Immunology and Serology Concepts, Exams of Nursing

Download Immunology and Serology Concepts and more Exams Nursing in PDF only on Docsity! Immunology & Serology - Questions + verified answers graded A+) **A patient has a T helper: T suppressor ratio of 1:2. What disease state might you expect? A. Infectious mononucleosis B. Rheumatoid arthritis C. AIDS D. Systemic lupus erythematosus - answer ✅✅**C. Due to reduced numbers of T cells in acquired immunodeficiency disease, there is a decrease in the T helper/T suppressor ratio. **A patient is immunized for rubella. What type of immunity does this patient have? A. Active B. Passive C. Adoptive D. Natural - answer ✅✅**A. Active immunity occurs after patient is presented with an antigen (infectious organism or immunization) and the patient produces antibodies. Option B is incorrect since passive immunity occurs when antibody is produced by another person or animal and the antibodies are transferred to the patient giving the patient temporary immunity. (The patient does not produce the antibodies.) Option C, adoptive immunity, occurs when immunocompetent cells are transferred to the patient. Option D, natural immunity, refers to the nonspecific mechanisms involved in fighting infection. It does not result in antibody formation. **A patient suspected of having syphilis had various tests performed with the following results: Rapid plasma regain (RPR) - reactive FTA-abs - nonreactive VDRL (CSF) - nonreactive These test results best reflect which of the following? A. neurosyphilis B. biologic false positive C. primary stage syphilis D. secondary stage syphilis - answer ✅✅**B. FTA-abs (fluorescent treponemal antibody absorption) is used to confirm positive screening tests (RPR, VDRL) for syphilis. Many diseases other than syphilis such as SLE, infectious mononucleosis, hepatitis, and malaria give false positive results for screening tests. Since the FTA-abs is negative, this is probably a biologic false positive. **A specimen is tested for antibodies to varicella resulting in a titer of 320. Two weeks later another specimen is drawn from the patient and the resulting titer is 640. A third test is done on a specimen drawn 4 weeks after the first specimen and the titer is 320. What is the disease state of the patient? the test is unnecessary. Option C is incorrect since mitotic cells are not seen in speckled patterns. Option D is incorrect because Crithidia substrate is used to confirm a homogeneous pattern. **Assess the disease state of the patient with the following results: HBsAg + HBeAg + anti-HBc + anti-HBe - anti-HBsAg - A. Incubation period for Hepatitis B B. Very early infection with Hepatitis B C. Highly infectious stage of Hepatitis B infection D. Immunity to Hepatitis B - answer ✅✅**C. When HBeAg is present, the patient is considered highly infectious. **Listed below are the results for a patient who had a positive ANA on initial testing. anti-Sm - anti-SSA + anti-SSB + anti-Scl-70 - anti-RANA - The disease most closely associated with these results is: A. SLE B. Mixed connective tissue disease C. Scleroderma D. Sjogren's syndrome - answer ✅✅**D. If an ANA pattern is speckled, follow up testing is performed to confirm the test and help determine the autoimmune disease present. Anti-SSA and anti-SSB are often positive in patients with Sjogren's syndrome. Patients with anti-Sm often have SLE. Anti-Scl-70 is associated with scleroderma and anti-RANA is associated with rheumatoid arthritis. **Multiple homogeneous, narrow bands are present in the gamma zone on electrophoresis of a patient's CSF on agarous gel. Immunofixation indicates that the bands are primarily IgG. This may indicate which of the following diseases: A. Addison's disease B. Myasthenia gravis C. Multiple sclerosis D. Multiple myeloma - answer ✅✅**C. In multiple sclerosis, IgG oligoclonal bands are often seen in CSF. Option A is incorrect because 40-70% of patients manifest antibodies against elements of the adrenal cortex and adrenal cell surfaces. Option B is incorrect since patients with myasthenia gravis demonstrate acetylcholine receptor blocking antibodies. (IgG, C3 and C9 can be demonstrated at the neuromuscular junctions). Option D is incorrect because multiple myeloma (plasma cell myeloma) is characterized by neoplastic proliferation of a single clone (monoclonal) of plasma cells that produce a specific type of immunoglobulin (usually IgG). **Multiple myeloma most commonly involves the following class of immunoglobulin: A. IgA B. IgD C. IgG D. IgM - answer ✅✅**C. Proliferation of a monoclonal antibody in multiple myeloma is usually of the IgG class. **The best method for screening cerebrospinal fluid for syphilis is: A. VDRL B. RPR C. FTA-abs D. Darkfield microscopy - answer ✅✅**A. VDRL is the test of choice for testing CSF. **The most sensitive assay for all stages of syphilis is: A. FTA-abs B. MTA-TP C. RPR D. VDRL - answer ✅✅**A. FTA-abs remains positive after treatment. Non-treponemal tests are not positive after patient is treated. **The tumor marker associated with cancer of the pancreas is: A. CEA B. CA 19-9 C. CA 125 antibodies are commonly implicated as a cause of biological false-positive nontreponemal tests for syphilis. Therefore, a treponemal test for syphilis should be performed to document this phenomenon in this case. *A 19-year-old girl came to her physician complaining of a sore throat and fatigue. Upon physical examination, lymphadenopathy was noted. Reactive lymphocytes were noted on the differential, but a rapid test for IM antibodies was negative. Liver enzymes were only slightly elevated. What test(s) should be ordered next? A. Hepatitis testing B. EBV serological panel C. HIV confirmatory testing D. Bone marrow biopsy - answer ✅✅*B. An EBV serological panel would give a more accurate assessment than a rapid slide IM test. The time of appearance of the various antibodies to the viral antigens differs according to the clinical course of the infection. *A biological false-positive reaction is least likely with which test for syphilis? A. VDRL B. Fluorescent T. pallidum antibody absorption test (FTA-ABS) C. RPR D. All are equally likely to detect a false-positive result - answer ✅✅*B. The FTA-ABS test is more specific for T. pallidum than nontreponemal tests such as the VDRL and RPR and would be least likely to detect a biological false-positive result. The FTA-ABS test uses heat-inactivated serum that has been absorbed with the Reiter strain of T. pallidum to remove nonspecific antibodies. Nontreponemal tests have a biological false-positive rate of 1%-10%, depending upon the patient population tested. False-positive findings are caused commonly by infectious mononucleosis (IM), SLE, viral hepatitis, and human immunodeficiency virus (HIV) infection. *A carbohydrate antigen 125 assay (CA-125) was performed on a woman with ovarian cancer. After treatment, the levels fell significantly. An examination performed later revealed the recurrence of the tumor, but the CA 125 levels remained low. How can this finding be explained? A. Test error B. CA-125 was the wrong laboratory test; α-fetoprotein (AFP) is a better test to monitor ovarian cancer C. CA-125 may not be sensitive enough when used alone to monitor tumor development D. CA-125 is not specific enough to detect only one type of tumor - answer ✅✅*C. CA-125 is a tumor associated carbohydrate antigen that is elevated in 70%-80% of patients with ovarian cancer and about 20% of patients with pancreatic cancer. While an increase in CA-125 may indicate recurrent or progressive disease, failure to do so does not necessarily indicate the absence of tumor growth. *A child suspected of having an inherited humoral immunodeficiency disease is given diphtheria/ tetanus vaccine. Two weeks after the immunization, his level of antibody to the specific antigens is measured. Which result is expected for this patient if he/she indeed has a humoral deficiency? A. Increased levels of specific antibody B. No change in the level of specific antibody *A hospital employee received the final dose of the hepatitis B vaccine 3 weeks ago. She wants to donate blood. Which of the following results are expected from the hepatitis screen, and will she be allowed to donate blood? A. HBsAg, positive; anti-HBc, negative—she may donate B. HBsAg, negative; anti-HBc, positive—she may not donate C. HBsAg, positive; anti-HBc, positive—she may not donate D. HBsAg, negative; anti-HBc, negative—she may donate - answer ✅✅*D. She may donate if she is symptom free. The response to hepatitis B vaccine would include a positive result for anti-HBs, a test not normally a part of routine donor testing. She will be negative for HBsAg and anti-HBc. *A laboratory is evaluating an enzyme-linked immunosorbent assay (ELISA) for detecting an antibody to cyclic citrullinated peptide (CCP), which is a marker for rheumatoid arthritis. The laboratory includes serum from healthy volunteers and patients with other connective tissue diseases in the evaluation. These specimens determine which factor of the assay? A. Sensitivity B. Precision C. Bias D. Specificity - answer ✅✅*D. Specificity is defined as a negative result in the absence of the disease. The non- rheumatoid arthritis specimens would be expected to test negative if the assay has high specificity. Precision is the ability of the assay to repeatedly yield the same results on a single specimen. Both bias and sensitivity calculations would include specimens from rheumatoid arthritis specimens. Although those specimens would be included in the evaluation, they are not listed in the question. *A newborn is to be tested for a vertically transmitted HIV infection. Which of the following tests is most useful? A. HIV PCR B. CD4 count C. Rapid HIV antibody test D. HIV IgM antibody test - answer ✅✅*A. Neonatal HIV diagnosis is performed by screening for the presence of the virus. The current antibody tests are either IgG-specific or an IgG/IgM combination assay. Thus an infant whose mother is HIV positive will also be positive in the HIV antibody assay. Although the CD4 count may be a useful assay to determine disease activity, there are many causes of reduced CD4 numbers and this assay should not be used to diagnose HIV infection. *A patient came to his physician complaining of a rash, severe headaches, stiff neck, and sleep problems. Laboratory tests of significance were an elevated sedimentation rate (ESR) and slightly increased liver enzymes. Further questioning of the patient revealed that he had returned from a hunting trip in upstate New York 4 weeks ago. His physician ordered a serological test for Lyme disease, and the assay was negative. What is the most likely explanation of these results? A. The antibody response is not sufficient to be detected at this stage B. The clinical symptoms and laboratory results are not characteristic of Lyme disease C. The patient likely has an early infection with hepatitis B virus D. Laboratory error has caused a false-negative result - answer ✅✅*A. The antibody response to B. burgdorferi may not develop until several weeks after initial infection. The antibody test should be followed by a test such as PCR to detect the DNA of the organism. Regardless of the test outcome, if the physician suspects Lyme disease, treatment should begin immediately. *A patient deficient in the C3 complement treatment efficacy or recurrence, the half-life of the protein must be considered when determining the testing interval. PSA has a half-life of almost 4 days and would not reach normal levels after surgery for approximately 3-4 weeks. The hook effect is the result of very high antigen levels giving a lower than expected result in a double antibody sandwich assay when both antibodies and sample are added at the same time. *A patient presents with clinical symptoms of celiac disease. Tests for anti-tissue transglutaminase and antigliadin antibodies are negative. Which of the following tests should be ordered? A. IgG level B. HLA DQ typing C. HLA DR typing D. IgM level - answer ✅✅*B. While antibodies to tissue transglutaminase and gliadin are often found in celiac disease, their combined sensitivity is less than 100%. Celiac disease is almost exclusively associated with the presence of HLA DQ2 and/or HLA DQ8. These HLA genes are not diagnostic of celiac disease, but provide a testing alternative in antibody-negative individuals who meet the clinical diagnostic criteria for celiac disease. *A patient received 2 units of RBCs following surgery. Two weeks after the surgery, the patient was seen by his physician and exhibited mild jaundice and slightly elevated liver enzymes. Hepatitis testing, however, was negative. What should be done next? A. Nothing until more severe or definitive clinical signs develop B. Repeat hepatitis testing immediately C. Repeat hepatitis testing in a few weeks D. Check blood bank donor records and contact donor(s) of transfused units - answer ✅✅*C. The level of HBsAg may not have reached detectable levels, and antibodies to HBc and HCV would not have yet developed. Waiting 1 or 2 weeks and repeating the tests may reveal evidence of hepatitis virus infection. *A patient received 5 units of fresh frozen plasma (FFP) and developed a severe anaphylactic reaction. He has a history of respiratory and gastrointestinal infections. Post-transfusion studies showed all 5 units to be ABO-compatible. What immunologic test would help to determine the cause of this transfusion reaction? A. Complement levels, particularly C3 and C4 B. Flow cytometry for T-cell counts C. Measurement of immunoglobulins D. NBT test for phagocytic function - answer ✅✅*C. The patient had an anaphylactic reaction to a plasma product. This, combined with the history of respiratory and gastrointestinal infections, suggests a selective IgA deficiency. Measurement of immunoglobulins would be helpful in this case. A low serum IgA and normal IgG substantiate the diagnosis of selective IgA deficiency. Such patients frequently produce anti-IgA, which is often responsible for a severe transfusion reaction when ABO-compatible plasma is administered. *A patient receives a transfusion of packed red cells and fresh frozen plasma and develops an anaphylactic, nonhemolytic reaction. She reports receiving a transfusion 20 years earlier. She had no reaction to the previous transfusion, but she did feel "poorly" a few weeks later. Which of the following transfused substances most likely elicited vitro coagulation tests: prothrombin time (PT), APTT, and dilute Russell's viper venom (DRVV) time. These tests require phospholipid for the activation of factor X. About 30% of patients with antibodies to cardiolipin or phospholipids have a biological falsepositive RPR result. Antismooth muscle is most commonly associated with chronic active hepatitis, and increased AST with necrotic liver diseases. Although ACA and LAC may be associated with SLE, the majority of patients with these antibodies do not have lupus and would have a normal C3 level. *A patient who is blood group O is accidentally transfused with group A blood and develops a reaction during the transfusion. What antibody is involved in this type II reaction? A. IgM B. IgE C. IgG and IgE D. IgG - answer ✅✅*A. IgG and IgM are the antibodies involved in a type II cytotoxic reaction. Naturally occurring anti-A in the form of IgM is present in the blood of a group O individual and would cause an immediate transfusion reaction. Cell destruction occurs when antibodies bind to cells causing destruction via complement activation, thereby triggering intravascular hemolysis. *A patient with joint swelling and pain tested negative for serum RF by both latex agglutination and ELISA methods. What other test would help establish a diagnosis of RA in this patient? A. Anti CCP B. ANA testing C. Flow cytometry D. Complement levels - answer ✅✅*A. Antibodies to cyclic citruillinated peptide are often found in RF-negative patients with rheumatoid arthritis. The absence of rheumatoid factors from serum does not rule out a diagnosis of RA, and more than half of patients who are diagnosed with RA present initially with a negative serum result. The serum RF test will eventually be positive in 80%-90% of patients who meet the clinical criteria for RA. *A patient with ovarian cancer who has been treated with chemotherapy is being monitored for recurrence using serum CA-125, CA-50, and CA 15-3. Six months after treatment the CA 15-3 is elevated, but the CA-125 and CA-50 remain low. What is the most likely explanation of these findings? A. Ovarian malignancy has recurred B. CA 15-3 is specific for breast cancer and indicates metastatic breast cancer C. Testing error occurred in the measurement of CA 15-3 caused by poor analytical specificity D. The CA 15-3 elevation is spurious and probably benign - answer ✅✅*A. Although CA-125 is the most commonly used tumor marker for ovarian cancer, not all ovarian tumors produce CA-125. Greatest sensitivity in monitoring for recurrence is achieved when several markers known to be increased in the malignant tissue type are measured simultaneously and when the markers are elevated (by malignancy) prior to treatment. In addition to limited sensitivity, no single tumor marker is entirely specific. Carbohydrate and other oncofetal antigens are produced by several malignant and benign conditions. Although testing errors may occur in any situation, measurements of carbohydrate antigens use purified monoclonal antibodies with very low cross reactivities. *A patient with symptoms associated with SLE and temperature was 37.7°C (100°F). Rubella tests for both IgG and IgM antibody were positive. What positive test(s) would reveal a diagnosis of congenital rubella syndrome in her baby after birth? A. Positive rubella tests for both IgG and IgM antibody B. Positive rubella test for IgM C. Positive rubella test for IgG D. No positive test is revealed in congenital rubella syndrome - answer ✅✅*B. A finding of IgG is not definitive for congenital rubella syndrome because IgG crosses the placenta from the mother; however, demonstration of IgM, even in a single neonatal sample, is diagnostic. *A renal transplant recipient is found to have a rising creatinine level and reduced urine output. The physician orders a "Urine PCR" assay. When you call to find out what organism the physician wants to identify, you are told: A. Hepatitis C virus B. Legionella pneumophila C. EBV D. BK virus - answer ✅✅*D. BK virus is a polyoma virus that can cause renal and urinary tract infections. The virus is an opportunistic pathogen and has become a well-recognized cause of poor renal function in kidney transplant recipients. Antibody testing is not practical or useful for this infection. The principal diagnostic assays are urinary cytology, and specific BK virus PCR testing in urine and serum. Although Legionella pneumophila can be diagnosed through a urinary antigen assay, that organism is not a primary cause of renal insufficiency in transplant patients. *A specimen appears to have a perinuclear staining pattern in an antineutrophil cytoplasmic antibody (ANCA) immunofluorescent assay using ethanolfixed neutrophils, suggesting the possibility of a pANCA. On which of the following substrates would this specimen display cytoplasmic speckling? A. Formalin-fixed neutrophils B. Unfixed neutrophils C. HEp-2 cells D. Rabbit kidney tissue - answer ✅✅*A. Antibodies to neutrophil cytoplasmic antigen demonstrating a perinuclear pattern of fluorescence indicate a diagnosis of vasculitis. However, atypical ANCAs and ANAs also demonstrate a perinuclear staining pattern on ethanol-fixed neutrophils. To differentiate these from pANCA, specimens appearing as a pANCA on ethanol-fixed cells are tested on formalin-fixed neutrophils. The myeloperoxidase containing granules that coalesce around the nuclear membrane during ethanol fixation will remain in the cytoplasm during formalin fixation. Thus, pANCA will have a cytoplasmic (cANCA) pattern on a formalin-fixed slide, but ANAs will retain a perinuclear pattern and the fluorescence will be diminished. *A streptozyme test was performed, but the result was negative, even though the patient showed clinical signs of a streptococcal throat infection. What should be done next? A. Either ASO or anti-deoxyribonuclease B (anti-DNase B) testing B. Another streptozyme test using diluted serum C. Antihyaluronidase testing D. Wait for 3-5 days and repeat the streptozyme during the past 12 weeks. Which of the following tests would you recommend to determine if the woman was infected during her pregnancy? A. Toxo PCR on amniotic fluid B. Toxo IgM on amniotic fluid C. Toxo IgG avidity D. Amniotic fluid culture - answer ✅✅*C. Although IgM is positive, in toxoplasmosis, specific IgM may remain detectable for a year or more following infection. IgG avidity, or the strength of binding of a serum to the antigen of interest, is a useful method to determine if an infection is recent or in the distant past. IgG avidity will increase with time following an infection. Amniotic fluid testing is not useful for determining when the mother might have been infected. *A woman who has had five pregnancies subsequently tests positive for HIV by Western blot. What is the most likely reason for this result? A. Possible cross-reaction with herpes or EBV antibodies B. Interference from medication C. Cross-reaction with HLA antigens in the antigen preparation D. Possible technical error - answer ✅✅*C. Multiparous women often have HLA antibodies. The Western blot antigens are derived from HIV grown in human cell lines having HLA antigens. A cross reaction with HLA antigen(s) in the Western blot could have occurred. *All of the following are functions of immunoglobulins except: A. Neutralizing toxic substances B. Facilitating phagocytosis through opsonization C. Interacting with TC cells to lyse viruses D. Combining with complement to destroy cellular antigens - answer ✅✅*C. Cytotoxic T cells lyse virally infected cells directly, without requirement for specific antibody. The TC cell is activated by viral antigen that is associated with MHC class I molecules on the surface of the infected cell. The activated TC cell secretes several toxins, such as tumor necrosis factor, which destroy the infected cell and virions. *All of the following are immunologic functions of complement except: A. Induction of an antiviral state B. Opsonization C. Chemotaxis D. Anaphylatoxin formation - answer ✅✅*A. Complement components are serum proteins that function in opsonization, chemotaxis, and anaphylatoxin formation but do not induce an antiviral state in target cells. This function is performed by interferons *All of the following hepatitis viruses are spread through blood or blood products except: A. Hepatitis A B. Hepatitis B C. Hepatitis C D. Hepatitis D - answer ✅✅*A. Hepatitis A is spread through the fecal-oral route and is the cause of infectious hepatitis. Hepatitis A virus has a shorter incubation period (2-7 weeks) than hepatitis B virus (1-6 months). Epidemics of hepatitis A virus can occur, especially when food and water become contaminated with raw sewage. Hepatitis E virus is also spread via the oral-fecal route and, like hepatitis A virus, has a short incubation period. *All of the following tests may be abnormal in a type III immune complex reaction except: A. C1q-binding assay by ELISA B. Raji cell assay C. CH50 level D. Mitogen response - answer ✅✅*D. Mitogen stimulation is used to measure T-cell, B-cell, and null-cell responsiveness, which is important in patients displaying anergy and other signs of immunodeficiency. The C1q assay and the Raji cell C. The sample was stored at 4°C prior to separating serum and cells D. Further serial dilution is necessary - answer ✅✅*D. Cold agglutinins may be measured in patients who have cold agglutinin disease, a cold autoimmune hemolytic anemia. In such cases, titers can be as high as 106. If all tubes (dilutions) for cold agglutinins are positive, except the negative control, then a high titer of cold agglutinins is present in the sample. Further serial dilutions should be performed. *An 18-month-old boy has recurrent sinopulmonary infections and septicemia. Bruton's X-linked immunodeficiency syndrome is suspected. Which test result would be markedly decreased? A. Serum IgG, IgA, and IgM B. Total T-cell count C. Both B- and T-cell counts D. Lymphocyte proliferation with phytohemagglutinin stimulation - answer ✅✅*A. A patient with Bruton's X-linked agammaglobulinemia presents with clinical symptoms related to recurrent infections, demonstrated in the laboratory by decreased or absent immunoglobulins. Peripheral blood B cells are absent or markedly reduced, but T cells are normal in number and function. Because phytohemagglutinin is a T-cell mitogen, the lymphocyte proliferation test using PHA would be normal for this patient. *An ANA test on HEp-2 cells shows nucleolar staining in interphase cells and dense chromatin staining in mitotic cells. The most likely cause of this staining pattern is: A. Antifibrillarin antibody B. Antiribosomal p antibody C. A serum with nucleolar and homogeneous patterns D. Technical artifact - answer ✅✅*A. Antifibrillarin antibody has this appearance. Ribosomal p antibody has nucleolar staining and a background homogeneous and cytoplasmic stain. A combination nucleolar/homogeneous specimen will also show homogeneous staining in the interphase cells. This pattern is not seen in typical technical artifacts. *An antinuclear antibody test is performed on a specimen from a 55-year-old woman who has unexplained joint pain. The IFA result is a titer of 40 and a homogeneous pattern. The appropriate follow-up for this patient is: A. Anti-DNA assay B. Extractable nuclear antigen (ENA) testing C. Retest ANA in 3-6 months D. CH50 complement assay - answer ✅✅*C. Approximately 25% of women in this age range may have low titer-positive ANA assays with no demonstrable connective tissue disease. A patient with anti-DNA-positive SLE would be expected to have a much higher titer (> 160) in an IFA assay. A similar titer would be expected for an ENA positive specimen, although the pattern would be speckled. Complement testing would not be indicated with this low titer in a 55-year-old female. *An IFE performed on a serum sample showed a narrow dark band in the lanes containing anti-γ and anti-λ. How should this result be interpreted? A. Abnormally decreased IgG concentration B. Abnormal test result demonstrating monoclonal IgGλ C. Normal test result D. Impossible to determine without densitometric quantitation - answer ✅✅*B. A narrow dark band formed in both the lane containing anti-γ and anti-λ indicates the presence of a monoclonal IgG λ immunoglobulin. A diffuse dark band would indicate a polyclonal increase in IgG that often accompanies the patient should be retested in 4 weeks - answer ✅✅*C. A negative IgM assay rarely rules out an infection. While a convalescent specimen may be useful in many cases, in an immunosuppressed patient the convalescent specimen may remain negative in the presence of an infection. Thus a parvovirus PCR test is the preferred choice in this case. A false-negative result could conceivably be caused by multiple whole blood or plasma transfusions, but retesting for antibody a month later would not be beneficial to the patient. *An initial and repeat ELISA test for antibodies to HIV-1 are both positive. A Western blot shows a single band at gp160. The patient shows no clinical signs of HIV infection, and the patient's CD4 T-cell count is normal. Based upon these results, which conclusion is correct? A. Patient is diagnosed as HIV-1-positive B. Patient is diagnosed as HIV-2-positive C. Results are inconclusive D. Patient is diagnosed as HIV-1-negative - answer ✅✅*C. The Western blot test is used as a confirmatory test for HIV, but it is not as sensitive as enzyme immunoassay tests using polyvalent HIV antigens derived from cloned HIV genes. The Western blot test is considered positive only if antibodies to at least two of three viral antigens—p24, gp41, and gp160/120—are detected. The presence of a single band is indeterminate. Over the course of the next 3 months, two or more antibodies will be detected if the patient is HIV positive; however, antibodies to a single viral protein may be caused by a cross reaction, and this patient may fail to seroconvert. This result should be reported as indeterminate, and the patient should be retested in 3 months. Alternatively, a more sensitive confirmatory test such as PCR or immunofluorescence may be performed. *Antibodies to thyroid peroxidase can be detected by using agglutination assays. Which of the following diseases may show positive results with this type of assay? A. Graves' disease and Hashimoto's thyroiditis B. Myasthenia gravis C. Granulomatous thyroid disease D. Addison's disease - answer ✅✅*A. Antibodies to thyroid peroxidase may be detected in both Graves' disease (hyperthyroidism) and Hashimoto's thyroiditis (hypothyroidism). If a positive result is found to thyroid peroxidase, thyroxine levels can be measured to distinguish between the two diseases. *Blood products are tested for which virus before being transfused to newborns? A. EBV B. Human T-lymphotropic virus II (HTLV-II) C. Cytomegalovirus (CMV) D. Hepatitis D virus - answer ✅✅*C. CMV can be life threatening if transmitted to a newborn through a blood product. HTLV-II is a rare virus, which like HIV, is a T-cell tropic RNA retrovirus. The virus has been associated with hairy cell leukemia, but this is not a consistent finding. *Free monoclonal light chains are often present in the serum of multiple myeloma patients, and may be useful for disease monitoring. Which of the following assays would be recommended to detect the presence of serum-free light chains? A. Serum protein electrophoresis B. Urine immunofixation C. Nephelometry *Given a heterophile antibody titer of 224, which of the following results indicate IM? A. Pig: Two-tube titer reduction, Beef: Five-tube titer reduction B. Pig: No titer reduction, Beef: No titer reduction C. Pig: Five-tube titer reduction, Beef: Five-tube titer reduction D. Pig: Five-tube titer reduction, Beef: No titer reduction - answer ✅✅*A. Antibodies to infectious mononucleosis (non- Forssman antibodies) are not neutralized or absorbed by guinea pig antigen (but are absorbed by beef cell antigen). A positive test is indicated by at least a four-tube reduction in the heterophile titer after absorption with beef cells and no more than a three-tube reduction in titer after absorption with guinea pig kidney. *How are cytotoxic T cells (TC cells) and natural killer (NK) cells similar? A. Require antibody to be present B. Effective against virally infected cells C. Recognize antigen in association with HLA class II markers D. Do not bind to infected cells - answer ✅✅*B. Both TC and NK cells are effective against virally infected cells, and neither requires antibody to be present to bind to infected cells. NK cells do not exhibit MHC class restriction, whereas activation of TC cells requires the presence of MHC class I molecules in association with the viral antigen. *How can interfering cold agglutinins be removed from a test sample? A. Centrifuge the serum and remove the top layer B. Incubate the clot at 1°C-4°C for several hours, then remove serum C. Incubate the serum at 56°C in a water bath for 30 minutes D. Use an anticoagulated sample - answer ✅✅*B. Cold agglutinins will attach to autologous red cells if incubated at 1°C-4°C. The absorbed serum will be free of cold agglutinins. *How is complement activity destroyed in vitro? A. Heating serum at 56°C for 30 min B. Keeping serum at room temperature of 22°C for 1 hour C. Heating serum at 37°C for 45 min D. Freezing serum at 0°C for 24 hours - answer ✅✅*A. Complement activity in serum in vitro is destroyed by heating the serum at 56°C for 30 min. In test procedures where complement may interfere with the test system, it may be necessary to destroy complement activity in the test sample by heat inactivation. *How is HLA typing used in the investigation of genetic diseases? A. For prediction of the severity of the disease B. For genetic linkage studies C. For direct diagnosis of disease D. Is not useful in this situation - answer ✅✅*B. HLA typing is useful in predicting some genetic diseases and for genetic counseling because certain HLA types show strong linkage to some diseases. HLA typing is not specifically used to diagnose a disease or assess its severity. In linkage studies, a disease gene can be predicted because it is located next to the locus of a normal gene with which it segregates. For example, the relative risk of developing ankylosing spondylitis is 87% in persons who are positive for HLA-B27. Analysis of family pedigrees for the linkage marker and disease can be used to determine the probability that a family member will inherit the disease gene. *If only anti-HBs is positive, which of the following can be ruled out? A. Hepatitis B virus vaccination B. Distant past infection with hepatitis B virus C. Hepatitis B immune globulin (HBIG) injection D. Chronic hepatitis B virus infection - answer ✅✅*D. Persons with chronic HBV infection show a positive test result for anti-HBc (IgG or total) and HBsAg but not anti-HBs. Patients with active chronic hepatitis acute phase reactants, and fibrinolytic factors enter the site of inflammation. Antibody and lymphocytes do not enter until later. *Interpret the following ASO results: Tube Nos. 1-4 (Todd unit 125): no hemolysis; Tube No. 5 (Todd unit 166): hemolysis A. Positive Todd unit 125 B. Positive Todd unit 166 C. No antistreptolysin O present D. Impossible to interpret - answer ✅✅*A. An ASO titer is expressed in Todd units as the last tube that neutralizes (no visible hemolysis) the streptolysin O (SLO). Most laboratories consider an ASO titer significant if it is 166 Todd units or higher. However, people with a recent history of streptococcal infection may demonstrate an ASO titer of 166 or higher; demonstration of a rise in titer from acute to convalescent serum is required to confirm a current streptococcal infection. ASO is commonly measured using a rapid latex agglutination assay. These tests show agglutination when the ASO concentration is 200 IU/mL or higher. *Interpret the following description of an immunofixation electrophoresis assay of urine. Dense wide bands in both the κ and λ lanes. No bands present in the heavy-chain lanes. A. Normal B. Light chain disease C. Increased polyclonal Fab fragments D. Multiple myeloma - answer ✅✅*C. Heavy wide bands seen with both anti-κ and anti-λ antisera indicate excessive light-chain excretion. Light-chain disease would show a heavy restricted band for one of the light-chain reactions, but not both. The finding of excess λ and κ chains indicates a polyclonal gammopathy with increased immunoglobulin turnover and excretion of the light chains as Fab fragments. *Interpret the following microcytotoxicity results: A9 and B12 cells damaged; A1 and Aw19 cells intact. A. Positive for A1 and Aw19; negative for A9 and B12 B. Negative for A1 and Aw19; positive for A9 and B12 C. Error in test system; retest D. Impossible to determine - answer ✅✅*B. The microcytotoxicity test is based upon the reaction of specific antisera and HLA antigens on test cells. Cells damaged by the binding of antibody and complement are detected with a supravital dye such as eosin. *Interpret the following quantitative RPR test results. RPR titer: weakly reactive 1:8; reactive 1:8-1:64 A. Excess antibody, prozone effect B. Excess antigen, postzone effect C. Equivalence of antigen and antibody D. Impossible to interpret; testing error - answer ✅✅*A. This patient may be in the secondary stage of syphilis and is producing large amounts of antibody to T. pallidum sufficient to cause antibody excess in the test. The test became strongly reactive only after the antibody was diluted. *Interpret the following results for EBV infection: IgG and IgM antibodies to viral capsid antigen (VCA) are positive. A. Infection in the past B. Infection with a mutual enhancer virus such as HIV C. Current infection Dakota from a 58-year-old patient shows a band at the β-γ junction. The specimen was also positive for rheumatoid factor. You recommend that an immunofixation test be performed to determine if the band represents a monoclonal immunoglobulin. Another specimen is obtained 2 weeks later by the physician in his office 30 miles away, and the whole blood is submitted to you for the IFE. The courier placed the whole blood specimen in an ice chest for transport. In this specimen, no β-γ band is seen in the serum protein lane, and the IgM lane is very faint. The rheumatoid factor on this specimen was negative. The physician wants to know what's wrong with your laboratory. Your response is: A. Nothing's wrong with our laboratory; the patient had an infection 2 weeks ago that has cleared up B. Something's wrong with our laboratory—we - answer ✅✅*D. The most likely cause of the discrepant results is the presence of a type II cryoglobulin. This is a monoclonal rheumatoid factor. The protein likely precipitated during the courier ride and was thus in the clot when the laboratory separated the serum. *Rapid assays for influenza that utilize specimens obtained from nasopharyngeal swabs detect: A. IgM anti-influenza B. IgA anti-influenza C. IgA-influenza Ag immune complexes D. Influenza antigen - answer ✅✅*D. The rapid influenza assays are antigen detection methods. They are designed to detect early infection, before antibody is produced. *Select the best donor for a man, blood type AB, in need of a kidney transplant. A. His brother, type AB, HLA matched for class II antigens B. His mother, type B, HLA matched for class I antigens C. His cousin, type O, HLA matched for major class II antigens D. Cadaver donor, type O, HLA matched for some class I and II antigens - answer ✅✅*A. A twin or sibling donor of the same blood type and HLA matched for class II antigens is the best donor in this situation. Class II antigens (HLA-D, HLA-DR, DQ, and DP) determine the ability of the transplant recipient to recognize the graft. The HLA genes are located close together on chromosome 6, and crossover between HLA genes is rare. Siblings with closely matched class II antigens most likely inherited the same class I genes. The probability of siblings inheriting the same HLA haplotypes from both parents is 1:4. *Serological tests for which disease may give a falsepositive result if the patient has Lyme disease? A. AIDS B. Syphilis C. Cold agglutinins D. Hepatitis C - answer ✅✅*B Lyme disease is caused by a spirochete and may give positive results with some specific treponemal antibody tests for syphilis. *SITUATION: A 54-year-old man was admitted to the hospital after having a seizure. Many laboratory tests were performed, including an RPR, but none of the results were positive. The physician suspects a case of late (tertiary) syphilis. Which test should be performed next? A. Repeat RPR, then perform VDRL B. Treponemal test such as MHA-TP on serum antigens in a complement-dependent cytotoxicity assay. What is the most likely cause? A. Too much supravital dye was added B. Rabbit complement is inactivated C. All leukocytes are dead D. Antisera is too concentrated - answer ✅✅*B. Inactive rabbit complement may not become fixed to antibodies that have bound test leukocytes; therefore, no lysis of cells will occur. When the supravital dye is added, all cells will appear negative (exclude the dye) for all HLAs. *T cells travel from the bone marrow to the thymus for maturation. What is the correct order of the maturation sequence for T cells in the thymus? A. Bone marrow to the cortex; after thymic education, released back to peripheral circulation B. Maturation and selection occur in the cortex; migration to the medulla; release of mature T cells to secondary lymphoid organs C. Storage in either the cortex or medulla; release of T cells into the peripheral circulation D. Activation and selection occur in the medulla; mature T cells are stored in the cortex until activated by antigen - answer ✅✅*B. Immature T cells travel from the bone marrow to the thymus to mature into functional T cells. Once in the thymus, T cells undergo a selection and maturation sequence that begins in the cortex and moves to the medulla of the thymus. Thymic factors such as thymosin and thymopoietin and cells within the thymus such as macrophages and dendritic cells assist in this sequence. After completion of the maturation cycle, T cells are released to secondary lymphoid organs to await antigen recognition and activation. *T regulator cells, responsible for controlling autoimmune antibody production, express which of the following phenotypes? A. CD3, CD4, CD8 B. CD3, CD8, CD25 C. CD3, CD4, CD25 D. CD8, CD25, CD56 - answer ✅✅*C. T regulator cells are believed to be the primary immune suppressor cells and express CD3, CD4, and CD25. CD25 is the interleukin 2 receptor. CD25 may be expressed by activated T cells, but is constitutively expressed by the T-regulator cells. CD25 expression on T-regulator cells occurs in the thymus and is regulated by the FOXP3 protein. *Tests to identify infection with HIV fall into which three general classification types of tests? A. Tissue culture, antigen, and antibody tests B. Tests for antigens, antibodies, and nucleic acid C. DNA probe, DNA amplification, and Western blot tests D. ELISA, Western blot, and Southern blot tests - answer ✅✅*B. Two common methods for detecting antibodies to HIV are the ELISA and Western blot tests. Two common methods for detecting HIV antigens are ELISA and immunofluorescence. Two common methods for detecting HIV genes are the Southern blot test and DNA amplification using the polymerase chain reaction to detect viral nucleic acid in infected lymphocytes. *The absorbance of a sample measured by ELISA is greater than the highest standard. What corrective action should be taken? A. Extrapolate an estimated value from the highest reading B. Repeat the test using a standard of higher concentration C. Repeat the assay using one half the volume of the sample D. Dilute the test sample - answer ✅✅*D. Usually when a test sample reads at a value above the highest standard in an ELISA test, it is diluted and measured again. In those instances where no additional clinical value can be obtained by dilution, the result may be reported as greater than the highest standard (citing the upper reportable limit of the assay). *The detection of precipitation reactions depends on the presence of optimal proportions of antigen and antibody. A patient's sample contains a large amount of antibody, but the reaction in a test system containing antigen is negative. What has happened? A. Performance error B. Low specificity C. A shift in the zone of equivalence D. Prozone phenomenon - answer ✅✅*D. Although performance error and low specificity should be considered, if a test system fails to yield the expected reaction, excessive antibody preventing a precipitation reaction is usually the cause. Prozone occurs when antibody molecules saturate the antigen patients with scleroderma. Anti-RNA and anti-Sm are not usually found in patients with mixed connective tissue disease. This is a syndrome involving aspects of SLE, RA, scleroderma, and polymyositis. The immunofluorescence pattern most often seen in MCTD is the speckled pattern caused by anti-RNP. *What comprises the indicator system in an indirect ELISA for detecting antibody? A. Enzyme-conjugated antibody + chromogenic substrate B. Enzyme conjugated antigen + chromogenic substrate C. Enzyme + antigen D. Substrate + antigen - answer ✅✅*A. The ELISA test measures antibody using immobilized reagent antigen. The antigen is fixed to the walls of a tube or bottom of a microtiter well. Serum is added (and incubated) and the antibody binds, if present. After washing, the antigen-antibody complexes are detected by adding an enzyme labeled anti-immunoglobulin. The unbound enzyme label is removed by washing, and the bound enzyme label is detected by adding chromogenic substrate. The enzyme catalyzes the conversion of substrate to colored product. *What constitutes a diagnosis of viral hepatitis? A. Abnormal test results for liver enzymes B. Clinical signs and symptoms C. Positive results for hepatitis markers D. All of these options - answer ✅✅*D. To diagnose a case of hepatitis, the physician must consider clinical signs as well as laboratory tests that measure liver enzymes and hepatitis markers. *What corrective action should be taken when an indeterminate pattern occurs in an indirect IFA? A. Repeat the test using a larger volume of sample B. Call the physician C. Have another medical laboratory scientist read the slide D. Dilute the sample and retest - answer ✅✅*D. An unexpected pattern may indicate the presence of more than one antibody. Diluting the sample may help to clearly show the antibody specificities, if they are found in different titers. If the pattern is still atypical, a new sample should be collected and the test repeated. *What criteria constitute the classification system for HIV infection? A. CD4-positive T-cell count and clinical symptoms B. Clinical symptoms, condition, duration, and number of positive bands on Western blot C. Presence or absence of lymphadenopathy D. Positive bands on Western blot and CD8-positive T-cell count - answer ✅✅*A. The classification system for HIV infection is based upon a combination of CD4-positive T-cell count (helper T cells) and various categories of clinical symptoms. Classification is important in determining treatment options and the progression of the disease. *What disease is indicated by a high titer of anti-Sm (anti-Smith) antibody? A. Mixed connective tissue disease (MCTD) B. RA C. SLE D. Scleroderma - answer ✅✅*C. High titer anti-Sm is indicative of SLE. Anti-Sm is one of two antibodies against saline extractable nuclear antigens, the other being anti-RNP. These antibodies cause a speckled pattern of immunofluorescence. *What effect does selecting the wrong gate have on the results when cells are counted by flow cytometry? A. No effect C. A normal serum level rules out malignant prostatic disease D. The percentage of free PSA is elevated in persons with malignant disease - answer ✅✅*A. PSA is a glycoprotein with protease activity that is specific for the prostate gland. High levels may be caused by prostate malignancy, benign prostatic hypertrophy, or prostatitis, but PSA is not increased by physical examination of the prostate. PSA has a sensitivity of 80% and a specificity of about 75% for prostate cancer. The sensitivity is sufficiently high to warrant its use as a screening test, but sensitivity for stage A cancer is below 60%. Most of the serum PSA is bound to protease inhibitors such as α1-antitrypsin and α1-antichymotrypsin. Patients with borderline PSA levels (4-10 ng/mL) and a low percentage of free PSA are more likely to have cancer of the prostate than patients with a normal percentage of free PSA. *What is measured in the CH50 assay? A. RBC quantity needed to agglutinate 50% of antibody B. Complement needed to lyse 50% of RBCs C. Complement needed to lyse 50% of antibodysensitized RBCs D. Antibody and complement needed to sensitize 50% of RBCs - answer ✅✅*C. The CH50 is the amount of complement needed to lyse 50% of standardized hemolysin-sensitized sheep RBCs. It is expressed as the reciprocal of the serum dilution resulting in 50% hemolysis. Low levels are associated with deficiency of some complement components and active systemic autoimmune diseases in which complement is being consumed. *What is the "M" component in monoclonal gammopathies? A. IgM produced in excess B. μ Heavy chain produced in excess C. Malignant proliferation of B cells D. Monoclonal antibody or cell line - answer ✅✅*D. The "M" component refers to any monoclonal protein or cell line produced in a monoclonal gammopathy such as multiple myeloma. *What is the advantage of 4th-generation rapid HIV tests over earlier rapid HIV tests? A. They use recombinant antigens B. They detect multiple strains of HIV C. They detect p24 antigen D. They are quantitative - answer ✅✅*C. Both 3rd-generation and 4th-generation rapid tests for HIV use recombinant and synthetic HIV antigens conjugated to a solid phase. The multivalent nature of these tests allows for detection of less common subgroups of HIV-1 and simultaneous detection of both HIV-1 and HIV-2. However, the 4th-generation assays also use solid-phase antibodies to p24 antigen to detect its presence. Because p24 antigen appears before antibodies to HIV, 4th-generation tests can detect infection 4-7 days earlier than tests based on antibody detection alone. *What is the correct procedure upon receipt of a test request for human chorionic gonadotropin (hCG) on the serum from a 60-year-old man? A. Return the request; hCG is not performed on men B. Perform a qualitative hCG test to see if hCG is present C. Perform the test; hCG may be increased in testicular tumors D. Perform the test but use different standards and controls - answer ✅✅*C. hCG is normally tested for in pregnancy; it is diverse D. Anti-idiotype antibodies cannot be developed - answer ✅✅*C. Vaccine development has been difficult primarily because of the genetic diversity among different strains of the virus, and new strains are constantly emerging. HIV-1 can be divided into two main subtypes designated M (for main) and O (for outlier). The M group is further divided into 9 subgroups, designated A-J (there is no E subgroup), based upon differences in the nucleotide sequence of the gag gene. Two remaining subtypes are designed N (non M and non O) and P (a subtype related to SIVgor). A vaccine has yet to be developed that is effective for all of the subgroups of HIV-1. *What is the main use of laboratory tests to detect antibodies to islet cells and insulin in cases of insulin-dependent diabetes mellitus (IDDM)? A. To regulate levels of injected insulin B. To diagnose IDDM C. To rule out the presence of other autoimmune diseases D. To screen susceptible individuals prior to destruction of β cells - answer ✅✅*D. Fasting hyperglycemia is the primary finding used to diagnose IDDM. For individuals with an inherited susceptibility to the development of IDDM, laboratory tests for the detection of antibodies to islet cells and insulin may help to initiate early treatment before complete destruction of β cells. *What is the most likely cause when a Western blot or ELISA is positive for all controls and samples? A. Improper pipetting B. Improper washing C. Improper addition of sample D. Improper reading - answer ✅✅*B. Improper washing may not remove unbound enzyme conjugated anti-human globulin, and every sample may appear positive. *What is the most likely explanation when a patient has clinical signs of viral hepatitis but tests negative for hepatitis A IgM, hepatitis B surface antigen, and hepatitis C Ab? A. Tests were performed improperly B. The patient does not have hepatitis C. The patient may be in the "core window" D. Clinical evaluation was performed improperly - answer ✅✅*C. The patient may be in the "core window," the period of hepatitis B infection when both the surface antigen and surface antibody are undetectable. The IgM anti-hepatitis B core and the anti-hepatitis B core total antibody assays would be the only detectable markers in the serum of a patient in the core window phase of hepatitis B infection. *What is the most likely explanation when antibody tests for HIV are negative but a polymerase chain reaction test performed 1 week later is positive? A. Probably not HIV infection B. Patient is in the "window phase" before antibody production C. Tests were performed incorrectly D. Clinical signs may be misinterpreted - answer ✅✅*B. In early seroconversion, patients may not be making enough antibodies to be detected by antibody tests. The period between infection with HIV and the appearance of detectable antibodies is called the window phase. Although this period has been reduced to a few weeks by sensitive enzyme immunoassays, patients at high risk or displaying clinical conditions associated with HIV disease should be tested again after waiting several more weeks. *What method may be used for tissue typing instead of serological HLA typing? A. PCR B. Southern blotting C. RFLP D. All of these options - answer ✅✅*D. PCR, Southern blotting, and testing for RFLPs may all be used to identify HLA genes. Many laboratories use PCR technology for the routine determination of HLA type. *What molecule on the surface of most T cells recognizes antigen? A. IgT, a four-chain molecule that includes the tau heavy chain B. MHC protein, a two-chain molecule encoded by the HLA region C. CD3, consisting of six different chains D. TcR, consisting of two chains, alpha and beta - answer ✅✅*D. T cells have a membrane bound receptor (T-cell receptor or TcR) that is antigen specific. This twochain molecule consists of a single α-chain, similar to an immunoglobulin light chain, and a single β-chain, similar to an immunoglobulin heavy chain. Some T cells may express a γ-δreceptor instead of the α-βmolecule. There is no τheavy chain. MHC and CD3 molecules are present on T cells, but they are not the molecules that give antigen specificity to the cell *What outcome results from improper washing of a tube or well after adding the enzyme-antibody conjugate in an ELISA system? A. Result will be falsely decreased B. Result will be falsely increased C. Result will be unaffected D. Result is impossible to determine - answer ✅✅*B. If unbound enzyme-conjugated anti-immunoglobulin is not washed away, it will catalyze conversion of substrate to colored product, yielding a falsely elevated result. *What screening test should be performed first in a young patient suspected of having an immune dysfunction disorder? A. Complete blood count (CBC) and white cell differential B. Chemotaxis assay C. Complement levels D. Bone marrow biopsy - answer ✅✅*A. The first screening tests performed in the initial evaluation of a young patient who is suspected of having an immune dysfunction are the CBC and differential. White blood cells that are decreased in number or abnormal in appearance may indicate further testing. *What substance is detected by the rapid plasma reagin (RPR) and Venereal Disease Research Laboratory (VDRL) tests for syphilis? A. Cardiolipin B. Anticardiolipin antibody C. Anti-T. pallidum antibody D. Treponema pallidum - answer ✅✅*B. Reagin is the name for a nontreponemal antibody that appears in the serum of syphilis-infected persons and is detected by the RPR and VDRL assays. Reagin reacts with cardiolipin, a lipid-rich extract of beef heart and other animal tissues. *What type of antibodies is represented by the solid or homogeneous pattern in the immunofluorescence test for antinuclear antibodies? A. Antihistone antibodies B. Anticentromere antibodies C. Anti-ENA (anti-Sm and anti-RNP) antibodies D. Anti-RNA antibodies - answer ✅✅*A. Antihistone antibodies (and also anti-DNA antibodies) cause the solid or homogeneous pattern, which is commonly found in patients with SLE, RA, mixed connective tissue disease, and Sjögren's syndrome. Antibodies to the centromere of chromosomes is a marker for the CREST (calcinosis, Raynaud's phenomenon, esophageal dysfunction, sclerodactyly, procedure, the enzyme will continue to act on the substrate, producing a falsely elevated test result. *Which antibody persists in low-level carriers of hepatitis B virus? A. IgM anti-HBc B. IgG anti-HBc C. IgM anti-HBe D. IgG anti-HBs - answer ✅✅*B. IgG antibodies to the hepatitis B core antigen (anti-HBc) can be detected in carriers who are HBsAg and anti-HBs negative. These persons are presumed infective even though the level of HBsAg is too low to detect. No specific B core IgG test is available, however. This patient would be positive in the anti-B core total antibody assay and negative in the anti-HB core IgM test. *Which CD4:CD8 ratio is most likely in a patient with acquired immunodeficiency syndrome (AIDS)? A. 2:1 B. 3:1 C. 2:3 D. 1:2 - answer ✅✅*D. An inverted CD4:CD8 ratio (less than 1.0) is a common finding in an AIDS patient. The Centers for Disease Control and Prevention requires a CD4-positive (helper T) cell count of less than 200/μL or 14% in the absence of an AIDS-defining illness (e.g., Pneumocystis carinii pneumonia) in the case surveillance definition of AIDS. *Which cluster of differentiation (CD) marker appears during the first stage of T-cell development and remains present as an identifying marker for T cells? A. CD1 B. CD2 C. CD3 D. CD4 or CD8 - answer ✅✅*B. The CD2 marker appears during the first stage of T-cell development and can be used to differentiate T cells from other lymphocytes. This T- lymphocyte receptor binds sheep red blood cells (RBCs). This peculiar characteristic was the basis for the classic E rosette test once used to enumerate T cells in peripheral blood. CD2 is not specific for T cells, however, and is also found on large granular lymphocytes (LGL or natural killer [NK] cells). *Which complement component is found in both the classic and alternative pathways? A. C1 B. C4 C. Factor D D. C3 - answer ✅✅*D. C3 is found in both the classic and alternative (alternate) pathways of the complement system. In the classic pathway, C3b forms a complex on the cell with C4b2a that enzymatically cleaves C5. In the alternative pathway, C3b binds to an activator on the cell surface. It forms a complex with factor B called C3bBb which, like C4b2a3b, can split C5. *Which control shows the correct result for a valid ASO test? A. SLO control, no hemolysis B. Red cell control, no hemolysis C. Positive control, hemolysis in all tubes D. Hemolysis in both SLO and red cell control - answer ✅✅*B. The red cell control contains no SLO and should show no hemolysis. The SLO control contains no serum and should show complete hemolysis. An ASO titer cannot be determined unless both the RBC and SLO controls demonstrate the expected results. *Which disease is least likely when a nucleolar pattern occurs in an immunofluorescence test for antinuclear antibodies? A. MCTD B. Sjögren's syndrome C. SLE D. Scleroderma - answer ✅✅*A.* All of the diseases except MCTD may cause a infection. *Which hepatitis B marker is the best indicator of early acute infection? A. HBsAg B. HBeAg C. Anti-HBc D. Anti-HBs - answer ✅✅*A. Hepatitis B surface antigen (HBsAg) is the first marker to appear in hepatitis B virus infection. It is usually detected within 4 weeks of exposure (prior to the rise in transaminases) and persists for about 3 months after serum enzyme levels return to normal. *Which hepatitis B markers should be performed on blood products? A. HBsAg and anti-HBc B. Anti-HBs and anti-HBc C. HBeAg and HBcAg D. Anti-HBs and HBeAg - answer ✅✅ *Which hepatitis B markers should be performed on blood products? A. HBsAg and anti-HBc B. Anti-HBs and anti-HBc C. HBeAg and HBcAg D. Anti-HBs and HBeAg - answer ✅✅*A. Blood products are tested for HBsAg, an early indicator of infection, and anti-HBc, a marker that may persist for life. Following recovery from HBV infection, some patients demonstrate negative serology for HBsAg and anti-HBs but are positive for anti-HBc. Such patients are considered infective. *Which immunofluorescence pattern indicates the need for ENA testing by Ouchterlony immunodiffusion, Multiplex, or ELISA assays? A. Homogeneous or solid B. Peripheral or rim C. Speckled D. Nucleolar - answer ✅✅*C. A speckled pattern is often due to the presence of antibodies against the extractable nuclear antigens, such as Sm, RNP, SSA, and SSB. Homogenous and rim patterns suggest antibodies to double-stranded DNA. The homogeneous pattern may also be seen with antibodies to deoxyribonuclear protein, which is not an ENA. Nucleolar patterns often indicate antibodies to RNA or fibrillarin. *Which immunoglobulin appears first in the primary immune response? A. IgG B. IgM C. IgA D. IgE - answer ✅✅*B. The first antibody to appear in the primary immune response to an antigen is IgM. The titer of antiviral IgM (e.g., IgM antibody to cytomegalovirus [anti-CMV]) is more specific for acute or active viral infection than IgG and may be measured to help differentiate active from prior infection. *Which immunoglobulin appears in highest titer in the secondary response? A. IgG B. IgM C. IgA D. IgE - answer ✅✅*A. A high titer of IgG characterizes the secondary immune response. Consequently, IgG antibodies comprise about 80% of the total immunoglobulin concentration in normal serum. *Which immunoglobulin can cross the placenta? A. IgG B. IgM C. IgA