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Associateination Exam
Question 1. Which type of leukocyte is primarily responsible for phagocytosing bacteria during an acute infection? A) Basophil B) Neutrophil C) Eosinophil D) T cell Answer: B Explanation: Neutrophils are the most abundant white blood cells and are key players in the innate immune response, especially in the phagocytosis of bacteria during acute infections. Question 2. Which cell acts as a professional antigen-presenting cell (APC) and is most efficient in activating naïve T cells?
Associateination Exam
A) Neutrophil B) Macrophage C) Dendritic cell D) NK cell Answer: C Explanation: Dendritic cells are the most potent APCs, crucial for activating naïve T cells by presenting processed antigen via MHC molecules. Question 3. Which immunoglobulin is produced first during a primary immune response? A) IgG B) IgA
Associateination Exam
Explanation: Adaptive immunity is specific and has memory but is slower to respond initially compared to innate immunity, which is immediate. Question 5. The complement system is primarily involved in which of the following immune functions? A) Phagocytosis B) Antigen presentation C) Opsonization and cell lysis D) Antibody production Answer: C Explanation: Complement proteins enhance phagocytosis (opsonization) and can lyse cells directly via membrane attack complex formation.
Associateination Exam
Question 6. Which cytokine is known as the “T cell growth factor”? A) IL- 2 B) IL- 4 C) IFN-gamma D) TNF-alpha Answer: A Explanation: IL-2 is produced by activated T cells and is essential for the proliferation and differentiation of T cells. Question 7. Which chromosome houses the genes encoding the Major Histocompatibility Complex (MHC) in humans? A) Chromosome 1
Associateination Exam
Answer: D Explanation: HLA-DR is part of the class II MHC molecules, whereas A, B, and C are class I. Question 9. Which of the following best describes the function of MHC class I molecules? A) Present endogenous peptides to CD8+ T cells B) Present exogenous peptides to CD4+ T cells C) Activate B cells D) Activate NK cells Answer: A Explanation: MHC class I molecules present peptides derived from proteins synthesized inside the cell to cytotoxic CD8+ T cells.
Associateination Exam
Question 10. The process of “antigen processing” for MHC class II involves which cellular compartment? A) Cytosol B) Golgi apparatus C) Endosome/lysosome D) Nucleus Answer: C Explanation: MHC class II molecules bind peptides derived from extracellular proteins processed in endosomal/lysosomal compartments.
Associateination Exam
B) HLA-B
C) HLA-DR
D) HLA-DQ
Answer: B Explanation: HLA-B27 is strongly associated with increased risk for ankylosing spondylitis. Question 13. Which type of hypersensitivity reaction is mediated by IgE antibodies? A) Type I B) Type II C) Type III D) Type IV
Associateination Exam
Answer: A Explanation: Type I hypersensitivity (immediate) is mediated by IgE and is responsible for allergies and anaphylaxis. Question 14. Which of the following best defines a “haplotype” in the context of HLA genetics? A) An individual HLA allele B) A set of HLA alleles inherited together from one parent C) The sum of all HLA alleles in a population D) The process of HLA gene expression Answer: B
Associateination Exam
Question 16. Which of the following is a key difference between innate and adaptive immunity? A) Adaptive immunity is antigen-specific B) Innate immunity develops memory C) Innate immunity is slower to respond D) Adaptive immunity is present at birth Answer: A Explanation: Adaptive immunity is specific to particular antigens and develops memory, whereas innate immunity is non-specific and lacks memory. Question 17. Which laboratory method utilizes beads coated with HLA antigens to detect anti-HLA antibodies?
Associateination Exam
A) Complement-Dependent Cytotoxicity (CDC) B) Luminex assay C) Flow cytometry crossmatch D) Mixed lymphocyte reaction Answer: B Explanation: The Luminex assay uses fluorescent beads coated with HLA antigens to detect and differentiate anti-HLA antibodies in serum. Question 18. Which of the following MHC molecules is expressed on virtually all nucleated cells? A) MHC class I B) MHC class II C) MHC class III
Associateination Exam
Question 20. The mean fluorescence intensity (MFI) in a Luminex assay reflects: A) The viability of lymphocytes B) The strength of antibody binding C) The amount of DNA present D) The specificity of T cell activation Answer: B Explanation: MFI in Luminex assays is proportional to the amount of antibody bound to the HLA-coated beads, reflecting antibody strength. Question 21. How does a flow cytometry crossmatch (FCXM) detect donor-specific antibodies?
Associateination Exam
A) By lysis of donor cells B) By measuring fluorescence-labeled antibody binding to donor cells C) By agglutination D) By PCR amplification Answer: B Explanation: FCXM uses fluorescent-labeled anti-human IgG to detect recipient antibodies binding to donor lymphocytes. Question 22. Which of the following is a common cause of HLA antibody formation in transplant candidates? A) Exposure to ultraviolet light B) Pregnancy C) Exercise
Associateination Exam
Explanation: In CDC crossmatch, recipient serum is incubated with donor lymphocytes and complement; cell lysis indicates the presence of cytotoxic antibodies. Question 24. Which of the following is NOT a function of macrophages? A) Phagocytosis B) Antigen presentation C) Antibody production D) Cytokine secretion Answer: C Explanation: Macrophages do not produce antibodies; this is the function of B cells.
Associateination Exam
Question 25. The primary role of B cells in immunity is to: A) Destroy infected cells directly B) Present antigen to CD8+ T cells C) Produce antibodies D) Activate the complement system directly Answer: C Explanation: B cells differentiate into plasma cells that synthesize and secrete antibodies. Question 26. During serological HLA typing, which test is used to detect the expression of HLA antigens on the cell surface? A) ELISA B) CDC (microlymphocytotoxicity) test
