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BIO15 Chapter 18 Practical Applications of Immunology Overview: So today we're going to talk about Chapter 18 , which covers the practical applications of immunology. We’re going to talk about: Vaccines : the process, different types A few diagnostic tests you’re likely to encounter in clinical practice
History of Vaccines We’ve already talked a little about the history, and you may remember from the last lecture: Edward Jenner was the one who noticed that milkmaids exposed to cowpox developed a mild disease , but when smallpox came around, they didn’t get sick. They seemed immune. The word "vaccine" comes from this — "vaca" means cow. Thanks to Jenner's work, we have scientific documentation and process for developing vaccines.
Vaccination vs. Vaccine Vaccination : The process of deliberately exposing a person or animal to a harmless version of the pathogen to stimulate the immune system. Vaccine : The entity or suspension used — it contains the organism or a fraction of it (sometimes a toxin).
Effectiveness of Vaccines There’s a chart (older, up to 2010) showing that: o Before the measles vaccine (early 1960s), the U.S. had about 100,000 cases/year. o After widespread use, by 1995 , cases became almost undetectable. This drop in cases is directly attributed to the vaccine.
Concerns About Vaccines There were concerns that the polio vaccine caused autism. o Multiple studies have disproven this link. The lecture does not advocate for or against vaccines — just explains the science so you can make an informed decision. Example: COVID-19 Vaccine There’s a lot of work being done to develop it quickly. There are FDA regulations for a reason — complications can occur. Again, understand the science , then make your own decision.
Types of Vaccines
1. Live Attenuated Whole-Agent Vaccines Strongest immunity , usually lifelong Use live pathogens that replicate , but don’t cause disease Stimulates both humoral and cellular immunity 📌 Example: MMR vaccine (measles, mumps, rubella) 2. Inactivated Whole-Agent Vaccines Safer than live attenuated Use dead or inactive pathogens Cannot replicate Stimulate humoral immunity only Often require **boosters
- Subunit Vaccines / Recombinant Vaccines** Use only parts of the microbe (usually antigens) Can't replicate or cause disease Lab-engineered to target strong immune-stimulating fragments Safer but may require **boosters
- Toxoid Vaccines** For bacteria where the toxin , not the bacteria, causes disease Designed to generate antibodies that neutralize toxins Require boosters every 10 years Do **not produce strong memory response
- Conjugate Vaccines** Designed for young children or those with weak immune systems Combine a polysaccharide antigen with a protein toxin Cannot cause disease Safe for infants and toddlers 6. Nucleic Acid Vaccines Use DNA that codes for an antigen DNA is injected → person produces antigen → immune system produces antibodies
- Identify desired antigen
- Inject it into a mouse
- Allow immune response to occur
- Sacrifice the mouse, harvest the spleen
- Combine spleen cells (B cells) with myeloma (cancer) cells o These form hybridomas
- Hybridomas produce specific antibodies continuously
- Antibodies are isolated and used 📌 Common Example : Pregnancy tests use monoclonal antibodies to detect specific hormones
Serological Testing "Serology" = Testing of fluids like blood or sputum Two types:
1. Direct Tests Look for presence of pathogen Are they currently infected? 2. Indirect Tests Look for antibodies (evidence of past exposure or vaccination ) For viruses , we usually use indirect tests
Types of Serological Tests Agglutination Tests Antigen-antibody reactions → visible clumping Sensitive and easy to interpret Can be direct or indirect 📌 Commonly used for: Blood typing Bacteria/fungi detection Indirect Agglutination Drawbacks: Can’t distinguish: o Current vs. past infection o Infection vs. vaccine Antibody Titer: Measures concentration of antibodies
High IgM = recent or new infection High IgG = older infection or vaccine response
ELISA (Enzyme-Linked Immunosorbent Assay) 📌 You have a lab and Lobster activity on ELISA — know this for the exam
Direct ELISA – Detects pathogen/antigen
- Antibody coated to plastic well
- Patient’s serum added
- If antigen present , it binds the antibody
- Add secondary antibody with enzyme (chromogen)
- Add substrate → Color change = positive 📌 More color = higher concentration of pathogen
Indirect ELISA – Detects antibodies (exposure)
- Antigen coated on well
- Add patient serum
- If antibodies present , they bind to the antigen
- Add secondary antibody with chromogen
- Color change = patient has antibodies Useful for viruses or diseases hard to isolate
Visual Aids Animations in Canvas walk you through both ELISA types Definitely watch those before the test
Final Notes: There’s a lot more in the textbook , but for this class: 📌 Focus on : Vaccine types and mechanisms Sensitivity vs. specificity Monoclonal antibodies Agglutination and ELISA (direct vs. indirect) Use the lecture material and study guide to prioritize your studying.
