Immunbiologie und Gesundheit / Immunology and health
Immunology items expect a clean separation of innate and adaptive responses, correct cell-to-function mapping, and a mechanistic explanation of vaccination or allergy. Graph tasks with antibody titres and questions about why antibiotics fail against viruses are common.
Innate immunity
- Barriers (skin, mucous membranes, stomach acid), then inflammation, phagocytes (macrophages, neutrophils), natural killer cells, complement and interferons.
- Fast, non-specific, no memory; recognises conserved molecular patterns rather than one antigen.
Adaptive immunity
- Humoral: B cells bind antigen, are activated with helper T-cell support, proliferate and differentiate into antibody-secreting plasma cells and long-lived memory B cells.
- Antibody structure: two heavy and two light chains, variable antigen-binding sites, constant region determining class (IgM, IgG, IgA, IgE, IgD).
- Cell-mediated: helper T cells recognise antigen presented on MHC II and release cytokines; cytotoxic T cells recognise antigen on MHC I and kill infected cells.
- Memory gives a faster, stronger secondary response, mostly IgG instead of IgM.
Vaccines, allergy and disease
- Vaccines present antigen without causing disease: live attenuated, inactivated, subunit/toxoid, mRNA or vector. Booster doses raise the titre and herd immunity protects those who cannot be vaccinated.
- Allergy is an IgE-mediated hypersensitivity: allergen cross-links IgE on mast cells → histamine release → vasodilation, bronchoconstriction.
- Antibiotics act on bacterial targets (cell wall, ribosomes) and do not affect viruses; resistance spreads by selection.
Worked example
An antibody titre curve shows a small IgM peak at day 7 on first exposure, a later IgG peak, and after a second exposure at day 200 a rapid, much higher IgG response appearing within about three days. Reasoning: first exposure requires clonal selection and differentiation, hence the delay; memory B cells from the first exposure are already present, so the second exposure bypasses the slow steps. The dominance of IgG indicates class switching had already occurred.
Traps that cost marks
Naming plasma cells as the memory cells; saying antibiotics cure influenza; claiming a vaccine gives immediate protection; mixing up IgE (allergy) with IgG (memory and secondary response); forgetting that T cells recognise antigen only when presented on MHC.