B cells, immunoglobulin classes and antibody responses
B-cell development, T-dependent and T-independent responses, class switching and affinity maturation, the properties of each immunoglobulin class, IgG half-life and FcRn, and how these explain serology, vaccine responses, antibody deficiency, immunoglobulin replacement and B-cell depletion.
Tier 1Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- B cells make antibody after differentiating into plasma cells. Most protein antigens need T-cell help (T-dependent response), which brings class switching, affinity maturation and memory.
- Polysaccharide antigens trigger T-independent responses: mainly IgM, low affinity, little memory, poor before age 2 and after splenectomy.
- Five classes: IgM (first, pentamer), IgG (most abundant, crosses placenta, half-life 21 days), IgA (mucosal), IgE (mast cells, helminths, allergy), IgD (naive B-cell receptor).
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Sources
- Cellular and Molecular Immunology (10th ed.)Elsevier (Abbas, Lichtman and Pillai), 2022
- Janeway's Immunobiology (10th ed.)W. W. Norton (Murphy, Weaver and Berg), 2022
- Criteria for the clinical use of immunoglobulin in Australia (Version 3)AU/NZNational Blood Authority, 2018 (current edition)
- Australian Immunisation Handbook: Pneumococcal diseaseAU/NZAustralian Government Department of Health, Disability and Ageing
- Primary immunodeficiency and immunoglobulin replacement: information for health professionalsAU/NZAustralasian Society of Clinical Immunology and Allergy (ASCIA)
- Last updated
- 14 November 2026
What changed
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