Innate + adaptive immunity: PRRs, complement, B/T cells, antibodies, V(D)J, MHC, clonal selection.
Immunology
Innate immunity
Germline-encoded, non-clonal, fast (<hours) first-line defence. Physical barriers, complement, phagocytes (macrophage, neutrophil,…
Adaptive immunity
Clonal, antigen-specific, memory-forming response (days-weeks). T cells (cellular) + B cells (humoral) with V(D)J-rearranged receptors.…
Pattern-recognition receptor (PRR)
Germline-encoded receptor detecting conserved pathogen features (PAMPs) or damage signals (DAMPs). Toll-like receptors (TLR1-10), NLRs,…
Complement system
Serum protease cascade of ~30 proteins. Three activation pathways (classical/lectin/alternative) converge on C3 convertase → C3b…
B cell
Bone-marrow-derived lymphocyte bearing surface immunoglobulin (BCR). Class-switches + somatically hypermutates in germinal centres.…
T cell
Thymus-matured lymphocyte bearing αβ-TCR (or γδ). Recognises antigen peptide + MHC. CD4+ helper, CD8+ cytotoxic, Treg, Th1/Th2/Th17, Tfh…
Antibody (immunoglobulin)
Y-shaped secreted BCR: two heavy + two light chains, variable antigen-binding (Fab) + constant (Fc) regions. Five classes: IgM (first), IgG…
V(D)J recombination
RAG1/2-mediated somatic rearrangement of V, D, J gene segments generating unique TCR and BCR per lymphocyte. Theoretical diversity ~10¹⁶.…
MHC (HLA)
Major histocompatibility complex: MHC-I (HLA-A/B/C) presents endogenous peptides to CD8+ T cells; MHC-II (HLA-DR/DP/DQ) presents exogenous…
Clonal selection theory
Burnet 1957: lymphocytes bear one receptor specificity before antigen encounter; antigen selects + expands cognate clones. Self-reactive…
Inflammation
Protective innate response to injury/infection: rubor (redness), calor (heat), tumor (swelling), dolor (pain), functio laesa. Mediated by…