🛡️ Immunology: One Night Revision & Cram Sheet
Give a mechanistic account of how the human immune system distinguishes self from non-self and from altered self. The course follows the barriers and receptors that respond at once, the lymphocytes that are selected and then remember, the effector molecules they deploy, and the patterns that appear when recognition fails, over-reacts, or is aimed at a transplant or a tumour. It also fixes what the common assays report, so that a result can be read as evidence.
🌟 Core Axioms & High-Yield Golden Rules
8 Core PrinciplesNon-negotiable foundational truths frequently tested in direct conceptual and numerical exam questions. Click checkbox to mark as mastered.
Innate vs. Adaptive Immunity: Innate uses germline-encoded PRRs (TLRs, NLRs) recognizing PAMPs; Adaptive uses somatic recombination (RAG1/2) for diverse BCRs and TCRs with immunological memory.
💡 PRRs recognize PAMPsMHC Class I presents endogenous antigens (8-10 amino acids) to CD8+ Cytotoxic T cells; processed via ubiquitin-proteasome pathway and loaded via TAP transporter.
💡 MHC I * CD8 = 8 (Rule of 8)MHC Class II presents exogenous antigens (13-25 amino acids) to CD4+ Helper T cells; invariant chain (CLIP) prevents premature binding until degraded in late endosomes/lysosomes by HLA-DM.
💡 MHC II * CD4 = 8 (Rule of 8)Antibody Isotypes: IgM is pentameric (primary response, activates complement); IgG is monomeric (most abundant in serum, crosses placenta); IgA is dimeric with J-chain and secretory component (mucosal secretions); IgE binds Fc-epsilon-RI on mast cells (Type I allergy/parasites).
💡 GAMED: IgG, IgA, IgM, IgE, IgDComplement activation: Classical (antibody-antigen, C1qrs -> C4b2a), Lectin (MBL/MASP -> C4b2a), Alternative (spontaneous C3 tickover -> C3bBb); all converge on C3 convertase -> C5 convertase -> Membrane Attack Complex (C5b-6-7-8-9 / MAC).
💡 All pathways converge on C3 convertaseV(D)J Recombination: RAG1 and RAG2 endonucleases recognize 12/23 RSS (recombination signal sequences); Artemis opens hairpin loops; TdT (terminal deoxynucleotidyl transferase) adds N-nucleotides, creating junctional diversity.
💡 12/23 rule + TdT junctional diversityT cell differentiation: Th1 (IL-12/IFN-gamma -> T-bet, cell-mediated immunity/macrophages); Th2 (IL-4 -> GATA-3, humoral/anti-parasite/allergy); Th17 (IL-6/TGF-beta -> ROR-gamma-t, neutrophil recruitment/fungi); Treg (TGF-beta/IL-2 -> FoxP3, immunosuppression).
💡 Th1 = T-bet | Th2 = GATA3 | Treg = FoxP3Hypersensitivity Types (Gell & Coombs): Type I (Immediate / IgE / Anaphylaxis); Type II (Cytotoxic / IgG/IgM against cell surfaces); Type III (Immune complex deposition / Serum sickness); Type IV (Delayed-type / T cell-mediated / Contact dermatitis).
💡 ACID: Anaphylactic, Cytotoxic, Immune complex, Delayed📚 Chapter-by-Chapter Rapid Cram Breakdown
12 ModulesHigh-density review of every curriculum chapter. Click any chapter title to view full in-depth lecture notes.
- Master Speed, specificity, memory: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master humoral and cell-mediated immunity: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master primary and secondary responses: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master clonal selection: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master tolerance: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
Cells and organs →
- Master Haematopoiesis: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master myeloid and lymphoid cells: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master primary and secondary lymphoid organs: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master lymph-node anatomy: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master Surface defences: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master PAMPs and PRRs: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master Toll-like receptors: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master inflammasomes: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master cGAS–STING: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master Three activation routes: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master opsonisation and the MAC: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master the respiratory burst: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master fever and the acute phase: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master NK cells: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master Epitopes and haptens: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master isotypes: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master affinity and avidity: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master effector functions: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master monoclonal antibodies: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master V(D)J recombination: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master allelic exclusion: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master hypermutation and class switch: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master tolerance checkpoints: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master germinal centres: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master MHC I and MHC II: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master polymorphism: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master cytosolic and endosomal processing: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master cross-presentation: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master Thymic selection: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master three signals: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master helper subsets: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master CD8 killing: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master memory and regulation: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
Cytokines as a network →
- Master Functional groups: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master pleiotropy and redundancy: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master chemokines: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master cytokine storm: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
Failures of immunity →
- Master Hypersensitivity I–IV: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master autoimmunity: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master primary immunodeficiency: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master HIV: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master Allorecognition: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master graft-versus-host: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master checkpoints: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master vaccine types: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master herd immunity: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
Immunological methods →
- Master ELISA: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master western blot: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master immunofluorescence: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master flow cytometry and CD markers: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
- Master precipitation and agglutination: understand underlying structural mechanisms, biochemical pathways, and diagnostic indicators.
⚖️ Must-Know Comparison & Distinction Tables
2 TablesSide-by-side matrices comparing commonly confused biological mechanisms, kinetic types, and pathways.
MHC Class I vs. MHC Class II Antigen Presentation
| Feature | MHC Class I | MHC Class II |
|---|---|---|
| Expressed On | All nucleated cells & platelets (NOT mature RBCs) | Professional APCs only (Dendritic cells, Macrophages, B cells) |
| Presenting To | CD8+ Cytotoxic T Lymphocytes (CTLs) | CD4+ T Helper Lymphocytes (Th1, Th2, Th17) |
| Antigen Origin | Endogenous (cytoplasmic, viral, tumor proteins) | Exogenous (phagocytosed bacteria, extracellular proteins) |
| Processing Machinery | Proteasome degradation -> TAP1/TAP2 translocation into ER | Endosome/lysosome acidification -> HLA-DM removes CLIP |
Gell and Coombs Hypersensitivity Types
| Type | Mechanism & Mediators | Onset Time | Classic Clinical Examples |
|---|---|---|---|
| Type I (Immediate) | IgE antibodies bind mast cells -> Histamine release | 15 - 30 minutes | Anaphylaxis, allergic asthma, hay fever |
| Type II (Cytotoxic) | IgG/IgM bind fixed tissue antigens -> Complement / ADCC | Minutes to hours | Hemolytic disease of newborn (Rh), Myasthenia gravis, Goodpasture |
| Type III (Immune Complex) | Antigen-antibody complexes deposit in microvasculature | Hours to days | SLE (Lupus), Post-streptococcal glomerulonephritis, Serum sickness |
| Type IV (Delayed-Type) | Sensitized Th1/CTLs release cytokines -> Macrophage activation | 48 - 72 hours | Tuberculin skin test (Mantoux), Contact dermatitis (poison ivy) |
⚠️ Examiner Traps & Common Student Mistakes
1 PitfallsClassic trap questions designed by examiners to catch uncritical students. Don't lose easy marks here!
Class Switching vs Somatic Hypermutation Mechanism
Thinking alternative splicing changes an antibody from IgM to IgG.
Co-expression of IgM and IgD on naive B cells is due to alternative RNA processing. However, class switching to IgG, IgA, or IgE involves IRREVERSIBLE DNA recombination mediated by AID (Activation-Induced Cytidine Deaminase).
📐 Key Formulas & Numerical Constants
2 FormulasStandard Equilibrium Constant
Keq = [Products] / [Reactants]Determines direction of chemical/biological reactions at dynamic equilibrium.
Relative Quantitative Ratio
Ratio = Experimental_Value / Baseline_ControlStandardizes comparative fold-change in quantitative biological assays.
🏛️ Landmark Scientists & Nobel Discoveries
6 PioneersFrequently tested in historical milestone and match-the-following exam questions.
Louis Pasteur
Major landmark discoveries
Robert Heinrich Hermann Koch
🏅 Nobel Prize in Physiology or Medicine (1905) for his investigations and discoveries in relation to tuberculosisMajor landmark discoveries
Sir Alexander Fleming
🏅 Nobel Prize in Physiology or Medicine (1945) for the discovery of penicillin and its curative effect in various infectious diseasesMajor landmark discoveries
Edward Jenner
Major landmark discoveries
Paul Ehrlich
🏅 Nobel Prize in Physiology or Medicine (1908) in recognition of his work on immunityMajor landmark discoveries
Élie Metchnikoff (Ilya Ilyich Mechnikov)
🏅 Nobel Prize in Physiology or Medicine (1908) in recognition of his work on immunityMajor landmark discoveries
🎯 Rapid-Fire Active Recall Checklist
4 QuestionsTest your memory before stepping into the exam hall. Try to answer mentally, then tap "Reveal Answer" to verify!