GATE 2021 BT – Question 40

General Biology · Immunology: MHC, antigen processing and presentation, regulation, tolerance, hypersensitivity, autoimmunity, immunodeficiency, graft vs host disease, vaccines · 2 marks · Multiple choice

Match P type I, Q type II, R type III and S type IV hypersensitivity to: 1 erythroblastosis fetalis, 2 host reaction to bee venom, 3 systemic lupus erythematosus, 4 tuberculin reaction.

P-2,Q-3,R-1,S-4
P-3,Q-1,R-4,S-2
P-2,Q-3,R-4,S-1
P-2,Q-1,R-3,S-4

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Correct answer: (D) P-2,Q-1,R-3,S-4

Explanation

Gell and Coombs classification of hypersensitivity:

**Type I (immediate, IgE-mediated):** allergy and anaphylaxis, for example the reaction to **bee venom**. P-2.
**Type II (antibody-mediated cytotoxicity):** antibodies bind cell-surface antigens, for example **erythroblastosis fetalis** (Rh incompatibility). Q-1.
**Type III (immune complex):** deposited complexes cause damage, for example **systemic lupus erythematosus**. R-3.
**Type IV (delayed, T-cell mediated):** appears after 24 to 72 hours, for example the **tuberculin** reaction. S-4.

Match: **P-2, Q-1, R-3, S-4** (option D).