Q57.Given below are two statements:
Statement I:
Type I Hypersensitivity reaction is mediated by IgE.
Statement II:
Type III Hypersensitivity reaction is mediated by the formation of immune complexes and activation of complement.
In the light of the above statements, choose the most appropriate answer from the options given below:
(1) Both Statement I and Statement II are correct
(2) Both Statement I and Statement II are incorrect
(3) Statement I is correct but Statement II is incorrect
(4) Statement I is incorrect but Statement II is correct
Both Statement I and Statement II are correct. The correct answer is option (1).
Statement Analysis
Statement I (Correct): Type I hypersensitivity (immediate allergy) is indeed mediated by IgE antibodies. Allergens bind to IgE on mast cells/basophils, causing degranulation and release of histamine, leukotrienes—triggering anaphylaxis, asthma, hives within minutes.
Statement II (Correct): Type III hypersensitivity involves immune complex (Ag-Ab) deposition in tissues, activating complement (C3a, C5a), neutrophils—causing inflammation as in SLE, serum sickness, Arthus reaction.
Why Other Options Fail
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Option 2: Wrong; both statements accurately describe Gell-Coombs classification.
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Option 3: Wrong; Statement II correctly identifies Type III mechanism.
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Option 4: Wrong; Statement I is fundamentally true for Type I reactions.
Introduction to Hypersensitivity Statements
Type I hypersensitivity IgE type III immune complex complement activation represents core immunology for NEET exams. Statement I covers immediate allergic reactions; Statement II describes immune complex diseases—both Gell-Coombs Type I & III hallmarks.
Mechanism Breakdown
Type I (IgE-mediated):
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Sensitization: Th2 → B-cell → IgE production
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Effector: Allergen cross-links IgE → mast cell degranulation → histamine release
Type III (Immune complex):
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Formation: Soluble Ag + IgG/IgM complexes
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Pathology: Tissue deposition → complement activation → neutrophil influx → vasculitis
Clinical Examples
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Type I: Anaphylaxis (penicillin), asthma, hay fever
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Type III: SLE (glomerulonephritis), rheumatoid arthritis, post-strep GN
Exam Strategy
Both statements test classic hypersensitivity classification. Option 1 always correct for these standard definitions—avoid overthinking mechanisms.
