Question

Type-1 hypersensitivity involves :
A. Immune complex
B. Cell mediated
C. IgE mediation
D. Antibody dependent cytotoxicity
E. Mast cell Degranulation
Choose the correct answer from the options given below :

• A. A, B and C only
• B. B and C only
• C. C and E only
• D. D and E only

Hint:

Mnemonic for the four types of hypersensitivity reactions: ACID
Type I: Allergic/Anaphylactic (IgE and mast cells)
Type II: Cytotoxic (IgG/IgM targeting cells)
Type III: Immune complex deposition
Type IV: Delayed (T-cell mediated, no antibodies)

Answer 1

The Correct Option is C

Step 1: Concept:
This question tests the clinical classification of immunological hypersensitivity reactions (the Gell and Coombs classification), specifically identifying the mechanisms behind Type I (immediate) hypersensitivity, which constitutes common allergies.

Step 2: Step-by-step Explanation:

• Type I Hypersensitivity is an immediate allergic reaction (like asthma, anaphylaxis, or hay fever). It is fundamentally mediated by IgE antibodies (Statement C).

• When an allergen binds to IgE antibodies that are already attached to the surface of mast cells and basophils, it cross-links them. This triggers the explosive release of histamine and other inflammatory mediators from the cell in a process called Mast cell degranulation (Statement E).

• For context regarding the incorrect statements:
- Antibody-dependent cytotoxicity (D) defines Type II hypersensitivity (IgG/IgM mediated).
- Immune complex deposition (A) defines Type III hypersensitivity.
- Cell-mediated (B) (T-cell driven) defines Type IV (delayed) hypersensitivity.
Therefore, the only correct components of a Type I reaction are C and E.

Step 3: Final Answer:
The correct combination is C and E only, matching option (C).