Question

Which of the following is called as cell-mediated (delayed) hypersensitivity:

• A. Type II hypersensitivity
• B. Type I hypersensitivity
• C. Type III hypersensitivity
• D. Type IV hypersensitivity

Hint:

Type IV hypersensitivity involves T-cells and is delayed, unlike the rapid antibody-mediated responses seen in Type I, II, and III hypersensitivities.

Answer 1

The Correct Option is D

Step 1: Understanding hypersensitivity types. Hypersensitivity reactions are classified into four types based on their immune mechanisms:
 - Type I: Immediate hypersensitivity (e.g., allergies, mediated by IgE). 
- Type II: Antibody-mediated cytotoxic hypersensitivity. 
- Type III: Immune complex-mediated hypersensitivity. -
 Type IV: Cell-mediated (delayed) hypersensitivity. 

Step 2: Characteristics of Type IV hypersensitivity. Type IV hypersensitivity is mediated by T-cells rather than antibodies. It is referred to as delayed hypersensitivity because the reaction typically occurs 24–72 hours after exposure to the antigen. 
Examples include: 
- Tuberculin skin test. 
- Contact dermatitis (e.g., poison ivy). 
- Granuloma formation in chronic infections. 

Step 3: Why other options are incorrect. - Type I, II, and III are antibody-mediated hypersensitivities and are not delayed or cell-mediated.