Question

T cells and macrophages are involved in which type of hypersensitivity?

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

Hint:

Type IV hypersensitivity is a cell-mediated immune response, and unlike other types, it does not involve antibodies.

Answer 1

The Correct Option is D

Type IV hypersensitivity, also known as delayed-type hypersensitivity (DTH), is a cell-mediated immune response primarily involving T cells (CD4+ T helper cells and cytotoxic T cells) and macrophages. This hypersensitivity does not involve antibodies but rather the activation of T cells and the subsequent recruitment of macrophages to the site of infection or injury, leading to inflammation and tissue damage.

(1) Type IV Hypersensitivity:
- This type of hypersensitivity is responsible for conditions such as contact dermatitis, tuberculin reactions (like the Mantoux test), and transplant rejection. - Macrophages play a key role in the inflammatory response in Type IV hypersensitivity.

(2) Why Other Options Are Incorrect:
- Type I Hypersensitivity (Option 1) involves IgE-mediated allergic reactions, such as hay fever or anaphylaxis, and is not associated with T cells and macrophages.
- Type II Hypersensitivity (Option 2) involves antibody-mediated destruction of cells, often through IgG or IgM, and does not primarily involve T cells and macrophages.
- Type III Hypersensitivity (Option 3) involves the formation of immune complexes that cause tissue damage but does not primarily involve T cells and macrophages.

Conclusion: T cells and macrophages are central to Type IV hypersensitivity, where they mediate delayed immune responses leading to inflammation and tissue damage.