Which hypersensitivity type involves delayed T-cell mediated responses?

Which hypersensitivity type involves delayed T-cell mediated responses?

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

Answer: (D)

Type IV hypersensitivity is characterized by delayed T-cell mediated responses. This type of hypersensitivity is also known as cell-mediated immunity, as it primarily involves T lymphocytes rather than antibodies. In Type IV hypersensitivity, the body's immune response is initiated by T helper cells, which release cytokines that activate macrophages and cytotoxic T cells. This leads to inflammation and tissue damage typically occurring 24 to 48 hours after exposure to the antigen. Common examples of Type IV hypersensitivity include contact dermatitis (like reactions to poison ivy), granulation tissue formation, and the tuberculin reaction (the skin test for tuberculosis). The other types of hypersensitivity involve different mechanisms. Type I is mediated by IgE antibodies and is immediate, Type II is antibody-mediated and involves IgG or IgM targeting cells, and Type III is mediated by immune complexes, leading to inflammation. Each of these types involves various cells and antibodies, distinguishing them from the T-cell mediated response in Type IV hypersensitivity.

Type IV hypersensitivity is characterized by delayed T-cell mediated responses. This type of hypersensitivity is also known as cell-mediated immunity, as it primarily involves T lymphocytes rather than antibodies.

In Type IV hypersensitivity, the body's immune response is initiated by T helper cells, which release cytokines that activate macrophages and cytotoxic T cells. This leads to inflammation and tissue damage typically occurring 24 to 48 hours after exposure to the antigen. Common examples of Type IV hypersensitivity include contact dermatitis (like reactions to poison ivy), granulation tissue formation, and the tuberculin reaction (the skin test for tuberculosis).

The other types of hypersensitivity involve different mechanisms. Type I is mediated by IgE antibodies and is immediate, Type II is antibody-mediated and involves IgG or IgM targeting cells, and Type III is mediated by immune complexes, leading to inflammation. Each of these types involves various cells and antibodies, distinguishing them from the T-cell mediated response in Type IV hypersensitivity.