Delayed type of hypersensitivity is seen in following except –
**Core Concept**
Delayed type of hypersensitivity, also known as cell-mediated immunity, is a type of immune response that involves the activation of T lymphocytes. This type of response is typically seen in reactions to foreign substances, such as tuberculin in the Mantoux test, and is characterized by a lag period of 48-72 hours before the onset of symptoms.
**Why the Correct Answer is Right**
Delayed type of hypersensitivity is mediated by T helper 1 (Th1) cells, which activate macrophages to engulf and digest foreign particles. The cytokines released by Th1 cells, such as interferon-gamma, also induce the activation of macrophages, leading to the release of inflammatory mediators and the subsequent symptoms of delayed hypersensitivity. This type of response is often seen in conditions such as tuberculosis and sarcoidosis.
**Why Each Wrong Option is Incorrect**
**Option A:** This option would be incorrect if it referred to a type of hypersensitivity reaction that does not involve cell-mediated immunity, such as anaphylaxis or type I hypersensitivity. However, without the actual option text, it is unclear why this option would be incorrect.
**Option B:** This option would be incorrect if it referred to a condition or substance that does not induce a delayed type of hypersensitivity response. However, without the actual option text, it is unclear why this option would be incorrect.
**Option C:** This option would be incorrect if it referred to a type of hypersensitivity reaction that is not mediated by cell-mediated immunity, such as a type II or type III hypersensitivity reaction. However, without the actual option text, it is unclear why this option would be incorrect.
**Option D:** This option would be incorrect if it referred to a condition or substance that induces an immediate type of hypersensitivity response, such as anaphylaxis or type I hypersensitivity. However, without the actual option text, it is unclear why this option would be incorrect.
**Clinical Pearl / High-Yield Fact**
Delayed type of hypersensitivity is often used as a diagnostic tool in conditions such as tuberculosis and sarcoidosis. The Mantoux test, which involves injecting tuberculin into the skin and observing for a delayed hypersensitivity response, is a common example of this type of test.
**Correct Answer:** None provided, please provide the options for a complete explanation.