Which of the follow ing interleukin is secreted by T helper 2 cells –
**Question:** Which of the following interleukins is secreted by T helper 2 (Th2) cells?
**Core Concept:** Interleukins are a group of cytokines that play a crucial role in modulating the immune response. T helper 2 cells are a subset of helper T cells that are involved in the immune response against parasites and allergies. They secrete specific interleukins to regulate the immune system.
**Why the Correct Answer is Right:** Interleukin-4 (IL-4) is the correct answer because it is the primary cytokine secreted by Th2 cells. IL-4 primarily plays a role in promoting B cell activation, class switch recombination, and immunoglobulin isotype switching, which are essential for the immune response against parasites and allergens.
**Why Each Wrong Option is Incorrect:**
A. Interleukin-5 (IL-5) is not secreted by Th2 cells; it is produced by eosinophils and basophils, which are involved in the immune response against parasites.
B. Interleukin-9 (IL-9) is produced by activated CD4+ T cells but not specifically by Th2 cells.
C. Interleukin-13 (IL-13) is also secreted by Th2 cells and plays a role in the development of allergic inflammation and asthma.
D. Interleukin-10 (IL-10) is produced by regulatory T cells (Tregs) and macrophages and is not specific to Th2 cells.
**Clinical Pearl:** Th2 cells and their secreted cytokines play a vital role in the immune response against parasites and allergens. A deep understanding of interleukins and their roles in the immune system is essential for medical students and practitioners, especially in the context of allergy and parasitic infections.
**Correct Answer:** Interleukin-4 (IL-4) is the correct answer as it is the primary cytokine secreted by Th2 cells and plays a crucial role in the immune response against parasites and allergens.