Which interleukin is needed for differentiation of eosinophils:September 2009
**Core Concept**
Eosinophils are a type of white blood cell involved in allergic reactions, parasitic infections, and asthma. Their differentiation from hematopoietic stem cells requires specific cytokines. Interleukins are a group of cytokines that play crucial roles in the immune response and hematopoiesis.
**Why the Correct Answer is Right**
The interleukin responsible for eosinophil differentiation is IL-5. IL-5 is produced by T helper 2 (Th2) cells and mast cells. It acts on the eosinophil progenitor cells to promote their differentiation and maturation. IL-5 also plays a role in the activation and survival of mature eosinophils. The IL-5 receptor is composed of two subunits, IL-5RΞ± and IL-5RΞ², which are involved in signal transduction. The binding of IL-5 to its receptor triggers a cascade of intracellular signaling events that ultimately lead to eosinophil differentiation.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because IL-2 is primarily involved in the proliferation and differentiation of T cells, rather than eosinophils.
* **Option B:** This option is incorrect because IL-4 is involved in the differentiation of naive helper T cells to Th2 cells, which produce IL-5, but it is not directly involved in eosinophil differentiation.
* **Option C:** This option is incorrect because IL-12 is involved in the differentiation of naive helper T cells to Th1 cells, which produce IFN-Ξ³, and is not directly involved in eosinophil differentiation.
**Clinical Pearl / High-Yield Fact**
IL-5 is a key cytokine in the pathogenesis of eosinophilic disorders, such as asthma and hypereosinophilic syndrome. In these conditions, elevated levels of IL-5 can lead to increased eosinophil production and activation, contributing to tissue damage and inflammation.
**Correct Answer:** C.