Which of the following are chemokines?
**Core Concept**
Chemokines are a family of small cytokines, or signaling molecules, that play a crucial role in the recruitment of immune cells to sites of infection or inflammation. They are classified into four main subfamilies: CXC, CC, CX3C, and XC chemokines, based on the arrangement of conserved cysteine residues.
**Why the Correct Answer is Right**
Chemokines interact with specific G protein-coupled receptors on the surface of immune cells, triggering a cascade of signaling events that lead to the migration of these cells towards the chemokine source. The CXC chemokine family, for example, is known to attract neutrophils and other granulocytes, while the CC chemokine family recruits monocytes and lymphocytes. The correct answer is a chemokine that belongs to one of these subfamilies.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is not a chemokine. Chemokines are typically smaller proteins with a specific structure and function, whereas this option does not fit this description.
**Option B:** This option is also incorrect because it is not a chemokine. While it may be involved in immune responses, it does not belong to the chemokine family.
**Option C:** This option is incorrect because it is not a chemokine. It may have some functional similarities to chemokines, but it is a distinct class of molecules.
**Clinical Pearl / High-Yield Fact**
Chemokines play a critical role in the pathogenesis of many inflammatory and infectious diseases, including asthma, atherosclerosis, and HIV/AIDS. Understanding the chemokine system is essential for developing effective therapies for these conditions.
**Correct Answer:** C. **IL-8** is a CXC chemokine that attracts neutrophils and other granulocytes to sites of inflammation.