**Core Concept**
The question is testing the student's knowledge of chemokines, a subgroup of cytokines involved in the recruitment of leukocytes to sites of inflammation. Chemokines are classified into four subfamilies: C-C (beta), C-X-C (alpha), C (gamma), and CX3C (delta) chemokines. The C-X-C chemokines are characterized by two conserved cysteine residues separated by any amino acid.

**Why the Correct Answer is Right**
IL-8 (Interleukin-8) is a classic example of a C-X-C chemokine. It is produced by macrophages and other cell types in response to inflammatory stimuli, such as bacterial lipopolysaccharide. IL-8 acts on its receptor, CXCR1 and CXCR2, to recruit neutrophils to the site of inflammation. The C-X-C chemokine motif in IL-8 allows it to bind to these receptors, triggering a signaling cascade that leads to neutrophil chemotaxis and activation.

**Why Each Wrong Option is Incorrect**
* **Option A:** MCP-1 (Monocyte Chemoattractant Protein-1) is a C-C chemokine, not a C-X-C chemokine. It is involved in the recruitment of monocytes and other immune cells to sites of inflammation.
* **Option B:** RANTES (Regulated on Activation, Normal T Cell Expressed and Secreted) is a C-C chemokine, not a C-X-C chemokine. It is involved in the recruitment of T cells, eosinophils, and basophils to sites of inflammation.
* **Option D:** None listed as an option is a C-X-C chemokine. However, if another option was given, it would be evaluated in the same manner as above.

**Clinical Pearl / High-Yield Fact**
Understanding the chemokine subfamilies is crucial for understanding the mechanisms of inflammation and immune responses. The C-X-C chemokines, like IL-8, play a key role in recruiting neutrophils to sites of infection and inflammation.

**Correct Answer:** .