C-C beta chemokine includes
**Core Concept**
C-C beta chemokines are a subgroup of chemokines that play a crucial role in recruiting immune cells to sites of inflammation. These chemokines are characterized by the presence of two conserved cysteine residues separated by one non-conserved residue, hence the name C-C. They primarily bind to the CCR1, CCR3, CCR4, CCR5, and CCR8 receptors, mediating various biological responses.
**Why the Correct Answer is Right**
Lymphotactin, also known as XCL1, is a C-C beta chemokine that selectively attracts T cells and natural killer cells. It is produced by activated T cells, macrophages, and dendritic cells, and plays a key role in the recruitment of these cells to the site of inflammation. The mechanism of lymphotactin involves binding to the XCR1 receptor, which is expressed on the surface of T cells and natural killer cells.
**Why Each Wrong Option is Incorrect**
**Option A:** Fractalkine is a chemokine that belongs to the C-X3-C chemokine family, not the C-C beta chemokines. It is unique in that it is both a chemokine and a chemokine receptor.
**Option B:** Eotaxin is a C-C chemokine, but it belongs to the C-C alpha chemokine subgroup, not the C-C beta chemokines. It is involved in the recruitment of eosinophils to sites of allergic inflammation.
**Option C:** Monokine induced by interferon-gamma (MIG) is a C-X-C chemokine, not a C-C beta chemokine. It is involved in the recruitment of T cells and macrophages to sites of inflammation.
**Clinical Pearl / High-Yield Fact**
C-C beta chemokines, such as lymphotactin, play a critical role in the recruitment of immune cells to sites of inflammation, and their dysregulation has been implicated in various inflammatory and immunological disorders, including autoimmune diseases and cancer.
**Correct Answer: D. Lymphotactin**