CD185

CD185, a 42 kD G-protein coupled receptor with seven transmembrane regions. CXCR5 is expressed by mature B cells, follicular helper T cells, Burkitt’s lymphoma cells, and a subset of neurons. It plays a crucial role in directing cell migration to the B cell follicles within secondary lymphoid organs, which are key sites for initiating immune responses.

The ligand for the CXCR5 chemokine receptor is CXCL13 (also known as B-lymphocyte chemoattractant or BLC). CXCR5 plays an important role in the positioning and cognate interactions of B-cell chronic lymphocytic leukemia (CLL) cells with CXCL13-secreting CD68+ accessory cells within the lymphoid tissues. This interaction helps support the survival and proliferation of CLL cells in their protective microenvironment.

The high expression of CXCR5 on T follicular helper cells (T(FH)) and a subset of central memory CD4 T cells (T(CM)), suggesting that CXCR5(+) T(CM) may function similarly to T(FH) cells in supporting humoral immune responses. CXCR5(+) T(CM) exhibit B cell helper qualities, expressing high levels of CXCL13, inducing plasma cell differentiation and Ig secretion, and showing responsiveness to ICOS ligand costimulation and IL-10 secretion. These attributes are acquired through interaction with B cells, indicating a specialized role in promoting quick and efficient secondary humoral immune responses. In conclusion, CXCR5(+) T(CM) are proposed as a distinct memory cell subset specialized in supporting antibody-mediated immune responses.