CD185, also known as CXCR5 or Burkitt lymphoma receptor 1 （BLR1）, is a G protein-coupled seven-transmembrane receptor that belongs to the CXC chemokine receptor family. It is specifically expressed in Burkitt's lymphoma and lymphatic tissues, such as follicles in lymph nodes and the spleen, and plays a crucial role in B cell migration and the development of lymph nodes and Peyer's patches. CXCR5 enables T cells to migrate to lymph node and B cell zones, which is essential for the production of high-affinity antibodies as B cells and T cells need to interact to activate the Ig class switch. This receptor is expressed on both CD4 and CD8 T cells and is often regarded as a defining marker for T Follicular Helper （Tfh） cells.