CXCR6 (CXC-chemokine receptor type 6) is a receptor for CXC chemokine CXCL16. CXCR6 is expressed by naive CD8 T cells, natural killer T cells, a subset of memory CD4 T cells and plasma cells. CXCR6 and its ligand play an important role in the trafficking of the cells expressing them. It is demonstrated that CXCL16+ macrophages in synovial fluid of rheumatoid arthritis patients lead to recruitment of CXCR6+ memory T cells, thereby contributing to the inflammatory cascade associated with rheumatoid arthritis pathology. CXCR6 is also used as a coreceptor by simian immunodeficiency viruses (SIVs) and by strains of HIV-2 and M-tropic HIV-1.