Strongly chemotactic for B-lymphocytes, weakly for spleen monocytes and macrophages but no chemotactic activity for granulocytes. Binds to BLR1/CXCR5. May play a role in directing the migration of B-lymphocytes to follicles in secondary lymphoid organs. Found in spleen (B-cell-rich zone or follicles), Peyer patches (strongest within germinal centers and extending to the mantle zone) and lymph nodes (in reticular pattern in follicles). Belongs to the intercrine alpha (chemokine CxC) family.