CXCL13, originally known as BLC (B-lymphocyte chemoattractant) or BCA-1 (B cell-attracting chemokine 1), is a homeostatic chemokine. It is constitutively secreted by stromal cells in B-cell areas of secondary lymphoid tissues (follicles), such as spleen, lymph nodes, tonsils, and Peyer's patches. CXCL13 plays a key role in orchestrating cell migration within spatially distinct regions of the secondary lymphoid organs. It strongly attracts B lymphocytes while promoting migration of only small numbers of T cells and macrophages. CXCL13 exerts its functions through its receptor CXCR5, which initially, was isolated from Burkitt Lymphoma and therefore designated as Burkitt's lymphoma receptor 1 (BLR1).