The chemokine CXC ligand 13 (CXCL13), also known as B-lymphocyte chemokine (BLC) or BCA-1, is expressed at high levels in human liver, spleen, lymph nodes and intestine. It selectively chemotaxis B cells belonging to the B-1 and B-2 subpopulations and exhibits its function by interacting with the chemokine receptor CXCR5.CXCL13, together with its receptor CXCR5, regulates the B-cell architecture in lymphoid follicles. In T cells, the expression of CXCL13 is thought to reflect the origin of T cell, especially follicular helper T cell (Tfh) germinal centers. Thus CXCL13 expression in T-cell lymphomas, such as angioimmunoblastic T-cell lymphoma, is thought to reflect the origin of the tumor T-cell germinal center.