CXCL13, also known as BCA-1 (B Cell-Attracting chemokine 1) or BLC, , is a recently identified new CXC chemokines. This chemokine is expressed in the stomach, spleen, liver, appendix and lymph nodes. CXCL13 can only elicit its activities through CXCR5receptor. BCA-1/BLC is a potent chemoattractant for B lymphocytes, and induces weak chemotactic response in T cells and macrophages. It should be noticed that CXCL13 shows no activity on neutrophils and monocytes.