The homeostatic chemokine CXCL13 (also called B cell-attracting chemokine 1 [BCA-1] or B-lymphocyte chemoattractant [BLC]) is constitutively expressed in secondary lymphoid tissue and initiates lymphoid neogenesis when expressed aberrantly. Recombinant human CXCL13 is a single non-glycosylated polypeptide chain containing 87 amino acids and mature human BCA-1 shares 64% amino acid sequence similarity with the mouse protein and 23-34% amino acid sequence identity with other known CXC chemokines. CXCL13 is a homeostatic chemokine for lymphocyte homing and positioning within follicles of secondary lymphoid tissues, acting through its cognate receptor, CXCR5. Besides, CXCL13 is a potent chemokine, produced by mature and recently recruited macrophages to sites of inflammation, which has antimicrobial and anti-angiogenic properties.