CXCL13 and systemic lupus erythematosus: It is likely that markedly increased levels of CXCL13 expression in the synovial tissue of CIA mice may contribute to the chemotactic attraction of peritoneal B1a cells, a notion supported by previous findings that the CXCL13-CXCR5 axis is responsible for the aberrant trafficking of B1a cells to the kidney in murine lupus [6].