In two commonly used lupus-prone mouse models, NZB/W F1 and MRL/lpr, transcript levels of renal CXCL13 and CXCR5 are consistently increased in aged lupus nephritic mice compared to nonlupus control mice or young mice prior to disease onset [22–25], suggesting their involvement in the development of LN. This evidence concerns the gene CXCL13 and systemic lupus erythematosus.