In order to explore the key factors that damage the BSCB during the progress of MS, this study screened and identified the chemokine (C‐X‐C motif) ligand 13 (CXCL13) was at an abnormally high level in the peripheral blood serum from both clinical MS patients and EAE mice. This evidence concerns the gene CXCL13 and myeloid sarcoma.