Another study has demonstrated that higher CSF IgM levels in treatment-naïve MS patients positively correlate with the CSF levels of molecules related to B-cell immunity (IL-10), recruitment (CXCL13 and CCL21), and macrophage/microglial activity (IL-12p70, CX3CL1 and CHI3L1), as well as white matter lesion numbers and disease activity after two years of follow-up, suggesting a potential role of IgM in the MS disease course (73). Here, CXCL13 is linked to myeloid sarcoma.