CXCL12 and myeloid sarcoma: By using unsupervised pathway analysis, the occurrence of OCB in the CSF at MS onset was associated with the overexpression of molecules related to the B cell immune response, such as the lymphoid chemokines CXCL13 (p < 0.001), CXCL12 (p < 0.001), factors related to B cell activation and differentiation such as BAFF (p = 0.019), APRIL (p = 0.015), IL6 (p = 0.0005), and IL10 (p = 0.035) (Fig. 2b) or to those with a B cell regulatory role, such as OPN (p = 0.019).