CXCL13 and secondary progressive multiple sclerosis: While TLOs formation was noticed in the brains of SPMS patients but not in primary-progressive MS (PPMS) or RRMS by Serafini et al. [19], intracerebral expression of CXCL13 and BAFF was shown to be accompanied by formation of lymphoid like structures in animal model of relapsing EAE [21].