Since the CSF from patients without inflammation in the brain contains BAFF at a similar level as the CSF from MS patients (Krumbholz et al., 2005; Kowarik et al., 2012), we would assume that the majority of the BAFF in the CSF also in MS patients is derived from blood, an hypothesis that would fit with our observations that the CSF contains BAFF-3mer, and that serum permanently transforms BAFF 60-mer into BAFF 3-mer. The gene discussed is TNFSF13B; the disease is myeloid sarcoma.