TNFSF13B and immune system disorder: When endogenous BAFF present in CSF or in a BAFF-high serum sample (from a patient with common variable immunodeficiency) was affinity-purified on atacicept prior to size-fractionation at pH 8.2, only BAFF 3-mer was detected, indicating the BAFF in CSF and in CVID serum is not only 3-mer, but also unable to associate as 60-mer under favorable conditions (Figures 7G,H).