Recent studies identified IL-10-secreting B cells that inhibit immune responses and autoimmune diseases such as RA.28 Semiquantitative reverse transcription polymerase chain reaction (RT-PCR) assay showed that IL-10 gene expression was markedly elevated in the joints of BAFF-Trap-treated mice (Supplemental Fig. 4A, B). Here, IL10 is linked to autoimmune disease.