TNF and rheumatoid arthritis: To further examine the inhibitory effect of RA B cells on osteoblastic bone formation in vivo, we mixed WT MPCs with BM B cells from WT, TNF-Tg, TNF-Tg/CCL3-KO, TNF-Tg/TNF-KO, or TNF-Tg/CCL3-KO/TNF-KO mice in Gelfoam and surgically implanted them subcutaneously into recipient SCID mice in a standard bone formation assay31.