B cells in RA mice express high levels of the osteoblast inhibitors C-C motif chemokine ligand 3 and TNF, and inhibit mesenchymal precursor cell differentiation into osteoblasts by activating extracellular signal-regulated kinase and NF-κB signalling pathways, while B cell depletion attenuates bone erosion and osteoblast inhibition in RA mice 71. Here, TNF is linked to rheumatoid arthritis.