TNF and rheumatoid arthritis: T lymphocytes have critical roles in RA pathogenesis: they contribute to (1) autoantibody production by B lymphocytes including antibodies to citrullinated protein antigens (ACPAs) and autoantibodies against IgG Fc (92), (2) adjustment of fibroblast-like synoviocyte (FLS) activation through cell–cell interaction, (3) promotion of inflammatory cytokine production including IL-15, IL-8, and TNF-α by FLSs (91), (4) regulation of monocyte/macrophage activation, and (5) TNF-α production and osteoclast formation (93–95).