TACI-ligand interactions are required for T cell activation and collagen-induced arthritis in mice

Interactions of the tumor necrosis factor superfamily members B lymphocyte stimulator (BLyS) and a proliferation-inducing ligand (APRIL) with their re ceptors-transmembrane activator and CAML interactor (TACI) and B cell matur ation molecule (BCMA)-on B cells play an important role in the humoral immu ne response. Whereas BCMA is restricted to B cells,TACI is also expressed o n activated T cells; we show here that TACI-Fc blocks the activation of T c ells in vitro and inhibits antigen-specific T cell activation and priming i n vivo. In a mouse model for rheumatoid arthritis (RA), an autoimmune disea se that involves both B and T cell components,TACI-Fc treatment substantial ly inhibited inflammation, bone and cartilage destruction and disease devel opment. Thus, BLyS and/or APRIL are important not only for B cell function but for T cell-mediated immune responses. Inhibition of these ligands might have therapeutic benefits for autoimmune diseases, such as RA, that involv e both B and T cells.