<prompt> Abatacept is ?TNF alpha inhibitorInhibitor of co-stimulation of T cellsIL-1 receptor antagonistMonoclonal antibody against IL-6 receptor  <response>: Ans. is b i.e., Inhibitor of co-stimulation of T cells T-cell costimulatory blockers Abatacept It is a fusion protein that combines the extracellular domain of the molecule CTLA4 CD 154 with the Fc poion of a human immunoglobulin. It interferes with the interactions between antigen presenting cells and T lymphocytes. Therefore, it affects early stages in the pathogenic cascade of event in RA. CTLA4 has high affinity for CD 28 when abatacept binds to CD28 on T cell surface, it prevents the second signal from being delivered, thus turning down the T cell response. Additional effects are decreasing the production of T cell-derived cytokines including TNF. 