Definition

A soluble fusion protein consisting of the extracellular domain of human cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) linked to a modified Fc (hinge, CH2, and CH3 domains) portion of human immunoglobulin G1 (IgG1) with immunosuppressive activity. Abatacept binds CD80 and CD86 on antigen presenting cells (APCs), blocking interaction with CD28 on T lymphocytes, which initiates a co-stimulatory signal required for full activation of T lymphocytes.