CTLA-4 immunoglobulin

CTLA-4 immunoglobulin (CTLA-4-Ig) is a class of soluble recombinant fusion proteins consisting of the extracellular domain of human cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) fused to the Fc portion of human immunoglobulin G (typically IgG1). CTLA-4-Ig acts as a selective co-stimulation modulator by binding with high affinity to CD80 (B7-1) and CD86 (B7-2) on antigen-presenting cells (APCs). This binding competitively blocks the interaction of CD80/CD86 with CD28 on T cells, thereby preventing the second co-stimulatory signal required for full T-cell activation, proliferation, and cytokine production. Prototypical members of this class include abatacept, which is approved for the treatment of rheumatoid arthritis, juvenile idiopathic arthritis, psoriatic arthritis, and the prophylaxis of acute graft versus host disease, and belatacept, a high-affinity variant approved for the prophylaxis of organ rejection in kidney transplant recipients.