CTLA-4 (CD152) is the first identified co-inhibitory molecule and clinically targeted immune checkpoint receptor, expressed on T cells where it primarily downregulates early T cell activation. CTLA-4 counteracts CD28 activity, a T cell co-stimulatory receptor, by binding to CD80 (B7-1) and CD86 (B7-2) with higher affinity. By outcompeting CD28 for these ligands, CTLA-4 diminishes T cell activation and delivers inhibitory signals, playing crucial roles in both innate and adaptive immune responses.

Abbreviations:

IDDM12, CELIAC3, GSE, CTLA-4, CD152.