Programmed cell death protein 1 and Cytotoxic T-lymphocyte–associated protein 4 (PD-1 and CTLA-4)

Programmed cell death protein 1 (PD-1) and Cytotoxic T-lymphocyte–associated protein 4 (CTLA-4) are inhibitory immune checkpoint receptors expressed on T lymphocytes. Both are crucial negative regulators of T-cell immune function, helping maintain immune homeostasis and self-tolerance by downregulating immune responses. PD-1 is expressed on activated T cells, B cells, and myeloid cells, interacting with its ligands PD-L1 and PD-L2 found on multiple cell types, especially in peripheral tissues. CTLA-4 is mainly found on regulatory T cells and activated T cells, interacting with CD80 and CD86 on antigen-presenting cells during T-cell priming, predominately in lymphoid tissues. In cancer, these checkpoints inhibit anti-tumor immunity, and antibody-mediated inhibition (immune checkpoint blockade) can restore or enhance anti-tumor T-cell activity but also carries substantial risks of immune-related adverse events[1][2][3].

Other names

Programmed cell death protein 1CD279Cytotoxic T-lymphocyte–associated protein 4CD152

Antibody blockade of PD-1/PD-L1 or CTLA-4 ligand interactions to promote T-cell activation against tumors or infected cells; Release of immune "brakes" to enhance endogenous anti-tumor or anti-pathogen immunity