Human Cytotoxic T-Lymphocyte Protein 4 (CTLA4) Protein

Background

Cytotoxic T-lymphocyte associated protein 4 (CTLA-4), encoded by the CTLA4 gene on chromosome 2, is an essential immune checkpoint receptor primarily expressed on activated T cells and regulatory T cells (Tregs). CTLA-4 plays a crucial role in maintaining immune homeostasis by delivering inhibitory signals to downregulate T cell activation and proliferation. This receptor functions by binding to the ligands CD80 (B7-1) and CD86 (B7-2), which are expressed on antigen-presenting cells (APCs). By inhibiting excessive immune responses, CTLA-4 prevents autoimmunity and maintains immune tolerance to self-antigens. CTLA-4 is the first immune checkpoint to have been targeted for immunotherapy, exemplified by the development of the monoclonal antibody ipilimumab, which blocks CTLA-4 to boost anti-tumor immune responses. Given its significance in regulating immune responses, CTLA-4 is a focus of research in fields ranging from oncology to autoimmune disorders.