A transmembrane protein (CD152, 223 aa) of the immunoglobulin superfamily, found on activated T cells and similar to the T-cell costimulatory CD28. Both CTLA-4 and CD28 bind to B7-1 (CD80) and B7-2 (CD86) on antigen-presenting cells but CTLA4 transmits an inhibitory signal to T cells, whereas CD28 is stimulatory. The CTLA-4 cytoplasmic domain interacts with SH2 domain of Shp2 (protein tyrosine phosphatase) and possibly with PI3-kinase. Genetic variation in CTLA4 influences susceptibility to systemic lupus erythematosus, diabetes type 1, coeliac disease type 3, hepatitis B virus infection, and possibly susceptibility to Graves' disease.
Subjects: Medicine and Health.