Description
CTLA-4 (Cytotoxic T-Lymphocyte Antigen 4), also known as CD152, is a protein receptor that down regulates the immune system. It is a member of the immunoglobulin superfamily, which is expressed on the surface of Helper T cells and transmits an inhibitory signal to T cells. CTLA4 is similar to the T-cell co-stimulatory protein, CD28, and both molecules bind to CD80 and CD86, also called B7-1 and B7-2 respectively, on antigen-presenting cells. CTLA4 transmits an inhibitory signal to T cells, whereas CD28 transmits a stimulatory signal. Blockade of CTLA4 expression in vitro augmented HIV-specific CD4-positive T-cell function