CTLA4 (cytotoxic T-lymphocyte–associated antigen 4, aka CD152) is a transmembrane protein member of the immunoglobin superfamily. This protein receptor plays a key role in downregulating immune responses (e.g., inhibit T-cell
Its expression relies on the stimulation of TCR and the binding between CD28 and B7 (B7-1/CD80 & B7-2/CD86), which both promote T-cell activation. Stimulating signals from TCR and CD28-B7 binding release CTLA4 from
vesicles and translocates CTLA4 to the cell membrane where CTLA4 undergoes dimerization.
Since CTLA4 has a much higher affinity for B7, this competitive binding could prevent signals from CD28-B7 binding. CTLA4 may also inhibit T-cell activation through the dephosphorylation of TCR-signaling proteins or the
interference with Akt signaling.
Click below to view & download the CTLA4 pathway map.