Complete loss of CTLA4 in mice induces lethal autoimmunity during the first three weeks after birth, indicating thevital role of CTLA4 in inhibiting autoimmune responses [ 10].In certain parts of Iran, such as Sistan and Baluchestan Province, OSCC is more prevalent than in other parts due to its proximity to Pakistan and India [ 11]. Here, CTLA4 is linked to Autoimmunity.