CTLA4 and hepatocellular carcinoma: CTLA-4, an IgSF receptor, plays an important role in immune regulation by feeding a negative signal to T cells once an immune response has been initiated and completed.[19] In this case-control study, the role of CTLA-4 tagging polymorphisms (rs733618 T>C, rs231775 G>A, rs3087243 G>A, and rs16840252 C>T) in HCC susceptibility was assessed.