CTLA4 and neoplasm: Furthermore, scFv PD-L1 antibody decreased the expression of T cell exhaustion markers PD-1, TIM-3, and CTLA-4 in xenograft tumor models in vivo but not in cultured cells in vitro, suggesting that additional mechanisms are underlying the regulation of PD-1, TIM-3, and CTLA-4 expression in the TME.