CTLA4 and neoplasm: Activated CD8+T cells pre-treated with sHLA-G exhibited increased level of ILT-2 protein, accompanied by a significant increase in the expression of CTLA-4, PD-1, and TIM3, suggesting a mutual regulation between HLA-G and other immune checkpoints which might be conducive to the immunosuppressive tumor microenvironment (TME) [215].2.