CTLA4 and neoplasm: A schematic showing immune interaction between T cell and APC; T cell with tumor cells is shown in Fig. 2B. Loss of CD4 + T cells and an increase in the expression of inhibitory receptors such as CD160, CD244, CTLA4, LAG-3, PD1, TIGIT, and TIM3, leads to a rapid decline in T cell effector activity.