Fig. 1

Checkpoint receptors on T cells. Figure 1 a shows negative checkpoint receptors (NCRs) on the right, and activating (costimulatory) checkpoint receptors (ACRs) of a normal T-cell on the left. The balance between the expression of these receptors, and the ligation with respective ligands, determines the functional status of the T-cell during varying physiological processes. Figure 1 b schematically shows how cancer cells may modulate T-cells, to prefentretially express and upregulate NCRs. Therefore, T-cells of cancer patients often become exhausted, anergic, and/or incapable of efficiently attacking and killing the cancer cells. This is one of the mechanisms by which the malignant cells induce tumor imune escape