However, as noted above, many other conventional immune checkpoints such as TIGIT, TNFRSF4 (OX40 receptor/CD134), TNFRSF9 (4-1BB/CD137), and TNFRSF18 (GITR) are not universally overexpressed in cytotoxic CD4+ T cells from cancer patients (Oh et al., 2020). Here, TNFRSF18 is linked to cancer.