TNFRSF18 and neoplasm: Autologous tumor-infiltrating Tregs inhibit the proliferation and cytokine secretion of CD4+ conventional T cells, a capacity which is recovered by antibodies against Cytotoxic T-Lymphocyte-Associated protein-4 (CTLA-4) and Glucocorticoid-Induced TNFR-Related protein (GITR) but not against other immune checkpoint (ICP) molecules.