Further validation of KLRG1 as a therapeutic target for human circulating cytotoxic CD4+ T cells, beyond work in murine models (37, 38) and proliferation of human CD8+ T cells in culture (11, 31), would require direct demonstration that intratumoral cytotoxic CD4+ T cells are recruited from blood, and that these clonally expanded effector cells in fact recognize tumor antigens. Here, KLRG1 is linked to neoplasm.