CD4 and melanoma: While evidence points to SLAMF7 as an activating co-receptor in melanoma (Cachot et al., 2021), and part of a cytotoxic CD4+ T cell-associated gene signature associated with checkpoint inhibitor response (Oh et al., 2020), CD4+ T cell expression of this receptor based on scRNA-seq was absent in some tumors (Cachot et al., 2021), and this will need to be verified at the level of protein expression in individual tumor contexts.