PDCD1 and melanoma: The effect of immune checkpoint inhibitors on IL-17A is not limited to γδ T cells, as human CD4+ T cells increase IL-17A after anti–PD-1 exposure (Bandaru et al., 2014) and IL-17A–producing cells in general are associated with anti–PD-1 resistance in melanoma, lung, and colorectal cancer (Gopalakrishnan et al., 2018; Li et al., 2021; Llosa et al., 2019; Peng et al., 2021).