When looking for intratumoral differences between patients responding or not responding to PD-1 Ab treatment, Ribas et al. also found that the frequencies of CD4+ T cells expressing CD57 (a marker generally associated with terminal differentiation and exhaustion of CD8+ T cells) was increased in non-responder TILs, suggesting that CD4+ T cell dysfunctionality associates with tumor progression [94]. Here, CD8A is linked to neoplasm.