CD4 and neoplasm: When investigating tumor samples from prostate cancer patients prior and after anti-CTLA-4 therapy, Gao et al. detected an increased expression of PD-L1 and V-domain Ig suppressor of T cell activation (VISTA), representing another inhibitory immune checkpoint molecule [42], on CD4+ T cells, CD8+ T cells, and CD68+ macrophages in posttreatment tumor tissues [43].