PDCD1 and neoplasm: In agreement with our flow cytometry results, we identified a significant upregulation in several genes encoding for immune checkpoint inhibitory molecules (e.g. Pdcd1, Lag3, Ctla4, Icos, Tigit, Tnfrsf18) in tumor-infiltrating CD4/ALK4-KO CD4+ T cells, compared to WT CD4+ T cells (Fig. 7A).