The downstream signalling events of PD1 include augmenting PTEN expression which consequently leads to attenuation of the phosphatidylinositol 3‐kinase (PI3K)/AKT/mTOR pathway.45, 46, 47, 48 This process modulates a plethora of cellular processes including energy metabolism and plays a pivotal role in the regulation of autoimmunity, inflammation, and cancer.48, 49, 50, 51 Western blot analysis of cell lysates from CD4+ T cells cultured with 1 μmol/L indirubin revealed increased PTEN phosphorylation and decreased AKT and mTOR phosphorylation (Figure 5). This evidence concerns the gene CD4 and cancer.