IDO1 and neoplasm: Additionally, IDO inhibitors, anti‐signal transducer and activator of transcription 3 (STAT3) and anti‐IL‐6 antibodies reversed the regulatory effect of CAFs on DCs.70 Several studies have shown that IDO is highly expressed in regulatory DCs in tumour areas, which can inhibit the anti‐tumour immune response.70, 71, 72 IDO participates in the immune tolerance and suppression of tumour cells by inducing T cell anaemia and Treg cell proliferation.