In addition, the conversion of dietary tryptophan to indole by Lactobacillus prevented the reduction of tumour‐associated macrophage (TAM) aryl hydrocarbon receptor (AhR) activity and aggregation of intratumoural TNF‐α+ IFN‐γ+ CD8+ T cells, attenuating the efficacy of immunotherapy.52 This evidence concerns the gene CD8A and neoplasm.