Hezaveh et al. found that indole compounds, tryptophan metabolites produced by Lactobacillus, can activate the aryl hydrocarbon receptor in tumor-associated macrophages, which inhibits the intratumoral infiltration of TNFα + IFNγ + and CD8 + T cells in the pancreatic ductal adenocarcinoma and correlates with rapid disease progression and mortality.165. Here, CD8A is linked to neoplasm.