CD8A and pancreatic ductal adenocarcinoma: Moreover, A recent study revealed that Lactobacilli can produce indole from tryptophan in foods, thereby activating the aryl hydrocarbon receptor (AhR) on tumor-associated macrophages (TAMs), leading to the reduction of interferon secreted by CD8+ T cells, and finally promoting the growth of pancreatic ductal adenocarcinoma [60].