Dietary tryptophan catabolite released by intratumoral Lactobacillus reuteri facilitates αPD-L1 therapy

Here, we elucidate a critical microbial-host crosstalk between probiotic-released aryl hydrocarbon receptor (AhR) agonist indole-3-aldehyde (I3A) and CD8 T cells within the tumor microenvironment that potently enhances spontaneous antitumor immunity and facilitates ICI therapy in preclinical melanoma. We used single cell RNA sequencing to phenotype CD8+ T cells within tumors of L. reuteri -treated or untreated mice. CD3+ T cells from tumors of mice treated with L. reuteri or untreated mice were isolated by magnetic selection and FACS and subjected to single cell RNA sequencing