Fig. 1
From: Gut microbiome modulates efficacy of immune checkpoint inhibitors
The potential mechanism of gut microbiome regulating ICIs efficacy. Firstly, the abundance of CTLA-4 on Tregs is upregulated by some bacteria and metabolites at baseline, which increases sensitivity to CTLA-4 blockade. Secondly, gut microbiota enhances the function of DCs. For example, Bifidobacterium promotes DCs maturation and decreases activation threshold, elevates recruitment and function of T cells by interaction with DCs. Thirdly, administration of Akkermansia muciniphila and Enterococcus hirae results in elevated CD4+ TCM in tumor bed. Fourthly, commensal bacteria are sensed by APCs, inducing pTh17 and Th1 differentiation, which influence tumor immunity by lymphocyte homing and recirculation. Fifthly, SCFAs are utilized by immune cells and gut epithelial cells as source of energy. Lastly, molecule mimicry theory and adjuvant effect participate in immune response