Figure 2.

The potential mechanism of gut microbiota modulating the efficacy of ICIs (1). Bacteroides thetaiotaomicron or Bacteroides fragilis enhances T cell response, treatment of anti-CTLA-4 blockade influences the abundance of immunogenic Bacteroides spp., which will in turn enhance immune response of T cells (2); Bacteroides fragilis induces Th1 immune response, promotes the maturation of dendritic cell (3); Bifidobacterium improves function of DC, results in activating of CD8+ T cell and enhancing anti-PD-L1 antitumor effect (4); The metabolite inosine of gut microbiota activates Th1 cell and increases level of IFN-γ, which can enhance antitumor effect in vivo (5); Microbiota composition affects IL-12-independent Th1 cell immune response (6); CTLA-4 blockade induces the inactivation of CTLA-4+ Treg cells, leads to activating of effector T cell and enhancing antitumor effect.