Faecal microbiota transplantation enhances efficacy of immune checkpoint inhibitors therapy against cancer

Figure 2 The potential mechanism of gut microbiome regulating anti-cytotoxic T-lymphocyte-associated protein 44 treatment efficacy. (1) Gut microbiota may induce dendritic cells maturation; (2) Gut microbiota may inhibit the M2 polarization, thereby decreasing M2 macrophages (F4/80⁺CD206⁺); (3) Gut microbiota may decrease regulatory T cells, CD4⁺ CD25⁺ Foxp3⁺ regulatory T cells, and CD4⁺/CD8⁺ T cells; (4) Gut microbiota increase CD8⁺ T cells and CD44⁺CD8⁺CD62L⁺ effector memory T cells; (5) Gut microbiota may increase inducible T cell co-stimulator expression on CD4⁺ T cells; (6) Gut microbiota may induce T helper 1 immune response; (7) Gut microbiota may reduce interleukin (IL)-6; IL-8; IL-10, and sCD25 level; and (8) Gut microbiota may increase inosine production. Altogether, all of these approaches may eventually improve anti- cytotoxic T-lymphocyte-associated protein 4 treatment efficacy. DCs: Dendritic cells; Treg: Regulatory T; T_EM: Effector memory T cells; ICOS: Inducible T cell co-stimulator; sCD25: Soluble CD25; IL: Interleukin.