Yoon et al. (2021) combined Bifidobacterium shortum and PD1 inhibitors in mice and found that both CD8+ T cell levels and CD8+/Treg ratios were elevated in mice, increasing the anti-tumor efficacy of mice (Yoon et al., 2021). Similarly, Montalban-Arques et al. used PD1 inhibitors along with a mixture of four Clostridium species instilled into the stomachs of mice and found that CD8+ T cells were infiltrated around the tumor tissue. As a result, this combination treatment cleared almost all tumor cells (Montalban-Arques et al., 2021) and achieved a better synergistic effect. The gene discussed is PDCD1; the disease is neoplasm.