Immunohistochemical examination exhibited that in the tumor tissues of mice co-treated with A. muciniphila and anti-PD-1 antibody, but not in those treated with the antibody alone, the ratio of CD4 to FoxP3, a definitive transcription factor for Treg [68], was increased, suggesting that the immune-stimulatory condition was induced in the tumor after the combinatory treatment. This evidence concerns the gene CD4 and neoplasm.