The number of beneficial bacteria, such as Bifidobacterium and Lactobacillus, in patients with AIDS is significantly lower than that in healthy people, and the numbers of Escherichia coli, Enterococcus faecalis, and Enterococcus faecium increase; and this change is related to the levels of TNF-α and CD4+ T lymphocytes in circulation (Lu et al., 2019). The gene discussed is CD4; the disease is AIDS.