Vétizou et al.248 found Bacteroides species, particularly B. thetaiotaomicron and B. fragilis, to have a role in improving the therapeutic efficacy of anti-CTLA-4 ICIs, for the treatment of melanoma and colon cancer in mice.248 On the other hand, the immunosuppressive effect of B. fragilis has been described earlier (section Microbial Toxins). The gene discussed is CTLA4; the disease is melanoma.