CD4 and neoplasm: Fecal material from responders strengthened anti‐tumor T cell responses in GF mice, with increased CD8+ T cells rather than Foxp3+ CD4+ Tregs.[40] Vétizou found that feces from CTL‐associated antigen‐4 (CTLA‐4) antibody (Ab)‐treated metastatic melanoma patients induced the outgrowth of B. fragilis and responses to CTLA‐4 Ab in tumor‐bearing GF mice.