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Updated: Mar 30, 2026

Induction of Intestinal Inflammation by Adoptive Transfer of CBir1 TCR Transgenic CD4+ T Cells to Immunodeficient Mice
Published on: December 16, 2021
Anticancer immunotherapy by CTLA-4 blockade relies on the gut microbiota
Marie Vétizou1, Jonathan M Pitt1, Romain Daillère1
1Institut de Cancérologie Gustave Roussy Cancer Campus (GRCC), 114 rue Edouard Vaillant, 94805 Villejuif, France. INSERM U1015, GRCC, Villejuif, France. University of Paris Sud XI, Kremlin-Bicêtre, France.
Abstract:
Antibodies targeting CTLA-4 have been successfully used as cancer immunotherapy. We find that the antitumor effects of CTLA-4 blockade depend on distinct Bacteroides species. In mice and patients, T cell responses specific for B. thetaiotaomicron or B. fragilis were associated with the efficacy of CTLA-4 blockade. Tumors in antibiotic-treated or germ-free mice did not respond to CTLA blockade. This defect was overcome by gavage with B. fragilis, by immunization with B. fragilis polysaccharides, or by adoptive transfer of B. fragilis-specific T cells. Fecal microbial transplantation from humans to mice confirmed that treatment of melanoma patients with antibodies against CTLA-4 favored the outgrowth of B. fragilis with anticancer properties. This study reveals a key role for Bacteroidales in the immunostimulatory effects of CTLA-4 blockade.
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