CTLA4 and colitis: Surrogate anti-CTLA4 treatment enhances Dextran sulfate sodium (DSS)-induced colitis—a model of ulcerative colitis without perforation—in C57BL6 mice but the inflammation observed does not mimic enterocolitis described in patients.21 22 We show that long-term treatment with an Fc-effector anti-CTLA4 antibody twice weekly in Balb/c mice induces enterocolitis with similar T-cell gene signature to what has been observed in the clinic with ipilimumab and tremelimumab.28–30 Unlike clinical observations, no other irAE were observed in Fc-effector anti-CTLA4 antibody.