We observed that C. difficile-infected IEC Stat5-deficient mice (VilCreER;Stat5f/f; STAT5ΔIEC−/−) showed more severe cecal inflammation and colitis, characterized by more colonic goblet cell depletion, more severe pseudomembranous colitis and crypt necrosis, and worse mucosal coagulative necrosis than these lesions in C. difficile-infected controls (STAT5+/+). The gene discussed is STAT5A; the disease is colitis.