CD4 and inflammatory bowel disease: Indeed, treatment of microbiota-reactive CD4+ T cells from healthy donors and IBD patients with IL1β, IL6, or IL23 for 1 week during stimulation with E coli, S typhimurium, L acidophilus, or B animalis (CFSE dilution assay) resulted in a 1.5- to 2-fold increase in IL17A production (Figure 7E and Supplementary Figure 6I).