CD19 and colitis: To determine whether CD11b+ B cells have a protective function in colitis, 1×107 CD19+ B cells from the PP of day 0 WT (Itgam+/+) mice and CD11b gene-deficient (Itgam−/−) mice were purified, and AT was performed in B cell-deficient mice (Cd79a−/−) 2 days prior to the administration of DSS (Figure 2A).