Figure 6: Secretory IgA and oral tolerance. Intestinal feces from 4-, 6-, 10-, or 16-week-old IL-10−/− mice were collected and total sIgA (a) was measured by ELISA. 16-week-old IL-10−/− or wild-type mice received Ova either by gavage or by continuous feeding. Seven days later mice were sensitized by an intraperitoneal (i.p.) injection of 0.2 mL saline (0.9% NaCl) solution containing 10 μg OVA (Sigma, St. Louis, MO) adsorbed in 1 mg aluminum hydroxide. Fourteen days later, animals received the same dose of OVA in PBS. Control animals received 0.2 mL sterile saline. Anti-Ova IgE and IgG1 antibodies were measured by ELISA. A.U.: arbitrary units. Bars represent the mean ± SEM of 5 mice per group. Asterisks represent difference between groups (* or *** ).