Failure to induce oral tolerance to a soluble protein in patients with inflammatory bowel disease.

BACKGROUND & AIMS: Defective suppressor/regulatory T-cell activation has been proposed as a mechanism to explain the uncontrolled inflammatory process seen in inflammatory bowel disease (IBD). Previous studies have suggested that inappropriate activation of CD4+ T cells may occur in the gastrointestinal tract in these patients. Because suppressor/regulatory T cells are thought to be one mechanism for the promotion of oral tolerance, we attempted to induce tolerance in normal controls (n = 21) and patients with either Crohn's disease (CD, n = 12) or ulcerative colitis (UC, n = 13). METHODS: Subjects were fed keyhole limpet hemocyanin (KLH) before subcutaneous immunization and booster immunization. Blood for KLH-induced T-cell proliferation and serum for anti-KLH antibody was obtained at baseline and after feeding, immunization, and booster. RESULTS: In the control group, KLH feeding (50 and 250 mg) before immunization and booster resulted in reduced KLH-specific T-cell proliferation compared with the group that was not fed KLH (P < 0.002). However, both CD and UC patients showed significantly enhanced proliferation, without tolerance induction, when compared with baseline values (P < 0.035 and 0.02, respectively). Serum antibody to KLH was present only after immunization in the control group; however, anti-KLH antibody was seen after oral administration in both the UC and CD groups. CONCLUSIONS: Taken together, these data suggest that oral antigen administration does not result in tolerance in CD and UC patients, and might actually result in active immunity. This may reflect an in vivo functional defect in mucosal suppression of immune responses in IBD.

Failure to induce oral tolerance in Crohn's and ulcerative colitis patients: possible genetic risk.

It has been proposed that defective activation of suppressor or regulatory T cells is one mechanism involved in the uncontrolled inflammatory process seen in inflammatory bowel disease (IBD). Because suppressor/regulatory T cells are thought to play a role in the promotion of oral tolerance, we attempted to induce oral tolerance in normal controls (n = 21) and patients with either Crohn's disease (CD; n = 12) or ulcerative colitis (UC; n = 13). In the first study, subjects were fed the neoantigen keyhole limpet hemocyanin (KLH) on days 1 to 5 and 11 to 15. Subcutaneous immunization with KLH was performed on day 26, with a booster immunization on day 35. Blood for KLH-induced T cell proliferation and serum for anti-KLH antibody production was obtained at baseline, on day 26 preimmunization (postfed), on day 35 after the first immunization, and again on day 42 after the second immunization. In normal individuals, KLH feeding prior to immunization and booster resulted in reduced KLH-specific T cell proliferation compared with the group that was not fed KLH. However, although on the same KLH-feeding protocol, both CD and UC patients demonstrated significantly enhanced proliferation without oral tolerance induction when compared with baseline values. These data suggest that oral tolerance induction is defective in patients with IBD. This may reflect an in vivo functional defect in mucosal suppression of immune responses in IBD. Both UC and CD appear to be multigenic disorders with evidence of familial segregation. We analyzed four multiplex Crohn's and two UC families to determine whether the defect in tolerance induction was genetically regulated. In three of the four CD families at least one unaffected family member also failed to tolerate (total 5 of 14 unaffected family members). In the UC families, the defect in tolerance segregated with disease. These data suggest a genetic defect in tolerance induction in Crohn's disease.