Background and Aims: Inflammatory changes in the rectum of patients with celiac disease after local instillation of gluten have been reported. The aim of this study was to examine rectal mucosa after local gluten challenge in children with celiac disease and their siblings. Methods: Rectal biopsy specimens were obtained before and 6 hours after rectal challenge with a peptictryptic digest of gliadin in 33 children with treated celiac disease, 12 controls, and 19 siblings of children with celiac disease. Epithelium and lamina propria volumes were determined, and CD3+ and γδ+ lymphocytes were counted. Results: After local instillation of gliadin, a significant increment in the absolute number of intraepithelial lymphocytes was noted in patients with celiac disease but not in controls. Immunohistochemical analysis showed a significant increase in CD3+ and γδ+ cells, with the γδ/CD3 ratio remaining unchanged after challenge. A discriminant analysis allowed correct classification of 100% of patients with celiac disease and controls. The same analysis was used to classify 6 of 13 siblings as having celiac disease. The positivity was not associated with the presence of the heterodimer encoded by the DQA*0501 DQB1*0201 alleles in any of the siblings. Conclusions: All patients with celiac disease were identified by rectal gluten challenge. Approximately half of the siblings reacted to rectal instillation of gluten. The genetic background of such sensitization to gluten remains to be elucidated.
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