The in vitro challenge of duodenal mucosa with gliadin is a useful model to reproduce the immunological features of celiac disease (CD) and allows the study of early pathogenetic events in this disease. With this model it was shown that antigens such as ICAM-1 and HLA-DR are upregulated as early as 1-2 h after gliadin challenge in patients with CD. After 24 h the lamina propria contained CD4+ T cells expressing the IL-2 receptor alpha-chain, which is a sign of activation. Intraepithelial lymphocytes increased in number and showed proliferative activity. After in vitro stimulation with gliadin, endomysial antibodies were found in the supernatant of the cultured mucosa from patients with CD following a gluten-free diet. This supported the notion that endomysial antibodies are at least in part produced locally. The model was also successfully used to identify toxic constituents of gliadin. Presently, organ culture is not commonly used for diagnostic purposes.