Data from a new mouse model support the long-standing hypothesis that celiac disease begins within the gut wall, as transglutaminase 2 (TG2)-specific B cells in Peyer’s patches sample perfused recombinant TG2 from the gut lumen and help ignite the autoimmune cascade that defines the disorder, according to investigators.

The model may help advance therapeutic development in celiac disease, including improved TG2 inhibitors and strategies to deplete autoreactive B cells, lead author Marie Fleur du Pré, PhD, of the University of Oslo, Norway, and colleagues, reported.

“An important unresolved question is where in the body the pathogenic interactions between TG2, gluten, and the T and B cells occur,” the investigators wrote in Gastroenterology. “We proposed that pathogenic TG2-gluten enzyme-substrate complexes could be generated in the gut lumen and initiate an anti-TG2 antibody response in gut-associated lymphoid tissues (GALT).”

To test this hypothesis, the investigators established a humanized mouse model designed to replicate the key genetic and cellular features of the disease. Mice expressing HLA-DQ2.5, the major susceptibility allele, received adoptive transfers of TG2-specific B cells and gluten-specific CD4 ⁺ T cells. Oral immunization with a chimeric “Troybody” antigen, a TG2-reactive antibody carrying a gluten T-cell epitope, was administered with cholera toxin to drive mucosal activation.

The model successfully generated TG2-directed immune responses, allowing the investigators to track where and how those responses emerged.

Subsequent analyses confirmed a TG2-specific mucosal response. Serum contained TG2-specific immunoglobulin A (IgA) and IgG, stool contained TG2-specific IgA, and TG2-specific IgA plasma cells were detected in the lamina propria of the small intestine, closely reflecting the autoimmune profile seen in untreated celiac disease.

To pinpoint the site of early B- and T-cell collaboration, the investigators examined Peyer’s patches and mesenteric lymph nodes. In both compartments, transferred TG2-specific B cells expanded and showed a germinal center phenotype, while gluten-specific CD4+ T cells exhibited a follicular helper profile, consistent with antigen-driven cooperation within the GALT.

The most direct test evaluated whether B cells in Peyer’s patches can sample TG2 from the gut lumen. Using a ligated-loop preparation, fluorescently labeled recombinant TG2 was infused into the intestinal lumen overlying Peyer’s patches. Confocal microscopy revealed uptake of the labeled enzyme by TG2-specific B cells in the subepithelial dome, but not by non-TG2-specific cells or in control loops. These findings show that luminal TG2 can be directly captured by Peyer’s patch B cells, linking epithelial shedding, gluten exposure, and autoimmune activation.

Taken together, the results support a model in which luminal TG2 binds dietary gluten and can be sampled by TG2-specific B cells in Peyer’s patches. These B cells then present gluten epitopes to T cells and initiate the anti-TG2 antibody response that defines celiac disease.

The investigators noted that their experiments did not directly demonstrate uptake of endogenous TG2-gluten complexes, nor did they assess contributions from other antigen-presenting cells such as dendritic cells.

Even so, these findings “offer a valuable preclinical tool to dissect these pathogenic T-cell–B-cell interactions,” du Pré and colleagues concluded. “We anticipate that further development of the model we describe here will provide a valuable foundation for the development of improved TG2 inhibitors and novel therapeutic strategies for celiac disease.”

Revolutionary Potential

Robert Anderson, MB ChB, PhD, principal science and innovation advisor for the Celiac Disease Foundation and senior researcher at the Wesley Research Institute in Brisbane, Australia, said the findings help explain how gluten reaches the immune system so quickly, and why that insight should reshape both treatment and diagnosis of celiac disease.

“It’s always been a bit of a mystery as to how the gluten penetrates the epithelial membrane and gets access to the immune system,” Anderson told Medscape Medical News, noting that patients with celiac disease can feel ill within about half an hour of gluten exposure.

These new findings show that T cells “can be activated very quickly,” he said, challenging the long-held assumption that such immune responses require at least 24 hours.

This mechanism undermines the “leaky gut” theory, Anderson said, since a general increase in permeability is unnecessary to explain disease onset. “Leaky-gut drugs are probably not going to be effective in the treatment of celiac disease,” he said.

Instead, Anderson pointed to TG2 as a more relevant therapeutic target, noting that recent trial data evaluating a non-absorbable TG2 inhibitor now make clearer sense: the agent blocks immune activation in the gut lumen before gluten even crosses the epithelial barrier.

Anderson predicted that TG2 inhibitors could become a safe, affordable first-line option to complement a gluten-free diet. In addition, the improved understanding of the role of T cells could reduce diagnostic reliance on gut biopsies.

“That’s looking at the effect, not the cause of celiac disease,” Anderson said. As co-founder and director of Novoviah, he is developing blood tests that detect gluten-reactive T cells even in patients on a gluten-free diet, potentially reducing or eliminating the need for prolonged gluten challenges.

“We actually may have the tools available in the next couple of years,” he said, predicting that such tests, alongside TG2-targeted drugs, could soon “revolutionize this field.”

The study was supported the Research Council of Norway and the National Institutes of Health. The investigators disclosed no conflicts of interest. Anderson is founder and director of Novoviah Pharmaceuticals, in Brisbane City, Australia.