Poster Presentation International Celiac Disease Symposium 2026

Gluten-free diet initiation transiently increases gluten-specific T-cell frequency and function in coeliac disease (#366)

Olivia Moscatelli 1 , Alice Becker-Scott 1 2 , Cynthia Kanagasundaram 1 2 , Jamie Rossjohn 3 , Melinda Hardy 1 , Jason Tye-Din 1 2
  1. Walter and Eliza Hall Institute, Parkville, VIC, Australia
  2. Gastroenterology, The Royal Melbourne Hospital, Melbourne, VIC, Australia
  3. Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia

Background: Coeliac disease (CeD) drug development requires accurate immunomonitoring of gluten-specific T cell responses, but interpretation may be affected by disease activity, recent gluten exposure, and the relationship between circulating and mucosal immunity. Gluten-specific T-cell frequency and phenotype change on a gluten-free diet (GFD), but function remains uncharacterised. We assessed gluten-specific T-cell function, frequency, and phenotype in CeD blood and gut after GFD initiation.

 

Methods: Sixteen adults with CeD were studied at diagnosis and weekly for 4 weeks after commencing a GFD. A second cohort of 12 patients with active or treated CeD provided paired blood and duodenal biopsies. Gluten-specific T-cell function was assessed using an interleukin-2 (IL-2) whole blood assay (WBA); blood and biopsy-derived lamina propria mononuclear cells were stimulated with gluten peptides, and 10 cytokines were measured by electrochemiluminescence or flow cytometry. Circulating gluten-specific T cells were assessed using 27-marker spectral flow cytometry with HLA-DQ2.5:gluten tetramers.

 

Results: IL-2 WBA responses peaked 2 weeks after GFD initiation:  4.13pg/mL versus 1.58pg/mL at baseline (p=0.0028) and 2.03pg/mL at week 1 (p=0.011), then declined by week 4 in 88% of patients.  Other WBA cytokine responses were unchanged. Gluten-specific T cell frequency increased from 14.65 to 18.35/million CD4+ T cells at week 1, then fell to 8.8/million by week 4 (p=0.011), correlating with IL-2 WBA responses (r=0.61, p=0.0001). PD-1, CD38, and ICOS expression decreased by week 4. Gluten-induced IL-2 responses were lower in active than treated CeD in blood and gut. LPMC stimulation induced broader cytokine responses than WBA. Intracellular cytokine staining identified IL-2-producing gut-resident gluten-specific T cells after gluten stimulation.

 

Conclusions: GFD initiation was associated with transiently increased gluten-specific T-cell frequency and function, alongside reduced activation. Gut sampling provides complementary mechanistic insights. These findings clarify gluten-specific T-cell dynamics during GFD initiation and inform use of blood-based IL-2 WBA for longitudinal immunomonitoring.