Gluten Challenge in Celiac Disease - Which Formulation of Gluten Gives the Best Response?

The goal of this clinical trial is to evaluate the immune response to gluten in patients with celiac disease (CeD) by comparing different forms of gluten administration. The participant population includes adults diagnosed with CeD, who are adhering to a gluten-free diet (GFD). The main questions it aims to answer are: * Does liquid gluten administration elicit a higher IL-2 cytokine response compared to solid gluten administration? * What is the relationship between serum IL-2 levels and gluten peptide serum concentrations following gluten challenges? Researchers will compare the responses of two groups: participants receiving liquid gluten (shake) to those receiving solid gluten (cookie) to determine if there is a significant difference in the IL-2 response rates between the two forms. Participants will be asked to: * Undergo two gluten challenges (liquid and solid) in a randomized order with at least 4 weeks apart. * Provide blood samples before and after each challenge to measure serum IL-2 levels and gluten peptide concentrations over a period of 6 hours. * Report any symptoms experienced following each gluten challenge.