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.

Inclusion Criteria:

• BMI 18-33 kg/m2
• Willingness to comply with the study procedure and having signed informed, written consent
• Previous diagnosis of coeliac disease according to established guidelines based on positive serology (Endomysium test, IgA-TG2 and/or IgG-DGP) (diagnosed in childhood) and a duodenal biopsy showing villous atrophy graded as Marsh 3 according to guidelines from European Society for Study of Coeliac Disease .
• Strict adherence to a gluten-free diet at least the 12 last months.

Exclusion Criteria:

• Positive serology (IgA-TG2 below upper level of normal) at screening visit
• Pregnancy or breast feeding. Fertile women must use effective contraception.
• Other inflammatory disease like uncontrolled hypothyreosis, type 1 diabetes, cardiovascular diseases, thyroid and renal disorders, inflammatory bowel diseases or any other disease that in the opinion of the responsible clinician makes the patient unsuitable for the study
• Using of immunosuppressive/steroid medications
• Wheat allergy
• Severe acute infection