The purpose of this study is to determine whether the immune response causing celiac disease is related to the autoimmune response causing type-1 diabetes.

Participants meeting eligibility criteria will have blood collected before and after a three-day oral gluten challenge. This blood will be tested for biomarkers associated with islet autoimmunity and gluten-specific cellular immunity.

Inclusion Criteria:

• Diagnosis of Celiac Disease by histology and serology
• For those with Type-1 Diabetes, at least one anti-islet antibody
• HLA-DQ2.5 genotype

Exclusion Criteria:

• Not following a gluten free diet for at least 12 months
• Known gluten exposure within the prior 2 months
• Treatment with systemic immune modifying biological agents (adalimumab, etanercept, infliximab, certolizumab pegol) in prior 6 months
• Treatment with systemic immunomodulatory agents in prior 30 days
• Human immunodeficiency virus infection, untreated hepatitis B virus, or hepatitis C virus infection
• Nut allergy
• Hemoglobin level below normal range
• History of angina
• Pregnant or lactating
• Severe symptoms to gluten challenge in the past
• Elevation in transglutaminase-IgA or deamidated gliadin peptide IgA or IgG greater than or equal to 50% above upper limit of normal
• Uncontrolled complications of type-1 diabetes or celiac disease which pose a risk to participation