Persons with coeliac disease treated with a gluten free diet will be asked to give blood for a new diagnostic blood test. In this test investigators will use multimerized HLA bound to different gliadin-peptides (tetramer) and with the help of a flow-cytometer identify (along with other relevant T-cell-markers) gluten specific T-cells. Investigators believe that these cells will be present in persons with coeliac disease regardless of gluten-intake. Investigators will compare their findings with two control groups; Persons on a gluten free diet where celiac disease is excluded (gluten sensitive group) and persons on a gluten containing diet (healthy control group). In the initial and main study investigators will look at HLA DQ2.5 individuals, which comprise >90% of all persons with coeliac disease.

Inclusion Criteria:

• HLA DQ2.5 positives in primary blinded study (other HLA-types ie DQ8 and DQ2.2 in later unblinded study)
• In gluten free group: Diagnosis must be confirmed by duodenal biopsy done after sufficient time on gluten containing diet and participant must have followed a glutenfree diet since.

Exclusion Criteria:

• Drugs that influence the immune system used last three months
• Infected with Hepatitis B, C or HIV
• Pregnant

Participants are invited through announcement in media. Eligibility is tested through HLA-test and previous workup with confirmation / exclusion of coeliac disease by reference method (duodenal biopsy).