Type 1 diabetes (T1D) and celiac disease are both characterized by an autoimmune feature. The diseases also share the same risk genes, and thereby patients have an increased risk of developing the other disease subsequently. The pattern of peripheral T and B cell subsets and soluble immune markers (cytokines, chemokines, acute phase proteins, adipocytokines and matrix metalloproteinases) are not yet well characterized in children with a combination of the common pediatric immunological disorders, T1D and celiac disease. To better understand the complex pathophysiology, it is important to gain a deeper knowledge of alterations present in the peripheral immune profile in children with these autoimmune diseases. Pinpointing biomarkers, e.g. peripheral immune markers, can hopefully contribute to the improvement of prognosis, diagnosis, and disease management. Flow cytometry is useful for studying different immune cells, but several pre-analytical factors may affect the outcome. In order to generate reliable results, it is important to evaluate the impact of different pre-analytical factors that possibly can lead to in vitro alterations of the immune cells.

Aim: The overall aim of this thesis was to increase our knowledge of peripheral immune marker patterns in children with a combined diagnosis of T1D and celiac disease, with a focus on T and B cell subsets and soluble immune markers; by immunological methods evaluated and adapted for this purpose.

Methods: This thesis comprises methodological and cross-sectional studies. The methodological studies are based on whole blood collected from sixty blood donors to examine the impact of pre-analytical factors (anticoagulant, sample handling time, isolation and cryopreservation) that may affect the immune cells (Study I, II). The cross-sectional studies include blood samples collected from a total of 103 participants (children with T1D and/or celiac disease or no diagnosis at all). The pattern of peripheral B (Study II) and T (Study III) cell subsets were examined by flow cytometry. Nearly thirty soluble immune markers were quantified in serum by Luminex technology (Study IV).

Results: Peripheral lymphocytes were stable in whole blood samples up to 24 hours, regardless of the anticoagulant. Generally, T and B cell subsets were not affected by isolation and cryopreservation. Children with combined T1D and celiac disease had higher percentages of terminally differentiated memory T helper cells, lower percentages of effector memory T cytotoxic cells and lower expression of suppressive immune markers on regulatory T cells compared with the other study groups. Further, children with combined T1D and celiac disease had a higher percentage of memory B and lower percentages of naive B cells than children with either T1D or celiac disease. Contrary, children with single diagnoses had an inverted naive/memory B cell pattern compared to children with combined diagnoses. Several of the "classical" (cytokines, chemokines), as well as "non-classical" (acute phase proteins, adipocytokines, matrix metalloproteinases) immune markers, were lower in children with combined diagnoses compared to the other study groups.

Conclusions: Based on our results, we conclude that whole blood samples stored up to 24 hours are feasible for flow cytometric analysis of lymphocyte subsets, regardless of the type of anticoagulant. Further, isolated and cryopreserved immune cells are feasible for flow cytometric analysis of T and B cell subsets. Impairment in the T and B cells mediated immune regulation in children with combined T1D and celiac disease seems to be clearly divergent from those seen in children with exclusively one of these two autoimmune diseases. Children with combined T1D and celiac disease appear to have a suppressed immune profile, including "classical" and "non-classical" immune markers. The methodological studies provide deeper knowledge of how reliable results can be obtained in studies of peripheral immune cells, e.g., in children with autoimmune diseases. The knowledge obtained by this thesis also brings a better understanding of the pattern of peripheral immune markers in T1D and/or celiac disease. This could potentially contribute to promoting the improvement of prognosis, diagnosis, and disease management.