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Interplay between receptors of innate immunity and vitamin D3 for the induction of alloreactions through antigen-presenting cells

Subject Area General and Visceral Surgery
Term from 2010 to 2017
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 160225957
 
Final Report Year 2018

Final Report Abstract

The main findings of this project are that SNPs of NOD2 seem to affect monocyte differentiation as the blood cell composition is changed in healthy donors with NOD2 SNP12 & SNP13 mutations. These healthy donors show lower levels of monocytes but these monocytes have a higher expression level of CD16. CD14+/CD16+ monocytes are discussed as “inflammatory monocyte” population and could partially explain the association of NOD2 SNPs with inflammatory diseases such as Crohn’s disease and GvHD. Furthermore healthy donors with NOD2 SNP12/13 had lower numbers of myeloid DCs. Based on these data we speculated that monocyte differentiation may be disturbed as a consequence of NOD2 mutations. Accordingly we found differences in the in vitro differentiation of monocytes into DCs. Interestingly, inhibition of DC differentiation regarding surface markers was detected only in a special fast protocol with mononuclear cells indicating that NOD2/CARD15 expression in human lymphocytes is in part responsible for the NOD2-mediated immune regulation. Problematic is the frequency of NOD2 SNPs in healthy donors. It took a long time to get a reasonable number of mutated donors and we still need to confirm the data with more donors. We tried to circumvent this problem by using a mouse model, however, could not reproduce the findings in mice, most likely based on the fact that murine monocytes are characterized by other markers and do not express CD16. In the second part of the project we analysed the interplay between NOD2 and vitamin D3. We investigated the impact of NOD2 SNPs on vitamin D levels in patients undergoing stem cell transplantation; here we did not find differences indicating that NOD2 is not involved in vitamin D3 metabolism in patients. However, analyses of gut biopsies showed that the expression of the vitamin D receptor VDR and the vitamin D3 metabolizing enzyme CYP27A1 seem to be related to GvHD development and TRM. We suggest that these findings may be linked to our in vitro data showing that the active metabolite of vitamin D3 can induce FOXP3 expression in vitro and may support Treg differentiation in the gut.

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