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P030. Interaction between glycans and the immune system: Do glycans play a role in Crohn's disease pathogenesis?

L. Baram1,5, L. Spektor1,5, H. Elad1,5, Z. Halpern2,5, H. Guzner-Gur3,5, I. Dotan4,5

1The Research Center for Digestive Tract and Liver Diseases, Israel; 2Tel Aviv Sourasky Medical Center, Tel Aviv, Israel; 3Internal Medicine Department B, Israel; 4Tel Aviv Sourasky Medical Center, IBD Center, Department of Gastroenterology and Liver Diseases, Tel Aviv, Israel; 5The Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel

Background: Crohn's disease (CD) is characterized by loss of tolerance towards intestinal microorganisms, reflected by serologic responses: ASCA (anti Saccharomyces cerevisiae antibodies), ALCA (anti laminaribioside carbohydrate antibodies) and ACCA (anti chitobioside carbohydrate antibodies), directed against the glycans mannan, laminarin and chitosan, respectively. Glycans are major constituents of fungal cell walls. However, their role in CD immunopathogenesis is yet unclear.

We aimed to explore glycan-induced immune responses in humans and their correlation with intestinal inflammation.

Methods: Peripheral blood mononuclear cells (PBMCs) isolated from CD and normal control patients were stimulated by glycans or heat killed (HK) yeasts. Intestinal epithelial cells (IECs) were generated from surgical specimens and IECs cell lines. Glycan receptor [dectin‑1 and mannose receptor (MR)] expression was assessed using flow cytometry and fluorescent microscopy; cytokine secretion in supernatant following glycan stimulation was assessed using ELISA and serologic status by the IBDX ELISA kit (Glycominds, Ltd, Israel).

Results: The glycans mannan and laminarin induced significantly higher pro-inflammatory cytokine secretion by CD vs. normal PBMCs: TNF‑α [laminarin: 408 vs. 212 pg/ml p = 0.014]; IL‑1 β [laminarin: 284 vs. 56 pg/ml, p = 0.013, mannan: 701 vs. 279 pg/ml p = 0.025], IL‑6 [laminarin: 2903 vs. 1075 pg/ml, p = 0.007, mannan: 5645 vs. 2856 pg/ml, p = 0.021]. A 89% and 77% inhibition of glycan-induced TNF‑α secretion was observed using spleen tyrosin kinase inhibitor. HK C. albicans induced higher TNF‑α secretion [5876 vs. 2470 pg/ml, p = 0.05], while HK S. cerevisiae induced lower IL‑10 secretion [56 vs. 253 pg/ml, p = 0.007] by CD vs. normal PBMCs. Dectin‑1 and MR were expressed by 60±20% and 80±9% of CD14+ cells, respectively, as well as IECs. ASCA status and MR expression by CD monocytes correlated (r = 0.59, p = 0.03), while no correlation between ALCA status and Dectin‑1 was observed (r = 0.28, p = 0.26).

Conclusions: Glycans are capable of stimulating immune responses, in a Syk-dependent way. The glycan receptors dectin‑1 and MR are mainly expressed by monocytes. CD is characterized by hyperesponsiveness towards yeast-characterizing glycans, reflected by increased pro-inflammatory cytokine secretion. Glycan receptor expression and serologic status correlate. These results may point out the link connecting glycans expressed by microorganisms and intestinal innate and adaptive inflammatory responses.