Please use this identifier to cite or link to this item: http://hdl.handle.net/1946/8087
Introduction: The coccoid blue-green algae Leptolyngbya erebi var. thermalis (BLK) is a dominating member of the microbial ecosystem of the Blue Lagoon geothermal seawater. Beneficial effects of regular bathing on psoriasis, a T cell mediated disease, were discovered shortly after its formation. However, very little is known about the biological activities providing the beneficial effects.
Objective: To determine whether crude samples of exopolysaccarides produced by BLK affect stimulation of human dendritic cells (DCs) and their ability to activate allogeneic CD4+ T cells.
Methods: Human-monocyte derived DCs were matured in the absence or presence of crude samples of BLK exopolysaccharides. The effects of the exopolysaccharides were determined by measuring the secretion of IL-10 and IL-12p40 by ELISA and the expression of surface molecules by flow cytometry. Subsequently, DCs matured in the presence or absence of the test sample BLK0 were co-cultured with allogeneic CD4+ T cells and their effects on activation of the T cells analyzed by measuring expression of various intracellular and surface molecules by flow cytometry, secretion of IFN-γ, IL-10, IL-17 and IL-22 by ELISA and proliferation by H3-thymidine uptake.
Results: DCs matured with either BLK0 or BLK0.5 at 100 μg/mL secreted increased levels of IL-10 compared to untreated DCs. Co-culturing allogeneic CD4+ T cells with DCs that had been matured in the presence of BLK0 increased IL-10 secretion compared to control. There was a tendency towards increased frequency of Foxp3+ and IL-10+ T cells and decreased frequency of PD1+ T cells when co-cultured with DCs matured with BLK0.
Discussion and conclusions: While these findings need to be repeated in a larger cohort the study showed that the exopolysaccharides secreted by BLK stimulate DCs to produce vast amounts of the immunosuppressive cytokine IL-10. In co-culture, these DCs induce allogeneic CD4+ T cells to secrete IL-10, and possibly upregulate Foxp3 and reduce PD1 expression, a phenotype resembling Tregs.