Immunomodulating effects of lichen-derived polysaccharides on monocyte-derived dendritic cells

Dendritic cells (DCs) belong to the innate immune system and play an important role as a bridge between the innate and the adaptive immune response. In this study the effects of eleven different chromatographically purified and well-characterised lichen polysaccharides on the maturation of DCs were tested by analysing the secretion of IL-12p40 and IL-10 by human monocyte-derived dendritic cells in vitro.

Eight of the polysaccharides upregulated IL-10 secretion by the DCs, as compared with unstimulated cells, with the IL-10 secretion induced by the β-glucans lichenan and Ths-2 (1) and the heteroglycans Pc-4 (2) and thamnolan (3) reaching significant levels. IL-12p40 secretion was significantly upregulated by the β-glucan lichenan and the heteroglcyans Pc-2 (2), Pc-4, thamnolan and Ths-4 (4), while the mature dendritic cells stimulated with the heteroglycan Pc-1 secreted significantly less IL-12p40 than the unstimulated cells. Proportional index (PI) was used to determine the relationship between the IL-12p40 and IL-10 secretion. The PI of all the β-glucans, i.e. lichenan, pustulan and Ths-2, and the heteroglycan thamnolan, was significantly lower than the PI observed for the unstimulated cells, which was mainly due to increased IL-10 secretion. Therefore, these polysaccharides could be considered suitable candidates in tolerance and anti-inflammatory studies, as IL-10 is one of the major cytokines involved in tolerance and anti-inflammatory responses.

Acknowledgements: Icelandic Council of Science

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