Laminarins and their derivatives affect dendritic cell activation and their crosstalk with T cells

Abstract

This research explores the impact of structural variations in laminarins derived from seaweed on their immunomodulatory properties. Laminarins from Laminaria digitata, L. hyperborea, and Saccharina latissima, were obtained using a two-step water extraction protocol, followed by structural characterization by FT-IR spectroscopy, 1H NMR, and MALDI-TOF MS. The laminarin backbones were confirmed as β–1,3-linked glucans with species-specific percentages of β–1,6-linkages (~10 %, ~4 %, and ~21 %, respectively). Each polymer chain consists of approximately 24 to 25 monomer units, while oligosaccharide fractions, produced using the enzyme LPHase, displayed distinct DP-ranges, degrees of β–1,6-branching and intrachain linkages. Laminarin from L. hyperborea and specific oligosaccharide fractions from L. hyperborea and S. latissima influenced cytokine secretion by dendritic cells (DCs). L. hyperborea laminarin and the fraction LhF5 (DP5–DP8) stimulated increased IL-6 and IL-10 secretion by DCs, suggesting a dual role in promoting inflammation and regulating the immune response. In contrast, LhF5, LhF4 (DP6–DP10), and S. latissima laminari-oligosaccharide fraction SlF3 (DP6–DP9) caused decreased TNFα secretion, reflecting anti-inflammatory potential. Co-culturing of treated DCs and CD4+ T-cells showed that L. hyperborea laminarin caused increased IL-17 and IL-10 secretion, whereas SlF3 caused reduced IL-12p40 and IFN-γ secretion. These findings show that DC maturation and T-cell activation are affected by laminarins of certain size-distribution and branching, implying therapeutic potential for the treatment of inflammatory diseases or vaccine enhancement.