Sulfate oligosaccharide of Gracilaria lemaneiformis modulates type 1 immunity by restraining T cell activation.

Seaweeds are important "blue food" and some seaweeds have been demonstrated that have the immunoregulation activities and benefit for human health. However, which immune cell subsets are targeted and how immune processes are regulated by those seaweeds remain poorly understood. Here we identified sulfated oligosaccharide of Gracilaria lemaneiformis (GLSO) inhibits IFNγ production by T cells in ovalbumin (OVA) immunized mice and in vitro activation system of OVA-specific CD4 T cells. Furthermore, GLSO predominantly targets T cells but not dendritic cells, and regulates the late stage of expression of T cell activation and differentiation markers. Mechanistically, results of transcriptomic and proteome analysis indicate that GLSO inhibits mTOR activity, glycolysis, cell cycle and DNA replication. Thus, GLSO has an immunomodulatory function in Th1 immune responses by restraining T cell activation. Our study unravels the anti-inflammatory mechanism of GLSO and provides a new insight for industrial development of seaweeds as health food.