Sulfated polysaccharides: Immunomodulation and signaling mechanisms

Polysaccharides are natural macromolecular polymers that are widely distributed in various food resources and have attracted much attention due to their significant bioactivities. Sulfated polysaccharides refer to polysaccharides containing sulfate groups on sugar units. A large number of studies have characterized and evaluated the biological relevance of sulfated polysaccharides, which shows great potential in terms of immunological activity. Through a critical analysis of current research literature regarding sulfated polysaccharides, this review will give an overview of the immunomodulatory properties and signaling mechanisms of natural or modified sulfated polysaccharides. The effects of the degree of substitution (DS), molecular weight, and structure on immunomodulatory effects will also be discussed. The mechanisms by which sulfated polysaccharides exert their immunological activity is mainly due to the regulation of macrophage function, natural killer cells, and T/B lymphocytes, together with the stimulation of the immune responses of lymphocytes and the activation of the complement system. The immunological activity of sulfated polysaccharides depends not only on the source of the polysaccharide but also on structural characteristics, such as molecular weight and DS. Studies on the mechanisms of immune function have shown that the action of sulfated polysaccharides is a complex process that may be regulated by one or more pathways. Nevertheless, the link between the immunological mechanisms and structure of sulfated polysaccharides requires further exploration.