Structural effects of sulfated polysaccharides from Codium fragile on NK cell activation and cytotoxicity

The effects of sulfates and proteins of the sulfated polysaccharide-F₂ (SP-F₂) from Codium fragile on the NK cell activation and cytotoxicity were systematically investigated. The SP-F₂ treatment significantly increased both NK cell proliferation (129%/100μg/mL) and their potent cytotoxic effects against HeLa cells (46%). The SP-F₂ treatment appeared to enhance NK cell activation through the expression of the activating receptor, NKp30; the secretion of the cytokine, IFN-γ and the release of the lysing proteins, perforin and granzyme-B. However, the treatment of the SP-F₂ derivatives, deproteinated and desulfated-F₂ (DP-F₂ and DS-F₂), markedly lowered the mRNA expression levels of IFN-γ, granzyme-B, NKp30 and FasL, suggesting that the proteins and sulfates were essential for the interaction between the SP-F₂ and NK cells. The antibody neutralization test revealed that CR3 might be a critical receptor involved in SP-F₂ NK cell activation.