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%/100 μg/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.