A sea urchin lectin, SUL-1, from the Toxopneustid sea urchin induces DC maturation from human monocyte and drives Th1 polarization in vitro

The sea urchin Toxopneustes pileolus belonging to the family Toxopneustidae, they have well-developed globiferous pedicellariae with pharmacologically active substances. We have purified a novel sea urchin lectin-1 (SUL-1) from the large globiferous pedicellariae of T. pileolus. Dendritic cells (DC) are professional APC and play a pivotal role in controlling immune responses. This study investigated whether SUL-1 can drive DC maturation from human immature monocyte-derived DC in vitro. Human monocytes were cultured with GM-CSF and IL-4 for 6 days followed by another 1 day in the presence of SUL-1 or LPS. DC harvested on day 7 were examined using functional assays. The expression levels of CD1a, CD80, CD83, CD86 and HLA-DR as expressed by mean fluorescence intensity (MFI) on DC differentiated from immature DC after culture with 1.0 μg/ml of SUL-1 for 1 day were enhanced and decreased endocytic activity. SUL-1-treated DC also displayed enhanced T cell stimulatory capacity in an MLR, as measured by T cell proliferation. Cell surface expression of CD80, CD83 and CD86 on SUL-1-treated DC was inhibited by anti-DC-SIGN mAb, while anti-DC-SIGN mAb had no influence on allogeneic T cell proliferation by SUL-1-treated DC. DC differentiated with SUL-1 induced the differentiation of naïve T cell towards a helper T cell type 1 (Th1) response at DC/T (1:5) cells ratio depending on IL-12 secretion. In CTL assay, the production of IFN-γ and 51Cr release on SUL-1-treated DC were more augmented than of immature DC or LPS-treated DC. SUL-1-treated DC expressed CCR7 and had a high migration to MIP-3β. Intracellular Ca2+ mobilization in SUL-1-treated DC was also induced by MIP-3β. These results suggest that SUL-1 bindings to DC-SIGN on surface of immature DC may lead to differentiate DC from immature DC. Moreover, it suggests that SUL-1 may be used on DC-based vaccines for cancer immunotherapy.