Lentinan extracted from shiitake mushrooms (Lentinus edodes) improves the non-specific immunity of sea cucumber (Apostichopus japonicus)

In this study, the subpopulations of coelomocytes of sea cucumber Apostichopus japonicus were identified with differential-interference microscope and flow cytometry (FCM). The immunostimulatory potential of crude lentinan (cLNT) from shiitake mushrooms (Lentinus edodes) on A. japonicus was then investigated both in vitro and in vivo. In vitro, the coelomocytes of A. japonicus were incubated with different concentrations of cLNT (0, 2.5, 7.5, 22.5 mg/L) for 1 h, and immuno assays were performed. Flow cytometric analysis revealed that phagocytic activity and viability of coelomocytes increased significantly with cLNT treatment. Biochemical analysis showed a significant increase in peroxidase and alkaline phosphatase activity in coelomocytes. In vivo, the immunostimulatory effect of cLNT on coelomocytes was investigated with FCM by feeding A. japonicus with cLNT-supplemented or control diet for 24 days. The phagocytic activity of coelomocytes in cLNT treatment group was significantly increased at 4, 8 and 12 days of feeding. The viability of coelomocytes was increased after 8 days of feeding. At 4, 8, 12 and 18 days of feeding, the number of small-sized and low granularity coelomocytes was reduced, while the number of large-sized and high granularity coelomocytes was increased compared to control diet. Collectively, our in vitro and in vivo studies suggest that cLNT derived from L. edodes clearly reveals immunostimulating effects on A. japonicus by increasing the viability and phagocytic activity of coelomocytes, and these findings suggest that dietary supplementation of cLNT might further improve the commercial production of sea cucumbers.