Immune response of sea cucumber Apostichopus japonicus coelomocytes to several immunostimulants in vitro

The in vitro effects of β-glucan, mannan oligosaccharides (MOS), CpG oligodeoxynucleotide (CpG ODN), lactoferrin and vitamin C on the non-specific immune response of sea cucumber Apostichopus japonicus coelomocytes were studied. Coelomocytes were cultured in L-15 medium containing different concentrations of β-glucan (0, 5, 25 and 100 µg ml−1), CpG ODN (0, 0.5, 2.5 and 5 µM), MOS (0, 40, 80 and 120 µg ml−1), lactoferrin (0, 5, 25 and 100 µg ml−1) and vitamin C (0, 25, 100 and 250 µg ml−1). Coelomocytes were incubated with the above immunostimulants for 1 h, 3 h, 6 h, 12 h or 24 h except vitamin C for 3 h, 6 h, 12 h, 24 h or 48 h. Coelomocytes incubated in medium without immunostimulants were taken as controls at each incubation time. After exposure to these substances, coelomocytes were sampled and immune parameters viz., phagocytosis, superoxide anion production, superoxide dismutase (SOD) activity and total nitric oxide synthase (T-NOS) activity were determined. All immune parameters were significantly (P < 0.05) enhanced by β-glucan, MOS and CpG ODN. Lactoferrin induced significant (P < 0.05) increase in superoxide anion production and SOD activity of coelomocytes but did not affect phagocytosis and T-NOS activity. Vitamin C significantly (P < 0.05) enhanced the SOD and T-NOS activities of coelomocytes while no significant effects were observed in phagocytosis and superoxide anion production. The results suggest that β-glucan, MOS, CpG ODN, lactoferrin and vitamin C can enhance the non-specific immune response of sea cucumber in vitro.