In this study, the immune-enhancing effects of purified polysaccharides from ascidian (Halocynthia roretzi) tunic were investigated. Crude polysaccharides (AP) were isolated by enzyme extraction (neutrase, 60°C, 15 h), ethanol precipitation, and lyophilization. In addition, crude polysaccharides were further fractionated into unabsorbed fractions (APF-Ⅰ, fraction No. 11∼17) and absorbed fractions (APF-Ⅱ, fraction No. 22∼37) by DEAE-sepharose CL-6B column chromatography in order to isolate immune regulating polysaccharide. The major constituents in APF-Ⅰ and APF-Ⅱ were total sugar (66.62% and 27.03%), uronic acid (47.53% and 15.87%), hexosamine (16.62% and 46.79%), and protein (2.43% and 4.94%), respectively. APF-Ⅰ increased production of nitric oxide (NO) and cytokines, such as tumor necrosis factor-alpha (TNF-α) and interleukin (IL)-6 in a dose-dependent manner. The mRNA expression levels of inducible NO synthetase, cyclooxygenase-2, TNF-α, and IL-6 were markedly increased as determined by polymerase chain reaction analysis. The above data led us to conclude that macrophage activation of purified polysaccharides was higher than that of crude polysaccharides. The polysaccharides isolated from ascidian tunic investigated herein are useful as natural immune enhancing agents.

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