| Summary: | 碩士 === 臺灣大學 === 獸醫學研究所 === 98 === Polysaccharides are polymeric carbohydrate structures, formed of repeating units (either mono- or di-saccharides) joined together by glycosidic bonds. β-glucans, are commonly found in the cell wall of bacteria and fungi, which possess immunomodulatory activity affecting both innate and adaptive immunity. Differences in the type of linkage and branching, polysaccharides can vary in solubility, molecular mass, tertiary structure, degree of branching and conformation; all these characteristics may influence their immune modulating effects.
To date, no evidence is available pertaining to the immunomodulatory activity of polysaccharides derived from animal origins. The present study aimed to investigate the effects of polysaccharide extracted from oyster (Crassostrea gigas) on T-cell reactivity. The oyster polysaccharide (OPS) used in the present study contains 97.98% glucose polymers and 1.8% proteins. The glycosidic bonds between mono-saccharides are 1,4-glucosidic linkage (71.31%), 1,3,4-glucosidic linkage (5.71%), and terminal glucose (2.83%). OPS contain about 23.82% β-glucan. The molecular weight of OPS is approximately 435 kDa. BALB/c mice were administered with OPS by gavage for three consecutive days prior to ovalbumin (OVA) sensitization. It demonstrated that OPS administration skewed the immune responses toward Th1 direction. The level of IFN-γ produced by splenocytes was elevated, whereas IL-4 was decreased. To further investigate the effect of OPS on Th1/Th2 immunobalance, a Th2-dominant murine food allergy model was employed. After two OVA sensitization, mice were repeatedly challenge a large amount OVA to induce allergic diarrhea. Results showed that OPS attenuated the occurrence of allergic diarrhea. OPS prevented the morphological change of duodenum. By toluidine blue and IHC staining, OPS administration was found to decrease the number of infiltrated and degranulated mast cells and IL-4+ cells. Results from the present study implicated that OPS may be a potential therapeutic agent for management of Th2-dominant disorders.
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