牡蠣多醣體對卵白蛋白誘發之T細胞免疫反應之作用

• Main Authors: 吳季芳, Wu, Chi-Fang
• Other Authors: 臺灣大學: 獸醫學研究所, 詹東榮
• Format: Thesis
• Language: English
• Published: 2010
• Subjects: 牡蠣;多醣體;免疫調節;T細胞;食物過敏; oyster;polysaccharide;immunomodulation;T cell;food allergy; Crassostrea gigas
• Online Access: http://ntur.lib.ntu.edu.tw/handle/246246/250601; http://ntur.lib.ntu.edu.tw/bitstream/246246/250601/1/ntu-99-R97629008-1.pdf

多醣體是由單醣或雙醣等碳水化合物藉由糖苷鍵鍵結聚合而成的結構，β-glucan是常在細菌或黴菌細胞壁中發現的多醣體，對於先天或後天免疫皆具有免疫調節作用。而多醣體依其鍵結和分枝形式的不同，其水溶性、分子量、三級結構、分枝程度及構形皆會有所不同，而這些特性都可能會其免疫調節作用。 目前為止，尚未有文獻報告有來自於關動物來源之β-glucan的免疫調節作用。本論文以萃取自牡蠣 (Crassostrea gigas) 的多醣體 (OPS) 來進行其對T細胞媒介之免疫反應作用的影響。本研究所使用之OPS其中97.98%為葡萄糖單醣聚合物，1.8%為蛋白質。單醣間的鍵結71.31%為1,4-glucosidic linkage，5.71%為1,3,4-glucosidic linkage，2.83%為terminal glucose，其中β-glucan含量約為23.82%，分子量約為435 kDa。BALB/c小鼠在以卵白蛋白免疫前以管餵方式每日投與OPS一次，連續給予三天。結果指出活體給予小鼠OPS可增加其脾臟細胞的代謝活性，而且脾臟細胞分泌的IFN-γ上升，IL-4則下降，使小鼠之免疫反應朝Th1發展。為進一步了解OPS是否具有Th1/Th2免疫調節的效果，本研究利用Th2反應為主的小鼠食物過敏模式來進行研究。小鼠經過兩次卵白蛋白免疫後再以大量卵白蛋白誘發其發生過敏性下痢的臨床症狀。結果顯示，給予小鼠OPS可降低小鼠下痢發生率，亦可降低其十二指腸黏膜組織的受損程度。藉由toluidine blue及免疫組織化學染色，發現OPS降低肥胖細胞浸潤及去顆粒化的數目，也會降低IL-4陽性細胞的數目。綜合上述，本論文的研究結果顯示，OPS為一具有免疫調節活性的天然成分，其潛力可應用於Th2相關的免疫疾病。 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.