台灣紫芝胞外多醣體之免疫佐劑活性與調節小鼠氣喘反應之研究

Abstract

台灣紫芝是台灣特有的靈芝，在本篇研究中，我們從台灣紫芝的液態培養中分離出胞外多醣體(PS-F2)，並利用PS-F2誘導小鼠骨髓細胞衍生之樹突細胞(BMDC)成熟並使之分泌細胞激素，結果顯示PS-F2可以增加成熟樹突細胞的表面分子CD40、CD80、CD86、MHC II的表現量，也可以增進成熟樹突細胞分泌TNF-α、IL-10、IL-12 p40和IL-6等細胞激素。此外，以PS-F2誘導的樹突細胞可以有效地呈現OVA323-339 peptide給OT II基因轉殖鼠的CD4+ T細胞，並刺激CD4+ T細胞產生細胞激素IFN-γ 和IL-17A。在動物實驗中，我們進一步的利用PS-F2作為免疫佐劑，以卵清蛋白 (OVA) 為抗原對小鼠進行免疫，發現PS-F2增加抗原專一性的免疫球蛋白，刺激Th1反應細胞激素IFN-γ生成，促進抗原專一性的脾臟細胞增生。在氣喘的動物模式中，以OVA作為抗原、氫氧化鋁作為佐劑與PS-F2混合均勻，腹腔注射至小鼠體內，結果顯示PS-F2可以有效的抑制Th2細胞激素所誘發的呼吸道發炎反應，減緩小鼠呼吸道過度反應，減少嗜酸性顆粒球滲入肺部，並降低血清中IgE的含量，在肺部沖洗液中可以明顯的發現Th1細胞激素IFN-γ增加，Th2細胞激素IL-4, IL-13, eotaxin下降。因此本篇研究指出台灣紫芝胞外多醣體PS-F2可以有效減緩過敏反應中的Th2細胞激素，改善過敏性氣喘的疾病。

Ganoderma formosanum is a unique Ganoderma species in Taiwan. In this study, we isolated the extracellular polysaccharide-fraction 2 (PS-F2) from the submerged culture of Ganoderma formosanum and demonstrated that PS-F2 induced the maturation and cytokine production in bone marrow-derived dendritic cells (BMDCs). Our results showed that PS-F2 stimulation enhanced the expression of BMDC maturation markers including CD40, CD80, CD86, and MHC II and the production of cytokines such as TNF-α, IL-10, IL-12p40, and IL-6. In addition, PS-F2-treated BMDCs presented the ovalbumin323-339 (OVA323-339) peptide to CD4+ T cells purified from OT II transgenic mice and stimulated T cells to produce IFN-γ and IL-17A. We further investigated whether PS-F2 could function as an adjuvant in vivo. We immunized mice with OVA antigen and found that PS-F2 could enhance anti-OVA immunoglobulin production and stimulate IFN-γ production. PS-F2 also induced OVA-specific splenocyte proliferation. In a murine asthmatic model, we evaluated whether PS-F2 could suppress Th2 cytokine-induced airway inflammation responses. BALB/c mice were immunized by intraperitoneally (i.p.) injection of OVA mixed with PS-F2 and aluminum hydroxide (Alum). PS-F2 administration attenuated airway hyper-responsiveness (AHR), reduced eosinophil infiltration and serum IgE levels. PS-F2 treatment also significantly enhanced IFN-γ production, increased IL-10 secretion, and reduced levels of Th2-type cytokines such as IL-4, IL-13, and eotaxin in the bronchoalveolar lavage fluid (BALF). Our results suggested that Ganoderma formosanum extracellular polysaccharide-fraction 2 might be beneficial for treating asthma disease through the suppression of Th2 response.