肺臟是我們體內氣體交換的器官，所以肺臟經常接觸空氣中的病原菌、過敏原和汙染物質。肺臟的防禦系統必須有效快速清除這些病原菌。肺泡的先天免疫防禦機制中含有嗜中性血球、巨噬細胞、補體、肺泡表面組成物質。位在嗜中性血球和巨噬細胞..等抗原呈現細胞上的Toll-likes receptors能辨識許多不同病原菌的PAMPs。例如，Toll-like receptor 9可以辨識散佈在細菌DNA中的未甲基化CpG寡核甘酸並且導致抗原呈現細胞產生發炎性細胞素，如：TNFα。許多文獻報導肺泡表面蛋白有調節先天免疫的功能，例如增加吞噬細胞清除病原菌。並且肺泡表面蛋白D的C端醣類辨識區域被報導能和許多PAMPs結合，例如 LPS, lipoteichoic acid, peptidoglycan, plasmic DNA 和人工合成寡核甘酸。但是肺泡表面蛋白D和CpG寡核甘酸的作用關係及其免疫反應仍不清楚。我的研究目的是在探討肺泡表面蛋白D在CpG寡核甘酸引起的發炎反應中所扮演的腳色。
研究結果顯示，CpG寡核甘酸在MHS細胞中會活化P38 MAPK及JNK磷酸化，並促使MHS細胞產生TNFα。然而，CpG寡核甘酸不影響其接受器TLR9的表現量。當分別以三種MAPK抑制劑進行處理時，發現P38磷酸化抑制（SB203580）和JNK磷酸化抑制劑（SP600125）會抑制CpG寡核甘酸誘發TNFα生成。顯示CpG寡核甘酸所誘導的P38和JNK參與TNFα生成反應。此外，也發現P38和JNK的上游共同訊號IRAK-1會受到CpG寡核甘酸而活化並被降解。研究結果也顯示，自然的肺泡表面蛋白D能些微促進CpG寡核甘酸誘發的TNFα生成量，但是僅具有C端糖類辨識區域的重組肺泡表面蛋白D能明顯抑制TNFα生成量。當以不同濃度的重組肺泡表面蛋白D前處理，再給予CpG寡核甘酸刺激時，P38磷酸化與JNK磷酸化接受到重組肺泡表面蛋白D的抑制。這結果導致CpG寡核甘酸誘發的TNFα生成量受到重組肺泡表面蛋白D的抑制。此外，CpG寡核甘酸所引起的IRAK-1降解也受到重組肺泡表面蛋白D的抑制；而自然的肺泡表面蛋白D不能抑制IRAK-1降解。這些結果證實recombinant SP-D 能抑制CpG寡核甘酸引起TNFα生成，可能是經由抑制IRAK-1和JNK、P38 MAPKs的活性。

As an gas-exchange organ, lungs are inevitably exposed to air that is contaminated with pathogens, allergens and pollutants. Host-defence mechanisms within the lungs must facilitate clearance of inhaled pathogens. The innate immune components in the lung alveolar include neutrophils, alveolar macrophages, opsonins, complements and surfactant components. Toll-like receptors (TLRs) on these antigen presenting cells (eg. macrophages and neutrophils) recognize different pathogen-associate molecular patterns (PAMPs) of inhaled pathogens. For example, unmethylated CpG dinucleotides (CpG ODN) distributed in bacterial DNA are recognized by TLR9, which leads to inflammatory cytokines (eg. TNFα) production by antigen presenting cells. Many literatures reported that surfactant proteins (SPs) regulate lung innate immunity, such as enhancing pathogen clearance by phagocytes through binding to a variety of bacteria, viruses and allergens. The carbohydrate recognition domain of SP-D was reported to bind many PAMPs, such as LPS, lipoteichoic acid, peptidoglycan, plasmic DNA and synthetic oligonucleotides. But the relationship between SP-D and CpG ODN and the immune response has not been defined. The objective of my study is to determine the role of SP-D in the modulation of TNFα production by alveolar macrophages activated by CpG ODN. Results showed that CpG ODN activated the phosphorylation of P38 and JNK MAP kinases and TNFα production in MHS cells. However, CpG ODN did not affect TLR9 expression. While MHS cells pretreated with three kinds of MAPK inhibitors, the CpG ODN-induced TNFα production was inhibited by P38 inhibitor (SB203580) and JNK inhibitor (SP600125). Which showed that P38 and JNK participated in TNFα production. Besides, IRAK-1, a joint molecular of upstream of P38 and JNK signaling, was activated and degraded by CpG ODN stimulation. Data also showed that native SP-D slightly up-regulated TNFα production under the stimulation of CpG ODN. But the recombinant SP-D composed of αhelical neck region and carbohydrate recognition domains inhibited CpG ODN-induced TNFα production significantly. While MHS cells pretreated with different dose of recombinant SP-D and then challenged with CpG ODN, the phosphorylation of P38 and JNK are inhibited by recombinant SP-D. Which led to recombinant SP-D inhibited TNFα production. In addition, IRAK-1 was protected from CpG ODN-induced degradation by recombinant SPD not native SP-D. These results demonstrated that recombinant SP-D inhibited CpG ODN-induced TNFα production via inhibition on the activity of IRAK-1, JNK and P38 MAPKs.

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