棘狀細胞 (dendritic cells; DC) 是免疫系統中一種特殊的抗原呈獻細胞 (antigen presenting cells; APC)，其於成熟 (maturation) 後會由周邊組織移動至淋巴器官中呈獻外來抗原給T淋巴球辨識，進而誘發抗原專一性免疫反應。Human erythroleukemia（HEL）細胞為一株表現功能性prostacyclin (IP) 接受器的細胞株，具有erythoid (紅血球) 、 monocytic (單核球) 及megakaryocytic (巨核細胞) 三種細胞表現型態的特性，因此常被用來研究這三種細胞型態的分化，其於PMA處理後，則會分化成類單核球/巨噬細胞 (monocyte/macrophage like cells) 及增加巨核細胞的分化。
　　過去本實驗室發現，以Prostacyclin致效劑beraprost、iloprost、carbaprostacyclin或BMY45778刺激HEL細胞時，會改變PMA誘導HEL細胞分化後的型態，產生貼壁之類棘狀細胞及抑制懸浮態之巨核細胞分化。此類棘狀細胞的型態與myeloid dendritic cells及KG-1細胞所衍生出之類棘狀細胞之型態相似。經由表面抗原分析實驗得知，經IP致效劑處理4天後的PMA誘導之類單核球/巨噬細胞，會增加棘狀細胞專一性標誌 (CD83) 及HLA-DR的表現且輔助刺激分子CD80也會表現很多。此外，在吞噬功能實驗， HEL細胞經PMA處理過後，加入IP 致效劑所誘導產生之棘狀細胞的吞噬能力比單獨投予PMA分化產生的類單核球/巨噬細胞低，且加入前列腺環素致效劑於PMA誘導之類單核球/巨噬細胞後也會增加T細胞刺激的能力，此為成熟棘狀細胞的特色。
　　此外，由DNA染色實驗及細胞表面抗原分析實驗結果得知，IP致效劑會抑制PMA誘導之細胞核內多倍體增加，以及降低巨核細胞專一性標誌CD41的表現，且加入cAMP類似物於PMA誘導之巨核細胞，同樣會造成上述之現象，因此得知IP致效劑會透過IP接受體去連結腺核苷酸鹽環化酶 (adenylyl cyclase ；AC) 進而增加細胞內cAMP的量，使得PMA誘導之巨核細胞分化受到抑制。

　　Dendritic cells (DCs) are professional antigen presenting cells (APCs) of the immune system. After maturation, DCs migrate from peripheral tissues to the lymphoid organs and are highly effective at presenting foreign antigens (Ag) to naïve T cells, thereby inducing Ag-specific immune response. Human erythroleukemia (HEL) cells is a pluripotent cell line with functional prostacyclin (IP) receptors. It is often used to study of erythroid, monocyte or megakaryocyte differentiation. It is well known that HEL cells will differentiate into monocytic/macrophage-like cells and increase megakaryocytic differentiation after phorbol ester (PMA) treatment.
　　In this study, IP agonists (beraprost, iloprost, carbaprostacyclin) and specific IP partial agonist, BMY45778 induced dendrite outgrowth with nodes and inhibited megakaryocytic differentiation from PMA-treated HEL cells. The morphology of these differentiated dendritic like cells are similar to that of myeloid dendritic cells or KG1 cells-derived dendritic like cells. Phenotypic analysis of the DC associated surface marker in PMA-treated HEL cells and beraprost stimulated PMA-treated HEL cells revealed that, IP agonists up-regulated membrane expression of DC phenotypic surface antigens CD83 and HLA-DR and expressed large amount of costimulatory molecule CD80. Moreover IP agonists also reduced the phagocytic activities of the PMA-treated HEL cells for both FITC-dextran and FITC-BSA while T cells stimulatory abilities were also enhanced after prostacyclin agonists treatment which are the characteristics of mature dendritic cells.
　　Moreover IP agonists inhibited the nuclear polyploidy and down-regulated the expression of megakaryocyte specific marker CD41 from DNA stain analysis and phenotypic analysis. Treatment of cAMP analogues also inhibited the appearance of megakaryocytic differentiation induced by PMA. Therefore, from the results, we suggest that IP agonists may through to activate IP receptor to activation of adenylyl cyclase and elevation of the intracellular cAMP level to inhibit PMA induced megakaryocytic differentiation of HEL cells.

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