细菌活化的浆细胞样树突状细胞在白血病自发缓解中的作用

白血病自发缓解（spontaneous remission,SR）临床罕见,多认为与严重感染等因素有关,确切机制不详.浆样树突状细胞（pDC）和髓样树突状细胞（mDC）是机体调节免疫的重要细胞,分别发挥调节初始免疫和继发免疫的关键作用.在感染诱发的白血病SR患者中观察到pDC数量明显增多并伴有IFN-α水平升高,推测细菌感染激活了pDC,在SR中发挥重要作用.本研究旨在探讨细菌能否活化pDC并观察其功能.选择健康献血员及白血病SR患者,以梯度密度离心法分离获得外周血单个核细胞（PBMNC）,应用免疫磁珠阴性选择及流式细胞阳性分选法,得到纯化的人pDC和mDC.将所得pDC分别与不同细菌共培育,利用流式细胞术及ELISA法检测共培育后细胞表面标志（CD40、CD86和HLA-DR）及细胞因子（IFN-α、IL-12、IFN-γ IL-2、IL-4、IL-10）分泌水平的变化.结果表明：金葡菌、铜绿假单胞菌能激活pDC分泌大量IFN-α并促使初始CD4＋T细胞向Th1分化.经细菌激活的pDC表面分子CD40、CD86表达明显增高,具有较强的刺激T细胞增殖能力.结论：金黄色葡萄球菌、铜绿假单胞菌细菌具有活化pDC的能力,活化的pDC能够产生大量干扰素,发挥初始免疫效应,提示细菌活化的pDC在感染诱导的白血病SR中可能发挥了重要作用.细菌活化pDC的确切机制尚需进一步研究.

Effect of Plasmacytoid Dendritic Cells Activited by Bacteria on Spontaneous Remission of Leukemia

Spontaneous remission （SR） of leukemia is a rare event in clinic,which possibly correlated with severe infection and sepsis,but its exact mechanism has not been confirmed.Plasmacytoid dendritic cells （pDC） and myeloid dendritic cells （mDC） play a key role in innate and adaptive immunity respectively.A patient with severe infection of staphylococcus aureus acquired completely spontaneous remission （SR）,moreover a increased number of pDC were observed,suggesting that bacteria-activated pDC may play an important role in SR.This study was purposed to explore if the bacteria can stimulate pDC successfully and get a functional pDC.Both pDC and mDC were isolated from freshly collected,leukocyte-rich buffy coats from healthy blood donor and leukemic patient with SR by using MACS and FACS.The pDC were cultured in RPMI 1640 medium and were stimulated with different kinds of bacteria and the expression of CD40,CD86 and HLA-DR on the cell surface was analyzed by flow cytometry.The cytokine （IFN-α,IL-12,IFN-γ,IL-2,IL-4,IL-10） production was measured by using ELISA kits.The results showed that the stimulation with staphylococcus aureus and pseudomonas aeruginosa resulted in the maturation of pDC,which secrete a large number of IFN-α and promote the differentiation of naive CD4 ＋ T cells to Th1 cells.The activated pDC expressed high level of CD40 and CD86 and showed higher T cell stimulatory capacities.It is concluded that staphylococcus aureus and pseudomonas aeruginosa can activate pDC,the activated pDC secrete high quantity of IFN-α.This result suggests that bacteria stimulated pDC may play a key role in SR of leukemia following severe infections.