自然调节性T细胞对脑型疟疾易感鼠和抵抗鼠感染结局的影响

目的探讨自然调节性T细胞(nTregs)在伯氏疟原虫感染过程中的活化特点及其与疾病进展的相关性。方法用伯氏疟原虫ANKA分别感染C57BL/6、BALB/c和DBA/2小鼠,计数红细胞感染率;感染前和感染后3、5、8d制备脾细胞悬液,流式细胞术检测脾细胞悬液中nTregs百分含量;ELISA和Griess方法检测脾细胞培养上清IFN-γ、IL-10和NO水平。结果C57BL/6小鼠感染后8～11d死于脑疟,BALB/c和DBA/2小鼠感染后3～4w死于贫血和过度虫体血症。3种小鼠于感染后3d,nTregs百分数达到峰值后逐渐下降,于感染后8d,C57BL/6小鼠nTregs百分数下降最为显著并明显低于正常水平,整个感染过程中,C57BL/6小鼠的nTregs百分含量显著低于BALB/c和DBA/2小鼠。3种小鼠脾细胞培养上清IFN-γ、NO和IL-10水平于感染后开始升高,感染后5d达到峰值,感染后8d与感染后5d相比,C57BL/6小鼠IFN-γ、NO水平轻微下降,IL-10水平显著下降;BALB/c和DBA/2小鼠IFN-γ、NO水平显著下降,IL-10水平轻微下降。并且C57BL/6小鼠IFN-γ、NO水平高于BALB/c和DBA/2小鼠,而IL-10水平低于BALB/c和DBA/2小鼠。3种小鼠感染后脾脏nTregs数量与IFN-γ和NO水平呈负相关,IL-10水平与感染率呈正相关。结论伯氏疟原虫感染过程中,nTregs数量的动态变化与宿主感染结局密切相关。

Effect of CD4~+ CD25~+ Foxp3~+ regulatory T cells on infection of mice susceptible or resistant to cerebral malaria

To investigate activation characteristics and correlation with disease progression of nature regulatory T cells （nTregs） during Plasmodium berghei （P. berghei） ANKA infection, C57BL/6, BALB/c and DBA/2 mice were infected by intraperitoneal injection of 1×106 P. berghei ANKA parasitized erythrocytes. Parasitemia of individual mice was monitored by microscopic examination of blood smear stained with Giemsa. Spleen cell suspension was prepared from the mice sacrificed on day 0, 3, 5, 8 post infection （p.i.）. The percentage of nTregs in spleen CD4＋T cells was analyzed by flow cytometry quantitatively. Levels of IFN-γ and IL-10 in spleen supernatants were measured by ELISA kits and the concentration of NO was detected by Griess’s method. C57BL/6 mice died from 8 to 11 days after infection when parasitemia was 15-20% with cerebral malaria （CM）, while BALB/c and DBA/2 mice survived until weeks 3 to 4 after infection and died of anemia and overwhelming parasitemia （70-80%）. The percentage of nTregs in total spleen CD4＋ T cell population started to elevate after infection and reached the peak on day 3 p.i. in CM-susceptible C57BL/6 mice or CM-resistant BALB/c and DBA/2 mice,and gradually reduced from day 5 p.i. to day 8 p.i.. On day 8 p.i., C57BL/6 mice showed the most significant decline in the percentage of nTregs. The percentage of nTregs in C57BL/6 mice was significantly lower than that in BALB/c and DBA/2 mice. IFN-γ, NO and IL-10 in cultured splenocyte supernatants began to increase after infection and reached the peak on day 5 p.i.. The results indicated that from day 5 p.i. to day 8 p.i., there were slight decline of IFN-γ and NO but significant decline of IL-10 in C57BL/6 mice. Moreover, there were significant decline of IFN-γ and NO but slight decline of IL-10 in BALB/c and DBA/2 mice. IFN-γ and NO in C57BL/6 mice were significantly higher than that in BALB/c and DBA/2 mice, while the level of IL-10 in C57BL/6 mice was lower than that in BALB/c and DBA/2 mice. The correlation analysis indicated that the percentage of nTregs was negatively associated with IFN-γ and NO, while the level of IL-10 was positively associated with parasitemia after infection. Results suggested that the dynamic changes of nTregs were closely associated with the infection outcome of host during P. berghei ANKA infection period.