Studies on effects of IL-3 in protection against intestinal parasites in vivo

粘膜肥大细胞(MMC)在抵抗肠道类圆线虫感染中起重要作用。反复注射IL-3可诱导小鼠显著的肠道肥大细胞增多症和对沙门氏菌的保护作用。外源性IL-3对肥大细胞增殖和保护作用明显。然而，内源性IL-3如何参与保护尚不清楚。从感染沙门氏菌的小鼠肠系膜淋巴结、脾和小肠中提取总RNA，RT-PCR法检测细胞因子的mRNA表达。在感染后第7天，小鼠肠系膜淋巴结中检测到IL-3mRNA，在第11天检测到IL-3mRNA的表达，而在正常组织、感染小鼠的脾和小肠中未检测到IL-3mRNA。IL-4mRNA在正常肠系膜淋巴结中可检测到。其表达高峰在第7天，肠系膜淋巴结、脾和小肠分别为正常的7倍、11天和7天。SCF基因在正常组织中表达较好。感染后SCF基因在肠系膜淋巴结中的表达增加，而在脾和小肠中的表达降低。参与MMC体外分化和增殖的不仅有IL-E，IL-4或SCF等细胞因子也可能是沙门氏菌感染的重要细胞因子。顺便说一句，感染沙门氏菌的小鼠肠道MMC在驱虫时表现出典型的颗粒状准晶超微结构。然而，在本研究中没有检测到在人结缔组织肥大细胞中观察到的过敏性脱颗粒。在注射IL-3的小鼠中也检测到了与沙门氏菌感染相似的特征性颗粒变化。因此，注射IL-3可以诱导与沙门氏菌感染相同水平的MMC激活。

Mucosal mast cells (MMC) are important in protection against intestinal Strongyloides ratti. A repetitively IL-3 injection induces marked intestinal mastocytosis and protection against S.ratti in mice. Effects of exogenous IL-3 is clear on the mastocytosis and protection. However, how endogenous IL-3 participates in the protection is unclear. We extracted total RNA from the mesenteric lymph node, the spleen and the small intestine of mice infected with S.ratti, and detected mRNA of cytokines by RT-PCR.IL-3 mRNA was detected in the mesenteric lymph node of mice on Day 7 post infection and decreased markedly on Day 11. No IL-3 mRNA was detected in the normal tissues, and the spleen or the small intestine from infected mice by the condition used. IL-4 mRNA was detectable in the normal mesenteric lymph node. Its expression peaked on Day 7 with 7 times of normal in the mesenteric lymph node, on Day 11 in the spleen and on Day 7 in the small intestine. SCF mRNA was well detected in the normal tissues. Expression of SCF mRNA was increased by infection in the mesenteric lymph node, but decreased by infection in the spleen and the small intestine. Not only IL-E but also the other cytokines like IL-4 or SCF,which participate in the differentiation and proliferation of MMC in vitro, may be important cytokines in S.ratti-infection. By the way, intestinal MMC in mice infected with S.ratti showed characteristic paracrystalline ultrastructure of granules at the time of the worm expulsion. However, the anaphylactic degranulation which is observed in human connective tissue mast cells was not detected in this study. A similar characteristic granule change to that observed in S.ratti-infection was detected in IL-3 injected mice. Therefore, IL-3 injection can induce the same level of MMC activation as induced by S.ratti-infection.