弓形虫对猪小肠IEL数量与细胞因子表达的影响

目的研究弓形虫对猪小肠上皮内淋巴细胞（intraepithelial lymphocytes，IEL）数量、IL-10、IFN-γ和IL-12表达水平的影响。方法对疑似患弓形虫病的家猪，经临床观察、弓形虫血清学检测、病理剖检检查和病理组织学观察诊断，确诊5头弓形虫感染猪（感染组）和5头正常猪（对照组）；采用HE染色检测小肠IEL数量和免疫组织化学方法检测IL-10、IFN-γ和IL-12的表达。结果弓形虫血清学检测阳性，且在病变组织观察到弓形虫速殖子或假包囊，确诊病猪所患为弓形虫病；与对照组比较，感染组猪的空肠、回肠IEL数量明显增加（P〈0．01），十二指肠IL-10、十二指肠和空肠IFN-γ、十二指肠和回肠IL-12的表达降低（P〈0．01），回肠IL-10和1FN-γ的表达亦降低（P〈0．05）。结论弓形虫感染猪小肠IEL数量增多，Th2型细胞因子IL-10和Th1型细胞因子IFN-γ、IL-12表达均降低，推测弓形虫调控IEL及其细胞因子，引起肠道黏膜免疫抑制，弓形虫入侵后维持肠道内环境平衡，说明IEL在抗弓形虫感染中并未起到积极作用。

Effect of Toxoplasma gondii on IEL and cytokine expression in small intestine of pigs

The purpose of this paper is to study the effect of Toxoplasrna gondii （T. gondii） on number of intraepithe- lial lymphocytes （IEL） and expression levels of IL-10, IFN-γ and IL-12 in small intestine of pigs. The disease suspected to be swine toxoplasmosis were diagnosed by the clinical observation, serological detection of T. gondii, pathological autopsy, and histopathological observation. Each segment of small intestine from 5 T. gondii infected pigs （infected group） and 5 normal pigs （control group） produced paraffin sections, then the number of IEL in small intestine were measured by HE, and the ex- pression of IL-10, IFN-γ and IL-12 in small intestine were measured by immunohistochemistry method. Serologic assays showed positive by T. gondii antigen rapid kit. There were T. gondii tachyzoite or pseudocyst in pathological tissues. There- fore, swine toxoplasmosis was diagnosed. Compared with the control group, the number of IEL were significantly higher in the jejunum and ileum of infected group （P〈0.01）. The expression of IL-10 in the duodenum, IFN-γ in the duodenum and jeju- num, and IL-12 in the duodenum and ileum of infected group reduced significantly （P〈0.01）. The expression of IL-10 and IFN-γ also reduced significantly in the ileum of infected group （P〈0.05）. It is concluded that the number of IEL were in- creased in small intestine of infected group, the expression of Th2 type cytokine IL-10 and Thl type cytokines IFN-γ, IL-12 were decreased, speculating that T. gondii regulate IEL and IEL-associated cytokines, and lead to intestinal mucosa immuno- suppression. IEL maintain the homeostasis of intestinal tract after invasion of host by T. gondii, which showed that IEL played no active role in host against T. gondii infection.