Effect On The Rat Mhc Ib And Nk Receptor At Maternal-fetal Interface Infected By Toxoplasma Gondii During Early Pregnancy

Toxoplasm(T) gondii, which widely parasitizes both in human and animals. It is one of the main pathogen that can cause human TORCH syndrome. Infection of T. gondii during human pregnancy may result in abnormal pregnancies, such as abortion, premature labor, and even still birth. And fetuses infected in early developmental stages can be severely affected. As we know, the keeping of normal pregnancy mainly based on the local immune balance at fetal-maternal interface. It is still not fully uderstand about the mechanisms of this immune balance but more and more studies have demonstrated that MHC molecules and uterine NK cells receptors expressed at fetal-maternal interface are crucial factors in maintaining normal pregnancy.It has been demonstrated that HLA-G expressed on human trophoblast cells can inhibit effectively maternal decidual natural killer(NK) cells immune reaction against fetus binding inhibitory receptors expressed on decidual NK cells. So they play a key role during normal pregnancy. In our lab it has been found that T. gondii infection could induce the HLA-G expression level decreased on human trophoblast cells and made inhibitory receptors KIR2DL4 and ILT-2 on decidual NK cells of early pregnancy lower both in mRNA and protein level(in press). So this study focuses on exploring the molecular mechanisms of abnormal pregnancy caused by T. gondii infection during early pregnancy in vivo using established rat model.RT.BM1 and RT1-E were important MHC Ib molecules in rat placenta, which bear much resemblance to human HLA-G and HLA-E. So they might play important roles in regulating decidual NK cells function during rat normal pregnancy through binding the receptors NKG2A, NKG2C and Ly49s3 expressed on decidual NK cells. But so far, the expression rules of these molecules during normal pregnancy was still not fully understand and the relationship between those molecules and abnormal pregnancy induced by infected with T. gondii also still need further explored.Therefore, our research focused on examining the expression of RT.BM1, RT1-E in rat placenta and NKG2A, NKG2C, Ly49s3 in rat uterus of nomal group and infected group for investigating the expression rules of these molecules during normal pregnancy and the relationship between these molecules and abnormal pregnancy caused by T. gondii infection during the early pregnancy. The result of these studies will be usefull for further understanding immune mechanism of abnormal pregnancy caused by T. gondii infection.48 pregnant Wistar rats were randomly divided into normal group and infection group equally. Infection group was intraperitoneally injected with 1×105 of living T. gondii RH Strian Tachyzoites on the 5th day of gestation, the normal control group without any injection. Six rats were euthanized at days 9, 13, 15 and 17 of pregnancy respectively. Placentas and uteri were collected and the expression of RT.BM1 and RT1-E of placenta and NKG2A, NKG2C, Ly49s3 of uteri were analyzed by real-time quantitative PCR.It was demonstrated that①the number of living embryos of normal group were 204, and the number of death embryos and absorption embryos were 3,then the stillborn rate was 1.4%. But the infection group was 133, 27, 16.9% respectively and the stillborn rate was significantly higher than that of normal group(P<0.05).②There are no significant difference of RT.BM1 mRNA expression level among 9th, 13th day and 15th day(P>0.05). But it significantly increased at 17th day (P<0.01). The relative expression level of RT.BM1 mRNA in the infection group was significantly higher than that of the normal group at 9th, 13th, 15th day (P<0.01).③The average mRNA expression of RT1-E of normal group was lowest at 9th day (P<0.05). The average mRNA expression of RT1-E of infected group were significantly higher than that of the normal group at 9th, 13th, 15th (P<0.01,P<0.05,P<0.01).④The relative expression of NKG2A mRNA is highest at 13th day(P<0.05)and there is no difference among expression at other time points. It is up regulated remarkably in infected group at early pregnancy and mid-pregnancy(D9, D13, D15)(P<0.05),(P<0.01)(,P<0.01).⑤The expression of NKG2C mRNA at 9th, 13th are significantly higher than those at 15th, 17th(P<0.01) and significantly increase when infected by T. gondii(P<0.01,P<0.05,P<0.05).⑥Expression of Ly49s3 mRNA is also highest at 13th day(P<0.05)and increase sharply at every time point(P<0.01)after infected by T. gondii.It is concluded that the rat model was successfully established. The normal expression of RT.BM1 and RT1-E in rat placenta and NKG2A, NKG2C, Ly49s3 of rat uterus NK cells has very important role to keep the normal pregnancy. T. gondii infection during the early pregnancy can change of expression level of above molecules and break the normal immune balance on the maternal-fetal interface. This may be one of the main molecular mechanisms of abnormal pregnancy induced by T. gondii infection during the early pregnancy.