Study On The Uterine Immune Character Of Large White And Meishan Pigs At Early And Midgestation

In the pig production, normal embryos suffer recessive miscarriage during early and midgestation, which causes great disparity between practical productivity and potential productivity. It brings great loss to swine industry. During early and midgestation, the embryonic mortality of Meishan pig with high litter size is 16%, but that of Large White with relative low litter size is 26%. The concrete reasons keep uncertain. There exists strong immunereaction at maternal-fetal interface during pregnancy. Therefore, the present study took Large White and Meishan pig as objects to study their uterine immune character to investigate the underlying mechanism of different productivity between Large White and Meishan pig and the recessive abortion during gestation. The main researches and results were as follows:1 The uterine anatomical and histologic structure of sows at different periodsUterine horns of Large White and Meishan pig had little difference in length from the observation of gross anotomy. The fetuses of Meishan pig were smaller than that of Large White, and abundance of blood vessels in former uterus were higher than the latter, which was the same as the observation of uterine microstructure. The quantity and diameter of endometrial glands in Large White and Meishan pig had little difference at the same pregnant stage. The results demonstrated that Meishan pig may depress the development of conceptus to reduce fetal loss. The length of uterine horn and the number of endometrial glands are not the main reasons for different litter size between Large White and Meishan pig, and the primary influencing factor may be the abundance of blood vessels.2 The distribution and quantitative change of macrophages in the uterus of sows at different periodsThe Azure-Eosin-Wright staining was used to examin the distribution and quantitative change of macrophages in the uterus. The results were as follows: there were lots of macrophages distributing in the superficial connective tissue under uterine epithelium of unpregnant Large White. In comparison with unpregnant Large White, macrophages were significantly fewer in the uterus of Large White at gd26 and gd50 (P<0.01). Macrophages kept low level in both Large White and Meishan pig at gd26 and gd50. And the distribution was similar, that was, most of the macrophages located in blood vessels. In Large White, conceptus-attachment sites (AS) had significantly more macrophages than between attachment sites (BS), the differences were both significant[ gd 26 (P< 0.01); gd 50 (P<0.01)]. But there were no significant differences between AS and BS in Meishan pig at both gd26 and gd50 (P>0.05). Macrophages infiltrated at the arresting attachment sites. The results indicated that unlike many other animals, macrophages kept low level during pregnancy to maintain a low immune state, which can sustain pregnancy. Macrophages located in the blood vessels at healthy attachment sites, which may be an immunosuppressive mechanism. Once the fetus died, macrophages infiltrated in its attachment sites to clear the dead cells.3 The distribution and quantitative change of plasma cells in the uterus of sows at different periodsThe Feulgen-methylene blue staining was used to examin the distribution and quantitative change of plasma cells in the uterus. The results were as follows: plasmocytes distributed in the same place at AS and BS of Large White and Meishan pig at gd26 and gd50 (P>0.05). They all distributed in the connective tissues surrounding blood vessels and glands. The amount of plasmocytes was small, and there were no significant differences between Large White and Meishan pig, between embryonic attachment sites at gd26 or gd50. One Meishan pig was pseudopregnant after first service. When returned to estrus, it was bred again and kept pregnancy to gd26. It found that there were much more plasmocytes distributing in its uterine superficial connective tissues than other pigs. The difference was significant (P<0.01). The results showed that for one hand, the porcine uteruses (except the one mentioned above) used in the study did not suffer bacterial infections, for the other hand, plasmocytes may play a negligible role in pregnancy whereas they can be considered as an important sign to determine whether the uterus was infected or not during pregnancy.4 The distribution and expressive intension of TLR4 in uterus of sows at different periodsThe immunohistochemistry SABC staining was used to examin the distribution and expressive intension of TLR4 in uterus. The results were as follows: placenta of both Large White and Meishan pig has different expression of TLR4 at different gestation days (including foetal placenta and maternal placenta). The trophoblast of Large white and Meishan pig at gd26 expressed lower intension of TLR4 than that of gd50 [Large White (P<0.01), Meishan (0.01