The Changes And Significance Of Duck Liver Macrophages In The Process Of Developing And Viral Infection

Liver macrophages are an important part of the mononuclear phagocyte system, and it’s the largest phagocytic cell subsets in organism. Macrophages not only a powerful nonspecific phagocytosis, it can clear the debris of liver tissue and a variety of antigenic material, but can also participate in specific immune response, anti-viral and bacterial infections and other anti-tumor immunity features. There is a big difference between birds and mammals liver, duck liver contains a lot of lipids in the early age. As the days increase, the liver lipid content decreased. This special characteristic in duck liver may cause macrophage polarization changes during development. Ducks of different ages have different tolerance to some pathogens, such as DHAV-1, Pasteurella and Newcastle disease virus. They can cause serious diseases or death of ducklings, but not pathogenic for adult ducks. For this study, through observing the duck liver macrophages polarization change during the development, provide the basis for the interpretation of these differences. The main work of this study was as follows: 1. Changes of duck liver macrophages during developmentTake 2 pieces tissue of 1, 4, 10, 21 and 35 days duck liver, one part for HE staining and immunohistochemical staining, observed and counted the positive cell of M1 and M2 polorization macrophages and statisticed the datas, another part for extracting RNA, analyzed M1 and M2 Giant macrophage gene expression changes by fluorescence quantitative PCR. The results show: as age increased, the lipid content of duck liver tissue reduced, during development liver macrophages mainly expressed as type M2, M1 macrophages except 1 day with higher levels, last low level during the development process, M2-type was always at a high level and maintained a stable number. The results show that, under normal conditions, mainly macrophage polorizantion in the liver tissue is M2 type. But in the body by external stimuli, M1 macrophages will be a substantial increase, promote inflammation. 2. The duck liver macrophage polorization changes after infected with DHAV-1In this study, 4,10,21 and 35 days ducks, respectively infection DHAV-1, 36 hours after infection executed the ducks and took liver tissue, one part for HE staining and immunohistochemical staining observes and counted the positive cell of M1 and M2 polorization macrophages and statisticed the datas, another part for extracting RNA, analyzing M1 and M2 Giant macrophage gene expression changes by fluorescence quantitative PCR. The results show: 4-day-old ducklings infected with DHAV-1 had the maximum amount of M1 macrophages in liver, M2 type was the lowest, while the elder ducks infected with reducing M1 macrophages, M2 macrophages the maximum of 10-day-old ducks after infected, and then decreased. The results showed that: different days duck infected with DHAV-1 has different liver macrophage polarization direction, with more lipid in liver tissue, there is low phagocytic activity of macrophages, thus need more to stimulate macrophage polarization to M1 type helps organizations remove the virus. Liver fat content may affect the polarization of macrophages.In addition, the study of 4-day-old ducks infected with DHAV-1 12,24,36,48,72,144 hours and 17 d after infected executed the ducks, test methods same as above. The early infection(24 hours), the organization didn’t appear obvious lesions, M1 macrophages amount was stable when the inflammation outbreak, M1 macrophage was also explosive growth, with the lesions reduced the inflammatory reaction weakened, M1 type macrophage also gradually reduced, had the similar trend with changes of virus. The amount of M2 macrophages substantially had opposite trend to M1 macrophages in the last stage of infection, accompanied by biliary epithelial hyperplasia, and gradually increase the number. The results show that, in the course of acute liver injury, M1 polarization type role for the promotion of the role of inflammation and phagocytosis of pathogens, while M2 polarization type is mainly to promote proliferation and repair of macrophages. Conclution: Similar to mammals, the main role of poultry liver M1 macrophages during acute infection is resistant to pathogens and promotes inflammation effect, M2 macrophages to inhibit inflammation and promote repair. There are a lot of lipids in duckling liver which can affect liver macrophage phagocytic capacity. It may be the the main reason of adult ducks and duckling DHAV-1 different tolerance. In early infection, liver M1 macrophages changed significantly, and promote tissue inflammation, late stage of infection, M2 macrophages increased significantly inhibit the inflammatory response, promote body repair.