Research On Cellular Immunity Change In M.gilvum And M.vaccae Infected Mice

Objective: In this study, we established a mouse model for sustained non-tuberculous mycobacterial infection using Mycobacterium vaccae and Mycobacterium gilvum, and analyzed immune cells, cytokines and histopathological changes in infected mouse. This detailed characterization of non-tuberculous mycobacterial infection in C57BL/6 mice may provide a basis for further studies on immunological mechanisms with non-tuberculous mycobacterial infection.Methods: Female C57BL/6 mice were infected intraperitoneal with Mycobacterium vaccae and Mycobacterium gilvum. Groups of four mice were euthanatized at 2,7,14,21,28 and 35 days after infection.Infected organs were fixed in buffered formalin for making pathological section to observe hispathological changes, at the same time, we recorded organ weight.Through quantitative real PCR, we detected IFN-γ,TNF-α,TGF-β, NLRP3,IL-12 b and IL-10 m RNA in liver and spleen. Then CD3+, CD4+, and CD8+ T lymphocyte cells proportion of all samples were determined by flow cytometry.Results: 1、During Mycobacterium vaccae infection, liver and lungs showed obvious pathological changes. In day 7 after infection, the expression quantity of all the cytokines in the liver reached the lowest point and followed by a gradual increase until day 28. Surprisingly, IL-10, TNF-α, IL-12 b and TGF-βm RNA were only weakly induced in the spleen. The Relative frequencies of CD4+ subsets in the total CD3+ T cell population decreased at the initiation of infection, followed by a significant increase. The Relative frequencies of CD8+ subsets in the total CD3+ T cell population increased at the initiation of infection, followed by a significant decrease. 2、During Mycobacterium gilvum infection, the pathological changes of liver, spleen and lung were seen weakly. Expression of IFN-γ m RNA in liver and spleen increased gradually. In day 14 after infection, the expression of IL-12 b in liver and spleen reached the lowest point, and followed by a gradual increase. IL-10 m RNA peaked 21 days post infection in liver followed by a gradual decrease, while IL-10 m RNA peaked 14 days post the infection in spleen followed by a significant decrease. Surprisingly, NLRP3, TNF-α, and TGF-β m RNA were only weakly induced in the liver and spleen. The Relative frequencies of CD4+ subsets in the total CD3+ T cell population decreased at the initiation of infection, followed by a significant increase.The Relative frequencies of CD8+ subsets in the total CD3+ T cell population increased at the initiation of infection, followed by a significant decrease.Conclusions: 1、The inflammatory responses in liver were stronger than in spleen during Mycobacterium vaccae infection, pathological changes in the liver was significantly higher than that in spleen. 2、The expression of IFN-γ,IL-12 b and IL-10 in liver and spleen played more significant role during M.gilvum infection, but NLRP3, TNF-α and TGF-β were only weakly induced in the spleen and liver. 3、CD4+ and CD8+ T lymphocytes may have played an important role in non-tuberculous mycobacterial infection.