Study On The Functions Of Immune Cell Subsets In STZ-Induced T1DM Hyperglycemic Mice Complicated With Infection

BackgroundType I diabetes mellitus(T1DM)is an autoimmune disease,the pathogenesis of which is related to genetic,metabolic,immune and environmental factors.The metabolic disorder of T1DM patients leads to the decrease of immune function and is easy to be complicated with infection.Salmonella typhimurium is a common cause of food poisoning and gastroenteritis.The intestinal mucosal immune system acts as the first line of defense against intestinal pathogens and external antigen infection,and plays a key role in maintaining intestinal tolerance to oral antigens and intestinal symbiotic bacteria.ObjectiveInduced of hyperglycemic mice model with streptozotocin,on the basis of which Salmonella typhimurium infection was carried out to study the changes of the number of immune cells and their subsets in T1DM and its immune organs,as well as the changes of related immune function.It can increase our understanding of the molecular basis of T1DM and provide a theoretical basis for the study of the characteristics of TIDM coinfection and the theoretical system of T1DM immunotherapy.Methods1.Inject STZ to construct a T1DM hyperglycemic mice model.Analysis of immune cell subsets in spleen(SP),thymus,brain,spinal cord,Lamina propria(LP),mesenteric lymph node(MLN)and Skin-draining lymph nodes(SLN)by flow cytometry.Serum concentrations of IFN-?,IL-6,CHOL,TG,ALT and AST were measured.2.Infected T1DM hyperglycemic mice with Salmonella typhimurium to monitor changes in body weight and mortality.Analysis of immune cell subsets in SP,LP,MLN by flow cytometry.The concentration of IL-6 and IFN-y in the serum was measured.HE staining was performed on the small intestine tissue to observe pathological changes in the tissues.Results1.On the 15th day after intraperitoneal injection of STZ,the proportion of Plasmacytoid dendritic cell(pDC),Lymphoid dendritic cell(LyDC)and myeloid dendritic cell(MyDC)in T1DM hyperglycemic mice Decreased,the proportion of neutrophils and monocytes increased.The proportion of MyDC,LyDC and pDC in the thymus is also reduced.The proportion of DC and macrophage in LP decreased,and the proportion of eosinophils increased.SLN has a reduced proportion of migratory DC,resident DC,pDC,monocytes,and neutrophils.The migratory DC,resident DC,and pDC ratios of the MLN are reduced.The proportion of CD4+FoxP3+Treg of T1DM hyperglycemic mice was significantly increased.The serum levels of CHOL,TG,ALT,IFN-? and IL-6 were all increased in T1DM mice.2.After three days of infection with Salmonella typhimurium in T1DM hyperglycemic mice,the proportion of DC and NK cells in SP decreased,the ratio of neutrophils and monocytes increased,and the proportion of CD4+FoxP3'Treg decreased.The proportion of DC,monocyte and B cells in LP decreased,the proportion of neutrophils and CD4+FoxP3'Treg increased,and the proportion of CD4+FoxP3+Treg in MLN decreased.The IL-6 concentration of T1DM mice infected with Salmonella typhimurium was higher than that of normal control mice infected with Salmonella t)yphimurium.HE staining showed that there was obvious inflammatory infiltration of intestinal tissue in T1DM hyperglycemic mice infected with Salmonella typhimurium.Conclusion1.The proportion of DC subpopulations in SP,Thymus,LP,MLN and SLN of T1DM hyperglycemic mice decreased,neutrophils increased,and the body was in an inflammatory and immunosuppressed state.It is demonstrated that the loss of DC subpopulation is associated with hyperglycemia.The proportion of CD4+FoxP3+Treg in SP,Thymus,MLN and SLN in T1DM hyperglycemic mice increased,suggesting that CD4+FoxP3+Treg plays an important role in the pathogenesis of T1DM.2.The proportion of DC in SP and LP of T1DM hyperglycemic mice was significantly decreased after infection with Salmonella typhimurium.The proportion of neutrophils increased,and hyperglycemia aggravated the progress of infection.The proportion of CD4+FoxP3'Treg in SP decreased,and Helios+Treg decreased,indicating that the decrease in Treg was due to inhibition of its proliferation,which led to aggravation of systemic infection.The increase in the proportion of CD4+FoxP3+Treg in LP is due to the fact that CD103+CD11b+DC in LP stimulates antigen-specific CD4+ T cell proliferation and induces its differentiation into FoxP3+Treg.