The Effects Of Lipopeptides On Chicken Mucosal Immunity In Respiratory Tract

Respiratory mucosa is an entrance for multiple pathogens to invade into host body.After their invasion,pathogens can cause the occurrence of many diseases,such as avian influenza,newcastle disease and infectious bronchitis,which seriously jeopardize the health of chickens and engender huge economic losses to the poultry industry.Thus,it is vital to improve the mucosal immunity in respiratory tract.Lipopeptide is a kind of bacterial metabolite that can effectively reduce surface tension.Many studies have shown their activity against pathogenic microorganism such as bacteria,fungi,mycoplasma and parasites.Unfortunately,however,so far little is known about the effects of lipopeptides on animal mucosal immunity.Hence,in our study,chickens got intranasal administration of three lipopeptides(surfactin,fengycin and iturin)respectively to detect the effects of them on both cellular immunity and humoral immunity in chicken respiratory mucosa.Next,we detected the effects of lipopeptides on chicken dendritic cells phenotypical maturation and functional maturation.To further study the effects of lipopeptides on maturation of dendritic cells,mouse dendritic cell was employed as a cell model.The aim of our study was to lay a theoretical basis for lipopeptides,especially surfactin,to become an effective mucosal immunity enhancer on chicken respiratory tract.Our study was divided into the following four parts:1 Effects of lipopeptides on cytokines expressions in chicken respiratory tract through intranasal administrationChickens were administrated with surfactin,fengycin and iturin respectively by nasal drops.The expressions of IL-10,IL-6,IL-12 and IFN-γ in nasal cavity and trachea were detected to evaluate the level of chicken mucosal cellular immunity in respiratory tract.We found that all of the three lipopeptides could increase the expressions of IL-β,IL-6,IL-12 and IFN-γ in nasal cavity and trachea with nasal drops to various extent,and surfactin played the most outstanding role among them.The results indicated that surfactin,fengycin and iturin,especially the former,could enhance the level of chicken mucosal cellular immunity in respiratory tract.2 Effects of lipopeptides on IgA expressions in chicken through intranasal administrationChickens were administrated with surfactin,fengycin and iturin respectively by nasal drops.The expressions of SIgA in nasal cavity washing fluid and trachea washing fluid,as well as IgA in serum,were detected to evaluate the level of chicken humoral immunity.We found that all of the three lipopeptides could increase the expressions of SIgA in respiratory tract mucosa and IgA in serum with nasal drops to various extent,and surfactin played the most outstanding role among them.The results indicated that surfactin,fengycin and iturin,especially the former,could enhance the level of chicken humoral immunity.3 Effects of lipopeptides on chicken dendritic cell maturationChicken bone marrow-derived dendritic cells were treated with three kinds of lipopeptides(surfactin,fengycin and iturin)respectively in vitro.The expressions of MHC Ⅱ and the number of proliferated T cells stimulated by dendritic cells were detected to evaluate the phenotypical maturity and ability to stimulate T cell proliferation of chicken dendritic cells.We found that after treated with these three lipopeptides,the expressions of MHC Ⅱ on dendritic cells were all elevated to various extent,and surfactin played the most outstanding role among them.But on the issue of the ability to stimulate T cell proliferation,only surfactin showed a promotion effect on dendritic cells.The results indicated that all of surfactin,fengycin and iturin could induce the phenotypical maturation of chicken dendritic cells,but only surfactin could induce the functional maturation of them.4 Effects of surfactin on mouse dendritic cell maturationIn the previous chapter,we found that all of surfactin,fengycin and iturin could induce the phenotypical maturation of chicken dendritic cells,but only surfactin could induce the functional maturation of them.Thus,in this chapter,mouse bone marrow-derived dendritic cells were treated with surfactin in vitro to get a further confirmation of its role in inducing dendritic cells maturation.The morphology,phenotypes,cytokines(IL-6 and TNF-a)expressions,as well as abilities of migration and stimulation of CD4+ T cell proliferation on mouse dendritic cells were detected after treated with surfactin.In addition,the contents of IκB-α in plasma and p65 in nuclear were detected to verify whether NF-κB signaling pathway was involved in this process.We found dendritic cells treated with surfactin had longer dendrites,higher expression levels of MHCII and CD40,increased secretion of IL-6 and TNF-α,as well as promoted abilities of migration and stimulation of CD4+ T cell proliferation.Besides,the expression level of κB-α in plasma was decreased and p65 in nuclear was increased.The results indicated that surfactin could induce multi-faceted maturity of mouse dendritic cells and NF-κB signaling pathway was involved in this process.