| Mycoplasma gallisepticum(MG) is the pathogen of Chronic respiratory disease of chicken(CRD) and infectious sinusitis of turkey, which can cause a lot of damage in poultry industry. Toll like receptor (TLRs) is a family of pattern recognition receptors, which can recognize the conserved molecules of pathogen-associated specifically, result in innate immune response, subsequently activate inflammatory process. TLRs is the key factor in innate immunity and acquired immunity.The deep researches in the ligands, types, biological function of TLRs enlighten a new way to study the interaction between immune receptor and pathogen. Recently, researchers made some progresses about TLRs in chicken parasitic disease and virus infection. However, the MG’s infection mechanism is still unclear, and there are no results about the interaction between TLRs and MG infection in avian. In this research, the function of NF-κB signal pathway mediated by TLR2and TLR6, which may involve in immune response after MG infection in cells and avian, were studied.This study detected the mRNA expression of TLR2, TLR6and related genes in NF-κB signal path (MyD88, NF-κB, TNFa, IL2, IL6) in DF-1cells and chicken embryos after different treatment by Q-PCR. The main results are as follows:1. The over-expression of TLR2, The over-expression of TLR6, both over-expression of TLR2and TLR6, the RNA interference of TLR6was performed in DF-1cells separately, then both control and transfected cells were detected. The results shows the NF-κB and related genes were no significant change after over-expression of TLR2and mis-expression of TLR6; however, in TLR6over-expressed and both of TLR2and TLR6overexpressed cells, the expression of MyD88, NF-κB, IL2and IL6was significantly increased compared with the control cells (P<0.05). The TNFa expression was no change. 2. After MG infection, the expression of TLR6, MyD88, NF-κB, TNFa, IL6were significantly increased compared with the uninfected cells (P<0.05), and there were no significant change of IL2, TLR2expression.3. All of the transfected cells were infected by MG. The results shows the expression of MyD88, NF-κB, IL2, IL6were significantly increased (P<0.01) in treated cells except the cells mis-expressed TLR6. The expression of TNFa was significantly increased in all treated cells.4.The11d chicken embryos were infected by MG, then lungs and tracheas were isolated respectively at12d,13d,15d and19d for Q-PCR. The Q-PCR results shows: there were no significant change of all genes in lungs at12d; The expression of TLR2and the genes in NF-κB signal pathway, except IL2and IL6, were significantly increased (P<0.05) in lungs at13d; all genes were significantly up-regulated in lungs and tracheas at15d; the expression of TLR6was significantly increased in lungs and tracheas at19d, but the others were significantly down-regulated in these tissues.These results suggested the up-regulation of TLR6can induce the genes in NF-κB signal pathway after MG infection, it is proposed that TLR6is a key signal factor in MG infected cells. There is synergy between TLR2and TLR6, but TLR2have no significantly function in innate immunity of MG; TNFa not only regulated by NF-κB signal pathway, but also have other regulating pathway, as a key factor in inflammatory process. Interestingly, at the beginning of MG infection in chicken embryos, the expression pattern of NF-κB signal pathway was similar with the results in cells; however, the results in19d embryos were contrary to the earlier stage. It suggested that the immune process may have some unknown negative feedback, which need further studies. |
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