| Mycoplasma pneumoniae (Mp), as one kind of pathogenic mycoplasma, resides in the respiratory tract of the human beings and results in the atypical pneumonia, pharyngitis, bronchitis, tracheitis, and many other diseases and complications involved in several organs and systems outside the respiratory system. Recently, with the increase of the clinical reports concerning the inflammatory injury of multiple organs due to the infection of Mp, the immunologists and microbiologists have carried out a series of researches on the molecular and immunological mechanism involved in the inflammatory injury induced by it.The monocytes of the human beings, the research shows, recognize the lipoprotein material on the membrane of Mp by Toll like receptor 2 (TLR2) and further synthesize and secrete such proinflammatory cytokines as TNF- α , IL-1β , IL-6 and IL-12 through the activation of NF- κ B transcript. Notably, these cytokines have been proved to be able to up-regulate the expression level of mICAM-1 on several cells in the inflammatory sites, strengthening the intensity of inflammation. To investigate whether the lipoprotein of Mp can up-regulate the expression level of mICAM-1 on macrophages and epithelial cells in the respiratory tract through TLR2 and further lay the foundation for the explanation of the mechanisms involved in the inflammatory reaction resulting from the infection of Mp, The flow cytometer and fluorescence microscope was adopted to analyze the expression of mICAM-1 and TLR2 on the THP-1 cells, which were respectively treated with only Mp-LAMP, Mp-LAMP blocked by the function purified anti-human TLR2 monoclonal antibody (TL2.1) , Mp-LAMP digested with different enzymes and flow cytometer was also adopted to analyze the expression of TLR2 and mICAM-1 on the A549 cells respectively induced by Mp-LAMPs of different densities, of 25 μg ml-1 for different time and of 25 μg · ml-1 pretreated by different enzymes including their corresponding controls and to analyzethe expression of intracellular TLR2 in A549 cells stimulated by bioactive Mycoplasma pneumoniae of different MOI. The results show that all the Mp-LAMP of different densities had the significant inducing ability to upregulate the expression of mICAM-1 and TLR2 on the THP-1 cells as compared to those of untreated cells(P<0.05) and the increase of their expression levels was dependent on the density of Mp-LAMP. When the TLR2 in the THP-1 cells was blocked by the TL2.1, even the inducing ability of Mp-LAMP at 25 u g/ml to upregulate the expression of mICAM-1 and TLR2 on THP-1 cells was severely inhibited(P<0.01) and the extent of inhibition depended on the dose of TL2.1.The correlation analysis found that there existed a close relationship between the upregulation of the expression of mICAM-1 and that of TLR2 in the THP-1 cells treated by Mp-LAMP (r=0.989, P<0.01); Perplexingly, although the expression level of TLR2 on the A549 cell line is, if any, little, the expression level of mICAM-1 on the A549 cells was enhanced obviously when incubated with Mp-LAMP as compared with that of normal cells and the extent of increase depended on the density of Mp-LAMP. The expression level of mICAM-1 increased gradually from the beginning and reached its peak at the time of 16 hours then decreased slowly when incubated with Mp-LAMP of 25 u g ' ml"1. The results of enzyme digestion showed the component with inducing ability was the lipid moiety of Mp-LAMP. Exciteingly, the expression level of intracellular TLR2 in A549 cells stimulated by Mycoplasma pneumoniae for 16hs was upregulated significantly when compared with that of normal cells (PO.01). It is just the lipid moiety of Mp-LAMP, the results above suggest, that up-regulates the expression level of mICAM-1 on the THP-1 cell line through the TLR2-dependent pathway; however, the definite mechanism involved in the up-regulation of mICAM-1 on the A549 cell line induced by Mp-LAMP remains to be found. |
PDF Full Text Request