Preliminary Study On The Mechanism Of Dendritic Cells In Anti Mycobacterium Tuberculosis Infection

ObjectiveTo establish the DC2.4 cell model of Mtb infected mice, and investigate the difference and related molecular mechanism of apoptosis induced by different virulence of Mtb. The mechanism of TRL4-NOD2 (T4N2) coordinated signal transfer targeting DC to enhance its activity and inhibitory rate of activated DC on Mtb growth was also investigated. Then analyzes the mechanism of DC in anti tuberculosis infection, which provided new clues and theoretical basis for the pathogenesis of tuberculosis and new anti tuberculosis immune therapy.MethodsThe DC2.4 cell model of Mtb infected mice was established in this study. The apoptosis of DC 2.4 cells was detected by Annexin V-FITC / PI fluorescent flow cytometry at different time points after infection, and analyze the difference of expression. The secretion of IL-6 and IL-12 in the supernatant was quantitated by ELISA with TLR4 ligand (LPS), NOD2 ligand (MDP) and TLR4-NOD2 (T4N2)double ligand in the different times. With Mtb infection DC after 4h, the cells were washed with extracellular bacteria, then stimulated with LPS, MDP and T4N2 double ligands were collected and cultured with control cracking after 24h. The cells were inoculated into the Lowenstein-Jensen culture medium and the cells were counted after 3 weeks. The number of colonies grown to determine the rate of inhibition of bacterial growth. SPSS17.0 statistical software was used to analyze the experimental data.Results1 Mycobacterium tuberculosis H37Ra standard attenuated strain and Dali clinical isolates 14-11 can induce apoptosis of DC 2.4 cells, the apoptotic rate increased significantly after infection at 6h, the rate difference between the two groups was significant (P <0.05). The apoptosis rate of DC2.4 cells induced by the isolates of Dali 14-11 was lower than that of the standard attenuated strain H37Ra cells at different time points after induction, and the apoptotic rate was significantly increased at 6h after induction.2 LPS stimulation group, MDP stimulation group and T4N2 double stimulation group were able to induce the release of cytokines IL-6 and IL-12 after DC2.4 infection, and the T4N2 coordinated signal stimulation group was compared with blank group, LPS group and MDP group, the levels of cytokines IL-6 (P <0.05)and IL-12 (P <0.05) were increased, and each time the difference was statistically significant (P <0.05).3 TLR4 ligand LPS, NOD2 ligand MDP and T4N2 ligand group were respectively stimulated with DC2.4. The growth inhibition of Mtb was inhibited by T4N2 coordinated signal activated DC2.4. Which was significantly higher than the control group and single stimulation group.Conclusion1 Different virulence of tb infected mice DC2.4 cells can rapidly induce apoptosis,the apoptosis rate may be related to the different virulence of the induced strains,the virulence of the H37Ra standard strains than the Dali clinical isolates 14-11 induced higher apoptosis rate.2 TLR4-NOD2 signal transduction can enhance the activation of DC.3 The activated DC could inhibit the growth of Mtb.