Plasminogen activator inhibitor type I may contribute to transient, non-specific changes in immunity in the subacute phase of murine tuberculosis

Tuberculosis, caused by Mycobacterium (M.) tuberculosis, is a devastating infectious disease causing many deaths worldwide. Non-specific host defense mechanisms such as the coagulation and fibrinolytic system may give insight in possible new therapeutic targets. Plasminogen activator inhibitor type-1 (PAI-1), an important regulator of inflammation and fibrinolysis, might be of interest as tuberculosis patients have elevated plasma levels of PAI-1. In this study we set out to investigate the role of PAI-1 during tuberculosis in vivo. Wildtype (WT) and PAI-1 deficient (PAI-1−/−) mice were intranasally infected with M. tuberculosis H37rv and sacrificed after 2, 5 and 29 weeks. Five weeks post-infection, bacterial loads in lungs of PAI-1−/− mice were significantly higher compared to WT mice, while no differences were seen 2 and 29 weeks post-infection. At two weeks post-infection increased influx of macrophages and lymphocytes was observed. PAI-1 deficiency was associated with a reduced cytokine response in the lungs; however, upon stimulation with tuberculin purified protein derivative (PPD), PAI-1−/− splenocytes released increased levels of IFN-γ compared to WT. No clear differences were found between PAI-1−/− and WT mice at 29 weeks after infection. In conclusion, these data suggest that PAI-1 contributes to transient, non-specific changes in immunity during the early phase of murine tuberculosis.