The kinetics of IL-17 production in the lungs and plasma of mice after intratracheal infection with Klebsiella pneumoniae

Background

IL-17 is a proinflammatory cytokine predominantly produced by T cells, which is involved in the innate immune responses to various physiologic and pathophysiologic processes including bacterial host defense. The neutralisation experiments showed that the lack of IL-17 leads to decreased neutrophil emigration and systemic granulopoietic responses to pulmonary bacterial pathogens and allergens. The aim of our study was to determine the kinetics of IL-17 in plasma and lungs of animals intratracheally infected with Klebsiella pneumoniae.

Materials and methods

In our experiments we used 8–12-week-old BALB/c male mice. Mice were intratracheally inoculated with 150 CFU K. pneumoniae strain Caroli. At different time points, mice were sacrificed and the lungs and blood were aseptically removed and prepared for the cytokine determination. Cytokine determination was performed by commercial ELISA kit (Bender-Med Systems, Vienna, Austria).

Results

The IL-17 concentration in lung homogenates slightly increased in the first 2 hours of infection. Then it slightly decreased and again started to increase 24 hours after the infection. The concentration in the lungs reached the maximal value 48 hours post infection. These results are consistent with data previously published by others. On the other hand, we also found increased plasma values of IL-17. Its concentration in plasma started to increase 12 hours after the infection and reached the peak value 24 hours post infection. These results are in contrast with the results of others who reported no changes in systemic IL-17 production after the intratracheal K. pneumoniae challenge.

Conclusion

IL-17 in local host defenses against the Gram-negative pathogens is undoubtedly important for the clearance of microorganisms, but its importance in the systemic host response is still not resolved. Its maximal concentration in plasma correlates with the appearance of the bacteria in the blood after 24 hours, so we speculate that its role is also to stimulate systemic proinflammatory cytokines to combat release of bacteria and/or their toxic products into the blood system.