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Pneumocystis carinii induces interleukin 6 production by an alveolar epithelial cell line
S T Pottratz1, S Reese, J L Sheldon
1Department of Internal Medicine, Indiana University School of Medicine, Indianapolis 46202, USA.
Background:
Pneumocystis carinii (PC) infection often results in severe pneumonia in immunocompromised patients. Attachment of PC organisms to alveolar epithelial cells is a hallmark of PC pneumonia; however, few studies have investigated the response of alveolar epithelial cells to PC infection.
Methods:
Interleukin 6 (IL-6) is a multifunctional cytokine that is produced by alveolar epithelial cells in response to a variety of stimuli. Our investigation was undertaken to determine whether PC organisms induce production of IL-6 by alveolar epithelial cells and to determine the effect of IL-6 on PC attachment.
Results:
Incubation of the human alveolar epithelial cell line, A549, with PC organisms resulted in a significant increase in IL-6 secreted into the cell culture media. Time-course studies showed that IL-6 production was detected as soon as 2 h after addition of PC and continued up to 48 h of exposure. Further studies demonstrated that preincubation of A549 cells with IL-6 resulted in a concentration-dependent increase in both A549 cell production of fibronectin and PC attachment.
Conclusion:
Thus, PC attachment to an alveolar epithelial cell line results in epithelial cell production of IL-6, which can act to further increase PC attachment. This may provide an important mechanism whereby PC organisms directly affect the host response to PC infection.