Pneumocystis carinii induces interleukin 6 production by an alveolar epithelial cell line.
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.


CONCLUSIONS
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.
Pottratz
S T
ST
Department of Internal Medicine, Indiana University School of Medicine, Indianapolis 46202, USA.
Reese
S
S
Sheldon
J L
JL
D000818:Animals; D001422:Bacterial Adhesion; D002460:Cell Line; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism / Q000382:microbiology*; D005260:Female; D005353:Fibronectins / Q000096:biosynthesis; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis*; D011010:Pneumocystis / Q000502:physiology*; D011650:Pulmonary Alveoli / Q000166:cytology / Q000378:metabolism / Q000382:microbiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D005353:Fibronectins; D015850:Interleukin-6