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2016 ; 9
(3
): 718-29
Nephropedia Template TP
Cai S
; Batra S
; Langohr I
; Iwakura Y
; Jeyaseelan S
Mucosal Immunol
2016[May]; 9
(3
): 718-29
PMID26349661
show ga
The role of interleukin-17A (IL-17A) in host defense against Legionella
pneumophila remains elusive. To address this issue, we used Il17a(-/-),
Il17f(-/-), and Il17a/Il17f(-/-) mice on a C57Bl/6 (non-permissive) background
and IL-17 neutralizing Abs in mice on an A/J (permissive) background. Higher
bacterial (L. pneumophila) counts in the lung and blood along with reduced
neutrophil recruitment were detected in Il17a(-/-), but not Il17f(-/-), mice. We
found that neutrophils produce IL-17A homodimer (IL-17A) during L. pneumophila
infection, and hematopoietic cell-derived IL-17A is known to be important for
bacterial clearance. Thus, intratracheal administration of wild-type neutrophils
or recombinant IL-17A restored bacterial clearance and neutrophil recruitment in
Il17a(-/-) mice. Furthermore, neutrophil-depleted Rag2(-/-) and Rag2/Il-2r?(-/-)
mice exhibited increased bacterial burden, reduced neutrophil influx and IL-17A
production in the lung. Recombinant IFN-? administration in Il17a(-/-) mice
augmented bacterial elimination, whereas IL-17A administration in Ifn?(-/-) mice
did not augment bacterial clearance. IFN-? is produced by T cells, but not
neutrophils or macrophages, suggesting that neutrophil-derived IL-17A induces
IFN-? in a paracrine fashion. Human pneumonic lungs and human neutrophils
challenged with L. pneumophila exhibited increased numbers of IL-17A producing
cells. These findings display a novel function of neutrophil-derived IL-17A in
antibacterial defense via the induction of IFN-? in a paracrine manner.