Lysozyme secretion by submucosal glands protects the airway from bacterial infection.
Submucosal glands are abundant (approximately 1 gland/mm2) secretory structures in the tracheobronchial airways of the human lung. Because submucosal glands express antibacterial proteins, it has been proposed that they contribute to lung defense. However, this concept is challenged by the fact that mice do not have submucosal glands in their bronchial airways, yet are quite resistant to bacterial lung infection. The contribution of airway submucosal glands to host defense is also debated as a pathophysiologic component of cystic fibrosis lung disease. Here, we asked whether submucosal glands protect airways against bacterial infection. By comparing tracheal xenograft airways with and without glands, we found that the presence of glands enhanced bacterial killing in vivo and by airway secretions in vitro. Moreover, immunodepletion studies suggested that lysozyme is a major antibacterial component secreted by submucosal glands. These studies provide evidence that submucosal glands are a major source of antibacterials critical for maintaining sterile airways.
Dajani
Rana
R
Department of Anatomy and Cell Biology, Center for Gene Therapy, Howard Hughes Medical Institute, University of Iowa, 51 Newton Road, Iowa City, IA 52242-1109, USA.
Zhang
Yulong
Y
Taft
Peter J
PJ
Travis
Sue M
SM
Starner
Timothy D
TD
Olsen
Ansgar
A
Zabner
Joseph
J
Welsh
Michael J
MJ
Engelhardt
John F
JF
D000818:Animals; D001424:Bacterial Infections / Q000276:immunology*; D001980:Bronchi / Q000201:enzymology / Q000276:immunology / Q000378:metabolism; D005289:Ferrets; D009113:Muramidase / Q000378:metabolism*; D051381:Rats; D020545:Respiratory Mucosa / Q000201:enzymology* / Q000276:immunology* / Q000378:metabolism; D014132:Trachea / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism; D014183:Transplantation, Heterologous
D009113:Muramidase