Published ahead of print on March 3, 2005, doi:10.1165/rcmb.2005-0059OC Am. J. Respir. Cell Mol. Biol., Volume 32, Number 6, June 2005, 548-552 A more recent version of this article appeared on June 1, 2005
Submitted on February 10, 2005 Lysozyme Secretion by Submucosal Glands Protects the Airway From Bacterial InfectionRana Dajani1,1 Department of Anatomy and Cell Biology, University of Iowa, Iowa City, Iowa, USA, 2 Department of Anatomy and Cell Biology, University of Iowa, Iowa City, Iowa, USA; Center for Gene Therapy, University of Iowa, Iowa City, Iowa, USA, 3 Department of Internal Medicine, University of Iowa, Iowa City, Iowa, USA, 4 Department of Internal Medicine, University of Iowa, Iowa City, Iowa, USA; Center for Gene Therapy, University of Iowa, Iowa City, Iowa, USA; Howard Hughes Medical Institute, University of Iowa, Iowa City, Iowa, USA, 5 Department of Anatomy and Cell Biology, University of Iowa, Iowa City, Iowa, USA; Department of Internal Medicine, University of Iowa, Iowa City, Iowa, USA; Center for Gene Therapy, University of Iowa, Iowa City, Iowa, USA * To whom correspondence should be addressed. E-mail: john-engelhardt{at}uiowa.edu.
Submucosal glands are abundant (~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 defence 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 the presence of glands enhanced bacterial killing in vivo and by airway secretions in vitro. Moreover, immuno-depletion studies suggested that lysozyme is a major anti-bacterial component secreted by submucosal glands. These studies provide evidence that submucosal glands are a major source of antibacterials critical for maintaining sterile airways.
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