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Infection and Immunity, September 2009, p. 3749-3758, Vol. 77, No. 9
0019-9567/09/$08.00+0 doi:10.1128/IAI.00454-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Jami E. Milam,1,2,
Gwo-Hsiao Chen,1,2
Galen B. Toews,1,2
Gary B. Huffnagle,2,3 and
Michal A. Olszewski1,2
Pulmonary Section, VA Ann Arbor Healthcare System, Ann Arbor, Michigan 48105,1 Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan 48109,2 Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan 481093
Received 22 April 2009/ Returned for modification 27 May 2009/ Accepted 17 June 2009
Successful pulmonary clearance of the encapsulated yeast Cryptococcus neoformans requires a T1 adaptive immune response. This response takes up to 3 weeks to fully develop. The role of the initial, innate immune response against the organism is uncertain. In this study, an established model of diphtheria toxin-mediated depletion of resident pulmonary dendritic cells (DC) and alveolar macrophages (AM) was used to assess the contribution of these cells to the initial host response against cryptococcal infection. The results demonstrate that depletion of DC and AM one day prior to infection results in rapid clinical deterioration and death of mice within 6 days postinfection; this effect was not observed in infected groups of control mice not depleted of DC and AM. Depletion did not alter the microbial burden or total leukocyte recruitment in the lung. Mortality (in mice depleted of DC and AM) was associated with increased neutrophil and B-cell accumulation accompanied by histopathologic evidence of suppurative neutrophilic bronchopneumonia, cyst formation, and alveolar damage. Collectively, these data define an important role for DC and AM in regulating the initial innate immune response following pulmonary infection with C. neoformans. These findings provide important insight into the cellular mechanisms which coordinate early host defense against an invasive fungal pathogen in the lung.
Published ahead of print on 29 June 2009.
J.J.O. and J.E.M. contributed equally to this paper.
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