The NKG2D-Activating Receptor Mediates Pulmonary Clearance ofPseudomonas aeruginosa

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Abstract
The NKG2D-activating receptor is expressed on cytotoxic lymphocytes and interacts with ligands expressed on the surface of cells stressed by pathogenic and nonpathogenic stimuli. In this study, we investigated the physiologic importance of NKG2D receptor-ligand interactions in response to acute pulmonaryPseudomonas aeruginosainfection.P. aeruginosainfection increased the expression of mouse NKG2D ligands (Rae1) in airway epithelial cells and alveolar macrophages in vivo and also increased the cell surface expression of human NKG2D ligands (ULBP2) on airway epithelial cells in vitro. NKG2D receptor blockade with a specific monoclonal antibody inhibited the pulmonary clearance ofP. aeruginosa.NKG2D receptor blockade also resulted in decreased production of Th1 cytokines and nitric oxide in the lungs ofP. aeruginosa-infected mice. Additionally, NKG2D receptor blockade reduced the epithelial cell sloughing that accompaniesP. aeruginosainfection. Macrophage phagocytosis and bronchoalveolar lavage cellularity were not different inP. aeruginosa-infected mice with and without NKG2D receptor blockade. These results demonstrate the importance of NKG2D-mediated immune activation in the clearance of acute bacterial infection and suggest that epithelial cell-lymphocyte interactions mediate pulmonary cytokine production, epithelial cell integrity, and bacterial clearance.