The goal of these studies is to determine the role of bacterial DNA in the development of Hypersensitivity Pneumonitis (HP), an environmental lung disease caused by contamination of hay by thermophilic bacteria. Previous studies have shown that Th1 responses with activation of Interleukin-12 are important in HP. Studies have shown that bacterial DNA is a powerful inducer of IL-12. The role of bacterial DNA in triggering the inflammatory response of HP is not known. To study this, a murine model of HP will be used, where mice will be intranasally installed with thermophilic bacteria. Groups of mice will be treated with thermophilic bacteria that have had the DNA destroyed and compared to groups treated with bacteria with intact DNA. The inflammatory response will be evaluated with histopathology, lung lavage cellarity and lung index. Cytokine responses will be evaluated in lung preparations. Less inflammatory and cytokine responses are expected in mice where DNA has been destroyed.