Abstract
Pneumonia is caused by both viral and bacterial pathogens and is responsible for a significant health burden in the Unites States. The innate immune system is the human body's first line of defense against these pathogens. The recognition of invading pathogens via pattern recognition receptors leads to proinflammatory cytokine and chemokine production, followed by recruitment and activation of effector immune cells. The nonspecific inflammatory nature of the innate immune response can result in immunopathology that is detrimental to the host. In this review, we focus on one class of pattern recognition receptors, the nucleotide-binding oligomerization domain (NOD)-like receptors, specifically NOD1 and NOD2, and their role in host defense against viral and bacterial pathogens of the lung, including influenza, respiratory syncytial virus, Streptococcus pneumoniae, Chlamydophila pneumoniae, and Staphylococcus aureus. It is hoped that improved understanding of NOD1 and NOD2 activity in pneumonia will facilitate the development of novel therapies and promote improved patient outcomes.