Inflammatory response to infectious pulmonary injury.

This review describing the inflammatory response to infectious pulmonary injury is focused on the innate immunity of the distal lung to bacterial pneumonia. The fact that the inflammatory response varies to some extent with the bacterial strain responsible for the infection is emphasised. The key cellular components present in the distal lung are described. The major role of alveolar macrophage is described, inasmuch as it responds to the usual daily challenges of bacteria entering the terminal airways and is capable of initiating an inflammatory reaction if the microbial challenge is either too large or too virulent. Under these conditions, the alveolar macrophages initiate an inflammatory response that recruits large numbers of neutrophils into the alveolar spaces. The strategy of the innate immune response may not be to recognise every possible antigen, but rather to focus on a few, highly conserved structures present in large groups of microorganisms. These structures are referred to as pathogen-associated molecular patterns and the receptors of the innate immune system that evolved to recognise them are called pattern-recognition receptors. The soluble factors in innate defence, such as cytokines, are described, and a last paragraph discusses whether a specific inflammatory response could characterise nosocomial pneumonia.