Lung surfactant and reactive oxygen-nitrogen species: antimicrobial activity and host-pathogen interactions

Surfactant protein (SP) A and SP-D are members of the collectin superfamily . They are widely distributed within the lung, are capable of antigen recog nition, and can discern self versus nonself. SPs recognize bacteria, fungi, and viruses by binding mannose and N-acetylglucosamine residues on microbi al cell walls. SP-A has been shown to stimulate the respiratory burst as we ll as nitric oxide synthase expression by alveolar macrophages. Although ni tric oxide (NO .) is a well-recognized microbicidal product of macrophages, the mechanism(s) by which NO . contributes to host defense remains undefin ed. The purpose of this symposium was to present current research pertainin g to the specific role of SPs and reactive oxygen-nitrogen species in innat e immunity. The symposium focused on the mechanisms of NO-mediated toxicity for bacterial, human, and animal models of SP-A- and NO-mediated pathogen killing, microbial defense mechanisms against reactive oxygen-nitrogen spec ies, specific examples and signaling pathways involved in the SP-A-mediated killing of pulmonary pathogens, the structure and binding of SP-A and SP-D to bacterial targets, and the immunoregulatory functions of SP-A.