Hemorrhagic shock impairs mucosal immunity to gut-derived antigens

Secretory immunoglobulin A (sIgA) is the principal antibody protecting agai nst pathogens in the respiratory tract and other mucosal surfaces. Nosocomi al pneumonias are frequent after injury and critical illness and are often due to enteric pathogens. The aim of this study was to assess the relative effect of hemorrhagic shock (HS) on mucosal immunity at intestinal and resp iratory mucosal sites. Fisher rats were immunized intragastrically with din itrophenylated (DNP) Pneumococcus (Pn). Three weeks later, animals were sub jected to sham treatment or HS. The animals were then rechallenged with DNP -Pn 1 or 3 days later. Animals were sacrificed 7 days later, and bronchoalv eolar and gastric lavage was performed. Total and anti-DNP-specific sIgA we re quantitated from these secretions by enzyme-linked immunosorbent assay. There was a significant decrease in DNP-Pn-specific sIgA at 72 hours after HS, which was not present in animals at 24 hours after HS. This was most pr ofound in bronchoalveolar lavage specimens. We conclude that impaired mucos al defense against gut-derived antigens after HS may be important mechanist ically for the development of posttraumatic pneumonia and other mucosally r elated infectious complications.