Hemorrhagic shock impairs mucosal immunity to gut-derived antigens

Secretory immunoglobulin A (sIgA) is the principal antibody protecting against pathogens in the respiratory tract and other mucosal surfaces. Nosocomial 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 respiratory mucosal sites. Fisher rats were immunized intragastrically with dinitrophenylated (DNP) Pneumococcus (Pn). Three weeks later, animals were subjected 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 bronchoalveolar and gastric lavage was performed. Total and anti-DNP-specific sIgA were 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 profound in bronchoalveolar lavage specimens. We conclude that impaired mucosal defense against gut-derived antigens after HS may be important mechanistically for the development of posttraumatic pneumonia and other mucosally related infectious complications.