Secretory immunoglobulin A abrogates inflammatory responses and improves mortality after pseudomonas pneumonia

Secretory immunoglobulin A (SIgA) is the principle antibody at respiratory and other mucosal sites. Its concentration in mucosal secretions is influenced by route of nutrition and insults common to the trauma patient. SIgA has anti-inflammatory effects, which may protect against exaggerated inflammatory responses after infection. Polyimmunoglobulin receptor (pIgR) knockout (KO) mice, which do not have SIgA in mucosal secretions but are otherwise immunologically intact, were used to study the importance of SIgA in respiratory secretions after bacterial pneumonia.

Pseudomonas aeruginosa or phosphate-buffered saline was administered intratracheally to pIgR-KO or conventional mice. Mortality was noted at 72 hours. Surviving animals were killed and blood, lung, and bronchoalveolar lavage (BAL) fluid samples were obtained and analyzed for myeloperoxidase, cytokine, and IgG levels.

Pneumonia was associated with increases in blood and bronchoalveolar lavage cytokine levels and increased lung myeloperoxidase activity. These results were significantly greater in pIgR-KO mice and associated with a threefold increase in mortality.

The importance of SIgA in maintaining mucosal homeostasis is demonstrated in this study, and the study supports efforts to preserve mucosal immune function in the trauma patient.