The relative roles of bacteria and host inflammatory cells in SIgA degradation.

Objective: Secretory Immunoglobulin (Ig) A, the most important Ig for lung defense, is highly dependent on its molecular structure for its immune activity. Proteolytic cleavage of SIgA may occur in the airways and render the SIgA molecule inactive. Previous studies have attributed IgA cleavage to neutrophils (polymorphonucleur cells [PMNs]) and other host immunoinflammatory cells in the airways or bacterial pathogens.

Cleavage of SIgA by gram negative respiratory pathogens enhance neutrophil inflammatory potential.

Objective: Secretory immunoglobulin A (SIgA), the principle immune defense at respiratory and other mucosal sites in the body, is highly dependant on its molecular structure for effective antibody function. Previous studies have demonstrated that gram-negative but not gram-positive isolates from patients with nosocomial pneumonia have IgA protease activity that contributes to the development of infection. We postulate that SIgA cleavage by bacteria would also affect anti-inflammatory properties of IgA and studied this in vitro.