Immunoglobulin A levels in bronchial samples during mechanical ventilation and onset of nosocomial pneumonia in critically ill patients.

Abstract

Local immunoglobulins play a key role in host defense against lung infection. We investigated the pattern of evolution of bronchial albumin, IgA, and IgG levels in ventilated ICU patients in relation to nosocomial pneumonia. Immunocompetent, critically ill patients underwent serial blood and bronchial protein determinations on Day 1 (intubation day), and on Days 3, 7, 10, and 14. The variations in proteins levels were compared with corresponding Day 1 values in the whole population, and between patients who developed lung infections (Group A) and the remaining population (Group B). Forty-four patients were included into the study. In the whole population, when compared with the baseline value, bronchial IgA/albumin ratio increased significantly (Day 3, +58%, p = 0.04); Day 14, +171%, p < 0.01), but serum IgA/albumin and serum and bronchial IgG/albumin ratios did not change significantly. In Group A, the increase in the IgA/albumin ratio was less than in Group B (Day 3, +15% versus +87%, p = 0.04; Day 14, +29% versus +210%, p < 0.01). No significant differences were observed between the two groups for bronchial and plasma albumin and IgG levels and for bronchial polymorphonuclear elastase levels. Bronchial IgA production was enhanced in ventilated patients. A reduction in this enhanced bronchial IgA production might account for the development of nosocomial pneumonia.

Injury Stimulates an Innate Respiratory Immunoglobulin A Immune Response in Humans

“…18 Others found that sputum IgA levels correlate inversely with tracheal cell adherence by bacteria. 19,20 An increased adherence indicates increased vulnerability to bacterial invasion by those organisms.…”

Injury Induces Localized Airway Increases in Pro-Inflammatory Cytokines in Humans and Mice

“…Although multiple components defend this border, the strategic molecule of mucosal immunity is secretory immunoglobulin A (sIgA) [7]. This protein binds pathogens at the mucosal border and prevents their attachment to the mucosa and tissue invasion, thereby protecting the host from pneumonia [8,9].…”

The gastrointestinal immune system: Implications for the surgical patient

“…Aspiration of saline lavages from distal bronchioles using fiberoptic bronchoscopy and simultaneous measurement of blood urea nitrogen allows calculation of the volume of ELF recovered by the equation: volume ELF (mL) = (mg urea in BAL)/(plasma urea concentration in mg/mL). 133,134 This technique can be applied to determine IgA and cytokine concentration changes in ELF and well as changes in ELF itself. Samples were obtained for analysis from 12 trauma patients sustaining severe blunt injury who were expected to require intubation for a minimum of 5 days in the ICU.…”