Background: Inhaled endotoxin or lipopolysaccharide (LPS) is implicated in the pathogenesis of pulmonary diseases. We investigated the inhalation effects of two different doses of LPS in healthy human subjects.
Methods: Eighteen healthy non-atopic human subjects inhaled either 15 microg (n=10) or 50 microg (n=8)Escherichia coli LPS in an open study. As control, each subject had isotonic saline inhalation 1 week before (baseline) and after LPS inhalation. Data collected included those of clinical parameter, induced sputum and peripheral blood CD4+ and CD8+ T cells.
Results: Acute flu-like symptoms and pyrexia were significantly greater in the 50 microg than 15 microg LPS group. Similarly, the increase in sputum and blood total cell and neutrophil counts at 6h following inhaled LPS were greater in the 50 microg group. Myeloperoxidase, human neutrophil elastase and interleukin-8 in sputum sol, but not blood, showed a trend towards greater increase following 50 microg LPS. All these changes were resolved at one week. In the 50 microg dose group alone, there was a reduction in the proportion of peripheral blood interferon (IFN)-gamma-producing CD4+ and CD8+ T cells at 6h followed by an increase at 1 week after inhaled LPS.
Conclusions: The airway and systemic effects of inhaled LPS are dose-related and predominantly neutrophilic. The changes in the proportions of circulating CD4+ and CD8+ T cells suggests preferential recruitment of IFN-gamma-producing T cells into tissue from inhaled 50 microg LPS, followed by reappearance of these cells in blood 1 week later.