Effect of antibody-mediated neutropenia on the cardiopulmonary response to endotoxemia

An ovine anti-neutrophil antibody has been produced by immunizing rabbits with purified sheep neutrophils. Serial intraarterial infusions of anti-neutrophil antibody in awake instrumented sheep produced selective and profound neutropenia. Intravascular infusion of endotoxin (Escherichia coli, 1.5 μg/kg/30 min) resulted in significant and equivalent increases in pulmonary artery pressure, peripheral vascular resistance, and protein-rich pulmonary lymph flow in an endotoxin group (n = 9) and a depletion + endotoxin group (n = 4). Changes in cardiopulmonary parameters were most pronounced 2 to 8 hr after endotoxin administration in both groups. Cardiac index (CI) showed a precipitous and transient fall in both experimental groups at 0.5 to 1 hr after endotoxin infusion; however, by 8 hr CI rose significantly in the endotoxin group, while it remained unchanged in the depletion + endotoxin group. A significant rise in the peripheral neutrophil count was associated with the increase in CI in the endotoxin group. Plasma and pulmonary lymph levels of thromboxane -B₂ were unchanged during the depletion period with a significant increase 1 hr after endotoxin infusion. In this study questions arise regarding the exclusive role of circulating neutrophils in the microvascular permeability changes seen in sepsis-mediated adult respiratory distress syndrome.