NEUTROPHIL-ENDOTHELIAL CELL-INTERACTION IN CRITICAL ILLNESS

Sepsis syndrome frequently results in endothelial injury in many organ systems. To evaluate neutrophil-pulmonary endothelial cell interaction in the sepsis syndrome, we studied 39 critically ill patients prospectively and 20 normal volunteers. Thirteen patients with sepsis (mean age, 71.4 years), 14 patients in an intensive care unit control group (mean age 65.4 years), and 12 patients admitted with acute myocardial infarction (mean age, 66.8 years) were evaluated. Blood samples were drawn from septic patients within 24 hours and from ICU and MI patients within 72 hours of admission. All sepsis patients were culture positive, 6 of 13 from the blood. Both renal failure and ARDS developed in 54 percent of septic patients. Cr-51-labelled neutrophils were prepared and added to bovine pulmonary endothelial cell monolayers with and without added phorbol myristate acetate. Endothelial cells with adherent PMA and nonadherent PMN's, were harvested and radioactivity in each fraction measured with a gamma scintillation counter. Baseline and maximally stimulated (PMA, 3.0 ng/ml) neutrophil adherence to endothelial cells were similar in all patient groups. However, in septic patients, PMA-stimulated PMN adherence was reduced at lower doses, most significantly in those who developed ARDS within 24 to 48 hours of admission (p < 0.05). Seventy-one percent of patients who developed ARDS had reduced stimulated adherence (PMA 1.0 ng/ml) compared to 22 percent of critically ill patients who did not. We conclude that diminished adherence of neutrophils to endothelium in response to low-level PMA stimulation is significantly more common in patients with sepsis who develop ARDS. Our findings suggest that PMN-endothelial cell interaction is altered by the time sepsis is clinically recognized but before the development of ARDS. We speculate that the observed reduction in adherence of the PMN to endothelial cells may be a consequence of down-regulation by mediators generated in the inflammatory response to sepsis and/or the need for active participation of septic endothelium in this interaction.