Immunoreactive Interleukin-1 in Bronchoalveolar Lavage Fluid of High-Risk Patients and Patients with the Adult Respiratory Distress Syndrome

Abstract

The adult respiratory distress syndrome (ARDS) is characterized by increased neutrophils and macrophages in bronchoalveolar lavage (BAL) fluid. Interleukin-1 (IL-1), an inflammatory mediator produced by macrophages, has been shown to be chemo-tactic for neutrophils and to stimulate lymphocyte activation and proliferation of fibro-blasts. BAL was performed in patients with ARDS, patients at high risk to develop ARDS, and in normal nonsmokers. After removal of cells and surfactant-complexed lipids by centrifugation, the remaining supernatant was concentrated by ukrafiltration utilizing membranes retaining substances greater than 5000 daltons. The concentrate was assayed for immunoreactive IL-1_β by a radioimmunoassay method. Patients with ARDS (n = 9) had an IL-1 level of 184 ± 67 pg/ml, high-risk patients (n = 9) had 172 ± 62 pg/ml, and normals (n = 10) had 4 ± 1 pg/ml. There was a significant (p ≤ .05) increase in IL-1 in the ARDS and risk groups compared to normals. IL-1 was detected in serum from patients with ARDS (n = 19), high risk (n = 19), and normals (n = 8), but no difference was noted among the three groups. BAL cell differentials revealed that neutrophils were increased (p < .05) in both the ARDS (59 ± 10%) and high-risk (65 ± 8%) groups compared to normals (2 ± 1%). There was a correlation (r = 0.64, p < .001) between IL-1 levels and BAL protein concentration. BAL IL-1 levels were highest in patients with the fully developed syndrome but were also elevated in patients at high risk. The absence of significant amounts of IL-1 in serum suggests that it may be produced within the lung.