Activity of pulmonary edema fluid interleukin-8 bound to α2-macroglobulin in patients with acute lung injury

Abstract

The formation of α2-macroglobulin (α2-M)/interleukin-8 (IL-8) complexes may influence the biological activity of IL-8 and the quantitative assessment of IL-8 activity. Therefore, in this study, concentrations of free IL-8 and IL-8 complexes with α2-M were measured in pulmonary edema fluid samples from patients with acute lung injury/acute respiratory distress syndrome (ALI/ARDS) and compared with control patients with hydrostatic pulmonary edema. Patients with ALI/ARDS had significantly higher concentrations of α2-M ( P < 0.01) as well as α2-M/IL-8 complexes ( P < 0.05). Because a substantial amount of IL-8 is complexed to α2-M, standard assays of free IL-8 may significantly underestimate the concentration of biologically active IL-8 in the distal air spaces of patients with ALI/ARDS. Furthermore, IL-8 bound to α2-M retained its biological activity, and this fraction of IL-8 was protected from proteolytic degradation. Thus complex formation may modulate the acute inflammatory process in the lung.