Anti–Interleukin 8 Autoantibody:Interleukin 8 Immune Complexes Visualized by Laser Confocal Microscopy in Injured Lung

Abstract Context.—Anti–interleukin 8 autoantibody:interleukin 8 (anti–IL-8 autoantibody:IL-8) complexes are present in lung fluids of patients with acute lung injury/acute respiratory distress syndrome (ALI/ARDS), and levels of these complexes correlate with progression to and the outcome of ARDS. FcγRIIa, an immunoglobulin G (IgG) receptor, mediates proinflammatory activity of the complexes. Objective.—To evaluate lung tissues from patients with ARDS for presence of anti–IL-8 autoantibody:IL-8 complexes and to establish whether the complexes associate with FcγRIIa. Design.—Lung tissue sections from 3 patients with ARDS and sections of normal lung tissues from 3 patients were stained with antibodies against IL-8 and IgG to detect immune complexes and with antibody against FcγRIIa. In some experiments, sections were blocked with anti-Fcγ RIIa antibody before staining. Samples were analyzed using confocal microscopy. Results.—Interleukin 8 costained with IgG and FcγRIIa in lung tissues from patients with ARDS but not in control tissues, suggesting that anti–IL-8 autoantibody:IL-8 complexes are deposited in lungs of patients with ARDS via FcγRIIa. Further, colocalization between IL-8 and FcγRIIa could be blocked by anti-FcγRIIa. Conclusions.—Our data demonstrate that anti–IL-8 autoantibody:IL-8 complexes are present in lung tissues of patients with ARDS, and are attached to FcγRIIa.