Anti-interleukin 8 autoantibody:interleukin 8 immune complexes visualized by laser confocal microscopy in injured lung: Colocalization with FcγRIIa in lung tissue from acute respiratory distress syndrome patients

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-FcγRIIa 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.