Anti-IL-8 autoantibodies in alveolar fluid from patients with the adult respiratory distress syndrome.

IL-8 is a potent neutrophil attractant and activator. IL-8 has been reported to be involved in the pathogenesis of several diseases, including rheumatoid arthritis, sepsis, psoriasis, and the adult respiratory distress syndrome (ARDS). Our previous studies demonstrated that high concentrations of IL-8 were present in alveolar fluids from patients with ARDS and were associated with increased mortality. In this study we report that a major portion of IL-8 in bronchoalveolar fluids from patients with ARDS is associated with anti-IL-8 autoantibody (anti-IL-8:IL-8 complexes). Free autoantibodies that recognize IL-8 were also detected in these fluids. Next, we examined the properties of anti-IL-8 autoantibodies present in lung fluids from ARDS patients and compared them with autoantibodies from normal plasma and arthritic synovial fluids. The anti-IL-8 autoantibody was polyclonal, and IgG3 and IgG4 were the primary IgG subclasses. Anti-IL-8:IL-8 complexes consisted of one IgG and one IL-8 molecule. In addition, anti-IL-8 autoantibody bound IL-8 with a high affinity (approximately 10(-12) M) and inhibited IL-8 interaction with its specific receptors on neutrophils. The results suggest that anti-IL-8 autoantibodies may regulate IL-8 activity.