Background: We have already reported that there are some periods when a high interleukin 8 (IL-8) concentration is observed in the tracheobronchial aspirate of infants with chronic lung disease (CLD), although the changing pattern of the IL-8 concentration varies depending on the type of CLD. Interleukin 8 is known as a neutrophil chemotactic agent. Therefore, we asked whether IL-8 is an important neutrophil chemotactic factor in the tracheobronchial aspirate of infants who later develop CLD.
Methods and results: We measured the neutrophil chemotactic activity of the tracheobronchial aspirate in CLD infants with or without anti-IL-8 antibody. Preincubation with anti-IL-8 immunoglobulinG resulted in a significant reduction of neutrophil chemotactic activity in the tracheobronchial aspirate. In infants with CLD following respiratory distress syndrome, there was a significant relationship between the IL-8 concentration and the neutrophil chemotactic activity of tracheobronchial aspirate without anti-IL-8 antibody, although no significant relationship was seen in infants with CLD following intra-uterine infection or with other CLD.
Conclusions: Interleukin 8 in the tracheobronchial aspirate seems to play a significant role in recruiting neutrophils into the airways of patients with CLD, especially CLD following respiratory distress syndrome. We believe that in this type of CLD, IL-8 in the lung is generated as a result of hyperoxia rather than infection. In this situation, production of other neutrophil chemotactic factors or some factors that inhibit IL-8 activity may be insignificant.