Alveolar macrophages of children suffering from recurrent infections of respiratory tract are less efficient in eliminating apoptotic neutrophils

During bacterial infections of the respiratory tract, neutrophils (PMN) are recruited to the lung by various mechanisms, including production of inter leukin-8 (IL-8) by alveolar macrophages (AM). After fulfilling their defens e function, PMN become apoptotic and have to be disposed of by AM to preven t local damage to the lung tissue by oxygen species and proteolytic enzymes . We measured the levels of IL-8 in the bronchoalveolar lavage (BAL) and th e ability of AM to engulf senescent PMN in a groups of children with and wi thout recurrent infections of the respiratory tract. The IL-8 level was mea sured by enzyme-linked immunosorbent assay (ELISA). The phagocytosis of apo ptotic neutrophils was evaluated microscopically by the presence of myelope roxidase positive material in AMI before and after 1 h of incubation with s enescent PMN. The data show that children suffering from recurrent infections have increa sed IL-8 in BAL and that their AM have a lower ability to engulf apoptotic PMN in vitro. Furthermore, the proportion of annexin V-binding cells was hi gher in BAL of children with recurrent infections of the respiratory tract than in normal controls. (C) 1999 Wiley-Liss, Inc.