Studies on bronchoalveoar lavage (BAL) fluid of infants developing CLD have shown large numbers of neutrophils and macrophages in the airways. G-CSF and GM-CSF are known to increase the activity of granulocytes and macrophages, therefore these factors could be important in determining the number and the function of neutrophils (N) and macrophages in the lungs of patients with CLD. This study was undertaken to determine: 1) concentrations of G- and GM-CSF in the BAL fluid of preterm infants developing CLD, 2) whether G- and GM-CSF concentrations correlate with neutrophil and macrophage counts in BAL, and 3) whether alveolar macrophages (AMs) are sources of G- CSF and GM-CSF. BAL was performed in 11 ventilated infants (BW≤1350g) during endotracheal intubation. Dexamethasone (Dxm) was administered to 4/6 infants who later developed CLD, starting on day 10 to 12. BAL specimens obtained while on Dxm were analyzed separately. Table
Correlation coefficients between G-CSF and Ns or AMs, and between GM-CSF and Ns or AMs were:0.62, 0.65, 0.56, 0.67. BAL concentrations (pg/mL) of G-CSF and GM-CSF were 1327±414 and 20±3, before Dxm, and 280±98 and 6±7, after Dxm. G- and GM-CSF gene expression was found by RT-PCR in AMs from most specimens. Isolated AMs released detectable amounts (ELISA) of G-and GM-CSF, and addition of 10 -6M Dxm strongly inhibited the LPS- dependent production of either cytokine (ELISA). We conclude that:1)G-CSF and GM-CSF are produced in the lungs of patients developing CLD in concentrations that increase over the first month of life and parallel an infiltrate of Ns and AMs; 2)G-and GM-CSF production in the lung is reduced following Dxm treatment;3)AMs are a source of G- and GM-CSF, and their production is inhibited by Dxm.
