CELLULAR-ASSOCIATION OF ANTIPROTEASES IN LAVAGES FROM VENTILATED PRETERM HUMAN NEONATES

Lung antiprotease activity is routinely assayed in the supernatant of bronchoalveolar ravage fluid (BALF). In this study the cellular fracti on of lavages was also analyzed. Functionally active acid-resistant in hibitors with molecular masses characteristic of the mucus proteinase inhibitor (MPI, 14 kDa) and elastase-specific inhibitor (ESI, 7 kDa) w ere demonstrated by gel chromatography. Immunocytochemical studies of cells obtained at various postnatal time points from lavages of 10 pre mature infants with chronic lung disease showed that the inhibitors we re confined to neutrophils and macrophages. At each time point, about 70% and 21% of these cells, respectively, stained positively. The poly clonal antibodies usually used to detect MPI did not distinguish betwe en MPI and ESI. Because of this cross reactivity, it was not possible to differentiate between MPI and ESI. Analysis with reverse transcript ase-polymerase chain reaction (RT-PCR) of cells from lavages and of nu cleated cells isolated from the peripheral blood showed the production of ESI only, but not of MPI. Nevertheless, MPI can associate with neu trophils and macrophages, as was shown in binding studies with the rec ombinant protein. These data suggest that when assaying bronchoalveola r lavages (BALs) for these antiproteases in the supernatant only, the total pool of inhibitors may be underestimated.