Am. J. Respir. Crit. Care Med., Vol 155, No. 6, Jun 1997, 2064-2071.
Cellular association of antiproteases in lavages from ventilated preterm human neonates
M Griese, M Schredl, K Hochstrasser and W Gebhard
Lung Research Group, Kinderpoliklinik, and Klinik und Poliklinik fur Hals-, Nasen-, und Ohrenkrande, Ludwig-Maximilians University, Munich, Germany.
Lung antiprotease activity is routinely assayed in the supernatant of
bronchoalveolar lavage fluid (BALF). In this study the cellular fraction of
lavages was also analyzed. Functionally active acid- resistant inhibitors
with molecular masses characteristic of the mucus proteinase inhibitor
(MPI, 14 kDa) and elastase-specific inhibitor (ESI, 7 kDa) were
demonstrated by gel chromatography. Immunocytochemical studies of cells
obtained at various postnatal time points from lavages of 10 premature
infants with chronic lung disease showed that the inhibitors were confined
to neutrophils and macrophages. At each time point, about 70% and 21% of
these cells, respectively, stained positively. The polyclonal antibodies
usually used to detect MPI did not distinguish between MPI and ESI. Because
of this cross reactivity, it was not possible to differentiate between MPI
and ESI. Analysis with reverse transcriptase-polymerase chain reaction
(RT-PCR) of cells from lavages and of nucleated cells isolated from the
peripheral blood showed the production of ESI only, but not of MPI.
Nevertheless, MPI can associate with neutrophils and macrophages, as was
shown in binding studies with the recombinant protein. These data suggest
that when assaying bronchoalveolar lavages (BALs) for these antiproteases
in the supernatant only, the total pool of inhibitors may be
underestimated.
