Expression profiles of hydrophobic surfactant proteins in children with diffuse chronic lung disease

Background: Abnormalities of the intracellular metabolism of the
hydrophobic surfactant proteins SP-B and SP-C and their precursors
may be causally linked to chronic childhood diffuse lung diseases.
The profile of these proteins in the alveolar space is unknown in
such subjects. Methods: We analyzed bronchoalveolar lavage fluid by
Western blotting for SP-B, SP- C and their proforms in children
with pulmonary alveolar proteinosis ( PAP, n = 15), children with
no SP- B ( n = 6), children with chronic respiratory distress of
unknown cause ( cRD, n = 7), in comparison to children without lung
disease ( n = 15) or chronic obstructive bronchitis ( n = 19).
Results: Pro-SP-B of 25 - 26 kD was commonly abundant in all groups
of subjects, suggesting that their presence is not of diagnostic
value for processing defects. In contrast, pro-SP-B peptides
cleaved off during intracellular processing of SP- B and smaller
than 19 - 21 kD, were exclusively found in PAP and cRD. In 4 of 6
children with no SP- B, mutations of SFTPB or SPTPC genes were
found. Pro-SP-C forms were identified at very low frequency. Their
presence was clearly, but not exclusively associated with mutations
of the SFTPB and SPTPC genes, impeding their usage as candidates
for diagnostic screening. Conclusion: Immuno-analysis of the
hydrophobic surfactant proteins and their precursor forms in
bronchoalveolar lavage is minimally invasive and can give valuable
clues for the involvement of processing abnormalities in pediatric
pulmonary disorders.