Quantity and structure of surfactant proteins vary among patients with alveolar proteinosis

Alveolar proteinosis (AP) is an idiopathic condition characterized by excess alveolar surfactant. Although the surfactant proteins (SP) are known to be aberrant, little is known of their variation between patients or their abundance relative to the lipids. We have examined surfactant composition in lavage fluid from 16 normal subjects and 13 patients with AP, one of whom was lavaged on 11 occasions over similar to 13 mo. In this patient we have examined composition on each occasion and in each sequential lavage aliquot. Composition was constant between right and left lung, but it differed markedly between patients. The cholesterol/disaturated phospholid ratios (CHOL/DSP) were invariably elevated, on average by similar to 7-fold, whereas the SP-A/DSP and SP-B/DSP ratios were generally elevated, in some cases by as much as similar to 40- and similar to 100-fold, respectively. Although AP ravage generally contained more non-thiol-dependent SP-A aggregates and low M-r isoforms, the two-dimensional immunochemical staining patterns varied between patients and right and left lung. In the patient lavaged on multiple occasions, the SP-A/DSP and SP-B/DSP ratios progressively decreased as the patient's condition resolved. Because the SP-B/SP-A ratio was normal in all cases, we suggest that structural changes to the proteins occurred secondarily and that caution must be used in comparing functional data derived using SP-A obtained from patients with AP.