Elevated levels of lung surfactant protein A in sera from patients with idiopathic pulmonary fibrosis and pulmonary alveolar proteinosis

Am Rev Respir Dis. 1993 Mar;147(3):723-9. doi: 10.1164/ajrccm/147.3.723.


An enzyme-linked immunosorbent assay using monoclonal antibodies to human lung surfactant protein A (SP-A) was applied to sera from patients with lung diseases. We examined whether SP-A appears in the sera of patients with diseases that are known to cause alterations in surfactant composition in bronchoalveolar lavage fluids, and we characterized the SP-A that was found. The level of SP-A in sera from 57 healthy volunteers was 45 +/- 3 ng/ml (mean +/- SEM). The levels in patients with idiopathic pulmonary fibrosis (IPF) (205 +/- 23 ng/ml, n = 32) and pulmonary alveolar proteinosis (PAP) (285 +/- 23 ng/ml, n = 6) were significantly higher than those in healthy control subjects (p < 0.01), whereas those of sarcoidosis (n = 16), pneumonia (n = 14), and tuberculosis (n = 14) were 52 +/- 27 ng/ml, 65 +/- 11 ng/ml, and 49 +/- 23 ng/ml, respectively. Electrophoresis and immunoblotting analysis demonstrated that the fraction isolated from serum of a patient with PAP or IPF by anti-SP-A immunoaffinity column chromatography consisted chiefly of human IgG and IgM, and that it also contained SP-A. Furthermore, IgG was found in preparation of purified human SP-A. SP-A was demonstrated to bind to nonimmune IgG coated onto microtiter wells. Gel filtration analysis revealed that serum SP-A was eluted at fractions of larger molecular size than was the purified SP-A. These findings suggest that SP-A appears in the bloodstream as a complex with immunoglobulin in IPF and in PAP.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Chronic Disease
  • Glycoproteins / blood*
  • Hepatitis / blood
  • Humans
  • Liver Cirrhosis / blood
  • Lung Diseases / blood
  • Methods
  • Middle Aged
  • Pancreatitis / blood
  • Proteolipids / blood*
  • Pulmonary Alveolar Proteinosis / blood*
  • Pulmonary Fibrosis / blood*
  • Pulmonary Surfactant-Associated Protein A
  • Pulmonary Surfactant-Associated Proteins
  • Pulmonary Surfactants / blood*
  • Sarcoidosis / blood
  • Tuberculosis, Pulmonary / blood


  • Glycoproteins
  • Proteolipids
  • Pulmonary Surfactant-Associated Protein A
  • Pulmonary Surfactant-Associated Proteins
  • Pulmonary Surfactants