Elevated levels of lung surfactant protein A in sera from patients with idiopathic pulmonary fibrosis and pulmonary alveolar proteinosis.
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.
Kuroki
Y
Y
Department of Biochemistry, Sapporo Medical College, Japan.
Tsutahara
S
S
Shijubo
N
N
Takahashi
H
H
Shiratori
M
M
Hattori
A
A
Honda
Y
Y
Abe
S
S
Akino
T
T
D000368:Aged; D002908:Chronic Disease; D006023:Glycoproteins / Q000097:blood*; D006505:Hepatitis / Q000097:blood; D006801:Humans; D008103:Liver Cirrhosis / Q000097:blood; D008171:Lung Diseases / Q000097:blood; D008722:Methods; D008875:Middle Aged; D010195:Pancreatitis / Q000097:blood; D011510:Proteolipids / Q000097:blood*; D011649:Pulmonary Alveolar Proteinosis / Q000097:blood*; D011658:Pulmonary Fibrosis / Q000097:blood*; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000097:blood*; D012507:Sarcoidosis / Q000097:blood; D014397:Tuberculosis, Pulmonary / Q000097:blood
D006023:Glycoproteins; D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants