Am. J. Respir. Crit. Care Med., Vol 155, No. 5, 05 1997, 1785-1788.
Immunoglobulin G is associated with surfactant protein A aggregate isolated from patients with pulmonary alveolar proteinosis
A Hattori, Y Kuroki, H Takahashi, H Sohma and T Akino
Department of Biochemistry, Sapporo Medical University School of Medicine, Chuo-ku, Japan.
We have previously shown that the purified preparation of surfactant
protein A (SP-A) isolated from patients with pulmonary alveolar proteinosis
(PAP) contains a very small amount of immunoglobulin G (IgG). We have
recently found that there exists an abnormal multimerized form (alveolar
proteinosis protein-I, APP-I) in SP-As isolated from patients with PAP in
addition to normal-sized octadecameric APP-II. We examined which of the
populations of APP that IgG is associated with. The APP was purified by
mannose-affinity column followed by gelfiltration over Bio Gel A5m after
the delipidation with 1-butanol. Analysis by gel filtration over Bio Gel
A15m showed two elution peaks of APP-I and APP-II. When the fractions
eluted from the Bio Gel A15m column were coated onto microtiter wells and
reacted with HRP-labeled antihuman IgG, the elution peak of IgG was
superimposed on that of APP-I but not on that of APP-II. The immunoblotting
analysis also revealed that a very small amount of IgG, which could not be
detected by staining with Coomassie blue or amido black, was associated
with APP-I but not with APP-II or normal SP-A. APP-I bound to nonimmune IgG
coated onto microtiter wells in a concentration-dependent manner, whereas
APP-II, normal human SP-A, and rat SP-A exhibited almost no binding to IgG.
The results indicate an unusual property of SP-A during the diseased state.
