Thrombus formation is the important pathologic finding observed in
glomerulonephritis induced by antiglomerular basement membrane (GBM)
antibodies. Although strong deposition of C3 and
membrane attack complex (MAC) is observed in this disease, the role of
complement has not been fully elucidated. The aim of this work was to investigate the role of
complement, especially an
anaphylatoxin C5a, in a rat model of thrombotic
glomerulonephritis. Rats were first pretreated with subclinical dose of
lipopolysaccharide (LPS). Thrombotic
glomerulonephritis was then induced by
intravenous injection with rabbit antirat GBM (RbAGBM) (Group I). For the evaluation of the role of
complement, the soluble
complement receptor type 1 (sCR1) (Group II) or the
C5a receptor antagonist
peptide (C5aR-AP) (Group III) was intravenously administered 30 min before RbAGBM injection. For exploring the role of neutrophils, rats were pretreated with
cyclophosphamide before induction of disease (Group IV). All rats were sacrificed at 6 h, and histological examination was performed. Rats in Group I developed severe glomerular
thrombosis. Leucocyte accumulation and strong binding of C3 and MAC were observed in the glomeruli. In rats treated with sCR1 (Group II) and C5aR-AP (Group III), both leucocyte accumulation and
thrombus formation in the glomeruli were significantly inhibited. C3 and MAC were negative in the glomeruli in Group II rats, while they were strongly observed in Group III. In neutrophil depleted rats (Group IV), there was also deposition of C3 and MAC in the glomeruli but
thrombus formation was not observed. These findings indicated that glomerular
thrombosis is dependent on the leucocytes, and mediated in part by the
anaphylatoxin C5a but not MAC in the present model.