A single footpad injection of a triglycosyl
glycopeptide (
nephritogenoside, NG) isolated from rat glomerular basement membrane can induce proliferative
glomerulonephritis (PGN) in homologous animals, resulting in contracted kidney. On the other hand, it is well known that administration of rat tubular brush border
antigen (Fx1A) causes a
membranous glomerulonephritis (MG) in homologous animals. When a partially purified NG (crude NG, cNG) is injected in rats, a mixed lesion of PGN and MG resulted. To investigate the correlation between renal glomerular lesions and humoral immune responses in animals given NG and cNG, levels of
antibodies to cNG and Fx1A, and those of
immune complexes (ICs) are measured in sera from animals of these experimental groups using
enzyme-linked
immunosorbent assay. Significant levels of
antibodies to cNG and Fx1A and those of ICs are detected in all groups of rats injected with cNG, Fx1A and
pronase-digested Fx1A. It was revealed that
antibodies to cNG in sera from rats injected with cNG, Fx1A and
pronase-digested Fx1A recognize the common
epitopes shared with Fx1A. On the other hand, neither
antibodies nor ICs are detected in rats injected with NG, suggesting that humoral immune mechanisms may not play a leading role in the pathogenesis of NG-induced
glomerulonephritis.