Heterogeneity of antibody response to glomerular basement membrane antigen in patients with different forms of glomerulonephritis.

ABSTRACT

Antibodies to collagenous and noncollagenous components of glomerular basement membrane (GBM) have been detected by immunoblotting in some sera from patients with various kinds of glomerulonephritis. A half proportion of patients with rapidly progressive glomerulonephritis (RPGN), chronic focal glomerulonephritis (CFGN), idiopathic membranous glomerulonephritis (MGN). IgA nephropathy and lupus nephritis (LE-GN) had IgG antibodies to heterogenous components in acid insoluble fraction of pepsin digested GBM. This acid insoluble fraction represented a complex of collagen and noncollagenous proteins of GBM. Following digestion of acid insoluble fraction with bacterial collagenase, the triple helical collagenous components of GBM were destroyed and released most likely of noncollagenous proteins. Antibodies to this noncollagenous proteins were found in only some patients with chronic glomerulonephritis (17.6%) and lupus nephritis (21.4%). Upon reaction with human placenta derived type IV collagen, different frequencies of antibody response were found in patients of different groups. However, all these reactive sera showed a similar immunoblotting pattern. The relationship between antibody response to antigenic components from human GBM or human placenta and pathogenesis of renal disease is unclear. However, the occurrence of spontaneous autoantibody response to some exposed GBM self antigens may mediate further renal destruction resulting in chronic ongoing stage of the disease.