Glomerular basement membrane type IV collagen antigens in Goodpasture's and Alport's syndromes

Abstract

Type IV collagen, the main constituent of the renal glomerular basement membrane, is involved in Goodpasture's syndrome, and autoimmune disease, and in Alport's syndrome, a genetic disease. There are 6 alpha chains, α1(IV) through α6(IV), in type IV collagen in mammals. Immunohistochemical studies, using α-chain-specific monoclonal antibodies on tissue specimens from healthy people and patients with Alport's syndrome, have shown that there are 3 forms of type IV collagen molecules in mammalian basement membranes, namely α1/α1/α2, α3/α4/α5, and α5/α5/α6. Antibody specificity analysis of sera from patients with Goodpasture's syndrome show that all sera have autoantibody, with the highest titer against α3(IV)NC1, although they also have titers against the other 5α chains. This indicates that α3(IV)NC1 is the major target antigen of the disease, although the glomerular basement membrane contains the α1 through α5 chains. Experimental glomerulonephritis in rats, induced by the injection of 6 recombinant α(IV)NC1s with an adjuvant, has shown that α3(IV)NC1 and α4(IV)NC1 are nephritogenic. The lack of, or very poor, nephritogenicity of the other 4 α(IV)NC1s can be explained by the high immunologic tolerance against these chains, which are distributed widely in basement membranes of the whole body.