Targets of alloantibodies in Alport anti-glomerular basement membrane disease after renal transplantation

A minority of patients with Alport syndrome develop anti-GBM disease in their allografts after renal transplantation. Clinically, the renal disease appears indistinguishable from Goodpasture's disease of native kidneys, in which the target of autoantibodies had been identified as the NC1 domain of the alpha 3 chain of type IV collagen, alpha 3(IV)NC1. However, in the majority of cases, Alport syndrome is due to mutations in the gene encoding the alpha 5 chain of type IV collagen, located on the X chromosome. Neither chain is detectable in the glomerular basement membrane (GBM) of most patients with Alport syndrome. We investigated the targets of the alloantibodies of 12 Alport patients who developed post-transplant anti-GBM disease by Western blotting onto recombinant NC1 domains made in insect cells. Binding to these antigens, for both typical Goodpasture and Alport anti-GBM antibodies, was strong and conformation-sensitive. Nine antibodies showed selective binding to alpha 5(IV)NC1. This specificity was confirmed by the demonstration of binding to a 26 kDa band of collagenase-solubilized human GBM, and/or binding to normal epidermal as well as renal basement membranes by indirect immunofluorescence. One antibody showed binding to alpha 5 and alpha 3(IV)NC1, while two showed predominant binding to alpha 3(IV)NC1. All seven patients whose pedigree or mutation analysis showed X-linked inheritance had predominant anti-alpha 5 reactivity. One with predominant anti-alpha 3 reactivity had a COL4A3 mutation. These findings show that human anti-GBM disease can be associated with antibodies directed towards different molecular targets. Alpha 5(IV)NC1 is the primary target in most patients with X-linked Alport syndrome who develop post-transplant anti-GBM disease.     

A single-chain Fv reactive with the Goodpasture antigen

Goodpasture's disease is defined by the presence of autoantibodies to the glomerular basement membrane and characterized clinically by rapidly progressive glomerulonephritis and pulmonary hemorrhage. P1, a murine monoclonal antibody to the Goodpasture antigen (the noncollagenous domain of the alpha 3 chain of type IV collagen, alpha 3(IV)NC1), has been a valuable reagent in investigating the pathogenesis of this disorder. The purpose of this study was to generate and characterize a recombinant form of P1 as a single-chain Fv (scFv). First strand cDNA was made from RNA extracted from the P1 hybridoma cell line, and DNA encoding the antibody light and heavy chain variable domains was amplified by polymerase chain reaction, using universal oligonucleotides. The purified products were ligated sequentially into an expression plasmid separated by a sequence encoding a 15 amino acid flexible oligopeptide linker. The resulting scFv was expressed in E. coli. Functional scFv, designated HBR-3, was obtained by denaturing and refolding the expressed product. HBR-3 was shown by ELISA, immunoblotting, and immunohistologic techniques, to have the same specificity for alpha 3(IV)NC1 as P1 and autoantibodies from patients with Goodpasture's disease. HBR-3 and P1 were shown to have similar affinity for their mutual ligand. On sections of normal human kidney, the scFv bound only to glomerular basement membrane and distal tubular basement membrane. It did not bind to the glomerular basement membrane of patients with Alport's syndrome, in whom the Goodpasture antigen is often not expressed in an antigenic form. We have, therefore, generated a scFv which reproduces the specific binding properties of the parent monoclonal antibody, P1. The potential of HBR-3 as a diagnostic reagent in Alport's syndrome has been demonstrated. The development of this recombinant molecule should permit new approaches to the investigation of Goodpasture's disease.     

Sequence analysis of the 'Goodpasture antigen' of mammals

BACKGROUND: Autoimmunity to the NC1 domain of the alpha3 chain of type IV collagen (alpha3(IV)NC1), the Goodpasture antigen, is the cause of spontaneous human antiglomerular basement membrane (anti-GBM) disease, and of anti-GBM nephritis in several animal models. METHODS: We have derived amino acid sequences from alpha3(IV)NC1 for a number of mammalian species (monkey, sheep, pig, dog, rabbit, and rat) by RT-PCR and cDNA cloning. The GBM of some species was studied comparatively for binding to Goodpasture autoantibodies. RESULTS: From this work and other data the sequences of nine mammalian species can be aligned. Regions and residues that may be functionally important are identified. Alpha3(IV)NC1 sequences were found to be less closely conserved across species than alpha1 and alpha2(IV)NC1, 91 to 99% in comparison to a minimum of 97% for alpha1, but these differences were unevenly distributed along the molecule. There was a particularly striking homology between rodent and human sequences in the carboxyl-terminal region. Binding of Goodpasture autoantibodies to rat alpha3(IV)NC1 was poor in comparison with other species. CONCLUSIONS: Comparison of sequences and binding casts doubt on the importance of the carboxyl-terminal region for antibody binding, a region identified as a potential major epitope in previous studies. Sequence comparisons suggest possible reasons for the nephritogenicity of alpha3(IV)NC1 in active models of anti-GBM disease.     

Susceptibility to anti-glomerular basement membrane disease and Goodpasture syndrome is linked to MHC class II genes and the emergence of T cell-mediated immunity in mice

We developed a new mouse model of human anti-glomerular basement membrane (GBM) disease to better characterize the genetic determinants of cell-mediated injury. While all major histocompatibility complex (MHC) haplotypes (H-2a, k, s, b, and d) immunized with alpha3 NC1 domains of type IV collagen produce anti-alpha3(IV) NC1 antibodies that cross-react with human Goodpasture [anti-GBM/anti-alpha3(IV) NC1] autoantibodies, only a few strains developed nephritis and lung hemorrhage associated with Goodpasture syndrome. Crescentic glomerulonephritis and lung hemorrhage were MHC-restricted in haplotypes H-2s, b, and d (A beta/A alpha region in H-2s) and associated with the emergence of an IL-12/Th1-like T cell phenotype. Lymphocytes or anti-alpha3(IV) NC1 antibodies from nephritogenic strains transfer disease to syngeneic recipients. However, passive transfer of isogenic alpha3(IV) NC1 antibodies into -/- T cell receptor-deficient mice failed to produce nephritis. Finally, nephritis and its associated IL-12/Th1-like T cell response attenuate in disease-susceptible mice tolerized orally to alpha3(IV) collagen before immunization. Our findings suggest collectively, as a hypothesis, that anti-GBM antibodies in mice only facilitate disease in MHC haplotypes capable of generating nephritogenic lymphocytes with special T cell repertoires.     

Oxidant-antioxidant imbalance in the experimental interstitial lung disease induced in sheep by visna-maedi virus

X-linked Alport syndrome (AS) is a heritable disorder which is associated with mutations in the type IV collagen alpha 5 (IV) chain gene (COL4A5) located on chromosome X. Following renal transplantation, an average of 6% of male AS patients develop anti-GBM nephritis. We studied the specificity of the antibodies against type IV collagen in the serum of a patient with COL4A5 partial deletion. The specificity of these alloantibodies was determined against collagenase-digested GBM, as well as against recombinant non-collagenous (NC1) domains of the type IV collagen alpha 1(IV)-alpha 6(IV) chains expressed in escherichia coli. Immunoblotting and ELISA demonstrated that these antibodies bound specifically to the NC1 domain of alpha 5(IV) collagen. There was no binding to the NC1 domain of the other chains, including the Goodpasture antigen. Competitive ELISA confirmed the results obtained by ELISA and immunoblotting. This patient developed alloantibodies directed against antigens present in the grafted kidney, but absent from his Alport kidney. The pathogenesis of post-transplantation glomerulonephritis in the Alport patient studied is thus similar to that of Goodpasture syndrome, with the exception that the pathogenic antibodies are targeted to another alpha chain of type IV collagen.     

Experimental Goodpasture's syndrome in Wistar-Kyoto rats immunized with alpha3 chain of type IV collagen

BACKGROUND: Glomerulonephritis and lung hemorrhage of autoimmune Goodpasture syndrome develop due to immune reactions against epitope(s) of the non-collagenous (NC1) domain of alpha3-chain of type IV collagen [alpha3(IV) NC1]. Whether thymic mechanisms have a role in the loss of tolerance to the Goodpasture epitope has not been established. We studied the renal and pulmonary effects of immunization with different forms (monomer, dimer, or hexamer) of alpha3(IV) NC1 collagen in Wistar-Kyoto (WKY) rats, and assessed whether the intrathymic inoculation of the antigen may protect against anti-GBM disease. METHODS: WKY rats were immunized with bovine alpha3(IV) monomer, dimer, or hexamer, or with alpha3(IV) NC1 synthetic peptide. Renal function, kidney and lung immunohistology, and circulating and tissue bound antibodies to type IV collagen chains were analyzed. Effects of intrathymic inoculation of antigen on subsequent disease induction were analyzed in WKY rats given alpha3(IV) NC1 dimer or GBM preparation intrathymically 48 hours before immunization. RESULTS: Proteinuria, linear IgG deposition in GBM, and crescentic glomerulonephritis developed in WKY rats immunized with alpha3(IV) NC1 dimer or hexamer. Lesions were dose-dependent upon injections of 10 to 100 microgram dimer. The alpha3(IV) NC1 monomer induced less severe proteinuria and no crescents. Pulmonary hemorrhage was detectable in 35% of rats immunized with 25 to 100 microgram alpha3(IV) NC1 dimer; alpha3(IV) synthetic peptide (36 carboxyl terminal) did not induce disease. Rats injected intrathymically with up to 100 microgram alpha3(IV) NC1 dimer or with GBM 48 hours before immunization were not protected against subsequent development of proteinuria and glomerulonephritis. CONCLUSIONS: These findings document that glomerulonephritis and lung hemorrhage can be elicited in WKY rats by immunization with alpha3(IV) NC1. Failure of the intrathymic inoculation of antigen to prevent disease suggests that immunological tolerance cannot be achieved by this intervention, in contrast to other autoimmune conditions, and may imply independent roles for cellular and humoral nephritogenic pathways in anti-GBM nephritis.     

Determination of indomethacin residues in poultry by high-performance liquid chromatography

Linear IgA disease (LAD) is characterized by circulating and tissue-bound IgA antibodies against heterogeneous antigens in the cutaneous basement membrane zone. In most cases the cause is unknown, but a minority of cases has been drug induced. We report a 76-year-old man who developed an acute blistering eruption following high-dose penicillin treatment for pneumococcal septicaemia. Indirect immunofluorescence demonstrated dermal binding IgA antibodies, and Western blotting of serum showed reactivity with a 250 kDa dermal antigen corresponding to collagen VII of anchoring fibrils. Indirect immunoelectron microscopy showed antibody labelling in the lamina densa and sublamina densa zone. This is one of the few cases of drug-induced LAD in which the target antigen profile has been characterized, and the first in which the antigen has been shown to correspond to collagen VII.     

Differential expression of alpha 1(IV), alpha 2(IV), alpha 5(IV) and alpha 6(IV) collagen chains in the basement membrane of basal cell carcinoma

Type IV collagen, the major component of basement membrane, consists primarily of alpha 1(IV) and alpha 2(IV) chains. Recently, other types of collagen IV chains, i.e. alpha 3(IV), alpha 4(IV), alpha 5(IV) and alpha 6(IV) chains, have been identified by protein chemistry and molecular cloning. We have examined the diversity of the assembly of alpha (IV) chains of the basement membrane surrounding tumour nests of basal cell carcinomas, in tissues from 11 patients, by immunohistochemical analysis using specific monoclonal antibodies to six alpha (IV) chain. The immunostaining profile of each chain differed with respect to the histological subtypes of basal cell carcinoma. In the morphea-like subtype, which was more invasive, alpha 1(IV) and alpha 2(IV) chains were discontinuously stained, and alpha 5(IV) and alpha 6(IV) chains were entirely absent. However, in the superficial subtype, which was non-aggressive, alpha 1(IV), alpha 2(IV), alpha 5(IV) and alpha 6(IV) chains were well stained compared with the other subtypes of basal cell carcinoma. In addition, in the solid subtype, which showed slow growth and ulceration, alpha 1(IV) and alpha 2(IV) chains were continuously stained, and alpha 5(IV) and alpha 6(IV) chains were discontinuous or absent. The assembly of alpha 5(IV) and alpha 6(IV) chains into the basement membrane was inhibited in the solid and morphea subtypes of BCC. This differential expression of type IV collagen chains seems to be associated with the invasive potential of basal cell carcinoma.     

Alport syndrome: from bedside to genome to bedside

Alport syndrome is a genetic disorder of basement membranes manifested clinically by a progressive nephropathy and, in many families, sensorineural hearing loss and ocular lesions. During the 1980s evidence was amassed indicating type IV (basement membrane) collagen as the defective protein in Alport This hypothesis was confirmed in 1990 by the cloning of the X-chromosomal gene COL4A5, which encodes the alpha 5 chain of type IV collagen, and the discovery of mutations in this gene in many Alport kindreds. The results of results of recent studies suggest that the alpha 5(IV) chain forms a distinct collagenous network with the alpha 3 and alpha 4 chains of type IV collagen and that mutations in alpha 5(IV) may prevent the normal incorporation of alpha 3(IV) and alpha 4(IV) into basement membranes. Renal biopsy remains an important modality for making the diagnosis of Alport syndrome, but may eventually be replaced by molecular genetic techniques. Posttransplant anti-glomerular basement membrane nephritis occurs rarely in Alport patients and may be restricted to a subgroup with particular COL4A5 mutations. It is not clear why COL4A5 mutations result in glomerulosclerosis and renal failure, or whether this process may be slowed through dietary or pharmacologic intervention.     

Prevalence and characterization of perinuclear anti-neutrophil cytoplasmic antibodies (P-ANCA) directed against HMG1 and HMG2 in ulcerative colitis (UC)

To examine the structural relationship among autoantibodies produced by individuals with anti-GBM antibody-mediated disease, a polyclonal anti-idiotype directed against human anti-alpha3(IV)NC1 antibodies was produced and then used to study autoantibodies from other patients. For this purpose, anti-alpha3(IV)NC1 antibodies (anti-GBM), derived from a single patient (LL) with high titer and typical anti-GBM antibody specificity, were isolated using recombinant alpha3(IV)NC1-sepharose affinity chromatography. Following hyperimmunization of rabbits with anti-GBM IgG, irrelevant rabbit anti-human IgG antibodies were removed from the antiserum using a human IgG-sepharose column. The rabbit anti-alpha3(IV)NC1 antibodies (anti-Id GBM) effluent bound to human anti-GBM antibodies, but it did not bind to either normal human IgG or recombinant alpha3(IV)NC1 protein. The Id-anti-Id interaction was conformationally dependent on intact heavy and light chains of the anti-alpha3(IV)NC1 antibodies (ELISA and Western blotting). A competitive immunoassay was developed to evaluate structural and potential genetic relationships among anti-alpha3(IV)NC1 antibodies from different patients. All patients tested (9 of 9) had a substantial fraction (producing > 50% inhibition) of anti-GBM antibodies expressing Id-GBM. The results indicate that shared determinants are expressed by anti-GBM antibodies from different individuals, and they raise the possibility that common genetic elements are used to encode them. These regions are potential targets for design of reagents to regulate autoreactive B cells and/or interfere with pathogenic antibody-GBM interactions, in individuals with anti-GBM antibody mediated diseases.     

Glomerular basement membrane. Identification of a novel disulfide-cross-linked network of alpha3, alpha4, and alpha5 chains of type IV collagen and its implications for the pathogenesis of Alport syndrome

Glomerular basement membrane (GBM) plays a crucial function in the ultrafiltration of blood plasma by the kidney. This function is impaired in Alport syndrome, a hereditary disorder that is caused by mutations in the gene encoding type IV collagen, but it is not known how the mutations lead to a defective GBM. In the present study, the supramolecular organization of type IV collagen of GBM was investigated. This was accomplished by using pseudolysin (EC 3.4.24.26) digestion to excise truncated triple-helical protomers for structural studies. Two distinct sets of truncated protomers were solubilized, one at 4 degrees C and the other at 25 degrees C, and their chain composition was determined by use of monoclonal antibodies. The 4 degrees C protomers comprise the alpha1(IV) and alpha2(IV) chains, whereas the 25 degrees C protomers comprised mainly alpha3(IV), alpha4(IV), and alpha5(IV) chains along with some alpha1(IV) and alpha2(IV) chains. The structure of the 25 degrees C protomers was examined by electron microscopy and was found to be characterized by a network containing loops and supercoiled triple helices, which are stabilized by disulfide cross-links between alpha3(IV), alpha4(IV), and alpha5(IV) chains. These results establish a conceptual framework to explain several features of the GBM abnormalities of Alport syndrome. In particular, the alpha3(IV). alpha4(IV).alpha5(IV) network, involving a covalent linkage between these chains, suggests a molecular basis for the conundrum in which mutations in the gene encoding the alpha5(IV) chain cause defective assembly of not only alpha5(IV) chain but also the alpha3(IV) and alpha4(IV) chains in the GBM of patients with Alport syndrome.     

Quantitative analysis of Na+ and Ca2+ current contributions on spike initiation in the newt olfactory receptor cell

The developmental localization patterns of collagen type IV alpha1-5 chains, laminin-1, laminin-5, and laminin alpha2 chain were analyzed in the embryonic mouse eye using isoform specific antibodies and immunofluorescence microscopy. Laminin-1 isoform and alpha1-2(IV) were ubiquitously expressed along the ocular surface basement membranes at a very early stage of eye development. Alpha3-5(IV) were first detected at later stages of development, and exhibited a variable distribution pattern along the ocular surface basement membrane. In contrast, expression of the laminin alpha2 chain was restricted to the conjunctival basement membrane, and was first detected during the same developmental period in which keratin K4-positive, differentiated conjunctival epithelial cells were observed. Although laminin-5 was uniformly expressed along the adult ocular surface basement membrane, during embryogenesis it was first incorporated into the conjunctival basement membrane structure. These data suggest that some of the laminin isoforms, including laminin alpha2 and laminin-5, may play a role in the formation of a conjunctival-type basement membrane. The temporal relationship between the localization of these molecules to the conjunctival basement membrane and the appearance of differentiated conjunctival epithelial cells suggests a role for external influence on the differentiation pathways of ocular surface epithelium.     

Diabetic pigmented spots on the extrapretibial region: immunohistochemical study of type IV collagen in dermal vessel wall

A case of diabetes mellitus associated with multiple pigment spots is reported. The patient had multiple pigmented atrophic patches on the abdominal area and thighs. There were no pigmented spots on the pretibial area. Histologically, dermal vessels showed intimal thickening and deposition of periodic acid-Schiff (PAS)-positive fibrillar material in vessel walls. Clinical and histological features indicated that these pigment spots were diabetic pigmented pretibial patches occurring in the extrapretibial area. Immunohistochemical studies of lesional and non-lesional skin using the antibodies for alpha1-alpha6 chains of type IV collagen revealed that PAS-positive material of vessel walls in both lesional and non-lesional skin was stained with alpha1 and alpha2 chain antibodies but not with alpha3-alpha6 chain antibodies, indicating that alpha1 and alpha2 chains of type IV collagen, which are normal components of the dermal vessel basement membrane, accumulate in the vessel walls in diabetes mellitus.     

Nonenzymatic glycation of type IV collagen and matrix metalloproteinase susceptibility

The glomerular basement membrane (GBM) is damaged in diabetes through complex mechanisms that are not fully understood. Prominent among them is nonenzymatic protein glycation leading to the formation of so-called advanced glycation end products (AGEs). We examined the effects of in vitro glycation of intact collagen type IV in bovine lens capsule (LBM) and kidney glomerular (GBM) basement membranes on their susceptibility to matrix metalloproteinases, using stromelysin 1 (MMP-3) and gelatinase B (MMP-9). Sites of cleavage of unmodified LBM collagen were located in the triple helical region. In vitro glycation by glucose severely inhibited the release of soluble collagen cleavage peptides by MMP-3 and MMP-9. The distribution of AGEs within the three domains of collagen IV (7S, triple helical, and noncollagenous NC1) were compared for LBM glycation using AGE fluorescence, pentosidine quantitation, and immunoreactivity towards anti-AGE antibodies that recognize the AGE carboxymethyllysine (CML). Marked asymmetry was observed, with the flexible triple helical domain having the most pentosidine and fluorescent AGEs but the least CML. The in vivo relevance of these findings is supported by preliminary studies of AGE distribution in renal basement membrane (RBM) collagen IV domains from human kidneys of two insulin-dependent diabetics and one normal subject. Pentosidine and fluorescent AGE distributions of diabetic RBM were similar to LBM, but the CML AGE in diabetic kidney was less in the triple helical domain than in NC1. Our results support the hypothesis that nonenzymatic glycation of collagen IV contributes to the thickening of basement membranes, a hallmark of diabetic nephropathy.     

Alport syndrome with neurofibromatosis type-I: a case report

We report a 9-year-old boy with repeated fractures of the tibia from age 6 months and microscopic hematuria from age 2 years. His maternal family has a history of nephritis and his paternal family has neurofibromatosis type-I (NF-I). The boy's renal biopsy revealed an irregular attenuation and splitting of the glomerular basement membrane. The skin biopsy was stained with monoclonal antibody against the alpha 5 chain of type IV collagen; the epidermal basement membrane was negative in the boy and segmentally positive in the boy's mother. We conclude that the patient inherited Alport syndrome from his mother and NF-I from his father. We postulate this was a chance association and that this case does not suggest any relationship between the two diseases.     

A novel variant of acquired epidermolysis bullosa with autoantibodies against the central triple-helical domain of type VII collagen

Epidermolysis bullosa acquisita and bullous systemic lupus erythematosus are autoimmune bullous disorders, with tissue-bound and circulating autoantibodies reactive with the noncollagenous NC1 domain of type VII collagen (C-VII). Here, we describe a novel acquired bullous dermatosis with autoantibodies against the triple-helical domain of C-VII. Three patients, all Japanese children, presented with widespread inflammatory tense blisters. Histologically, subepidermal tissue separation was noted with inflammatory infiltrate in the superficial dermis. Direct immunofluorescence staining revealed linear IgG/C3 deposits along the dermal-epidermal junction. Circulating IgG anti-basement membrane zone autoantibodies stained the dermal side of normal skin separated with 1 M NaCl. Direct and indirect immunoelectron microscopy using colloidal gold labeling showed that patient sera reacted with anchoring fibrils. The gold particles were localized both near the lamina densa and on the central banded portion of the fibrils. The sera reacted with C-VII in immunoblots. Epitope analyses with natural and recombinant fragments of C-VII disclosed that the sera did not recognize the NC1 domain of C-VII, but the central triple-helical domain of this anchoring fibril protein. Thus, the present probands show a hitherto unrecognized variant of epidermolysis bullosa acquisita, with autoantibodies against epitopes in the collagenous domain of C-VII.     

Expression of type IV collagen in the developing human kidney

The distribution of alpha1-6 chains of type IV collagen (alpha1-6(IV)) in human fetal kidneys was examined by indirect immunofluorescence. By 11 weeks of gestation, alpha1, 2, 3, 4, and 6(IV) were already present, but alpha5(IV) appeared relatively late, at 21 weeks. Alpha1(IV) and alpha2(IV) were present in all basement membranes, alpha3(IV) and alpha4(IV) were restricted to the glomerular basement membrane and parts of the tubular basement membrane. Alpha5(IV) was distributed in the glomerular basement membrane, Bowman's capsule, and parts of the tubular basement membrane. Alpha6(IV) was present in the Bowman's capsule, parts of the tubular basement membrane, and occurred in parts of the glomerular basement membrane at the early capillary loop stage, but disappeared during the later capillary loop stage.     

Alport syndrome. A review of the ocular manifestations

Alport syndrome has a prevalence of 1/5000, and 85% of patients have the X-linked form, where affected males develop renal failure and usually have a high-tone sensorineural deafness by the age of 20. The typical ocular associations are a dot-and-fleck retinopathy which occurs in about 85% of affected adult males, anterior lenticonus which occurs in about 25%, and the rare posterior polymorphous corneal dystrophy. The retinopathy and anterior lenticonus are not usually demonstrated in childhood but worsen with time so that the retinal lesion is often present at the onset of renal failure, and the anterior lenticonus, later. The demonstration of a dot-and-fleck retinopathy in any individual with a family history of Alport syndrome or with end-stage renal disease is diagnostic of Alport syndrome. The presence of anterior lenticonus or posterior polymorphous corneal dystrophy in any individual is highly suggestive of the diagnosis of Alport syndrome. Additional ocular features described in X-linked Alport syndrome include other corneal dystrophies, microcornea, arcus, iris atrophy, cataracts, spontaneous lens rupture, spherophakia, posterior lenticonus, a poor macular reflex, fluorescein angiogram hyperfluorescence, electrooculogram and electroretinogram abnormalities, and retinal pigmentation. All mutations demonstrated to date in X-linked Alport syndrome have affected the COL4A5 gene which encodes the alpha 5 chain of type IV collagen. This protein is probably common to the basement membranes of the glomerulus, cochlea, retina, lens capsule, and cornea. However, the alpha 3(IV) and 4(IV) as well as the alpha 5(IV) collagen chains are usually absent from the affected basement membranes, because the abnormal alpha 5(IV) molecule interferes with the stability of all three. The loss of these collagen molecules from the affected basement membranes results in an abnormal ultrastructural appearance. The ocular and other clinical features of autosomal recessive Alport syndrome are identical to those seen in X-linked disease, while retinopathy and cataracts are the only ocular abnormalities described in the rare autosomal dominant form of Alport syndrome. There are no ocular associations of thin basement membrane disease which is a common disease that probably represents the heterozygous expression of X-linked or autosomal recessive Alport syndrome.