Influence of the major histocompatibility complex on age at onset of chronic lymphoid leukaemia

Goodpasture syndrome is an often fatal autoimmune disease associated with glomerulonephritis and/or pulmonary hemorrhage. The clinical manifestations of this disease correlate well with the presence of circulating antiglomerular basement membrane (GBM) autoantibodies. The primary target antigen in glomerular and alveolar basement membranes is thought to be the alpha 3 chain of type IV collagen. Nearly all that is known about anti-GBM antibodies in humans comes from work on unbound circulating antibody. We recently had the unique and rare opportunity to obtain early postmortem antibody and tissues from a patient who died with catastrophic Goodpasture syndrome. The specificity of circulating, kidney-bound and lung-bound autoantibodies from this patient was evaluated against a variety of purified basement membrane constituents. The results indicate that the primary target for the circulating and tissue-bound autoantibodies is the NC1 domain of the alpha 3(IV) chain of type IV collagen. Additionally, all the antibodies recognize a cryptic epitope/s on the alpha 3(IV)NC1 hexamer. Furthermore, tissue-bound and circulating antibodies compete with one another for overlapping epitopes on the antigen. These findings demonstrate that circulating autoantibodies in Goodpasture syndrome are highly representative of those bound to organ tissues, strengthening the notion that pathogenic autoantibodies are targeted to the alpha 3(IV)NC1 collagen, and that previous reports of findings in the circulation may be applicable to tissue injury.     

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.     

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.     

Differential effects of estrogen metabolites on bone and reproductive tissues of ovariectomized rats

A total of 108 patients affected by Alport's syndrome, taken from 97 families, were enrolled in a genetic and ultrastructural study. Sixty-four families (75 patients) were X-linked, seven autosomal recessive, two autosomal dominant, five uninterpretable, and 19 sporadic. The ultrastructural features were consistent with Alport's syndrome in 66, doubtful in 20, and not significant for Alport's syndrome in 22 patients in the X-linked, sporadic, and genetically uninterpretable groups (without significant differences), as well as in the autosomal group. Mutations of the COL4A5 gene were present in 36 patients in the first three groups, without significant differences. More severe mutations were more frequently present in patients with an ultrastructural pattern consistent with Alport's syndrome. Nevertheless, there seems to be no strict correlation between mutation and ultrastructure, because a major rearrangement was found in a patient with no significant lesions, and different morphologic patterns were detected in patients Belonging to the same family. Immunohistochemical investigation into 24 patients for alpha (IV) chains showed that both alpha 3(IV) and alpha 5(IV) were lacking in the glomerular basement membrane of 13 patients (five with mutations) and were expressed in another six (three with mutations and one in the autosomal group). On the contrary, in this study the retained expression of alpha 3(IV) chain was found, despite the lack of alpha 5(IV) in the glomerular basement membrane of five patients (two with mutation). These different patterns could be related to both the type and severity of the COL4A5 mutations. All of the ultrastructural patterns were identified in all three immunohistochemical groups. Ultrastructural features and alpha 5(IV) chain production, even if an expression of a genetic mutation, do not strictly correlate. The combined use of analysis of collagen expression and electron microscopy made it possible to diagnose Alport's syndrome in 92% of the cohort, and therefore this approach is advisable. A multidisciplinary approach is recommended in the study of Alport's syndrome in an attempt to achieve a better diagnostic definition of and insight into the pathogenetic mechanisms.     

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.     

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.     

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.     

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.     

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.     

Inherited diseases of the glomerular basement membrane

The inherited diseases of the glomerular basement membrane include Alport's syndrome (AS), nail-patella syndrome, and thin basement membrane nephropathy. Classical AS is inherited in an X-linked manner and accounts for approximately 85% of the cases. Its manifestations include hematuria, sensorineural hearing loss, ocular defects, and a progression to renal failure. A defect(s) in the alpha 5 (IV) chain of type IV collagen is believed to be the etiology of classic AS, and alterations in its encoding gene localized to the X-chromosome have been elucidated. Although isolated cases of anti-glomerular basement membrane glomerulonephritis have been reported following renal transplantation in patients with AS, it is considered an effective form of renal replacement therapy. Less is known regarding the genetic basis of the autosomal-dominant form of AS, which apparently accounts for the remaining 15% of the cases. Nail-patella syndrome is characterized by nail dysplasia, patellar hypoplasia or aplasia, and nephropathy. It is inherited in an autosomal-dominant fashion with the gene locus assigned to the long arm of chromosome 9. Possible linkage between the COL5A1 gene and the gene for nail-patella syndrome has been suggested. Approximately 30% of the patients progress to end-stage renal failure. Renal transplantation has been successful in treating patients who progress to end-stage renal failure. Thin basement membrane nephropathy is an autosomal dominant trait that accounts for approximately 30% of the cases presenting as persistent, asymptomatic hematuria. The cause of thin basement membrane nephropathy is unknown at present. No decline in renal function is associated with thin basement membrane nephropathy.     

Expression of laminin alpha 1, alpha 5 and beta 2 chains during embryogenesis of the kidney and vasculature

Laminins, found predominantly in basement membranes, are large glycoproteins consisting of different subsets of alpha, beta and gamma chain subunits. To resolve conflicting data in the literature concerning coexpression of alpha 1 and beta 2 chains, expression of alpha 1 chain was studied with two different antisera against the E3 fragment of laminin alpha 1 chain. Expression of the alpha 1 chain was seen in several types of epithelial basement membranes throughout development, but its expression in rat glomerular basement membranes and some other types of epithelial basement membranes occurred only during early stages of development. By contrast, beta 2 chains were detected by immunofluorescence only during advanced stages of glomerulogenesis and vascular development. By Northern and Western blots, beta 2 chains were detected somewhat earlier, but in situ hybridization revealed that beta 2 chain was also confined to vasculature during the earlier stages. It thus seems that, in the tissues studied here, the expression of alpha 1 and beta 2 chains was mutually exclusive. To explore whether the newly described alpha 5 chain is expressed in locations lacking alpha 1 chain, expression of alpha 5 chain was studied by Northern blots and in situ hybridization. The alpha 5 chain was not uniformly expressed in all embryonic epithelial cell types but was present mainly in epithelial sheets which produce very little alpha 1 chain. There also appeared to be a developmental trend, with alpha 1 chain appearing early and alpha 5 later, in maturing epithelial sheets. The alpha 5 chain could be a major alpha chain of the adult glomerular basement membrane.     

Differential expression of five laminin alpha (1-5) chains in developing and adult mouse kidney

The nature of the laminin alpha chains in the embryonic and adult kidney is still being debated. The present study attempted to clarify this issue by immunofluorescence study using monoclonal antibodies against mouse alpha1, alpha2, and alpha5 chains and in situ hybridization for the alpha2, alpha3B, alpha4, and alpha5 mRNAs. Novel alpha1 chain-specific monoclonal antibodies against E8 fragment revealed a restricted distribution of alpha1 chain in a subset of epithelial basement membranes in the embryo, in agreement with previous mRNA data. The alpha2 mRNA was produced by mesenchyme, although the protein was deposited in epithelial basement membranes. The alpha3B mRNA was found only in a small subset of endothelial cells. The alpha4 mRNA was found transiently in embryonic mesenchyme, with particularly high levels in condensed mesenchyme, close to the tips of the ureteric tree where tubulogenesis is initiated. The alpha5 mRNA was strongly expressed by ureter epithelium but not expressed at early stages of tubulogenesis. Immunofluorescence verified low levels of the alpha5 chain in the early stages of tubulogenesis. However, during the capillary loop stage, the alpha5 chain became strongly expressed in the developing glomerular basement membrane, which matches the in situ hybridization results. During subsequent maturation of the kidney, the alpha5 chain became ubiquitously expressed in basement membranes. Overall, the alpha5 chain exhibited the broadest pattern of expression, followed by the alpha1 chain, particularly in the adult stage. These chains were the only ones produced by epithelial cells. Although some basement membranes contained several alpha chains, we failed to detect any of the five studied chains in some basement membranes. Thus, the identity of the alpha chains of many embryonic kidney blood vessels and several basement membranes in the inner medulla in the developing and adult kidney remain unclear.     

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.     

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.     

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.     

Glomerular endothelial cells synthesize collagens but little gelatinase A and B

Mesangial sclerosis is a major feature of progressive renal disease. The mesangium contains mesangial cells and is bounded by the peripheral glomerular basement membrane and endothelial cells. Mesangial cells synthesize and degrade extracellular matrix. Whereas both mesangial and endothelial cells synthesize extracellular matrix components, the degradative pathway, well studied in the former, has not been investigated in endothelial cells. This study examines lines of all three glomerular cell types derived from female B6SJLF1/J mice, as well as mRNA levels for collagens alpha1(I), alpha1(IV), alpha3 (IV), alpha5 (IV), and alpha1 (VI), laminin, tenascin, matrix metalloproteinase-2 (MMP-2), and MMP-9. Type I and IV collagen synthesis was confirmed by enzyme-linked immunosorbent assay. MMP-2 and MMP-9 enzyme activity was measured by zymography. It was found that glomerular endothelial cells are a significant source of collagens, laminin, and tenascin. However, they express only low levels of MMP-2 and no detectable MMP-9. Stimulation with exogenous transforming growth factor-beta1 leads to a significant increase in collagen I, tissue inhibitors of metalloproteinase-1, and MMP-9 in conditioned media. These data suggest that glomerular endothelial cells may play an active role in extracellular matrix remodeling in glomerular disease.     

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.     

Tissue distribution of amyloid P component as defined by a monoclonal antibody produced by immunization with human glomerular basement membranes

A monoclonal antibody reactive against amyloid P component (NCL-AMP) has been developed following immunization of mice with partially-purified human glomerular basement membranes (GBM) and standard hybridization and cloning techniques. The antibody reactivity was evaluated by enzyme-linked immunosorbent assay (ELISA) and by the indirect immunoperoxidase technique on sections of frozen and fixed human kidney and other tissues. The distribution of amyloid P component in various normal tissues is described and the possible co-localization with the Goodpasture antigen is discussed. In addition, the suitability of the antibody for detection of amyloid deposits in renal amyloidosis is demonstrated and its potential for use in other pathological conditions is considered.