The immunohistology of glomerular antigens. IV. Laminin, a defined noncollagen basement membrane glycoprotein

Serum laminin and basic fibroblast growth factor concentrations in patients with complicated Plasmodium falciparum malaria

Serum concentrations of laminin and basic fibroblast growth factor (FGF) were measured in 20 patients suffering from complicated Plasmodium falciparum malaria in Bangkok. Significant higher mean serum concentrations of laminin were determined prior to treatment (1973 ng/ml) and 7 days after starting medication (1025 ng/ml) in comparison to the control (412 ng/ml). The values remained numerically higher for at least 21 days. With regard to serum basic FGF concentrations, a peak was found 7 day after starting treatment (35.61 pg/ml). In addition, a significant correlation was found for parasite clearance time and basic FGF concentration on day 7 (P < 0.01). These increased values of laminin and basic FGF may be the consequence of endothelial and basement membrane damage induced by sequestration of the parasites. Furthermore, basic FGF might play a role in endothelial repair mechanisms after the clearance of the parasites.

Glomerular distribution of type IV collagen in diabetes by high resolution quantitative immunochemistry

We examined type IV collagen distribution and density in human diabetic kidneys by quantitative immunogold electron microscopy. We studied normal kidney transplant donors and "slow-track" and "fast-track" insulin dependent diabetic (IDDM) patients. The "slow-track" patients had IDDM for > or = 20 years and mesangial volume fraction (VvMes/glom) of < or = 0.32. The "fast-track" patients had IDDM for < or = 20 years and VvMes/glom > or = 0.37. Renal biopsies were embedded in Lowicryl, reacted with polyclonal anti-type IV collagen (in the distribution of the classical alpha 1(IV) and alpha 2(IV) collagen chains) and monoclonal anti-alpha 4(IV) collagen chain antibody followed by gold conjugated secondary antibody. We found, by morphometric techniques, a decrease in the immunogold densities of anti-type IV collagen in the subendothelial zone of the GBM in the "fast-track" IDDM patients. There was a trend towards a decrease in mesangial matrix (MM) particle density in the "fast-track" (P = 0.07) but not in the "slow-track" patients. However, because of the marked increase in MM in the "fast-track" patients, the per glomerulus estimated quantity of these antigens in MM was increased. In contrast, the density of alpha 4(IV) collagen chain was increased in the epithelial zone of the GBM in the "fast-track" IDDM patients. It is not known whether these changes in glomerular type IV collagen represent markers of advanced diabetic lesions or whether these changes might be detected earlier in diabetic patients destined for the later development of serious lesions.

Fibronectin and basement membrane components in renal amyloid deposits in patients with primary and secondary amyloidosis

Kidney biopsies from one patient with primary (AL) and three with secondary (AA) amyloidosis were used for an ultrastructural study of the collocalization of basement membrane proteins and the extracellular matrix protein fibronectin within amyloid deposits. Antibodies against amyloid P component, laminin, and heparan sulphate proteoglycan core protein all reacted with the basement membranes and the amyloid depositions in AA and AL amyloidosis. Monoclonal and polyclonal antibodies against collagen type IV reacted only with the basement membranes. Anti-fibronectin reaction was found in association with the basement membranes in all four cases, while labelling of amyloid depositions was found only in one of the AA amyloid cases and in the AL amyloid depositions. It is concluded that basement membrane components may be of importance for the formation of amyloid fibrils.

The structure of the normal human glomerular basement membrane. Ultrastructural localization of type IV collagen and laminin

Structural models of the glomerular basement membrane (GBM) have been based solely on the localization of antigens in animal kidneys. These models depict a type IV collagen lattice as the structural skeleton along the central portion of the membrane, with the glycoprotein laminin attached predominantly in the laminae rarae where it is thought to be involved with endothelial and visceral epithelial cell attachment. The human GBM is also known to contain type IV collagen and laminin. The present study localizes both of these structural antigens in normal human GBM using the ultrastructural immunogold technique. Type IV collagen is situated in the sub-endothelial third of the GBM and is continuous with the type IV collagen within the mesangial matrix. Laminin is localized throughout the entire thickness of the GBM and mesangial matrix. These results indicate that the structure of human GBM is significantly different from that proposed in animal models. A structure for the normal human GBM is discussed, depicting a thin type IV collagen lattice which is asymmetrically placed in the sub-endothelial third of the membrane, with laminin distributed as an integral component of the membrane in addition to its role in cell attachment.

Basement membrane collagen in the kidney: regional localization of novel chains related to collagen IV

Variability in the collagen chain composition of renal basement membranes was demonstrated by immunofluorescent microscopy using polyclonal and monoclonal antibodies and correlating with imaging of the glomerular basement membrane by phase microscopy. Antibodies toward the globular domains of alpha 1(IV) and alpha 2(IV) collagen chains, triple helical and 7S domains of collagen IV bind within the glomerulus to mesangial matrix, along the subendothelial region of the glomerular capillary wall, and to all tubular and vascular basement membranes. The portion of glomerular basement membrane corresponding to the phase dense image is not reactive with these antibodies. A different binding pattern is seen with antibodies against two novel globular regions of basement membrane collagen chains which bind to the phase dense aspect of glomerular basement membrane and to Bowman's capsule. Human tubular basement membrane is not reactive, except along portions of the distal tubule, whereas bovine tubular basement membrane is diffusely reactive; mesangial matrix and extraglomerular vascular basement membranes are not reactive. Although a possible explanation for the regional distribution of basement membrane collagen antigens in the glomerulus may relate to antigen exposure, a more likely reason is that collagen chains are regionally expressed. The staining patterns suggest that the novel collagen chains have a selective tissue distribution compared with alpha 1(IV) and alpha 2(IV) chains and that the glomerular cells of origin of these collagen IV chains may differ.

A murine nephritogenic monoclonal anti-DNA autoantibody binds directly to mouse laminin, the major non-collagenous protein component of the glomerular basement membrane

The interaction of the murine monoclonal anti-DNA antibody H241 with extracellular glomerular antigens was found to be due to the binding of this antibody to laminin, the major non-collagenous protein constituent of the glomerular basement membrane. This interaction is specific, since it is inhibited by laminin, double-stranded DNA and single-stranded DNA in solution. Furthermore, the binding of H241 to mouse laminin is mediated by conformational properties of the antigen because mild denaturation of laminin strongly decreases the binding capacity of H241, while exposure of laminin to sodium dodecyl sulfate, completely abolishes this interaction. H241 is able to bind to both, human and mouse laminin. These findings are in agreement with the ligand binding specificities of the autoantibodies spontaneously produced, that differ from those generated by artificial immunization. We conclude that the polyreactivity of H241 that confers to it the capacity to bind laminin, may account for its ability to form immune deposits by binding directly to non-DNA glomerular antigens.

Differentiation properties of renal collecting duct cells in culture

In the present study, we were particularly interested in distinguishing specific patterns of structural and functional proteins in the collecting duct system of neonatal and adult kidneys and in cultured renal collecting duct epithelia in order to ascertain the degree of differentiation in the cultures. We studied the distribution of specific renal collecting duct cell markers using morphological, immunohistochemical and biochemical procedures. Cultured renal collecting duct epithelium undergoes maturation in vitro. Examples of morphological differentiation include the appearance of cilia and microvilli at the apical cell pole, and a basement membrane at the basal aspect of the epithelium. Tight junctions with five to seven strands separate the wide intercellular spaces from the apical cell surface. Physiological maturation from a 'leaky' to a 'tight' epithelium is evident from the acquisition of the alpha-subunit of Na/K-ATPase and the development of a high transepithelial potential difference and resistance. Biochemical differentiation is revealed by the expression of specific proteins. The simple-epithelium cytokeratins, PKK1 and PKK2, which are typical intracellular-matrix proteins of mature collecting duct epithelium, maintain the same distribution in cell culture as in neonatal and adult kidneys. An indicator of maturation in vitro is the expression of the collecting duct-specific proteins, PCD2 and PCD3. Newly developed monoclonal antibodies against these antigens reacted similarly with cultured cells and cells of the mature collecting duct system, but they did not label the embryonic ampullae in the cortex of neonatal rabbit kidneys. In contrast, a third collecting duct-specific protein, PCD1, is not expressed by the cultured cells, which indicates the retention of an embryonic characteristic in vitro. Embryonic collecting duct ampullae of the neonatal kidney in situ contain laminin during their development. Laminin is, however, absent in cultured collecting duct epithelium. Biochemical stimulation of the adenylate cyclase system by arginine vasopressin resulted in a twofold stimulation of the enzyme activity. This degree of stimulation is similar to that found in maturing kidneys of neonatal rabbits and indicates another embryonic feature of the cultures.

Immunohistochemical localization of glomerular basement membrane antigens in various renal diseases

The immunofluorescent localization of glomerular basement membrane (GBM) antigens was examined in 52 specimens from normal kidneys and in various renal diseases using antisera to human GBM (HGBM), IV type collagen (IV Col) and P3 antigen, a rat nephritogen. Anti-HGBM serum normally stained the GBM and the mesangium in a restrictive pattern, anti-IV Col serum stained the GBM and the mesangium in a wider pattern and anti-P3 serum stained only the GBM. In mesangial proliferative glomerulonephritis, including IgA nephropathy and Henoch-Schönlein nephritis, the widened mesangial areas were stained with anti-HGBM and anti-IV Col sera. In membranous nephropathy, the punched-out lesions of thickened GBM were demonstrated with the three antisera in moderate cases and a double linear distribution with fine granulation with anti-HGBM and anti-IV Col sera were revealed in one severe case. In membranoproliferative glomerulonephritis, the expanded mesangium and thickened capillary walls were stained with anti-HGBM and anti-IV Col sera, while the outer line of glomerular capillary walls was only positive with anti-P3 serum. In crescentic glomerulonephritis, the collapsed glomerular tufts were stained normally with anti-HGBM and anti-P3 sera and weakly with anti-IV Col serum. In diabetic nephropathy, anti-HGBM serum stained the GBM in a double linear distribution without reacting with the expanded mesangium; anti-IV Col serum stained the mesangium and the GBM in a less clear double linear fashion while anti-P3 serum stained the GBM as single line. Thin membrane disease and Alport's syndrome had normal reactivity with all antisera. However, in one case of Alport's syndrome anti-HGBM and anti-P3 sera stained the GBM in a focal and segmental pattern, while normal staining with anti-IV Col serum was found. In lesions with adhesions and crescents the staining was positive for HGBM and IV Col and negative for P3; obsolescent glomeruli were stained with anti-HGBM and anti-P3 sera, and had diminished staining with anti-IV Col serum. The identification of the various structural glomerular antigens is useful in the classification of certain types of glomerular diseases. Further insight into the mechanisms underlying these conditions may be obtained in this way.

Localization and distribution of anionic charges in the glomerular mesangium of normal and nephrotic rats

Sulfated glycosaminoglycans and sialoglycoproteins are thought to play a pivotal role in the glomerular capillary wall barrier to filtration since these anionic charged elements are important in the maintenance of capillary wall integrity and constitute a charge-selective filter. The development of proteinuria in puromycin aminonucleoside (PAN) nephrosis is associated with polyanion loss from the glomerular capillary wall structures. Since in PAN nephrosis the permeability of the mesangial area to plasma proteins and tracer substances has also been shown to be increased, the purpose of this study was to analyse the localization and distribution of anionic charges in the glomerular mesangium in this experimental model. Glycosaminoglycans were labeled by perfusion of the kidneys with ruthenium red solution (RR). Electron microscopic examination revealed the presence of distinct small RR granules ("anionic sites") in the mesangial intercellular matrix substance and in the laminae rarae of the glomerular basement membrane (GBM). The center-to-center spacing of the granules was measured and a frequency distribution of intervals in different interval classes was constructed. In normal glomeruli the anionic sites in the mesangial matrix showed a distribution pattern identical to the GBM with a maximal interval incidence at the 31-40 nm class. In nephrotic rats anionic site distributions in matrix and GBM did not change significantly. Sialoglycoproteins were labeled with colloidal iron (CI). In PAN nephrosis a decrease of CI binding was observed at the epithelial-basement membrane junction of the glomerular capillary wall. However, CI labeling of the mesangial matrix and mesangial cell membranes did not differ from that of normal glomeruli.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding of platelet factor four (PF 4) to glomerular polyanion

Synthetic polycations have been shown to bind to glomerular polyanion (GPA) and increase glomerular permeability. Here, we show that human platelet factor 4 (PF 4), a platelet secretory protein, binds to GPA. The following methods were used to assess PF 4 binding to GPA: (1) Sections of human and rat renal cortex were incubated with PF 4 or PF 4 was injected intravenously into rats followed by immunofluorescence techniques; (2) 125I-PF 4 was added to isolated glomerular basement membrane (GBM) suspensions and binding assessed isotopically; (3) PF 4 was perfused through rat kidneys ex vivo followed by immunoperoxidase methods for electron microscopy (EM). In vitro and in vivo, PF 4 bound to the mesangium and linearly to capillary walls. Isotopic studies showed dose-dependent saturable binding of PF 4 to GBM which was reversed by heparin. By EM, PF 4 binding sites were resolved in the GBM, particularly in the laminae rarae as punctate densities similar in distribution to anionic sites revealed by cationic dyes. Also, endothelial and epithelial cell surfaces stained. An ionic interaction between PF 4 and GPA was indicated by elimination of staining by washing PF 4-treated sections with buffer containing 1.0 and 3.0 M NaCl or with heparin. Pretreatment of rats with polyethyleneimine (a synthetic polycation) blocked PF 4 binding. Heparin administration in vivo removed previously bound PF 4. By virtue of its affinity for GPA and behavior like a polycation, PF 4 may alter glomerular permeability and play a role in glomerular disease.

Simultaneous anti-glomerular basement membrane and membranous glomerulonephritis: case report and literature review

A 20-year-old male experienced a sore throat, fever, and lumbar pain. Examination revealed haematuria, proteinuria, and transiently impaired renal function. Renal biopsy revealed minor mesangial widening and small cellular crescents in 20% of the glomeruli under the light microscope, whereas immunofluorescence showed bright, linear staining of IgG along the glomerular basement membrane (GBM). Ultrastructural analysis showed minute subepithelial deposits analogous to early membranous glomerulonephritis (MGN). Anti-GBM antibodies were detected in the patient's serum. These findings were suggestive of simultaneous anti-GBM and immune complex glomerulonephritis in a patient with a mild, reversible renal illness.

Immune-mediated injury to basement membranes in mice immunized with murine laminin

Mice immunized with laminin isolated from mouse EHS sarcoma developed immune-mediated pathological changes in the basement membranes of the kidneys and lungs, and in the subendothelial basement membranes of arteries in the kidney. Subendothelial and mesangial dense deposits were seen in the renal glomerulus. Thickening and splitting of both the glomerular basement membrane and the alveolar basement membrane occurred in mice immunized with laminin. Granular dense structures were present in the lamina densa of subendothelial basement membranes of renal arteries. Staining for in vivo-bound mouse IgG was observed primarily along the glomerular basement membrane and in the mesangium by the indirect peroxidase technique. Mouse IgG was also detected in the adventitial connective tissue of renal arteries and was present focally along tubular basement membranes. No circulating antibody was detectable using either Western immunoblotting or microELISA techniques.

Production of monoclonal antibodies to fibronectin, type IV collagen and other antigens of the human glomerulus

A series of monoclonal antibodies to human glomerular antigens was prepared by immunisation of a mouse with isolated whole glomeruli, followed by boosting with particulate glomerular basement membrane and fusion of murine spleen cells with the NSI-myeloma line. Hybridoma supernatants were screened jointly by a radioimmunoassay involving binding to isolated glomeruli, and by a 4-layer immunoperoxidase technique applied to polyester wax-embedded sections. Seven monoclonal antibodies with different specificities (PHM7-PHM13) were established and repeatedly cloned. Each antibody displayed a distinctive distribution within the glomerulus, including different patterns of staining of mesangial cells, mesangial matrix and glomerular basement membrane, in addition to extra-glomerular basement membranes and extracellular matrix. All antibodies also stained cellular outgrowths of isolated glomeruli cultured in vitro, and showed additive binding to cultured cells by radioimmunoassay. Physical characterization using absorptions with purified substrates, plus specific chemical and enzymatic digestions, indicated that PHM12 is directed against type IV collagen. PHM13 is directed against fibronectin as shown by absorption with purified fibronectin and immunoprecipitation of a 220 000 MW glycoprotein. The remaining 5 monoclonal antibodies, which react with carbohydrate (PHM7) or protein (PHM8-PHM11) determinants, were shown to be nonreactive with type IV collagen, fibronectin or other known glomerular components including sialic acid, laminin, amyloid P-component or various glycosaminoglycans. These monoclonal antibodies therefore appear to define a new series of human glomerular antigens, or possibly closely related antigenic determinants, which are synthesized by glomerular cells and incorporated into the mesangium and glomerular basement membrane. These antibodies, by providing markers for at least 2 antigens known to be important in glomerular cell-matrix interactions, should prove useful in research into the mechanisms involved in renal pathology.

Immunocytochemical localization of a renal glycoprotein (gpCDI) synthesized by cultured collecting duct cells

A sulfated, proline-rich glycoprotein (gpCDI, apparent molecular weight 200,000 in column chromatography and 150,000 in SDS-PAGE) was isolated from cultured renal collecting duct epithelium by centrifugation. Triton X100 extraction and DEAE-cellulose ion exchange chromatography. A DEAE-cellulose ion exchange chromatography fraction with the enriched gpCDI was used for immunization of guinea pigs. The antiserum was prepared for antigen localization by indirect immunofluorescence in collecting duct cell cultures and in tissue sections of neonatal and adult rabbit kidneys. In the cultured collecting duct epithelium, antibody staining of the epithelium and structures of the extracellular matrix was age dependent. Cultures of dedifferentiated collecting duct monolayers revealed positive reaction in the cytoplasm. In neonatal and adult rabbit kidneys, the antibody was localized in the entire collecting duct system but not in the collecting duct ampullae of the newborn kidney. Staining of the cytoplasm was found only in medullary collecting ducts of the neonatal kidney; other portions revealed staining mostly at the basal circumference of the tubule and at the luminal cell borders. Apart from collecting ducts, no other tubular segments were reactive. The cortical and the medullary interstitium contained fluorescent fibres which were concentrated around vascular structures. A possible relation between gpCDI and collagenous compounds is discussed. Bowman's capsule reacted positively, whereas staining of the mesangial matrix was weak. The localization of the antigen, as revealed by indirect immunofluorescence, suggests that gpCDI occurs both in intracellular and extracellular (interstitial) location. Two main points are emphasized: Firstly gpCDI is considered an important constituent in different stages of collecting duct development, and secondly, the staining pattern of the antibody varies with the different portions of both young and adult kidney collecting ducts; this staining heterogeneity may correspond with the known regional differences of collecting duct functions.

Ultrastructural localisation of fibronectin in mouse kidney

The ultrastructural localisation of fibronectin in mouse kidney was investigated by indirect immunoperoxidase cytochemistry. In glomeruli, fibronectin was found predominantly in matrix between endothelial and mesangial cells. Smaller quantities were demonstrable in peripheral capillary walls both subendothelially and around visceral epithelial cell foot processes. It was present between parietal epithelial cells and Bowman's capsule and at the base of tubular epithelial cells outlining the inner aspect of tubular basement membranes.

Glomerular antigens in glomerulonephritis

Ideas on the immunopathogenesis of glomerulonephritis are evolving to embrace a concept of a dynamic and constantly fluctuating involvement of immune reactants in the production of glomerular inflammation. The glomerulus should be regarded as a template around which the antibody-induced inflammatory events that constitute glomerulonephritis are initiated. Such lesions may be produced by direct antibody attack on glomerular antigens of either intrinsic structural or "planted" type, as discussed in this review, or by the deposition of circulating soluble immune complexes containing extraglomerular antigens. These mechanisms are not mutually exclusive and both may play a role in some situations. Intrinsic glomerular antigens are being increasingly better defined as to site, structure, function, and experimental animal models of spontaneous and induced glomerular injury resulting from direct antibody binding to nonclassic GBM capillary wall antigens are available for study. Similar nonclassic GBM antigens are likely to be found of importance in man. Anti-GBM antibody-induced glomerulonephritis continues to be the best understood example of direct attack on the glomerulus by antibody, and its nephritogenic noncollagenous GBM antigenic constituents are being characterized. The incorporation of extraneous substances as "planted" antigens within glomerular structures is now recognized in experimental animal models, and there is suggestive evidence to support the concept in man. Emphasis needs to be placed on the continuing interplay of free antibody and antigen with deposited reactants which, together with complement components, modulate the quality and quantity of the glomerular immune deposits.

Proteinuria and structural alterations in rat glomerular basement membranes induced by intravenously injected anti-laminin immunoglobulin G

Antibodies against laminin, which is a defined glycoprotein of basement membranes, were produced in sheep and affinity purified by immunoadsorption on laminin-Sepharose (S alpha L). When injected intravenously into rats, S alpha L rapidly bound in a linear pattern to the glomerular basement membrane (GBM) in the peripheral and mesangial regions of all glomeruli, and, when greater than 0.5 mg S alpha L was injected, to some tubular BM as well. 1-2 h after the injection of conjugates of horseradish peroxidase (HRP) and S alpha L, HRP reaction product was present throughout the full thickness of the GBM and mesangial matrix. [125I]S alpha L binding to the kidney in vivo increased linearly over the dose range of 40-950 micrograms of IgG and accounted for approximately 2% of the injected dose/g kidney. When 4 mg of [125I]S alpha L was injected, 1.5% or 62 micrograms/g kidney was bound. Proteinuria did not develop within 7 wk of injection in rats that received 0.5-1.6 mg of S alpha L. In contrast, all animals that received injections of 4 mg of S alpha L gradually became proteinuric within 3-6 wk. Thickening, reduplication, and flocculent subendothelial deposits were observed in the GBM of these animals. In addition, mononuclear cells adhered to the GBM and infiltrated beneath the endothelium. However, the deposition of rat C3 was infrequently observed, and rat IgG was not seen in the glomeruli of any rat that received S alpha L. 10 wk after injection, much greater amounts of S alpha L appeared within the mesangium than the peripheral GBM. These results demonstrate that the interaction of S alpha L with the GBM, possibly in concert with infiltrating mononuclear cells, gradually altered the structure and permeability characteristics of the glomerulus independent of a host anti-S alpha L humoral response.

Preservation of mesangium and immunohistochemically defined antigens in glomerular basement membrane isolated by detergent extraction

To define the characteristics of isolated glomerular basement membrane (GBM), immunohistochemical and morphometric analyses have been carried out on rat and human tissues. Site-specific arrays of antigens were identified in detergent-isolated GBM in a distribution similar to that observed in intact kidney. In the human, fibronectin, procollagen IV, and collagen V were observed along the internal aspect of GBM continuous with antigenic sites in the mesangium. Another array of antigens was identified in the GBM but not within the mesangium--Goodpasture's antigen, bovine lens capsule type IV collagen, and amyloid P component. In addition, sites reactive with rabbit antiserum to laminin were present on both sides of the lamina densa as well as within the mesangial region. Actomyosin, a presumed mesangial cell antigen persisted in the mesangium of isolated GBM. Mesangial matrix was identified in detergent-isolated GBM in an amount equivalent to that present in intact glomeruli. Sonicated GBM contained the same antigens but it was not possible to quantitate the amount of mesangial material by immunofluorescence or morphometric analysis. The thickness of the lamina densa was greater in sonicated and detergent-treated rat GBM preparations than in native rat kidney. These studies demonstrated that isolated GBM is heterogeneous with respect to its antigenic constituents and in addition contains mesangial matrix, which is morphologically and immunohistochemically distinct from peripheral GBM.

Formation of basement membranes in the embryonic kidney: an immunohistological study

Specific antibodies to laminin, type IV collagen, basement-membrane proteoglycan, and fibronectin have been used in immunofluorescence microscopy to study the development of basement membranes of the embryonic kidney. Kidney tubules are known to form from the nephrogenic mesenchyme as a result of an inductive tissue interaction. This involves a change in the composition of the extracellular matrix. The undifferentiated mesenchyme expresses in the composition of the extracellular matrix. The undifferentiated mesenchyme expresses fibronectin but no detectable laminin, type IV collagen, or basement-membrane proteoglycan. During the inductive interaction, basement-membrane specific components (laminin, type IV collagen, basement membrane proteoglycan) become detectable in the induced area, whereas fibronectin is lost. While the differentiation to epithelial cells of the kidney requires an inductive interaction, the development of the vasculature seems to involve an ingrowth of cells which throughout development deposits basement-membrane specific components, as well as fibronectin. These cells form the endothelium and possibly also the mesangium of the glomerulus, and contribute to the formation of the glomerular basement membrane. An analysis of differentiation of the kidney mesenchyme in vitro in the absence of circulation supports these conclusions. Because a continuity with vasculature is required for glomerular endothelial cell differentiation, it is possible that these cells are derived from outside vasculature.

The biochemical properties of basement membrane components in health and disease

Basement membranes are complex macromolecular structures which occupy the extracellular space between cells of different histologic types. Biochemically it is composed of Type IV collagen, several noncollagenous glycoproteins including laminin, fibronectin, GP-2 and PYS glycoprotein, and heparan sulfate. Morphologic changes are commonplace in a number of renal diseases. In diabetic glomerular disease, the basement membrane is markedly thickened but the biochemical basis has not been elucidated. In other disease-associated basement membrane changes, altered glycosylation of glycoprotein components has been described. The most important issue is the effect such alterations have on the interaction of basement membrane components and the function of the basement membrane.

Amyloid P-component in human glomerular basement membrane. Abnormal patterns of immunofluorescent staining in glomerular disease

Serum amyloid P-component (SAP) is a normal plasma protein and is a constituent of normal human glomerular basement membrane. Immunofluorescence with anti-SAP antibody produced characteristic linear staining along the glomerular basement membrane in normal kidney. Distinctive abnormal staining patterns were seen in renal biopsy specimens from patients with diabetes, membranous glomerulonephritis, mesangiocapillary nephritis, systemic vasculitis, Goodpasture's syndrome.