Hybridomas reveal shared immunodominant epitopes of gamma-glutamyltransferase isoforms from human kidney and renal cell carcinoma

Metastatic renal cell carcinoma (RCC) is a tumor with a poor prognosis resistant to chemotherapy and irradiation. However, in rare cases, spontaneous regressions of metastases after nephrectomy have been reported that were ascribed to destruction of the tumor by the immune system. In earlier studies, we and others identified the expression of modified antigens in RCC. In particular, a concanavalin A-binding isoform of gamma-glutamyltransferase (gamma GT) comprises about 50% of the enzymatic activity found in the tumor tissue of many RCC patients. The monoclonal antibody 138H11, directed against all human gamma GT isoforms, revealed a membranous expression of gamma GT around RCC cells compared to the restricted, apical pattern of renal cells. These data raised the question why the RCC-specific gamma GT, exposed to the immune system in vivo, is not immunogenic in patients with RCC. To address this question, we generated mouse hybridomas against highly purified human RCC gamma GT. Although we obtained a large panel of hybridomas that produced antibodies reacting immunohistochemically in a gamma GT-specific manner, all antibodies stained normal kidney gamma GT as well as RCC gamma GT. These results suggest that the biochemical features specific for RCC gamma GT are not necessarily reflected by specific antigenic determinants that could be differentiated by the immune system of the challenged mice. The lack of immunogenic epitopes different from normal gamma GT enzyme may offer an explanation why gamma GT produced by RCC can escape immunological surveillance.

Monocyte cell-surface CD14 expression and soluble CD14 antigen in hemodialysis: evidence for chronic exposure to LPS

Expression of CD14 on peripheral blood monocytes and serum levels of the 53 kD soluble CD14 antigen were investigated in patients with end-stage renal failure who were undergoing chronic hemodialysis (HD) with either cuprophane/hemophane (CU/HE) low-flux (LF) or polysulfone/polyamide (PS/PA) high-flux (HF) membranes. Baseline expression of CD14 was significantly lower in HD patients compared to uremic patients and normal controls. Patients using PS/PA membranes disclosed a further decreased CD14 expression than patients with CU/HE membranes. Specific fluorescence intensity for CD14 increased 15 minutes after the start of the dialysis session and was on average 22% higher after hemodialysis. The serum levels of sCD14 were elevated about 2.5-fold in HD patients compared to healthy controls (5.4 +/- 1.3 vs. 2.2 +/- 0.5 mg/liter, P < 0.0001) and were significantly higher compared to non-dialyzed patients with chronic renal failure (3.9 +/- 1.0 mg/liter, P < 0.001). After regular dialysis with high-flux membranes, soluble CD14 serum concentrations significantly increased (P < 0.001) compared to pre-dialysis levels. Values of soluble CD8 (54 kD) were elevated only 1.5-fold in HD patients relative to healthy controls, whereas serum levels of the low molecular weight soluble CD23 (20 kD) 12 and 19-fold in patients treated with HF-HD and LF-HD, reflecting the renal impairment and filtration through HF membranes. Thus, high sCD14 values in HD patients may stem from increased release of the up-regulated membrane antigen due to monocyte activation during hemodialysis treatment. Since the CD14 antigen is involved in LPS-induced monocyte activation, the influence of lipopolysaccharide on CD14 expression and sCD14 release was investigated in vitro. Addition of 1 ng/ml or 0.01 ng/ml LPS to whole blood significantly enhanced monocyte CD14 expression after 30 or 60 minutes of incubation. The release of soluble CD14 by cultured peripheral blood monocytes significantly increased in the presence of 0.01 ng/ml LPS during a five-day incubation experiment. Our results demonstrate an enhanced expression of CD14 by monocytes after HD and increased sCD14 serum levels possibly due to chronic exposure to trace amounts of endotoxins, as supported by in vitro experiments.

Increased soluble CD14 serum levels and altered CD14 expression of peripheral blood monocytes in HIV-infected patients

Serum levels of soluble CD14 were elevated in HIV-infected asymptomatic patients or those with lymphadenopathy (CDC II/III) 2.9 +/- 0.8 mg/l compared with normal controls with 2.2 +/- 0.47 mg/l, P < 0.001. A further rise was seen in patients with ARC (CDC IVA) 3.8 +/- 1.1 mg/l, P < 0.01 and patients with AIDS (CDC IVB-D) 5.7 +/- 2.5 mg/l, P < 0.01. Although absolute numbers of CD14+ cells decrease in the AIDS group, the percentage of CD14+ monocytes did not change. In contrast, levels of soluble T cell antigens sCD4 and sCD8, which are higher in HIV-infected patients compared with normal subjects, showed no increase with disease progression. Serum levels of sCD14 were correlated positively with beta 2-microglobulin levels (rs = 0.63, P < 0.0001). Whereas the percentage of CD14+ monocytes did not change, an increase in monocytic CD14 expression in HIV-infected patients was observed (P < 0.01). The percentage of a monocyte subset expressing both CD14 and CD16 increased from 6% in normal healthy persons to 13% in HIV-infected patients (P < 0.001), and did not vary between the HIV patient groups. Incubation of cultured peripheral blood monocytes with azidothymidine had no effect on either normal or LPS-induced or IL-4-inhibited sCD14 release in vitro. Therefore, an effect of AZT on sCD14 serum values in vivo is considered to be unlikely. Our data further provide evidence that monocytes/macrophages are engaged in HIV infection.

Elevated levels of soluble CD14 in serum of patients with systemic lupus erythematosus

A soluble form of CD14 (sCD14) was assessed with an ELISA assay in the serum of the following three clinical groups: 35 patients with an inactive phase of systemic lupus erythematosus (SLE), 17 patients with SLE relapses, and 65 normal healthy volunteers. Increased levels of sCD14 were observed in all patients suffering from SLE compared with normal controls. In addition, patients with active SLE revealed higher serum concentrations of sCD14 (median 6.9 mg/l) than patients under remission (4.1 mg/l; P < 0.0001). Serum values of sCD14 correlated neither with the number of peripheral blood monocytes bearing the CD14 membrane antigen, nor with serum concentrations of IL-1 beta. Serum sCD14 was compared with other clinical parameters used to monitor the clinical course of patients with SLE, among them complement C3, anti-dsDNA antibodies and soluble IL-2 receptor (sIL-2R). A good correlation emerged between sCD14 and C3 as well as sIL-2R concentrations, but sCD14 and anti-dsDNA titres disclosed no significant correlation in both groups of patients with SLE. Serial studies in patients with severe SLE showed that serum sCD14 closely parallels the clinical course as defined by an activity score. Our data suggest that serum sCD14 represents a promising parameter to monitor disease activity in patients with SLE.

Shedding and repair of renal cell membranes following drug-induced nephrotoxicity in humans

Nephrotoxic drugs may account for approximately at least 20% of clinically observed cases of acute renal failure in whom tubular lethal or sublethal damage is a predominant finding. Acute toxic tubular cell injury is characterized by loss of cellular polarization, intrinsic energy deficiency, calcium overload, release of toxic proteases and free oxygen radicals, derangement of the cytoskeleton, and vacuolar transformation of brush border microvilli. These events may finally lead to irreversible cell death. Shedding of membrane enzymes and cytoskeletal components in urine (kidney tissue proteinuria) may serve as a noninvasive early marker for assessing tubular cell injury. Successful recovery of renal function depends on early repair of lethally or sublethally damaged nephrons, in which intrinsic nephrogenic adaptive and proliferative responses cooperate in concert with auto/para/-juxtacrine growth promoting factors and cytokines. Exogenously administered growth factors may enhance renal cell recovery, as shown in animal models. Increased expression of immediate early genes in tubular cells after renal injury reflects the ongoing mitogenic activity necessary for reepithelialization and remodeling (new, polarized, differentiated cells). Further progress in understanding the molecular mechanisms of renal tubular injury will probably influence the diagnostic modalities and therapeutic approaches to acute drug induced renal failure.

Angiotensinase A (aminopeptidase A): properties of chromatographically purified isoforms from human kidney

Angiotensin-II-cleaving angiotensinase A (aminopeptidase A, E.C. 3.4.11.7, ATA) plays an important role in glomerular haemodynamics. the pathophysiology of essential arterial hypertension and the induction of vascular disorders. In order to study biochemical and immunological properties of ATA, two isoforms (I and II) of the glycoprotein were isolated for the first time from human kidney cortex. Kidney cortex homogenate, digested with bromelain, was fractionated by ammonium sulphate precipitation and subsequent hydrophobic interaction chromatography, using a fast protein liquid chromatographic (FPLC) system. By anion-exchange FPLC (Mono Q column), the isoforms of ATA were eluted in two distinct peaks and were further purified by size-exclusion FPLC and preparative polyacrylamide gel electrophoresis. Biochemical, immunological and immunohistological characterization disclosed differences in the intrarenal localization, glycosylation Michaelis constant and apparent molecular mass (native and sodium dodecyl sulphate gel electrophoresis) but similar properties in the double-immunodiffusion technique. Polyclonal rabbit antibodies, raised against ATA isoforms I and II, precipitated an analogous antigen in urine from patients with renal tubular damage.

Biochemical and immunological properties of urinary angiotensinase A and dipeptidylaminopeptidase IV. Their use as markers in patients with renal cell injury

Dipeptidyl peptidase IV (EC 3.4.14.5) and angiotensinase A (EC 4.4.11.7) were purified to homogeneity from pooled urine concentrate of patients with renal damage, using ultrafiltration, ammonium sulphate precipitation, lectin affinity chromatography, FPLC-ion-exchange(Mono-Q-)chromatography, and FPLC-gel filtration (Superdex). Based on the specific enzyme activity of the starting material, dipeptidyl peptidase IV was enriched 1629 fold, angiotensinase A 1183 fold. The relative molecular masses, Michaelis constants and isoelectric points were determined. Negative staining of the purified enzymes revealed globular proteins (5-7 nm). Antisera raised against dipeptidyl peptidase IV and angiotensinase A reacted specifically with tubular and, in the case of anti-angiotensinase A sera, with tubular and glomerular structures. In addition, urinary membrane vesicles of proximal tubule origin were eluted with the void volume (Superdex-gel filtration), indicating heavy epithelial cell disintegration. Both soluble tissue enzymes (dipeptidyl peptidase IV, angiotensinase A) and vacuolar blebs shed from epithelia contribute to proteinuria, as was shown in patients with glomerulonephritis, interstitial nephritis, diabetic nephropathy and, for angiotensinase A, in patients with essential arterial hypertension.

Immunoscintigraphic localization of renal tumours in an extracorporeal perfusion model with a monoclonal antibody against gamma-glutamyltransferase

Monoclonal antibody 138H11 against human gamma-glutamyltransferase has been shown to react immunohistochemically with 98% of all tested clear-cell type and chromophilic renal cell carcinomas, but not with renal chromophobic carcinomas, Duct-Bellini carcinomas or oncocytomas. In normal kidney the target epitopes of mAb 138H11 are located in the luminal brush-border membrane of proximal tubule cells, whereas in renal carcinomas the epitopes are found surrounding the whole tumour cells. These results form the basis of the present immunoscintigraphic study designed to evaluate mAb 138H11 in an extracorporeal perfusion model. Immediately after nephrectomy, human tumour-bearing kidneys were perfused with 99mTc-labelled mAb 138H11 in Euro-Collins solution. High specific uptake in 4/4 renal clear cell carcinomas could be demonstrated by planar immunoscintigraphy and single-photon-emission computed tomography, "regions of interest" investigation and immunohistochemistry. In contrast, a perfused oncocytoma showed up as an unlabelled lesion. The results indicate a possible use for mAb 138H11 in immunoscintigraphy or even therapy, provided high tumour uptake can be confirmed in patients.

[Renal involvement in rheumatic (systemic) diseases: new diagnostic possibilities]

Patients (pts) with rheumatoid arthritis (RA) may develop structural damage and functional deterioration of the kidney, where interstitial fibrosis and mesangioproliferative glomerulitis are seen most frequently. Compared to controls 80 pts with RA under various therapeutical regimes and 23 pts with SLE excreted immunoreactive membrane proteins of the proximal tubule at an increased rate. 30 out of 76 pts, but all with SLE, revealed a pathological pattern of proteinuria in SDS-PAGE.

Differential diagnosis of histogenetically distinct human epithelial renal tumours with a monoclonal antibody against gamma-glutamyltransferase

The localization of membrane-bound gamma-glutamyltransferase with monoclonal antibody (mAb) 138H11 proved to be of value for differential diagnosis of renal cancer, since it correlated with the histogenetic profile of human epithelial renal tumors. Immunoreactive gamma-glutamyltransferase was located in the proximal tubule in all normal human kidneys (15/15) examined thus far by both ultrastructural and immunohistochemical techniques. From 68 epithelial renal cancers tested 31/31 clear-cell carcinomas and 15/16 chromophilic carcinomas expressed the target epitope of mAb 138H11. In contrast, 0/11 oncytomas, 0/9 chromophobic carcinomas, and 0/1 Duct-Bellini carcinoma were immunoreactive. These results support a model of histogenesis and classification of epithelial renal tumours, according to which clear-cell and chromophilic renal carcinomas originate from transformed proximal tubule cells, whereas oncocytomas, chromophilic and Duct-Bellini carcinomas originate from cells of the collecting duct.

Glomerular angiotensinase A in the rat: increase of enzyme activity following renal ablation

Angiotensinase A (aminopeptidase A; ATA) is an angiotensin II splitting exopeptidase, which is localized in endothelial and epithelial cells of the glomerular tuft. In order to investigate the influence of a reduction in renal mass on enzyme activity, ATA activity was measured in isolated rat glomeruli five and 14 weeks after 1-1/3 nephrectomy. Glomerular ATA activity in remnant kidneys increased significantly after five weeks following ablation compared with glomeruli of two kidney control rats (5.34 +/- 4.02 vs. 1.71 +/- 1.96 mU/mg protein, P less than 0.05). After 14 weeks, however, this difference was no longer present. Treatment of rats with enalapril or saralasin inhibited the increase of ATA seen five weeks after renal ablation, whereas indomethacin had no effect on enzyme activity. Furthermore, normal two kidney rats, treated with furosemide, revealed a higher glomerular ATA than two kidney controls (5.5 +/- 2.64 vs. 2.1 +/- 1.7 mU/mg protein, P less than 0.05). In vitro superfusion of isolated glomeruli with enalaprilate or furosemide from rats after renal ablation did not influence enzyme activity, however, superfusion with 0.05 mM angiotensin II or 0.05 mM saralasin significantly reduced ATA. Our results suggest that glomerular ATA might be involved in the early regulation of the intrarenal renin-angiotensin system and could modify glomerular adaptation to reduce renal mass by affecting angiotensin II degradation.

Urinary excretion of dipeptidyl aminopeptidase i.v. in patients with renal diseases

Enzymuria is a frequent finding in patients suffering from various kidney diseases. The present study was undertaken to evaluate the clinical value of the determination of tubule-brush-border-associated dipeptidyl aminopeptidase IV (DAP IV) in the urine of patients with acute and chronic tubulointerstitial nephritis (n = 12), chronic glomerulonephritis (n = 15), essential arterial hypertension (n = 30), after kidney transplantation (n = 20), and of healthy control persons (n = 68). DAP IV was measured in spontaneously voided mid-stream morning urine ("second morning urine"), and was expressed as enzyme activity in units/liter. In order to account for variations due to urine concentration without collecting 24-hour specimens, a urinary DAP IV/creatinine ratio (DCR) was calculated. Furthermore, patterns of proteinuria were assayed by SDS-polyacrylamide gel electrophoresis. Urinary DAP IV activity of healthy controls was 4.94 +/- 0.12 U/l (DCR: 0.46 +/- 0.30 U/mmol creatinine) with only small day to day variations. Urinary DAP IV activity in patients with tubulointerstitial nephritis was significantly higher (15.5 +/- 15.6 U/l, p less than 0.05 vs controls; DCR: 1.67 +/- 0.97 U/mmol creatinine, p less than 0.001 vs controls). In patients with chronic glomerulonephritis urinary DAP IV activity was 9.6 +/- 5.6 U/l, p less than 0.05 (DCR: 1.22 +/- 0.75 U/mmol creatinine, p less than 0.05 vs controls). Increased urinary DAP IV activity in patients with chronic glomerulonephritis was associated with a mixed glomerulo-tubular pattern of proteinuria (as determined by SDS-PAGE).(ABSTRACT TRUNCATED AT 250 WORDS)

Urinary proteins of tubular origin: basic immunochemical and clinical aspects

A variety of tubular marker proteins, as compared to healthy controls, are excreted at an increased rate in the urine of patients with renal damage. Beside cytoplasmic glutathione-S-transferase and lysosomal beta-N-acetyl-glucosaminidase (beta-NAG) the majority of kidney-related urine proteins derives from membrane surface components of the most vulnerable proximal tubule epithelia, among them ala-(leu-gly)-aminopeptidase, gamma-glutamyl transpeptidase (GGT), the tubular portion of angiotensinase A, the major brush border glycoprotein 'SGP-240' and adenosine-deaminase-binding protein. Urinary tissue proteins, e.g. brush border (BB) microvilli, are immunologically identical with those antigens prepared from cell membranes of the human kidney itself. BB antigens are shed into the urine of patients with glomerulonephritis, interstitial nephritis, systemic diseases, e.g. systemic lupus erythematosus (SLE), diabetes mellitus and multiple myeloma, arterial hypertension, infectious diseases (malaria, AIDS) and after operations, renal grafting and administration of X-ray contrast media, aminoglycosides or certain cytostatics (cis-platinum). Tissue proteinuria of tubular proteins is determined by enzyme-kinetic or quantitative immunological assays applying either poly- or monoclonal antikidney antibodies. Clinical, ultrastructural and histochemical studies support the idea that both 'soluble' and high-molecular-weight membrane particles (vacuolar blebs, greater than 10(6) dalton) as well as microfilamental components of the epithelial cytoskeleton contribute to tubular 'histuria' which appears as a sensitive parameter in monitoring tubular damage under clinical conditions at a very early phase.

Tubule-derived membrane glycoproteins in the urine of patients (including those with AIDS) as analysed by radioimmunoblotting

As a contribution to the noninvasive diagnosis of kidney damage, polyclonal antisera specifically directed against brush border surface glycoproteins of the proximal tubule of the human kidney were used in radioimmunoblotting studies for the assessment of kidney-tissue proteinuria. Urine specimens from healthy controls, from patients (n = 41) with various forms of renal involvement and from those suffering from symptomatic HIV-infection (AIDS) but having normal kidney function, were investigated for the excretion of kidney-derived membrane proteins. After SDS-polyacrylamide gel electrophoresis of urine samples and electroblotting of protein bands on nitrocellulose sheets, followed by incubation with the antibody and subsequently with 125I-labelled protein A, 3 major tubular glycoproteins (Mr 240 000, 160 000, 120 000) were revealed by autoradiography. The results indicate and increased shedding of epithelial membrane glycoproteins in the urine of patients with kidney lesions, and they also demonstrate the suitability of radioimmunoblotting for the determination of such tissue-antigens ("brush border-histuria").

Immunological and ultrastructural analysis of loss of tubular membrane-bound enzymes in patients with renal damage

The pathophysiological background of shedding of membrane-bound enzymes from the proximal tubule was assessed in urine specimens of patients with renal damage applying immunospecific affinity-chromatography, immunotitration, ultracentrifugation, electroimmunodiffusion, immunohistology, as well as negative staining technique. Compared to healthy controls, patients with kidney injury, e.g. after administration of potentially nephrotoxic drugs (cytostatics, contrast media) revealed an increased excretion rate of vacuolar membrane fragments (50-500 nm) into urine. The brush border (BB) of the proximal tubule was identified as a main source of urinary blebs as concluded from immunoelectrophoretic and immunohistochemical analysis. In addition, the marker enzyme profile of urinary vacuolar blebs was similar to that of the BB membrane from human kidney. The results further evidenced that, during the initial phase of tubular injury, 5-10 nm surface glycoproteins of the BB, among them Ala-Leu-aminopeptidase and portions of gamma-glu-transpeptidase, are released into urine; this might be followed by increased blebbing of macromolecular BB fragments, indicating more severe membrane disruption.

Glomerular and tubular membrane antigens reflecting cellular adaptation in human renal failure

The excretion profiles of the following marker proteins of glomerular and tubular origin were studied in patients suffering from chronic renal disease (GN, N = 36, GFR: 8 to 120 ml/min/1.73 m2): angiotensinase A (ATA), a glomerular endothelial glycoprotein, tubular ala(-leu-gly)-amino-peptidase-M (APM), gamma-glutamyl transpeptidase (GGT), and the major brush border surface glycoprotein (SGP-antigen) of 240 kD. In addition, urinary excretion of proteins from kidney tissue and serum from 30 patients undergoing chronic hemodialysis (RCDT) were analyzed. Compared to the controls, ATA, APM and GGT activities were significantly higher in urine specimens of patients with GFR greater than 25 ml/min, whereas the urinary APM, GGT and SGP concentrations were decreased, and correlated with the GFR. Urinary GGT activity was negatively correlated with ATA activity but positively correlated with the decrease in GFR. Urine ATA activity of RCDT patients was higher compared to normal controls (2P = 0.001). Urinary excretion of serum proteins of RCDT patients, as assessed by SDS-polyacrylamide gel electrophoresis, disclosed heavy tubular proteinuria, indicating predominant tubular rather than glomerular alterations in handling of proteins. Histochemical evaluation of kidney sections from RCDT patients revealed clusters of hypertrophic nephrons with increased glomerular and tubular concentration of immunoreactive membrane proteins. However, there was a general decrease in renal cell-marker concentrations as observed by quantitative image analyses. These results indicate that renal injury is associated with a modulation in the synthesis of tubular and glomerular cell markers.

[Effect of renovascular roentgen contrast media on the function of the healthy kidney--an individual comparison]

In 50 patients with healthy kidneys the excretion of tubular enzymes was determined quantitatively before and after administration of an ionic and a non-ionic contrast medium and compared intra-individually. Both preparations produced a highly significant increase in enzyme levels to about twice the initial value, the increase being significantly lower with the non-ionic contrast medium. This effect was fully reversible within 24 hours. No noticeable change was seen within the examination period of 48 hours in respect of creatinine and creatinine clearance levels.

[Monoclonal antibodies against the kidney and kidney neoplasms: potential diagnostic probes and therapy]

Monoclonal antibodies (MAb) raised against plasma membranes isolated from human kidney and renal cancer (CA) were capable of reacting with epitopes of either proximal or distal tubular antigens, also found to be excreted in urine of patients under pathological conditions. CA disclosed a microheterogenous distribution of antigens carrying proximal and distal tubule epitopes respectively. Some hybridoma produced MAb which were able to recognize epitopes strongly associated with CA.

Isolation and characterization of dipeptidyl aminopeptidase IV from human kidney cortex

Intact dipeptidyl aminopeptidase IV (DAP IV) was solubilized by bromelain treatment from human kidney brush border plasma-membranes. Purification of DAP IV was performed by a 3-step method, applying lectin-affinity chromatography on WGA-Sepharose, gel filtration and anion-exchange chromatography. DAP IV from human kidney cortex showed a pH optimum of 8.7 and was totally inhibited by 1 mmol/l Zn2+. Isolated DAP IV revealed a relative molecular mass of 250 kDa as determined by the native-PAGE method and of 220 kDa by the gel filtration method. Analytical isoelectric focussing of DAP IV revealed an isoelectric point of pH 5.3. Ultrastructural analysis of isolated DAP IV fractions, using the negative staining technique, disclosed the presence of numerous globular particles with an average diameter of 5 nm which correspond to the structural substrate of the purified protein.

Routine diagnosis with PhastSystem compared to conventional electrophoresis: automated sodium dodecyl sulfate-polyacrylamide gel electrophoresis, silver staining and western blotting of urinary proteins

The recent introduction of the PhastSystem, an automatic electrophoresis and staining system with precast gradient-gels, allows rapid and reproducible analysis of proteinuria in patients suffering from renal injury. A routine method for sodium dodecyl sulfate-polyacrylamide gradient gel electrophoresis (SDS-PAGE) and silver staining of unconcentrated urine specimens in the PhastSystem is described and compared to our conventional "macro"-method with self-cast SDS-polyacrylamide gradient gels. The method described for the PhastSystem using 0.3 microL sample volumes and an 8-25% polyacrylamide gradient gel leads to highly reproducible results within 1.5 h. Before electrophoresis urine specimens were neither concentrated nor dialyzed. Samples with a protein concentration exceeding 5 mg/mL had to be diluted 1:5 (v/v). Analysis and documentation of PhastGels appeared as easy as with our conventional SDS-PAGE. Protein bands could reliably be identified by Western blotting. Urine and serum proteins, separated in PhastGels, were electrophoretically transferred to nitrocellulose and detected with specific antibodies against human albumin, transferrin, alpha-1-antitrypsin and IgG. Comparison of several standard kits for molecular weight determination revealed considerable differences concerning the quality of protein separation patterns. Availability of precast gels and automatization of SDS-PAGE and staining allows easy standardization of urine SDS-PAGE among clinical routine laboratories.

[Characterization of membrane antigens from human kidney and renal adenocarcinoma]

The brush border of the proximal tubule of human kidney consists of peripheral, integral as well as of transmembranous antigens. Peripheral (surface) antigens are associated with the presence of 5-7 nm globular particles sensitive to limited proteolysis; particles were found to contain a multienzyme complex and exhibited strong affinity towards ConA and WGA. PM-antigens can be solubilized from different portions of PM by differential treatment with proteases and detergents. Labelled antisera against isolated surface glycoproteins reveal a specific reaction with luminal PM of the proximal tubule only, supporting their value for quantitative image analysis (histometry) of kidney tissue sections and for screening of tissue-proteinuria. PM were capable of binding cationic serumproteins (esp. immunoglobulin) and certain O/K-antigens from E.coli, where adhesion was observed on peripheral and intrinsic PM-antigens as well. Major markers of the distal tubule are Tamm-Horsfall protein (cytoplasmic compartment) and a PNA-binding glycoprotein originating from the luminal PM. PM from renal adenocarcinoma exhibit not the globular surface structure found in renal PM, show low immunogenicity, a modulation in the glycosylation pattern of the marker gamma-Glu-transpeptidase and are characterized by a marked depletion of normally differentiated renal antigens. Due to solubilization experiments the presence of cryptic antigens are likely. In addition common determinants between cancer antigens and distinct proteins of the distal tubule and placental trophoblast became apparent.

[Immunodiagnosis of kidney tubular cell injuries using specific anti-membrane antibodies]

In contrast to healthy persons, microvillous antigens of the proximal tubule were excreted at an increased rate in patients with kidney diseases as could be shown using specific antisera against brush border (BB) fragments (tissue-proteinuria, histuria). These urinary membrane components were immunologically completely identical with those antigens prepared from isolated kidney cell membranes. A glycoprotein of 240 000 dalton, containing mannose and N-acetylglucosamine was identified as a major immunoreactive constituent of the brush border surface and found to be part of a multienzyme complex. BB-antigens were excreted in urine of patients with glomerulonephritis, hypertension, pyelonephritis, multiple myeloma, after operations, after kidney transplantation, under cytostatic treatment, and after administration of radiopaque agents. Histuria of BB-antigens was significantly higher in patients with multiple myeloma and Bence-Jones-proteinuria compared to those patients where no Bence-Jones L-chains in urine became apparent. Selective kidney angiography and intravenous urography caused a significantly higher output of BB-antigens as compared to the control period (2 p less than 0,005). In a volunteer model, on the basis of BB-histuria, a different nephrotoxic potency of cephalosporins and aminoglycosides arose. In addition, beside soluble BB-antigens, also high molecular weight membrane vesicles were discovered in urine of patients after cytostatic treatment (cis-platinum), after x-ray contrast media, and after kidney transplantation. Both, soluble as well as supramolecular membrane vesicles were isolated from urine applying immunospecific affinity chromatography (anti-BS-agarose beads). Labeled antisera directed against the vesicle material of urine revealed a specific immunofluorescence of cortical tubule only.(ABSTRACT TRUNCATED AT 250 WORDS)