Recombinant variants of antibody 138H11 against human gamma-glutamyltransferase for targeting renal cell carcinoma

The monoconal antibody 138H11 recognizes human renal gamma-glutamyltransferase (GGT), an antigen shown to allow targeting primary and metastatic renal cell carcinoma (RCC). We determined the primary structure of the antigen binding region of mAb 138H11 and generated several different recombinant antibody variants. First, monomeric single-chain Fv antibody fragments, diabodies and triabodies were obtained by constructing linker variants consisting of 18, 10, 8, 5, 3, 2, 1 and zero amino acid residues, resulting in significant differences in yield and molecular architecture. Second, two variants of disulphide bond-stabilised Fv fragments (dsFvs) were generated using two different pairs of complementary framework amino acid positions of VH and VL for disulphide stabilisation. The binding activities of diabodies to human GGT located on its tissue decreased when using shorter linker lengths. The scFv dimer containing a 3 amino acid residue linker peptide and one of the dsFv variants were not functional. Further, the work paves the way for generating new effector constructs and a systematic optimisation of the pharmacokinetics of this tumor targeting antibody by offering variants with a broad range of valencies and molecular masses.

1-alpha-calcidol modulates major human monocyte antigens and toll-like receptors TLR 2 and TLR4 in vitro

Since vitamin D derivatives are known to interfere with the cellular immune response, we analysed the possible effect of 1-alpha-calcidol (AC) on major monocyte antigens CD14 (an endotoxin receptor), HLA-DR, and toll-like recptors 2 and 4 (TLR2, TLR4). Peripheral blood monocytes were isolated from healthy donors and cultured by standard protocol followed by incubation with various concentrations of AC in unstimulated and LPS-activated cells. After 24, 48 and 72 hours cells were harvested and analysed for the expression of antigens by flowcytometry. Compared to the controls AC increased the expression of CD14 in a dose and time dependent manner (after 72 hours culture time p < 0.01). AC was capable of further stimulating CD14 expression in LPS activated monocytes (p < 0.05). Both LPS and AC downmodulated HLA-DR dramatically after 24 (p < 0.05), 48 (p < 0.01) and 72 hours (p < 0.0001). The expression of TLR2 but not of TLR4 was inhibited by 10-7M AC. The data reveal that AC significantly modulates the expression of CD14, HLA-DR as well as of TLR2, all involved as targets and effector molecules in antigen recognition and processing, relevant to overcome infections and organ lesions.

Proinflammatory blood monocytes: main effector and target cells in systemic and renal disease; background and therapeutic implications

Although peripheral blood monocytes are heterogeneous, they all express the CD14 molecule, a multifunctional receptor, and part of the toll-like membrane receptor complex. In healthy persons, a minor subset (8%) coexpresses CD14 and CD16, a low affinity Fc-gamma type III receptor. This subpopulation shows characteristics of tissue macrophages and expands greatly in acute and chronic infections, systemic inflammatory syndromes, hyperlipidedemia, AIDS and renal failure. CD14+/CD16+ monocytes (Mo) exhibit higher phagocytosis activity than CD14++/CD16-negative monocytes and synthesize high levels of interleukin-1, TNF-alpha and HLA-DR, -DP and -DQ antigens. Glucocorticoids (and interleukin-4), and successful therapy in patients with inflammatory and septic complications lead to a down-regulation in the expression of CD14 and deplete CD14+/CD16+-proinflammatory Mo. Recovery of low monocytic HLA-DR expression parallels clinical improvement. Serial analyses of Mo phenotypes may be useful tools for monitoring patients receiving immunosuppressive and anti-inflammatory therapy respectively.

Haemodialysis monocytopenia: differential sequestration kinetics of CD14+CD16+ and CD14++ blood monocyte subsets

In peripheral blood the majority of circulating monocytes present a CD14highCD16- (CD14++) phenotype, while a subpopulation shows a CD14lowCD16+ (CD14+CD16+) surface expression. During haemodialysis (HD) using cellulosic membranes transient leukopenia occurs. In contrast, synthetic biocompatible membranes do not induce this effect. We compared the sequestration kinetics for the CD14+CD16+ and CD14++ monocyte subsets during haemodialysis using biocompatible dialysers. Significant monocytopenia, as measured by the leucocyte count, occurred only during the first 30 min. However, remarkable differences were observed between the different monocyte subsets. CD14++ monocyte numbers dropped to 77 +/- 13% of the predialysis level after 15 min, increasing to > or = 93% after 60 min. In contrast, the CD14+CD16+ subset decreased to 33 +/- 15% at 30 min and remained suppressed for the course of dialysis (67 +/- 11% at 240 min). Approximately 6 h after the end of HD the CD14+CD16+ cells returned to basal levels. Interestingly, the CD14+CD16+ monocytes did not show rebound monocytosis while a slight monocytosis of CD14++ monocytes was occasionally observed during HD. A decline in CD11c surface density paralleled the sequestration of CD14+CD16+ monocytes. Basal surface densities of important adhesion receptors differed significantly between the CD14+CD16+ and CD14++ subsets. In conclusion, during HD the CD14+CD16+ subset revealed different sequestration kinetics, with a more pronounced and longer disappearance from the blood circulation, compared with CD14++ monocytes. This sequestration kinetics may be due to a distinct surface expression of major adhesion receptors which facilitate leucocyte-leucocyte, as well as leucocyte-endothelial, interactions.

Targeted therapy of experimental renal cell carcinoma with a novel conjugate of monoclonal antibody 138H11 and calicheamicin thetaI1

In search for a new therapeutic approach for metastasized renal cell carcinoma (RCC), we evaluated the cytotoxicity of a novel prodrug chemoimmunoconjugate with monoclonal antibody (mAb) 138H11 and the DNA-cleaving enediyne calicheamicin thetaI1 (Camtheta) in vitro and in vivo. Previously, mAb 138H11, produced against human renal gamma-glutamyltransferase, stained over 99% clear cell and papillary RCC on frozen sections, showing a membranous expression of the target antigen. In contrast, in normal kidneys gammaGT was restricted to the brush-border in the lumen of proximal tubules and not accessible to the circulation. Thus, human tumor-bearing kidneys perfused in an extra-corporeal system with 99mTc-138H11 revealed a high, specific uptake into the tumor. In this study, fluorescence-activated cell sorting analysis showed binding of mAb 138H11 to RCC cell lines, whereas squamous cell carcinoma lines, fibroblasts, and the murine RENCA were negative. XTT cell proliferation assays revealed efficient killing of the Caki-1 cell line by the 138H11-Camtheta conjugate using SPDP (EC50 = 5 x 10(-11) M) as a covalent linker. For in vivo testing, five groups of eight nude mice each were injected with 2.5 x 10(6) Caki-1 cells s.c. and treated with the following: (a) PBS; (b) 138H11; (c) Camtheta; (d) a mixture of 138H11 and Camtheta; and (e) 138H11-Camtheta conjugate. Treatment started on day 1 after tumor induction and was repeated three times. The data show a highly significant inhibition of tumor growth with the 138H11-Camtheta conjugate versus PBS (P = 0.004). Only mice treated with 138H11-Camtheta showed a tumor shrinkage to minimal residues. In a second experiment, lower doses of the 138H11-Camtheta conjugate were compared with an antineuroblastoma mAb (ch14.18), confirming targeted killing of RCC by the 138H11-Camtheta conjugate at tolerable toxicity in vivo. In conclusion, these combined results encourage further studies for targeted therapy of metastatic RCC with mAb 138H11 conjugates.

Induction of RANTES, HLA-DR, and intercellular adhesion molecule-1 on highly purified distal tubular cells from human kidney

BACKGROUND

Expression of proinflammatory molecules by tubular epithelial cells plays an important role in renal allograft rejection and inflammatory kidney diseases. Different studies from patients with acute rejection point to the involvement of distal tubular segments. At present no in vitro system for the human distal tubule is established.

METHODS

Human distal tubular cells were isolated immunomagnetically. Cultured cells were stimulated with cytokines (interferon-gamma, tumor necrosis factor-alpha, interleukin-1beta, or a cytokine mix). Secretion of RANTES (regulated upon activation, normal T-cell expressed and secreted) was evaluated with an enzyme-linked immunoassay. Expression of HLA-DR and intercellular adhesion molecule (ICAM)-1 was assessed by flow cytometric analysis and immunofluorescence studies.

RESULTS

Our data clearly indicate that distal tubular cells express RANTES, HLA-DR, and ICAM-1 in response to a mixture of specific cytokines. Dexamethasone inhibited the induced expression of RANTES and HLA-DR significantly, but not that of ICAM-1.

CONCLUSIONS

We demonstrate an appropriate in vitro system for the human distal tubule. The present study proves the involvement of the distal tubular segment during inflammatory kidney diseases.

Effects of mycophenolic acid on human renal proximal and distal tubular cells in vitro

BACKGROUND

Mycophenolic acid has been shown to be effective for the prevention and treatment of renal allograft rejection. Rejection episodes were found to be associated with an infiltration of lymphocytes and macrophages/monocytes into the diseased kidney. Expression of RANTES, HLA-DR and ICAM-1 may be important for the pathogenesis of this leukocyte infiltration. Therefore the aim of this study was to evaluate the effect of the antiproliferative and immunosuppressive agent mycophenolic acid (MPA) on cell growth and cytokine-induced expression of RANTES, HLA-DR and ICAM-1 of highly purified proximal (PTC) and distal tubular cells (DTC) from human kidney.

METHODS

Human PTC and DTC were cultured in the presence of different concentrations of MPA (0.25-50 microM) or MPA plus guanosine (100 microM). Total cell number (DNA content) was determined after 4 days of cell culture by a non-radioactive fluorescence assay. Cells were stimulated by a combination of cytokines (IL1beta+gammaIFN+TNFalpha=cytomix) or cytomix plus MPA. Secretion of RANTES protein was evaluated with an enzyme-linked-immunosorbent assay. Cell surface expression of HLA-DR and ICAM-1 was assessed by flow cytometric analysis.

RESULTS

MPA inhibited cell growth of PTC and DTC in a dose-dependent manner. This effect was totally abolished by the addition of guanosine. Cytokine-induced RANTES expression was synergistically increased in the presence of MPA, an effect that was partially prevented by the addition of guanosine. Cytokine stimulation resulted in de novo expression of HLA-DR and a marked increase of ICAM-1 expression, which was partially inhibited by dexamethasone. Addition of MPA did not influence this stimulated expression.

CONCLUSIONS

We demonstrate that MPA has an effect on cell growth and chemokine release of tubular epithelial cells, and that these effects are dependent on the inhibition of cellular guanosine production. The clinical consequences of this possible pro-inflammatory effect of MPA on RANTES release may be abolished by a concomitant treatment with steroids.

[When lipids increase in dialysis: the role of heparin! Standard heparin increases, low-molecular-weight heparin lowers triglycerides]

Dyslipoproteinemia in patients on hemodialysis is characterized by a decrease in high density lipoprotein (HDL), cholesterol, hypertriglyceridemia, increased triglyceride-rich lipoproteins, such as very low density lipoprotein (VLDL) and intermediate density lipoprotein (IDL), a higher proportion of the small dense low density lipoprotein (small dense LDL) subfraction, and higher lipoprotein(a) concentration. The reason for the changes in triglyceride metabolism is an increase in the production of apolipoprotein B, and a decrease in the metabolism of VLDL as a consequence of decreased endothelial cell delipidation. The endothelial lipoprotein lipase, which plays a major role in this process, is released by heparin, which is essential for the function of the enzyme. Repeated administration of heparin for anticoagulation during hemodialysis apparently leads to an LPL depletion in the endothelium. This results in further exhaustion of lipolysis. Clinical studies in hemodialysis patients with high triglyceride and cholesterol levels indicate that a change from standard heparin to low-molecular-weight heparin improves the lipid profile by lowering triglycerides and cholesterol.

[Chronic pyelonephritis. Synopsis of laboratory values and ultrasound lead to diagnosis]

Bacteria or their antigens persisting in the kidneys may induce the classical type of chronic pyelonephritis (CP), which progresses slowly, and may finally result in end-stage renal failure requiring dialysis. Pyelonephrogenic strains enter uro-epithelial and renal epithelial cells--where they accumulate--or may invade the renal interstitium. Promoting factors are obstruction, reflux, urolithiasis, nephrolithiasis, pregnancy, diabetes mellitus, humoral and cellular immunodeficiencies, immunosuppression treatment (e.g. following transplants), autoimmune phenomena (antigenic mimicry). Therapy comprises the treatment of underlying disease, antibiotics as indicated by the resistogram, acidification of urine (L-methionine), i.v. immunoglobulins (IgM, IgG) and oral vaccination with lyophilized uropathogens.

Transdifferentiation of distal but not proximal tubular epithelial cells from human kidney in culture

Human renal proximal and distal (thick ascending limb and early distal convoluted tubule) epithelial cells have been isolated according to their specific antigen expression. The cells were well characterized by flow cytometry, enzyme cytochemistry and electron microscopy and cultured for up to 3 months. Cultured tubular cells coexpressed cytokeratin and vimentin as intermediate filament proteins. While primary isolated cells, proximal as well as distal, revealed the phenotypic characteristics of their nephron origin, cultured distal cells showed the tendency to dedifferentiate/transdifferentiate. Distal cells lost their characteristic expression of Tamm-Horsfall glycoprotein and started de novo expression of the proximal marker proteins aminopeptidase M, gamma-glutamyl transferase and dipeptidyl peptidase IV. The expression of these antigens by distal cells could be shown by flow-cytometric analysis and fluorescence microscopy. Enzyme activity assays revealed the activity of aminopeptidase M, gamma-glutamyl transferase and dipeptidyl peptidase IV, but not of the proximal marker enzyme alkaline phosphatase. This antigenic shift could not be prevented in different culture media, and the original phenotype could not be restored. Cultured cells displayed characteristic hormonal stimulation patterns indicative of their proximal and distal origins, as shown by activation of adenylate cyclase by different peptide hormones. These results indicate that distal tubular cells possibly transdifferentiate to a more proximal phenotype in view of loss of the distal marker enzyme Tamm-Horsfall protein and de novo expression of proximal marker enzymes like dipeptidyl peptidase IV and aminopeptidase M.

CD14++ monocytes, CD14+/CD16+ subset and soluble CD14 as biological markers of inflammatory systemic diseases and monitoring immunosuppressive therapy

The majority of peripheral blood monocytes strongly positive for the lipopolysaccharides (LPS)-receptor CD14 are negative for Fcgamma receptor type III (CD16). However, a subset of monocytes coexpressing CD14 and CD16 accounts for about 8% of all monocytes. This population exhibits features of tissue macrophages, and is largely expanded (> 20%) during acute and chronic inflammatory diseases including cases with pararheumatic systemic vasculitis. In addition, compared to normal controls, soluble CD14 (sCD14) is elevated (> 3 microg/ml) in serum specimens of these patients. CD14+/CD16+ monocytes show a higher phagocytosis rate than CD14+/CD16 negative cells, and express higher levels of interleukin-1 and major histocompatibility complex, such as histocompatibility antigens HLA-DR, -DP and -DQ antigens. Glucocorticoids downregulate expression of CD14 and rapidly deplete CD14+/CD16+ monocytes from peripheral blood. Patients under chronic immunosuppressive therapy exhibit low CD14/+/CD16+ rates, which may rise during infectious and non-infectious inflammatory complications, however. Thus, serial analyses for sCD14 and the proinflammatory CD14+/CD16+ subset of monocytes suggest a valuable tool monitoring patients under immunosuppressive and/or antiinflammatory therapy.

Renal failure in giant cell vasculitis

A 59-year-old white woman with temporal arteritis developed progressive renal failure. Renal biopsy results showed focal and segmental necrotizing glomerulonephritis; furthermore, giant cells were present in the destructed vessel walls. Immunosuppressive therapy did not prevent terminal renal failure. This case shows that renal involvement may be a feature of temporal arteritis.

Expanded CD14+ CD16+ monocyte subpopulation in patients with acute and chronic infections undergoing hemodialysis

Infections are frequent complications in end-stage renal failure patients undergoing hemodialysis (HD), and peripheral blood monocytes are important cells in host defense against infections. The majority of circulating monocytes express high levels of lipopolysaccharide receptor antigen CD14 and are negative for the immunoglobulin Fcgamma receptor type III (CD16). We studied the occurrence of a minor subpopulation coexpressing low levels of CD14 together with CD16 in HD patients. In healthy controls CD14+ CD16+ monocytes account for 8% +/- 4% of CD14+ monocytes, with an absolute number of 29 +/- 14 cells/microl. In stable HD patients the CD14+ CD16+ subpopulation was significantly elevated (14% +/- 3%, or 66 +/- 28 cells/microl), while the number of CD14(++) monocytes (monocytes strongly positive for CD14) remained constant. In HD patients suffering from chronic infections a further rise in CD14+ CD16+ monocytes was observed (128 +/- 71 cells/microl; P < 0.01) such that this subpopulation constituted 24% of all blood monocytes. In contrast, numbers of CD14++ cells did not change compared to those for stable HD patients, indicating that the CD14+ CD16+ monocyte subpopulation was selectively expanded. During acute infections the CD14+ CD16+ cell subpopulation always expanded. A whole-blood assay revealed that CD14+ CD16+ monocytes exhibited a higher phagocytosis rate for Escherichia coli bacteria than CD14++ monocytes, underlining their role during host defense. In addition, CD14+ CD16+ monocytes expressed higher levels of major histocompatibility complex (MHC) class II antigens (HLA-DR, -DP, and -DQ) and equal amounts of MHC class I antigens (HLA-ABC). Thus, CD14+ CD16+ cells constitute a potent phagocytosing and antigen-presenting monocyte subpopulation, which is expanded during acute and chronic infections commonly observed in chronic HD patients.

Nephrotoxic potential of antiinfective drugs as assessed by tissue-specific proteinuria of renal antigens

In order to assess the nephrotoxic potential of antibiotics, various aminoglycosides and cephalosporins were tested for their potency to alter the excretion of tubular marker proteins (and brush border antigens) or to change the normal pattern of serumproteinuria as analyzed by SDS polyacrylamidgel gradient electrophoresis. After aminoglycosides, especially after gentamicin injection, a cumulative highly significant increase in the urinary output of marker proteins emerged (healthy volunteer model). In contrast, cephalosporins exhibited practically no nephrotoxic effect on proximal tubule cells. Excretion of tubular marker proteins was enhanced under combined administration of cephalosporins and aminoglycosides mainly due to the aminoglycoside component. There was no nephrotoxic synergy of both drugs. Image analysis of rat kidney sections after injection of aminoglycosides revealed that increased shedding of tubular membrane components under the toxic challenge is followed by rapid inductive repair processes (overshoot protein synthesis) of tubular cells. After a limited acute toxic damage tubular cells may recover within one week.

Isolation of proximal and distal tubule cells from human kidney by immunomagnetic separation. Technical note

After collagenase digestion and Percoll density gradient centrifugation of human renal tissue, tubular epithelial cells of the proximal and the distal segments were isolated with an immunomagnetic method using MACS microbeads. To enrich proximal tubular (PT) cells we used a monoclonal antibody (mAb) against aminopeptidase M (APM, CD 13), specific of the proximal tubule. Distal tubular (DT) cells were isolated through a mAb recognizing Tamm-Horsfall glycoprotein (THG), a specific antigen for the thick ascending limb and the early distal convoluted tubule. Cells of the proximal primary isolate were histochemically strongly positive for aminopeptidase M (98.6%), however, cells of the distal portion were negative (98.7%). Ultrastructural analysis of PTC primary isolates revealed highly preserved brush border microvilli, well-developed endocytosis apparati and numerous mitochondria, whereas DTC primary isolates showed smaller cells with basolateral invaginations and less apical microvilli. Characterization by immunofluorescence indicated the coexpression of cytokeratin and vimentin, whereas staining for desmin, smooth muscle actin, a fibroblast-specific marker and von Willebrand factor was negative. Cultured PT and DT cells displayed different adenylate cyclase responsiveness to hormonal stimulation. PTH (10(-6) M) increased cAMP production in distal cells up to 32.8-fold of the basal level and in proximal only up to 3.5-fold (10(-8) M, DT 14.4x and PT 2.25x). Calcitonin stimulated adenylate cyclase in DT in a dose dependent fashion (10(-6) M, 4.3x; 10(-8) M, 2.25x), whereas only a low calcitonin response was found in PT cells (10(-6) M, 1.6x; 10(-8) M, 1.4x). AVP (10(-6) M) activated the distal cAMP-production only up to 1.9x of the basal level, but the proximal cAMP-production was negligible (only 1.3x the basal level). The data of this study indicate the proximal and distal tubule origin of the cultured cells that were isolated according to their segment-specific antigens.

Immunohistochemical differentiation of metastases of renal carcinomas versus other carcinomas with anti-gamma GT monoclonal antibody 138H11

AIMS

Adenocarcinomas account for about 60% of metastatic cancers of unknown primary (CUP) site. In such a clinical CUP situation, histopathologists are challenged to differentiate renal cell carcinomas (RCC) from other adenocarcinomas with similar immunophenotypes, especially chemotherapeutically treatable mammary and ovarian carcinomas.

METHODS AND RESULTS

Recently, we produced a monoclonal antibody (mAb), designated 138H11, against human gamma-glutamyl-transferase (gamma GT), which stained over 98% primary clear cell and chromophilic RCC on frozen sections. The 138H11 epitope could not be stained using conventional techniques in most paraffin-embedded sections of the same origin, due to destruction by formalin fixation below the detection level. Here, we demonstrate that mAb 138H11 can specifically stain gamma GT in paraffin-embedded primary and metastatic RCC after enhancement with an ultrasensitive immunohistochemical method. We analysed a selected subgroup of adenocarcinomas with immunophenotypes which would not allow a differentiation from RCC in a CUP situation. We found a predominantly membranous expression of the 138H11 target antigen in 26/51 primary RCC and 15/ 34 metastatic RCC. In contrast, all 43/43 primary ovarian and bronchial carcinomas as well as 54/54 metastases of ovarian, mammary, bronchial and gastric carcinomas were negative for mAb 138H11.

CONCLUSIONS

The data suggest that mAb 138H11 is useful for the immunohistochemical differentiation of RCC from other metastatic adenocarcinomas if the primary site of the tumour is not known.

Expression and release of the monocyte lipopolysaccharide receptor antigen CD14 are suppressed by glucocorticoids in vivo and in vitro

The effect of glucocorticoid (GC) treatment on expression and release of the monocyte cell surface LPS receptor Ag CD14 was studied in vivo and in vitro. In patients with acute inflammatory diseases receiving GC pulse therapy serum concentrations of soluble CD14 and CD14 expression by peripheral blood monocytes decreased significantly. The LPS-binding capacity correlated positively with the amount of cell surface CD14 by human blood monocytes. In vitro, a time- and dose-dependent effect of GC preparations on monocyte membrane and soluble CD14 by cultured peripheral blood monocytes was found. Incubation with 2 x 10(-8) M prednisolone down-regulated cell surface CD14 after 72 h, and 2 x 10(-7) M suppressed CD14 expression even after 24 h. Prednisolone also decreased release of the soluble CD14 Ag, where a 10-fold higher GC concentration was required for a significant suppression compared with membrane CD14 during culture. Expression of other monocyte membrane Ags were either unchanged (CD33, CD35), diminished (CD13, CD89), or increased (CD32) by GC, indicating no general down-modulation of cell surface Ag expression. Preincubation with glucocorticoids for 24 h significantly down-regulated CD14 expression during subsequent steroid-free culture for at least 7 days. In cultured monocytes, the LPS-induced increase of membrane and soluble CD14 was markedly but not completely inhibited by prednisolone. Therefore, GC treatment suppresses the up-regulation of the LPS receptor during endotoxin challenge, and likewise, the IL-1 secretion after LPS stimulus was significantly diminished. Taken together, the suppression of the monocytic cell surface and soluble endotoxin receptor CD14 by GC may contribute to the increased risk of infections in patients undergoing steroid therapy.

Expression and release of the monocyte lipopolysaccharide receptor antigen CD14 are suppressed by glucocorticoids in vivo and in vitro

The effect of glucocorticoid (GC) treatment on expression and release of the monocyte cell surface LPS receptor Ag CD14 was studied in vivo and in vitro. In patients with acute inflammatory diseases receiving GC pulse therapy serum concentrations of soluble CD14 and CD14 expression by peripheral blood monocytes decreased significantly. The LPS-binding capacity correlated positively with the amount of cell surface CD14 by human blood monocytes. In vitro, a time- and dose-dependent effect of GC preparations on monocyte membrane and soluble CD14 by cultured peripheral blood monocytes was found. Incubation with 2 x 10(-8) M prednisolone down-regulated cell surface CD14 after 72 h, and 2 x 10(-7) M suppressed CD14 expression even after 24 h. Prednisolone also decreased release of the soluble CD14 Ag, where a 10-fold higher GC concentration was required for a significant suppression compared with membrane CD14 during culture. Expression of other monocyte membrane Ags were either unchanged (CD33, CD35), diminished (CD13, CD89), or increased (CD32) by GC, indicating no general down-modulation of cell surface Ag expression. Preincubation with glucocorticoids for 24 h significantly down-regulated CD14 expression during subsequent steroid-free culture for at least 7 days. In cultured monocytes, the LPS-induced increase of membrane and soluble CD14 was markedly but not completely inhibited by prednisolone. Therefore, GC treatment suppresses the up-regulation of the LPS receptor during endotoxin challenge, and likewise, the IL-1 secretion after LPS stimulus was significantly diminished. Taken together, the suppression of the monocytic cell surface and soluble endotoxin receptor CD14 by GC may contribute to the increased risk of infections in patients undergoing steroid therapy.

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)