Jan R. Brentjens

Studies on the formation of glomerular immune deposits in Brown Norway rats injected with mercuric chloride

Brown Norway rats injected with mercuric chloride (HgCl2) develop autoantibodies which immunolocalize along the glomerular basement membrane at first in a linear pattern and then in a granular pattern. The aim of this study was to characterize the specificity of these antibodies and to investigate the mechanisms responsible for the formation of granular immune deposits in the subepithelial zone of the glomerular basement membrane. The rats were found to develop circulating anti-laminin, anti-type IV collagen, anti-heparan sulfate proteoglycan, and anti-entactin antibodies. Antibodies against laminin and type IV collagen were found in relatively high titers in the sera and were specifically concentrated in the nephritic kidneys. Antibodies eluted from the nephritic kidneys with either linear or granular deposits reacted with basement membrane antigens synthesized and secreted by cultured rat glomerular visceral epithelial cells. Thus, in this model, the interaction of anti-laminin and type IV collagen antibodies with antigens secreted by glomerular visceral epithelial cells might, together with other mechanisms, contribute to the formation of granular immune deposits in the subepithelial part of the glomerular basement membrane.

Gametes contain angiotensin converting enzyme (kininase II)

The localization of angiotensin converting enzyme (ACE) in the gonads of the normal rabbit was studied by immunofluorescence and immunoelectron microscopy. The enzyme is present in the cytoplasm of testicular spermatids and of epididymal and ejaculated spermatozoa, and on the surface of follicular and tubal cocytes. These findings support the hypothesis that ACE has a role in gamete maturation and in fertilization.

Experimental Chronic Serum Sickness in Rats

This article describes a method of immunization that produces chronic serum sickness in rats within a relatively short time. Fisher rats, which were immunized subcutaneously three times with bovine serum albumin (BSA) in adjuvant, responded with high titers of antibodies to BSA. 2 weeks after the third subcutaneous immunization, daily increasing amounts of BSA were injected either intraperitoneally or intravenously. When an intravenous dose of 2mg of BSA was reached, the rats were given daily intravenous injections of BSA for several weeks. This procedure, which avoided death from anaphylaxis, induced severe proliferative glomerulonephritis in all the rats and produced deposition of antigen-antibody complexes in many other organs besides the kidney. This highly reproducible model of experimental chronic serum sickness in inbred animals may have applications for the study of the mechanisms of immune complex disease.

Antibody-mediated injury to proximal tubules in the rat kidney induced by passive transfer of homologous anti-brush border serum

Abstract Study of the natural history of Heymann nephritis in rats has led to the suggestion that antibodies to brush border are responsible for injury to proximal tubules. To obtain direct evidence that antibodies to brush border are cytotoxic to cells of the proximal tubular epithelium, passive transfer experiments were performed. Rats with serum sickness glomerulonephritis were recipients of homologous anti-brush border serum. Forty-eight hours after the first injection of anti-brush border serum, immunoglobulin was bound to the luminal border of proximal tubules. Fixation of immunoglobulin was associated with loss of microvilli and proliferation of cells of the tubular epithelium. The changes in proximal tubules observed in passive transfer experiments were similar to those seen in rats with Heymann nephritis and were not observed in animals which received injections of normal rat serum. It appears that damage of renal tubules may be the consequence of deposition of antibodies along the plasma membrane of tubular cells.

Glomerular macrophage proliferation in experimental immune complex nephritis

In immune complex nephritis, glomerular hypercellularity is known to result from the proliferation of intrinsic cells and from the infiltration of mononuclear cells, primarily macrophages. An immunohistochemical double-labeling procedure was used to determine whether macrophages were among the cells which may undergo mitosis within the glomerular tuft. The monoclonal antibody ED1 served as a macrophage marker; cells in the S-phase of mitosis were recognized by uptake of bromodeoxyuridine. Glomerular proliferation was studied in chronic serum sickness of LEW rats, an animal model of immune complex nephritis for which the relationship between immunopathology and pathophysiology has been well described. In normal glomeruli, resident mesangial macrophages accounted for an unexpectedly large proportion (greater than or equal to one-third) of the total mitotic activity. In immune complex glomerulonephritis, the rate of glomerular macrophage proliferation increased rapidly just at the onset of proteinuria and remained high throughout the remaining course of disease. Glomerular macrophages from rats with proliferative nephritis also divided more vigorously than normal in short term culture in vitro, while persistently expressing abnormal surface marker phenotypes. The proliferation of mesangial macrophages appears to be a prominent feature of the normal process of glomerular cell renewal. In hypercellular glomeruli, vigorous local proliferation could greatly amplify the potential of macrophages to cause damage.

Immunologically mediated lesions of kidney tubules and interstitium in laboratory animals and in man

ConclusionIn recent years, animal models of TI nephritis attributable to humoral immune mechanisms have become firmly established. Results of immunopathology studies indicate that similar mechanisms might be involved in a small fraction of human TI nephritides. In some patients the contribution of humoral immune mechanisms to TI lesions may not have been recognized in tissue specimens obtained at late stages of disease.In laboratory animals as well as in man insufficient information is available to appraise the possible significance of immediate-type hypersensitivity and cell-mediated immune reactions in the induction and perpetuation of TI lesions. More studies on these two immune effector mechanisms are needed to clarify the pathogenesis of TI nephritis that, in the majority of the patients, is still not understood.

The occurrence of IgA-nephropathy in patients with diabetes mellitus may not be coincidental: a report of five cases.

We describe five patients with IgA-nephropathy complicating diabetes mellitus. In four cases, diabetic glomerulosclerosis was present at the same time. One patient suffered from dermatitis herpetiformis. The observation of the present five cases together with the notion of an increased prevalence in diabetes mellitus of celiac disease and dermatitis herpetiformis suggests that the occurrence of IgA-nephropathy in diabetic patients is not mere coincidence.

Factors influencing susceptibility of LEW rats to Heymann nephritis.

Although most LEW rats develop the proteinuria of Heymann nephritis (HN) within 2 months after immunization with Fx1A, protein excretion of some animals remains normal. We have compared nonproteinuric rats with those that developed HN in order to identify factors that influence susceptibility to immunologically medicated kidney disease. In the primary response to Fx1A, immunofluorescence tests showed that antibrush border titers in serum and immunoglobulin deposition in vivo were similar in all rats. However, complement was detected only in rats with proteinuria. Reimmunization with Fx1A at 30 weeks stimulated anamnestic antibody responses in all rats. Following reimmunization, 60% of nonproteinuric rats developed severe HN with an unusually rapid (1 week) onset. Once again, complement was present only in glomeruli of rats with proteinuria. It appears that titers of antibodies to brush border, measured by immunofluorescence tests, are not an index of the pathogenicity of the immune response to Fx1A. Immunological memory, leading to rapid expression of autoimmune disease upon reexposure to antigen, can be established by a primary immunization that does not produce clinical symptoms. Abnormal urine protein composition may provide a clue to subclinical immunopathology of the kidney.

Expression and modulation of surface antigens in cultured rat glomerular visceral epithelial cells.

This study, using immunocytochemical light and electron microscopy techniques, characterizes the distribution of three antibodies bound to the surface of rat glomerular visceral epithelial cells (GEC) in culture, and tests their ability to redistribute corresponding antigens under conditions appropriate for antigenic modulation (antigen disappearance). At 4 degrees C or after fixation, anti-renal tubular brush border vesicle (BBV) IgG bound diffusely to the surface of GEC and to coated pits. Anti-gp330 IgG had a discrete distribution on the surface of GEC and reacted with coated pits. Anti-podocalyxin IgG was bound diffusely to the surface of GEC but not to coated pits. At 37 degrees C, anti-BBV IgG induced marked redistribution of immune complexes with both shedding and internalization. Anti-gp330 IgG induced weaker redistribution, with internalization of immune complexes predominating. Anti-podocalyxin IgG induced rapid redistribution of immune complexes and antigenic modulation but minimal internalization. Experiments of differential redistribution indicated that anti-BBV IgG modulated the expression of both gp330 and podocalyxin; anti-gp330 IgG had a weaker effect on BBV antigens and podocalyxin; and anti-podocalyxin failed to redistribute BBV antigens or gp330. The relevance of these immunocytochemical studies of antibody-cell surface antigen interaction in cultured GEC to understanding the pathogenesis of Heymann glomerulonephritis (HG) is discussed.

Renal Injury and Proteinuria in Female Spontaneously Hypertensive Rats

This investigation describes the evolution of functional and morphological changes in the kidney of female spontaneously hypertensive rats (SHR; 5-90 weeks) and control animals of the same genetic strain, Wistar-Kyoto (WKY). Systolic blood pressure in SHR was 162.0 +/- (SD) 14.1 mm Hg up to 45 weeks, then increased to 189.4 +/- (SD) 16.6 mm Hg (50-90 weeks). Blood pressure in WKY controls remained constant (117.8 +/- 13.6 mm Hg, 5-100 weeks). Protein excretion in the SHR was higher than controls (1.5 +/- 0.5 mg/24 h x 100 g BW, 5-100 weeks) from week 30 on. At 90 weeks, excretion rose to 26.1 +/- 9.8 mg/24 h x 100 g BW and is predominately an albuminuria. After 70 weeks superficial tubular fluid albumin concentration in the SHR is significantly increased (p less than 0.001) over controls. Microscopic changes were evident in glomeruli, tubules, interstitium and arterial vessels at 72-90 weeks and demonstrated an increasing gradient of severity from outer to inner cortex. Glomeruli show sclerosis, fibrinoid necrosis and pericapsular fibrosis. Glomeruli studied with a polyanionic stain revealed a marked decrease in staining affinity of deep, compared to superficial glomeruli. The arterial lesions consisted of thickening of the intima and hyperplasia of the media. WKY kidneys were unremarkable. The selectivity of renal injury and proteinuria in the female SHR is similar to that in the male SHR. However, the evolution of these changes is delayed and may be related to a lower blood pressure until 50 weeks of age.