Role of CD59 in experimental glomerulonephritis in rats

In Vivo Assessment of Laboratory-Grown Kidney Tissue Grafts

Directed differentiation of stem cells is an attractive approach to generate kidney tissue for regenerative therapies. Currently, the most informative platform to test the regenerative potential of this tissue is engraftment into kidneys of immunocompromised rodents. Stem cell-derived kidney tissue is vascularized following engraftment, but the connection between epithelial tubules that is critical for urine to pass from the graft to the host collecting system has not yet been demonstrated. We show that one significant obstacle to tubule fusion is the accumulation of fibrillar collagens at the interface between the graft and the host. As a screening strategy to identify factors that can prevent this collagen accumulation, we propose encapsulating laboratory-grown kidney tissue in fibrin hydrogels supplemented with candidate compounds such as recombinant proteins, small molecules, feeder cells, and gene therapy vectors to condition the local graft environment. We demonstrate that the AAV-DJ serotype is an efficient gene therapy vector for the subcapsular region and that it is specific for interstitial cells in this compartment. In addition to the histological evaluation of epithelial tubule fusion, we demonstrate the specificity of two urine biomarker assays that can be used to detect human-specific markers of the proximal nephron (CD59) and the distal nephron (uromodulin), and we demonstrate the deposition of human graft-derived urine into the mouse collecting system. Using the testing platform described in this report, it will be possible to systematically screen factors for their potential to promote epithelial fusion of graft and host tissue with a functional intravital read-out.

The role of the immune system in idiopathic nephrotic syndrome: a review of clinical and experimental studies

Idiopathic nephrotic syndrome (INS) is a multifactorial disease, characterized by proteinuria, hypoalbuminemia, edema and hyperlipidemia. Studies in humans and animal models have associated INS with changes in the immune response. The purpose of this article is to review clinical and experimental findings showing the involvement of the immune response in the pathogenesis of INS. The role of the immune system in INS has been shown by clinical and experimental studies. However, the pattern of immune response in patients with INS is still not clearly defined. Many studies show changes in the dynamics of T lymphocytes, especially the regulatory T cells. Alternatively, there are other reports regarding the involvement of the complement system and B lymphocytes in the pathophysiology of INS. Indeed, none of the immunological biomarkers evaluated were undeniably linked to changes in glomerular permeability and proteinuria. On the other hand, some studies suggest a link between urinary chemokines, such as IL-8/CXCL8 and MCP-1/CCL2, and changes in glomerular permeability and/or the deterioration of glomerulopathies. To understand the pathophysiology of INS, longitudinal studies are clearly needed. The characterization of the profile of the immune response might help the development of specific and individualized therapies, leading to clinical improvement and better prognosis.

The presence of CD55- and/or CD59-deficient erythrocytic populations in patients with rheumatic diseases reflects an immune-mediated bone-marrow derived phenomenon

Background

Complement has the potential to provoke severe impairment to host tissues, as shown in autoimmune diseases where complement activation has been associated with diminished CD55 and/or CD59 expression on peripheral blood cell membranes. The aim of this study was to evaluate the presence of CD55- and/or CD59-deficient erythrocytic populations in patients with different rheumatic diseases and to investigate possible correlations with clinical or laboratory parameters.

Material/Methods

CD55 and CD59 expression was evaluated in erythrocytes of 113 patients with rheumatic diseases, 121 normal individuals, and 10 patients with paroxysmal nocturnal hemoglobinuria (PNH) using the Sephacryl gel microtyping system. Ham and sucrose tests were also performed.

Results

Interestingly, the majority of patients (104/113, 92%) demonstrated CD55- and/or CD59-deficient erythrocytes: 47 (41.6%) with concomitant deficiency of CD55 and CD59, 50 (44.2%) with isolated deficiency of CD55, and 6 (6.2%) with isolated deficiency of CD59. In normal individuals, only 2 (1%) had concomitant CD55/CD59 negativity and 3 (2%) had isolated CD55 or CD59 deficiency. All PNH patients exhibited simultaneous CD55/CD59 deficiency. Positive Ham and sucrose tests were found only in PNH patients. There was no association between the CD55- and/or CD59-deficient erythrocytes and hemocytopenias or undergoing treatment. However, CD55 expression significantly influenced hemoglobin values (F=6.092, p=0.015).

Conclusions

This study provides evidence supporting the presence of erythrocytes with CD55 and/or CD59 deficiency in patients with rheumatic diseases. Moreover, CD55 deficiency on red cells influences hemoglobin concentration. Further studies using molecular techniques will clarify the exact pathophysiological mechanisms of this deficiency.

Shiga toxin 2 reduces complement inhibitor CD59 expression on human renal tubular epithelial and glomerular endothelial cells

Infections with enterohemorrhagic Escherichia coli (EHEC) are a primary cause of hemolytic-uremic syndrome (HUS). Recently, Shiga toxin 2 (Stx2), the major virulence factor of EHEC, was reported to interact with complement, implying that the latter is involved in the pathogenesis of EHEC-induced HUS. The aim of the present study was to investigate the effect of Stx2 on the expression of membrane-bound complement regulators CD46, CD55, and CD59 on proximal tubular epithelial (HK-2) and glomerular endothelial (GEnC) cells derived from human kidney cells that are involved in HUS. Incubation with Stx2 did not influence the amount of CD46 or CD55 on the surface of HK-2 and GEnC cells, as determined by fluorescence-activated cell sorter analysis. In contrast, CD59 was significantly reduced by half on GEnC cells, but the reduction on HK-2 cells was less pronounced. With increasing amounts of Stx2, reduction of CD59 also reached significance in HK-2 cells. Enzyme-linked immunosorbent assay analyses showed that CD59 was not present in the supernatant of Stx2-treated cells, implying that CD59 reduction was not caused by cleavage from the cell surface. In fact, reverse transcription-quantitative PCR analyses showed downregulation of CD59 mRNA as the likely reason for CD59 cell surface reduction. In addition, a significant increase in terminal complement complex deposition on HK-2 cells was observed after treatment with Stx2, as a possible consequence of CD59 downregulation. In summary, Stx2 downregulates CD59 mRNA and protein levels on tubular epithelial and glomerular endothelial cells, and this downregulation likely contributes to complement activation and kidney destruction in EHEC-associated HUS.

Membrane-bound complement regulatory proteins as biomarkers and potential therapeutic targets for SLE

For the last two decades, there had been remarkable advancement in understanding the role of complement regulatory proteins in autoimmune disorders and importance of complement inhibitors as therapeutics. Systemic lupus erythematosus is a prototype of systemic autoimmune disorders. The disease, though rare, is potentially fatal and afflicts women at their reproductive age. It is a complex disease with multiorgan involvement, and each patient presents with a different set of symptoms. The diagnosis is often difficult and is based on the diagnostic criteria set by the American Rheumatology Association. Presence of antinuclear antibodies and more specifically antidouble-stranded DNA indicates SLE. Since the disease is multifactorial and its phenotypes are highly heterogeneous, there is a need to identify multiple noninvasive biomarkers for SLE. Lack of validated biomarkers for SLE disease activity or response to treatment is a barrier to the efficient management of the disease, drug discovery, as well as development of new therapeutics. Recent studies with gene knockout mice have suggested that membrane-bound complement regulatory proteins (CRPs) may critically determine the sensitivity of host tissues to complement injury in autoimmune and inflammatory disorders. Case-controlled and followup studies carried out in our laboratory suggest an intimate relation between the level of DAF, MCP, CR1, and CD59 transcripts and the disease activity in SLE. Based on comparative evaluation of our data on these four membrane-bound complement regulatory proteins, we envisaged CR1 and MCP transcripts as putative noninvasive disease activity markers and the respective proteins as therapeutic targets for SLE. Following is a brief appraisal on membrane-bound complement regulatory proteins DAF, MCP, CR1, and CD59 as biomarkers and therapeutic targets for SLE.

The alternative and terminal pathways of complement mediate post-traumatic spinal cord inflammation and injury

Complement is implicated in the inflammatory response and the secondary neuronal damage that occurs after traumatic spinal cord injury (SCI). Complement can be activated by the classical, lectin, or alternative pathways, all of which share a common terminal pathway that culminates in formation of the cytolytic membrane attack complex (MAC). Here, we investigated the role of the alternative and terminal complement pathways in SCI. Mice deficient in the alternative pathway protein factor B (fB) were protected from traumatic SCI in terms of reduced tissue damage and demyelination, reduced inflammatory cell infiltrate, and improved functional recovery. In a clinically relevant paradigm, treatment of mice with an anti-fB mAb resulted in similarly improved outcomes. These improvements were associated with decreased C3 and fB deposition. On the other hand, deficiency of CD59, an inhibitor of the membrane attack complex, resulted in significantly increased injury and impaired functional recovery compared to wild-type mice. Increased injury in CD59-deficient mice was associated with increased MAC deposition, while levels of C3 and fB were unaffected. These data indicate key roles for the alternative and terminal complement pathways in the pathophysiology of SCI. Considering a previous study demonstrating an important role for the classical pathway in promoting SCI, it is likely that the alternative pathway plays a critical role in amplifying classical pathway initiated complement activation.

A protein toxin from the sea anemone Phyllodiscus semoni targets the kidney and causes a severe renal injury with predominant glomerular endothelial damage

Envenomation by the sea anemone Phyllodiscus semoni causes fulminant dermatitis and, rarely, acute renal failure in humans. Here, we investigated whether the venom extracted from the nematocysts (PsTX-T) was nephrotoxic when administered intravenously in rats and whether PsTX-T induced activation of the complement system. Although small dose of PsTX-T induced acute tubular necrosis in rats resembling pathology seen in patients, kidneys displayed glomerular injury with glomerular endothelial damage, thrombus formation, mesangiolysis, and partial rupture of glomerular basement membrane, accompanied by severe tubular necrosis at 24 hours after administration of 0.03 mg of PsTX-T per animal, similar to the glomerular findings typical of severe hemolytic uremic syndrome. The early stage injury was accompanied by specific PsTX-T binding, massive complement C3b, and membrane attack complex deposition in glomeruli in the regions of injury and decreased glomerular expression of complement regulators. A pathogenic role for complement was confirmed by demonstrating that systemic complement inhibition reduced renal injury. The isolated nephrotoxic component, a 115-kd protein toxin (PsTX-115), was shown to cause identical renal pathology. The demonstration that PsTX-T and PsTX-115 were highly nephrotoxic acting via induction of complement activation suggests that inhibition of complement might be used to prevent acute renal damage following envenomation by P. semoni.

Decay-accelerating factor but not CD59 limits experimental immune-complex glomerulonephritis

The complex balance between the pro-activating and regulatory influences of the complement system can affect the pathogenesis of immune complex-mediated glomerulonephritis (ICGN). Key complement regulatory proteins include decay accelerating factor (DAF) and CD59, which inhibit C3 activation and C5b-9 generation, respectively. Both are glycosylphosphatidylinositol-linked cell membrane proteins, which are widely distributed in humans and mice. Chronic serum sickness induced by daily immunization with horse spleen apoferritin over 6 weeks was used to induce ICGN in DAF-, CD59- and DAF/CD59-deficient mice, with wild-type littermate mice serving as controls. Both DAF and DAF/CD59-deficient mice had an increased incidence of GN relative to wild-type controls associated with significantly increased glomerular C3 deposition. Disease expression in CD59-deficient mice was no different than wild-type controls. DAF- and DAF/CD59-deficient mice also had increased monocyte chemoattractant protein-1 mRNA expression and glomerular infiltration with CD45(+) leukocytes. Our findings suggest that activation of C3 is strongly associated with experimental ICGN while downstream formation of C5b-9 is of lesser pathogenic importance in this model.

Inhibition of Complement Component C3 Reduces Vein Graft Atherosclerosis in Apolipoprotein E3–Leiden Transgenic Mice

BACKGROUND

Venous bypass grafts may fail because of development of intimal hyperplasia and accelerated atherosclerosis. Inflammation plays a major role in these processes. Complement is an important part of the immune system and participates in the regulation of inflammation. The exact role of complement in the process of accelerated atherosclerosis of vein grafts has not yet been explored, however.

METHODS AND RESULTS

To assess the role of complement in the development of vein graft atherosclerosis, a mouse model, in which a venous interposition was placed in the common carotid artery, was used. In this model, vein graft thickening appeared within 4 weeks. The expression of complement components was studied with the use of immunohistochemistry on sections of the thickened vein graft. C1q, C3, C9, and the regulatory proteins CD59 and complement receptor-related gene y could be detected in the lesions 4 weeks after surgery. Quantitative mRNA analysis for C1q, C3, CD59, and complement receptor-related gene y revealed expression of these molecules in the thickened vein graft, whereas C9 did not show local mRNA expression. Furthermore, interference with C3 activation with complement receptor-related gene y-Ig was associated with reduced vein graft thickening, reduced C3 and C9 deposition, and reduced inflammation as assessed by analysis of influx of inflammatory cells, such as leukocytes, T cells, and monocytes. In addition, changes in apoptosis and proliferation were observed. When C3 was inhibited by cobra venom factor, a similar reduction in vein graft thickening was observed.

CONCLUSIONS

The complement cascade is involved in vein graft thickening and may be a target for therapy in vein graft failure disease.

Complement activation contributes to both glomerular and tubulointerstitial damage in adriamycin nephropathy in mice

Adriamycin nephropathy is a model of focal segmental glomerulosclerosis, characterized by proteinuria and progressive glomerulosclerosis and tubulointerstitial damage. In this study, we examined the role of complement in the etiology of adriamycin nephropathy in mice. We used mice deficient in C1q, factor D, C3, and CD59, and compared them with strain-matched controls. C3 deposition occurred in the glomeruli of wild-type mice as early as 48 h following a single i.v. injection of adriamycin. C3-deficient mice developed significantly less proteinuria and less podocyte injury at day 3 postadriamycin than controls, suggesting that complement is important in mediating the early podocyte injury. At later time points, C3-deficient mice were protected from glomerulosclerosis, tubulointerstitial injury, and renal dysfunction. Factor D-deficient mice were also protected from renal disease, confirming the importance of alternative pathway activation in this model. In contrast, C1q-deficient mice developed similar disease to controls, indicating that the complement cascade was not activated via the classical pathway. CD59-deficient mice, which lack adequate control of C5b-9 formation, developed significantly worse histological and functional markers of renal disease than controls. Interestingly, although more C9 deposited in glomeruli of CD59-deficient mice than controls, in neither group was tubulointerstitial C9 staining apparent. We have demonstrated for the first time that alternative pathway activation of complement plays an important role in mediating the initial glomerular damage in this in vivo model of focal segmental glomerulosclerosis. Lack of CD59, which regulates the membrane attack complex, led to greater glomerular and tubulointerstitial injury.

Suppression of complement regulatory proteins (CRPs) exacerbates experimental autoimmune anterior uveitis (EAAU)

This study was undertaken to explore the role of complement regulatory proteins (CRPs) in experimental autoimmune anterior uveitis (EAAU). We observed that the levels of CRPs, Crry and CD59, in the eyes of Lewis rats increased during EAAU and remained elevated when the disease resolved. The in vivo role of these CRPs in EAAU was explored using neutralizing mAbs, antisense oligodeoxynucleotides (AS-ODNs), and small interfering RNAs against rat Crry and CD59. Suppression of Crry in vivo at days 9, 14, or 19 by neutralizing mAb or AS-ODNs resulted in the early onset of disease, the exacerbation of intraocular inflammation, and delayed resolution. Suppression of CD59 was only effective when the Abs and ODNs were given before the onset of disease. The most profound effect on the disease was observed when a mixture of Crry and CD59 mAbs or AS-ODNs was administered. A similar effect was observed with a combination of Crry and CD59 small interfering RNA. There was no permanent histologic damage to ocular tissue after the inflammation cleared in these animals. Increased complement activation as determined by increased deposition of C3, C3 activation fragments, and membrane attack complex was observed in the eyes of Lewis rats when the function and/or expression of Crry and CD59 was suppressed. Thus, our results suggest that various ocular tissues up-regulate the expression of Crry and CD59 to avoid self-injury during autoimmune uveitis and that these CRPs play an active role in the resolution of EAAU by down-regulating complement activation in vivo.

Mechanisms of immune-deposit formation and the mediation of immune renal injury

The passive trapping of preformed immune complexes is responsible for some forms of glomerulonephritis that are associated with mesangial or subendothelial deposits. The biochemical characteristics of circulating antigens play important roles in determining the biologic activity of immune complexes in these cases. Examples of circulating immune complex diseases include the classic acute and chronic serum sickness models in rabbits, and human lupus nephritis. Immune deposits also form "in situ". In situ immune deposit formation may occur at subepithelial, subendothelial, and mesangial sites. In situ immune-complex formation has been most frequently studied in the Heymann nephritis models of membranous nephropathy with subepithelial immune deposits. While the autoantigenic target in Heymann nephritis has been identified as megalin, the pathogenic antigenic target in human membranous nephropathy had been unknown until the recent identification of neutral endopeptidase as one target. It is likely that there is no universal antigen in human membranous nephropathy. Immune complexes can damage glomerular structures by attracting circulating inflammatory cells or activating resident glomerular cells to release vasoactive substances, cytokines, and activators of coagulation. However, the principal mediator of immune complex-mediated glomerular injury is the complement system, especially C5b-9 membrane attack complex formation. C5b-9 inserts in sublytic quantities into the membranes of glomerular cells, where it produces cell activation, converting normal cells into resident inflammatory effector cells that cause injury. Excessive activation of the complement system is normally prevented by a series of circulating and cell-bound complement regulatory proteins. Genetic deficiencies or mutations of these proteins can lead to the spontaneous development of glomerular disease. The identification of specific antigens in human disease may lead to the development of fundamental therapies. Particularly promising future therapeutic approaches include selective immunosuppression and interference in complement activation and C5b-9-mediated cell injury.

CD59a deficiency exacerbates ischemia-reperfusion injury in mice

The terminal complement components C5a and the membrane attack complex are involved in the pathogenesis of ischemia-reperfusion injury in many organs. CD59 is the major regulator of membrane attack complex formation. Mice deficient in the Cd59a gene (mCd59a-/-) were used to investigate the role of CD59 in renal ischemia-reperfusion injury. Unilateral ischemia-reperfusion injury was induced by clamping the left renal pedicle for 30 minutes under general anesthetic. Mice were studied at 72 hours and 2 weeks after ischemia-reperfusion injury. mCd59a-/- mice developed significantly greater tubular injury (P = 0.01), tubulointerstitial apoptosis (P = 0.02), and neutrophil influx (P = 0.04) than controls at 72 hours after ischemia-reperfusion. Two weeks after ischemia-reperfusion, mCd59a-/- mice exhibited more severe tubular damage predominantly in a corticomedullary distribution than controls (P = 0.02). Quantification of interstitial leukocytes revealed significantly greater numbers of infiltrating lymphocytes (but not macrophages) in mCd59a-/- mice than controls (P = 0.04) at 2 weeks. At both time points, significantly more C9 (as a marker of membrane attack complex) deposition occurred in a peritubular distribution in mCd59a-/- mice than controls. In conclusion, these results demonstrate that the lack of CD59a, by allowing unregulated membrane attack complex deposition, exacerbates both the tubular injury and the interstitial leukocyte infiltrate after ischemia-reperfusion injury in mice.

Pathological study on the relationship between C4d, CD59 and C5b-9 in acute renal allograft rejection

In order to evaluate the activation or inhibition of the later phases of classical complement cascade in renal allograft presenting with acute rejection, particularly with C4d deposition on the peritubular capillary (PTC), we observed the expression of CD59 and C5b-9 on the PTC. Subjective cases were divided into two groups, an acute rejection group, of 4 males and 6 females, and a normal donor group, of 5 males and 5 females. Renal biopsies were performed at the onset of acute rejection and at the transplant operation, before reperfusion. C4d deposition on PTC was found in three of 10 cases (30%) with biopsy proven acute rejection, whereas CD59 on PTC was positively expressed in all of the rejection cases. Although C5b-9 was not observed on PTC in the acute rejection group, it was intensively deposited on the tubular basement membrane (TBM) in five cases, including the three with positive C4d on PTC. In the normal donor group, CD59 on PTC was intensively observed, whereas C5b-9 was weakly expressed on TBM. CD59, a complement regulatory factor, works as an inhibitory factor against the formation of C5b-9, a membrane attack complex. From our data, we noted the dissociation between the depositions of C4d and C5b-9 on PTC. The substantially expressed CD59 on PTC may affect this dissociation between C4d and C5b-9 on PTC. The intensive deposition of C5b-9 on TBM in acute rejection cases may suggest an independent immunological injury attacking tubular cells.

Overexpression of complement inhibitor Crry does not prevent cryoglobulin-associated membranoproliferative glomerulonephritis

BACKGROUND

Mice overexpressing thymic stromal lymphopoietin (TSLP) develop mixed cryoglobulinemia with renal disease closely resembling human cryoglobulin-associated membranoproliferative glomerulonephritis (MPGN), including glomerular deposits of immunoglobulins and complement. We assessed the effect of complement inhibition through overexpression of Crry (complement receptor-1 related gene/protein Y), which blocks the classic and alternative pathway of complement activation through inhibition of the C3 convertase, in cryoglobulinemia-associated immune complex glomerulonephritis.

METHODS

TSLP transgenic mice were crossbred with animals overexpressing Crry. Mice were sacrificed after 50 days (females) or 120 days (males), and kidneys, blood, and urine were collected from seven mice of each experimental group (wild type, Crry transgenic, TSLP transgenic, and Crry/TSLP doubly transgenic).

RESULTS

TSLP/Crry doubly transgenic animals demonstrated expected serum levels of Crry. Renal involvement, both in TSLP transgenic and TSLP/Crry doubly transgenic animals, was characterized by glomerular matrix expansion, macrophage influx, activation of mesangial cells, and deposition of immunoglobulins and complement. Overexpression of Crry did not result in significant improvement of renal pathology or laboratory findings. Expression of recombinant soluble Crry was confirmed by enzyme-linked immunosorbent assay (ELISA) in Crry transgenic animals. However, formation of the membrane attack complex C5b-9 as a marker of terminal active complement components and represented by glomerular C9 staining could not be inhibited in Crry transgenic TSLP mice.

CONCLUSION

These results indicate that overexpression of Crry was not sufficient to prevent renal injury in TSLP transgenic mice. We suggest that the inhibitory capacity of Crry may be overwhelmed by chronic complement activation. Further studies need to address the role of complement in cryoglobulinemic glomerulonephritis before therapeutic complement inhibition can be attempted.

CD59a deficiency exacerbates accelerated nephrotoxic nephritis in mice

CD59 is a complement regulatory protein that inhibits the terminal part of the complement system, the membrane attack complex (MAC), a mediator of renal injury. Mice deficient in the Cd59a gene (mCd59a-/-) were used to investigate the role of CD59 in experimentally induced accelerated nephrotoxic nephritis, a model of immune complex-mediated glomerulonephritis. After accelerated nephrotoxic nephritis was induced by administration of sheep nephrotoxic globulin, mCd59a-/- mice and strain-matched controls on two genetic backgrounds, 129/Sv x C57BL/6 and 129/Sv, were examined. For both, mCd59a-/- mice developed significantly greater glomerular cellularity than wild-type (WT) mice at day 5 after administration. At day 10 post-administration, mCd59a-/- mice exhibited more glomerular thrombosis than WT mice (thrombosis score, 1.8 [range, 1.4 to 4.0] versus 0.8 [range, 0.2 to 1.5] quadrants thrombosed per glomerulus, respectively; P = 0.0006). In the majority of experiments, mCd59a-/- mice also had significantly more proteinuria than controls; however, there was no difference in serum creatinine or albumin. Quantitative immunofluorescence of kidney sections revealed significantly more C9 (as a marker of MAC) deposition within glomeruli of mCd59a-/- mice than WT controls (P < 0.001). There was no difference in deposition of C3 and sheep IgG between the two experimental groups. The lack of CD59a, by allowing unregulated MAC deposition, exacerbates the renal injury in this model of immune complex-mediated glomerulonephritis.

Deficiency of the mouse complement regulatory protein mCd59b results in spontaneous hemolytic anemia with platelet activation and progressive male infertility

Basal complement activity presents a potential danger for "self" cells that are tightly protected by complement regulators including CD59. Mice express two Cd59 genes (mCd59a and mCd59b); mCd59b has approximately a 6-fold higher specific activity than mCd59a. Consistently, mCd59b knockout mice present a strong phenotype characterized by hemolytic anemia with increased reticulocytes, anisopoikilocytosis, echinocytosis, schistocytosis, free hemoglobin in plasma, hemoglobinuria with hemosiderinuria, and platelet activation. Remarkably, mCd59b(-/-) males express a progressive loss of fertility associated with immobile dysmorphic and fewer sperm cells after 5 months of age. This work indicates that mCd59b is a key complement regulator in mice and that CD59 is critical in protecting self cells; it also provides a novel model to study complement regulation in human diseases.

FK506 ameliorates proteinuria and glomerular lesions induced by anti-Thy 1.1 monoclonal antibody 1-22-3

BACKGROUND

We have previously reported that CD4 T lymphocytes and their cytokines contribute to development of Thy 1.1 glomerulonephritis (GN). FK506 is reported to suppress the production of Th1 cytokines. The aims of this study were to elucidate the role of Th1 cytokines on mesangial alteration and to examine whether FK506 is available for therapy of mesangial proliferative GN.

METHODS

The effects of daily treatments of FK506 from day -5 and from day +1 of Thy 1.1 GN induction on glomerular alterations were analyzed.

RESULTS

FK506 treatment with 1.0 and 0.3 mg/kg body weight (BW) daily from day 1 to day 4 significantly reduced the glomerular expression of mRNA for interferon-gamma (IFN-gamma; 1.0 mg/kg BW FK506, 32.4% to the placebo group, P < 0.01) and IL-2 (55.6%, P < 0.01) on day 5. FK506 treatment from day -5 of GN induction reduced proteinuria and glomerular alteration in a dose-dependent manner. Although no side effects were detected in rats with 0.3 mg/kg BW of FK506 treatment from day +1, the treatment also ameliorated proteinuria (day 14, 3.7 +/- 0.89 vs. 19.8 +/- 12.3 mg/100 g BW/day P < 0.05) and glomerular alterations [total cell number, 63.1 +/- 3.1 vs. 80.2 +/- 7.4, P < 0.01; matrix expansion, 0.90 +/- 0.30 vs. 1.34 +/- 0.27, P < 0.05; alpha-smooth muscle actin (alphaSMA) expression; 1.20 +/- 0.12 vs. 1.96 +/- 0.29, P < 0.01] on day 14.

CONCLUSION

Th1 cytokines may play an important role in the development of mesangial proliferative glomerulonephritis, and could be targets for therapy. FK506 might be available for clinical use.

Increased susceptibility of decay-accelerating factor deficient mice to anti-glomerular basement membrane glomerulonephritis

To prevent complement-mediated autologous tissue damage, host cells express a number of membrane-bound complement inhibitors. Decay-accelerating factor (DAF, CD55) is a GPI-linked membrane complement regulator that is widely expressed in mammalian tissues including the kidney. DAF inhibits the C3 convertase of both the classical and alternative pathways. Although DAF deficiency contributes to the human hematological syndrome paroxysmal nocturnal hemoglobinuria, the relevance of DAF in autoimmune tissue damage such as immune glomerulonephritis remains to be determined. In this study, we have investigated the susceptibility of knockout mice that are deficient in GPI-anchored DAF to nephrotoxic serum nephritis. Injection of a subnephritogenic dose of rabbit anti-mouse glomerular basement membrane serum induced glomerular disease in DAF knockout mice but not in wild-type controls. When examined at 8 days after anti-glomerular basement membrane treatment, DAF knockout mice had a much higher percentage of diseased glomeruli than wild-type mice (68.8 +/- 25.0 vs 10.0 +/- 3.5%; p < 0.01). Morphologically, DAF knockout mice displayed increased glomerular volume (516 +/- 68 vs 325 +/- 18 x 10(3) microm(3) per glomerulus; p < 0.0001) and cellularity (47.1 +/- 8.9 vs 32.0 +/- 3.1 cells per glomerulus; p < 0.01). Although the blood urea nitrogen level showed no difference between the two groups, proteinuria was observed in the knockout mice but not in the wild-type mice (1.4 +/- 0.7 vs 0.02 +/- 0.01 mg/24 h albumin excretion). The morphological and functional abnormalities in the knockout mouse kidney were associated with evidence of increased complement activation in the glomeruli. These results support the conclusion that membrane C3 convertase inhibitors like DAF play a protective role in complement-mediated immune glomerular damage in vivo.

Accelerated nephrotoxic nephritis is exacerbated in C1q-deficient mice

C1q deficiency strongly predisposes to the development of systemic lupus erythematosus in humans and mice. We used the model of accelerated nephrotoxic nephritis in C1q-deficient mice to explore the mechanisms behind these associations. C1q-deficient mice developed severe glomerular thrombosis within 4 days of induction of disease, whereas wild-type mice developed mild injury. These findings suggest that C1q protects from immune-mediated glomerular injury. This exacerbated thrombosis was also seen in mice triply deficient in C1q, factor B, and C2, excluding a major pathogenic role for the alternative pathway of complement in this phenomenon. However, these mice did not develop elevated creatinine levels. No exacerbation of accelerated nephrotoxic nephritis was observed in mice doubly deficient in factor B and C2, suggesting a protective role for C1q against renal inflammation that is proximal to C2 activation. There were increased murine IgG deposits, neutrophil numbers, and apoptotic cells in the glomeruli of C1q-deficient mice compared with wild-type mice. Renal expression of genes encoding procoagulant proteins was also enhanced in C1q-deficient mice. The increased IgG deposits and apoptotic cells in the glomeruli of C1q-deficient mice suggest that the exacerbation of disease may be due to a defect in the clearance of immune complexes and/or apoptotic cells from their kidneys.

Targeted deletion of the CD59 gene causes spontaneous intravascular hemolysis and hemoglobinuria

The glycolipid-anchored glycoprotein CD59 inhibits assembly of the lytic membrane attack complex of complement by incorporation into the forming complex. Absence of CD59 and other glycolipid-anchored molecules on circulating cells in the human hemolytic disorder paroxysmal nocturnal hemoglobinuria is associated with intravascular hemolysis and thrombosis. To examine the role of CD59 in protecting host tissues in health and disease, CD59-deficient (CD59(-/-)) mice were produced by gene targeting in embryonic stem cells. Absence of CD59 was confirmed by staining cells and tissues with specific antibody. Despite the complete absence of CD59, mice were healthy and fertile. Erythrocytes in vitro displayed increased susceptibility to complement and were positive in an acidified serum lysis test. Despite this, CD59(-/-) mice were not anemic but had elevated reticulocyte counts, indicating accelerated erythrocyte turnover. Fresh plasma and urine from CD59(-/-) mice contained increased amounts of hemoglobin when compared with littermate controls, providing further evidence for spontaneous intravascular hemolysis. Intravascular hemolysis was increased following administration of cobra venom factor to trigger complement activation. CD59(-/-) mice will provide a tool for characterizing the importance of CD59 in protection of self tissues from membrane attack complex damage in health and during diseases in which complement is activated.

Membrane complement regulatory proteins: insight from animal studies and relevance to human diseases

The complement system plays an important role in host defense. However, if not properly regulated, activated complement can also cause significant damage to host tissues. To prevent complement-mediated autologous tissue damage, host cells express a number of membrane-bound complement regulatory proteins. These include decay-accelerating factor (DAF, CD55), membrane cofactor protein (MCP, CD46) and CD59. Recent studies of membrane complement regulatory proteins from various animal species have revealed similarities as well as significant differences from the corresponding human proteins. In this review, we summarize recent advances in this area and contrast the structure, function and tissue distribution of membrane complement regulatory proteins in human and nonprimate mammalian species. We also discuss how the characterization of the animal proteins has provided important clues and might continue to show relevance to the pathogenesis and therapeutics of a number of human diseases.

CD59 protects rat kidney from complement mediated injury in collaboration with crry

BACKGROUND

As previously reported, the membrane-bound complement regulator at the C3 level (Crry/p65) is important in maintaining normal integrity of the kidney in rats. However, the role of a complement regulator at the C8/9 level (CD59) is not clear, especially when activation of complement occurs at the C3 level. The aim of this work was to elucidate the in vivo role of CD59 under C3 activating conditions.

METHODS

Two monoclonal antibodies, 5I2 and 6D1, were used to suppress the function of Crry and CD59, respectively. In order to activate alternative the pathway of complement, the left kidney was perfused with 5I2 and/or 6D1 and was recirculated.

RESULTS

In the kidneys perfused with 5I2 alone, deposition of C3 and membrane attack complex (MAC) was observed in the peritubular capillaries, vasa recta, and tubular basement membranes. Cast formation, tubular dilation and degeneration, and cellular infiltration were observed at days 1 and 4, and they recovered by day 7. Further suppression of CD59 by 6D1 significantly enhanced the deposition of MAC and worsened the already exacerbated tubulointerstitial injury. These effects of 6D1 were dose dependent. Perfusion with 6D1 alone did not induce histologic damage or MAC deposition in the tubulointerstitium.

CONCLUSIONS

In rats, CD59 maintains normal integrity of the kidney in collaboration with Crry in rats against complement-mediated damage in vivo.

Crry, a complement regulatory protein, modulates renal interstitial disease induced by proteinuria

Crry, a complement regulatory protein, modulates renal interstitial disease induced by proteinuria.

BACKGROUND

Recent studies have suggested a role for urinary complement components in mediating tubulointerstitial damage, which is known to have a good correlation with progression of chronic renal diseases. Although accumulating evidence suggests that complement regulatory proteins play an important protective role in glomeruli, their role in renal tubules remains unclear. In order to establish the role of a complement regulatory protein, Crry, in renal tubular injury, we employed a molecular biological approach to block the expression of Crry in tubules of animals with proteinuria induced with puromycin aminonucleoside nephritis (PAN). Methods and Results. Two different antisense oligodeoxynucleotides (ODNs) against Crry were designed and applied to cultured rat mesangial cells in vitro in order to establish their efficacy. Antisense ODN treatment resulted in decreased expression of Crry protein associated with increased sensitivity to complement attack in cell lysis assays compared with control ODN treatment or no treatment (44.7, 1.50, and 1.34%, respectively). Antisense ODNs did not affect the expression of Thy1 as a control, confirming the specificity of our ODNs. In vivo, we performed selective right renal artery perfusion to administer antisense ODNs to the kidney and showed prominent uptake of ODNs by proximal tubular cells. Reduced expression of Crry protein was demonstrated in proximal tubular cells in antisense ODNs-treated kidneys. Normal rats treated with the antisense ODNs did not show any pathological changes. However, in PAN, rats with massive proteinuria showed increased deposition of C3 and C5b-9 in tubules in antisense-treated kidneys, and histological assessment revealed more severe tubulointerstitial injury in antisense-treated animals compared with controls.

CONCLUSION

These results establish a pathogenic role for complement in leading to tubulointerstitial injury during proteinuria and, to our knowledge for the first time, show a protective role of a complement regulatory protein, Crry, in renal interstitial disease.

The concept of glomerular self-defense

The balance between local offense factors and defense machinery determines the fate of tissue injury: progression or resolution. In glomerular research, the most interest has been on the offensive side, for example, the roles of leukocytes, platelets, complement, cytokines, eicosanoids, and oxygen radical intermediates. There has been little focus on the defensive side, which is responsible for the attenuation and resolution of disease. The aim of this review is to address possible mechanisms of local defense that may be exerted during glomerular injury. Cytokine inhibitors, proteinase inhibitors, complement regulatory proteins, anti-inflammatory cytokines, anti-inflammatory eicosanoids, antithrombotic molecules, and extracellular matrix proteins can participate in the extracellular and/or cell surface defense. Heat shock proteins, antioxidants, protein phosphatases, and cyclin kinase inhibitors may contribute to the intracellular defense. This article outlines how the glomerulus, when faced with injurious cells or exposed to pathogenic mediators, defends itself via the intrinsic machinery that is brought into play in resident glomerular cells.

Complement regulatory proteins in glomerular diseases

Complement activation plays a critical role in the pathogenesis of many forms of glomerulonephritis. Complement activation leads to tissue injury through various mechanisms including the generation of chemotactic factors and activation of the resident glomerular cells following C5b-9 insertion. Recent advances have disclosed the mechanisms of regulation of complement activation by discovery of a number of complement regulatory proteins. Decay accelerating factor (DAF), membrane cofactor protein (MCP), and complement receptor type 1 (CR1) act by inactivating C3/C5 convertase. They belong to the gene superfamily known as the regulators of complement activation (RCA), and share a common structural motif called a short consensus repeat (SCR). In contrast, CD59 works by inhibiting formation of C5b-9. The glomerulus is particularly well endowed with these membrane-bound complement regulatory proteins. DAF, MCP, and CD59 are ubiquitously expressed by all three resident glomerular cells, while CR1 is localized exclusively in podocytes. Expression of complement regulatory proteins can be changed by many factors including complement attack itself, and their expression levels are affected in various glomerular disorders. Studies utilizing cultured glomerular cells and animal models of glomerular diseases suggest important protective roles of complement regulatory proteins against immune-mediated renal injury. Recent progress in molecular biological techniques has made new therapeutic strategy feasible. Systemic administration of soluble recombinant complement regulatory proteins and local overexpression of complement regulatory proteins are promising therapeutic approaches.

Effect of the sugar chain of soluble recombinant CD59 on complement inhibitory activity

A soluble recombinant CD59#77 (rCD59#77), consisting of 77 amino acids starting from the N terminus of membrane-bound CD59, was prepared using a gene expression system in CHO cells. The rCD59#77 preparation was composed of glycosylated and non-glycosylated forms (G and NG forms). Unexpectedly, NG form was 7 times more potent than G form in complement inhibitory activity. Postulating that sialic acids on G-form molecules make it difficult for rCD59#77 to access nascent membrane attack complexes on the cell surface, the sialic acids were removed by neuraminidase treatment. However, the inhibitory activity was not changed. Next, one of two putative N-glycosylation sites was mutated by substituting Gln18 for Asn18. The mutant, designated rCD59#77(N/Q), had no sugar moiety and was as active as the NG form of rCD59#77. These results suggest that the bulky sugar moiety at Asn18 is not necessary for the complement-inhibitory activity of rCD59 and actually hampers that function.

Transfected CD59 protects mesangial cells from injury induced by antibody and complement

CD59 is a complement regulatory protein on the glomerular cells that inhibits C5b-9 assembly and insertion. We employed an overexpression strategy to determine the functional significance of CD59 in mesangial cells. We made a CD59 expression vector tagged with FLAG utilizing site-directed mutagenesis and PCR, which allows transfected CD59 to be distinguished from the constitutively expressed protein. In stable clones, overexpressed CD59 was clearly detected immunocytochemically both by anti-FLAG and anti-CD59 antibody in a granular pattern. The overexpression of CD59 was also confirmed by Western blotting. To determine if overexpression of CD59 by mesangial cells protected these cells from C5b-9 attack, we performed complement-mediated cell lysis assays. CD59-transfected mesangial cells demonstrated marked resistance to complement-mediated cell lysis which was reversed in the presence of antibody to CD59. We also investigated the role of CD59 in protecting cells from the effects of membrane insertion of sublytic quantities of C5b-9. Overexpressed CD59 suppressed production of superoxide, one of the inflammatory mediators induced by sublytic C5b-9 attack. These results demonstrate directly that transfected CD59 functions as a potent protector of mesangial cells against both lytic and sublytic attack by C5b-9. CD59 may be an important regulator of complement-mediated disease in the glomerular mesangium.

Intercellular adhesion molecule-1/leukocyte function associated antigen-1-mediated and complement receptor type 4-mediated infiltration and activation of glomerular immune cells in immunoglobulin A nephropathy

Glomerular expression of intercellular adhesion molecule-1 (ICAM1) (CD54) and membrane cofactor protein (MCP; CD46) and positive infiltrating cells in leukocyte function associated antigen-1 (LFA1)alpha (CD11a) and C3bi receptors (CR3/CD11b, CR4/CD11c) were examined by the indirect immunoperoxidase method on 43 sets of repeated renal biopsy specimens from patients with immunoglobulin A nephropathy. Twenty-four-hour urine protein at the time of renal biopsy was also evaluated. Glomerular infiltration of LFA1alpha+ cells was significantly correlated with glomerular expression of ICAM1 (r = 0.494, P < 0.0001). Glomerular complement receptor type 4 (CR4)+ cells were significantly correlated with glomerular expression of MCP (r = 0.405, P < 0.0001). The glomerular expressions of ICAM1 and MCP were significantly correlated with each other (r = 0.700, P < 0.00001). The glomerular infiltrations of LFA1alpha+ and CR4+ cells were highly correlated with each other (r = 0.884, P < 0.00001), and both cell types were significantly correlated with urine protein (respectively, r = 0.426 and 0.478, P < 0.001 and 0.0001). When the change in these parameters between the time of the initial and follow-up biopsies was evaluated, there was a significant correlation between the change in glomerular expression of ICAM1 (DeltaICAM1) and MCP (DeltaMCP) as well as between the change in glomerular infiltration of LFA1alpha+ cells (DeltaLFA1alpha+) and CR4+ cells (DeltaCR4+). Both DeltaLFA1alpha+ and DeltaCR4+ were significantly correlated with the change in urine protein. These findings suggest that ICAM1/LFA1 interaction and MCP-mediated C3bi/C3biR interaction cooperate and participate in persistent glomerular infiltration of immune cells in immunoglobulin A nephropathy, and that these LFA1alpha+ and C3biR+ cells contribute to the induction of proteinuria.

Differential expression of complement proteins and regulatory decay accelerating factor in relation to differentiation of cultured human colon adenocarcinoma cell lines

Self protection of host cells against inadvertent injury resulting from attack by autologous complement proteins is well reported for vascular epithelium. In intestinal epithelium, the expression of C complement proteins and regulatory proteins remains currently poorly reported. This study looked at the distribution of C complement proteins and regulatory decay accelerating factor (DAF) in four cultured human intestinal cell lines of embryogenic or colon cancer origins. C3 and C4 proteins and DAF were widely present in human colon adenocarcinoma T84, HT-29 glc-/+ cells compared with human embryonic INT407 cells. In contrast, no expression of C5, C5b-9, and CR1 was seen for any of the cell lines. Taking advantage of the Caco-2 cells, which spontaneously differentiate in culture, it was seen that the C3, C4, and DAF were present in undifferentiated cells and that their expression increased as a function of the cell differentiation. These results, taken together with other reports on the presence of C complement proteins and DAF in the intestinal cells infer that the expression of regulatory C complement proteins develops in parallel with the expression of C proteins to protect these cells against the potential injury resulting from the activation of these local C proteins. Moreover, the finding that the pathogenic C1845 Escherichia coli binds to the membrane bound DAF in the cultured human intestinal cells synthetising locally C proteins and regulatory C proteins supports the hypothesis that E coli could promote inflammatory disorders by blocking local regulatory protein function.

Role of a rat membrane inhibitor of complement in anti-basement membrane antibody-induced renal injury

In the kidneys of anti-glomerular basement membrane (anti-GBM) antibody disease, binding of antibodies to tubular basement membrane (TBM) is often observed. The present work was performed to explore the mechanisms of binding of anti-GBM antibodies to TBM in vivo with special reference to 5I2Ag, a rat membrane inhibitor of complement which regulates complement activation at C3 convertase level. To suppress functions of renal 5I2Ag, F(ab')2 fragment of 5I2 (a neutralizing mAb against 5I2Ag) was perfused in the left kidney and then blood circulation was restored. Mild proteinuria ( < 10 mg/16 hr) was observed during first several days. Five days later, there were tubulointerstitial injuries defined by tubular vimentin staining and leukocyte infiltration. Significant deposition of C3 was observed in the capillaries and in TBM. In rats intravenously injected with rabbit anti-rat GBM antibodies five minutes after kidney perfusion with 5I2, strong binding of rabbit IgG to TBM was observed at one and five days after injection. Although these rats showed mild proteinuria comparable to those perfused with 5I2 and those injected with normal rabbit serum, tubulointerstitial injury was significantly enhanced at Day 5. In contrast, rats perfused with irrelevant mAb and injected with anti-GBM antibodies did not show any significant binding of antibodies to TBM nor tubulointerstitial injury. Furthermore, rats which were made proteinuric by puromycin aminonucleoside and injected with anti-GBM antibodies did not show any significant binding of rabbit IgG to TBM. These results indicate that 5I2Ag, a rat membrane inhibitor of complement at the C3 convertase level, regulates vascular permeability in the living kidney, and that dysfunction or decreased expression of this molecule leads to increased accessibility of anti-GBM antibodies to TBM.

CD59: its role in complement regulation and potential for therapeutic use

CD59 regulates complement activation cascade at the final step, inhibiting formation of membrane attack complex (MAC). This protein, being anchored to the cell membrane via glycosyl phosphatidyl inositol (GPI), is expressed ubiquitously on cells which are in contact with body fluids containing components. Recently, MAC formation has been reported to play an important role in pathogenesis of inflammatory diseases such as ischemia or autoimmune diseases. In this review, we describe the structure and biological activities of CD59, the pathogenic role of MAC formation, and discuss application of soluble molecules of CD59 for therapeutic use.

Tubulointerstitial injury induced in rats by a monoclonal antibody that inhibits function of a membrane inhibitor of complement

The kidney widely expresses membrane-associated complement regulatory proteins (membrane inhibitors of complement). The aim of this work was to evaluate the roles of these molecules in rat kidneys in vivo. To suppress functions of rat membrane inhibitors of complement, two mAbs, 512 and 6D1, were used. 5I2 and 6D1 inhibit functions of membrane inhibitors of complement at C3 level (rat Crry/p65) and C8/9 level (rat CD59), respectively. F(ab')2 fragment of 5I2 or 6D1 was perfused in the left kidneys, and perfusate was discarded from the renal vein. After perfusion, the left kidneys were connected to systemic circulation. In rats perfused with 5I2, mouse IgG was found in glomeruli, peritubular capillaries, vascular bundles, and tubules 15 min after recirculation. Binding of C3 and C5b-9 was evident in these areas. 1 d after perfusion with 5I2, cast formation, dilatation of tubular lumen, and tubular cell degeneration were observed. At day 4 through day 7, significant mononuclear cell infiltration and proximal tubule damage were observed. These changes were completely prevented by complement depletion. Rats perfused with 6D1 showed the binding of mouse IgG in the similar areas as 5I2, but C3 or C5b-9 deposition was not observed. Rats perfused with 6D1 or vehicle only did not show any pathology in the left kidneys. These results suggest that rat Crry/p65 plays protective roles against spontaneously occurring indiscriminate attack to tubulointerstitial tissues by autologous complement and that rat Crry/p65 is one of the important factors to maintain normal integrity of the kidney in rats.

Complement regulation in the rat glomerulus: Crry and CD59 regulate complement in glomerular mesangial and endothelial cells

The complement regulators, decay accelerating factor, membrane cofactor protein, and CD59 are present in human glomeruli. Crry is the rodent analogue to the former two proteins. In this study, we examined complement regulation in cultured rat glomerular endothelial cells (GEnC) and mesangial cells (MES). Immunoprecipitation of 125I-labeled membrane proteins and Western blotting studies were performed with anti-Crry and anti-CD59. In both GEnC and MES, Crry was present as 53, 65, and 78 kD proteins. The 20 kD CD59 was apparent in GEnC. CD59 was also present in MES, but in relatively smaller quantities. By Northern analyses, 1.8 kb CD59 mRNA was present in GEnC as well as in RNA from isolated rat glomeruli. mRNA for Crry was present in both GEnC and MES as 2.2 kb species. The functional significance of these proteins was evaluated next. Anti-Thy 1.1 IgG was used to activate the complement classical pathway in MES. To inhibit the function of the complement regulators, anti-CD59 and/or anti-Crry F(ab')2 antibodies were added with anti-Thy 1.1. Inhibition of Crry function led to enhanced cytotoxicity, while there was no effect when CD59 function was inhibited. The complement alternative pathway was studied by adding complement in Mg-EGTA buffer. Inhibition of Crry led to productive alternative pathway activation, which was accentuated by anti-CD59 when Crry was incompletely inhibited. Alternative pathway regulation was also evaluated in GEnC. Inhibition of CD59 function alone had no effect in GEnC, while inhibition of Crry led to significant cytotoxicity from alternative pathway activation. Under conditions in which Crry was inactive, inhibition of CD59 further enhanced cytotoxicity. Therefore, Crry is present in both GEnC and MES and restricts the complement alternative pathway in both cell types. Crry also regulates the classical pathway in MES. CD59 is present and functionally active in GEnC, while it appears to have a minor role in MES.

Pathogenic significance of interleukin-6 in a patient with antiglomerular basement membrane antibody-induced glomerulonephritis with multinucleated giant cells

We report a patient with anti-glomerular basement membrane disease who developed renal failure associated with systemic manifestations, including acute-phase inflammatory reactions and plasmacytosis. Renal tissue obtained by an open surgical biopsy showed circumferential cellular crescents, multinucleated giant cells, and exudation of fibrin in all glomeruli. Immunofluorescence microscopy demonstrated deposition of immunoglobulin G, C3, and membrane attack complex along glomerular capillary walls. Multinucleated giant cells were suggested to be macrophage-monocyte lineage because they were CD68 positive. Bone marrow aspiration showed an increase of plasma cells. Immunostaining showed intensive expression of interleukin-6 (IL-6) in practically every part of the renal sites involving multinucleated cells, crescents, tubules, and infiltrating cells, suggesting that one of the sources of systemically elevated IL-6 was the kidney. Serum IL-6, anti-glomerular basement membrane antibody, and acute-phase proteins were markedly elevated, and returned dramatically to the normal level after corticosteroid therapy and plasmapheresis. We believe that IL-6 played an important role in the development of many symptoms in the present case.

Molecular cloning of the rat analogue of human CD59: structural comparison with human CD59 and identification of a putative active site

We have previously described the purification and partial characterization of the rat analogue of the human complement regulatory molecule CD59 [Hughes, Piddlesden, Williams, Harrison and Morgan (1992) Biochem. J. 284, 169-176]. We present here the molecular cloning and full sequence analysis of this molecule. A PCR-based approach utilizing primers designed from the amino-terminal protein sequence was used to isolate a full-length cDNA clone from a rat kidney cDNA library. This clone encoded a 92 bp 5'-flanking sequence, a 66 bp signal peptide and a 315 bp coding region containing putative glycosylation and GPI-anchor signals. The 3' untranslated flanking region was approximately 1.1 kbp long and included the poly-A tail and a CATA repeating sequence. The coding region was 58% identical with the human cDNA at the nucleotide level and 44% identical at the amino acid level. Despite this relatively low overall sequence conservation, several highly conserved stretches were apparent, particularly in the N-terminal portion of the molecule, in the cysteine-rich region immediately preceding the site of glycolipid attachment and in the C-terminal peptide removed during glycolipid attachment. An N-glycosylation site was identified at Asn-16 and a putative glycosylphosphatidylinositol anchor addition site at Asn-79, indicating that the mature processed protein was two residues longer than human CD59. Comparison of the sequences of rat and human CD59, together with consideration of the published three-dimensional structure of human CD59 and functional data, implicates specific regions of the protein in interactions with C-8 and/or C-9.