Membranous and crescentic glomerulonephritis in a patient with anti-nuclear and anti-neutrophil cytoplasmic antibodies.
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Antibodies, Antineutrophil Cytoplasmic↗
Biomedical subjects
R J Quigg
Publications and source records attributed to R J Quigg.
Altered vitamin D metabolism in type II diabetic mouse glomeruli may provide protection from diabetic nephropathy.
The db/db mouse develops features of type II diabetes mellitus as the result of impaired signaling through its abnormal leptin receptor. In spite of accurate metabolic features of diabetes, renal disease manifestations in these mice are not as severe as in humans suggesting the presence of protective genes. There is a growing body of evidence in humans for the relevance of vitamin D in diabetes. Here we followed a large cohort of db/db mice and their non-diabetic db/+ littermates. Transcriptional profiling revealed significant upregulation of 23 genes involved in Ca2+ homeostasis and vitamin D metabolism in db/db glomeruli relative to db/+ glomeruli. Increased glomerular expression of vitamin D3 1alpha-hydroxylase, vitamin D binding protein, calbindins D9K and D28K, and calcyclin mRNA was confirmed by quantitative reverse transcription-polymerase chain reaction in 20-, 36-, and 52-week-old db/db glomeruli. Although vitamin D3 1alpha-hydroxylase protein was primarily expressed and upregulated in db/db renal tubules, it was also expressed in glomerular podocytes in vivo. Serum 1,25-dihydroxyvitamin D3 and urinary Ca2+ excretion were increased >3-fold in db/db mice compared to db/+ mice. Cultured glomerular podocytes had mRNA for vitamin D3 1alpha-hydroxylase, vitamin D receptor, and calbindin D28K, each of which was increased in high glucose conditions. High glucose also led to enhanced production of fibronectin and collagen IV protein, which was blocked by 1,25-dihydroxyvitamin D3. These results show that vitamin D metabolism is altered in db/db mice leading to metabolic and transcriptional effects. The podocyte is affected by paracrine and potentially autocrine effects of vitamin D, which may explain why db/db mice are resistant to progressive diabetic nephropathy.
25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
Increased serum C3 levels in Crry transgenic mice partially abrogates its complement inhibitory effects.
Complement receptor 1-related gene/protein y (Crry) is a potent murine complement regulator that inhibits C3 convertases. Transgenic mice that overexpress soluble Crry (sCrry), directed systemically by the metallothionein-I promoter, have been used as an animal model for chronic blockade of complement activation. Recently we have found that alternative pathway (AP) activity in Crry transgenic mice was not inhibited as much as expected. To elucidate the mechanism of this effect, we evaluated the AP activities and levels of sCrry and AP complement components in transgenic and non-transgenic mice. In transgenic mice, expression of sCrry was induced by feeding zinc sulphate solution to 70.1 +/- 42.7 micro g/ml mean serum level. Its corresponding level of purified sCrry inhibited 49% of AP activity of normal mice serum; however, the actual AP activities in transgenic mice were not decreased when compared to non-transgenic mice (130.2 +/- 9.0%versus 113.0 +/- 35.4%). Expressed sCrry was functional, as immunoprecipitation and removal of sCrry from transgenic sera with rabbit anti-Crry polyclonal antibody resulted in enhanced AP activity, consistent with initial levels of sCrry. We then compared the changes to C3, factor B, factor H and factor D serum levels in transgenic and non-transgenic mice after induction of sCrry expression. Of these only C3 was increased after zinc feeding in transgenic mice compared to non-transgenic mice (142.8 +/- 14.1%versus 121.4 +/- 15.1%, P = 0.023). These results suggest that the inhibitory effect of chronic exposure to sCrry is compensated by concomitant alteration in C3 levels. This result also suggests the presence of a complement regulatory protein controls the level of serum C3, which has potential importance in the design and interpretation of studies involving chronic use of complement inhibitors.
Animals↗
A protein with characteristics of factor H is present on rodent platelets and functions as the immune adherence receptor.
Complement-coated particles interact with specific immune adherence receptors (IAR). In primates, this function is served by complement receptor 1 (CR1) on erythrocytes. In contrast, rodent platelets bear IAR distinct from CR1, the identity of which was studied here. A 150-kDa C3b-binding protein was isolated from rat platelets, which had immunochemical and biochemical identity to plasma factor H. Immunofluorescence microscopy and flow cytometry demonstrated that factor H was present on the surface of rat and mouse platelets, which could be removed by treatment with neuraminidase. Sheep erythrocytes bearing C3b underwent immune adherence with rat and mouse platelets, which was blocked with anti-factor H F(ab')(2) antibodies, but not with antibodies binding to the complement regulator, Crry, on the platelet surface. By reverse transcription-polymerase chain reaction using rat platelet RNA and primers designed from mouse factor H, a 472-base pair product was generated that was identical in sequence to that produced from rat liver RNA. The translated protein product was 85% similar to mouse liver factor H. The 3'-nucleotide sequence from platelets predicted a soluble factor H protein. By Northern analysis, liver and platelets had identically sized factor H mRNA. Thus, rat and mouse platelets have a membrane protein with characteristics of factor H that is linked via sialic acid residues and functions as the IAR. Whether platelet factor H is acquired by passive adsorption from sera and/or is produced by platelets remains to be determined.
Amino Acid Sequence↗
Glomerular complement regulation is overwhelmed in passive Heymann nephritis.
BACKGROUND: An injection of anti-Fx1A antibodies in rats leads to passive Heymann nephritis (PHN), a model of membranous nephropathy. Fx1A is a crude extract of renal cortex that contains megalin as a principal component. However, when rats are given anti-megalin antibodies, abnormal proteinuria does not occur. Because of the established complement dependence of PHN, we hypothesized that antibodies neutralizing complement regulatory proteins in the rat glomerulus also were required to induce PHN. Two likely targets are Crry and CD59, proteins abundant on the rat podocyte and contained within Fx1A that inhibit the C3 convertase and C5b-9 assembly, respectively. METHODS: Rats were injected with anti-megalin monoclonal antibodies, followed by anti-Crry and/or anti-CD59 F(ab')(2) antibodies five days later. In a second group of experiments, rats were injected with anti-Fx1A or anti-Fx1A immunodepleted of reactivity against Crry and/or CD59. RESULTS: In the setting of podocyte-associated anti-megalin monoclonal antibodies, simultaneous neutralization of Crry and CD59 function led to the development of significant proteinuria (11.0 +/- 2.1 mg/day, P < 0.001 vs. all other groups). In contrast, animals that had neither or only one of these complement regulators inhibited had normal urinary protein excretion (< or =6 mg/day). In animals given anti-Fx1A depleted of anti-Crry and/or anti-CD59, all groups developed typical PHN, characterized by heavy proteinuria and extensive glomerular deposition of C3 and C5b-9. CONCLUSION: Crry and CD59 play an important role in restraining complement-mediated injury following subepithelial immune complex deposition; however, in PHN, their regulatory capacity is overwhelmed.
Animals↗
Value of the Bruce protocol to determine peak exercise oxygen consumption in patients evaluated for cardiac transplantation.
BACKGROUND: Peak exercise oxygen consumption (peak VO2) is an important discriminator of survival in patients with systolic heart failure and is used to select ambulatory patients for transplantation. The major trials assessing the relationship between peak VO2 and survival have used a variety of low-level exercise protocols. It is unknown how peak VO2 measured in this patient population by the more vigorous Bruce treadmill protocol compares with that obtained on less intense protocols. METHODS: We studied 15 patients (50 +/- 12 years old) with severe heart failure (left ventricular ejection fraction 23.5% +/- 8.6%). Patients randomly performed 3 exercise tests with the Bruce treadmill, modified Naughton treadmill, and modified bicycle protocols within 14 days. To determine the ability of this patient population to perform the Bruce protocol, we also retrospectively analyzed the ability of 84 patients to perform this test on their initial evaluations at our center. RESULTS: All patients reached the anaerobic threshold (AT) on all 3 protocols. The Bruce and modified Naughton treadmill protocols resulted in similar peak VO2 percent predicted peak VO2, and VO2 at AT values (17.7 +/- 3.8 mL/kg/min, 57.2% +/- 21.1% and 15.4 +/- 4.1 mL/kg/min vs 18.0 +/- 4.7 mL/kg/min, 58.1% +/- 22.5% and 15.6 +/- 4.4 mL/kg/min, respectively). Peak VO2 and VO2 at AT on both treadmill protocols were higher than those obtained with bicycle testing (15.3 +/- 3.1 and 11.8 +/- 3.0 mL/kg/min, P <.05). Exercise duration was shorter with the Bruce and bicycle protocols (6.2 +/- 2.2 and 6.7 +/- 2.4 minutes, respectively) compared with the modified Naughton protocol (9.7 +/- 4.3 minutes, both P <.005). In addition, 79 of the 84 patients (94%) evaluated were able to complete the Bruce protocol and reach AT. CONCLUSIONS: The Bruce protocol was more time efficient than the modified Naughton protocol and yielded similar peak VO2, percent predicted peak VO2, and VO2 at AT values. Bicycle exercise may underestimate peak VO2 values. The form of exercise should be considered when assessing peak VO2 criteria for transplant listing.
Adult↗
Production and functional analysis of rat CD59 and chimeric CD59-Crry as active soluble proteins in Pichia pastoris.
Crry (CR1-related gene/protein) is a rodent complement regulator that inhibits C3 convertases. CD59 is a conserved protein inhibitor active towards C8 and C9. We have previously produced rat Crry as a recombinant soluble (rs) protein in Pichia pastoris. In this study we produced functionally active rat rsCD59 and a chimeric rsCD59-Crry protein in P. pastoris. The GPI anchor addition site of rat CD59 (Asn-79) was replaced either by a stop codon to produce rsCD59, or with the sequence of the first five short consensus repeats of Crry to produce rsCD59-Crry. Proteins were generated by fermentation and purified by affinity chromatography on an anti-CD59 column. In a standard classical pathway haemolysis assay, all three rs proteins had inhibitory activity, with 50% inhibition at 0.5 microM (rsCrry and rsCD59-Crry) and 4.4 microM (rsCD59). In an assay examining inhibition of C5b-9, in which C5b-7 was first formed, followed by purified C8 and C9, rsCD59 and rsCD59-Crry were active with 50% inhibition at 0.8 microM (rsCD59-Crry) and 1.3 microM (rsCD59). The degree of inhibition was independent of whether the C8 and C9 were of rat or human origin. Therefore, we have produced rsCD59 and rsCD59-Crry in P. pastoris. The rsCD59 retains its inhibitory activity towards C5b-9, while rsCD59-Crry appears to have the combined activities of Crry and CD59. In a haemolytic assay, the inclusion of CD59 to Crry is of no additional benefit to Crry, which may illustrate the overall importance of the C3 convertase step. Yet, inclusion of Crry to CD59 increases the potency of CD59 towards C5b-9.
Animals↗
Complement is activated in kidney by endotoxin but does not cause the ensuing acute renal failure.
BACKGROUND: Acute renal failure (ARF) in sepsis occurs when the release of multiple inflammatory mediators is induced by bacterial endotoxins. C3 mRNA is markedly up-regulated in mouse kidney after exposure to lipopolysaccharide (LPS). We hypothesized that LPS could induce tubular synthesis and secretion of C3, leading to activation of the complement cascade and direct renal tubular injury. METHODS: ARF was induced in mice by intravenous injection of LPS and was confirmed by an acute rise in blood urea nitrogen (BUN) and histologically by acute tubular necrosis. Three separate strategies were used to investigate the role of the complement system in this model of ARF: (1) Crry-Ig, a recombinant protein containing the potent murine complement C3 activation inhibitor Crry was injected at the same time as LPS (N = 8). (2) LPS was injected into transgenic mice overexpressing Crry in glomeruli and tubules (N = 8), and (3) LPS was injected into C3-deficient mice (N = 5). RESULTS: Compared with unmanipulated mice, C3 staining by immunofluorescence (IF) microscopy in mice injected with LPS was greater in renal cortical tubular cells (IF score of 2. 1 +/- 0.1 vs. 1.4 +/- 0.2 in controls, P = 0.013), most prominently at the basolateral surface. LPS injection led to a 16- to 42-fold increase in urinary C3 excretion. Despite reduction or complete elimination of renal C3 with maneuvers suppressing complement activation, BUN values were not statistically different across all groups. In no experiment did BUN values correlate with the extent of C3 staining. CONCLUSION: Although LPS up-regulates renal C3 synthesis, resulting in basolateral tubular C3 deposition, this is not responsible for LPS-induced ARF in mice.
Acute Kidney Injury↗
Echocardiographic Doppler evaluation of left ventricular diastolic filling in older, highly trained male endurance athletes.
Previously published data have suggested that endurance training does not retard the normative aging impairment of early left ventricular diastolic filling (LVDF). Those studies, suggesting no effect of exercise training, have not examined highly trained endurance athletes or their LVDF responses after exercise. We therefore compared LVDF characteristics in a group of older highly trained endurance athletes (n = 12, mean age 69 years, range 65-75) and a group of sedentary control subjects (n = 12, mean age 69 years, range 65-73) with no cardiovascular disease. For all subjects, M-mode and Doppler echocardiographic data were obtained at rest. After baseline studies, subjects underwent graded, maximal cardiopulmonary treadmill exercise testing using a modified Balke protocol. Breath-by-breath respiratory gas analysis and peak exercise oxygen consumption (VO(2)max) measurements were obtained. Immediately after exercise and at 3-6 minutes into recovery, repeat Doppler echocardiographic data were obtained for determination of LVDF parameters. VO(2)max (44 +/-6.3 vs 27+/-4.2 ml/kg/min, P<0.001), oxygen consumption at anaerobic threshold (35+/-5.4 vs 24+/-3.8 ml/kg/min, P<0.001), exercise duration (24+/-3 vs 12+/-6 minutes, P<0.001), and left ventricular mass index (61+/-13 vs 51+/-7.8 kg/m(2), P<0.05) were greater in endurance athletes than in sedentary control subjects, whereas body mass index was lower (22+/-1.7 vs 26+/-3.4 kg/m(2), P<0.001). No differences in any of the LVDF characteristics were observed between the groups with the exception of a trend toward a lower atrial filling fraction at rest in the endurance athlete group versus the control subjects (P = 0.07). High-intensity endurance exercise training promotes exceptional peak exercise oxygen consumption and cardiovascular stamina but does not appear to alter normative aging effects on left ventricular diastolic function.
Aged↗
Renal, central nervous system and pancreatic overexpression of recombinant soluble Crry in transgenic mice. A novel means of protection from complement-mediated injury.
Crry is a potent complement regulator that inhibits classical and alternative pathway C3 convertases in rodents. We have produced transgenic animals expressing Crry as a recombinant soluble protein driven by the broadly active metallothionein-I promoter. These animals have high serum and urinary levels of rsCrry leading to inhibition of complement activity. In nephrotoxic serum nephritis (NSN), injected antibodies bind to glomeruli, leading to complement activation and subsequent glomerular injury and albuminuria. We have shown that rsCrry can block such injury and reduce albuminuria by as much as 75%. Corresponding to the reduction in albuminuria was the complete absence of C3 staining in glomeruli by immunofluorescence microscopy in 17/20 transgene positive animals. Support for a local source of protective rsCrry in this model is provided by the demonstration of Crry transgene mRNA in the glomerulus and a very high fractional excretion of rsCrry in the urine. Therefore, rsCrry expression markedly ameliorates an antibody-induced disease model in vivo. In addition, local synthesis of Crry in other organs that are targets of immune injury has been found. For example, Crry transgene mRNA is present throughout the central nervous system and in pancreatic islets. Thus, continuous complement inhibition at the C3 convertase step appears to be feasible and is effective in complement-mediated injury states. A number of disease models affecting these target organs can be tested using these mice.
Animals↗
We need to inhibit complement in glomerular proteinuria.
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Animals↗
Effects of intravenous milrinone followed by titration of high-dose oral vasodilator therapy on clinical outcome and rehospitalization rates in patients with severe heart failure.
This study evaluated the efficacy of intravenous milrinone in improving hemodynamics and facilitating the titration of high-dose oral vasodilator therapy to improve clinical status. Fourteen patients (mean age 52 +/- 12 years) with severe heart failure and a left ventricular ejection fraction of 18 +/- 6% underwent right-side heart catheterization and an intravenous milrinone infusion followed by titration of oral vasodilator and diuretic therapy. Milrinone significantly (p <0.05) improved right atrial pressure (12 +/- 5 to 8 +/- 5 mm Hg), pulmonary capillary wedge pressure (23 +/- 7 to 15 +/- 7 mm Hg), cardiac index (1.9 +/- 0.4 to 3.4 +/- 0.5 L/min/m2), systemic vascular resistance (1,809 +/- 526 to 891 +/- 144 dynes/s/cm(-5)), and pulmonary vascular resistance (285 +/- 151 to 163 +/- 68 dynes/s/cm(-5)), which was maintained in 10 patients with titration of high-dose oral vasodilator therapy. Oral angiotensin-converting enzyme inhibitor and diuretic doses were increased 318% and 89%, respectively. Four patients also received hydralazine to optimize hemodynamics. New York Heart Association functional class improved from 3.8 +/- 0.4 to 2.6 +/- 0.6 following therapy. Ten patients who responded to therapy had fewer hospitalized days during the subsequent year compared with the year before treatment (4 +/- 17 vs 17 +/- 15), and no patient died. In contrast, the 3 patients who responded poorly to therapy tended to have more hospitalized days at 12 months compared with pretreatment (31 +/- 11 vs 20 +/- 18; NS); 1 patient died. We conclude that intravenous milrinone followed by optimization of oral medical therapy may be used as a therapeutic trial to identify patients in need of cardiac transplantation.
Adult↗
Transgenic mice overexpressing the complement inhibitor crry as a soluble protein are protected from antibody-induced glomerular injury.
Complement receptor 1-related gene/protein y (Crry) is a potent murine membrane complement regulator that inhibits classical and alternative pathway C3 convertases. In nephrotoxic serum (NTS) nephritis, injected antibodies (Abs) bind to glomeruli, leading to complement activation and subsequent glomerular injury and albuminuria. To study the phenotypic effects of continuous complement pathway blockade, transgenic mice were created that express recombinant soluble (rs) Crry directed by the broadly active and heavy metal-inducible metallothionein-I promoter. One transgenic line expressing high levels of rsCrry was propagated. Serum rsCrry levels were 18.7 +/- 2.7 microg/ml (n = 5) at basal level and increased to 118.1 +/- 20.6 microg/ml 4 d after addition of zinc to the drinking water. By reverse transcription polymerase chain reaction (RT-PCR), transgene messenger (m)RNA was present in liver, kidney, brain, lung, and spleen, but not in heart. By in situ RT-PCR analysis of kidneys, transgene mRNA was widely expressed both in renal glomeruli and tubules. Urinary excretion of rsCrry was 113.4 +/- 22.4 microg/ml with a fractional excretion relative to creatinine of 13.2 +/- 2.7%, consistent with local renal production of rsCrry and secretion into urine. The founder and all transgene positive adult animals have remained healthy with no mortality or apparent phenotypic abnormalities, including infection or immune complex disease. To determine whether rsCrry blocked complement-mediated injury, NTS nephritis was induced by injection of NTS immunoglobulin (Ig)G, followed by an 18-h urine collection to quantitate the excretion of albumin as a measure of glomerular injury. In transgene-negative littermates (n = 15), transgene-positive animals (n = 10), and transgene-positive animals fed zinc (n = 10), albuminuria was 4,393 +/- 948, 1,783 +/- 454, and 1,057 +/- 277 microg/mg creatinine, respectively (P < 0.01 by ANOVA). Glomerular C3 was evident by immunofluorescence staining in 12/15 transgene-negative animals, but in none of the transgene-positive animals fed zinc. Thus, we have produced the first transgenic animals that overexpress a soluble C3 convertase inhibitor. rsCrry expression markedly ameliorates an Ab-induced disease model in vivo. These results support the hypothesis that continuous complement inhibition at the C3 convertase step is feasible and effective in complement-mediated injury states.
Animals↗
Inhibition of complement regulation is key to the pathogenesis of active Heymann nephritis.
Crry (complement receptor 1-related protein/gene y) is a key cellular complement regulator in rodents. It is also present in Fx1A, the renal tubular preparation used to immunize rats to induce active Heymann nephritis (HN), a model of membranous nephropathy. We hypothesized that rats immunized with anti-Fx1A develop autoantibodies (auto-Abs) to Crry as well as to the megalin-containing HN antigenic complex, and that anti-Crry Abs promote the development of injury in HN by neutralizing the complement regulatory activity of Crry. Rats immunized with Fx1A lacking Crry remained free of proteinuria and glomerular deposits of C3 during a 10-wk follow-up despite typical granular immunoglobulin (Ig)G deposits in glomeruli. Anti-Fx1A auto-Abs were present in their sera at levels that were not different from sera pooled from proteinuric rats with HN induced with nephritogenic Fx1A. Passive administration of sheep anti-Crry Abs to rats immunized with Crry-deficient Fx1A led to proteinuria and glomerular C3 deposition, which were not seen in such rats injected with preimmune IgG, nor in rats with collagen-induced arthritis injected with anti-Crry IgG. To directly examine the role of Crry in HN, rats were immunized with Crry-deficient Fx1A reconstituted with rCrry. This led to typical HN, with 8 out of 15 rats developing proteinuria within 14 wk. Moreover, the extent of glomerular C3 deposition correlated with proteinuria, and anti-Crry Abs were present in glomerular eluates. Thus, Crry is a key nephritogenic immunogen in Fx1A. Formation of neutralizing auto-Abs to Crry impairs its function, leading to unrestricted complement activation by Abs reactive with the HN antigenic complex on the epithelial cell surface.
Animals↗
Blockade of antibody-induced glomerulonephritis with Crry-Ig, a soluble murine complement inhibitor.
A recombinant soluble form of the mouse membrane complement inhibitor Crry (complement receptor-related gene y) fused to IgG1 hinge, CH2, and CH3 domains has been created and designated Crry-Ig. Crry has been used because, similar to human soluble CR1, it demonstrates decay-accelerating activity for both the classical and alternative pathways of complement as well as cofactor activity for factor I-mediated cleavage of C3b and C4b. The mouse IgG1 isotype was incorporated because it is a noncomplement-activating isotype and, when fused to Crry, results in a complement inhibitor that should not be recognized as foreign when used chronically in murine models. Crry-Ig demonstrated complement-inhibitory activity in both the fluid phase and on target surfaces. Following in vivo injection, Crry-Ig manifested a two-phase serum elimination profile, a rapid initial loss most likely reflecting tissue redistribution and a second more prolonged decline with a t1/2 of 40 h. Inhibition of complement activation in mice following injection of Crry-Ig was demonstrated by a marked decrease in the ability of serum from treated mice to be activated by zymosan particles in vitro. Finally, in vivo efficacy of Crry-Ig was demonstrated by its ability to substantially diminish renal injury induced by complement-fixing nephrotoxic Ab. The use of Crry-Ig in vivo in murine models of chronic inflammatory and autoimmune disease should allow further insight into the potential therapeutic effects and possible untoward complications of continuous blockade of complement using inhibitors that act on activation products of C4 and C3.
Animals↗
Beyond drug therapy: nonpharmacologic care of the patient with advanced heart failure.
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Aged↗
Immune complex glomerulonephritis in C4- and C3-deficient mice.
In this study, we examined the roles of C4 and C3 in immune complex glomerulonephritis by actively immunizing C4-deficient (C4 -/-), C3 deficient (C3 -/-) and wild-type mice with apoferritin. Wild-type animals with an intact complement system produced anti-apoferritin IgG and IgM antibodies, and developed mesangial proliferative glomerulonephritis characterized by hypercellularity, matrix expansion, deposition of IgG, IgM, IgA and C3, and the presence of electron dense deposits. In the majority of animals, the peripheral capillaries also contained IgG, C3 and subendothelial and subepithelial electron dense deposits. In contrast to wild-type animals, all apoferritin-immunized C4 -/- and C3 -/- mice had serum cryoprecipitates containing polyclonal IgM and the variable presence of polyclonal IgG. These animals also developed immune complex glomerulonephritis, but their disease manifestations were distinctly different from that of their wild-type littermates. In apoferritin-immunized C4 -/- and C3 -/- mice, IgG was either absent or present in reduced quantities in glomeruli, yet IgM and IgA were present in greater intensity in glomeruli. Capillary wall IgG deposits were absent in all C4 -/- and C3 -/- animals. C4 -/- animals also had significant glomerular C3 deposition, hypercellularity and neutrophil infiltration, which were not present in C3 -/- animals. These results illustrate the complex interplay between the effects of complement to process immune complexes and to lead to inflammation and tissue injury.
Animals↗
Anti-vitronectin antibodies enhance anti-Thy-1-induced proteinuria in PVG/c, but not in Wistar rats.
Injection of rats with mouse monoclonal IgG2a anti-Thy1.1 antibodies (ER4G) results in rapid development of proteinuria in Wistar rats, reaching average values of 160 mg/24 h on day 3 after antibody administration. In contrast, no overt proteinuria was observed in PVG/c+ rats (maximum, 40 mg/24 h on day 3). This study investigates whether differences in the inactivation of C5b-9 complexes in the glomerulus by complement inhibitors are responsible for the differences in proteinuria between the two rat strains. Regardless of the presence of proteinuria, an increased expression of Crry by mesangial cells (MC) was observed within 24 h after injection of ER4G in both Wistar and PVG/c+ rats. Double-label immunofluorescence using goat anti-mouse Ig antibodies demonstrated an expression of Crry exclusively on MC. Furthermore, Crry colocalized with C5b-9 complexes on MC, as detected by a monoclonal antibody against the rat C5b-9 neo-antigen. In PVG/c+ rats, C5b-9 complexes persisted in the mesangial area for at least 7 d and colocalized immediately (within 1 h) and homogeneously with vitronectin. However, in proteinuric Wistar rats, C5b-9 complexes disappeared from the glomerular mesangium within 6 d. In these rats, mesangial colocalization of C5b-9 with vitronectin could only occasionally be detected. Pretreatment of PVG/c+ rats with antibodies against vitronectin, followed by administration of ER4G, resulted in the immediate development of proteinuria (maximum, 119 mg/24 h on day 3; P < 0.05), whereas Wistar rats did not become more proteinuric. This study provides evidence that differences in susceptibility of PVG/c+ and Wistar rats to complement-mediated damage of the glomerulus may be related to the degree of inactivation of C5b-9 complexes by complement regulatory factors.
Animals↗