Autoimmunity in rapidly progressive glomerulonephritis

Pauci-immune glomerulonephritis in a captive chimpanzee (Pan troglodytes), and a review of spontaneous cases in animals

BACKGROUND

Crescentic glomeruli are the hallmark finding in rapidly progressive glomerulonephritis (RPGN) and are characterized by disruption and proliferation of the glomerular capsule and an influx of cells into Bowman's space. Pauci-immune-type RPGN is identified by a lack of immunoglobulins and immune complexes in the glomerular basement membrane.

METHODS

Complete necropsy and histology were performed on the affected chimpanzee. Electron microscopy was performed on kidney sections. A search of the literature was performed to identify spontaneous RPGN in animals.

RESULTS

We report a case of crescentic glomerulonephritis of the pauci-immune-type in a hepatitis C virus-infected 28-year-old male chimpanzee (Pan troglodytes) who was humanely euthanized for a cardiac-related decline in health.

CONCLUSION

To our knowledge, this is the first report describing pauci-immune crescentic glomerulonephritis in a non-human primate.

Crescentic glomerulonephritis in a polar bear (Ursus maritimus)

Spontaneous crescentic glomerulonephritis (CrGN) in animals has only been reported in dog and sheep. We report the pathological features of CrGN in a 17-year-old male polar bear that died due to renal failure. Histologically, the lesions were characterized by fibrocellular crescents, adhesion between Bowman's capsule and the glomerular capillary tuft and an increase in the mesangial matrix in glomeruli. The proliferating cells in the crescent were partly immunopositive for cytokeratin and intensely positive for vimentin, WT-1 and α-smooth muscle actin, suggesting they originated from parietal epithelial cells. Ultrastructually, thickening of the glomerular basement membrane and loss of epithelial cell foot processes were observed with electron-dense deposits.

The pulmonary-renal syndrome: a poorly understood clinicopathologic condition

The co-existence of pulmonary hemorrhage and glomerulonephritis delineates a severe syndrome, often underestimated, resulting from several diseases and frequently associated with serum positivity for antineutrophil cytoplasmic antibodies (ANCA) or antiglomerular basement membrane (GBM) antibodies. The most common illness presenting as pulmonary-renal syndrome is systemic vasculitis. Moreover, the idiopathic pulmonary-renal syndrome is a distinctive clinicopathologic entity with different pathogenetic mechanisms. Tissue immunofluorescence studies are fundamental in distinguishing anti-GBM antibody-mediated forms from immune-complex-mediated and ANCA-associated forms. The type of glomerular or alveolar immunologic injury is the main factor determining the outcome and thus the prognosis of the pulmonary-renal syndrome. Development and improvement of appropriate serologic detection techniques have given reliable and early guidance for diagnosing these cases.

Antineutrophil cytoplasmic antibodies as markers for systemic autoimmune disease

Antineutrophil cytoplasmic antibodies (ANCA) have been associated with systemic vasculitis for almost 15 years. Significant advances in our understanding of the ANCA phenomenon have occurred with recognition of broadening the spectrum of diseases associated with ANCA, identification of specific antigens recognized by ANCA, and development of antigen specific assays for clinical use. Nevertheless problems continue for the chest physician in interpretation of this test. Although antigen specific testing improves overall performance of the test, accurate assessment of pretest probability of disease is still important for effective use of ANCA testing.

The alpha 3 chain of type IV collagen induces autoimmune Goodpasture syndrome

Human Goodpasture syndrome is a lethal form of autoimmune disease that is characterized by pulmonary hemorrhage and glomerulonephritis. The tissue injury is mediated by autoantibodies that bind to glomerular and alveolar basement membrane. The target autoantigen is alpha 3(IV) collagen, one of six genetically distinct chains that comprise type IV collagen, and the epitope is sublocalized to the noncollagenous domain (NC1) of the alpha 3 chain. The present study reports the unique capacity of alpha 3(IV)NC1 dimer from bovine kidney to aberrantly engage the immune system of rabbits to respond to self, mimicking the organ-specific form of the human disease, whereas the other chains of type IV collagen are nonpathogenic. However, alpha 3(IV)NC1 hexamer was nonpathogenic, suggesting the exposure of a pathogenic epitope upon dissociation of hexamer into dimers. Exposure of the pathogenic epitope by infection or organic solvents, events which are thought to precede Goodpasture syndrome, may be the principal factor in the etiology of the disease. The pathogenicity of alpha 3(IV) collagen brings full circle a decade of research that has identified four novel chains (alpha 3-alpha 6) of type IV collagen.

Activation of autoreactive T-lymphocytes by cultured syngeneic glomerular mesangial cells

The capacity of intrinsic, glomerular mesangial cells (MC) to cause an autoreactive response of syngeneic lymphocytes in vitro are presented. Initial experiments demonstrated the MHC class II dependent capacity of MC to present exogenous antigen to sensitized lymph node lymphocytes (LN) and to activate naive, allogeneic LN in the absence of a nominal antigen. However, the most striking finding of the present investigation was that mouse MC (C57BL/6 or DBA/2) augmented a significant activation of naive, syngeneic lymphocytes. The extent of the proliferative lymphocyte response was comparable to that observed after stimulation with allogeneic MC. Moreover, during syngeneic coculture substantial amounts of interferon bioactivity were generated. Equipotent concentrations of rm IFN-gamma were sufficient to induce class II MHC expression of mouse MC. In control experiments the macrophage cell line, IC-21 (C57BL/6), or freshly prepared DBA/2 mouse peritoneal macrophages did not elicit a syngeneic LN response. Using MC, which had not been pretreated, the MC-specific LN stimulation occurred after prolonged periods of coculture. The stimulation index (S.I.) was 9.77 after 144 hours compared with LN controls (S.I. = 1). However, a 48 hour pretreatment of MC with either rm IFN-gamma alone or in combination with rh TNF-alpha and/or the continuous presence of rm IL-1 alpha during coculture periods from 72 to 144 hours substantially enhanced the proliferative LN response. Analysis of non-adherent LN by flow cytometry (FACS) after 96 or 120 hours coculture with MC revealed an increased ratio of Thy1.2+ to B220+ cells with a predominant rise of L3T4+ T-helper cells compared to Lyt2+ cytotoxic T-cells. Furthermore, immune fluorescence microscopy showed that a fraction of Thy1.2+ lymphoblasts adhered to MC. FACS analysis of these adherent LN after detachment demonstrated that in comparison to cocultures with untreated MC, cocultures of LN with IFN-gamma/TNF-alpha pre-treated MC resulted in a 24.4% increase of Thy1.2+ cells, with 89% of these being L3T4+ T-helper lymphocytes. In conclusion, autoreactivity of preferentially T-helper cells to cocultured glomerular MC was shown, which may represent a useful model of T-lymphocyte dependent glomerulonephritis.

Glomerulonephritis associated with antibodies to neutrophil cytoplasm and glomerular basement membrane

The prognosis for recovery of renal function of oligoanuric patients with anti-glomerular basement membrane disease is generally regarded as poor. Five patients are reported with dialysis-dependent renal failure in whom antibodies were present simultaneously both to neutrophil cytoplasm and glomerular basement membrane all of whom responded, at least initially, to immunosuppressive therapy and plasma exchange. Two of the 5 remain in clinical and immunological remission at 25 and 51 months of follow-up. We suggest that reversal of dialysis-dependent renal failure may be possible in some patients who display this dual antibody positivity.

Autoantibodies to native myeloperoxidase in patients with pulmonary hemorrhage and acute renal failure

Sera from 245 patients were screened by indirect immunofluorescence for perinuclear/nuclear staining (P-ANCA) of ethanol-fixed neutrophils, a staining pattern which is associated with the presence of antibodies to myeloperoxidase. Using immunoblot and immunoprecipitation techniques on 15 P-ANCA-positive sera, 13 patients demonstrated antibody to purified or native myeloperoxidase but not to denatured myeloperoxidase. In patients with P-ANCA, the most frequent reason for medical attention was hemoptysis (8/13; 62%). Of the 15 sera with P-ANCA, acute renal failure was identified in 9 patients (60%). Five patients (33%) had both. All patients (eight of eight) with hemoptysis had antibodies which bound functional MPO as compared to three of seven P-ANCA-positive patients without hemoptysis (P less than 0.001), suggesting that antibodies which recognize conformational sites on native myeloperoxidase occur in a subgroup of patients with alveolar hemorrhage as their presenting clinical sign. These findings may provide insight into the disease process associated with P-ANCA. We further identify a subgroup of patients with a severe pulmonorenal syndrome and antibodies recognizing native myeloperoxidase.

Plasma exchange in focal necrotizing glomerulonephritis without anti-GBM antibodies

To determine whether plasma exchange was of additional benefit in patients treated with oral immunosuppressive drugs for focal necrotizing glomerulonephritis (without anti-GBM antibodies), we performed a randomized controlled trial with stratification for renal function on entry. Forty-eight cases were analyzed, 25 in the treatment group (plasma exchange, prednisolone, cyclophosphamide and azathioprine) and 23 in the control group (drug therapy only). There was no difference in outcome in patients presenting with serum creatinine less than 500 mumol/liter (N = 17), or greater than 500 mumol/liter but not on dialysis (N = 12), all but one of whom had improved by four weeks. However, patients who were initially dialysis-dependent (N = 19) were more likely to have recovered renal function (P = 0.041) if treated with plasma exchange as well as drugs (10 of 11) rather than with drugs alone (3 of 8). Long-term follow-up showed that improvement in renal function was generally maintained. The results of this trial confirm that focal necrotizing glomerulonephritis related to systemic vasculitis responds well to immunosuppressive drugs when treatment is started early, and suggest that plasma exchange is of additional benefit in dialysis-dependent cases.

Antineutrophil cytoplasmic antibody--a useful serological marker for vasculitis

Systemic necrotizing vasculitides, including polyarteritis nodosa, Churg-Strauss syndrome, "overlap" systemic vasculitis, Wegener's granulomatosis, and idiopathic crescentic glomerulonephritis, are frequent clinical diagnostic problems. These diseases have diverse presentations and are often rapidly progressive, causing irreversible injury to the vessels of the kidneys and lungs before effective immunosuppressive therapy is instituted. Even in their less fulminant forms, they are a cause of significant morbidity and mortality. Antineutrophil cytoplasmic antibody, a recently identified autoantibody, has a high sensitivity and specificity for this spectrum of diseases. The clinical and pathological similarities, the high frequency of antineutrophil cytoplasmic antibody expression, and the similar good response to immunosuppressive therapy suggest that these diseases may be linked by a common pathophysiological mechanisms. Evidence is growing that antineutrophil cytoplasmic antibody plays a central role in this mechanisms. A revision in the classification scheme of vasculitides to recognize that the polyarteritis group (polyarteritis nodosa, Churg-Strauss syndrome, and "overlap" systemic vasculitis), Wegener's granulomatosis, and idiopathic crescentic glomerulonephritis are closely related diseases may be warranted. The clinical and pathological features of systemic necrotizing vasculitides and the current knowledge concerning antineutrophil cytoplasmic antibodies are reviewed.

The antineutrophil antibody in uveitis

Ninety eight patients with uveitis of various types were tested for the presence of the antineutrophil antibody or ANCA by an indirect immunofluorescence method. This antibody is found in patients with diseases associated with small vessel vasculitis, including Wegener's granulomatosis and microscopic polyarteritis. Eleven true positive cases were found. A positive test was not associated with the anatomical site of the uveitis but was related to the time course of the disease. In particular single/repeated rather than nonrecurrent uveitis was associated with a positive test. Three groups of patients seem more likely to have positive tests: those with bilateral chronic posterior uveitis; a group with an anterior uveitis which is single/repeated who were younger than 46 at disease onset and had isolated eye disease; and an older group, aged 60 years or more at onset, with single/repeated uveitis and systemic features.

Towards a more rapid diagnosis of rapidly progressive glomerulonephritis

An attempt was made to provide simple practical guidelines to alert general practitioners to the diagnosis of rapidly progressive glomerulonephritis and lead to early referral to hospital. The duration of illness before referral to this hospital and its effect on outcome in patients with crescentic nephritis were assessed retrospectively from the case notes of 24 patients referred over two years. Four patients had Goodpasture's syndrome, 11 Wegener's granulomatosis, seven microscopic polyarteritis, and two idiopathic progressive glomerulonephritis. The duration of symptoms before referral to the local hospital was similar in the four groups of patients and varied from one week to 28 months (mean 10 months). The duration of stay in the local hospital was two, nine, 11, and 180 days in the patients with Goodpasture's syndrome and a mean of four days (range one to eight) in those with Wegener's granulomatosis and 10 days (one to 18 days) in those with microscopic polyarteritis. In the local hospital the diagnosis was based on the results of renal biopsy and detection of antibodies to glomerular basement membrane in two patients with Goodpasture's syndrome and on the results of renal biopsy in seven of the other patients aided by the detection of antibodies to the cytoplasm of neutrophils (ANCA) in 10. Three of the 24 patients died and four required maintenance haemodialysis. Patients who present to their general practitioners with persistent non-specific symptoms should have a urine dipstick test and then blood tests and emergency referral to hospital if necessary. Hospital physicians should be aware of the speed and accuracy with which current assays can confirm a diagnosis of rapidly progressive glomerulonephritis.

Immunoglobulin heavy chain switch region gene polymorphisms in glomerulonephritis

Much evidence suggests that primary IgA nephropathy (IgAN) and idiopathic membranous nephropathy (MN) are immune complex mediated diseases. Moreover, genetic factors may play an important role in their pathogenesis. Recently, restriction fragment length polymorphisms (RFLPs) of the immunoglobulin heavy chain genes have been described which appear to associate with glomerulonephritis. We have studied RFLPs of the switch region of the IgM (S mu) and IgA1 (S alpha 1) heavy chain in MN and IgAN. DNA obtained from British Caucasoids with IgAN (N = 75), MN (N = 43), and normal controls (N = 73), was digested with the restriction enzyme Sac1, and studied using Southern blot techniques and hybridization with a 32P labelled DNA probe homologous to S mu. This probe detects RFLPs at the S mu and S alpha 1 loci. The genotypic and allelic frequencies of the S mu and S alpha 1 alleles in IgAN and MN was similar to normal controls. Caucasoid subjects with IgAN from Northern and Southern Europe (Finland and Italy, respectively) were also studied to determine whether an ethnic variation in genetic susceptibility to IgAN exists. The frequency of the S mu and S alpha 1 alleles was similar between the patient groups and their respective local healthy controls. These results do not support the recent findings of an association with RFLPs of the S mu and S alpha 1 loci in IgAN and MN, and suggest that the immunoglobulin heavy chain switch region genes are not important in conferring disease susceptibility to IgAN or MN.

Anti-neutrophil cytoplasmic antibodies in uveitis

The antineutrophil cytoplasmic antibody test has become available over the past 4 or 5 years. It is positive in a limited number of conditions whose characteristic feature is the presence of a small vessel vasculitis. These include Wegener's granulomatosis and microscopic polyarteritis. The test was applied to 63 patients with uveitis of various types. 14 positive tests were found amongst which anterior uveitis was the most common disease present.