A nephrological view of the classification of vasculitis

From the nephrologic perspective, a nomenclature system has been proposed that is clinically useful for diagnosis, classification and therapy. This nomenclature allows the nephrologist to consider the best approach to ANCA positive patients with necrotizing and crescentic glomerulonephritis. It allows for better understanding of the extra-renal manifestations of disease especially those with pulmonary-renal syndrome. The classification system allows for the rapid introduction of immunosuppressive therapy in individuals without repetitive search for specific pathological features on biopsy. This classification system allows for the possibility that all of these conditions are pathogenically related. As such, it separates this group of diseases from those which are attributable to immune complex disease or direct antibody binding. For this nomenclature system to stand the test of time it must be simple, logical and clinically usefully. While not yet perfected, the working nomenclature for ANCA-associated diseases is a step forward.

Acute renal failure secondary to leukocyte-mediated acute glomerular injury

Acute glomerulonephritis can cause acute renal failure. Activated neutrophils and monocytes are major effectors of glomerulonephritic renal failure. Adhesion molecules, granule enzymes, reactive oxygen radicals, lipid metabolites, and cytokines of activated neutrophils and monocytes mediate glomerular capillary constriction, occlusion, and destruction. Injurious products and biologically active mediators released by activated leukocytes have profound functional effects on mesangial cells and endothelial cells, which in turn participate in the disturbance of glomerular function, for example, by altering capillary diameter and surface area. The glomerular inflammatory events result in decreased glomerular capillary ultrafiltration coefficient and glomerular filtration rate, as well as other functional perturbations.

Interleukin-18, neutrophils, and ANCA

Hewins et al. show that IL-18 is expressed in the kidneys of patients with ANCA-associated glomerulonephritis, and that IL-18 primes neutrophils via p38 MAPK. These findings suggest a role for IL-18, including IL-18-induced T(H)1 polarization and IFN-gamma production, in the progression of ANCA disease.

Hematometra associated with estrogen replacement therapy

We have described two cases of hematometra occurring after initiation of estrogen replacement therapy. In both cases, cervical stenosis had developed during a prolonged period of hypoestrogenism. After initiation of sequential estrogen/progestin therapy, the stenosis prevented menstrual flow, and sonography revealed an asymptomatic hematometra in both cases. Based on these cases, we recommend doing a baseline evaluation of cervical patency before initiating estrogen replacement therapy in women who have been menopausal for a substantial length of time.

Neonatal foreskin substrate has limitations for the immunofluorescent screening of monoclonal antibodies

Two monoclonal antibodies to type IV collagen showed a marked decrease in the labeling of the dermal-epidermal junction of neonatal foreskin while the basement membrane around dermal blood vessels was brightly stained. In contrast, these antibodies labeled the junction and dermal blood vessels with approximately equal intensity when adult skin of nonforeskin site was used as substrate. Other antibodies to matrix molecules (bullous pemphigoid antigen, epidermolysis bullosa acquisita antigen, and laminin) showed excellent staining of both the dermal-epidermal junction and dermal blood vessels in both neonatal foreskin and adult skin. Further, the ultrastructural appearance of the substrates appeared identical. The implication is that neonatal foreskin is not a good substrate to use for the routine screening of monoclonal antibodies to matrix components by indirect immunofluorescence since a "false negative" evaluation may occur.

Epigenetics and complementary proteins

Although studies on the immunopathogenesis of anti-neutrophil cytoplasm antibody (ANCA) vasculitis have been directed at understanding the autoantibody, there is growing evidence that points to the importance of ANCA autoantigen genes and their regulation. Transcriptional analysis indicates that ANCA autoantigen genes are active in mature neutrophils of ANCA vasculitis patients compared to healthy controls. The unusual transcriptional state of neutrophils from ANCA vasculitis patients appears to be a consequence of failed or disrupted epigenetic silencing. Defective epigenetic silencing could have global effects, by altering the transcriptional and phenotypic state of neutrophils, or local effects by permitting transcription of autoantigen genes from both strands resulting in anti-sense transcripts. Although the role of anti-sense transcripts is currently unknown, there are two intriguing possibilities. Anti-sense transcripts could function (as described for other genes) in transcriptional silencing of autoantigen genes, which takes place in normal neutrophil progenitors. In the setting of failed epigenetic silencing, the fate of anti-sense transcripts may be pathological and serve as a template for production of complementary autoantigens. The observation that ANCA vasculitis patients have anti-sense transcripts and antibodies to complementary proteins is consistent with a role of anti-sense transcripts in complementary protein production. A better understanding of epigenetic silencing and complementary proteins in ANCA vasculitis may unlock the underlying pathology of this condition.

Wegener's granulomatosis mimicking a sternal abscess

Bone destruction as a manifestation of Wegener's granulomatosis has been reported, but these cases were limited to the head and face. We present a case in which a sternal abscess was the initial manifestation of Wegener's granulomatosis. We believe this is the first reported case of bone destruction due to Wegener's occurring in a location other than the head and face.

Localization of S protein and its relationship to the membrane attack complex of complement in renal tissue

The S protein (S) binds to the attack complex of complement (C5b-9) in plasma preventing cytolysis. Using immunofluorescence microscopy, the authors determined the distribution of S in human renal tissue and its relationship to C5b-9, immunoglobulins, C3, albumin, and fibronectin. They examined normal and diseased human kidney tissue from patients with several forms of glomerulonephritis, diabetic nephropathy, and arterionephrosclerosis. S and C5b-9 were found in all diseased tissues; their amounts and distribution directly correlated with severity and location of injury. S and C5b-9 were colocalized in all immune deposits and in all injured glomeruli, tubular basement membranes, and vessel walls. Other than within immune deposits, S and C5b-9 were usually not colocalized with C3. This study demonstrates that S is deposited in areas of tissue injury and thus may participate in the pathogenesis of renal damage. Because in tissue S and C5b-9 are always associated, the attack complex in tissue must either be derived from the circulation as SC5b-9 or it must be capable of binding S after the formation in situ of C5b-9.

Subtotal nephrectomy in the rabbit: a model of chronic hypercalcemia, nephrolithiasis, and obstructive nephropathy

The association of a critical reduction in renal mass with the subsequent destruction of remaining nephrons has been observed in several species. We studied this process in experimental rabbits after 1 2/3 nephrectomy to define the course and its pathogenesis in this species. Control rabbits underwent sham operative procedures. After renal ablation, rabbits became increasingly cachectic and developed polyuria and hypertension. Despite food intake similar to that of controls (grams per kilogram per day), experimental rabbits developed severe hypercalcemia by 5 to 8 weeks after renal ablation, a change that persisted until death. During the study 17 experimental animals died of uremia 9 to 27 weeks after surgery, and the remaining seven experimental and 25 sham-operated rabbits were sacrificed at 5 to 7 months. At death, 19/24 experimental rabbits had severe obstruction of their collecting systems by concretions of gravel (n = 3) or large calcium carbonate stones (n = 16). Renal biopsy at 4 weeks revealed focal interstitial round cell infiltration progressing by 12 weeks to diffuse tubulointerstitial inflammation and fibrosis. Histologic evidence of obstruction was also evident at this time and became extensive on all subsequent examinations. By contrast, the glomeruli remained well preserved without evidence of sclerosis. We speculate that chronic hypercalcemia and, perhaps more significantly, urinary obstruction may have altered intrarenal hemodynamics and prevented the development of progressive sclerosis observed in the rat remnant kidney model. The present study describes an experimental model of chronic hypercalcemia and spontaneous calcium carbonate nephrolithiasis.

Amelioration of immune complex-mediated glomerulonephritis by synthetic protease inhibitors

Proteases are involved in the pathogenesis of inflammatory diseases by participating in the activation of mediator systems and by producing proteolytic tissue injury. Homeostatic control of inflammation is accomplished in part by physiologic protease inhibitors. The authors investigated the effectiveness of a number of synthetic protease inhibitors in ameliorating the glomerular injury induced by immune complex-mediated glomerulonephritis in mice. Two amidine-type protease inhibitors, bis (5-amidino-2-benzimidazolyl)methane and 1,2-bis (5-amidino-2-benzimidazolyl)ethane, had the greatest effects. They caused a marked reduction in glomerular necrosis (P less than 0.001) but did not affect the amount or site of immune complex localization or leukocyte influx. The inhibition constants of the protease inhibitors against nine purified physiologic proteases were determined. These results were discussed in relation to the effectiveness of the protease inhibitors in reducing glomerular injury. This investigation indicates that the administration of synthetic protease inhibitors can have a beneficial effect on immune-mediated inflammatory injury.

Do antineutrophil cytoplasmic autoantibodies cause Wegener's granulomatosis and other forms of necrotizing vasculitis?

The in vitro experimental observations support the theoretical pathogenic scenario depicted in Figure 14. A similar scenario could be portrayed for monocytes. ANCA in the circulation are unable to interact with unprimed neutrophils because the target antigens are within the cytoplasm (Fig. 14A). Synergistic priming of neutrophils, e.g., by an infection, causes small amounts of target antigens to be released at the cell surface (Fig. 14B) where they can interact with ANCA (Fig. 14C). ANCA-activated neutrophils then adhere to endothelial cells via adhesion molecule interactions that may require prior priming of the endothelial cells (Fig. 14C). These activated and adherent neutrophils then injure endothelial cells (and eventually underlying vessel wall structures) by releasing granule enzymes and toxic oxygen metabolites (Fig. 14D). Although many research groups throughout the world have been attempting to create an animal model of ANCA-induced disease based on the theoretical paradigm proposed in Figure 14, as well as on other paradigms, no one has reported complete success. Until this is accomplished, the role of ANCA in the pathogenesis of Wegener's granulomatosis and other forms of ANCA-associated vasculitides will remain conjectural.

Shared idiotypy among patients with myeloperoxidase-anti-neutrophil cytoplasmic autoantibody associated glomerulonephritis and vasculitis

Anti-neutrophil cytoplasmic autoantibodies (ANCA) have been hypothesized to participate in the pathogenesis of necrotizing vasculitis based on their association with small vessel vasculitides and the in vitro ability of such antibodies to activate cytokine-primed neutrophils. Much remains to be elucidated about the factors responsible for the generation and perpetuation of these autoantibodies and the shaping of the ANCA immune response. This study evaluated the clonal diversity of the ANCA immune response in patients with myeloperoxidase-ANCA associated disease. Isoelectric focusing was used to investigate the clonality of myeloperoxidase-ANCA from 34 patients with pauci-immune necrotizing glomerulonephritis. Sixty-nine percent of the patients had two or less clonotypes to myeloperoxidase, whereas 31% had more than two clonotypes. Clonality was stable over the course of the disease and shared among some unrelated patients. Shared idiotypy was specifically investigated using a murine monoclonal anti-idiotype (7F2C11) to the anti-myeloperoxidase antibodies of one patient with ANCA associated vasculitis. This monoclonal antibody was selected by demonstrating: (1) binding to the proband's affinity purified anti-myeloperoxidase antibodies; (2) an inhibitory effect on the binding of the proband's anti-myeloperoxidase to myeloperoxidase; and (3) lack of binding to control human antibody preparations, or to the proband's crude immunoglobulin preparation, thus excluding an anti-allotype antibody. Purified 7F2C11 was immobilized on Sepharose, and this monoclonal anti-idiotype affinity column was used to search for a shared anti-myeloperoxidase idiotype in the plasma of four other patients with myeloperoxidase-ANCA associated disease. Using this column, we were able to extract anti-myeloperoxidase antibodies from plasma of the other patients but not from control antibody preparations. We concluded that most myeloperoxidase-ANCA patients have a restricted response to myeloperoxidase and that some patients share a common idiotype. The demonstration of shared idiotypy suggests a restricted number of autoreactive epitopes of the myeloperoxidase molecule, or that some anti-myeloperoxidase autoantibodies are encoded by germ line genes, or both.

Apoptosis of endothelial cells induced by the neutrophil serine proteases proteinase 3 and elastase

The pathogenesis of vasculitis associated with anti-neutrophil cytoplasmic antibodies is not established. The anti-neutrophil cytoplasmic antibody autoanigens proteinase 3 (PR3) and elastase induce detachment and cytolysis of endothelial cells in vitro. We investigated whether PR3 and elastase trigger endothelial cell apoptosis. Primary bovine pulmonary artery endothelial cells were treated with either PR3, elastase, or myeloperoxidase (MPO) and apoptosis assessed by four different methods. By the cell death detection enzyme-linked immunosorbent assay, DNA fragmentation increased to 208 +/- 84% or 153 +/- 27% of control with 1 micrograms/ml PR3 or elastase at 24 hours. By ultraviolet light microscopy, the percentage of apoptotic cells significantly increased (P < 0.05) with 5 or 10 micrograms/ml PR3 and 25 or 50 micrograms/ml elastase at 6, 12, or 24 hours. Values at the 24-hour time point are 15.3 +/- 6.4% or 25.8 +/- 6.6% for 5 or 10 micrograms/ml PR3 and 13.9 +/- 3.6% or 20.7 +/- 1.8% for 25 or 50 micrograms/ml elastase compared with 2.2 +/- 1.2% for control. Similarly, with flow cytometry, 5 or 10 micrograms/ml PR3 and 25 or 50 micrograms/ml elastase for 6, 12, or 24 hours demonstrated increasing apoptosis in a dose- and time-dependent manner with the highest values achieved at 24 hours (23.4 +/- 4.0% and 35.6% for 5 and 10 micrograms/ml PR3 and 31.8 +/- 4.0% and 47.8% for 25 and 50 micrograms/ml elastase compared with 7.9 +/- 2.2% in control). Typical DNA laddering was apparent from 6 to 24 hours at 5 or 10 micrograms/ml PR3 and 25 or 50 micrograms/ml elastase. Myeloperoxidase did not induce cell apoptosis. Release of PR3 and elastase by activated neutrophils during acute inflammation, including anti-neutrophil cytoplasmic antibody-associated vasculitis, may result in vascular damage by endothelial cell apoptosis.

Cumulative ovulation rate in human menopausal/human chorionic gonadotropin-treated monkeys: "step-up" versus "step-down" dose regimens

Cumulative ovulation rates in monkeys given human menopausal gonadotropin/human chorionic gonadotropin (hMG/hCG) on menstrual cycle days 3 to 9 in a "step-up" versus "step-down" protocol were compared with those achieved by hMG only. Using direct ovarian observation to detect sites of follicular rupture, retrograde tubal irrigation to collect eggs or embryos, and serum estradiol and progesterone levels to infer changes in ovarian status, we counted the number of ovulations at intervals of 24, 48, 72, 96, and 120 hours after hCG or comparable intervals without hCG. The data indicate (1) whereas most ovulations occurred on or before day 3 after hCG treatment, when the "step-up" dose regimen was employed additional follicles had ruptured on days 4 and 5; (2) a "step-down" protocol for hMG therapy may better synchronize follicular rupture and reduce susceptibility to delayed ovulations compared with a "step-up" dose regimen; and (3) under hMG stimulation, few follicles would rupture spontaneously (without hCG or luteinizing hormone treatment).

Membrane attack complex of complement in dermatitis herpetiformis

The assembly of membrane attack complex (MAC) of complement implies activation of complement to the attachment of C9 and the presence of MAC on tissue suggests a possible pathogenic role for complement in disease since MAC is able to damage membranes. We examined normal skin of five patients with dermatitis herpetiformis for the presence of MAC using a monoclonal antibody (poly C9-MA) that recognizes a neoantigen of C9 that is not present on monomeric C9 but is common to both isolated MAC and to polymerized C9. Granular deposits of polymerized C9 were found at the sites of IgA deposition in the dermal papillae of normal skin from all patients. The pathologic importance of this finding is uncertain.

Anti-neutrophil cytoplasmic autoantibodies--a serologic marker for vasculitides

Anti-neutrophil cytoplasmic autoantibodies (ANCA) have specificity for proteins in the cytoplasmic granules of neutrophilic and the lysosomes of monocytes. ANCA occur in a high proportion of patients with Wegener's granulomatosis, microscopic polyangiitis (microscopic polyarteritis), Churg-Strauss syndrome and certain forms of drug-induced vasculitis. ANCA with different specificities from those in patients with vasculitis occur in patients with inflammatory bowel disease and rheumatoid arthritis. ANCA titres correlate to a degree with disease activity and response to treatment. ANCA are a useful diagnostic marker but because of the low prevalence of ANCA-associated diseases, their positive predictive value is good only in patients with signs and symptoms of vasculitis. In vitro data indicate that ANCA can activate cytokine-primed neutrophils and monocytes, causing them to degranulate, release toxic oxygen metabolites, adhere to endothelial cells, and kill endothelial cells. If these events occur in vivo, ANCA may be directly involved in the pathogenesis of vasculitis.

Studies on complement deposits in epidermolysis bullosa acquisita and bullous pemphigoid

Epidermolysis bullosa acquisita (EBA) is an inflammatory subepidermal blistering disease characterized by circulating and tissue-bound autoantibodies specific for type VII collagen of the basement membrane zone. The antibodies consist of both complement- and noncomplement-binding populations and belong to all four subclasses of IgG. We investigated the presence of the membrane attack complex C3b, C5, and S protein in EBA and compared C3b and C5 in EBA and bullous pemphigoid. In 10 patients with EBA, these components were detected at the basement membrane zone as follows: membrane attack complex, 90%; S protein, 90%; direct C5, 90%; C3b, 100%; and C5 binding, 90%. In the patients with bullous pemphigoid, the results were as follows: direct C5, 58%; C3b, 33%; and C5 binding, 19%. These results provide additional evidence for complement activation at the basement membrane zone in EBA, show that complement activation in EBA proceeds to activation of terminal complement components, and suggest that EBA antibodies are more potent activators of C5 than are bullous pemphigoid antibodies.