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.

Prognostic markers in patients with antineutrophil cytoplasmic autoantibody-associated microscopic polyangiitis and glomerulonephritis

The purpose of this study was to determine the prognostic value of clinical, laboratory, and pathologic features at the time of presentation on patient and renal survival in patients with antineutrophil cytoplasmic autoantibody (ANCA)-associated microscopic polyangiitis and glomerulonephritis (excluding Wegener's granulomatosis). One hundred seven ANCA-positive patients with necrotizing and crescentic glomerulonephritis, including 69 with evidence for microscopic polyangiitis, were evaluated for this study. The relative risk of death was calculated for the following potential prognostic indicators: (1) ANCA pattern; (2) pulmonary hemorrhage at onset; (3) presence of extrarenal manifestations versus renal limited disease; and (4) treatment with corticosteroids and cyclophosphamide (intravenous or oral), compared with corticosteroids alone. Cox's proportional hazard model was used to assess the predictive value of the following variables on renal survival: (1) age; (2) race; (3) pulmonary symptoms at onset of disease; (4) renal pathology; (5) ANCA pattern; and (6) peak serum creatinine values obtained near the time of renal biopsy. Patients were followed prospectively for 2.5 yr (range, 5 days to 12 yr 2 months). There were 12 disease-related deaths and 46 patients who reached ESRD. The relative risk (and 95% confidence interval) of patient death was 8.65 (3.36, 22.2) times greater in patients who presented with pulmonary hemorrhage, and 3.78 (1.22, 11.70) times greater in patients with cytoplasmic ANCA compared to those with perinuclear ANCA. The relative risk of pulmonary hemorrhage was no different by ANCA pattern. The risk of death was 5.56 times lower in the cyclophosphamide-treated patients versus those treated with corticosteroids alone. The predictors of renal survival were entry serum creatinine value (P = 0.0002), race (African Americans having a worse outcome compared with Caucasians, P = 0.0008), and the presence of arterial sclerosis on kidney biopsy (P = 0.0076) when controlling for age, ANCA pattern, microscopic polyangiitis versus glomerulonephritis alone, and pulmonary involvement. Pathology indices such as glomerular necrosis, glomerular crescents, glomerular sclerosis, and interstitial sclerosis were not predictive of renal survival when controlling for entry serum creatinine value, race, and arterial sclerosis. However, in the subgroup of patients with a peak creatinine value of < or = 3.0 mg/dL (N = 29), increased interstitial sclerosis was a predictor of a poor renal outcome (P = 0.04).

Treatment response and relapse in antineutrophil cytoplasmic autoantibody-associated microscopic polyangiitis and glomerulonephritis

In this study, the rate of remission, relapse, and treatment resistance in 107 patients with microscopic polyangiitis and necrotizing and crescentic glomerulonephritis associated with antineutrophil cytoplasmic autoantibodies were assessed. Patients with Wegener's granulomatosis were excluded. Prospective criteria were identified to assess remission, relapse, and resistant disease. Ninety-seven of the 107 patients received treatment with corticosteroids (N = 25) or with cyclophosphamide and corticosteroids (N = 72). Of these patients, 75 (77.3%) went into remission (complete remission, N = 61; remission on therapy, N = 14). Of the 75 responders, 32 patients (43%) remained in long-term remission, for a mean follow-up of 44 +/- 29 months; 15 patients (20%) progressed to ESRD without signs of relapse, for a mean of 21.4 +/- 22.8 months after the end of treatment; 6 patients died. Twenty-two of the 75 patients who initially responded to treatment (29%) suffered a relapse that occurred within 18 months of the end of therapy and usually affected the same organ systems as on initial presentation. There was a significant difference in the remission rate between the corticosteroid-treated patients and the cyclophosphamide-treated patients (56% versus 84.7%, P = 0.003), and the cyclophosphamide-treated patients had three times less risk of experiencing a relapse than did corticosteroid-treated patients (0.31, 95% Cl = (0.12, 0.84)). Seventy-seven percent (17 of 22 patients) of treatment resistance occurred in patients who presented with fulminant disease or advanced and severe renal disease. It was concluded that most patients with microscopic polyangiitis or necrotizing and crescentic glomerulonephritis achieve remission with therapy. Relapses occur in 29% of patients and generally respond to retreatment. Initial treatment with cyclophosphamide and corticosteroids rather than corticosteroids alone results in a lower frequency of relapse. Even patients who require dialysis at presentation may benefit from treatment, however, patients who are not treated until the disease process is life-threatening may die before induction therapy is complete, indicating the continued need for early diagnosis and therapy.

Animal models in ANCA-vasculitis

The animal models described to date suggest pathogenicity of ANCA. Unfortunately, none of the models unequivocally proves that ANCA are pathogenic. Further search for a suitable animal model to document or exclude causal significance of ANCA in vasculitis is needed.

The pathologic spectrum of pulmonary lesions in patients with anti-neutrophil cytoplasmic autoantibodies specific for anti-proteinase 3 and anti-myeloperoxidase

Anti-neutrophil cytoplasmic autoantibodies (ANCA) occur in a subset of patients with systemic small vessel vasculitis, including patients with Wegener's granulomatosis, microscopic polyangiitis (microscopic polyarteritis), and Churg-Strauss syndrome. Pulmonary disease appears at some time during the course in many patients with ANCA-associated vasculitis. The histologic features of 25 open lung biopsies and two autopsy cases were studied from 27 patients with ANCA. Patients' ages ranged from 8 to 79 years with a mean of 52.6 years. There were 12 females and 15 males. Autoantibodies were characterized as C-ANCA in 13 patients and as P-ANCA in 14 patients. Anti-proteinase 3 antibodies were documented in 12 of 13 patients with C-ANCA. Anti-myeloperoxidase antibodies were documented in all 14 patients with P-ANCA. Vascular lesions were present in 21 patients (78%) and 11 patients (41%) had bronchial lesions. Capillaritis was the most common vascular lesion (17 patients, 63%), and was found with similar frequency in patients with C-ANCA and those with P-ANCA. Extravascular structures were a common site of tissue injury. Airway lesions including bronchiolitis obliterans organizing pneumonia (4 patients, 19%), necrotizing granulomatous inflammation (4 patients, 15%), and non-granulomatous inflammation (3 patients, 11%) were more commonly associated with patients with C-ANCA. Interstitial lesions were found in 20 patients (74%), and included necrotizing granulomatous inflammation (8 patients, 30%), fibrosis (13 patients, 48%), and chronic inflammation (12 patients, 44%). No histologic lesion were found that were specific for C-ANCA or P-ANCA. This series demonstrates the wide variety of pulmonary lesions found in patients with ANCA-associated pulmonary disease, and shows that extravascular structures are a common site of injury in ANCA-associated vasculitis.

A review of therapeutic studies of idiopathic membranous glomerulopathy

The treatment of idiopathic membranous glomerulopathy remains an enigma. We have reviewed many of the important clinical trials concerning membranous glomerulopathy using a meta-analysis and a secondary pooled analysis to test the effects of corticosteroid or alkylating, therapy compared with no treatment on renal survival and complete remission of the nephrotic syndrome. A search was performed using MEDLINE (1968 through 1993) for articles on idiopathic membranous glomerulopathy and glomerulonephritis. Bibliographies of articles were reviewed for completeness. Sixty-nine articles were reviewed. Meta-analysis was performed for four trials that evaluated corticosteroids compared with no treatment and for three trials that evaluated alkylating therapy compared with no treatment. Pooled analysis was performed on randomized and prospective studies (10 studies) and then with 22 case series added. All studies evaluated renal biopsy-proven disease. Meta-analysis was performed on the relative chance of being in complete remission for each study. Renal survival could be evaluated by pooled analysis only. For pooled analyses, Cox's proportional hazard and logistic regression models were used to test the effect of therapy on renal survival and the nephrotic syndrome, respectively. Data concerning gender, nephrotic syndrome, and geographic region were used in all statistical models. Evaluation of renal survival revealed no differences by treatment group (P > 0.1). By meta-analysis, the relative chance of complete remission was not improved for corticosteroid-treated patients (1.55; 95% confidence interval, 0.99 to 2.44; P > 0.1), but was improved for patients treated with alkylating agents (4.8; 95% confidence interval, 1.44 to 15.96; P < 0.05) when compared with no treatment. Pooled analysis of randomized and prospective studies, as well pooled analysis with all studies, supported the findings of the meta-analysis. Corticosteroids or alkylating therapy did not improve renal survival in idiopathic membranous glomerulopathy. Complete remission of the nephrotic syndrome was observed more frequently with the use of alkylating agents.

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.

Antimyeloperoxidase antibodies induce neutrophil adherence to cultured human endothelial cells

Antimyeloperoxidase autoantibodies are found in the sera of some patients with glomerulonephritis and systemic vasculitis. Previously, we demonstrated that they were able to stimulate neutrophils to damage cultured human endothelial cells. We now report that antimyeloperoxidase antibodies are able to stimulate neutrophils to adhere to cultured human endothelial cells. Immunoglobulin G purified from myeloperoxidase-antineutrophil cytoplasmic autoantibody positive sera increased adherence to 331 +/- 60% of unstimulated controls. In a similar manner, rabbit antimyeloperoxidase enhanced neutrophil adherence. Stimulating the endothelial cells with 10 micrograms/mL endotoxin enhanced antimyeloperoxidase stimulated adherence. In the presence of a CD18 blocking antibody (MoAb 60.3), antimyeloperoxidase-stimulated adherence was significantly decreased. These results add further understanding to the antimyeloperoxidase-stimulated neutrophil-endothelial cell interaction and further support the hypothesis that antimyeloperoxidase autoantibodies are of pathogenic import in glomerulonephritis and vasculitis.

Immune complex glomerulonephritis is induced in rats immunized with heterologous myeloperoxidase

Anti-neutrophil cytoplasmic antibodies (ANCA), including anti-myeloperoxidase (MPO) antibodies, are associated with pauci-immune necrotizing small vessel vasculitis or glomerulonephritis. In order to substantiate a pathogenic role for ANCA, an animal model of pauci-immune ANCA-induced glomerulonephritis or vasculitis is required. Brouwer et al. reported pauci-immune glomerulonephritis in rats immunized with human MPO followed by perfusion of kidneys with lysosomal enzyme extract combined with H2O2, and suggested that this could serve as a model of ANCA-induced disease. We repeated these studies in spontaneously hypertensive rats (SHR) and Brown Norway rats (BNR). We immunized rats with human MPO. When circulating anti-MPO antibodies were detectable by indirect immunofluorescence microscopy and ELISA, blood pressure was measured, then perfusion of the left kidney of each rat was done via the renal artery in a closed, blood-free circuit with either MPO + H2O2, MPO, H2O2 alone or MPO + H2O2 + neutral protease. Rats were killed on day 4 or day 10 after perfusion, and specimens were examined by light and immunofluorescence microscopy. Pathological lesions and deposits of IgG, C3, and MPO were found in immunized rats perfused with MPO + H2O2 with or without neutral protease, or MPO alone, in both rat strains and on both day 4 and day 10. The degree of histologic injury was proportional in intensity to the amount of IgG immune deposits. Spontaneously hypertensive rats sustained more damage and higher blood pressure than Brown Norway rats. No lesion was observed in immunized rats perfused with H2O2 or in the non-perfused right kidneys. Some of the non-immunized rats perfused with MPO + H2O2 developed pathological lesions. In conclusion, these rat models are examples of immune complex-mediated glomerulonephritis, and therefore are not similar to human ANCA-associated disease.

Luteal phase hyperprolactinemia

OBJECTIVE

To determine the incidence of both isolated and repetitive prolactin elevations in the luteal phase of otherwise normoprolactinemic women. To see if sporadic luteal-phase hyperprolactinemia is associated with progesterone deficiency, and to explore a possible physiological basis for sporadic hyperprolactinemia by TRH challenge.

SETTING

Hospital-based reproductive endocrinology/infertility service.

DESIGN

Prospective measurement of luteal phase serum progesterone and prolactin in normoprolactinemic ovulatory women. TRH stimulation testing in volunteers with repetitive luteal phase hyperprolactinemia and normoprolactinemic controls.

PATIENTS

133 sequentially selected infertile, ovulatory women with normal prolactin levels in the proliferative phase of the cycle.

INTERVENTIONS

Measurement of serum progesterone and prolactin during the luteal phase, based on the day of the LH surge. TRH testing in the midluteal phase of the cycle in patients with two or more luteal phase prolactin elevations, and in five normoprolactinemic volunteers in both the preovulatory and midluteal phase.

RESULTS

Of 133 subjects, 85 (64%) had no prolactin level exceeding 20 ng/mL in the luteal phase. Thirty-three (25%) had two or more elevated levels, and were considered to have repetitive luteal phase hyperprolactinemia (LPH). TRH testing in control subjects resulted in a greater prolactin response in the preovulatory phase. The group with LPH demonstrated an initial elevation of prolactin greater than that of the normoprolactinemic controls, but a subsequent drop to levels lower than both preovulatory and midluteal normoprolactinemic controls by 45 minutes.

CONCLUSIONS

Sporadic luteal-phase hyperprolactinemia is a relatively common event (36% of 133 subjects in the present series). Of these 48 women, 33 (69%) had repetitive elevations, suggesting the elevation in these subjects to be more than a random event. The physiological validity of this observation is further demonstrated by an abnormal response to TRH stimulation, but the normal levels of luteal phase progesterone leave questions as to its pathological importance.

Vasculitis affecting the skin. A review

Although cutaneous purpura and nodules are important clinical manifestations of vasculitis, many other cutaneous expressions of injury also can be caused by vasculitis. Once cutaneous vasculitis is recognized, patient evaluation should center on identifying causative agents, pathogenic mechanisms and extracutaneous organ system involvement, and diagnostic categorization of the disease. Once identified, some causative agents, such as an infectious pathogen, drug, or neoplasm, can be eliminated leading to resolution of the vasculitis. Recognition of the pathogenic category, such as immune complex-mediated vasculitis or ANCA-associated vasculitis, will narrow the differential diagnosis and suggest the likelihood and pattern of extracutaneous disease. Accurate diagnostic categorization, which will direct prognostication and treatment, usually requires integration of clinical, pathologic, and serologic data.

The pathology of vasculitis involving the kidney

The kidneys are frequently affected by systemic vasculitides. This is not surprising given the numerous vessels within the renal parenchyma. The kidneys are most often involved by small vessel vasculitides, such as microscopic polyangiitis (microscopic polyarteritis), Wegener's granulomatosis, Henoch-Schönlein purpura, and cryoglobulinemic vasculitis. These vasculitides cause renal dysfunction predominantly by inducing glomerular inflammation with resultant nephritis and renal failure. Microscopic polyangiitis (microscopic polyarteritis) and Wegener's granulomatosis are associated with and may be caused by antineutrophil cytoplasmic autoantibodies. Henoch-Schönlein purpura is caused by immunoglobulin (Ig) A-dominant immune complex localization in small vessels. Cryoglobulinemic vasculitis is sometimes induced by hepatitis C infection. Necrotizing medium-sized vessel vasculitides, such as classic polyarteritis nodosa and Kawasaki's disease, are less frequent causes of renal disease. They cause infarction secondary to thrombosis of inflamed major extrarenal and intrarenal arteries, and may lead to life-threatening hemorrhage from rupture of aneurysms. Large vessel vasculitides, such as giant cell (temporal) arteritis and Takayasu arteritis, only rarely injure the kidneys, usually by ischemia secondary to vasculitic involvement of the renal arteries or abdominal aorta. This ischemia can cause renovascular hypertension.

Antineutrophil cytoplasmic autoantibody-positive crescentic glomerulonephritis as a complication of treatment with propylthiouracil in children

Propylthiouracil, which is commonly used in the treatment of hyperthyroidism, has been associated in adults with antineutrophil cytoplasmic autoantibody, a serologic marker of vasculitis. Severe renal disease has not been reported as a complication of therapy with this drug. We report severe antineutrophil cytoplasmic autoantibody-positive vasculitis in children receiving propylthiouracil, as well as rapidly progressive crescentic glomerulonephritis after administration of this drug.

Collapsing glomerulopathy: a clinically and pathologically distinct variant of focal segmental glomerulosclerosis

Sixteen patients with renal biopsy findings of extensive focal glomerular capillary collapse, visceral epithelial cell hypertrophy and hyperplasia, and variable degrees of tubulointerstitial injury in the absence of evidence for human immunodeficiency virus (HIV) infection or intravenous drug abuse were prospectively identified by renal biopsy. The pathologic process was designated collapsing glomerulopathy to distinguish it from other patterns of focal glomerular sclerosis. The clinical and pathologic characteristics of these 16 patients were analyzed and compared to a group of 25 patients with noncollapsing focal segmental glomerulosclerosis (FSGS). Thirteen of 16 patients with collapsing glomerulopathy were black as compared with 11 of 25 with FSGS (P = 0.018). The most common findings at presentation were hypertension and manifestations of the nephrotic syndrome. Although the duration of symptoms prior to presentation was no longer in the collapsing glomerulopathy group, the presenting mean serum creatinine was higher in patients with collapsing glomerulopathy than in those with noncollapsing FSGS (3.5 +/- 3.4 mg/dl vs. 1.3 0.6 mg/dl, P = 0.001). Twenty-four-hour urine protein excretion was also higher in the collapsing glomerulopathy group (13.2 +/- 7.7 g/day vs. 4.6 +/- 4.5 g/day FSGS, P = 0.005). The collapsing glomerulopathy patients had a mean age of 41.4 +/- 19.1 (range 19 to 81), a male-to-female ratio of 11:5 and a black-to-white ratio of 13:3. Renal survival, evaluated by life-table analysis, was markedly worse in collapsing glomerulopathy patients than in FSGS patients (P = 0.0004). It is proposed that collapsing glomerulopathy is a distinct entity characterized by black racial predominance, massive proteinuria, relatively rapidly progressive renal insufficiency, and distinctive pathologic findings.(ABSTRACT TRUNCATED AT 250 WORDS)

Nomenclature of systemic vasculitides. Proposal of an international consensus conference

The following are some of the conclusions and proposals made at the Chapel Hill Consensus Conference on the Nomenclature of Systemic Vasculitis. 1. Although not a prerequisite component of the definitions, patient age is recognized as a useful discriminator between Takayasu arteritis and giant cell (temporal) arteritis. 2. The name "polyarteritis nodosa," or alternatively, the name "classic polyarteritis nodosa," is restricted to disease in which there is arteritis in medium-sized and small arteries without involvement of smaller vessels. Therefore, patients with vasculitis affecting arterioles, venules, or capillaries, including glomerular capillaries (i.e., with glomerulonephritis), are excluded from this diagnostic category. 3. The name "Wegener's granulomatosis" is restricted to patients with granulomatous inflammation. Patients with exclusively nongranulomatous small vessel vasculitis involving the upper or lower respiratory tract (e.g., alveolar capillaritis) fall into the category of microscopic polyangiitis (microscopic polyarteritis). 4. The term "hypersensitivity vasculitis" is not used. Most patients who would have been given this diagnosis fall into the category of microscopic polyangiitis (microscopic polyarteritis) or cutaneous leukocytoclastic angiitis. 5. The name "microscopic polyangiitis," or alternatively, "microscopic polyarteritis," connotes pauci-immune (i.e., few or no immune deposits) necrotizing vasculitis affecting small vessels, with or without involvement of medium-sized arteries. Cryoglobulinemic vasculitis, Henoch-Schönlein purpura, and other forms of immune complex-mediated small vessel vasculitis must be ruled out to make this diagnosis. 6. The name "cutaneous leukocytoclastic angiitis" is restricted to vasculitis in the skin without involvement of vessels in any other organ. 7. Mucocutaneous lymph node syndrome must be present to make a diagnosis of Kawasaki disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunoglobulin A-fibronectin aggregate levels in children and adults with immunoglobulin A nephropathy

Immunoglobulin A-fibronectin aggregates (IgAFNs) may be demonstrable in the serum of patients with IgA nephropathy. Initial reports suggested that IgAFN could be a marker for IgA nephropathy with clinical utility in differentiating IgA nephropathy from non-IgA glomerulonephritis. Serum IgAFN concentration was determined in 105 samples from 52 patients with IgA nephropathy who were followed in Kentucky or Tennessee. On at least one occasion, IgAFN was positive (significantly elevated) for 25 of the 52 patients (48%). Thirty-eight percent of the 105 samples were positive. Pediatric and adult patients had a similar incidence of positive IgAFN. A small but nonsignificant increase in the incidence of positive IgAFN was shown for patients who had or subsequently developed chronic renal insufficiency. Weak but significant correlations were found between IgAFN concentration and serum IgA concentration and C3 activation. In the present study, IgAFN concentration was significantly higher for the patients with IgA nephropathy as compared with the patients with non-IgA glomerulonephritis from our previous study. While IgAFN may be clinically useful in differentiating IgA nephropathy from non-IgA nephropathy, the present assay cannot be used to diagnose IgA nephropathy.

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.

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.

The clinical, serologic, and immunopathologic heterogeneity of cutaneous leukocytoclastic angiitis

Histologically identical cutaneous leukocytoclastic angiitis occurs in patients with different serologic markers for vasculitis. When categorized on the basis of serologic analysis for antineutrophil cytoplasmic autoantibodies and IgA fibronectin aggregates, categories of leukocytoclastic angiitis have many overlapping features; however, there are distinctive clinical and immunopathologic trends among the categories. When both serologic tests are negative, there is a low probability that systemic vasculitis is present. The presence of either serologic marker indicates a strong probability for the presence of extracutaneous vasculitis and/or glomerulonephritis.

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.