Diagnostic usefulness of antineutrophil cytoplasmic autoantibody serology. Comparative evaluation of commercial indirect fluorescent antibody kits and enzyme immunoassay kits.

Antineutrophil cytoplasmic autoantibodies (ANCAs) are increasingly used as serologic markers for pauci-immune crescentic glomerulonephritis and small vessel vasculitis. Many hospital laboratories and referral laboratories use commercial assay kits to detect ANCAs, despite inadequate documentation in the medical literature of kit performance. We evaluated the diagnostic sensitivity, specificity, and predictive value of 3 commercial indirect immunofluorescence assay (IFA) kits and 7 commercial enzyme immunoassay (EIA) kits for several ANCA subtypes. Serum samples from 396 patients with a variety of renal diseases were analyzed, including 146 patients with pauci-immune crescentic glomerulo-nephritis with or without systemic vasculitis. With 1 exception, the kits had more than 90% agreement with the reference standard and gave results similar to those of research laboratories. IFA diagnostic sensitivity ranged from 81% to 91% and EIA sensitivity from 75% to 84%. Maximum specificity was obtained with combined IFA and EIA. Diagnostic specificity was more than 70% for 2 of 3 IFA kits and at least 90% for 5 of 7 EIA kits. Predictive values varied with clinical manifestations. Most commercial IFA and EIA kits that were evaluated provide acceptably accurate analytic results.

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).

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.

Anti-neutrophil cytoplasmic autoantibody-associated glomerulonephritis and vasculitis.

Anti-neutrophil cytoplasmic autoantibodies (ANCA) react with constituents of neutrophil primary granules and monocyte lysosomes. Indirect immunofluorescence microscopy using alcohol-fixed neutrophils demonstrates two ANCA types: one causing cytoplasmic staining (C-ANCA), and a second causing artifactual perinuclear staining (P-ANCA) that frequently has specificity for myeloperoxidase. Using indirect immunofluorescence microscopy (IIFM) and enzyme immunoassays (EIA), sera from over 300 patients with renal disease, with and without systemic vasculitis, were analyzed. Of 76 patients with pauci-immune glomerulonephritis with crescents or necrosis, 87% had ANCA by IIFM (38% of C-ANCA type, 49% of P-ANCA type), and 78% had ANCA by EIA. Of 55 patients with nonlupus immune complex-mediated glomerulonephritis, only 11% had ANCA by IIFM and 5% had ANCA by EIA. Of 24 patients with anti-GBM antibody-mediated glomerulonephritis, none had ANCA. Renal and extrarenal lesions were studied in 81 patients with ANCA-associated glomerulonephritis. These patients formed a pathologic continuum ranging from renal-limited to widespread systemic vascular injury, including patients with primary crescentic glomerulonephritis, Wegener's granulomatosis, and polyarteritis nodosa. In ANCA-positive patients the frequency of C-ANCA and P-ANCA correlated with disease distribution. P-ANCA was most frequent with renal-limited disease and C-ANCA was most frequent when there was lung and sinus involvement. It is proposed that ANCA are not only useful diagnostic markers, but may also be directly involved in a novel pathogenetic mechanism that is a frequent cause of crescentic glomerulonephritis and systemic necrotizing vasculitis.

Low incidence of IgA nephropathy in blacks.

The clinical and pathologic features were evaluated in 106 IgA nephropathy patients identified in 1,753 consecutive patients undergoing renal biopsy in the southeastern United States. Special attention was paid to the proportion of Blacks among the IgA nephropathy patients compared with non-IgA nephropathy patients, and any differences in clinical or pathologic findings between Whites and Blacks with IgA nephropathy. The incidence of IgA nephropathy was approximately six times lower in Blacks (6 out of 461) than in Whites (100 out of 1,292) undergoing renal biopsy (P less than 0.001). There were no morphologic or immunohistopathologic differences between Whites and Blacks with IgA nephropathy. The only clinical difference was a marked shift in the male to female sex ratio from 3.5:1 in Whites to 1:5 in Blacks (P less than 0.004). The low incidence and reversed sex ratio of IgA nephropathy in Blacks were also supported by a review of previously published data.

Concurrent antiglomerular basement membrane antibody and immune complex mediated glomerulonephritis.

A teenage male, with Goodpasture's syndrome and serum antiglomerular basement membrane (anti-GBM) antibodies, had a focal proliferative glomerulonephritis with crescents. Immunofluorescence microscopy of his glomeruli using anti-IgG antibodies demonstrated both intense linear GBM staining, and granular subepithelial staining. Electron microscopy revealed numerous subepithelial electron-dense deposits. Identical IgG subclass restriction (dominance of IgG1 and IgG4) of both types of glomerular deposits in this patient supports, but does not prove, a postulate that the linear staining was due to anti-GBM antibodies bound to intact GBM, and that the granular staining was due to anti-GBM antibodies complexed with freed GBM antigens.

Diffuse T-cell lymphoma preceded by nodular lymphoma.

A patient with a nodular lymphoma morphologically indistinguishable from follicular B-cell lymphoma subsequently developed a diffuse T-cell lymphoma. This T-cell lymphoma displayed characteristics analogous to mature T-lymphocytes, and typed as a suppressor/cytotoxic T-cell with the monoclonal antibodies. The light and electron microscopy morphology of the T-cell lymphoma was similar to that reported for node-based T-cell lymphomas. There was a polymorphous proliferation of variably transformed lymphocytes including immunoblasts. This case could represent either a nodular form of T-cell lymphoma converting to a diffuse T-cell lymphoma, or a follicular B-cell lymphoma preceding, and possibly inducing, a suppressor T-cell lymphoma.

Insulin receptor autoantibody-induced pancreatic islet beta (B) cell hyperplasia.

A patient with progressive systemic sclerosis (scleroderma) and anti-insulin receptor autoantibody-induced diabetes mellitus was found to have pancreatic islet beta (B) cell hyperplasia by computerized morphometry and immunohistochemistry. Unlike most previously reported cases of islet cell hyperplasia, where the islet cell hyperactivity produced disturbed glucose metabolism (hypoglycemia, this case illustrates compensatory islet cell hyperplasia in response to a perturbation in glucose metabolism by insulin-receptor blockade with resultant hyperglycemia.

Interstrain variations in nephritogenicity of heterologous protein in mice.

Swiss albino, BALB/c, and eight substrains of C3H mice were given daily intraperitoneal injections of horse apoferritin (HAF) for up to 56 days. At varying intervals, renal tissue was examined by light, immunofluorescence, and electron microscopy. Swiss mice developed proliferative glomerulonephritis after 7 to 14 days of HAF, and 45 per cent progressed to severe crescentic glomerulonephritis after from 21 to 56 days of HAF. In Swiss mice, glomerular immune deposits evolved from predominantly IgM mesangial deposits at 7 days to mesangial IgG at 14 days to capillary wall IgG after 21 or more days of HAF injections. BALB/c mice given identical HAF doses never developed severe crescentic glomerulonephritis but rather an extensive global necrotizing glomerulonephritis most prevalent after from 9 to 18 days of HAF. The distinct evolution of glomerular immune deposits observed in Swiss mice was less clear-cut in BALB/c mice, with greater persistence of mesangial deposits and IgM over time. Only 11 per cent of C3H mice (confined to two substrains) developed glomerular lesions by light microscopy after 2 to 3 weeks of HAF administration. No C3H/HeN mice developed glomerulonephritis even after up to 47 days of HAF injection. From 7 days on, 45 per cent of HAF-injected C3H mice had low level IgM mesangial immune deposits but did not manifest the evolution from mesangial to capillary deposition observed in BALB/c and Swiss albino mice. F1 hybrid and congenic mice carrying BALB/c H-2 genetic information developed glomerular lesions similar to those produced in BALB/c mice. These data (1) indicate an interrelated morphologic and immunohistologic evolution of heterologous protein induced glomerular lesions in mice, (2) demonstrate morphologic and immunohistologic differences in glomerular lesions development between genetically disparate mouse strains given identical antigen exposures, and (3) support the genetic control of heterologous protein-induced glomerulonephritis and suggest a role for the major histocompatibility region in this genetic regulation.

IgD myeloma with intracytoplasmic crystalline inclusions.

Plasma cells from an IgD myeloma contained intracytoplasmic crystals. By electron microscopy, these crystals had 13-nm periodicity and were contained within vacuoles formed of smooth membranes. Immunofluorescence microscopy of the neoplastic plasma cells demonstrated diffuse cytoplasmic staining with accentuated Golgi region staining specific for immunoglobulin delta heavy and lambda light chains. The observations support an association between the crystal-containing vacuoles and the Golgi apparatus. Previously reported plasma cell and lymphocyte crystalline inclusions are reviewed, and compared with the crystals described in this report.