Immunologic and clinical observations of granulocyte-specific antinuclear antibodies

Hypovitaminosis A Drives the Progression of Tubulointerstitial Lupus Nephritis through Potentiating Predisease Cellular Autoreactivity

Vitamin A (VA) deficiency (VAD) is observed in both humans and mice with lupus nephritis. However, whether VAD is a driving factor for accelerated progression of lupus nephritis is unclear. In this study, we investigated the effect of VAD on the progression of lupus nephritis in a lupus-prone mouse model, MRL/lpr. We initiated VAD either during gestation or after weaning to reveal a potential time-dependent effect. We found exacerbated lupus nephritis at ∼15 wk of age with both types of VAD that provoked tubulointerstitial nephritis leading to renal failure. This was concomitant with significantly higher mortality in all VAD mice. Importantly, restoration of VA levels after weaning reversed VAD-induced mortality. These results suggest VAD-driven acceleration of tubulointerstitial lupus nephritis. Mechanistically, at the earlier time point of 7 wk of age and before the onset of clinical lupus nephritis, continued VAD (from gestation until postweaning) enhanced plasma cell activation and augmented their autoantibody production, while also increasing the expansion of T lymphocytes that could promote plasma cell autoreactivity. Moreover, continued VAD increased the renal infiltration of plasmacytoid dendritic cells. VAD initiated after weaning, in contrast, showed modest effects on autoantibodies and renal plasmacytoid dendritic cells that were not statistically significant. Remarkably, analysis of gene expression in human kidney revealed that the retinoic acid pathway was decreased in the tubulointerstitial region of lupus nephritis, supporting our findings in MRL/lpr mice. Future studies will elucidate the underlying mechanisms of how VAD modulates cellular functions to exacerbate tubulointerstitial lupus nephritis.

Antineutrophil cytoplasmic antibodies in rheumatoid arthritis. Characterization and clinical correlations

OBJECTIVE

To study the prevalence, interrelationships, and target antigens of antineutrophil cytoplasmic antibodies (ANCA) in rheumatoid arthritis (RA) and to relate their presence to disease duration and to the occurrence of extraarticular manifestations, including vasculitis.

METHODS

Sera from 94 patients with RA (31 with recent-onset disease, 35 with longstanding disease but without extraarticular manifestations, and 28 with extraarticular disease) were studied for the presence of ANCA by indirect immunofluorescence. All sera were tested by enzyme-linked immunosorbent assay (ELISA) for the presence of antibodies to proteinase 3, myeloperoxidase (MPO), elastase, lactoferrin (LF), and cathepsin G (CG), and by Western blotting for antibodies to neutrophil proteins.

RESULTS

Seventy percent of the 94 sera showed staining of the nuclei of ethanol-fixed neutrophils; 32% of the 94 were proven to have ANCA, as manifested by their cytoplasmic staining pattern on paraformaldehyde-fixed neutrophils. In the ELISA, 19 sera reacted with LF, 1 with MPO, and 1 with CG. By Western blotting, 21 sera reacted with LF, and 15 reacted with previously unknown polypeptides (7 sera with a 67/66-kd doublet and 8 with a 63/54-kd doublet). Neither of these antibodies was associated with a particular subset of the disease, but the prevalence of the antibodies tended to increase among patients with longstanding disease.

CONCLUSION

ANCA in RA patients are directed toward diverse cytoplasmic antigens of the neutrophil, in particular, LF and other, not yet fully characterized polypeptides. The antibodies are not a marker for a disease subset, but are probably a corollary of chronic inflammation.

Antineutrophil cytoplasmic antibodies: a still-growing class of autoantibodies in inflammatory disorders

Antineutrophil cytoplasmic antibodies (ANCA) have been described as sensitive and specific markers for active Wegener's granulomatosis (WG). ANCA in WG produce a characteristic cytoplasmic staining pattern of neutrophils (c-ANCA) and are directed against proteinase 3 (Pr3), a serine protease from the azurophilic granules. c-ANCA, more or less equivalent to anti-Pr3, occur in more than 90% of patients with extended WG, in 75% of patients with limited WG without renal involvement, and in some 40% to 50% of patients with vasculitic overlap syndromes suggestive of WG such as microscopic polyarteritis. The presence of c-ANCA is highly specific for those diseases (greater than 98%). Changes of levels of c-ANCA precede disease activity and may be used as guidelines for treatment. Antibodies producing a perinuclear staining of ethanol-fixed neutrophils (p-ANCA) occur in a wide range of diseases. They are directed against different cytoplasmic constituents of neutrophils. Among those, antibodies to myeloperoxidase are found in patients with idiopathic crescentic glomerulonephritis, the Churg-Strauss syndrome, polyarteritis nodosa with visceral involvement, and vasculitic overlap syndromes. Their specificity for this group of necrotizing vasculitides is high (94% to 99%), although they may occur in patients with hydralazine-induced glomerulonephritis, anti-glomerular basement membrane disease, and possibly in some patients with idiopathic systemic lupus erythematosus. Antibodies to leukocyte elastase are incidentally found in patients with vasculitic disorders, whereas lactoferrin antibodies are detected in patients with primary sclerosing cholangitis with or without ulcerative colitis and in rheumatoid arthritis. Their diagnostic significance awaits further studies. p-ANCA of undefined specificity may distinguish ulcerative colitis (sensitivity of 75%) from Crohn's disease (sensitivity of 20%). p-ANCA also occur in autoimmune liver diseases: in 75% of patients with chronic active hepatitis, in 60% to 85% of those with primary sclerosing cholangitis, and in about 30% of patients with primary biliary cirrhosis. Finally, p-ANCA are detected in chronic arthritides and in some 5% of healthy controls. Assessment of their diagnostic value has to await further characterization of the antigens involved, allowing the development of antigen-specific assays.

Substrate specificity of antinuclear antibodies in scleroderma

Studies of antinuclear antibodies (ANA) were carried out in 39 cases of systemic scleroderma and for comparison in 19 cases of systemic lupus erythematosus (SLE) and 4 of mixed connective tissue disease (MCTD) using indirect immunofluorescence (IF) methods under standard conditions. The results on three different substrates--monkey esophagus, guineapig lip and rat liver--are reported. In 48.7% of scleroderma cases ANA showed a substrate specificity. The highest percentage of positive results in scleroderma was obtained on monkey esophagus (97.4%) and the lowest on rat liver (61.5%). In SLE and MCTD, in contrast, only about 13% of the sera displayed such specificity. If only sera with substrate specificity are considered, the positive results on monkey esophagus and rat liver are 94.7% and 21.1%, respectively. Titers of sera reacting positively on 2 or 3 substrates were mostly in agreement, although some sera both in systemic scleroderma and SLE showed higher titers on monkey esophagus. The IF pattern was usually the same regardless of the substrate, Tests for ANA in scleroderma should be performed on at least 2 substrates simultaneously.

Serum antibody in rheumatoid arthritis reactive with a cell-associated antigen. Demonstration by precipitation and immunofluorescence

A cell-free extract of human diploid B lymphocytes (Wil2) in continuous culture was used as the source of antigen in immunodiffusion to detect a precipitating antibody referred to as rheumatoid arthritis precipitin (RAP) in sera of patients with rheumatoid arthritis (RA). The prevalence of RAP was determined in various arthritides and other connective tissue diseases. It was found in 67% of patients with seropositive RA and in 62% of patients with Sjögren's syndrome associated with RA. But its frequency was lower in many other connective tissue diseases, including seronegative RA and Sjögren's syndrome without associated RA. Matching sera and synovial fluids from patients with seropositive RA were also studied. Differences in serum and synovial fluid RAP titers were demonstrated, but generally when RAP was present in serum, it was also present in synovial fluid and vice versa. Indirect immunofluorescence (IF) with Wil2 cells as substrate was used to demonstrate RAP and to determine morphologically the nature of the reactive cellular antigen. When cells were treated with commonly used fixatives, little or no staining with RAP positive sera was observed. This outcome was shown to be the result of the extreme solubility of the cellular antigen reactive with RAP. The antigen was retained best in a reactive form in Wil2 cells after fixation of cells with dry heat at 37 degrees C for 30 minutes, and it was demonstrated by IF staining as small round granules distributed in the nucleus and cytoplasm. IF was also employed to demonstrate that RAP is immunoglobulin belonging to IgG and IgM classes and not to IgA or IgD.

Diagnosis of lupus erythematosus and rheumatoid arthritis in children

Laboratory tests are of importance in differentiating lupus erythematosus from rheumatoid arthritis, and in distinguishing between the two forms of lupus, because an accurate understanding of the nature of the disease determines rational therapy.