Antonella Radice

International recommendations for the assessment of autoantibodies to cellular antigens referred to as anti-nuclear antibodies

Anti-nuclear antibodies (ANA) are fundamental for the diagnosis of autoimmune diseases, and have been determined by indirect immunofluorescence assay (IIFA) for decades. As the demand for ANA testing increased, alternative techniques were developed challenging the classic IIFA. These alternative platforms differ in their antigen profiles, sensitivity and specificity, raising uncertainties regarding standardisation and interpretation of incongruent results. Therefore, an international group of experts has created recommendations for ANA testing by different methods. Two groups of experts participated in this initiative. The European autoimmunity standardization initiative representing 15 European countries and the International Union of Immunologic Societies/World Health Organization/Arthritis Foundation/Centers for Disease Control and Prevention autoantibody standardising committee. A three-step process followed by a Delphi exercise with closed voting was applied. Twenty-five recommendations for determining ANA (1–13), anti-double stranded DNA antibodies (14–18), specific antibodies (19–23) and validation of methods (24–25) were created. Significant differences between experts were observed regarding recommendations 24–25 (p<0.03). Here, we formulated recommendations for the assessment and interpretation of ANA and associated antibodies. Notably, the roles of IIFA as a reference method, and the importance of defining nuclear and cytoplasmic staining, were emphasised, while the need to incorporate alternative automated methods was acknowledged. Various approaches to overcome discrepancies between methods were suggested of which an improved bench-to-bedside communication is of the utmost importance. These recommendations are based on current knowledge and can enable harmonisation of local algorithms for testing and evaluation of ANA and related autoantibodies. Last but not least, new more appropriate terminologies have been suggested.

Anti-endothelial cell antibodies in patients with Wegener's granulomatosis and micropolyarteritis.

Anti‐endothelial cell antibodies (AECA) have been detected by cell surface radioimmunoassay innine out of 15 patients with micropolyarteritis (MPA) and in two out of five patients with Wegenersgranulomatosis. AECA mostly belonged to the IgG isotype and were present in the active phase ofthe diseases. These antibodies were not detectable in 10 sera from patients with essential mixedcryoglobulinaemia. suggesting that they were not a mere epiphenomenon consequent to theinflammatory vascular injury. The binding activity was not related to ABH antigens or to HLA class Iantigens displayed by resting human endothelial cells in culture and was not influenced by removingimmune complexes. Absorption of the anti‐neutrophil cytoplasmic antibodies (ANCA). present inMPA and Wegeners granulomatosis sera, did not affect the endothelial binding. AECA‐positive seradid not display lytic activity against endothelial cells, neither alone nor after addition of freshcomplement or normal human peripheral blood mononuelear cells. Although AECA arc notcytolytic for endothelial cell monolayers in vitro, the reactivity against intact endothelial cells suggeststheir possible involvement in in vivo pathological processes affecting vascular structures in smallvessel primary vasculitides.

Are laboratory tests useful for monitoring the activity of lupus nephritis? A 6-year prospective study in a cohort of 228 patients with lupus nephritis

Objectives: To evaluate the role of immunological tests for monitoring lupus nephritis (LN) activity. Methods: C3, C4, anti-dsDNA and anti-C1q antibodies were prospectively performed over 6 years in 228 patients with LN. Results: In membranous LN only anti-C1q antibodies differentiated proteinuric flares from quiescent disease (p = 0.02). However, in this group 46% of flares occurred with a normal value of anti-C1q antibodies versus 20% in proliferative LN (p = 0.02). In patients with antiphospholipid antibodies (APL), 33% of flares occurred with normal levels of anti-C1q antibodies versus 14.5% in patients that were APL-negative (p = 0.02). In proliferative LN, anti-C1q antibodies showed a slightly better sensitivity and specificity (80.5 and 71% respectively) than other tests for the diagnosis of renal flares. All four tests had good negative predictive value (NPV). At univariate analysis anti-C1q was the best renal flare predictor (p<0.0005). At multivariate analysis, the association of anti-C1q with C3 and C4 provided the best performance (p<0.0005, p<0.005, p<0.005 respectively). Conclusions: Anti-C1q is slightly better than the other tests to confirm the clinical activity of LN, particularly in patients with proliferative LN and in the absence of APL. All four “specific” tests had a good NPV, suggesting that, in the presence of normal values of each, active LN is unlikely.

Coexistence of Different Circulating Anti-Podocyte Antibodies in Membranous Nephropathy

BACKGROUND AND OBJECTIVES The discovery of different podocyte autoantibodies in membranous nephropathy (MN) raises questions about their pathogenetic and clinical meaning. This study sought to define antibody isotypes and correlations; to compare levels in MN, other glomerulonephritides, and controls; and to determine their association with clinical outcomes. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Serum IgG(1), IgG(3), and IgG(4) against aldose reductase (AR), SOD2, and α-enolase (αENO) were measured at diagnosis in 186 consecutive MN patients, in 96 proteinuric controls (36 with FSGS, and 60 with IgA nephropathy), and in 92 healthy people recruited in four Italian nephrology units. Anti-phospholipase A2 receptor (PLA2r) and anti-neutral endopeptidase (NEP) IgG(4) were titrated in the same specimens. Association with 1-year follow-up clinical parameters was studied in 120 patients. RESULTS IgG(4) was the most common isotype for all antibodies; IgG(1) and IgG(3) were nearly negligible. IgG(4) levels were positive in a significant proportion of MN patients (AR, 34%; SOD2, 28%; αENO, 43%). Antibody titers were higher in MN than in healthy and pathologic controls (P<0.005). Anti-NEP IgG(4) did not differ from normal controls (P=0.12). Anti-PLA2r IgG(4) was detected in 60% of patients and correlated with anti-AR, anti-SOD2, and anti-αENO IgG(4) (P<0.001). In MN patients negative for the whole antibody panel (20%), 1-year proteinuria was lower compared with patients with at least one antibody positivity (P<0.05). CONCLUSIONS Our data suggest that IgG(4) is the prevalent isotype for antibodies against cytoplasmic antigens of podocytes (AR, SOD2, αENO). Their levels were higher than in other proteinuric glomerulonephritides and in normal controls and were correlated with anti-PLA2r. Only baseline negativity for all known antibodies predicted lower 1-year proteinuria.

Anti-DNA antibodies: a diagnostic and prognostic tool for systemic lupus erythematosus?

The clinical impact of anti-DNA antibodies lies on their diagnostic power for systemic lupus erythematosus (SLE), being a formal classification criterion. In spite of such a disease association, low-avidity anti-DNA antibodies might also be part of the natural autoantibody repertoire. Their switch to pathogenic high-avidity autoantibodies is the result of the autoimmune process leading to SLE. Anti-DNA antibodies were shown to play a role in SLE pathogenesis and particularly in kidney damage. Accordingly, antibody titres might fluctuate in relation to disease activity, but their prognostic value for flares is still debated. Several methods for anti-DNA detection were described and there is evidence that the assays identify different antibodies with different prognostic value. The results of a multicenter study on four different routine tests for anti-dsDNA antibody detection showed that: (i) Farr assay displays the best diagnostic specificity/sensitivity for SLE, followed by Crithidia luciliae method (CLIFT), (ii) the new generation of solid phase assay (EliA) shows an increased sensibility versus the classical enzyme linked immune assay (ELISA) but a decreased specificity. Antibody titre detected by EliA and Farr assay correlated with disease activity. These findings would suggest that more than one assay should be useful for SLE diagnosis and monitoring.

Antibodies to endothelial cells in primary vasculitides mediate in vitro endothelial cytotoxicity in the presence of normal peripheral blood mononuclear cells

Twenty-eight out of 62 patients with Wegeners granulomatosis and micropolyarteritis display circulating antiendothelial cell antibodies (AECA) detectable by a cell surface radioimmunoassay. These antibodies do not induce an in vitro endothelial damage either alone or in the presence of fresh complement; however, 50% of IgG-AECA positive sera can be cytotoxic in the presence of human normal peripheral blood mononuclear cells (PBM) at high effector/target ratios. The specificity of the PBM-mediated cytotoxicity is supported by the absence of the phenomenon in AECA negative sera, by the disappearance of the lytic effect after absorption of AECA, and by the finding that cellular-mediated cytotoxicity can be reproduced by purified IgG-AECA positive fractions. On the contrary, polymorphonuclear leukocytes or adherent mononuclear cells are not involved in such a cytotoxic activity. AECA seem to be directed against determinants consitutively expressed on the endothelial surface since the activation of endothelial cells by interleukin-1 beta or interferon-gamma affects neither the antibody binding nor their ability to mediate 51Cr release in the presence of PBM. These findings favor the hypothesis for a possible direct pathogenetic role of circulating AECA in the in vivo vascular damage.

Antinucleosome antibodies in primary antiphospholipid syndrome: A hint at systemic autoimmunity?

BACKGROUND Antinucleosome antibodies (anti-NCS) are reported to be highly sensitive and specific for systemic lupus erythematosus (SLE) and to correlate with disease activity. They may appear in early stages of the disease, in particular before anti-dsDNA antibodies, being a potential marker for identifying patients susceptible to SLE. Patients with primary antiphospholipid syndrome (PAPS) may develop full-blown SLE but there is no evidence for markers predictive for that. AIM To evaluate whether anti-NCS may be predictors for full-blown or lupus like disease (LL) in a cohort of PAPS patients. METHODS A multicentric cohort of 105 PAPS patients was tested for IgG/IgM anti-NCS by using a home made assay with H1-stripped chromatin as antigen. RESULTS Eighty-one out of 105 (77%) of the patients were positive for anti-NCS; medium-high titre results were present only in 49/105 (46%). Anti-NCS were more frequently detected in PAPS+LL, but no relationship with clinical/serological features was found, except for a weak correlation with anti-dsDNA antibodies. Two PAPS patients evolved into full-blown SLE during the follow-up and displayed high titre anti-NCS many years before. CONCLUSIONS Our findings suggest that anti-NCS might be added to the mosaic of autoimmune phenomena characterizing PAPS patients and in particular those with more chance to evolve to SLE.

Renal involvement in anti-neutrophil cytoplasmic autoantibody associated vasculitis

Renal involvement is a common and often severe complication of anti-neutrophil cytoplasmic autoantibody (ANCA) associated vasculitides (AAV). With the exception of Churg-Strauss syndrome (CSS), where kidney involvement is not a prominent feature, renal disease is present in about 70% of patients with Wegeners granulomatosis, now called granulomatosis with polyangiitis (GPA) and in almost 100% of patients with microscopic polyangiitis (MPA). Kidney involvement is generally characterized by a pauci-immune necrotizing and crescentic glomerulonephritis with a very rapid decline of renal function (rapidly progressive glomerulonephritis). Even though there are not qualitative differences in glomerular lesions in patients with GPA or with MPA, chronic damage is significantly higher in MPA (and/or P-ANCA positive patients) than in GPA (and/or C-ANCA positive patients). If untreated necrotizing and crescentic glomerulonephritis has an unfavorable course leading in a few weeks or months to end stage renal disease. Serum creatinine at diagnosis, sclerotic lesions and the number of normal glomeruli at kidney biopsy are the best predictors of renal outcome. Corticosteroids and cyclophosphamide (with the addition of plasma exchange in the most severe cases) are the cornerstone of induction treatment of ANCA-associated renal vasculitis, followed by azathioprine for maintenance. Rituximab is as effective as cyclophosphamide in inducing remission in AAV and probably superior to cyclophosphamide in patients with severe flare, and could be preferred in younger patients in order to preserve fertility and in patients with serious relapses.

Anti‐C1q Autoantibodies in Lupus Nephritis

Anti‐C1q antibodies are found in a variety of diseases, in addition to systemic lupus erythematosus (SLE), and in 3–5% of normal individuals. In particular, anti‐C1q antibodies are detected at a high titer in 100% of patients with hypocomplementemic urticarial vasculitis and in 30–48% of SLE patients. Their titer correlates with active renal disease with a sensitivity of 44–100% and a specificity of 70–92%. An increase in anti‐C1q antibody titer has been suggested to be able to predict renal flares in lupus nephritis so that monitoring anti‐C1q might be valuable for the clinical management of SLE patients as a noninvasive biological marker. Recently our group studied 228 patients affected by lupus nephritis and found that the association of anti‐C1q, C3, and C4, in a multivariate analysis, provided the best prediction of renal flares, particularly in patients with focal and diffuse proliferative lupus nephritis and in the absence of antiphospholipid antibodies.

Glomerular Autoimmune Multicomponents of Human Lupus Nephritis In Vivo: α-Enolase and Annexin AI

Renal targets of autoimmunity in human lupus nephritis (LN) are unknown. We sought to identify autoantibodies and glomerular target antigens in renal biopsy samples from patients with LN and determine whether the same autoantibodies can be detected in circulation. Glomeruli were microdissected from biopsy samples of 20 patients with LN and characterized by proteomic techniques. Serum samples from large cohorts of patients with systemic lupus erythematosus (SLE) with and without LN and other glomerulonephritides were tested. Glomerular IgGs recognized 11 podocyte antigens, with reactivity varying by LN pathology. Notably, IgG2 autoantibodies against α-enolase and annexin AI were detected in 11 and 10 of the biopsy samples, respectively, and predominated over other autoantibodies. Immunohistochemistry revealed colocalization of α-enolase or annexin AI with IgG2 in glomeruli. High levels of serum anti-α-enolase (>15 mg/L) IgG2 and/or anti-annexin AI (>2.7 mg/L) IgG2 were detected in most patients with LN but not patients with other glomerulonephritides, and they identified two cohorts: patients with high anti-α-enolase/low anti-annexin AI IgG2 and patients with low anti-α-enolase/high anti-annexin AI IgG2. Serum levels of both autoantibodies decreased significantly after 12 months of therapy for LN. Anti-α-enolase IgG2 recognized specific epitopes of α-enolase and did not cross-react with dsDNA. Furthermore, nephritogenic monoclonal IgG2 (clone H147) derived from lupus-prone MRL-lpr/lpr mice recognized human α-enolase, suggesting homology between animal models and human LN. These data show a multiantibody composition in LN, where IgG2 autoantibodies against α-enolase and annexin AI predominate in the glomerulus and can be detected in serum.