Myositis-specific autoantibodies in clinical practice: Improving the performance of the immunodot.

BACKGROUND/OBJECTIVES: Idiopathic inflammatory myopathies (IIM) diagnosis and sub-classification can be improved by detection of myositis specific antibodies (MSA) as a first step in diagnosis. However, when using semi-quantitative immunodots for MSA detection, clinical assay performance needs to be improved. METHODS: A retrospective study was done for the "myositis" and "synthetase" immunodots (SRP, NXP2, TIF1gamma, SAE1/2, Mi2, MDA5, Jo1, PL7, PL12, EJ, OJ, KS, ZO and HA) from D-Tek used for 270 patients who had tested positive for MSA in a tertiary laboratory hospital. RESULTS: Results from this analysis revealed: (i) none of the 60 healthy controls presented MSA; (ii) a low assay specificity among patients who tested positive for MSA, 128/270 (47%) were labeled IIM based on the manufacturer's recommended threshold; (iii) in non-IIM patients (53%), the MSA spectrum overlaps predominantly with other autoimmune diseases or idiopathic interstitial lung disease; and (iv) use of a clinical cut-off improves assay specificity for anti-SRP, anti-NXP2, anti-MDA5, anti-Jo1 and anti-PL7 Abs. CONCLUSION: Determining the clinical threshold of the semi-quantitative immunodot assay for MSA is effective for improving its capacity to discriminate IIM from non-IIM and, when IIM diagnosis is excluded, another autoimmune disease or an idiopathic interstitial lung disease should be considered in front of a positive MSA.

Causal risk and protective factors in rheumatoid arthritis: A genetic update.

The characterization of risk and protective factors in complex diseases such as rheumatoid arthritis (RA) has evolved from epidemiological studies, which test association, to the use of Mendelian randomization approaches, which test direct relationships. Indeed, direct associations with the mucosal origin of RA are retrieved with periodontal disease (Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans predominantly), interstitial lung involvement, tobacco smoking and air pollutants. Next, factors directly associated with an acquired immune response include genetic factors (HLA DRB1, PTPN22), capacity to produce anti-modified protein antibodies (AMPA), and relatives with a history of autoimmune diseases. Finally, factors can be also classified according to their direct capacity to interfere with the IL-6/CRP/sIL-IL6R proinflammatory pathway as risk factor (body fat, cardiometabolic factors, type 2 diabetes, depressive syndrome) or either as protective factors by controlling of sIL-6R levels (higher education level, and intelligence). Although some co-founders have been characterized (e.g. vitamin D, physical activity, cancer) the direct association with sex-discrepancy, pregnancy, and infections among other factors remains to be better explored.

[Influence of epigenetic in Sjögren's syndrome]. / Épigénome et syndrome de Gougerot-Sjögren.

Sjögren's syndrome (SS) is a systemic autoimmune epithelitis with a major female incidence, and characterized by a dry syndrome, impaired quality of life, visceral involvement, and lymphoma for the most aggressive cases. During this process, epithelial cells acquire the capacity to produce cytokines, chemokines, and autoantigens which can in turn be presented to the immune system. Consequently, this epithelitis is accompanied by lymphocytic infiltrations leading to the formation of pseudo-follicles in which self-reactive B lymphocytes are present. The recent integration of genomic and especially of epigenomic data, which make it possible to analyze the different cellular partners, opens new perspectives and allows to a better understanding of this complex and still incurable disease.

Epigenetic modifications in salivary glands from patients with Sjögren's syndrome affect cytokeratin 19 expression.

Sjögren's syndrome (SS) is a chronic autoimmune epithelitis, and several lines of experiments indicate that multifactorial factors contribute to salivary gland epithelial cells (SGEC) dysfunctions including a combination of environmental factors, lymphocytic infiltrations, genetic predispositions as well as epigenetic defects. Such statement is reinforced by the observation that global DNA methylation (5MeCyt) is altered in minor salivary glands from pSS patients and that such defect is associated cytokeratin 19 (KRT19) overexpression. An epigenetic deregulation of the KRT19 gene was further tested by treating the human salivary gland (HSG) cell line with the DNA demethylating agent 5-azacytidin, and with the histone acetylase inhibitor trichostatin A. Blocking DNA methylation, but not histone acetylation, with 5-azacytidin was associated with KRT19 overexpression at both transcriptional and protein level. Next, analysis of the CpG genome-wide methylome array in the KTR19 locus from long term cultured SGEC obtained from 8 pSS patients revealed a more reduced DNA methylation level in those patients with defective global DNA methylation. Altogether, our data, therefore, suggest that alteration of DNA methylation in SGEC may contribute to pSS pathophysiology in part by controlling the expression of KRT19.

Defective DNA methylation in salivary gland epithelial acini from patients with Sjögren's syndrome is associated with SSB gene expression, anti-SSB/LA detection, and lymphocyte infiltration.

The pathogenesis of primary Sjögren's syndrome (pSS) is complex, in part due to DNA methylation abnormalities. This study was undertaken to evaluate the importance of global DNA methylation ((5m)C) as determined in minor salivary glands (MSG) from well characterized pSS patients. Twenty-two pSS patients and ten controls were selected, and MSG were stained with anti-(5m)C, anti-(5m)C/anti-cytokeratin (KRT)19, or with anti-SSB/La antibodies (Ab). The DNA methylation status at the SSB gene promoter P1 and P1' was evaluated by methylation-sensitive restriction enzymes (MSRE) coupled with PCR. The effect of the DNA demethylating drug 5 azacytidine (5-Aza) was tested in the human salivary gland (HSG) cell line. In pSS, the reduction of global DNA methylation ((5m)C) was associated with lymphocyte infiltration, the emergence of (5m)C(low) and KRT19(high) acini, and the detection of circulating anti-SSB/La Ab, but not with disease activity (ESSDAI). Next, treating HSG cells with 5-Aza was effective in inducing SSB expression. Finally in pSS patients positive for anti-SSB/La Ab, we further observed DNA demethylation at the SSB gene promoter P1 with consequent SSB overexpression at both the transcriptional and protein levels in salivary gland epithelial cells. In conclusion, our results highlight the importance of DNA methylation in the pathophysiology of pSS and to the emergence of anti-SSB/La Ab.

Anti-α actinin antibodies as new predictors of response to treatment in autoimmune hepatitis type 1.

BACKGROUND: We reported that combined presence of autoantibodies (Abs) against filamentous-actin (AFA) and α-actinin are specific for autoimmune hepatitis type 1 (AIH-1) diagnosis. AIM: To explore our data and assess whether anti-α-actinin and AFA Abs could be used as indicators of response to treatment and predictors of AIH-1 flares in a large cohort of AIH-1 patients. METHODS: Seven hundred and sixty-four serial serum samples of 86 consecutive AIH-1 patients, 509 pathological and 110 normal controls were tested for the presence of anti-α-actinin and AFA Abs by an in-house IgG-specific ELISA and a standardised commercially available ELISA respectively. Patients sera were divided into baseline group (active disease before treatment initiation, n = 86) and then according to treatment response into group A-responders (n = 40 patients), group B-relapsers/incomplete responders (n = 37 patients) and group C-not-treated (n = 9 patients). RESULTS: Anti-α-actinin and AFA levels were significantly higher at baseline. Double reactivity against α-actinin and AFA was associated with disease activity (OR 4.9; 95% CI: 2.7-9). Anti-α-actinin optical densities (ODs) before treatment decreased significantly at first remission (P < 0.05). Treatment response was associated with anti-α-actinin Abs negativity before treatment (OR 3.4; 95% CI: 1.3-8.9) and absence of double positivity for anti-α-actinin and AFA Abs before treatment (OR 3.8; 95% CI: 1.4-10.4). Responders had lower baseline levels of anti-α-actinin than relapsers and/or incomplete responders (P = 0.002). Binary logistic regression revealed lower levels of anti-α-actinin as the only independent predictors of response (P = 0.05). CONCLUSIONS: Anti-α-actinin Abs at baseline appear to predict treatment response and therefore they might be used for monitoring treatment outcome in AIH-1.

Epigenetic alterations and autoimmune disease.

Recent advances in epigenetics have enhanced our knowledge of how environmental factors (UV radiation, drugs, infections, etc.) contribute to the development of autoimmune diseases (AID) in genetically predisposed individuals. Studies conducted in monozygotic twins discordant for AID and spontaneous autoimmune animal models have highlighted the importance of DNA methylation changes and histone modifications. Alterations in the epigenetic pattern seem to be cell specific, as CD4+ T cells and B cells are dysregulated in systemic lupus erythematosus, synovial fibroblasts in rheumatoid arthritis and cerebral cells in multiple sclerosis. With regard to lymphocytes, the control of tolerance is affected, leading to the development of autoreactive cells. Other epigenetic processes, such as the newly described miRNAs, and post-translational protein modifications may also be suspected. Altogether, a conceptual revolution is in progress, in AID, with potential new therapeutic strategies targeting epigenetic patterns.

Virus de l'hepatite C et hepatopathies chroniques a Dakar : etude cas-temoins

En Afrique noire; la place de l'infection par le virus de l'hepatite C (VHC) dans la survenue des hepatopathies chroniques reste discutee; en particulier au Senegal ou la prevalence du VHC est moderee. C'est pourquoi une etude cas-temoins a ete menee a l'Hopital Principal de Dakar; en 1995; incluant 73 malades et 73 temoins. Les malades etaient repartis en 2 hepatites chroniques; 25 cirrhoses et 46 carcinomes hepatocellulaires. Les malades et les temoins ont fait l'objet d'etude serologique vis-a-vis du VHC (test ELISA de depistage; test ELISA de 3e generation en cas de positivite; puis confirmation par immunoblot) avec determination du serotype du VHC par methode immunoenzymatique; une recherche d'infection par le virus de l'hepatite B et une recherche d'anticorps anti-delta ont complete l'etude. Seulement 2 malades etaient porteurs d'anticorps anti-VHC (3 p. 100) et la serologie etait douteuse chez 2 autres ; le serotype 2 a ete mis en evidence chez l'un de ces malades ; aucun temoin n'etait positif vis-a-vis du VHC. Cinquante-quatre malades (74 p. 100) et 15 temoins (21 p. 100) etaient porteurs de l'antigene HBs parmi lesquels 13 malades (24 p. 100) et 1 temoin (7 p. 100) etaient porteurs d'anticorps anti-delta. Cette etude montre le role actuellement negligeable du VHC dans la survenue des hepatopathies chroniques en milieu hospitalier au Senegal et confirme le role predominant du virus de l'hepatite B et aggravant du virus de l'hepatite delta. Ces resultats sont confrontes aux donnees de la litterature concernant les pays d'Afrique noire. Au Senegal; l'impact du VHC parait inferieur a celui qui est oberve en Afrique centrale

Renal involvement in Wegener's granulomatosis.

The term pauci-immune glomerulonephritis with vasculitis encompasses a group of auto-immune disorders, which includes Wegener's granulomatosis, microscopic polyangiitis, Churg-Strauss syndrome, and renal-limited vasculitis. Over the past few years, progress has been made in understanding the epidemiology and environmental and genetic risk factors of the role of antineutrophil cytoplasmic antibodies (ANCA) in kidney pathogenesis and the utilization of ANCA in diagnosis. However, certain aspects are still subject to debate including the classification and the place of ANCA in treatment.

Characterization of the human CD5 endogenous retrovirus-E in B lymphocytes.

All T lymphocytes and some B lymphocytes express CD5. This coreceptor is encoded by one gene that consists of 11 exons. We have previously described a B cell-specific alternative exon 1, leading to the synthesis of a protein, devoid of leader peptide, and, therefore, retained in the cytoplasm. The novel exon 1 originates from a human endogenous retrovirus (HERV) at a time interval between the divergence of New World monkeys from Old World monkeys, and prior to the divergence of humans from Old World monkeys. Based on sequence similarity to gamma-retroviruses, it was categorized as class I: based on the specificity of its primer binding site, it was allotted to the subclass E, and based on its location within the cd5 gene, named HERV-E.CD5. Alternative transcripts were detected in lymphoid organs including fetal liver (not adult liver), more particularly in CD5-negative cell surface B-1b than in CD5-positive cell surface B-1a, and not at all in B-2 cells. By alignment of 5' long terminal repeats, HERV-E.CD5 was distinguished from similar proviruses. This could be central to the regulation of membrane expression of CD5 in human B lymphocytes, and, thereby, to the strength of the B-cell antigen receptor signaling.

The ananti-alpha-actinin test completes ananti-DNA determination in systemic lupus erythematosus.

In murine systemic lupus erythematosus (SLE) models, nephritogenic anti-dsDNA IgG has been shown to cross-react with a kidney antigen, alpha-actinin, and to be critical in renal pathogenesis. In humans, studies of anti-alpha-actinin antibodies (Abs) are scarce, and these antibodies remain to be evaluated. We have thus far tested sera from patients with SLE (n = 103), rheumatoid arthritis (RA, n = 93), and primary Sjögren syndrome (pSS, n = 34), and from healthy subjects (n = 160), for the presence of anti-alpha-actinin and anti-DNA Abs. The latter were tested using several methods [IIF on Crithidia luciliae (Crit) and ELISA using dsDNA]. Anti-alpha-actinin Abs were confirmed by Western blot. Sera from 23 of 103 SLE patients, 3 of 93 RA patients, 1 of 33 pSS patients, and 1 of 160 controls scored positive for anti-alpha-actinin Abs. In SLE, the positivity was significantly associated with anti-dsDNA reactivity (22 of 23): 19 of 23 sera were alpha-actinin-positive/dsDNA-positive and 13 were alpha-actinin-positive/Crit-positive. Few cases were alpha-actinin-positive/dsDNA-negative: 1 SLE, 3 RA, and 1 control. Furthermore, anti-alpha-actinin Abs have been detected at high level before or at the early stage of lupus nephritis when compared with active and inactive SLE without kidney manifestations.

Role of B-cell antigen receptor-associated molecules and lipid rafts in CD5-induced apoptosis of B CLL cells.

A total of 40 patients with B-CLL were investigated for CD5-triggered apoptosis and categorized as 20 resistant (group I) and 20 sensitive patients (group II). The densities of surface IgM (sIgM) and CD5 were lower in group I than group II, as were the percentages of CD79b+, CD38+, and Zap70-expressing B cells. CD5 signaling was mediated through the BCR in group II B cells, as established by coimmunoprecipitation of CD5 and CD79a and tyrosine phosphorylation of CD79a. Following colocalization of CD5 and sIgM in membrane lipid rafts (LRs), Syk became associated with these molecules, whereas SHP-1 was uncoupled from CD5. Nonresponsiveness to CD5 cross-linking in group I was ascribed to three possible abnormalities, and defined as three subgroups of patients. In subgroups Ia and Ib, CD5 and sIgM colocalized within the LRs. SHP-1 remained attached to the BCR in subgroup Ia, but not in subgroup Ib, where signal transduction was associated with an excess of truncated CD79b. In subgroup Ic, CD5 and sIgM segregated into different LRs, resulting in no signaling of apoptosis.

Consequences of Fc gamma receptor type III reactivity in non-organ-specific autoimmune diseases.

Polymorphonuclear neutrophils (PMNs) express constitutively the Fc gamma receptors (Fc gamma Rs) Fc gamma RIIIb and Fc gamma RIIa for the Fc part of IgG, and soluble Fc gamma RIIIb (sFc gamma RIIIb) has been identified. Elevated levels of sFc gamma RIIIb were detected in non-organ-specific autoimmune conditions, and there was a considerably decreased number of PMNs undergoing apoptosis in the presence of sFc gamma RIIIb. Anti-Fc gamma RIIIb autoantibodies (autoAbs) have also been described in such patients. They are not cytotoxic to these cells, but they extend their survival. The anti-apoptotic signal can be transduced through Fc gamma RIIa and/or CD11b, the beta-chain of the complement receptor 3. However, Fc gamma RIIIb appears to be also competent. Anti-Fc gamma RIIIb-conditioned supernatant from cultured PMNs induces the transcription of messenger RNA for granulocyte colony-stimulating factor and granulocyte/macrophage colony-stimulating factor, followed by protein synthesis. The delay in apoptosis may be generated by a downregulation of the death promoter Bax. Inflammation might thus be modulated by sFc gamma RIIIb and anti-Fc gamma RIIIb autoAbs in systemic diseases.

Distinguishing features of anti-beta2 glycoprotein I antibodies between patients with leprosy and the antiphospholipid syndrome.

Anticardiolipin (ACA), anti-beta2 glycoprotein I (beta2GPI), and antiprothrombin antibodies of IgG and IgM classes were quantitated by enzyme-linked immunosorbent assays in 176 untreated leprosy patients across the histopathological spectrum. Positivity rates ranged from 21% (IgG ACA) to 30% (IgM anti-prothrombin) versus 4% in healthy controls (p <10(-2) to 10(-3)). Levels of IgM anti-beta2GPI and IgG ACA were significantly higher in lepromatous leprosy and multibacillary patient subgroups. IgG3 was the most common subclass reactive to both beta2GPI and prothrombin in selected high-titer leprosy sera, unlike antibodies from patients with the antiphospholipid syndrome (APS) largely restricted to IgG2. In leprosy patients, but not in the APS control group, there was no statistical correlation between ACA and anti-beta2GPI antibody levels. Likewise, a large fraction of anti-beta2GPI positive sera (36/45 and 28/44 for IgG and IgM, respectively) were unreactive in the standard ACA assay. Most assayed anti-beta2GPI antibodies from leprosy patients showed (i) ability to recognize both human and bovine beta2GPI immobilized on non-irradiated polystyrene plates, (ii) concentration-dependent inhibition of binding by cardiolipin, and (iii) relatively high avidity binding to fluid-phase beta2GPI, thereby differing from those found in APS. Finally, the location of the major epitopic region on the beta2GPI molecule targeted by autoantibodies was different in leprosy and APS, as assessed by direct binding to domain I- and V-deleted mutants and competition with the mouse monoclonal antibody 8C3, directed at domain I. Thus, leprosy-related antiphospholipid antibodies comprise persistent IgG and IgM anti-beta2GPI that differ from APS-related ones with respect to IgG subclass, avidity and epitope specificity, possibly reflecting distinct pathophysiological significance.

Anti-endothelial cell antibodies (AECA) in systemic sclerosis--increased sensitivity using different endothelial cell substrates and association with other autoantibodies.

OBJECTIVE: One of the main features of systemic sclerosis (SSc) is vascular damage, the mechanism of which is not understood. In the present study we examined whether screening of SSc patients for different anti-endothelial cells antibodies (AECA) of various origins increase the sensitivity of AECA detection in SSc patients. Secondary aim was an attempt to correlate AECA with other common autoantibodies. MATERIALS & METHODS: 478 SSc patients were studied for the presence AECA, anti-cardiolipin (aCL), anti-dsDNA, anti-heparin (AHA), anti-pyruvate dehydrogenase (PDH) and anti-PDC-E2 autoantibodies. AECA levels were detemined using human umbilical vein EC (HUVEC), bone marrow EC (BMEC), EC hybridoma (EA.hy 926) and Kaposi sarcoma EC (KS). RESULTS: Positive AECA were found in 49.5% of SSc patients (27.1% HUVEC; 34.3% BMEC; 26.3% EaHy 926 and 22.7% KS). The highest percent reactivity of AECA was obtained using microvascular BMEC. When combining BMEC and either other cell lines the reactivity ranged from 41.4% to 46%. A significant association between AECA on the one hand and AHA (p<0.001)) and anti-PDH (p<0.05) on the other was secn. Cross-reactivity with anti-PDC-E2 was excluded by inhibition tests, but AHA and anti-PDH may be part of the spectrum of AECA. CONCLUSIONS: Since false-negative AECA may result from lack of expression of various antigens on a specific EC, analysis of AECA in SSc patients requires using several EC types, including microvascular EC.

Cross-linking of human FcgammaRIIIb induces the production of granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor by polymorphonuclear neutrophils.

We have reported that human autoantibodies reacting with the polymorphonuclear neutrophil (PMN)-anchored FcgammaRIIIb (CD16) protect these cells from spontaneous apoptosis. In this study, we used anti-CD16 F(ab')(2) to delineate the mechanism(s) whereby the PMN life span is extended. As documented using four methods, CD16 cross-linking impeded spontaneous apoptosis, whereas anti-CD18 F(ab')(2) exerted no effect. Incubation of PMNs with anti-CD16 prevented the up-regulation of beta(2) integrins, particularly CD11b, which is the alpha-chain of complement receptor type 3, but also CD18, which is its beta-chain, as well as CD11a and CD11c. Anti-CD16-conditioned supernatant of PMNs diminished the percentage of annexin V-binding fresh PMNs after another 18 h in culture, whereas the negative control anti-CD18 had no effect. The expression of mRNA for G-CSF and GM-CSF was induced by anti-CD16, followed by the release of G-CSF and GM-CSF in a dose-dependent manner. Anti-G-CSF and anti-GM-CSF mAbs abrogated the antiapoptotic effect of the related growth factors. The delay in apoptosis was accompanied by a down-regulated expression of Bax, and a partial reduction of caspase-3 activity. These data suggest an autocrine involvement of anti-CD16-induced survival factors in the rescue of PMNs from spontaneous apoptosis. Thus, apoptosis of aged PMNs can be modulated by signaling through FcgammaRIIIb, which may occur in patients with PMN-binding anti-FcgammaRIIIb autoantibodies.

Recent progress in the understanding of B-cell functions in autoimmunity.

Our early concepts of the normal role of B cells in immunity focused on their ability to produce antibodies (Ab) and in the case of autoimmune diseases autoAbs, some of which were pathogenic. Over the past 10 years, it has became apparent that B cells display a variety of characteristics, other than Ab production, which could contribute to autoimmunity. They normally play a role in the development of lymphoid architecture, regulating T-cell subsets and dendritic cell (DC) function through cytokine production, and in activation of T cells. Receptors editing is also important in B cells which aids in immunity to infection and, possibly, prevention of autoimmunity. Transgenic animal models have now shown that B cells are necessary for many autoimmune diseases although their Ab products are not required in some cases. Negative signalling by CD5 and other molecules, such as CD22, in maintaining tolerance through recruitment of src-homology two domain-containing protein tyrosine phosphatase-1 has also been documented. In fact, we have now reached a new era whereby the B cell has returned as an important contributor to autoimmune disorders, so that the race is on to characterize signalling regulation via the B-cell receptor and coreceptors. Identification of such molecules and their potential defects should lead to effective ways of controlling the immune response and in particular preventing the development of autoimmune states. The classical view of B cells in the biology of immune responses to infectious and self-antigens (Ag) that they promote immunity primarily by producing Ab turns out to be rather naïve. Indeed, studies over the last few years indicate that this view is far from complete, and suggest that B lymphocytes have extraordinarily diverse functions within the immune system. Furthermore, it is becoming increasingly clear that the pathogenesis of autoimmune diseases cannot solely be accounted for by T cells, and intrinsic abnormalities of B cells have been described in such conditions. In this brief review we highlight some recent observations in the context of B lymphocyte in pathophysiology, and focus on their revival as pivotal players the pathophysiology in autoimmune diseases. Yet, it remains difficult to provide a model of how important B cells are in immunity and autoimmunity.

Soluble Fcgamma receptor IIIb alters the function of polymorphonuclear neutrophils but extends their survival.

We have established that polymorphonuclear neutrophil (PMN)-binding anti-Fcgamma receptor IIIb (FcgammaRIIIb) autoantibodies (autoAb) inhibit the function of these cells but extend their survival. Here, we show that recombinant FcgammaRIIIb (rFcgammaRIIIb), as well as purified FcgammaRIIIb (pFcgammaRIIIb), deteriorated the PMN adherence and respiratory burst in a dose-dependent manner. Furthermore, rFcgammaRIIIb and pFcgammaRIIIb reduced the level of annexin V-binding PMN from 23.6 +/- 1.6 % to 6.3 +/- 1.0 and 11.0 +/- 1.0 %, respectively, while human serum albumin exerted no effects. Incubation of rFcgammaRIIIb with those autoAb binding to soluble FcgammaRIIIb resulted in the attachment of such immune complexes (IC) to the cells, thereby also delaying apoptosis (44.9 +/- 5.9 versus 18.0 +/- 2.0 % annexin V-binding PMN after 16 hours). Soluble FcgammaRIIIb, in concert with FcgammaRIIIb / anti-FcgammaRIIIb IC, produced similar effects in that the percentage of annexin V-binding PMN declined to 16.0 +/-1.9 %. It was thus suggested that FcgammaRIIIb / anti-FcgammaRIIIb IC inserted the Fc region of their IgG into the membrane FcgammaRIIIb. Such an interpretation is consistent with our finding that, whereas aggregated IgG and anti-FcgammaRIIIb monoclonal Ab prevented membrane FcgammaRIIIb / IC interaction, neither soluble FcgammaRIIIb, nor anti-cgammaRII did so. We conclude that the function and the life span of PMN are influenced synergistically by soluble FcgammaRIIIb and anti-FcgammaRIIIb autoAb.

Functional heterogeneity of anti-endothelial cell antibodies.

While it has been claimed that some anti-endothelial cell antibodies (AECA) activate EC, there is also evidence that others trigger apoptosis. To address the issue of whether activation is a prerequisite for AECA-mediated apoptosis of EC, 23 AECA-positive sera were evaluated for their ability to induce activation and/or apoptosis. Activation was defined as an over-expression of E-selectin and intercellular adhesion molecule 1. Optical microscopy, annexin V binding, hypoploid cell enumeration, and determination of poly (ADP-ribose) polymerase cleavage-related products were used to assess apoptosis. Four functional profiles were defined: 10 sera promoted activation and apoptosis (act+/apo+), one was act+/apo-, six act-/apo+, and the remaining six act-/apo-. The reduced membrane expression of thrombomodulin was associated with apoptosis, rather than activation. Caspase-3 was implicated in the two models of apoptosis, the ratios of several survival proteins to Bax decreased, regardless of the ability of apo+ AECA to activate the cells, while radical oxygen species did not appear to be involved. Furthermore, it occurred that macrophages engulfed EC treated with apoptosis-promoting AECA, but not those incubated with AECA that did not induce apoptosis. Hence, AECA represent an extremely heterogeneous family of autoantibodies, not only because of the variety of their target antigens, but also the subsequent diversity of their effects.

Differential effects of anti-Fc gamma RIIIb autoantibodies on polymorphonuclear neutrophil apoptosis and function.

Anti-Fc gamma receptor IIIb (Fc gammaRIIIb) human autoantibodies (Ab) have been classified previously into three groups, based on the results of an indirect immunofluorescence (IIF) test and an enzyme-linked immunosorbent assay (ELISA): IIF+/ELISA+ (group A), IIF+/ELISA- (group B), and IIF-/ELISA+ (group C) sera. In this study, differential effects between IIF+ autoAb, recognizing cell-bound Fc gammaR, and those ELISA+, recognizing only cell-free Fc gammaR, were studied on polymorphonuclear neutrophils (PMN). Neither group A nor B autoAb was cytotoxic, although both prolonged the survival of PMN by delaying spontaneous apoptosis. By the same extent, the PMN-binding antisera stimulated the appearance of a CD11b(dim) population, following a 12-h incubation. This event was associated with a lowered expression of beta2 integrin molecules, resulting in altered PMN function. Treatment with groups A and B autoAb reduced adhesiveness and respiratory burst. This impairment of the responses was more pronounced when the cells originated from donors NA1+ NA1+ rather than donors NA2+ NA2+. From our observations, the influences of anti-Fc gammaRIIIb autoAb on PMN survival, as well as function and subsequent dysregulation of the inflammatory response, have proven somewhat dependent on their target antigens, as determined by IIF coupled with ELISA and Fc gammaRIIIb polymorphism.