Function In Systemic Lupus Erythematosus Research Articles

Presence of antibodies to SSB/La is associated with decreased phagocytic efficiency of neutrophils in patients with systemic lupus erythematosus

SSB/La antigen, expressed on surface of polymorphonuclear neutrophils (PMN), is one of the cognate antigens recognized by antineutrophil antibodies. The present study was aimed to assess PMNs in systemic lupus erythematosus (SLE) patients for their phagocytic efficiency and its correlation with history of infections and presence of anti-SSB/La antibodies and their capacity to produce interleukin (IL)-12 in response to lipopolysaccharide (LPS) with or without interferon gamma (IFN-gamma). Fifty patients with SLE, fulfilling American College of Rheumatology criteria of diagnosis, and 20 healthy controls were enrolled for the study. Phagocytic efficiency was evaluated by flow cytometry, using flourescein isothiocyanate (FITC)-labeled Escherichia coli, and expressed as mean channel fluorescence (MFI). PMNs were stimulated with LPS or LPS + IFN-gamma for 18 h, IL-12p40 was estimated in supernatants by enzyme-linked immunosorbent assay, and anti-SSB/La antibodies were detected in serum by Western blot. The mean MFI values were significantly lower in patients with SLE than controls (P < 0.0001), and among patients, it was lower in patients with history of infection than in those without (P < 0.005). Anti-SSB/La positivity was also associated with lower MFI (P < 0.005) and higher frequency among patients with history of infective episodes (P < 0.05). LPS- and LPS + IFN-gamma-stimulated IL-12 levels were lower among SLE patients than in controls. However, there was no difference in the levels of IL-12 between patients with and without history of infection. These data suggest that the autoantibodies to SSB/La may modulate PMN function in SLE.

Pulmonary dysfunction in systemic lupus erythematosus and anti‐phospholipid syndrome patients

Objective: To assess and compare parameters of pulmonary function in systemic lupus erythematosus (SLE) and anti‐phospholipid syndrome (APS) patients.Methods: Consecutive patients (n = 74) who were free of respiratory symptoms were divided into four groups: 1) SLE (n = 23); 2) SLE with anti‐phospholipid antibodies (aPL) (n = 18); 3) SLE with APS (n = 20); and 4) primary APS (PAPS) (n = 13). Pulmonary function testing, single breath diffusion capacity of carbon monoxide (DLCO/SB) and echocardiography studies were performed. Induced sputum cytology was analysed.Results: Forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), and DLCO were significantly reduced in SLE compared to PAPS patients (p = 0.039; p = 0.017; p = 0.029, respectively). Elevated pulmonary arterial pressure was observed in two patients with SLE and aPL and in two with SLE and APS. Lymphocyte and eosinophil counts in induced sputum showed no significant differences; however, a trend towards lower CD4 counts in SLE vs. PAPS was noted (p = 0.086), while in patients with both SLE and APS, a low CD4/CD8 ratio was seen. Patients with APS were older than patients without APS (47.12±14.86 vs. 34.29±12.6, p = 0.0001), while SLE patients were younger than PAPS patients (38.19±14.68 vs. 48.53±13.97, p = 0.023).Conclusion: Abnormal pulmonary functions tests were detected frequently in asymptomatic patients with SLE or PAPS. Although SLE patients were younger, pulmonary function was significantly more impaired in SLE as compared to PAPS patients.

CAMP response element modulator α expression in patients with systemic lupus erythematosus

T cells from patients with systemic lupus erythematosus (SLE) have high levels of cAMP response element modulator (CREM)-alpha which bind to the interleukin (IL-2) promoter and limit IL-2 production. In this case-controlled study, we show that CREM-alpha mRNA levels were higher in T cells from patients with SLE than controls while CREB mRNA levels did not differ between the two groups. CREM-alpha mRNA levels did not correlate with clinical characteristics, disease activity or treatment. Nevertheless, there was a trend for patients on high doses of corticosteroids to have low levels of CREM-alpha mRNA. The discovery of specific non-toxic medications that block the expression of CREM-alpha may prove useful in reversing the aberrant T cell function in SLE.

Right Heart Function in Systemic Lupus Erythematosus: Insights from Myocardial Doppler Tissue Imaging

The purpose of this study was to use Doppler tissue imaging to evaluate heart function and to investigate the correlation between Doppler imaging and pulmonary artery systolic pressure (PASP) and right ventricular (RV) ejection fraction (EF) in patients with systemic lupus erythematosus (SLE). Standard echocardiography and 2-dimensional and color Doppler imaging were used to assess cardiac function in patients given the diagnosis of SLE (n = 40) and healthy control subjects (n = 45). Half of the patients with SLE also presented with pulmonary hypertension (PH). Significant differences in PASP and RV EF (RVEF) were found between the control and SLE groups. The peak systolic velocity of tricuspid annulus was significantly lower in patients with SLE than in the control group. The calculated myocardial performance index of the RV, septum, and left ventricular lateral wall were significantly higher in patients with SLE than in the control group. Bivariate correlation analysis revealed a significant correlation among PASP, RVEF, and systolic tricuspid annular velocity. There was a significant correlation between each of these 3 parameters and the 6-minute walk distance in patients with SLE. Patients with SLE and PH had a significantly shorter 6-minute walk distance than patients with SLE without PH. Furthermore, in patients with SLE and PH, RVEF and systolic tricuspid annular velocity were lower than in the control subjects and patients with SLE without PH. Patients with SLE and PH had a longer isovolumic relaxation time and a higher myocardial performance index of RV than those without PH. Finally, by simple linear regression analysis, we found a significant positive relation between RVEF and systolic tricuspid annular velocity, but a negative relationship between PASP and systolic tricuspid annular velocity. These findings demonstrate that in patients with SLE, systolic tricuspid annular velocity determined by echocardiography and Doppler imaging can be used to assess RV function and PASP. Furthermore, systolic tricuspid annular velocity reflects exercise tolerance in patients with SLE and the length of the isovolumic relaxation time represents the progression of PH.

Evaluation of Auditory System Function in Systemic Lupus Erythematosus

Evaluation of Auditory System Function in Systemic Lupus Erythematosus

Endothelial function in systemic lupus erythematosus: relationship to disease activity, cardiovascular risk factors, corticosteroid therapy, and coronary calcification

Endothelial dysfunction is frequently present in patients with systemic lupus erythematosus and may increase their risk of premature coronary artery disease. In this pilot study we have characterized the relationship between endothelial function, measures of disease activity, and cardiovascular risk factors in patients with lupus. Clinical characteristics and cardiovascular risk factors were evaluated in 20 patients with lupus. Flow-mediated dilation of the brachial artery was measured using high resolution ultrasound and the presence or absence of coronary calcification determined by electron-beam computed tomography. The relationship between these variables and flow-mediated dilation was determined using Spearman correlation coefficients (RHO) and Mann Whitney-Wilcoxon tests. Twenty patients (17 female) median age (interquartile range) 42.5 (32.0-47.5) years were studied. The median flow-mediated vasodilation was 3.6% (1.7%-7.7%). In patients with coronary calcification (n = 6), flow-mediated dilation was 2.1% (-0.42%-3.6%) compared with 4.0% (3.5%-8.3%) in those without (p = 0.12). There was no significant relationship between flow-mediated dilation and markers of disease activity, duration of disease, and cardiovascular risk factors. Lower flow-mediated dilation was associated with duration of corticosteroid therapy (RHO = -0.44, p = 0.05). In these preliminary results, endothelial dysfunction is associated with long-term exposure to corticosteroids.

Impairment of Left Ventricular Function in Systemic Lupus Erythematosus Evaluated by Measuring Myocardial Performance Index with Tissue Doppler Echocardiography

In 44 patients affected by systemic lupus erythematosus (SLE) without any clinical signs of heart disease (group I) the myocardial performance index (MPI) was calculated to investigate left ventricular function. The index, as the sum of isovolumetric contraction time (ICT) and isovolumetric relaxation time (IRT) divided by ejection time (ET), was measured by tissue Doppler echocardiography (TDE). Results achieved show a prolonged MPI with respect to the values recorded in healthy controls (group II). Its prolongation is due to a significant increase of IRT, whereas ICT and ET were within the normal limits. In patients with SLE without an evident cardiac engagement, this outcome seems to depend on a prevalent diastolic left ventricular dysfunction, perhaps due to a subclinical myocarditis. TDE is more precise than the conventional Doppler method in evaluating MPI and single time intervals, because their measurements are accomplished in concomitance of left ventricular wall motion rather than the flow movement.

A revised assay for the measurement of T-cell receptor excision circles as a quantitative measure of thymic function in systemic lupus erythematosus

In 1998 Douek and colleagues described a novel approach to measuring thymic output using T-cell receptor excision circles (TRECs) measured in CD4+ and CD8+ T cells. TRECs are byproducts of T-cell receptor gene re-arrangements, whereby sections of excised DNA re-form as stable episomes that do not replicate with mitosis. TRECs present in T cells arising from the thymus are thus 'diluted out' upon T-cell division and can be used as a surrogate marker of thymic output. However, the interpretation of TREC number in lymphocyte subsets is confounded by the influences of T-cell proliferation, intracellular TREC degradation and T-cell death, and it has been criticised as a measurement of thymic function. Here, we describe a method for quantifying TRECs in whole blood. This revised assay provides a representation of 'total peripheral TRECs'. The effects of T-cell proliferation and cell death on the determined absolute TREC level are minimised, providing us with an improved estimation of thymic function over time. In a series of validation experiments our assay has been shown to have excellent intra-assay and inter-assay reproducibility and to generate results consistent with previously published work in healthy controls. We are now using this assay to determine thymic function in the autoimmune disease systemic lupus erythematosus to test our hypothesis that a defect in thymic function contributes to lupus pathogenesis. To measure the absolute TREC number per unit volume of blood (as a representation of 'total peripheral TRECs'), the amount of DNA extracted from a volume of whole blood must be representative of 'total' DNA in that volume of blood. We have compared four methods of DNA extraction from whole blood for consistency of yield and purity. Figure ​Figure1a1a shows the mean DNA yield from parallel extractions (n = 10) performed after (a) 1 hour, (b) 6 hours and (c) 24 hours from collection for a single sample. The overall mean yield was 32.23 μg/ml ± 2.3 standard deviations (SDs). Two further, separate, samples were similarly prepared in parallel to confirm consistency – (d) 26.8 μg ± 1.97 SD and (e) 26.9 μg ± 2.23 SD (n = 10). To measure TRECs in samples we have used a quantitative real-time PCR (TAQMAN™) assay to amplify a known proportion of the extracted DNA. The total TREC number per sample is determined absolutely from a standard curve (derived from a plasmid containing TREC sequence) and final values are presented as TRECs per millilitre of whole blood. Figure ​Figure1a1a (top axis) shows that the TREC number is reproducibly calculated from parallel extractions (n = 5). The intra-assay coefficient of variation is 1.4% (range 0.8–2.5%) while the inter-assay co-efficient of variation is 2.4% (range 0.6–4.4%). The coefficient of variation is negatively correlated with TREC number (r2 = 0.83 and 0.66, respectively). Using this assay we have also shown that TRECs are reliably detectable in healthy controls (Fig. ​(Fig.1b)1b) and show an age-related decline in keeping with the known reduction in thymic volume over time. TRECs are not detectable in RAJI (human B-cell lymphoma line) or SW48 (human colonic carcinoma cell line) (data not shown). We are now using this assay to determine the TREC number in the autoimmune disease systemic lupus erythematosus to test our hypothesis that a defect in thymic function contributes to lupus pathogenesis. Figure 1 (a) Lower axis: serial DNA extractions (see text). Bars represent mean of 10 ± standard deviation. Upper axis: T-cell receptor excision circles (TRECs) per millitre of blood from the same samples (mean ± deviation). (b) TRECs per millitre ... While measurement of TRECs in T cells and their subsets provides a representation of thymic function in the steady state, in the context of autoimmunity, where abundant auto-antigen provides a constant T-cell-activating stimulus, interpretation of the TREC number within lymphocyte subsets is confounded. By reliably and reproducibly estimating total peripheral TRECs we aim to minimise the impact of T-cell turnover on TREC number in order to gain a better understanding of thymic function in systemic lupus erythematosus.

Transcriptional down‐regulation of the platelet ADP receptor P2Y12 and clusterin in patients with systemic lupus erythematosus

Cardiovascular complications are common in systemic lupus erythematosus (SLE) and myocardial infarctions are the leading cause of increased mortality. The ADP receptor P2Y(12) plays a central role in platelet activation and the P2Y(12) blocker clopidogrel reduces the incidence of cardiovascular events. Clusterin, a complement inhibitory protein suggested to be involved in the pathogenesis of SLE, has been found recently in a microarray study to be expressed at very high levels in platelets. Using a new protocol for mRNA quantification in platelets we set out to study if gene expression is altered in SLE patients compared with a healthy control group. Quantitative assay based on real-time PCR was used to measure mRNA expression, Western blot for P2 receptor protein expression and PFA-100 for platelet aggregation. The P2Y(12) receptor expression was decreased in SLE compared to the controls (P < 0.05), while expression of P2Y(1) and P2X(1) were unaltered. These findings were consistent at the protein level. The clusterin mRNA expression was very high. However, SLE patients had significantly lower levels than controls (P < 0.05). Platelet aggregation was similar in both groups. It may be suggested that a decreased level of P2Y(12) receptors could represent a protective response in SLE against thrombotic complications. Lowered clusterin levels could be involved in the pathogenesis of SLE due to decreased protective effects. These findings could help to achieve a better understanding of the platelet function in SLE and serve as a guide for further research and drug use.

Relationship between myocardial perfusion scinti-graphy and brachial artery endothelial function in systemic lupus erythematosus

Background: Up to 35% of patients with SLE have abnormalities on myocardial perfusion imaging (MPI).It is postulated that endothelial dysfunction (EdF) is a precursor to atherosclerosis and may contribute to abnormalities on MPI. Aim: To determine the relationship between EdF measured using brachial artery Doppler ultrasound and MPI in patients with SLE. Method: This was a prospective study of 76 women with SLE, without clinical CAD. Assessment of EdF using brachial artery Doppler ultrasound was performed in all patients. Endothelium-dependent ( ed) and independent ( eid) flow mediated dilatation (FMD) was measured in response to post-ischemic reactive hyperemia and sublingual GTN respectively. All patients also underwent rest-stress MPI using SPECT 99mTc sestamibi using dipyridamole stress. MPI was interpreted using a 20 segment model. Summed stress score (SSS) were computed. Results: 40(52.6%) patients had both normal FMD and MPI. 7(9.2%) patients had both abnormal FMD and MPI. 8(10.5%) patients had abnormal FMD alone while 21(27.6%) patients had abnormal MPI alone. 36(47.4%) had an abnormality in either or both investigations. There was no agreement between FMD and MPI (Kappa=9.2%, correlation coefficient = −0.01, NS). However in an analysis of continuous variables, there was a statistically significant but weak negative correlation between eid and MPI (correlation coefficient = −0.35, p=0.002). Conclusion: In this study there was no agreement between FMD and MPI. Abnormal FMD with normal MPI is in keeping with the hypothesis that endothelial dysfunction is a precursor to myocardial ischemia, whereas normal FMD with abnormal MPI may reflect external influences such as treatment with statins at the time of study. Our findings indicate that brachial FMD and myocardial scintigraphy are complementary investigations in assessing the cardiovascular health of patients with SLE and should not be used interchangeably. When used in combination, brachial FMD and myocardial scanning identify around 47.4% of patients with SLE who may be at risk of developing clinical coronary artery disease.

Protein kinase A and signal transduction in T lymphocytes: biochemical and molecular methods.

Abnormal T-cell effector functions in systemic lupus erythematosus (SLE) are present and may be associated with disease immunopathogenesis. Our work has led to the characterization of a signaling defect, involving protein kinase A (PKA), leading to abnormal T-cell effector functions in SLE. PKA is a component of the adenylyl cyclase/cyclic adenosine monophosphate/PKA (AC/cAMP/PKA) pathway, a principal signal transduction system in T cells. The aim of this chapter is to provide a comprehensive, technical, step-by-step approach to studying PKA function in T cells. The methods detailed here are (a) chromatographic fractionation of PKA-I and PKA-II isozymes and PKA phosphotransferase activity in purified T cell populations, (b) Western immunoblotting to identify the presence of regulatory (R)-subunit proteins of PKA, and (c) isolation of RNA, and quantification of PKA R subunit-specific transcripts by competitive polymerase chain reaction. Although our emphasis in the chapter is T cells, these methods may be useful for investigation of signaling via PKA in other cell types as well.

Correlation between circulating CD27high plasma cells and disease activity in patients with systemic lupus erythematosus.

Disease activity in systemic lupus erythematosus (SLE) is usually assessed with complex disease activity scores comprising a variety of different parameters. In order to determine whether SLE disease activity correlates with abnormal B lymphocyte activity, B cell subsets were analyzed, and their relationship to clinical and humoral measures of disease activity was assessed. The distribution of B cell subsets was determined by fluorescence-activated cell sorting analysis and assessed in relation to the autoantibody profile, disease activity measured by the SLE Disease Activity Index (SLEDAI) and the European Consensus Lupus Activity Measure scores, disease duration, and therapy. The number and frequency of CD27(high) plasma cells were significantly correlated with the SLE disease activity indices and with the titer of anti-double-stranded DNA (anti-dsDNA) autoantibodies. Circulating B cell subsets were not influenced by age or sex, but appeared to relate to the duration of disease and the therapeutic regimen, with the number and frequency of CD27(high) plasma cells increasing and those of CD27- naive B cells decreasing over time. Patients were divided into those with a SLEDAI score of 0-8 (low disease activity) and those with SLEDAI score >8 (high disease activity). Patients with high disease activity had an increased frequency of both CD19+ B cells and CD27(high) plasma cells. By using a nonparametric data sieving algorithm, we observed that these B cell abnormalities provided predictive values for nonactive and active disease of 78.0% and 78.9%, respectively. The predictive value of the B cell abnormalities (78.9%) was greater than that of the humoral/clinical data pattern (71.4%), including anti-dsDNA antibody levels, circulating immune complexes, increased erythrocyte sedimentation rate, mucocutaneous involvement, and acute renal involvement. Flow cytometric monitoring of B cell subsets in the peripheral blood provides new insights into abnormalities of B cell function in SLE and may also be a diagnostically valuable option for monitoring the activity of this autoimmune disease.

Analysis of B-cell subpopulations in systemic lupus erythematosus

Abnormalities in humoral immunity play a significant role in systemic lupus, mandating further studies in B-cell autoimmunity in this entity. Disease activity in systemic lupus erythematosus (SLE) is usually assessed with complex disease activity scores composed of a variety of different parameters. To determine whether SLE disease activity correlated with abnormal B-lymphocyte activity, B-cell subsets were analyzed and related to clinical measures. The distribution of B-cell subsets was determined by fluorescence-activated cell sorting analysis and compared with the autoantibody profile, with the disease activity measured by the SLE disease activity index (SLEDAI) and the European Consensus Lupus Activity Measurement (ECLAM), disease duration and therapy. The number and frequency of CD27high plasma cells were significantly correlated with the SLE disease activity indices (SLEDAI and ECLAM) and the titer of anti-dsDNA autoantibodies. Circulating B-cell subsets were not influenced by age or gender, but appeared to relate to the duration of disease and the therapeutic regimen, with the numbers and frequencies of CD27high plasma cells increasing and those of CD27-naive B cells decreasing over time. Patients were divided into those with a SLEDAI score of 0–8 (low activity) and those with a SLEDAI score > 8 patients (high activity). High-activity patients were found to have an increased frequency of CD19+B cells as well as CD27high plasma cells. Using a nonparametric data sieving algorithm, these B-cell abnormalities exhibited predictive values for nonactive and active disease of 78.0% and 78.9%, respectively. The predictive value of the B-cell abnormalities was greater than that of the humoral/clinical data pattern, including anti-DNA antibody levels, circulating immune complexes, increased erythrocyte sedimentation rate, mucocutaneous and acute renal involvement, which showed predictive values of 77.8% and 70.0% for active and nonactive disease. Flow cytometric monitoring of B-cell subsets in the peripheral blood provides new insights into the abnormalities in B-cell function in SLE, and may also be a diagnostically valuable option to follow disease activity in this autoimmune disease.

Cardiac valvular abnormalities are frequent in systemic lupus erythematosus patients with manifest arterial disease.

The objective of this study was to study cardiac valve morphology and function and ventricular function in systemic lupus erythematosus (SLE) patients with and without co-existing cardiovascular disease (CVD) and in population controls. Twenty-six women (52 +/- 8.2 years) with SLE (SLE cases) and a history of CVD (angina pectoris, myocardial infarction, cerebral infarction or intermittent claudication) were compared with 26age-matched women with SLE but without manifest CVD (SLE controls) and 26 age-matched control women (population controls). Echocardiographywas performed to assess valvular abnormalities and manifestations of ischaemic heart disease. Thirteen of the 26 SLE cases but only one of the SLE controls and one of the population controls had cardiac valvular abnormalities. Three of the SLE cases had already undergone valve replacement and another had significant aortic insufficiency; the other nine had thickening of mainly mitral leaflets without hemodynamic significance. Among SLE cases, patients with valvular abnormalities had higher homocysteine (P < 0.001) and triglyceride (P = 0.02) concentrations than patients without valvular disease. In contrast atherosclerosis as determined by IMT, oxidized LDL as measured by the monoclonal antibody E06, autoantibodies against epitopes of OxLDL (aOxLDL) or phospholipids (aPL), disease duration or activity, or acute phase reactants did not differ between SLE cases with or without valvular abnormalities. Valvular abnormalities were not more common in SLE cases with stroke as compared to those with myocardial infarction, angina or claudication. In conclusion, valvular abnormalities are strongly associated with CVD in SLE. Raised levels of homocysteine and triglycerides characterize patients with cardiac valve abnormalities.

Increased interferon-gamma (IFN-gamma), IL-10 and decreased IL-4 mRNA expression in peripheral blood mononuclear cells (PBMC) from patients with systemic lupus erythematosus (SLE).

Cytokines are important regulators of lymphocyte function in SLE. However, the profile of Th1 and Th2 cytokines produced by circulating lymphocytes in human SLE has not been clearly elucidated. The aim of the present study was to characterize the gene expressions of the Th1-type cytokine IFN-gamma, and the Th2-type cytokines IL-10 and IL-4 in PBMC of 15 patients with SLE and 10 healthy individuals by a semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR). Our results showed that expression of IFN-gamma (P = 0.0004) and IL-10 (P = 0.002) transcripts were significantly increased in PBMC of patients with SLE compared with healthy controls. By contrast, expression of IL-4 transcripts in PBMC of patients with SLE was significantly decreased compared with the healthy controls (P = 0.0008). Primary sources of IL-10 were B cells and monocytes, with variable contribution of T cells as detected in various fractions of PBMC of patients with SLE (P = 0.049). These findings support the hypothesis that the enhanced production of IFN-gamma by mononuclear cells may trigger inflammatory responses, together with the enhanced production of IL-10 resulting in autoantibody production by B cells in human SLE.

Protein Kinase A RIβ Subunit Deficiency in Lupus T Lymphocytes: Bypassing a Block in RIβ Translation Reconstitutes Protein Kinase A Activity and Augments IL-2 Production

A profound deficiency of type I protein kinase A (PKA-I or RIalpha/beta2C2) phosphotransferase activity occurs in the T lymphocytes of 80% of subjects with systemic lupus erythematosus (SLE), an autoimmune disorder of unknown etiology. This isozyme deficiency is predominantly the product of reduced or absent beta isoform of the type I regulatory subunit (RIbeta). Transient transfection of RIbeta cDNAs from SLE subjects into autologous T cells that do not synthesize the RIbeta subunit bypassed the block, resulting in RIbeta subunit synthesis and restoration of the PKA-Ibeta (RIbeta2C2) holoenzyme. Transfected T cells activated via the T cell surface receptor complex revealed a significant increase of cAMP-activatable PKA activity that was associated with a significant increase in IL-2 production. These data demonstrate that a disorder of RIbeta translation exists, and that correction of the PKA-I deficiency may enhance T lymphocyte effector functions in SLE.

Ethnic differences in cognitive function in systemic lupus erythematosus

Ethnic differences in cognitive function in systemic lupus erythematosus

Ethnic differences in cognitive function in systemic lupus erythematosus

Ethnic differences in cognitive function in systemic lupus erythematosus

Impaired phagocytosis of apoptotic cell material by monocyte-derived macrophages from patients with systemic lupus erythematosus.

To investigate whether the established impaired phagocyte function in systemic lupus erythematosus (SLE) patients also affects apoptotic cell clearance. Accumulation of apoptotic waste as a source for autoantigens that induce and maintain autoimmune responses is discussed. Apoptosis was detected by morphology and propidium iodide staining. In vitro phagocytosis of autologous apoptotic cells in cultured peripheral blood mononuclear cells was evaluated microscopically. Cross-feeding experiments were performed to investigate phagocytosis of heterologous apoptotic cells by in vitro-differentiated macrophages. Furthermore, the effect of annexin V on the phagocytosis of apoptotic cells was investigated. Reduced clearance of apoptotic cells in SLE patients was observed. The defective clearance appeared to reflect phagocyte dysfunction and not an abnormal execution of apoptosis. A similar picture was seen when in vitro-differentiated macrophages from control populations were treated with annexin V. Noninflammatory engulfment phagocytosis of apoptotic cells is decreased in SLE patients. Persistently circulating apoptotic waste may encounter inflammatory removal pathways and serve as immunogen for the induction of autoreactive lymphocytes and as antigen for immune complex formation.

Fas ligand expression and function in systemic lupus erythematosus.

Mutations in the Fas receptor or its ligand (FasL) lead to lupus-like systemic autoimmune diseases in mice and in some humans. To determine whether a significant number of patients with systemic lupus erythematosus (SLE) have impaired FasL function, we compared T cell effector function by superantigen-activated CD4+ T cell lines or by anti-CD3- and IL-2-generated cytotoxic T cells. No differences were observed between SLE and normal control superantigen-derived CD4+ T cells in either the ability of these cells to up-regulate Fas expression or to induce apoptosis of the Fas-sensitive target B cells. When anti-CD3/IL-2-activated T cells were examined, SLE T cells had a modest reduction (-8%) in T cell cytotoxicity compared with normal controls, but the reduction was similar to the rheumatoid arthritis disease controls. A modest reduction in cytotoxicity was evident in both the Fas and perforin/granzyme pathways as determined by testing Fas-positive and -negative targets as well as by selective blockade of the perforin/granzyme pathway with concanamycin. These results indicate that no specific defects in FasL function are evident in the majority of SLE patients under the in vitro conditions tested. The proportional reduction in FasL and perforin/granzyme function in SLE and rheumatoid arthritis patients following anti-CD3/IL-2 stimulation most likely reflects subtle differences in activation in patient-derived vs normal control T cells.