Antigens In Systemic Lupus Erythematosus Research Articles

Tumour-associated antigens in systemic lupus erythematosus: association with clinical manifestations and serological indicators.

To explore the relationship of tumour-associated antigens (TAAs) with the clinical manifestations and serological markers of SLE. This was a retrospective study. Clinical data of SLE patients were extracted from the electronic medical records, including serum levels of TAAs such as alpha-fetoprotein (AFP), carcinoembryonic antigen (CEA), cancer antigen (CA) 19-9, CA125, CA15-3 and cytokeratin 19-fragments (CYFRA21-1). TAA positivity was defined as serum level exceeding the upper limit of the corresponding reference range. A total of 149 SLE patients (SLE group) and 149 age- and sex-matched healthy subjects (control group) were enrolled. Compared with healthy controls, the SLE group had higher positivity rates for CA19-9 and CYFRA21-1, and elevated serum levels of CA125, CA15-3 and CYFRA21-1. SLE patients with TAA positivity were older, had a higher prevalence of serous effusion, pericardial effusion, albuminuria and thrombocytopenia, and lower positivity rate for anti-dsDNA than patients without TAA positivity. The levels of serum creatinine (SCR), blood urea nitrogen, glutamic oxalate transaminase and 24-h urinary protein were also higher in SLE patients with TAA positivity, but platelet count and serum albumin levels were lower. On logistic regression, thrombocytopenia and SCR levels were identified as independent risk factors for TAA positivity. CA125 positivity rate and serum levels of CA125 were associated with SLE disease activity. The positivity rates and serum levels of some TAAs were elevated in SLE, and thrombocytopenia and SCR levels were independent risk factors for TAA positivity.

Platelets release mitochondrial antigens in systemic lupus erythematosus.

The accumulation of DNA and nuclear components in blood and their recognition by autoantibodies play a central role in the pathophysiology of systemic lupus erythematosus (SLE). Despite the efforts, the sources of circulating autoantigens in SLE are still unclear. Here, we show that in SLE, platelets release mitochondrial DNA, the majority of which is associated with the extracellular mitochondrial organelle. Mitochondrial release in patients with SLE correlates with platelet degranulation. This process requires the stimulation of platelet FcγRIIA, a receptor for immune complexes. Because mice lack FcγRIIA and murine platelets are completely devoid of receptor capable of binding IgG-containing immune complexes, we used transgenic mice expressing FcγRIIA for our in vivo investigations. FcγRIIA expression in lupus-prone mice led to the recruitment of platelets in kidneys and to the release of mitochondria in vivo. Using a reporter mouse with red fluorescent protein targeted to the mitochondrion, we confirmed platelets as a source of extracellular mitochondria driven by FcγRIIA and its cosignaling by the fibrinogen receptor α2bβ3 in vivo. These findings suggest that platelets might be a key source of mitochondrial antigens in SLE and might be a therapeutic target for treating SLE.

Characterization of CD4+ T cells expressing an elevated interferon-stimulated gene signature in SLE patients

Abstract The type I interferon (IFN) signaling pathway plays a key role in Systemic Lupus Erythematosus (SLE) pathology, and a majority of patients display elevated expression levels of interferon-stimulated genes (ISGs) in the peripheral blood. However, it is unclear which immune cells are responding to IFN to drive disease pathology. We compared the ISG signatures of cell types sorted from peripheral blood of IFNβ-treated relapsing-remitting multiple sclerosis (RRMS) patients with those of SLE patients. While systemic IFNβ treatment stimulated ISG expression in the monocytes and neutrophils of RRMS patients, the ISG signature in SLE patients was primarily detected in CD4+ T and B cells. This suggests these cells may be exposed to higher levels of IFN in microenvironments of inflammation within SLE patients, such as upon interaction with APC presenting SLE antigens. We hypothesize that a subset of primarily antigen-specific CD4+ T cells expand and express ISGs during SLE disease activity, and that these cells and their signature pathways can serve as disease biomarkers and therapeutic targets. To examine ISG expression by CD4+ T cells in SLE, we compared the expression of several ISG-correlated surface markers between high- and low-IFN score patients and healthy controls. Subsets of CD4+ T cells in high-IFN score patients expressed elevated levels of PD1, CD66a, and OX40, while the majority of cells expressed a similar level as cells in healthy controls. This suggests that only a small subset of CD4+ T cells is activated by localized IFN sources and is involved in SLE pathology. We have further characterized PD1+, OX40+ CD66a+, and SLE-specific memory CD4+ T cells by RNAseq and flow cytometry.

Impaired Cytokine Responses to Epstein-Barr Virus Antigens in Systemic Lupus Erythematosus Patients.

We analyzed cytokine responses against latent and lytic Epstein-Barr virus (EBV) antigens in systemic lupus erythematosus (SLE) patients and healthy controls (HCs) to obtain an overview of the distinctive immune regulatory response in SLE patients and to expand the previously determined impaired EBV-directed T-cell response. The concentrations of 14 cytokines (IL2, IL4, IL5, IL6, IL10, IL12, IL17, IL18, IL1β, IFNγ, TNFα, TNFβ, TGFβ, and GM-CSF) were quantified upon stimulation of whole blood with latent state antigen EBNA1, lytic cycle antigen EBV-EA/D, and the superantigen SEB. To avoid results affected by lack of lymphocytes, we focused on SLE patients with normal levels. Decreased induction of IL12, IFNγ, IL17, and IL6 upon EBNA1 stimulation and that of IFNγ, IL6, TNFβ, IL1β, and GM-CSF upon EBV-EA/D stimulation were detected in SLE patients compared to HCs. IFNγ responses, especially, were shown to be reduced. Induction of several cytokines was furthermore impaired in SLE patients upon SEB stimulation, but no difference was observed in basic levels. Results substantiate the previously proposed impaired regulation of the immune response against latent and lytic cycle EBV infection in SLE patients without lymphopenia. Furthermore, results indicate general dysfunction of leukocytes and their cytokine regulations in SLE patients.

Lupus and Epstein-Barr

Systemic lupus erythematosus (SLE) is a heterogeneous human disease influenced by a complex interplay of necessary, but not individually sufficient, factors. Although many genetic and environmental factors are associated with SLE, this review will focus on the evolving evidence for key Epstein-Barr virus (EBV)-specific roles in SLE, focusing on new experimental studies published during 2009, 2010, and 2011. SLE patients have a dysregulated immune response against EBV. EBV antigens exhibit structural molecular mimicry with common SLE antigens and functional molecular mimicry with critical immune-regulatory components. SLE patients, from a number of unique geographic regions, are shown to have higher rates of EBV seroconversion, especially against early EBV antigens, suggesting frequent viral reactivation. SLE patients also have increased EBV viral loads and impaired EBV-specific CD8 cytotoxic T cells, with impaired cytokine responses to EBV in lupus patients. Irregular cytokine production in plasmacytoid dendritic cells and CD69 CD4 T cells after stimulation with EBV has also been demonstrated. Recent advances demonstrate SLE-specific serologic responses, gene expression, viral load, T-cell responses, humoral fine specificity, and molecular mimicry with EBV, further supporting potential roles for EBV in lupus etiology and pathogenesis.

B cells twist and shout

B cells twist and shout

Antineutrophil autoantibodies and their target antigens in systemic lupus erythematosus.

Various autoantibodies have been identified in sera from patients with systemic lupus erythematosus (SLE) and autoantibodies against neutrophil have been reported. It was suggested that antineutrophil autoantibodies might be involved in the pathogenesis of neutrocytopenia; however, the role of autoantibodies against neutrophil precursors and their specific target autoantigen(s) remained further characterized. The objective was to investigate the target antigens and clinical associations of autoantibodies against neutrophils and neutrophil precursors in patients with SLE. Sera were collected from 92 patients with SLE and renal biopsy proven lupus nephritis. Cell lysates of peripheral neutrophils (as mature neutrophils) from a normal blood donor and white blood cells from a patient with blast crisis of chronic granulocytic leukemia (CGL) (as neutrophil precursors) were used as antigens in Western blot analysis to detect autoantibodies in sera from patients with SLE. The clinical significance of antineutrophil autoantibodies that recognized different antigens were further analysed. Using normal peripheral neutrophils as antigens, two bands could be blotted: 64 kD (33/92, 35.9%) and 50 kD (13/92, 14.1%). The prevalence of anti-64 kD autoantibody in patients with positive rheumatic factor was significantly higher than that in patients without (54.5 versus 18.8%, P < 0.05). Using CGL white cells as antigen, five bands could be blotted: 60 kD (34/92, 37.0%), 50 kD (32/92, 34.8%), 29 kD (27/92, 29.3%), 42 kD (19/92, 20.7%) and 18 kD (16/92, 17.4%). The prevalence of anti-60 kD autoantibody was significantly higher in patients with neutrocytopenia than that in patients without neutrocytopenia (100 versus 48.3%, P < 0.01). The prevalence of anti-29 kD autoantibody was significantly higher in patients with alopecia than that in patients without alopecia (45.8 versus 20.8%, P < 0.05). Furthermore, the prevalences of anti-60 kD, anti-50 kD and anti-42 kD autoantibodies were significantly higher in patients with anti-Ro autoantibody than those in patients without; the prevalences of anti-29 kD and anti-18 kD autoantibodies were significantly higher in patients with anti-Sm autoantibody than those in patients without. We conclude that there are heterogeneous autoantibodies against both neutrophils and their precursors in sera from patients with SLE. Different autoantibodies may have different clinical significance.

The autoimmune response to chromatin antigens in systemic lupus erythematosus: autoantibodies against histone H1 are a highly specific marker for SLE associated with increased disease activity.

This study investigates specificity, sensitivity and concomitant presence of antibodies against histone H1 (H1), nucleosomes (NUC), chromatin (CHR) and dsDNA in patients with systemic lupus erythematosus (SLE), analyses their association with SLE disease activity and characterizes the immunodominant epitope reactivity of anti-H1 antibodies and its relation to SLE disease activity. In a cross-sectional study 394 sera of patients with various rheumatic diseases and healthy subjects were analysed by ELISA for antibodies against H1, NUC, CHR and dsDNA. In addition, a longitudinal analysis was performed that included 121 sequential serum samples derived from 16 SLE patients to assess the relation of these antibodies as well as antibodies to histone H2B to SLE disease activity. To assess epitope reactivity of anti-H1 antibodies overlapping synthetic peptides covering the entire H1 sequence were used. Anti-H1 antibodies yielded a sensitivity of approximately 45% and a specificity of over 98% for SLE, which was comparable to that found for anti-dsDNA antibodies. Anti-CHR and anti-NUC antibodies were of similar sensitivity but slightly (anti-CHR) or considerably (anti-NUC) less specific for SLE (95 and 85%, respectively). The sequential analysis revealed a strong correlation of anti-H1 antibodies with SLE disease activity that was better than the correlation of anti-dsDNA and anti-NUC antibodies, while only weak correlation was found for anti-CHR and anti-H2B antibodies. The immunodominant epitope for anti-HI was localised between amino acids 204 and 218 (pp204-218) and immune reactivity to this epitope also correlated with disease activity. Anti-H1 is a highly specific marker for SLE with a diagnostic value comparable to anti-dsDNA. A positive testing for anti-H1 indicates increased disease activity, as does the appearance of antibodies to its immunodominant epitope pp204-218.

Structural analysis of TCRalpha and beta chains from human T-Cell clones specific for small nuclear ribonucleoprotein polypeptides Sm-D, Sm-B and U1-70 kDa: TCR complementarity determining region 3 usage appears highly conserved.

Systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD) are systemic autoimmune diseases that are characterized by the presence of autoantibodies reactive with U small nuclear RNP (snRNP) autoantigens. Both B and T cells are important in the pathogenesis of the disease, and T- and B-cell immunity against snRNP polypeptides have been shown to be linked in vivo. Currently, several alternative hypotheses for the pathogenesis of these diseases have been proposed. These include loss of tolerance, modified self-antigens, molecular mimicry and nondirected immune activation. To help distinguish between the various models of disease pathogenesis, we have characterized the T-cell receptor (TCR) CDR3 from a large panel of well-characterized human T-cell clones and lines specific for individual snRNP polypeptides. The results presented here reveal highly restricted TCR usage across patients by the snRNP-reactive T cells based on the deduced amino acid sequence of the CDR3 loop. These data support the hypothesis that T-cell responses against self antigens in SLE and MCTD are antigen driven and that there are a limited number of T-cell epitopes present on the snRNP autoantigens.

Increased Level of Soluble HLA Class I Antigens in Systemic Lupus Erythematosus: Correlation with Anti-DNA Antibodies and Leukopenia

The concentration of soluble HLA class I (sHLA-I) was measured by ELISA in serum samples from 30 well-characterised SLE patients at high and low disease activity states and from 100 healthy controls. HLA-A allotypes in the patients were analysed by a PCR-based typing technique. A higher level of sHLA-I was found in SLE patient sera both at high and low disease activity than in controls (P< 0.001). The sHLA-I level was further increased during active disease (P< 0.01). Concentrations of sHLA-I correlated with anti-dsDNA antibodies at high disease activity, but not with disease activity as analysed by a modified SLEDAI. Numbers of leukocytes and lymphocytes, as well as levels of C1q and C3 correlated inversely with sHLA-I concentration. In five serial samples from ten patients the sHLA-I level co-varied with disease activity. Presence of HLA allotype A9 was associated with higher sHLA-I levels in both patients (P< 0.001) and controls (P< 0.001). We conclude that the increased sHLA-I concentration in SLE patients was related to several laboratory parameters reflecting disease activity suggesting that sHLA-I molecules are connected with the disease process. Increased sHLA-I level due to HLA-A allotype was not a disease susceptibility factor for SLE.

Protein microarray characterization of the autoantibody response in systemic lupus erythematosus and related diseases

Systemic lupus erythematosus (SLE) is the prototypical systemic autoimmune disease characterized by production of autoantibodies against a wide range of nuclear self-antigens. These antigens include DNA, histone and several constituents of the RNA splicing complex. Binding of autoantibodies to their specific antigens leads to tissue injury, ultimately resulting in end-organ damage. Individual SLE patients are known to have considerable variability in their specific autoantibody response patterns, and this in part correlates with their clinical manifestations. We have refined protein microarray technology and utilized it to study variation in the autoantibody response between individual SLE patients. We have further extended these studies to other diseases including primary biliary cirrhosis, rheumatoid arthritis, scleroderma, mixed connective tissue disease, multiple sclerosis, diabetes mellitus, and the myositides. Protein microarrays are produced by the application of thousands of proteins and peptides to the surface of a glass microscope slide using a robotic arrayer. We have developed an array containing the major SLE antigens including dsDNA, ssDNA, Sm, Ro, La, histones, and Sm/RNP, along with several other common disease-specific autoantigens. Arrays are probed with serum from disease or control patients, followed by incubation with fluorescently labeled, anti-human secondary antibody. Our array analysis reveals distinct autoantigen response patterns in individual SLE patients. ELISA, immunoprecipitation, and western blot analysis validate our array results. Protein autoantigen arrays represent a powerful tool which may be used to perform comprehensive studies of the breadth of epitope spreading, as well as the fine specificity of the autoantibody response. The large scale of our protein arrays allows us to examine reactivity patterns against a much wider range of autoantigens than was previously possible with more traditional methods. Our ability to distinguish autoantibody specificity patterns using autoantigen microarrays will provide further insight into the role of autoantibodies in disease progression and pathogenesis in subsets of SLE patients with distinct autoantibody responses.

Anti-endothelial cell antibodies in primary antiphospholipid syndrome and SLE: patterns of reactivity with membrane antigens on microvascular and umbilical venous cell membranes.

Although there has been recent emphasis on autoantibodies to epitopes on beta-2-glycoprotein I and prothrombin in the pathogenesis of antiphospholipid syndrome (APS), antibodies other than those directed toward epitopes on phospholipid binding proteins are present. These include those reactive with antigens on platelet membrane glycoproteins, and with vascular endothelial cell membrane. As the pathogenesis of the thrombotic manifestations of APS remains unexplained, further characterization of these antibodies may be informative. We have confirmed anti-endothelial cell binding to a range of cell membrane antigens in systemic lupus erythematosus (SLE) and primary APS. Furthermore, differences in both the pattern of antibody binding and band intensity between human umbilical vein (HUVEC) and human microvascular endothelial cells (HMEC-1) were demonstrated. Of 17 primary APS sera, antibody binding to HUVEC cell membranes was found in nine and to HMEC-1 membranes in seven. Binding at 72-79 kD was confined to HUVEC. In 32 SLE sera, binding to HUVEC and HMEC-1 membranes was detected in 17 and 22 respectively, binding at 135-155 kD being confined to HMEC-1. These results are consistent with the phenotypic variation in endothelial cells of different origins and confirm the frequent presence of autoantibodies reactive with vascular endothelium in both SLE and PAPS. Whether these antibodies could be involved in the pathogenesis of thrombosis, through induction of endothelial cell apoptosis or damage, remains to be determined.

Mechanism of renal damage in systemic autoimmune disorders

Renal involvement is one of the most serious manifestations of systemic autoimmune disorders such as systemic lupus erythematosus (SLE) and mixed cryoglobulinemia (MC). The antigen target of the nephritogenic humoral immune response can be classified as renal specific antigens; circulating antigens that can be trapped in the kidney (for example because of charge); soluble antigens that are bound by circulating antibodies. Antibodies that bind renal specific antigens or circulating antigens trapped in the kidney form in situ immunocomplexes. Antibodies that bind soluble antigens present in the vascular compartment form circulating immunocomplexes that can deposit in glomeruli, in basal membrane or mesangium, as well as in vessel walls, tubular basal membrane and interstitium. Deposition of circulating immune complexes has been suggested to play a major role in inducing renal damage in systemic autoimmune disorders. However, a number of studies indicate that autoantibodies present in SLE sera can bind antigens of glomerular cells or constituents of basal membranes. The aim of the present study was to analyze the specificity of antibodies reactive with renal antigens in SLE and MC. MATERIALS AND METHODS

The effect of intravenous cyclophosphamide pulse on peripheral blood lymphocytes in lupus erythematosus patients

In the present study we investigated the long-term effect of intravenous pulse cyclophosphamide (CY) on lymphocyte surface antigens in systemic lupus erythematosus (SLE) patients. Blood samples derived from 17 lupus erythematosus patients were analysed using two- and three-colour flow cytometry. During the CY therapy, the total number of T lymphocytes (CD3+) was reduced by 31.4%, B lymphocytes (CD19+) by 67.4% and NK cells (CD16+) by 27.4%. Six months after the end of the CY regimen, these values recovered to entry levels. At the onset of the study we observed increased percentages of CD3+ CD25+, CD3+ CD4- CD8-, CD4+ CD29+, CD19+ and CD19+ CD5+ cells. The CY treatment regimen decreased the CD3+ CD25+, CD3+ CD4- CD8-, CD19+ and CD19+ CD5+ cells, but increased the CD3+ CD8+ subpopulation. Taken together, a deficiency of CD8+ T cells associated with CD4+ CD29+ predominance may imply an immune regulatory imbalance leading to abnormal CD4+ cell activation and in consequence to autoimmunity. Depletion of CD19+ cells combined with an enlargement of CD8 cells as a result of CY therapy may reduce the enhanced immune response in SLE patients.

Antibodies to CD45 and other cell membrane antigens in systemic lupus erythematosus.

At some point in their illness, most patients with systemic lupus erythematosus (SLE) develop cold-reactive IgM anti-lymphocyte autoantibodies, which appear to represent a type of natural autoantibody that exhibits a disease-related increase in titer. Increased levels of such autoantibodies are found during flares of SLE disease activity in association with lymphopenia [7, 61], suggesting a causal relationship with T cell depletion and various functional abnormalities of T cells, B cells, and monocytes. Addition of SLE serum or immunoglobulin with anti-lymphocyte autoantibody activity to in vitro cultures of normal peripheral blood mononuclear cells alters their function in ways closely paralleling that of freshly isolated lymphocytes and monocytes from patients with SLE. Mechanisms by which such functional effects could occur in vivo include: (a) elimination of cells by complement-mediated lysis, antibody-dependent, cell-mediated cytotoxicity [15], and/or opsonization; (b) alteration of lymphocyte migration patterns; (c) modulation of surface determinants [63]; (d) agonist, partial agonist, or antagonist effects on cell surface receptors [38, 39, 65]; and (e) interaction with soluble products of activated cells [18]. Thus, autoantibodies to lymphocyte and monocyte surface determinants may constitute one of the pathogenetically significant extrinsic elements that alters cellular immune function in this disorder.

Prevalence and clinical significance of antiphospholipid antibodies to noncardiolipin antigens in systemic lupus erythematosus.

The specificity and immunoglobulin isotype distribution of antiphospholipid (aPL) antibodies have been evaluated in 68 patients with systemic lupus erythematosus (SLE) by ELISA which employed a panel of 7 different PL antigens. A total of 49 patients (72%) were positive for aPL antibodies of different isotypes and directed to one or more PL epitopes. Prevalence of IgG anticardiolipin (aCL, 37%) was similar to that of the other negatively charged PLs phosphatidylserine (PS, 35%), phosphatidylinositol (PI, 35%), phosphatidylglycerol (PG, 35%) and phosphatidic acid (PA, 40%); prevalence reduced to 9-12% and 7-16% respectively for IgM and IgA isotypes to the same antigens. aPL antibodies to the zwitterionic PLs phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were also observed, though their prevalence was lower than that demonstrated for negatively charged PLs. Of the 36 SLE patients who were aCL negative (53%), 17 (25% of all patients and 47% of aCL-negative patients) were positive for aPL antibodies of different isotypes to one or more non-CL epitopes. During a mean follow-up period of 30 months, 10 patients had deep vein thrombosis (DVT) with a total of 21 events. By chi 2 test, a significant correlation was found between DVT and IgG aCL (p = 0.03) and between this event and the presence of lupus anticoagulant (LA) antibody (p = 0.04). However, stronger correlations were demonstrated between DVT and IgA aCL (p = 0.007), IgG anti-PS (p = 0.02), and IgA anti-PC, -PI and -PG (p = 0.02, 0.003 and 0.02, respectively), whereas no correlation was found between thrombotic events and aPL antibodies with PE and PA specificities.(ABSTRACT TRUNCATED AT 250 WORDS)

Anticardiolipin Antibodies: their Relationsip with HLA-DR Antigens in Systemic Lupus Erythematosus

Anticardiolipin Antibodies: their Relationsip with HLA-DR Antigens in Systemic Lupus Erythematosus

Antimyosin antibodies in CNS-lupus.

Anti-myosin antibodies (AMA) in the sera of patients with systemic lupus erythematosus (SLE) and healthy subjects were measured by ELISA. AMA were IgM dominant. The titers of AMA were significantly higher in active SLE than in inactive SLE and healthy subjects. AMA negative SLE patients have significantly lower serum IgM than that in AMA positive subjects. Frequency analysis of HLA antigens in SLE revealed that AMA positivity was associated with HLA-A11, AMA negativity with HLA-B40 and DR2, and those with central nervous system involvement (CNS-SLE) were associated with HLA-B40. The patients with CNS-SLE have low serum IgM, low titer of AMA and HLA-B40.

Detection of Immunoprecipitated Systemic Lupus Erythematosus Antigens by Immunoblot Analysis

When antigens are isolated from staphylococcal protein A immunoprecipitation pellets for analysis by SDS polyacrylamide gel electrophoresis and immunoblotting, severe background problems, due to the presence of antisera and bacterial proteins, can result. We describe a procedure for the analysis of immunoprecipitated systemic lupus erythematosus antigens (e.g., La, Ro, and Sm) which significantly reduces this background while retaining sensitivity with respect to antigen detection. We have adapted a method previously described (MacSween, J.M. and Eastwood, S.L. Methods Enzymol. 1981; 73:459-471) in which lithium diiodosalicylate is used to separate the immunoprecipitated antigen from a covalent antibody-staphylococcal protein A complex. In addition, a modified series of immunoblot incubations was employed, in which antigenic proteins were identified by incubating blots with the antiserum used for the original immunoprecipitation (e.g., La) followed by protein A-biotin and avidin-alkaline phosphatase. Overall, the procedure is straight-forward and may be applicable to other immunoblot systems.

Spontaneous antibody-secreting cells against DNA and common environmental antigens in systemic lupus erythematosus

Cells spontaneously secreting IgG or IgM antibodies to DNA or to common environmental antigens--influenza virus haemagglutinin, adenovirus hexon and mannan from Candida albicans--have been enumerated by ELISA spot in blood from patients with systemic lupus erythematosus (SLE) and normal donors. Mean values were raised for all antigens in the disease, with those for DNA being no greater than for the other antigens. In normal donors, levels of IgM-secreting cells were similar for DNA and the environmental antigens whereas virtually no IgG anti-DNA secreting cells were found. When results were expressed relative to total numbers of IgG or IgM-secreting cells, the differences between the groups disappeared or were greatly reduced in all systems except IgG anti-DNA. These findings are consistent with a requirement for both polyclonal activation and a self-antigen response in the production of IgG autoantibodies in SLE.