Anti-beta2-glycoprotein I antibodies in pediatric systemic lupus erythematosus and antiphospholipid syndrome

OBJECTIVE: To determine whether serum beta2-glycoprotein I antibody (anti-beta2GPI) detection improves identification of pediatric subjects at risk for antiphospholipid syndrome (APS). METHODS: Serum antiphospholipid antibodies (aPL) were identified by anticardiolipin enzyme-linked immunosorbent assay (ELISA), lupus anticoagulant assays, and syphilis screening in children with primary APS, systemic lupus erythematosus (SLE), or SLE plus APS. Anti-beta2GPI level and isotype were determined by beta2GPI ELISA and correlated with clinical manifestations and other aPL assays. RESULTS: One hundred-ten subjects under 22 years of age and of mixed ethnicity were evaluated. Fifty-seven had SLE (including 14 with APS), 25 had primary APS, 16 had SLE-like APS, 6 were healthy children with aPL detected incidentally, 4 had other rheumatic diseases and 2 had other conditions. Anti-beta2GPI were detected in 48% of SLE subjects and did not improve aPL detection over standard tests. Anti-beta2GPI were associated with stroke (P = 0.014), but not with other APS manifestations, and were rarely detected in primary APS. Among subjects with APS manifesting as chronic thrombocytopenia, anti-beta(2)GPI distinguished subjects with SLE from those with primary APS. CONCLUSIONS: With the exception of stroke, anti-beta2GPI detection does not improve identification of pediatric APS over that of traditional aPL assays. Anti-beta2GPI are rare in pediatric primary APS, but may predict evolution of chronic thrombocytopenia to SLE.     

IgG anti-beta2-glycoprotein I antibodies in adult patients with systemic lupus erythematosus: prevalence and diagnostic value for the antiphospholipid syndrome

OBJECTIVE: To investigate the prevalence of serum anti-beta2-glycoprotein I (anti-beta2-GPI) antibodies and other antiphospholipid antibodies (aPL) in patients with systemic lupus erythematosus (SLE). To study their diagnostic value for the antiphospholipid syndrome (APS). METHODS: Anti-beta2-GPI and IgG anticardiolipin (aCL) were determined in sera from 102 consecutive patients with SLE using ELISA. Serum and plasma tests were also done for lupus anticoagulant (LAC), syphilis, and antibodies to dsDNA. Clinical and laboratory features of APS were observed. RESULTS: Prevalences were 23.5% for aCL and 18.6% for anti-beta2-GPI. Correlations between the presence of aCL and anti-beta2-GPI and between their titers were statistically significant (p<0.0001). No associations were found between anti-beta2-GPI and disease activity criteria (SLEDAI, ECLAM, dsDNA). Anti-beta2-GPI were significantly associated with LAC (p = 0.005), APS (p = 0.005), and a high aCL titer (aCL > 5 SD; p< or =0.001). LAC was the best diagnostic criterion for APS. CONCLUSION: These data suggest that determination of anti-beta2-GPI in addition to aCL and LAC is unlikely to improve the diagnosis of APS in patients with SLE.     

Prevalence of beta 2-glycoprotein I antibody in systemic lupus erythematosus patients with beta 2-glycoprotein I dependent antiphospholipid antibodies.

OBJECTIVE--To investigate whether beta 2-glycoprotein I antibody (aGPI) exists in sera that are positive for antiphospholipid antibodies (aPL). METHODS--Thirty six patients with systemic lupus erythematosus (SLE) and 20 healthy volunteers were recruited. GPI independent and dependent aPL (anticardiolipin (aCL), antiphosphatidylserine, antiphosphatidylinositol, antiphosphatidic acid) were measured using a conventional enzyme linked immunosorbent assay (ELISA). aGPI was measured by an ELISA using a gamma irradiated plate coated with purified GPI. RESULTS--Twenty of 36 SLE patients were positive for at least one of the GPI-dependent aPL. Five of these 20 were also positive for aGPI. Another five of the 20 showed low GPI dependency aCL antibodies; however, three of these patients required GPI for binding to phosphatidylserine, phosphatidylinositol, or both. CONCLUSION--We confirmed the existence of aGPI in patients with true GPI dependent aPL. From these results, we recommend the use of a gamma irradiated plate with GPI as antigen for the detection of true GPI dependent aPL or aGPI.     

Immune responses to native beta(2)-glycoprotein I in patients with systemic lupus erythematosus and the antiphospholipid syndrome

OBJECTIVE: To identify HLA class II associations with anti beta(2)-glycoprotein I (beta2GPI) antibodies in a cohort of Caucasian patients with systemic lupus erythematosus (SLE) and to determine whether these HLA genotypes act as restriction elements for lymphocyte proliferation to native human beta2GPI in vitro. METHODS: Anti-beta2GPI antibodies were detected in patient sera using enzyme-linked immunosorbent assays (ELISAs). HLA class II alleles (DRB1, DQB1) were determined by polymerase chain reaction-based DNA genotyping. In vitro peripheral blood mononuclear cell (PBMC) responses to native human beta2GPI were measured in a 7-day proliferation assay. RESULTS: We identified three groups of Caucasian SLE patients using these ELISAs. In group 1, 16 out of 18 SLE patients (89%) with anti-beta2GPI antibodies were positive for HLA-DRB1*0401/4/8, DR11 or DRB1*1302 (P=0.001 vs controls) compared with 23 out of 53 patients (43%) in group 2 with anti-cardiolipin antibodies only, 57 out of 151 patients (38%) in group 3 (SLE patients without anticardiolipin antibodies) and 109 out of 225 controls (48%). Fourteen patients with anti-beta2GPI antibodies had greater median stimulation indices to beta2GPI in vitro compared with the 15 controls studied (P=0.04). CONCLUSION: The HLA class II and PBMC proliferation data suggest that beta2GPI may be both a T- and B-cell autoantigen in SLE.     

Specificity and sensitivity of anti-beta2-glycoprotein I as compared with anticardiolipin antibody and lupus anticoagulant in Thai systemic lupus erythematosus patients with clinical features of antiphospholipid syndrome

Antibodies to beta(2)-glycoprotein I (anti-beta(2)-GPI) have been reported to have stronger association with clinical antiphospholipid syndrome (APS) than anticardiolipin antibodies (aCL) and lupus anticoagulant (LAC). We investigated the sensitivity and specificity of ELISA for anti-beta(2)-GPI in Thai systemic lupus erythematosus (SLE) patients with clinical features of APS and compared the results with IgG/IgM aCL and LAC to find the test with the best association. The hospital records of 151 Thai SLE patients whose sera had been sent for either IgG/IgM anticardiolipin antibodies or lupus anticoagulant testing were reviewed. Sera of patients either without complete clinical records or those with APS-related manifestations other than vascular thrombosis and pregnancy morbidity (according to the international consensus statement on preliminary classification criteria for definite APS) were excluded. For the remaining subjects (112 patients), their sera were tested for anti-beta(2)-GPI antibody, IgG and IgM anticardiolipin, and lupus anticoagulant. The sensitivity and specificity of each method were compared by using the chi-square test. Among the 112 (74.2%) SLE patients in the study, 35 (31.3%) presented with preliminary clinical criteria for APS (i.e., vascular thrombosis and pregnancy morbidity) whereas 77 (68.7%) did not. The sensitivity and specificity of anti-beta(2)-GPI determination were 57.1 and 79.2%, respectively, whereas those of IgG aCL were 25.7 and 94.8%, of IgM aCL were 5.7 and 98.7%, and of LAC were 44.8 and 77.3%, respectively. The accuracy of the four tests showed similar association with clinical APS (accuracy of test = 72.3, 73.2, 69.6, and 68.3%, respectively). Concerning the sensitivity, specificity, and difficulty of the methods, the combination of anti-beta(2)-GPI and IgG aCL tests was the best for the diagnosis of APS in Thai SLE patients.     

Hypocomplementemia in systemic lupus erythematosus and primary antiphospholipid syndrome: prevalence and clinical significance in 667 patients

The objective of the study was to analyse the prevalence and clinical significance of hypocomplementemia in a large series of patients diagnosed either with systemic lupus erythematosus (SLE) or with primary antiphospholipid syndrome (APS) and its association with the main clinical, hematological and immunological features of these diseases. Between 1992 and 2003, complement determinations (C3 and C4 levels, CH50 activity) were performed in 597 consecutive patients diagnosed with SLE (530 women and 67 men, mean age 32.6 years) and 70 with primary APS (57 women and 13 men, mean age 38.7) visited in our department. Complement determinations are routinely made at the first visit of patients and yearly during the follow-up. SLE and primary APS were diagnosed according to current classification criteria. Hypocomplementemia was detected in 371 (62%) of SLE patients. Compared with patients with normal complement values, those with hypocomplementemia showed a higher prevalence of female gender (P < 0.001), fever (P = 0.021), nephropathy (P < 0.001), cutaneous vasculitis (P = 0.023), positive anti-dsDNA antibodies (P = 0.012) and cryoglobulinemia (P < 0.001). In addition, patients with hypocomplementemia showed a higher prevalence of APS-related features such as hemolytic anemia (P = 0.001) and antiphospholipid antibodies (P < 0.001). Hypocomplementemia was prospectively related to accumulated hospitalization in SLE patients but not with the accumulated number of lupus flares or with the survival after follow-up of five years. In contrast, 33 (47%) patients with primary APS presented low complement values, which were associated with a higher prevalence of livedo reticularis (P = 0.022), thrombocytopenia (P = 0.004), lupus anticoagulant (P = 0.013), positive IgM-aCL (P = 0.039), positive ANA (P = 0.002) and anti-dsDNA (P = 0.046). The diagnostic value of hypocomplementemia in patients with SLE is based on the association with disease activity, immune-complex mediated manifestations (glomerulonephritis, cryoglobulinemia) and APS-related features (livedo reticularis, hemolytic anemia and aPL). Hypocomplementemia was found in nearly half of patients with primary APS, and was associated with some APS features (livedo reticularis, thrombocytopenia, aPL) but also with SLE-related immunological markers (ANA and anti-dsDNA), identifying a subset of patients with primary APS with a higher risk of evolving to SLE. These results clearly support the routine determination of complement factors in the clinical follow-up of patients with SLE and primary APS.     

Antiphospholipid syndrome nephropathy in patients with systemic lupus erythematosus and antiphospholipid antibodies: prevalence, clinical associations, and long-term outcome

OBJECTIVE: To evaluate the prevalence, clinical associations, and outcome of antiphospholipid syndrome (APS) nephropathy in patients with systemic lupus erythematosus (SLE) and antiphospholipid antibodies (aPL) and in SLE patients without aPL. METHODS: Kidney biopsy specimens obtained from 81 patients with aPL (18 of whom had APS) and 70 patients without aPL were retrospectively examined for the presence of APS nephropathy. Clinical and serologic data obtained at the time of kidney biopsy and during a mean followup of 7 years were recorded. In cases for which serial kidney biopsy specimens were available, the evolution of APS nephropathy was examined. RESULTS: APS nephropathy existed in 39.5% of patients with aPL, compared with only 4.3% of patients without aPL. APS nephropathy was associated with both lupus anticoagulant and anticardiolipin antibodies. Among aPL-positive SLE patients, APS nephropathy was found in two-thirds of those with APS and in one-third of those without APS. A strong association between APS nephropathy and the presence of arterial thrombosis and livedo reticularis was noted. Patients with APS nephropathy had a higher frequency of hypertension and elevated serum creatinine levels at the time of kidney biopsy but did not have a higher frequency of renal insufficiency, end-stage renal disease, or death at the end of followup. Serial kidney biopsy specimens were available from 11 patients and showed progression of APS nephropathy lesions. During followup, manifestations of APS (especially arterial thromboses) developed more frequently in the SLE/non-APS patients with APS nephropathy than in those without APS nephropathy. CONCLUSION: Among patients with SLE, APS nephropathy occurs almost exclusively in those with aPL, suggesting an important role of aPL in the pathogenesis of APS nephropathy. Patients with APS nephropathy develop hypertension, raised serum creatinine levels, and progression of histologic lesions, all of which are associated with a poor renal outcome. Manifestations of APS also tend to develop in these patients. APS nephropathy should be included in the APS classification criteria, and the use of appropriate anticoagulant therapy should be tested.     

抗β2-糖蛋白Ⅰ抗体在系统性红斑狼疮中的临床意义

目的了解抗!2-糖蛋白Ⅰ抗体(抗!2-GPⅠ抗体)与系统性红斑狼疮(SLE)临床特点的关系及在其诊断中的价值。方法采用酶联免疫吸附试验(ELISA)检测112例SLE患者、40例类风湿关节炎(RA)患者、30例干燥综合征(SS)患者和40名正常人血清中的抗!2-GPⅠ抗体水平。同时,测定患者血清中的抗心磷脂抗体(ACL)等指标,并分析其与患者的临床特点(如:血栓、流产)的关系及其临床意义。统计学分析采用t检验、!2检验和Spearman检验。结果抗!2-GPⅠ抗体在SLE中敏感性为21.4%(24/112),特异性为88.6%,在RA和SS敏感性分别为15.0%(6/40)和6.7%(2/30),40名正常对照均为阴性。抗!2-GPⅠ抗体与血栓形成密切相关(P<0.01),与ACL-IgG和IgM型水平呈正相关(r=0.479,P=-0.032;r=0.400,P=0.045)。抗!2-GPⅠ抗体与其他临床及实验室指标无明显相关性。结论抗!2-GPⅠ抗体在SLE中具有一定的敏感性,且可能在SLE的血栓形成中发挥作用,联合检测ACL与抗!2-GPⅠ抗体能够辅助诊断SLE伴血栓形成。     

Anti-beta2-glycoprotein I autoantibodies, in vitro thrombin generation, and the antiphospholipid syndrome

OBJECTIVE: Thrombin plays a pivotal role in the regulation of hemostasis. We examined the effect of antiphospholipid (aPL) antibodies, in particular those with specificity for beta2-glycoprotein I (beta2-GPI), on in vitro thrombin generation, and examined the association with clinical manifestations of the antiphospholipid syndrome (APS). METHODS: We studied plasma samples from 59 patients with aPL antibodies determined by the presence of either elevated anticardiolipin (aCL) antibodies or lupus anticoagulant (LAC). Direct antibody binding of IgG, IgM, and IgA to beta2-GPI and prothrombin (PT) was determined by ELISA. Affinity purification of total IgG and IgG anti-B2-GPI antibodies was performed using staphylococcal protein A and phospholipid liposomes. A chromogenic assay was used to determine the effect of plasma samples and purified autoantibodies on in vitro thrombin generation. RESULTS: Thirty-three of 59 (56%) plasma samples inhibited in vitro generation of thrombin and 7/59 (12%) accelerated thrombin formation. There was a strong negative correlation between thrombin generation and IgG aCL (r = -0.72, p < 0.001) and IgG anti-beta2-GPI (r = -0.71, p < 0.001) antibody levels, and a weaker correlation with LAC (r = -0.46, p = 0.001). This association was not found with anti-PT antibodies and could not be attributed to concurrent therapy with warfarin. Additional experiments with affinity purified IgG antibodies indicated a dose dependent inhibition of thrombin generation, which was restricted to anti-beta2-GPI antibodies. Patients with a history of core clinical manifestations of the APS [venous and arterial thrombosis, recurrent (> or = 2) fetal loss] had significantly greater inhibition of in vitro thrombin generation (mean +/- SEM Z score: -3.38 +/- 0.51 vs -1.42 +/- 0.56; p = 0.01) and higher levels of IgG aCL (mean +/- SEM Z score: 8.39 +/- 1.12 vs 5.39 +/- 0.88; p = 0.04) and IgG anti-beta2-GPI antibodies (mean +/- SEM Z score: 4.49 +/- 0.69 vs 2.26 +/- 0.54; p = 0.01). Odds ratios for these variables and clinical manifestations of the APS were 5.43, 4.17, and 3.28, respectively. CONCLUSION: aPL antibodies may accelerate or inhibit the rate of in vitro thrombin formation. The predominant effect is inhibition that is restricted to IgG anti-beta2-GPI antibodies and it is strongly associated with clinical manifestations of the APS.     

Anti-beta 2-glycoprotein I antibodies: a useful marker for the antiphospholipid syndrome

We studied anti-beta 2-glycoprotein I antibodies (a beta 2GPI) in autoimmune disease patients to evaluate their relationship to clinical findings. Seventy-nine systemic lupus erythematosus (SLE) patients [44 with antiphospholipid antibodies (aPL)], 21 with primary antiphospholipid syndrome (APS), eight asymptomatic individuals with aPL and 60 controls were studied. Sixteen SLE patients (14 with aPL and two without aPL) and six with primary APS had a beta 2GPI. A significant relationship was found between a beta 2GPI and aPL (P < 0.01). In SLE, a significant correlation was found between previous thrombosis or thrombocytopenia and a beta 2GPI or a beta 2GPI + aPL, but not between fetal losses and a beta 2GPI. These data suggest that a beta 2GPI may be useful in the study of APS.      

Cardiac dysfunction in patients with systemic lupus erythematosus and antiphospholipid syndrome

OBJECTIVE: To comparatively assess the parameters of systolic and diastolic cardiac function in patients with systemic lupus erythematosus (SLE) and antiphospholipid syndrome (APS). METHODS: Consecutive patients (n=74) who were free of cardiovascular symptoms were divided into four groups: (1) SLE (n=23); (2) SLE with antiphospholipid antibodies (aPL; n=18); (3) SLE with APS (n=20); and (4) primary antiphospholipid syndrome (PAPS; n=13). Pulsed, continuous, colour Doppler echocardiography, and M-mode and B-mode studies were performed. RESULTS: Left ventricular end diastolic and end systolic dimensions were higher in SLE as compared with patients with PAPS (p=0.022 and 0.022, respectively), with a trend towards a lower fractional shortening in SLE (p=0.07), suggesting systolic dysfunction. Parameters of diastolic function were more impaired in patients with APS, reflected by lower left ventricular and right ventricular E wave to A wave (E:A) ratios in patients with APS (groups 3, 4) compared with those without APS (groups 1, 2; 1.15 (0.40) v 1.49 (0.43), p=0.001 and 1.19 (0.31) v 1.49 (0.41), p=0.001, respectively) and a more prolonged left ventricular isovolumic relaxation time (IVRT; 94.2 (24.6) v 84.4 (17) ms, respectively, p=0.055). Patients with APS were older than those without APS (47.12 (14.86) v 34.29 (12.6), p=0.0001). Patients with SLE were younger than those with PAPS (38.19 (14.68) v 48.53 (13.97), p=0.023). CONCLUSION: Abnormal echocardiographic findings were detected frequently in asymptomatic patients with SLE or PAPS. Although patients with SLE were younger, left ventricular systolic function was more impaired in patients with SLE compared with those with PAPS, whereas left ventricular and right ventricular diastolic function, as reflected by IVRT and E:A ratios, were significantly more impaired in patients with APS.     

Stroke in patients with systemic lupus erythematosus and antiphospholipid antibody syndrome

Opinion statement  Primary prevention of strokes in patients with antiphospholipid antibodies (APLs) with or without systemic lupus erythematosus (SLE) is not well known. The same applies to patients with SLE and valvular heart disease. The decision should be made on an individual basis until further studies become available. Special consideration for preventive antithrombotic treatment should be given to patients with persistent high titers of immunoglobulin G APLs, which require protein cofactor for detection, presence of lupus anticoagulant, or left-sided cardiac valve lesions. High-level oral anticoagulation with warfarin is still the preferred treatment for secondary prevention of strokes in patients with antiphospholipid antibody syndrome (APS) with or without SLE or with cardiac valvular lesions. Immunosuppression should only be used in patients with active SLE disease. There is no evidence so far to support its use in patients with primary APS. Advances in identifying unique APL features that are associated with increased risk for thrombosis will hopefully allow a more rational treatment for primary and secondary prevention of strokes in these patients in the near future.     

Stroke in patients with systemic lupus erythematosus and antiphospholipid antibody syndrome

Opinion statement Primary prevention of strokes in patients with antiphospholipid antibodies (APLs) with or without systemic lupus erythematosus (SLE) is not well known. The same applies to patients with SLE and valvular heart disease. The decision should be made on an individual basis until further studies become available. Special consideration for preventive antithrombotic treatment should be given to patients with persistent high titers of immunoglobulin G APLs, which require protein cofactor for detection, presence of lupus anticoagulant, or left-sided cardiac valve lesions. High-level oral anticoagulation with warfarin is still the preferred treatment for secondary prevention of strokes in patients with antiphospholipid antibody syndrome (APS) with or without SLE or with cardiac valvular lesions. Immunosuppression should only be used in patients with active SLE disease. There is no evidence so far to support its use in patients with primary APS. Advances in identifying unique APL features that are associated with increased risk for thrombosis will hopefully allow a more rational treatment for primary and secondary prevention of strokes in these patients in the near future.     

Antibodies to β2-glycoprotein I and clinical manifestations in patients with systemic lupus erythematosus

Objective. To investigate whether anticardiolipin antibodies (aCL) in patients with systemic lupus erythematosus (SLE) bind to β₂-glycoprotein I (β₂GPI), and to search for a relationship between the presence of IgG and/or IgM anti-β₂GPI antibody and clinical manifestations in SLE patients. Methods. IgG and IgM anti-β₂GPI in 308 Japanese SLE patients were measured using phospholipid-independent enzyme immunoassays. Relationships to clinical histories and to various laboratory data were examined. Results. The values of anti-β₂GPI and aCL, as measured by conventional enzyme immunoassay, showed a strong correlation, but the anti-β₂GPI assay was more useful in distinguishing β₂GPI-dependent aCL from β₂GPI-independent aCL. The presence of IgG anti-β₂GPI was associated with an increased frequency of a history of thrombosis. Comparisons of various laboratory data suggested that the titer of anti-β₂GPI may fluctuate with disease activity. Conclusion. The results suggest that pathogenic aCL is directed against structurally altered β₂GPI and that enzyme immunoassay for anti-β₂GPI may prove useful in evaluating the risk of thrombosis and monitoring the clinical course in patients with SLE.     

Atherogenic oxidized low-density lipoprotein/beta2-glycoprotein I (oxLDL/beta2GPI) complexes in patients with systemic lupus erythematosus and antiphospholipid syndrome

Oxidized low-density lipoprotein (oxLDL) interacts in vitro with beta2-glycoprotein I (beta2GPI) via LDL-derived specific ligands forming oxLDL/beta2GPI complexes. Circulating oxLDL/beta2GPI complexes have been demonstrated in patients with systemic lupus erythematosus (SLE) and antiphospholipid syndrome (APS). Autoimmune vascular inflammation and oxidative stress contribute to oxLDL/beta2GPI complex formation. Immunohistochemical staining of atherosclerotic lesions suggest that these complexes are formed in the arterial wall and released into circulation. The demonstration of antibodies to oxLDL/beta2GPI complexes indicates that these complexes are immunogenic, and the coexistence of complexes and antibodies suggest an active pro-thrombotic/pro-atherogenic role in the development of autoimmune vascular complications. Circulating oxLDL/beta2GPI complexes can be measured by ELISA using a monoclonal antibody specific to complexed human beta2GPI to capture beta2GPI bound to oxLDL. An enzyme-conjugated monoclonal antibody to human Apo B 100 allows the specific detection of oxLDL/beta2GPI complexes. OxLDL/beta2GPI complexes were common in SLE and APS patients suggesting an underlying process of inflammation and oxidation. Using oxLDL/beta2GPI complexes as capture antigen, antibodies to oxLDL/beta2GPI can be measured by ELISA. Serum levels of IgG anti-oxLDL/beta2GPI antibodies were significantly higher in SLE patients with APS compared to SLE controls without APS. Further, high titers of these IgG antibodies were observed in APS patients with a history of arterial thrombosis. The presence of circulating oxLDL/beta2GPI complexes and IgG antibodies to these complexes indicates significant vascular injury and oxidative stress as well as an active role in autoimmune-mediated atherothrombosis.     

Antibodies to high-density lipoprotein and beta2-glycoprotein I are inversely correlated with paraoxonase activity in systemic lupus erythematosus and primary antiphospholipid syndrome

OBJECTIVE: To determine the prevalence of anti-high-density lipoprotein (anti-HDL) antibodies and to establish a possible relationship between anti-HDL, anticardiolipin antibodies (aCL), anti-beta(2)-glycoprotein I (anti-beta(2)GPI), and paraoxonase (PON) activity in patients with systemic lupus erythematosus (SLE) and primary antiphospholipid syndrome (APS). METHODS: Thirty-two patients with SLE and 36 with primary APS were enrolled in a cross-sectional study. Twenty age- and sex-matched healthy subjects were used as controls. Serum levels of IgG and IgM aCL, anti-beta(2)GPI, and antiprothrombin antibodies and IgG anti-HDL were measured by enzyme-linked immunosorbent assay. Total cholesterol, HDL cholesterol, HDL(2), and HDL(3) were determined by standard enzymatic techniques. PON activity was assessed by quantification of nitrophenol formation, and total antioxidant capacity (TAC) by chemiluminescence. RESULTS: Levels of total HDL, HDL(2), and HDL(3) were reduced in patients with SLE compared with controls (mean +/- SD 0.51 +/- 0.3, 0.37 +/- 0.3, and 0.14 +/- 0.1 mmoles/liter, respectively, versus 1.42 +/- 0.9, 1.01 +/- 0.7, and 0.40 +/- 0.2). Patients with SLE and primary APS had higher titers of anti-HDL antibodies and lower PON activity than controls. In the SLE population, PON activity was inversely correlated with IgG anti-HDL titers (r = -0.48, P = 0.005) whereas in the primary APS population, IgG anti-beta(2)GPI was the only independent predictor of PON activity (r = -0.483, P = 0.003). In the SLE group, anti-HDL was inversely correlated with TAC (r = -0.40, P < 0.02), and PON activity was positively correlated with TAC (r = 0.43, P < 0.02). CONCLUSION: IgG anti-HDL and IgG anti-beta(2)GPI antibodies are associated with reduced PON activity in patients with SLE and primary APS. Since the physiologic role of PON is to prevent low-density lipoprotein oxidation with its attendant atherogenic effects, the reported interactions may be relevant to the development of atherosclerosis in SLE and primary APS.