Use of a new fluorescence immunoassay to detect anti-dsDNA antibodies is more correlated with disease activity and complement than the ELISA method in SLE patients

To determine whether the serum levels of anti-double strand DNA (anti-dsDNA) autoantibodies detected using a newly developed fluorescence immunoassay (FIA) in patients with systemic lupus erythematosus (SLE) correlated more with clinical parameters, such as SLE disease activity index (SLEDAI), complement and the occurrence of nephritis when compared with traditional enzyme-linked immunosorbent assay (ELISA), we prospectively collected 124 serum samples from 31 patients who had juvenile-onset SLE and were regularly monitored every 2 months at our outpatient clinic. At every visit, clinical manifestations and laboratory parameters were assessed and the SLEDAI was determined. Correlation analyses between the two different measurements of anti-dsDNA antibodies and SLEDAI, serum complement levels and the occurrence of nephritis were performed. The results showed that anti-dsDNA autoantibodies detected using both ELISA and FIA significantly correlated with SLEDAI, and significantly and inversely correlated with the serum levels of C3 and C4. FIA had significantly higher correlation with SLEDAI and C4 than did ELISA. The mean values of anti-dsDNA antibodies detected using FIA in patients with nephritis were significantly higher than in those without nephritis. In contrast, the values of anti-dsDNA antibodies detected using ELISA did not show significant differences between these two groups. We conclude that FIA had better correlation with SLEDAI, C4 and the occurrence of nephritis, and comparable correlations with C3 that were similar to the results found using ELISA. Thus, it is worthwhile developing the FIA method for clinical evaluation of disease activity in SLE patients.     

Autoantibodies against nuclear pore complexes are associated with more active and severe liver disease in primary biliary cirrhosis

BACKGROUND/AIMS: Antibodies against nuclear pore complexes (NPCs) have been detected in primary biliary cirrhosis (PBC), but their clinical relevance is still unsettled. METHODS: We tested sera from 171 consecutive PBC patients and 230 control subjects (149 with autoimmune or viral liver diseases, 28 with systemic lupus erythematosus, and 53 healthy) by immunoblotting for antibodies against purified human NPCs. RESULTS: Antibodies to NPCs were detected in 27% of the patients with PBC, were highly specific (97%), and were not associated with antimitochondrial antibodies. Their prevalence was higher in symptomatic patients (36 vs. 16%, P < 0.01) and was associated (P < 0.001) with more severe disease, as assessed by the presence of cirrhosis or its complications (13% prevalence in patients without cirrhosis, 31% in uncomplicated, and 54% in complicated cirrhosis), or by the application of the Mayo prognostic model (12% in the lowest, 21% in the median, 47% in the highest score tertile). Positive patients had higher levels of serum bilirubin (2.2 +/- 3.7 vs. 1.0 +/- 1.1 mg/dl, P < 0.01) and more marked inflammatory infiltrates on liver biopsy (P < 0.05). CONCLUSIONS: Autoantibodies to NPCs are more prevalent in PBC patients than in controls and are strongly associated with more active and severe disease.     

Inflammatory bowel disease associated circulating immune complexes

Circulating immune complexes have been detected in patients with inflammatory bowel disease (IBD). To determine if these complexes are related specificially to IBD or more generally to loss of intestinal mucosal integrity, we compared circulating immune complex levels in the sera of 86 IBD patients, nine pseudomembranous and nine bacterial colitis patients, and 42 healthy controls. Immune complexes were measured by a Raji cell radioimmunoassay. Raji detectable circulating immune complex levels were significantly higher in the IBD group than in the healthy controls (P<0·001). Circulating immune complex levels in the pseudomembranous-bacterial colitis group and the healthy controls were essentially identical. While nearly 20% of the IBD patients (16 of 86) had abnormally high levels, none of the patients with the other forms of intestinal inflammation (0 of 18) had abnormal levels. These data suggest that the circulating immune complexes present in inflammatory bowel disease patients are related to the IBD process rather than to non-specific mucosal cell (barrier) damage. Patients with intestinal inflammation and normal peripheral immune complex levels also had normal mesenteric vein levels. These data suggest that lack of formation, rather than more efficient hepatic reticuloendothelial clearance, was primarily responsible for the absence of detectable complexes in Raji negative individuals. Circulating immune complex levels did not correlate with type, location, severity, or extraintestinal manifestations of inflammatory bowel disease. The absence of Raji detectable circulating immune complexes in the majority of patients, even in those with extraintestinal manifestations, raises serious doubts about the pathogenic significance of such complexes. Nevertheless, as the circulating immune complexes appear to be disease related, they may be used to isolate and identify disease specific antigen(s) of possible aetiological importance.     

Serum amyloid P component-DNA complexes are decreased in systemic lupus erythematosus. inverse association with anti-dsDNA antibodies

OBJECTIVE: To study serum levels of serum amyloid P component (SAP) and SAP-DNA complexes in a population-based cohort of patients with systemic lupus erythematosus (SLE). METHODS: The study population comprised 82 unselected patients of predominantly Scandinavian ancestry with SLE according to current classification criteria. Serum samples were collected at baseline and serially for up to 2 years. SAP component and SAP-DNA complexes were measured by ELISA. Associations between SAP-DNA and clinical manifestations or serological findings were analyzed. Ninety healthy, age-matched blood donors served as controls. RESULTS: SLE patients had normal serum concentrations of SAP, whereas SAP-DNA complexes were decreased. Two-thirds of the SLE patients tested persistently SAP-DNA complex-negative. There was no relationship between the occurrence of SAP-DNA complexes and clinical manifestations. SAP-DNA-negative patients tended to have lower leukocyte counts and complement C3 levels, and higher erythrocyte sedimentation rates and C3d levels versus SAP-DNA-positive patients. There was an inverse association between the occurrence of anti-double-stranded DNA (anti-dsDNA) antibodies and SAP-DNA complexes. Co-occurrence of SAP-DNA complexes and anti-dsDNA antibodies was demonstrated in only one SLE patient, implying that 81/82 patients were discordant for the presence of anti-dsDNA antibodies and SAP-DNA complexes. CONCLUSION: The decreased level of SAP-DNA complexes in SLE patients and the inverse relationship between these complexes and anti-dsDNA antibody supports the concept that SAP component is implicated in the clearance of cell nuclear debris.     

A simple method for detecting HIV antibodies hidden in circulating immune complexes

A method previously used for studying the specificity of antibody components of circulating immune complexes in different diseases has been applied to analyse circulating immune complexes in HIV-infected patients. Antibodies against HIV antigens hidden in circulating immune complexes were studied in 14 sera from 13 patients with asymptomatic HIV infection (group 1) and in 11 sera from seven patients with HIV symptoms (group 2). HIV antigen-coated wells from the Vironostika kit as well as core and envelope antigen-coated beads from the Abbott confirmatory kit were used as solid-phase antigen. Using the Vironostika plates, HIV antibodies were demonstrated in circulating immune complexes in three and five sera in groups 1 and 2, respectively. Anti-core antibodies hidden in circulating immune complexes were present in three out of eight and two out of nine sera, respectively, in groups 1 and 2, whereas anti-envelope antibodies were present in circulating immune complexes in one out of eight and six out of nine sera in the same groups. These findings demonstrate that not only core-anti-core but also envelope-anti-envelope immune complexes are present in the sera of HIV infected patients.     

Autoantibodies to IgG/HLA class II complexes are associated with rheumatoid arthritis susceptibility

Specific HLA class II alleles are strongly associated with susceptibility to rheumatoid arthritis (RA); however, how HLA class II regulates susceptibility to RA has remained unclear. Recently, we found a unique function of HLA class II molecules: their ability to aberrantly transport cellular misfolded proteins to the cell surface without processing to peptides. Rheumatoid factor (RF) is an autoantibody that binds to denatured IgG or Fc fragments of IgG and is detected in 70–80% of RA patients but also in patients with other diseases. Here, we report that intact IgG heavy chain (IgGH) is transported to the cell surface by HLA class II via association with the peptide-binding groove and that IgGH/HLA class II complexes are specifically recognized by autoantibodies in RF-positive sera from RA patients. In contrast, autoantibodies in RF-positive sera from non-RA individuals did not bind to IgGH/HLA class II complexes. Of note, a strong correlation between autoantibody binding to IgG complexed with certain HLA-DR alleles and the odds ratio for that allele’s association with RA was observed (r = 0.81; P = 4.6 × 10⁻⁵). Our findings suggest that IgGH complexed with certain HLA class II alleles is a target for autoantibodies in RA, which might explain why these HLA class II alleles confer susceptibility to RA.Autoantibodies are produced in most autoimmune diseases and are frequently used in their diagnosis. Rheumatoid factor (RF) is an IgM autoantibody that binds to denatured IgG or Fc fragments of IgG and is detected in about 80% of RA patients but also in 5–10% of healthy individuals, as well as in other autoimmune diseases (1). However, the natural antigens that are recognized by RF are unknown, partly because such denatured IgG does not exist in physiological situations. Specific HLA class II alleles are strongly associated with susceptibility to many autoimmune diseases (2). Because peptide repertoires presented on different HLA class II alleles differ (3, 4), it has been proposed that specific peptide–HLA class II combinations affect T-cell development and/or tolerance, which may confer susceptibility or resistance to autoimmune diseases (5). A recent report of a large-scale genetic study indicates that several amino acid residues within the HLA-DR peptide-binding groove determine susceptibility to rheumatoid arthritis (RA) (6). However, it has remained enigmatic for decades how specific HLA class II molecules control the immune response in autoimmune diseases (7).We recently found that misfolded HLA class I molecules are present on the cell surface of HLA class II-expressing cells. Unexpectedly, we discovered that these misfolded HLA class I molecules were transported to the cell surface by association with the peptide-binding groove of HLA class II molecules (8). Indeed, direct association between HLA class II molecules and misfolded HLA class I molecules was detected in HLA class II-expressing B-cell lines. Furthermore, the intact misfolded proteins transported to the cell surface by HLA class II molecules efficiently stimulated antigen-specific B cells (8). Accordingly, we hypothesized that misfolded proteins aberrantly transported to the cell surface by HLA class II molecules might be targets for autoantibodies detected in autoimmune diseases.     

Tetramolecular immune complexes are more efficient than IVIg to prevent antibody-dependent in vitro and in vivo phagocytosis of blood cells

Intravenous immunoglobulins (IVIg) have immunomodulatory effects in vivo and are widely used in the treatment of autoimmune diseases, such as idiopathic thrombocytopenic purpura (ITP). The mechanisms by which IVIg can prevent platelet clearance in ITP patients are not fully understood but are known to require the participation of low affinity Fcgamma receptors (FcgammaRs), which interact poorly with monomeric immunoglobulin G (IgG). Given the importance of low affinity FcgammaRs in the treatment of ITP, we hypothesized that immune complexes (IC) produced in vitro could reproduce the effects of IVIg. Small-size tetramolecular IC were prepared using mouse monoclonal anti-human IgG and human Fc fragments. The effects of tetramolecular IC and IVIg on the in vitro and in vivo inhibition of phagocytosis of opsonized blood cells were compared. The results obtained showed that tetramolecular IC were at least six times more efficient than IVIg to prevent phagocytosis of opsonized red blood cells in vitro, and clearance of platelets in the thrombocytopenic mouse model.     

Complement fixation by anti-dsDNA antibodies in SLE: measurement by radioimmunoassay and relationship with disease activity.

We have developed a sensitive, solid phase radioimmunoassay (RIA) to quantify the amount of complement (C') fixation by anti-double-stranded DNA (anti-dsDNA) antibodies and have studied sera from 48 patients with systemic lupus erythematosus (SLE). 46% of the patients were positive in this assay. There was no correlation with serum C' levels, and only weak correlation with anti-dsDNA activity as measured by a solid phase RIA. An association was shown between positive values for C' fixation by anti-dsDNA antibodies and the presence of active lupus (p less than 0.01); there was a similar association with the presence of active renal disease in those patients with raised DNA binding (p less than 0.01). Our results suggest that quantitative measurement of C' fixation by anti-dsDNA antibodies may provide information about the pathogenicity of such antibodies in patients with SLE and be a better guide to potential end organ damage than the conventional measurement of DNA binding.     

Autoantibodies and drug-or metabolite-dependent antibodies in patients with diclofenac-induced immune haemolysis

Two patients with acute immune haemolytic anaemia caused by diclofenac are described. Both patients had developed IgG drug-independent autoantibodies and drug-dependent antibodies. The drug-dependent antibodies in one patient reacted with red blood cells (RBC) only in the presence of urine from patients receiving diclofenac (ex vivo antigen) but not in the presence of the drug itself or its known metabolites. This antibody appeared to recognize a trace metabolite which has not yet been identified. The drug-dependent antibodies in the second patient reacted with RBC in the presence of urine as ex vivo antigen as well as in the presence of the drug itself and its main metabolites. Incorrect diagnosis of such cases often is due to the occurrence of autoantibodies and/or unusual drug metabolism and excretion.     

Loss of red blood cell-complement regulatory proteins and increased levels of circulating immune complexes are associated with severe malarial anemia

Severe anemia is one of the most lethal complications of Plasmodium falciparum malaria. Red blood cells (RBCs) from children with severe malarial anemia are deficient in complement regulatory proteins (CR1 and CD55). A case-control, age- and sex-matched study was carried out to determine whether these deficiencies are acquired or inherited and the relative contribution of these complement regulatory protein deficiencies, the immune complex level, and the parasite density to the development of severe malarial anemia. RBC CR1 and CD55 deficiencies resolved after treatment, suggesting that these changes were acquired. Using conditional logistic regression, a decline in CD55 (or CR1) (odds ratio [OR], 4.2; 95% confidence interval [CI], 2.1-8.1; P<.001) and an increase in immune complex level (OR, 2.6; 95% CI, 1.5-4.8; P=.001) were significantly associated with severe malarial anemia.     

IgA-containing circulating immune complexes in patients with IgA nephropathy

The role of circulating immune complexes in the pathogenesis of IgA nephropathy (Berger's disease) is controversial. Previous studies have shown that a minority of these patients have immune complexes, but the methods used have been able to detect only IgG- or IgM-containing circulating Immune complexes. Using a sensitive, specific Raji cell radioimmunoassay for IgA-containing circulating immune complexes, we have examined serum specimens from 12 patients with IgA nephropathy for the presence of IgA-containing circulating immune complexes. In addition, the Raji cell IgG assay and the ¹²⁵I-C1q binding assay were used for the detection of IgG-or IgM-containing circulating immune complexes. Purified monoclonal antibodies against human IgA₁ and IgA₂ were used to determine the subclass of IgA present in renal biopsy specimens from five of these patients. Six of 12 (50 percent) patients had IgA-containing circulating immune complexes, whereas only two of 12 (17 percent) had positive results in the Raji IgG assay and one of 12 (8 percent) in the ¹²⁵I-C1q binding assay. There was no correlation between serum IgA, C3, C4, or factor B levels and the presence or level of IgA-containing circulating immune complexes. None of the three patients with renal failure had circulating immune complexes of any type. Of the seven patients with disease duration of two years or less, five (71 percent) had IgA-containing circulating immune complexes, and three (43 percent) had IgG- or IgM-containing complexes. In all five renal biopsy specimens examined for IgA subclass, diffuse, heavy, mesangial deposits of IgA₁ were seen, whereas IgA₂ staining was absent or present in only trace amounts. These findings suggest that IgA₁ is the predominant antibody in renal biopsy specimens from patients with IgA nephropathy. The finding of IgA-containing circulating immune complexes in these patients—and their more frequent occurrence in patients with early stages of the disease—suggests that IgA-containing circulating immune complexes may play a role in the pathogenesis of IgA nephropathy.     

Immune complexes in primary biliary cirrhosis: Higher prevalence of circulating immune complexes in patients with associated autoimmune features

A longitudinal study, examining the levels of immune complexes serially for three years, in serum from 88 patients with primary biliary cirrhosis was performed by the Raji cell radioimmunoassay. Studies of the association of autoimmune features in primary biliary cirrhosis and the effect of D-penicillamine therapy in relation to the levels of complexes were carried out. Twenty-two patients (25 percent) were found to have autoimmune features, such as Sjögren's syndrome, rheumatoid-like arthritis, scleroderma, Raynaud's disease, and Hashimoto's thyroiditis. In this subset of patients with primary biliary cirrhosis, a significantly higher prevalence (86 percent) of circulating immune complexes was detected compared with those patients showing no autoimmune features (60 percent). In addition, patients with associated autoimmune features had higher mean levels of immune complexes (259.7 μg AHG eq/ml) compared with those without autoimmune features (202.1 μg AHG eq/ml). The mean levels of complement C4, reflecting activation of classic complement pathway, were significantly lower in patients with elevated immune complexes and associated autoimmune features. The mean level of immune complexes in 13 patients receiving D-penicillamine, in contrast to the placebo group, decreased at one year but subsequently was greater than the initial level. Patients who had normal levels of immune complexes and received penicillamine therapy continued to have complex levels within the normal range for up to three years of follow-up study, but patients receiving placebo showed significantly elevated levels at subsequent intervals. Thus, levels of immune complexes in primary biliary cirrhosis may reflect the association with autoimmune features.