Autoimmunity: polyclonal activation or antigen induction?

B cell TLRs and induction of immunoglobulin class-switch DNA recombination

Toll-like receptors (TLRs) are a family of conserved pattern recognition receptors (PRRs). Engagement of B cell TLRs by microbe-associated molecular patterns (MAMPs) induces T-independent (TI) antibody responses and plays an important role in the early stages of T-dependent (TD) antibody responses before specific T cell help becomes available. The role of B cell TLRs in the antibody response is magnified by the synergy of B cell receptor (BCR) crosslinking and TLR engagement in inducing immunoglobulin (Ig) class switch DNA recombination (CSR), which crucially diversifies the antibody biological effector functions. Dual BCR/TLR engagement induces CSR to all Ig isotypes, as directed by cytokines, while TLR engagement alone induces marginal CSR. Integration of BCR and TLR signaling results in activation of the canonical and non-canonical NF-κB pathways, induction of activation-induced cytidine deaminase (AID) and germline transcription of IgH switch (S) regions. A critical role of B cell TLRs in CSR and the antibody response is emphasized by the emergence of several TLR ligands as integral components of vaccines that greatly boost humoral immunity in a B cell-intrinsic fashion.

Naturally occurring V region connected antibodies inhibit anti-dsDNA antibody reactivity with dsDNA

The production of autoantibodies against a vast array of self antigens, most notably double stranded (ds) DNA, characterized systemic lupus erythematosus (SLE). The purpose of this work is to study specific Ig fractions isolated from normal human serum (NHS) and their effect on the binding of anti-double-stranded deoxyribonucleic acid (dsDNA) antibodies (Abs) to dsDNA. A fraction named immunoglobulin G (IgG)-reactive IgG was purified from total NHS IgG by absorption onto (CNBr)-activated Sepharose 4B linked to intact IgG molecules (IgG-Sepharose column). IgG-reactive IgG was co-incubated with systemic lupus erythematosus (SLE) patient's serum and binding of the anti-dsDNA Abs to dsDNA was measured by enzyme-linked immunosorbent assay (ELISA). Co-incubation of SLE patient's serum with IgG-reactive IgG resulted in a dose-dependent reduction in binding of anti-dsDNA Abs to dsDNA. A reduction greater than 70% was observed at a concentration of 300 μg of IgG-reactive IgG per mL of a 400-fold diluted SLE patient's serum whereas total NHS IgG, at the same concentration, resulted in a 10% reduction in binding. The purification process used to isolate IgG-reactive IgG was based on interactions between intact Ig rather than on interactions between F(ab')(2) portions. IgG(2) is the predominant immunoglobulin (Ig) subclass in IgG-reactive IgG. Thus, IgG(2) might have an important role in the connectivity characteristics of NHS IgG. The capacity of IgG-reactive IgG to inhibit anti-DNA Ab binding to dsDNA may have potential application in the treatment of SLE. This targeted biological approach may provide an alternative strategy to immunosuppressants.

Deletion of the dominant autoantigen in NZB mice with autoimmune hemolytic anemia: effects on autoantibody and T-helper responses

The mechanisms underlying apparently spontaneous autoimmune diseases, such as autoimmune hemolytic anemia (AIHA) in New Zealand Black (NZB) mice, are unknown. Here, we determine the contribution of the dominant red blood cell (RBC) autoantigen, the anion exchanger protein Band 3, to the development of NZB autoimmune responses. The approach was to prevent Band 3 expression in NZB mice by disrupting the AE1 gene. AE1(-/-) NZB mice produced RBC autoantibodies at the same levels as the wild-type strain, but they differed in recognizing antigens that correspond to glycophorins, rather than Band 3. Splenic T-helper (Th) cells from wild-type NZB mice proliferated strongly against multiple Band 3 peptides, particularly the dominant epitope within aa861-874. This helper response was severely attenuated in AE1(-/-) animals, leaving only weak proliferation to peptide aa861-874. The results demonstrate that the defect in self-tolerance in NZB AIHA is directed to the RBC type, and is not specific for, or dependent on, Band 3. However, the predisposition to RBC autoimmunity may be focused onto Band 3 by weak Th cell cross-reactivity between the helper dominant epitope and an exogenous antigen. The redundancy of the major autoantigen illustrates the requirement for specific therapy to induce dominant forms of tolerance, such as T-cell regulation.

Hydroxyl radical modification of polyguanylic acid: role of modified guanine in circulating SLE anti-DNA autoantibodies

The hydroxyl radical generated by UV irradiation of hydrogen peroxide cause an extensive damage to guanine residues of ribohomopolymer, polyguanylic acid, poly (G) as investigated by spectrophotometric measurements, agarose gel electrophoresis, Sephadex G-200 gel filtration and DEAE Sephadex A-25 column chromatography. Native and ROS-poly (G) were highly immunogenic inducing high titre antibodies in rabbits. The antibodies showed wide range of cross reactivity with various synthetic polynucleotides exhibiting B-, A-, and allied conformations. The diverse antigen binding characteristics of the induced antibodies resembles to those of naturally occurring lupus anti-DNA autoantibodies. Sera from various SLE patients showed preferential binding to ROS-poly (G) than native poly (G), indicating that oxidatively modified guanine residues are better recognised. The significance of these findings in the induction of SLE anti-DNA autoantibodies by oxygen free radicals modified guanine residues in DNA has been discussed.

Autoanticorps, tolérance et auto-immunité

In 1900, the group from Metchnikoff suggested the concept of autoimmunization by demonstrating the presence of autoantibodies in normal conditions; which was opposed to the concept of horror autotoxicus raised by Ehrlich. Landsteiner's description of the transfusion compatibility rules and 50 year-later work from Burnett's and Medawar's groups lead to the clonal deletion theory as a general explanation of tolerance and autoimmunity. However, more recent work succeeded demonstrating that autoreactive B cells constitute a substantial part of the B-cell repertoire and that this autoreactive repertoire secretes the so-called natural autoantibodies (NAA) characterized by their broad reactivity mainly directed against very well conserved public epitopes. They fulfill the definition of an autoantibody since they are self-reactive, but they are not self-specific. As yet, NAA directed against determinants of polymorphism have not been reported. The presence of this repertoire in normal conditions challenges the clonal deletion theory as a unique explanation for self-tolerance. However, if we take into account that this autoreactive B-cell repertoire is not self-specific, this contradiction may not be a real one opposition. Indeed, the Lansteiner's rule that a subject belonging to group A will never produce anti-A antibodies and will always produce natural antibodies against the B-cell group, could never be challenged. Clonal deletion is probably accounting for this phenomenum. However, the serum of healthy adult individuals frequently exhibits low titers of anti-I antibodies, which is a precursor molecule of AB0 antigen system. The mechanism accounting for deletion of B cells directed against critical determinants like antigens A and B in the red blood cell system and allowing the production of autoantibodies against I remain elusive.

Antithyrotropin receptor antibody: an update

Numerous studies have reported the characteristics and significance concerning antithyrotropin receptor antibodies (TSHR-Abs), which cause Graves' disease and in some cases primary hypothyroidism. However, many unsolved questions concerning those antibodies remain. Here, recent developments in the study of TSHR-Abs are reviewed based on three aspects: mechanisms of TSHR-Ab production, antibody binding epitopes, and clinical TSHR-Ab assays. Mechanisms of TSHR-Ab production are discussed from five points of view: aberrant expression of the major histocompatibility complex, dysregulation of T cells, molecular mimicry, bystander effect, and expansion of autoreactive B cells. Regarding epitopes, unique TSHR-Abs have been reported that may explain the complicated pathophysiology of patients with TSHR-Ab diseases. Finally, recent efforts to improve TSHR-Ab measurements are introduced. Such efforts will contribute to clinical examinations and treatments for thyroid diseases as well as experimental methods of thyroidology.

Anti-insulin antibodies and the natural autoimmune response in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is characterized by the finding of ample serum autoantibodies. The role and the origin of many of these antibodies are still obscure. The aim of this work was to study the occurrence of anti-insulin antibodies (AIA) in SLE, and to postulate, based on AIA determination, on the mechanisms involved in the production of some autoantibodies in SLE. IgG and lgM AIA, anti-DNA antibodies (ADA) and anti-tetanus toxoid antibodies (ATA) were determined using ELISA in sera and B-lymphocytes culture media of 24 SLE patients, 10 healthy controls and 19 insulin-dependent diabetes mellitus (IDDM) patients. B- and T-lymphocytes were isolated using Ficoll gradient, depleted of T-cells using cyclosporin A, EBV infected and grown in medium. The frequencies of IgM-AIA and IgG-ADA were higher in SLE patients than in healthy controls (P < 0.02 and P < 0.05, respectively). The rate of IgM-AIA in SLE and IDDM was comparable, while IgG-AIA was significantly less common in SLE than in IDDM (P < 0.05). The prevalence of ATA in SLE patients and healthy controls was similar. These findings increase the spectrum of the humoral autoimmune response in SLE and suggest that part of it (natural autoantibodies) is independent of antigen driven response.

Significant association between the skewed natural antibody repertoire of Xid mice and resistance to Trypanosoma cruzi infection

The Xid mutation predominantly affects the development of B cells and consequently the levels and composition of natural antibodies in sera. In contrast to the congenic and susceptible BALB/c strain, immunodeficient BALB.Xid mice display a resistant phenotype both to acute Trypanosoma cruzi infection and to the development of severe cardiopathy. Because natural antibodies are known to be basically self-antigen driven, IgM and IgG natural antibody repertoires (NAR) were compared before and during infection in these two strains. The analysis revealed fundamental alterations of IgM and IgG NAR in pre- and post-infected Xid mice. In particular, relatively increased natural (pre-existing) autoreactive IgG, dominated by the unique recognition of a single band in autologous heart extracts, was typical for uninfected Xid mice. This natural autoreactive IgG directed to heart antigens disappeared early after infection not only in Xid, but also in individual BALB/c mice that survived the acute infection. Conversely, the subgroup of BALB/c mice that died early after infection presented the most pronounced instances of the rapid, relative increase of IgM reactivities to self and non-self proteins. These results suggest that self-reactive NAR may play a role in an immunoregulatory mechanism relevant for the determination of susceptibility/resistance to infections. This may act either by influencing specific responses, or by modulating the self-aggressive components responsible for pathology.

Lymphocyte polyclonal activation: a pitfall for vaccine design against infectious agents

In this article, Bernardo Reina-San-Martin, Alain Cosson and Paola Minoprio summarize the marked alterations in the immune system functions after infection that might account for the poor success of effective parasite vaccine development. Many of the studies on oligoclonal B- and T-cell responses to parasite antigens aiming at vaccination strategies would seem to ignore more general, and perhaps fundamental, aspects of parasite-immune system interactions. In essence, because of its consequences on immunopathology and parasite escape, the authors ascribe a central importance in the pathogenesis of parasitic diseases to the 'nonspecific' polyclonal lymphocyte activation that occurs during infection. Hence, novel targets and strategies for immune intervention should be considered.

Estrogen enhancement of anti-double-stranded DNA antibody and immunoglobulin G production in peripheral blood mononuclear cells from patients with systemic lupus erythematosus

OBJECTIVE

To study the in vitro effect of estrogen on IgG anti-double-stranded DNA (anti-dsDNA) antibody and total IgG production in peripheral blood mononuclear cells (PBMC) from patients with systemic lupus erythematosus (SLE), in order to elucidate its regulatory role in SLE.

METHODS

PBMC from SLE patients and normal donors were cultured with 17beta-estradiol (E2). IgG anti-dsDNA antibodies, total IgG, and cytokine activity in the culture supernatants were measured by enzyme-linked immunosorbent assay.

RESULTS

E2 enhanced production of IgG anti-dsDNA antibodies as well as total IgG in PBMC from SLE patients. Anti-dsDNA production in patients with inactive disease was less responsive to E2 than that in patients with active disease. E2 also enhanced total IgG, but not anti-dsDNA, production in the PBMC of normal donors. Antibody production was increased by E2 to a lesser extent in patients' B cells than in their PBMC. Anti-interleukin-10 (anti-IL-10) antibodies partially blocked the E2-induced increase in antibody production in patients' PBMC, but anti-IL-10 had no effect on B cells. E2 increased IL-10 production by patients' monocytes. Exogenous IL-10 acted additively with E2 in increasing antibody production in patients' B cells.

CONCLUSION

These results suggest that E2 may polyclonally increase the production of IgG, including IgG anti-dsDNA, in SLE patients' PBMC by enhancing B cell activity and by promoting IL-10 production in monocytes. These findings support the involvement of E2 in the pathogenesis of SLE.

Evidence for multiple mechanisms of polyclonal T cell activation in murine lupus

Individuals with systemic autoantibody-mediated diseases such as lupus have polyclonal T and B cell activation. Yet, autoantibody production is restricted to certain autoantigens. The mechanisms underlying this phenomenon remain unclear. We propose three potential mechanisms by which autoreactive helper T cell responses diversify to become polyclonal, yet are restricted to certain antigens. First, using a model where self-Ig peptides spontaneously activate T cells and modulate disease in lupus mice, we demonstrate that the numbers of autoantibody-augmenting T helper peptides increased across the Ig molecule as mice aged ("intramolecular determinant spreading"). Secondly, a single T cell hybridoma established from a (NZB x NZW)F1 mouse immunized with one self-Ig peptide recognized several Ig-derived determinants, which had little sequence homology with the immunizing peptide. Such determinant degeneracy can lead to polyclonality. To explore a mechanism for restriction to certain autoantigens, a protein database search was done for homologies with sequences of selected stimulatory Ig peptides. Identical sequences of such determinants were not found in murine proteins other than Ig. These occurred infrequently in nonautoantibody Ig, but quite commonly in lupus-related autoantibodies such as antibodies to DNA, cardiolipin, and erythrocytes. Thus, determinant spreading and degenerate recognition in T cells coupled with recurring use of T cell determinant sequences among autoantibodies result in polyclonality that is restricted to certain autoantigens.

Influence of microbial stimulation on hypergammaglobulinemia and autoantibody production in pristane-induced lupus

Pristane induces a lupus-like syndrome characterized by autoantibody production and glomerulonephritis in nonautoimmune strains of mice. Although it has been suggested that this syndrome results from nonspecific immune activation, there is little evidence so far that B cells are activated nonspecifically by pristane or that this promotes autoimmunity. In this study, we examined whether polyclonal hypergammaglobulinemia occurs in pristane-induced lupus, and its relationship to the production of anti-DNA, nRNP/Sm, and Su autoantibodies. In conventionally housed mice, there was a marked increase in total IgM and IgG3 2 weeks after i.p. pristane injection, followed by increased IgG1, IgG2a, and IgG2b levels. IgM levels were higher in pristane-treated specific pathogen-free (SPF) mice than in conventionally housed mice, whereas IgG and IgA levels were reduced. Pristane induced anti-nRNP/Sm and Su autoantibodies in SPF mice, but their onset was delayed and levels were lower than those in conventionally housed mice. There was no consistent relationship between total IgG1, 2a, and 2b hypergammaglobulinemia and production of anti-nRNP/Sm and Su autoantibodies. Moreover, the total Ig levels were similar in the anti-nRNP/Sm-positive and -negative groups. In contrast, production of IgM anti-ssDNA antibodies paralleled IgM hypergammaglobulinemia in some, but not all, mice. These studies indicate that pristane-induced lupus is associated with marked hypergammaglobulinemia, the magnitude of which is influenced by the microbial environment. However, anti-nRNP/Sm and Su autoantibody production is at least partly independent of polyclonal B cell activation. The data strongly suggest that pristane-induced lupus is not exclusively the consequence of nonspecific immune stimulation. They also point to the importance of microbial stimulation in the development of hypergammaglobulinemia in this inducible lupus model.

Polyclonal B cell activators and in vitro induction of auto-antibody reactive with collagen

Cells producing autoantibodies are known to be present in chronically inflamed periodontal tissues. In sites of chronic inflammation, polyclonal B cell activators (PBA) are known to exhibit adjuvant activity when combined with foreign antigens. These results prompted an examination of PBA in eliciting an antibody response to an autoantigen (i.e. collagen type I). Rat lymphocytes were stimulated with rat collagen (type I), microbial PBA (LPS) or the combination of LPS plus rat collagen in vitro. Anti-collagen antibody-forming cells (AFC) were enumerated using an ELISPOT assay. Collagen or LPS alone elicited few anti-collagen AFC but the addition of LPS to collagen resulted in a substantial adjuvant effect and yielded maximal responses to collagen. Comparisons of anti-collagen AFC from short-term immunized (2-6 wk after booster), non-immunized and long-term immunized (3-4 months after booster) animals were performed. It revealed that cells from recently immunized rats were significantly easier to activate than the other 2 groups. The adjuvant effect of microbial PBA may be important in anti-collagen antibody production and thus the localization of PBA in periodontal pockets may explain why anti-collagen AFC are restricted to the chronically inflamed periodontal tissues.

Testosterone suppresses anti-DNA antibody production in peripheral blood mononuclear cells from patients with systemic lupus erythematosus

OBJECTIVE

To study the in vitro effect of testosterone on anti-DNA antibody production in peripheral blood mononuclear cells (PBMC) from patients with systemic lupus erythematosus (SLE) in order to elucidate its regulatory role in SLE.

METHODS

PBMC from SLE patients were cultured with testosterone. IgG anti-double-stranded DNA (anti-dsDNA) antibody, total IgG, and cytokine activity in the supernatants were measured by enzyme-linked immunosorbent assay.

RESULTS

Testosterone suppressed both IgG anti-dsDNA antibody and total IgG production in PBMC from SLE patients. Antibody production in B cells was also suppressed by testosterone, although the magnitude of its effect on B cells was lower than that on PBMC. Interleukin-6 (IL-6) partially restored the testosterone-induced decrease in antibody levels in PBMC. Testosterone reduced IL-6 production in monocytes.

CONCLUSION

These results suggest that testosterone may directly suppress anti-DNA antibody production in PBMC from SLE patients by inhibiting B cell hyperactivity and, indirectly, by down-regulating IL-6 production in monocytes. These results support the therapeutic effects of testosterone on SLE.

Current concepts and advances in clinical laboratory testing for autoimmune diseases

This review discusses the current concepts of immunological tolerance, physiological vs. pathological autoimmunity, autoimmune diseases, and laboratory tests helpful in diagnosis. The autoantibodies in organ-specific autoimmune diseases are directed against antigens of the injured organs, whereas the antinuclear antibodies (ANA) detected in systemic autoimmune diseases are detected against a vast array of nuclear and intracellular antigens and peptides necessary for DNA/RNA synthesis, repair, splicing, and transcription. Knowledge of the mean titer and presence or absence of specific ANA types will help predict the nature of the disease and the response to therapy. Noteworthy features of these "ANA profiles" are (1) patients with systemic lupus erythematosus frequently have multiple types of ANA but anti-dsDNA and anti-SM are diagnostic, (2) patients with drug-induced lupus have ANA restricted to antihistone, (3) patients with mixed connective tissue disease have ANA restricted to anti-RNP, (4) patients with CREST (calcinosis, Raynaud's, esophageal dysmotility, sclerodactyly, and telangiectasia) syndrome have ANA restricted to anticentromere, (5) ANA with anti-SS-A/Ro specificity is associated with vasculitis and nephritis, (6) ANA with anti-SS-B/La and anti-nRNP specificities is associated with milder clinical disease, (7) ANAs with anti-Jo-1 and PM-Scl specificities are associated with pulmonary fibrosis and poor prognosis. Technological advances in the fields of molecular immunogenetics are guiding the studies of autoimmune diseases from serological and histopathological evaluations toward search for subcellular risk factors such as chemical and biological agents and susceptibility genes. Knowledge of these factors will help (1) to identify disease susceptibility genes prior to clinical onset and irreversible tissue damage, (2) to avoid environmental risk factors, and (3) to devise specific immunosuppressive strategies.

Production of anti-Ro/SS-A and anti-La/SS-B autoantibodies is closely coordinated in systemic lupus erythematosus and independent of anti-dsDNA production

Autoimmune diseases such as Sjögren's Syndrome and systemic lupus erythematosus (SLE) are characterized by serum autoantibodies against protein components of small cytoplasmic ribonucleoproteins (scRNPs). The origin and regulation of these anti-Ro/SS-A and anti-La/SS-B antibodies is not well understood. Regular co-occurrence of these two autoantibodies in humans together with murine studies on antibody responses against scRNPs after immunization suggest a role for scRNPs as common antigen. We sought additional evidence for this hypothesis in a longitudinal serological study of patients with SLE. Quantitative measurement of the antibody responses against Ro/SS-A and La/SS-B proteins and for comparison to dsDNA in 852 serum samples was performed. These samples were collected from nine patients during an average observation period of more than 10 years. A significant and strong correlation between the two anti-scRNP responses emerged during 90% of follow-up. In contrast, correlation of anti-scRNP with anti-dsDNA responses was remarkably absent in the same patients. Our results confirm the unique relationship between anti-Ro/SS-A and anti-La/ SS-B responses and could thus be interpreted as support for a model wherein induction and perpetuation of autoantibody production is dependent on scRNPs containing both proteins as antigen.

Hepatitis C virus and non-Hodgkin's lymphomas

The etiology of non-Hodgkin's lymphomas (NHL) remains a controversial matter, but, in the last few years, considerable evidence suggests that aberrations of the immune system and viruses may act as etiologic agents, in at least some cases of NHL. In fact, patients with primary immuno-deficiencies, or those suffering from diseases characterized by autoimmune dysfunction, show an increased risk for the development of NHL. Several viruses have been identified as possible etiologic agents for NHL; one of the best studied is the Epstein-Barr virus, which was detected in cultures of tumor cells from patients with Burkitt's lymphoma. The pathogenetic potential of this virus is illustrated by its association with an increasing number of malignant diseases. In addition, the human T-cell lymphotropic virus family (HTLV), was also recognized as possible etiologic agents for several lymphomas, such as cutaneous T-cell lymphoma and T-cell leukemia-lymphoma syndrome (HTLV-I), and T-cell hairy cell leukemia (HTLV-II). Recently, the presence of hepatitis C virus infection has also been recognized in several hematological malignancies such as mixed cryoglobulinemia, low-grade malignant lymphomas and Waldenström's disease. The possible etiopathogenetic role of this virus in non-Hodgkin's lymphomas is discussed on the basis of molecular, clinical, and epidemiological considerations.

Distributions of HLA class II alleles in autoantibody subsets among Norwegian patients with systemic lupus erythematosus

In order to find potential correlations between HLA class II alleles and anti-SS-A, -SS-B, -Sm and anti-snRNP responses among Norwegian patients with systemic lupus erythematosus (SLE), HLA-DRB1, -DRB3*0101, -DQA1 and -DQB1 alleles were determined by DNA typing 50 patients and 108 controls. HLA distributions were analysed in the following autoantibody subgroups: anti-SS-A with -SS-B, anti-SS-A without -SS-B, anti-snRNP without -Sm, anti-SS-A without -snRNP and anti-snRNP without -SS-A. The autoantibodies were detected by EIA (enzyme immunuassay). Patients with anti-SS-A and -SS-B had significantly increased frequencies of DRB1*03, DRB3*0101, DQA1*0501, DQB1*0201 (in linkage disequilibrium) versus controls and versus patients without anti-SS-A and -SS-B. No differences in HLA distribution were found when the group with anti-SS-A alone was compared to the group with anti-SS-A and concomitant -SS-B. Comparing the groups with and without anti-SS-A and -SS-B, the highest RR were found for the alleles DRB1*03, DRB3*0101, DQB1*0501, DQB1*0201 (in linkage disequilibrium) with RR: 16.8, 5.0, 19.6, 10.3, respectively, P < 0.05). RR for DQw2/DQw6 heterozygotes was 3.5 (Ns.), and RR for cases having DQ alpha molecules with glutamine in position 34 and DQ beta molecules with leucine in position 26 on both chains was 6.3 (P < 0.05). No HLA associations were observed in the group with anti-snRNP without concomitant -Sm or without concomitant -SS-A. These results show that production of anti-SS-A and -SS-B is associated to the HLA alleles DRB1*03, DRB3*0101, DQA1*0501, DQB1*0201, and that this haplotype shows stronger correlation to these responses than DQw2/DQw6 heterozygosity or HLA molecules having glutamine in position 34 (DQ alpha) and leucine in position 26 (DQ beta). The failure to observe any correlation with DRBI*15,16 (DR2) in the group with anti-SS-A alone may demonstrate ethnic differences concerning this response. The failure to identify any HLA associations for the anti-snRNP response may reflect the heterogeneity of the molecules that constitute this antigen.

Autoantibodies to malondialdehyde-modified epitope in connective tissue diseases and vasculitides

Malondialdehyde (MDA), a peroxidative end-product released during polyunsaturated fatty acid degradation, reacts strongly with lysine residues of cellular proteins. MDA-modified proteins become immunogenic and may elicit specific autoantibody formation. We hypothesized that systemic diseases in which inflammatory events occur, could be an interesting model for studying oxidative stress. A few studies have suggested that MDA-modified proteins may exist in systemic diseases, and that autoantibodies to MDA-modified structures might reflect this oxidative process. Autoantibodies to MDA-modified epitope(s) were therefore assayed in sera of patients with systemic lupus erythematosus (SLE, n = 29), scleroderma (SCL, n = 11), giant cell arteritis (GCA, n = 11), periarteritis nodosa (PAN, n = 10), rheumatoid arthritis (RA, n = 9), and healthy subjects (HS, n = 32). Significantly increased anti-MDA-modified epitope(s) autoantibodies were found in patients with SLE and also in other systemic diseases such as PAN and SCL. Autoantibodies to MDA-modified epitope(s) were predominantly of IgM isotype, with low levels of IgG and no IgA activity. In SLE, anti-MDA-modified epitope(s) autoantibody titres correlated strongly with systemic lupus activity measure (SLAM, r = 0.702, P = 0.0001), anti-nuclear antigen autoantibodies (ANA, r = 0.4, P = 0.029), IgG anti-cardiolipin (r = 0.558, P = 0.03) and the steroid drug regimen (r = 0.52, P = 0.004). Autoantibodies to MDA-modified epitope(s) may reflect oxidative modifications occurring in systemic diseases, and might be useful as clinical markers of SLE activity if further investigated.

Investigation of the prevalence and clinical associations of antibodies to human fibronectin in systemic lupus erythematosus

OBJECTIVES

To assess the prevalence of antibodies to human fibronectin (anti-Fn) in sera of patients with certain connective tissue diseases and to determine their association with disease activity and the pattern of organ involvement in patients with systemic lupus erythematosus (SLE).

METHODS

A capture enzyme linked immunosorbent assay (ELISA) was developed to quantify anti-Fn antibodies in serum samples from 65 patients with well characterised SLE, 50 with rheumatoid arthritis (RA), 15 with Behçet's disease (BD), 15 with systemic vasculitis and 36 healthy subjects. An anti-Fn antibody titre greater than mean + 3SD of the healthy control log values after back transformation to the normal scale was considered positive. Disease activity in SLE patients was scored using the British Isles Lupus Assessment Group (BILAG) Index. Erythrocyte sedimentation rate (ESR), concentrations of anti-dsDNA antibody, soluble interleukin-2 receptors (sIL-2R), C3, C4, C3 degradation products (C3dg) and immunoglobulin, and antinuclear antibody (ANA) titres were measured in blood samples from SLE patients; neopterin concentration was measured in corresponding urine samples.

RESULTS

Anti-Fn antibodies were found in 22 of 65 SLE patients (33.8%), seven of 50 with RA (14%), one of 15 with BD (6.6%) and none of the 15 subjects with vasculitis. Thirty SLE patients had active disease and 35 had inactive disease; their median anti-Fn concentrations were 117 u/ml (range 47-450) and 68 u/ml (range 17-334), respectively (p = 0.0001). The presence of anti-Fn did not correlate with immunoglobulin concentrations or ANA titres in these sera. No significant difference was found between SLE patients with disease activity in one major organ system compared with multiple organ involvement, as defined by BILAG (p = 0.19). However, patients with musculoskeletal manifestations had consistently greater anti-Fn concentrations compared with patients with other clinical manifestations. There were significant correlations between amounts of anti-Fn in SLE sera and ESR (rs = 0.25, p = 0.045), sIL-2R (rs = 0.28, p = 0.024) and urine neopterin (rs = 0.3, p = 0.016) but not with serum anti-dsDNA antibody titres, plasma C3, C3dg or C4. However multiple regression analysis showed a low significant correlation only with sIL-2R and BILAG score (p = 0.047 and 0.042, respectively).

CONCLUSION

Anti-Fn antibodies were detected in 34% of SLE patients and in small proportions of RA and BD patients. An association between serum anti-Fn and disease activity in SLE has been identified and most SLE patients with musculoskeletal involvement had increased anti-Fn antibody concentrations.

Host-microflora interaction in systemic lupus erythematosus (SLE): circulating antibodies to the indigenous bacteria of the intestinal tract

Experimental data suggest a role for the microflora in the disease expression of systemic lupus erythematosus (SLE). In active SLE anti-ds-DNA antibodies are supposed to be pathogenic by forming immune complexes with DNA. Bacteria might induce the production of anti-ds-DNA antibodies. To explore the relation between the host and his microflora in SLE in comparison with healthy controls we studied the prevalence of systemic antibodies to faecal bacteria that were discriminated by their morphology by indirect immunofluorescence. IgM titres against their own faecal microflora were found to be lower both in active and inactive SLE when compared to healthy individuals. IgG-class antibacterial antibodies were increased in inactive SLE but decreased in active SLE compared to inactive SLE and healthy controls, although plasma levels of total IgG were almost doubled in active SLE. The lower IgG antibacterial antibody titres in active SLE might possibly result from sequestration of these IgG antibodies in immune complexes, indicating a possible role for antibacterial antibodies in exacerbations of SLE.

Safety considerations for nucleic acid vaccines

Whilst it is premature to formulate guidelines for the manufacturing requirements of a nucleic acid vaccine, it can never be too early to discuss and debate the issues surrounding the use of a novel biotherapeutic. The major safety issues posed by nucleic acid vaccination include the possibility of transformation (or tumorigenic) events in recipients of a DNA vaccine, the potential formation of anti-DNA antibodies, and unexpected and untoward effects of long-term expression of a foreign antigen. This paper examines the extent to which these points impinge on the safety of DNA vaccines.

The glomerular basement membrane in lupus nephritis

Systemic lupus erythematosus is a disease that is particularly suited for studies of glomerular basement membrane pathology. Classification of the renal pathology of lupus nephritis is usually based on light microscopic features, combined with immunofluorescence findings and electron microscopic alterations. Study of renal biopsy helps to distinguish potentially reversible and irreversible disease, and to estimate prognosis of patients with lupus nephritis. Moreover, studies of human disease, as well as the availability of animal models and in vitro cell culture systems employing biochemical and molecular biological studies of extracellular matrix, have led to a considerable increase in knowledge of the pathogenetic events underlying derangements of the glomerular basement membrane in lupus nephritis.

Precursor frequencies for DNA-specific B lymphocytes in patients with systemic lupus erythematosus (SLE)

Precursor frequencies for anti-DNA-secreting B cells were estimated in six healthy donors and 18 SLE patients with active and inactive disease. Precursors for IgG anti-dsDNA-secreting B cells were exclusively detected in SLE patients (73% of active patients and one inactive patient, 0.01-0.99% of IgG-producing B cells). These frequencies were in the same order of magnitude as frequencies of precursors for IgG anti-tetanus toxoid, which were detectable in three healthy volunteers after booster vaccination (0.07-0.8% of IgG-producing B cells), but not before (< 0.01%). Precursors for IgG anti-ss-DNA secreting B cells were observed in 33% of healthy donors and in 78% of SLE patients (0.01-0.32% of IgG-producing B cells). Only patient-derived IgG anti-DNA clones cross-reacted with (33%) or were monoreactive to dsDNA (12%). Precursors for IgM anti-DNA-secreting B cells were observed in healthy donors and SLE patients in comparable frequencies and with similar reactivities with ssDNA and dsDNA. Segregation analyses and sorting experiments showed that > 94% of clones secreting IgG anti-DNA were derived from in vivo sIgG+ B cells. sIgM+ B cells were induced to switch in vitro; however, only twice were cultures containing IgM and IgG anti-DNA antibodies observed under clonal conditions. In conclusion, our results indicate that precursor B cells for IgG anti-dsDNA in SLE patients are similarly selected and expanded as are precursor B cells specific for foreign antigens such as tetanus toxoid.

Host-microflora interaction in systemic lupus erythematosus (SLE): colonization resistance of the indigenous bacteria of the intestinal tract

Experimental data suggest a role for the microflora in Systemic Lupus Erythematosus (SLE). Anti-ds-DNA antibodies may be pathogenic in SLE by forming immune complexes with DNA. Foreign bacteria in the intestines could constitute the stimulus for anti-ds-DNA antibody production in SLE. Colonization Resistance (CR) is the defence capacity of the indigenous microflora against colonization of the intestines by foreign bacteria. A low CR implies increase of translocation of bacteria and a higher chance of subsequent, possibly DNA-cross-reacting antibacterial antibody production. We measured CR by a comprehensive biotyping technique in healthy individuals and patients with inactive and active SLE. CR tended to be lower in active SLE patients than in healthy individuals (P = 0.09, Wilcoxon one sided, with correction for ties). This could indicate that in SLE more and different bacteria translocate across the gut wall due to a lower CR. Some of these may serve as polyclonal B cell activators or as antigens cross-reacting with DNA.

Sex- and age-dependency of IgG auto-antibodies against IL-1 alpha in healthy humans

Naturally occurring anti-interleukin (IL)-1 alpha IgG antibodies (Ab-IL-1 alpha) were measured in sera of 466 healthy Danish blood donors. Ab-IL-1 alpha bound IL-1 alpha with exceptionally high affinity (Kd: 10(-11) M) and neutralized both cell-associated and extracellular IL-1 alpha but not IL-1 beta or IL-1 receptor antagonist. More than 80% of the saturable binding of rIL-1 alpha to serum was to Ab-IL-1 alpha, suggesting that these antibodies are the quantitatively most important IL-1 alpha-binding components in serum. Judged by second antibody precipitation assay, the prevalence of Ab-IL-1 alpha varied between 30% and 75% and correlated positively with age (P = 0.037). The binding capacity of serum also increased with age. Although men were more frequently positive than women (P < 0.001), there were no sex- or age-dependent alterations in the average affinities of the antibodies. Free IL-1 alpha-like molecules were generally not detected in these sera. However, acid treatment showed that 25% of Ab-IL-1 alpha-positive sera contained low amounts of IL-1 alpha-Ab-IL-1 alpha immune complexes. IgG4 represented the main IgG isotype, whereas IgG3 Ab-IL-1 alpha were undetectable. The relative amounts of IgG4 Ab-IL-1 alpha increased while IgG2-and IgG1 Ab-IL-1 alpha decreased in elderly individuals. The presence in normal individuals and the lack of affinity maturation with age suggest that Ab-IL-1 alpha may be regulatory natural auto-antibodies perhaps coded by germline genes.

Serum and gingival crevicular fluid anti-desmosomal antibodies in periodontitis

SDS polyacrylamide gel electrophoresis separates desmosomal proteins and glycoproteins of bovine tongue epithelium by their relative molecular mass. The Western immunoblot technique was used to reveal the reactions of desmosomal proteins and glycoproteins with naturally occurring antibodies in serum and gingival crevicular fluid (GCF). Naturally-occurring serum and GCF antibodies (IgG and IgM) from periodontitis patients and healthy, unaffected controls reacted with desmosomal proteins (desmoplakins) and glycoproteins (desmogleins). Sera from 90% of subjects with periodontitis showed increased reactions of IgG with desmoplakins (240 and 210 kDa) and 80% with desmogleins (165, 130, and 115 kDa), when compared with unaffected controls. Patients' IgG reacted with desmosomal components more strongly than IgM. IgG antibodies against desmosomal antigens in GCF showed similar specificities from patients and healthy subjects and to their serums. When GCF within individuals with periodontitis was compared, anti-desmosomal IgG from diseased sites showed greater reactivity than healthy controls. These data suggest that anti-desmosomal antibodies are a normal part of the immune repertoire. The presence of elevated titers of anti-desmosomal antibodies appear to distinguish periodontitis from unaffected sites. When detected, elevated titers of anti-desmosomal antibodies may contribute to the pathogenesis and indicate increased risk of periodontitis.

Trypanosoma cruzi infection enhances polyreactive antibody response in an acute case of human Chagas' disease

The kinetics of antibody response in an acute case of human Chagas' disease was investigated. Hypergammaglubulinaemia appeared at day 17 of infection, and persisted after 66 days of infection, at which time parasitaemia became undetectable. Titration of immunoglobulins showed that the three principal isotypes were involved in the response, emphasizing polyclonal B cell activation. Total IgA was detected before total IgM, and the latter before total IgG. High titres of autoantibodies were found among IgM and IgG subclasses. IgA was also the first isotype to be detected among specific anti-Trypanosoma cruzi antibodies. However, the maximal parasite antibody response was attained after 30 days of infection for all isotypes. With regard to possible cross-reactivity between molecules of host and parasite, adsorption experiments on T. cruzi-specific immunosorbent were designed. Specific antibodies, present in the eluates, also recognized natural antigens, especially laminin. In order to characterize the alpha-galactose epitope of laminin, adsorption experiments on sheep erythrocytes were performed, and revealed the possible presence of another epitope on the glycoprotein. Our results indicate that in the case of Chagas' disease investigated here, polyclonal activation occurred; moreover, they suggest that molecular mimicry may play a role by increasing autoantibodies, probably via a parasite-driven mechanism.

Detection of autoantibodies against islet amyloid polypeptide in human serum. Lack of association with type 1 (insulin-dependent) diabetes mellitus, or with conditions favouring amyloid deposition in islets. The Belgian Diabetes Registry

A radiobinding assay for the detection of autoantibodies against islet amyloid polypeptide was developed, analytically validated, and--in parallel with a similar assay for the detection of autoantibodies against insulin--applied to sera from recent-onset Type 1 (insulin-dependent) diabetic patients and from age- and sex-matched control subjects. There was no difference in islet amyloid polypeptide autoantibody titres between patient groups and matched control subjects, nor within subject groups according to age. At onset of Type 1 diabetes, elevated islet amyloid polypeptide-autoantibody levels (> 97th percentile of control subjects) were only detected in 1 of 30 patients aged 0-19 years and in 2 of 35 patients aged 20-39 years. By contrast, insulin autoantibodies were frequently demonstrated, in particular at onset of diabetes under age 20 (0-19 years: 18 of 30 patients; 20-39 years: 10 of 35 patients; p < 0.01 vs matched control subjects). Islet amyloid polypeptide autoantibodies were not detectable in 3 insulinoma patients nor in 37 patients (aged 33-70 years) with Type 2 diabetes (vs 1 of 40 in matched control subjects). In positive serum, adsorption onto protein A-Sepharose removed islet amyloid polypeptide binding activity, hereby confirming its antibody nature. In conclusion, Type 1 diabetes is associated with an age-dependent autoantibody reaction against insulin but not against islet amyloid polypeptide. Conditions associated with amyloid deposition in islets (Type 2 diabetes, insulinoma and ageing) do not favour the formation of autoantibodies against islet amyloid polypeptide.

Analysis of heavy and light chain use of lupus-associated anti-La/SS-B and anti-Sm autoantibodies reveals two distinct underlying immunoregulatory mechanisms

The immunoregulatory mechanisms involved in autoimmune diseases are still unclear. One approach to elucidating these mechanisms involves evaluation of the clonality of the lymphocytes involved in autoimmunity. Molecular analysis of the rearrangement patterns of antigen receptor genes in T cells and B cells has produced ambiguous results. The present study focuses on the analysis of the autoantibodies themselves, being the end products of autoimmune reactivity. Heavy and light chain use of autoantibodies and of total IgG was determined in sera containing anti-La/SS-B and/or anti-Sm antibodies, two autoantibody specificities associated with rheumatic diseases such as systemic lupus erythematosus and Sjögren's syndrome. From our experiments, the anti-La/SS-B response emerges as an oligoclonal, IgG1-restricted B-cell response associated with sharply elevated levels of total serum IgG1-kappa. These characteristics are in sharp contrast to the polyclonal, IgG-subclass-unrestricted anti-Sm response which is accompanied by normal or slightly elevated total serum IgG levels. These findings suggest that anti-La/SS-B autoantibodies, in contrast to anti-Sm autoantibodies, are the product of a restricted oligoclonal B-cell response and thus may be the consequence of a (virally triggered) benign B-cell lymphoma.

Activation of IL-6 production by UV irradiation of blood mononuclear cells from patients with systemic lupus erythematosus

Cultured mononuclear cells from patients with systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and normal donors were assayed for their ability to secrete IL-6 both spontaneously and after exposure to UV light. Mononuclear cells from SLE, RA and atopic control patients produced IL-6 spontaneously, while those from normal donors did not. Spontaneous production of IL-6 occurred in the non-adherent cell population. UV light-induced IL-6 production was confined exclusively to the SLE patients and was present only in the macrophage/monocyte fraction. This stimulation was induced by wavelengths in the UVA, UVB but not the UVC portion of the spectrum. These results suggest that cytokine release may be involved in the exacerbations of SLE provoked by photosensitivity.

Autoimmune diseases: overview and current concepts of pathogenesis

No single theory or mechanism can adequately explain all features or pathogenesis of autoimmune diseases. The clinically wide spectrum of autoimmune diseases is best considered as the mosaic of autoimmunity and the many factors involved are genetic, hormonal, immunological, and environmental. These multifactorial considerations help to explain not only the diversity of various clinical diseases encountered but also the differences in clinical manifestations from patient to patient within the same disease group.

Clonal frequency analysis of B cells producing pathogenic anti-DNA antibody-associated idiotypes in systemic lupus erythematosus

In order to identify the mechanism responsible for autoantibody production in systemic lupus erythematosus (SLE), B cell repertoires associated with anti-DNA idiotypes were explored by a limiting dilution analysis using Epstein-Barr virus (EBV) transformation methods and ELISA spot assays. The frequencies of B cell clones producing antibodies to DNA and to conventional antigens, tetanus toxoid, dinitrophenyl, or keyhole limpet hemocyanin were higher in active SLE compared to those in inactive SLE and in normal subjects. In addition, there was a disproportionate increase in anti-DNA antibody- and anti-DNA idiotype (Id)-producing clones at the precursor cell levels as well as at the mature cell level. On the other hand, numbers of anti-Id clones against anti-DNA-Id, termed 0-81 Id, were markedly increased at inactive stages of the disease but not at active stages. These were confirmed by serial studies in some patients with SLE. These results support a two-step mechanism for autoantibody production, in which initial polyclonal activation is followed by an antigen-driven process, and indicate an alteration of the precursor B cell repertoire in SLE, which may also associate with a preferential expansion of anti-DNA clones.

The requirements for growth of in vivo activated autoimmune B cells are similar to those of in vitro generated lipopolysaccharide B cell blasts and dissimilar to anti-IgM plus IL-4 induced B lymphoblasts

The requirements for growth of in vivo activated B cells (natural blasts) from autoimmune NZB/W mice and of B cells from the same animals activated in vitro with either LPS or anti-IgM plus IL4 (mimicking 'in vitro' antigen induced TH cell-B cell interaction) were studied comparatively. The proliferation of natural and LPS blasts was inhibited by anti-IgM antibodies and augmented by recombinant IL-5. In contrast, anti-IgM stimulated the growth of anti-IgM plus IL-4 primed B cells but was without effect on the proliferative responses in the presence of IL-5. The growth inhibition induced by anti-IgM signalling on natural and LPS blasts seemed to be due to cross-linking of sIg rather than to binding of anti-IgM antibodies to the Fc receptors since a similar effect was observed with the F(ab)'2 fragment of this molecule. Maximum proliferation was obtained by a combination of IL-4 and IL-5 in natural and LPS blasts, whereas peak responses in anti-IgM plus IL-4 blasts were achieved by a combination of anti-IgM and IL-4. Lymphoblasts recovered after preculturing natural blasts in medium alone (more differentiated in vivo activated B cells) displayed high spontaneous proliferation which was strongly inhibited by anti-IgM. This inhibition was reversed partially by IL-4 and totally by IL-5. To define better the role of BLy+ cells in the spleen of NZB/W mice, purified Ly1+ and Ly1- cells, obtained by separation using magnetic beads, were analysed. The growth of both cell subpopulations was inhibited by anti-IgM and enhanced by IL-5. Cytotoxic elimination of Ly1+ cells from the primed B blast populations did not modify the proliferative pattern of these cells. Our results show that the growth requirements of in vivo activated autoimmune B cells resemble those of LPS blasts and differ from those following stimulation with anti-IgM plus IL-4, suggesting that B cells in systemic autoimmune diseases may have been activated by polyclonal stimulation. Nevertheless, other mechanisms for autoimmune B cell activation cannot be ruled out by the present experimental approach.

Guillain-Barré syndrome following cardiopulmonary bypass

Two cases of Guillain-Barré syndrome occurring after otherwise uneventful cardiac surgery using cardiopulmonary bypass are presented. Although Guillain-Barré syndrome has been reported after surgical procedures, it has never been reported after cardiopulmonary bypass. Recent literature supports an immune mediated process for Guillain-Barré. Cardiopulmonary bypass may act as the trigger for this immune mediated response.

Autostimulatory effects of IL-6 on excessive B cell differentiation in patients with systemic lupus erythematosus: analysis of IL-6 production and IL-6R expression

Introducing avidin-biotin complex ELISA for anti-DNA antibody, the mechanism of in vitro production of anti-ssDNA antibody as well as of polyclonal immunoglobulin mediated by an IL-6-IL-6R loop was studied in patients with systemic lupus erythematosus (SLE). Regardless of the presence or absence of T cells, B cells from SLE patients could produce IgG anti-ssDNA antibody as well as total IgG without any stimulation. Low density B cells obtained by Percoll gradient density centrifugation responded to rIL-6 to produce IgG and IgG anti-ssDNA antibody. rIL-2 and rIL-4 had lesser effects on the differentiation of low density B cells. In fact, IL-6R was preferentially expressed on low density B cells from active SLE patients, as detected by anti-IL-6R MoAb, MT18, which did not inhibit IL-6 binding. SLE B cells, especially high density B cells, produced greater amounts of IL-6 in culture supernatants than did T cells, regardless of whether disease was active or inactive. Normal T cells and B cells did not produce significant amounts of IL-6. Thus, endogenous IL-6 produced by high density B cells bound to the IL-6R preferentially expressed on the low density B cells, and drove them into terminal differentiation, especially in active SLE patients. Further, addition of polyclonal anti-IL-6 or anti-IL-6R MoAb (PM1), which inhibited IL-6 binding, both inhibited IgG anti-ssDNA antibody as well as total IgG production by SLE B cells in a dose-dependent manner. These results suggest that interruption of the autocrine IL-6 loop would be of therapeutic value in SLE.

Immunity to self-antigens in periodontal disease

Auto-antibody to collagen, previously detected in periodontal disease, may represent either a response to local tissue damage or be the manifestation of a disturbance of the host immune response induced by the periodontal flora and its products. In an effort to distinguish between these two hypotheses, this study was undertaken to determine circulating IgG auto-antibody levels in 41 periodontal-disease patients against 12 self-antigens (salmon DS-DNA, calf SS-DNA, human and bovine thyroglobulin, rabbit proteoglycan, horse myoglobin, bovine myosin, actin, fetuin, human transferrin, cytochrome C, and human Type I collagen) and compare them to those in 21 periodontal disease-free subjects. None of the detected IgG auto-antibody levels were significantly different between periodontal disease and control sera (Mann-Whitney U-test, P greater than 0.05) except for human Type I collagen (P less than 0.05). Fifty-six percent of patients and 38% of controls were "broad responders;" i.e., 50% or more of the auto-antibody levels were higher than the median values of the control group; however, these values were not significantly different using the chi-square test. It was concluded that the destruction of connective tissue components is the primary driving force in the induction of the enhanced auto-antibody response found in periodontal disease. This response is apparently secondary to the primary bacterial infection which remains the major etiologic event.

Does mitogen-induced antibody production by normal blood cells mimic spontaneous production in lupus?

Blood cells from patients with systemic lupus erythematosus (SLE) showed a raised level of spontaneous IgG production that included antibodies to DNA and to common environmental antigens (influenza virus haemagglutinin, adenovirus hexon and mannan from Candida albicans). In contrast, no IgG antibody was produced against an antigen not normally encountered in the UK (egg antigen from Schistosoma mansoni) or a self-antigen not generally associated with SLE (thyroglobulin). IgM production was raised to a lesser extent and only antibodies to DNA were detected. When normal cells were stimulated with pokeweed mitogen or S. aureus organisms, the specificity pattern of IgG production was similar to that described above for SLE with the major exception of the absence of IgG anti-DNA. IgM antibodies to DNA and all the other antigens were detected, but the specificity of the IgM ELISA assays for the protein antigens needs further clarification. The activity of IgM anti-DNA relative to total IgM was far greater in the SLE system. These results provide further evidence that a response to self-antigen is required for production of pathogenic IgG autoantibodies in SLE.

Contemporary concepts of autoimmunity and autoimmune diseases

No single theory or mechanism can explain the phenomenon of autoimmunity and autoimmune diseases. Not all autoimmune responses are harmful or "forbidden." Considerable research has indicated that autoimmune response may be normal and important in the regulation of the immune system. Autoimmunity may play a role in a wide range of clinical states including physiological clearance of dead cells, and cell components, aging, response to viral and microbial infections, and generalized immunological diseases. There are many factors involved in autoimmunity including genetic, hormonal, immunological, and environmental factors. The susceptibility to autoimmune diseases is multifactorial and polygenic. There is a definite association of the autoimmune diseases with MHC alleles. Also, non-MHC genes are involved in disease susceptibility. Numerous mechanisms of autoimmunity have been discussed. There may be an alteration with dysregulation of the immune system with defective generation of normal suppressor mechanisms or an altered neuroendocrine regulation. The altered immune system will make the host more susceptible to autoimmune disease. Autoimmune reactions can occur in a host with a normal immune system. Some examples are as follows: 1. Infection or damage to host target organ with release or alteration of autoantigen 2. Molecular mimicry or cross-reactivity between virus or bacteria and host autoantigens 3. Abnormal expression of MHC molecules by antigen-presenting cells in target cells resulting in activation of autoreactive T-cells. 4. Drug administration

Spectrotypes of anti-DNA antibodies show that anti-DNA-secreting B-cell clones of SLE patients are restricted in number, stable and long lived

We have investigated the number of B-lymphocyte clones secreting anti-ssDNA antibodies in SLE patients and a chronic active hepatitis patient by isoelectric focusing and reverse immunoblotting of serum antibodies. Individual clones can be identified by the unique pattern of bands produced by their antibodies (the clonotype). Using this technique, we have shown that the anti-DNA response of the majority of SLE patients is clonally restricted, in many cases only a single B-cell clone responding. We have also measured qualitative and quantitative changes in expression of B-cell clones and shown that these clones are remarkably stable with lifespans of up to six years or more. These results are in agreement with previous observations of clonal restriction of the anti-DNA response in three mouse models of SLE and in addition show that, unlike the mouse models, human anti-DNA-secreting B-cell clones are extremely stable and long-lived. The implications of these results for models of initiation and regulation of the autoimmune response are discussed.

Autoimmunity to human thyroglobulin. Respective epitopic specificity patterns of anti-human thyroglobulin autoantibodies in patients with Sjögren's syndrome and patients with Hashimoto's thyroiditis

We evaluated the epitopic specificity pattern of anti-human thyroglobulin (anti-hTg) autoantibodies from patients with primary Sjögren's syndrome (SS). All of the primary SS sera tested contained both IgG and IgM anti-hTg autoantibodies recognizing at least 1 region on hTg; in 65% of the cases, 3 or more regions were recognized. A strong recognition of region II, as is seen in Hashimoto's thyroiditis, was associated with thyroid disorder in primary SS. These results emphasize the importance of region II in autoimmune thyroid disease.

Chemiluminescence is increased in a subgroup of PHA-stimulated lymphocytes from patients with systemic lupus erythematosus and inhibited by 5-lipoxygenase inhibitors

Chemiluminescence (CL) was examined in phytohemagglutinin (PHA)-stimulated control and lupus lymphocytes because oxidative radicals have the chemical potential to generate DNA changes recently observed in lupus lymphocytes. Increased CL was found in 30 of 65 PHA-stimulated lupus lymphocyte samples by a luminol assay. CL did not correspond statistically to oxidative potential measured by a nitroblue tetrazolium assay. CL did not appear to be related to disease activity, organ involvement, or drug therapy. However, six of six males tested had positive CL activity. Cocultivation of CL-positive PHA-stimulated lupus lymphocytes with metabolic inhibitors of various oxidative enzymes revealed that 50 microM arachidonic acid dramatically inhibited the excess oxidation. A specific inhibitor of 5-lipoxygenase activity, 3 microM nordihydroguaiaretic acid, abolished excess CL activity. These studies suggest that chemiluminescence assays can be used to better understand the oxidative metabolism in lupus lymphocytes. The enzyme 5-lipoxygenase may be dysfunctional in a subgroup of lupus patients.

New Zealand white rabbits immunized with RNA-complexed total histones develop an autoimmune-like response

The antibody response of rabbits immunized with a total histone mixture containing randomly coiled H1/H5, H2A, H2B, H3 and H4 devoid of DNA was investigated in direct and competitive ELISA. The antisera were tested with isolated histones and chromatin and with a series of overlapping synthetic peptides covering the entire sequences of the four core histones and two peptides of H1. It was found that the New Zealand (NZ) white rabbits immunized with the total histone (TH) mixture complexed with RNA produced IgG antibodies reacting with histones and with a number of histone peptides but not with chromatin. The antisera also contained IgG antibodies which bound components that correspond to common target antigens in autoimmune diseases such as native dsDNA, peptides of Sm-D antigen, ubiquitin, branched peptides of ubiquitinated H2A and poly(ADP-ribose). By competition experiments, it was shown that these antibodies corresponded to non-crossreacting antibody populations. New Zealand rabbits immunized with TH in the absence of RNA or random outbred rabbits immunized with the RNA-complexed histone fraction produced antibodies reacting with histone, chromatin and very few histone peptides, while no activity with non-related antigens was observed. The pattern of reactivity of antisera raised in NZ rabbits with RNA-complexed TH was found to be very similar to that observed in sera of patients with systemic lupus erythematosus while, in contrast, the antibody response was very different in NZ or outbred rabbits immunized with various native nuclear particles and with individual histones. Altered nucleosome particles rather than native nucleosomes may represent the antigenic stimulus giving rise to autoantibodies.

The contribution of non-MHC genes to susceptibility to autoimmune diseases

Genetic studies of experimental models of autoimmune diseases, including systemic lupus-like syndromes and organ-specific autoimmunity, provide major information on genetic control of autoimmune diseases. In addition to genes known to be linked to the major histocompatibility complex (MHC), these studies point to multiple genes located outside the MHC that influence the onset and the progression of autoimmune diseases. Identification of these genes and of their interrelationships is now a major task that will be facilitated by recent progress in molecular biology and gene mapping. Among candidate genes, antigen-receptor genes (i.e., immunoglobulin- and T-cell receptor genes) most likely contribute an important part of the autoimmune susceptibility in several of these animal models. Available linkage data suggest a similar involvement of these antigen-receptor genes in several human autoimmune diseases. In addition to a better understanding of pathogenic mechanisms associated with autoimmunity, the knowledge of these disease-predisposing genes is expected to permit a better classification of often complex syndromes as well as the design of new treatments.