The forces driving autoimmune disease

Infection, inflammation and host carbohydrates: a Glyco-Evasion Hypothesis

Microbial immune evasion can be achieved through the expression, or mimicry, of host-like carbohydrates on the microbial cell surface to hide from detection. However, disparate reports collectively suggest that evasion could also be accomplished through the modulation of the host glycosylation pathways, a mechanism that we call the "Glyco-Evasion Hypothesis". Here, we will summarize the evidence in support of this paradigm by reviewing three separate bodies of work present in the literature. We review how infection and inflammation can lead to host glycosylation changes, how host glycosylation changes can increase susceptibility to infection and inflammation and how glycosylation impacts molecular and cellular function. Then, using these data as a foundation, we propose a unifying hypothesis in which microbial products can hijack host glycosylation to manipulate the immune response to the advantage of the pathogen. This model reveals areas of research that we believe could significantly improve our fight against infectious disease.

Cancer-Induced, Immune-Mediated Ocular Degenerations

The means whereby vision can be lost from a disease located distant from the eye include autoimmunity, with sensitization resulting from extraocular stimuli, a process illustrated here by the immunologic confusion caused by cancers. The uncontrolled proliferation of malignancies commonly involves the expression of components of the central nervous system, but a damaging loss of tolerance is rare. When autoimmunity does develop, organ-specific antigens are more often involved than the more generalized and widely disseminated common neuronal components. A focus upon a single antigen is typical of the immune-mediated paraneoplasia, a collection of syndromes identified by unusual antibody reactions. This review provides an outline of the immunologic trail that led to the recognition of autoimmunity in paraneoplastic ocular degenerations, how specific antibody reactions aid in diagnosis, and the possibility of including antibodies in modes for sight-saving intervention. 'Those who do not know history are destined to repeat it'.

SNP analysis of genes implicated in T cell proliferation in primary biliary cirrhosis

Previous studies on primary biliary cirrhosis (PBC) have focused on the role of T lymphocytes as potential effectors of tissue injury. We hypothesized that single nucleotide polymorphisms (SNPs) of genes involved in lymphocyte proliferation would be responsible for uncontrolled expansion of T cells and autoreactivity. To address this, we genotyped DNA from 154 patients with PBC and 166 ethnically matched healthy controls for SNPs of five candidate genes (60G/A CTLA-4, 1858 C/T LYP, -IVS9 C/T foxp3, p1323 C/G ICOS and -9606 T/C CD25) using a TaqMan assay.

We report herein a statistically significant decrease in homozygosity rate for the 60A⋆CTLA-4 allele in patients with PBC compared to controls (p = 0.0411). Moreover, we found a significant association of the same allele and of the LYP⋆T allele with anti-mitochondrial antibody (AMA) serum negativity (p = 0.0304 and 0.0094, respectively). No association between any of the other studied SNPs and PBC susceptibility, progression, or AMA status was observed. In conclusion, given the high prevalence of SNPs in CTLA-4 detected in numerous autoimmune diseases, we encourage a more detailed genetic analysis of this candidate gene. Further, although obtained from a limited number of AMA-negative subjects, our data suggest a potential genetic heterogeneity for this specific subgroup of patients with PBC.

Follow-up of avidity and titre of anti-myeloperoxidase antibodies in sera from patients with propylthiouracil-induced vasculitis

OBJECTIVE

Propylthiouracil (PTU) has been known to induce myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA) positive vasculitis. Our previous study indicated that the increase of avidity of MPO-ANCA might be associated with the occurrence of clinical vasculitis in patients with PTU-induced ANCA. The current study aimed to follow-up the avidity and titre of anti-MPO antibodies in sequential sera from patients with PTU-induced ANCA-associated systemic vasculitis (AASV).

METHODS

Six patients with PTU-induced vasculitis were enrolled in the current study. Serial sera in both active phase and in remission were collected. MPO-ANCA avidity was assessed by antigen-inhibition enzyme-linked immunosorbent assays (ELISAs), and avidity constant (aK) was determined as the reciprocal value of the MPO molar concentration in the liquid phase resulting in 50% inhibition of anti-MPO antibody binding to MPO in solid phase ELISA. Titres of MPO-ANCA were determined by using serial serum dilutions in MPO-ELISA.

RESULTS

After cessation of PTU and initiation of immunosuppressive therapy, the avidity and titre of MPO-ANCA decreased significantly during follow-up in sera from all the patients, and the avidity decreased much more quickly than the titres.

CONCLUSION

Our study indicates that avidity of anti-MPO antibodies might be more closely associated with clinical vasculitis than titre.

Serum antiguanosine antibodies as a marker for SLE disease activity and pathogen potential

BACKGROUND

This article reviews research conducted on the immunogenicity of the nucleosides of DNA, especially guanosine, the most immunologically active nucleoside. Discussed is the relationship between circulating antibodies to guanosine, their potential role in SLE disease activity, the binding properties of monoclonal antiguanosine antibody (4H2) compared to polyclonal antiguanosine antibodies in humans with SLE, cell membrane penetration by these antibodies and their interference with signal transduction possibly related to their binding to mitochondria and their apparent GTPase activity.

METHODS

Enzyme-linked immunosorbent assay methodology was used to show clinical relationships between antiguanosine antibody levels and disease activity in SLE. These results are discussed along with methods of detecting cell penetration by this antibody using special staining techniques, laser-scanning microscope detection of mitochondrial localization, and interference of cAMP and pKA production/activation. Additionally, there is some discussion regarding the assay used to detect enzymatic activity of antiguanosine antibodies.

RESULTS

Enhanced circulating levels of antiguanosine antibodies in patients with SLE correlate closely with SLE disease activity. Other factors are discussed that support the pathogenic potential of these antibodies, including their ability to penetrate lymphocytes, bind to mitochondria, inactivate mitochondrial function, interfere with signal transduction, and their potential enzymatically activity.

CONCLUSIONS

Antiguanosine antibodies correlate with SLE disease activity and may be pathogenically important in SLE by interfering with signal transduction, inactivating mitochondrial and cell function in patients with SLE.

Hypotheses on a germline origin of antibody diversity. Possible applications: improvement of the efficiency of immune response and autoimmune disease treatment

In this paper, the antibody reaction is supposed to be due to the combination of a limited number of different antibodies against the epitopes of the antigen. In addition, the efficient part of the epitopes of proteins is assumed to be the size of dipeptides. The 400 different dipeptides would be distributed in two sets, those which are foreign to the host, against which would be directed antibodies, and those which are present in the proteins of the self, which would elicit no reaction. Each chain of the antibodies would recognise one aminoacid and 40 genes would be sufficient (20 for the light chains and 20 for the heavy chains) to code for the variable parts of the immunoglobulins against proteic antigens. With these hypotheses, the combination of antibodies against at least four different epitopes of the size of dipeptides can account for the main characteristics of the antibody reaction: response against any foreign proteic antigen and specificity. In fact, the epitopes have been found to be larger than dipeptides, several additional aminoacids are involved in the antibody-binding sites. Somatic mutations and VDJ recombinations are selected to give the maximal affinity for the antigens. However, these mechanisms have not been shown to create different specificities from the same V genes. Moreover, the phenomenon of heteroclisis and the decrease, due to mutations, of antigen-binding capacity of antibodies, sometimes observed, are better explained by the model proposed here than by the classical theory. The modification of the epitope subset of the self, by intrathymic injection of antibodies against particular pathogens, is proposed to improve the immune response when microorganisms develop immune escape mechanisms. On the other hand, in the case of autoimmune diseases, the displacement of autoantibodies against self-epitopes could be carried out by the injection into the thymus of specific anti-idiotypic antibodies.

From infection to autoimmunity

We have investigated two models of virally-induced autoimmune myocarditis in mice using widely different infectious agents. Infection of susceptible BALB/c mice with either Coxsackievirus or murine cytomegalovirus results in the development of acute myocarditis from day 7-14 after infection, and chronic myocarditis from day 28 onwards. The chronic phase of myocarditis is associated with mononuclear infiltration of the myocardium and the production of autoantibodies to cardiac myosin, although infectious virus cannot be detected past day 14 of infection. T cells and autoantibodies have been shown to be important for the development of autoimmune myocarditis. Many researchers have investigated the role of molecular mimicry in the development of myocarditis after viral infection. This review explores the 'adjuvant' effect of infection on the innate immune response and how this determines the progression to autoimmune disease. We show that NK cells protect against the development of disease, while complement and complement receptors are involved in the development of autoimmune myocarditis induced by inoculation with virus or cardiac myosin, respectively. Our results suggest that the innate immune response to viral and self-antigens may determine whether susceptible strains of mice progress to chronic autoimmune disease. These findings have broad implications for understanding the role of infection in inducing autoimmune disease.

Association of viral load in plasma samples of HIV-infected hemophilia patients with autoantibodies and gp120-containing immune complexes on CD4+ lymphocytes

OBJECTIVE

We investigated whether the induction of antilymphocyte autoantibodies and immune complexes is associated with the activity of HIV replication.

METHODS

Viral HIV-1 RNA was measured in the plasma samples of 84 HIV+ hemophilia patients and correlated with the IgM, IgG, IgM/IgG and IgM/IgG/gp120 load of circulating CD4+ lymphocytes, CD4+ and CD8+ cell counts, plasma neopterin levels and in vitro T-cell responses to mitogens and pooled allogeneic stimulator cells.

RESULTS

Compared to patients with no immune complexes, on circulating CD4+ lymphocytes, viral load was increased in patients with IgM, IgM/IgG or IgM/IgG/gp120 complexes. Sequential analysis of HIV+ patients showed that peaks of retroviral activity were associated with the subsequent formation of CD4+ lymphocyte-reactive IgM and IgG autoantibodies and gp120-containing immune complexes.

CONCLUSION

The induction of autoantibodies and immune complexes attached to CD4+ lymphocytes is associated with periods of increased viral activity in HIV-infected patients.

Intrathecal immune response in patients with neuroborreliosis: specificity of antibodies for neuronal proteins

Cerebrospinal fluid (CSF) and serum samples of 47 patients with serologically proven neuroborreliosis were examined by Western blotting for antibodies to a crude extract of human cortex (CNS) comprising a multitude (> 40) of protein bands. Intrathecal synthesis of total immunoglobulins was determined by the Reiber formula and of autoantibodies to CNS proteins by enzyme-linked immunoassay (ELISA) and by Western blotting. Employing ELISA, intrathecal synthesis of autoantibodies (IgG, IgM and/or IgA) was demonstrated in 40 of 47 patients with neuroborreliosis (85%), in 5 of 40 with multiple sclerosis (12%), and in 22 of 40 with viral meningoencephalitis (55%). Of 40, 35 and 15 patients with neuroborreliosis and an intrathecal synthesis of total IgG, IgM or IgA, 20 revealed an intrathecal production of IgG antibodies (50%), 24 of IgM antibodies (68%) and 6 of IgA autoantiodies (40%) in the CSF. The specificity of autoantibodies differed greatly between most patients. Of 24 different CNS proteins which elicited an immune response in various patients, identities could be determined only for the myelin basic protein (5 of 40) and for the three neurofilament proteins (NF-68, NF-150, NF-200) (13 of 40 patients). In this limited number of patients no significant correlation between individual clinical symptoms and certain autoantiodies could be detected. The higher frequency of intrathecally produced autoantibodies in patients with neuroborreliosis is assumed to result from mitogenic rather than specific activation of autoreactive B-cell clones by Borrelia burgdorferi. The pathogenic relevance of these autoantibodies remains to be determined.

Epstein-Barr virus-induced autoimmune responses. II. Immunoglobulin G autoantibodies to mimicking and nonmimicking epitopes. Presence in autoimmune disease

During infectious mononucleosis, IgM autoantibodies are generated to a protein, p542, which contains a glycine-rich 28-mer epitope cross-reactive with the Epstein-Barr nuclear antigen-1 through Epstein-Barr nuclear antigen-1's glycine/alanine repeat. In normal individuals it is uncommon to find IgG anti-p542, but among patients with progressive systemic sclerosis, systemic lupus erythematosus, and ulcerative colitis high IgG anti-p542 (> 3 SD above the mean of normal 20-50 yr controls) occurred frequently. Lesser elevations occurred in Sjögren's syndrome, rheumatoid arthritis, ankylosing spondylitis, and Crohn's disease, but none with chronic hepatitis B infection. The reactive epitopes on p542 were mapped with deletion mutants, which indicated that the glycine-rich 28-mer was the major antigenic determinant, with lesser antibody responses to other epitopes. We conclude that normally there is an inability to generate IgG autoantibodies to the cross-reactive (mimicking) epitope of the p542 host protein, but that this inability is overcome in a proportion of patients with autoimmune disease. We conclude also that non-cross-reactive autoepitopes exist on p542 protein, to which IgG autoantibodies can commonly be formed in autoimmune disorders. The mechanisms responsible for the latter must involve different mechanisms than those responsible for autoantibodies to the mimicking epitope.

Self and non-self antigen in diabetic autoimmunity: molecules and mechanisms

In this article, we have summarized current facts, models and views of the autoimmunity that leads to destruction of insulin-producing beta-cells and consequent Type 1 (insulin-dependent) diabetes mellitus. The presence of strong susceptibility and resistance gene loci distinguishes this condition from other autoimmune disorders, but environmental disease factors must conspire to produce disease. The mapping of most of the genetic risk (or disease resistance) to specific alleles in the major histocompatibility locus (MHC class II) has direct functional implications for our understanding of autoimmunity in diabetes and directly implies that presentation of a likely narrow set of peptides is critical to the development of diabetic autoimmunity. While many core scientific questions remain to be answered, current insight into the disease process is beginning to have direct clinical impact with concerted efforts towards disease prevention or intervention by immunological means. In this process, identification of the critical antigenic epitopes recognized by diabetes-associated T cells has achieved highest priority.

Isotypic distribution of anti-pyruvate dehydrogenase antibodies in patients with primary biliary cirrhosis and their family members

IgG subclasses of anti-pyruvate dehydrogenase (PDH) antibodies were determined in 72 patients with primary biliary cirrhosis. All isotypes were detected, but IgG3, IgG1, and IgG2 predominated independently or in association. An average of 33.3 +/- 19.1% of the anti-PDH IgG was IgG1 (mean optical density, 0.863 +/- 0.783, vs 0.053 +/- 0.038 in the normal controls), 25.0 +/- 17.8 IgG2 (0.652 +/- 0.656 vs 0.062 +/- 0.030), 39.5 +/- 23.4% IgG3 (1.140 +/- 0.917 vs 0.010 +/- 0.023), and 2.4 +/- 7.4% IgG4 (0.060 +/- 0.182 vs 0.012 +/- 0.007). Anti-PDH IgG were restricted to IgG1 in the family members of patients (0.180 +/- 0.403).

Isotype and affinity of anti-myeloperoxidase autoantibodies in systemic vasculitis

The role of immunoglobulin (Ig) isotype and affinity of antimyeloperoxidase (MPO) antibodies in the clinical expression of vasculitis (organ involvement, severity and evolution) remains incompletely defined. We have determined the anti-MPO antibody isotypes, as well as the apparent affinity constant (aK) of anti-MPO IgG by using fluid phase MPO inhibition of IgG binding in an MPO specific ELISA. Twenty-eight patients with anti-MPO antibodies and necrotic and crescentic glomerulonephritis, either isolated or associated to various other organ localizations, were analyzed. Serum samples were obtained before treatment and during follow-up. No association was observed between the isotype, the level or apparent affinity of anti-MPO antibodies and the clinical symptoms, severity, and organ distribution of vasculitis, including alveolar hemorrhage. No significant correlation was found between the apparent affinity and the level of anti-MPO IgG. However, the presence of anti-MPO IgM was clearly associated with low affinity anti-MPO IgG and vice versa. Furthermore, in a longitudinal study, high levels of anti-MPO IgM, when present, were observed early in the course of the disease and in some cases preceded the reappearance of anti-MPO IgG during relapses. High affinity anti-MPO IgG were usually present before treatment. Immunosuppressive therapy resulted in decreased apparent affinity and level of anti-MPO IgG. Importantly, anti-MPO IgG level increased during relapses but the affinity of these IgG autoantibodies remained low.(ABSTRACT TRUNCATED AT 250 WORDS)

IgG3 reactive rheumatoid factor in rheumatoid arthritis: etiologic and pathogenic considerations

Rheumatoid factor (RF) is a polyclonal autoantibody directed against the Fc portion of IgG. Although the role of RF in patients with rheumatoid arthritis (RA) is unclear, immune complexes that form between RF and IgG can activate the classical complement (C) pathway, leading to pathogenic outcomes involving inflammatory events and tissue damage. The specificity of serum RF and RF produced by rheumatoid synovial cells (RSC) is different. Serum RF has specificity for rabbit IgG and human IgG subclasses IgG1, 2, and 4, but binds poorly to IgG3. The affinity of serum RF for IgG Fc is low, having an association constant of 10(4)-10(5) M-1. RSC RF, however, has specificity for human IgG and high avidity for IgG3. Because of this greater specificity and avidity for IgG3, and because RSC RF may be pathogenically more important than serum RF, an important role for IgG3-reactive RF in RA may exist. Binding of RF to IgG may be dependent on the allotype and glycosylation of IgG. Infectious agents present in RA patients may directly or indirectly induce the production of certain RF. In this communication, we review and expand on several observations examining the role of IgG3-reactive RF in RA including: 1) binding differences between RF derived from RSC and serum; 2) glycosylation characteristics of IgG and its interaction with RF; 3) apparent allotype dependent binding of IgG3-reactive RF; and 4) possible relationship between infectious agents and the production of IgG3-reactive RF. Taken together, these observations suggest an important role for IgG3-reactive RF in better understanding the etiology and pathogenesis of RA.

Immunosuppressive therapy of autoimmune diseases

Cyclosporin A, corticosteroids and cyclophosphamide show a remarkable efficacy in a large number of autoimmune diseases. However, their effect is dependent on continuous drug administration with potential risks of drug toxicity and over immunosuppression. Results recently obtained in animal models, particularly with anti-CD3 and anti-CD4 monoclonal antibodies, indicate that reestablishment of tolerance to self antigens is a feasible goal.

Immunosuppressive therapy of autoimmune diseases

Ciclosporin and cyclophosphamide show a remarkable efficacy in most autoimmune diseases. However, their effect is dependent on continuous drug administration with risks of drug toxicity and over immunosuppression. Results recently obtained in animal models, discussed here by Jean François Bach particularly with anti-CD3 and anti-CD4 monoclonal antibodies, indicate that reestablishment of tolerance to self antigens is a feasible goal.

Autoimmunity--towards the year 2001

The interactive roles of T cells, major histocompatibility complex (MHC) class I and II molecules and antigen-presenting cells in the generation of autoimmunity is the subject of much discussion. A recent symposium contributed to the debate by inviting experts in several fields of immunology to answer specific questions relating to the mechanisms that trigger autoimmunity.