Cross-reactivity Of Autoantibodies Research Articles

Spontaneous regression of tumours. Possible cross reactivity of autoantibodies against carbonic anhydrase I.

Spontaneous tumour regression in patients after high dose therapy and autologous stem cell transplantation or patients with standard therapy is accompanied with the presence of high titers autoantibodies against carbonic anhydrase I (CA I). The concomitant presence of aplastic anaemia-like syndrome in these patients points to parallel bone marrow suppression during this period. It seems that CA I, an 'obscure' enzyme, does not have any significant physiological role in humans. One possible explanation points to the fact that autoantibodies against CA I may target another antigen(s) which is(are) important in tumour growth as well as in normal haematopoiesis. One of the candidates for such a target is the DNA polymerase theta.

The autoimmune targets in IPEX are dominated by gut epithelial proteins

The autoimmune targets in IPEX are dominated by gut epithelial proteins

Autoantibody cross-reactivity with a microbial protein from a prevalent human gut commensal in antiphospholipid syndrome

Abstract Given the vast antigenic source of the gut microbiota, we hypothesized that human gut commensal bacteria induce and sustain autoreactivity via cross-reactivity. As a paradigm, we studied the antiphospholipid syndrome (APS), which is a serious autoimmune clotting disorder of unknown etiology but with a well-defined major autoantigen, b2-glycoprotein I (b2GPI). Infectious triggers are implicated in transient autoantibody production, but the persistent stimuli for anti-b2GPI antibodies remain unknown. To this end, we characterized b2GPI-specific monoclonal autoantibody reactivity to an in silico identified candidate commensal, Roseburia intestinalis (R.int), that is abundant in human stool from APS patients as detected by a species-specific PCR. Using an APS-derived monoclonal antibody, P1-117, that binds to the major B cell epitope in domain I of b2GPI (RGGMR), we tested for cross-reactivity to anaerobically cultured R.int and its candidate cross-reactive R.int protein (WP_006857340.1). P1-117 bound significantly to R.int lysates whereas a control antibody specific for another epitope within b2GPI did not. Further, P1-117 displayed significant binding to the recombinantly expressed R.int cross-reactive candidate protein. BALB/cJ mice immunized with whole heat-killed R.int displayed significant cross-reactive splenocytes and low titers of cross-reactive IgG autoantibodies. In conclusion, we present here in vitro and in vivo studies supporting cross-reactivity of pathogenic b2GPI-specific autoantibody with a common gut commensal. This study provides a concept for persistently colonizing gut commensals as chronic cross-reactive triggers in genetically susceptible autoimmune hosts such as APS patients.

Acute longitudinal myelitis as the first presentation in child with systemic lupus erythematosus concurrent with positive antiphospholipid antibody

Systemic lupus erythematosus (SLE) is a multi-system auto-immune disorder that is characterized by widespread immune deregulation, formation of auto–antibodies, and immune complexes, resulting in inflammation and potential damage to variety of organs. 25-95% it is complicated by neurological or neuropsychiatric symptoms, which is referred to as neuropsychiatric SLE (NPSLE). NPSLE contain both central and peripheral nervous systems, which includes transverse myelitis. We report our experience of concurrent manifestation of transverse myelitis as an initial presentation of SLE, which suggests the common immune-mediated mechanisms of diseases. We here report the case of a 7-year-old girl with SLE who first presented with features of TM. The patient developed ascending weakness starting from low extremities, experienced difficulty in voiding. An initial diagnosis of TM was made on the basis of clinical findings and MRI spine, which displayed T2 weighted high signal intensities at thoracic level. She partially respond to intravenous immunoglobulin therapy, and serological analysis revealed the presence of anti-dsDNA, anti nuclear antibody with decreased level of complements. The diagnosis was revised to acute transverse myelitis resulting from SLE. Additional methylprednisolone pulse therapy led to rapid clinical improvement. This was followed by oral prednisolone and cyclophosphamide pulse therapy. The crossreactivity of auto-antibodies and increased susceptibility to infection owing to immunologic changes associated with lupus may form the basis of the association. Systemic Lupus Erytheromyitis should consider as an etiology of transverse myelitis. Aggressive treatment may alter the course and lead to a better outcome.

Severe warm autoimmune haemolytic anaemia due to anti-Jk(a) autoantibody associated with Parvovirus B19 infection in a child.

Severe warm autoimmune haemolytic anaemia due to anti-Jk(a) autoantibody associated with Parvovirus B19 infection in a child.

Why human pemphigoid autoantibodies do not trigger disease by the passive transfer into mice?

The recapitulation of disease features in animals by the transfer of patient autoantibodies has been used to demonstrate the autoimmune nature of several diseases. Failure of disease induction by the passive transfer of autoantibodies has been assigned to a limited cross-reactivity of the autoantibodies with the murine tissue. However, the possibility that the passively transferred “inflammatory” patient autoantibodies may not be able to unfold their pathogenic potential due to restricted Fc-dependent effector functions has not yet been systematically explored. In this study we analyze the interaction of patients’ autoantibodies with murine complement and granulocytes. Bullous pemphigoid is a blistering disease associated with autoantibodies, which are thought to induce subepidermal blistering by activating complement and granulocytes. The passive transfer of patients autoantibodies failed to induce skin blistering in wild type mice. The cross-reactivity of pemphigoid autoantibodies with murine antigens was analyzed in silico, ex vivo and by the passive transfer of IgG in vivo. Complement-fixing ability of patients’ autoantibodies was evaluated by complement-binding test. Granulocyte activation was assessed by reactive oxygen species production assay and the cryosection model. We have found that although pemphigoid autoantibodies bound to murine skin in vitro and in vivo, they showed a lower capacity to fix murine complement and a reduced ability to activate murine granulocytes when compared with human complement and cells, respectively. These results indicate that for disease models using the passive transfer of patient autoantibodies, their interaction with the innate factors of the host should be optimized to match the human situation.

An Analysis of the Cross-Reactivity of Autoantibodies to GAD65 and GAD67 in Diabetes

BackgroundAutoantibodies to GAD65 (anti-GAD65) are present in the sera of 70–80% of patients with type 1 diabetes (T1D), but antibodies to the structurally similar 67 kDa isoform GAD67 are rare. Antibodies to GAD67 may represent a cross-reactive population of anti-GAD65, but this has not been formally tested.Methodology/Principal FindingsIn this study we examined the frequency, levels and affinity of anti-GAD67 in diabetes sera that contained anti-GAD65, and compared the specificity of GAD65 and GAD67 reactivity. Anti-GAD65 and anti-GAD67 were measured by radioimmunoprecipitation (RIP) using 125I labeled recombinant GAD65 and GAD67. For each antibody population, the specificity of the binding was measured by incubation with 100-fold excess of unlabeled GAD in homologous and heterologous inhibition assays, and the affinity of binding with GAD65 and GAD67 was measured in selected sera. Sera were also tested for reactivity to GAD65 and GAD67 by immunoblotting. Of the 85 sera that contained antibodies to GAD65, 28 contained anti–GAD67 measured by RIP. Inhibition with unlabeled GAD65 substantially or completely reduced antibody reactivity with both 125I GAD65 and with 125I GAD67. In contrast, unlabeled GAD67 reduced autoantibody reactivity with 125I GAD67 but not with 125I GAD65. Both populations of antibodies were of high affinity (>1010 l/mol).ConclusionsOur findings show that autoantibodies to GAD67 represent a minor population of anti-GAD65 that are reactive with a cross-reactive epitope found also on GAD67. Experimental results confirm that GAD65 is the major autoantigen in T1D, and that GAD67 per se has very low immunogenicity. We discuss our findings in light of the known similarities between the structures of the GAD isoforms, in particular the location of a minor cross-reactive epitope that could be induced by epitope spreading.

Cross-reactivity of autoantibodies from patients with epidermolysis bullosa acquisita with murine collagen VII.

The pathomechanism of antibody-mediated tissue damage in autoimmune diseases can be best studied in experimental models by passively transferring specific autoantibodies into animals. The reproduction of the disease in animals depends on several factors, including the cross-reactivity of patient autoantibodies with the animal tissue. Here, we show that autoantibodies from patients with epidermolysis bullosa acquisita (EBA), a subepidermal autoimmune blistering disease, recognize multiple epitopes on murine collagen VII. Indirect immunofluorescence microscopy revealed that EBA patients' IgG cross-reacts with mouse skin. Overlapping, recombinant fragments of murine collagen VII were used to characterize the reactivity of EBA sera and to map the epitopes on the murine antigen by ELISA and immunoblotting. The patients' autoantibody binding to murine collagen VII triggered pathogenic events as demonstrated by a complement fixing and an ex vivo granulocyte-dependent dermal-epidermal separation assay. These findings should greatly facilitate the development of improved disease models and novel therapeutic strategies.

Paraneoplastic neurological syndrome and polyglandular autoimmune syndrome type 2 in a case of small cell lung cancer

We report a female patient with small cell lung cancer (SCLC) and clinical findings consistent with polyglandular autoimmune syndrome type 2 (PGA2) and paraneoplastic neurological syndrome (PNS). To the best...

Anti-La (SS-B) but not anti-Ro52 (SS-A) antibodies cross-react with laminin--a role in the pathogenesis of congenital heart block?

Cross-reactions between maternally derived autoantibodies and fetal cardiac antigens have been postulated to play a role in the pathogenesis of congenital heart block (CHB). We have explored the cross-reactivity of autoantibodies to the small ribonuclear autoantigens, La/SS-B and Ro/SS-A, with laminin, the major component of cardiac sarcolemmal membrane using affinity-purified antibodies from patients with Sjögren's syndrome (SS). Anti-La antibodies purified from eight of 10 patients cross-reacted significantly with mouse laminin by ELISA. In contrast, purified antibodies to Ro52 from the same 10 patients showed little or no binding to laminin. Laminin inhibited up to 70% binding of anti-La antibodies to La antigen, and La inhibited up to 65% binding of anti-La antibodies to laminin. The cross-reaction was further examined on cryosections of 10 human fetal hearts aged from 8.7 to 14.9 weeks of gestation, two normal adult hearts, and one pathological adult heart with a diagnosis of dilated cardiomyopathy. Anti-Ro52 antibodies did not bind to the surface of cardiac cells. However, anti-La antibodies from seven of 10 patients tested bound to the surface of fetal myocytes from hearts aged 9.4 to 14.9 weeks of gestation, and also to the myocytes from the pathological adult heart but not to normal adult hearts. Preincubation with La antigen abolished the binding of anti-La antibodies to the surface of adult heart myocytes with dilated cardiomyopathy, and pre-incubation with mouse laminin could partially block this binding. These results suggest that molecular mimicry between laminin and La, but not Ro52, may act as a target for specific maternal autoantibodies, and contribute to the pathogenesis of CHB at a critical stage during fetal cardiac development.

A milk‐free diet downregulates folate receptor autoimmunity in cerebral folate deficiency syndrome

In cerebral folate deficiency syndrome, the presence of autoantibodies against the folate receptor (FR) explains decreased folate transport to the central nervous system and the clinical response to folinic acid. Autoantibody crossreactivity with milk FR from different species prompted us to test the effect of a milk-free diet. Intervention with a milkfree diet in 12 children (nine males, three females; mean age 6y [SD 4y 11mo], range 1-19y), decreased autoantibody titer significantly from 2.08pmol of FR blocked per ml of serum (SD 2.1; range 0.24-8.35) to 0.35pmol (SD 0.49; range 0-1.32; p=0.012) over 3 to 13 months, whereas FR autoantibody titer increased significantly to 6.53 (SD 6.08; range 0.54-14.07; p=0.013) in nine children who were reexposed to milk for 6 to 14 weeks. In 12 children on a normal diet (eight males, four females; mean age 5y 5mo [SD 4y 1mo], range 1y 6mo-16y 4mo), the antibody titer increased significantly from 0.84pmol of FR blocked per ml (SD 0.39; range 0.24-1.44) to 3.04pmol (SD 1.42; range 0.84-6.01; p=0.001) over 10 to 24 months. Decreasing the autoantibody titer with a milk-free diet in conjunction with folinic acid therapy may be advocated for these patients.

Humoral immune response to citrullinated collagen type II determinants in early rheumatoid arthritis

Collagen type II (CII) is a relevant joint-specific autoantigen in the pathogenesis of rheumatoid arthritis (RA). Whereas the reasons for the breakage of self tolerance to this major cartilage component are still enigmatic, T cell responses to glycosylated CII determinants in RA patients indicate that post-translational modifications play a role. Since the conversion of arginine into citrulline by peptidylarginine deiminases (PAD) in some non-joint-specific antigens such as filaggrin or fibrin has been shown to give rise to RA-specific humoral immune responses, we investigated whether PAD modification of cartilage-specific CII might affect its recognition by circulating autoantibodies in early RA. In vitro treatment with purified PAD led to arginine deimination of native CII or of synthetic CII peptides as evidenced by amino acid analysis. The citrullination resulted in modified recognition of the immunodominant CII epitope C1(III) (amino acid residues 359-369) by murine and human antibodies. In a cohort of early RA patients (n=286), IgG antibodies directed toward a synthetic citrullinated C1(III) peptide (citC1(III)-P) were detectable with a prevalence of 40.4%. The partial autoantibody cross-reactivity between citC1(III)-P and citrullinated peptides mimicking epitopes of the cytoskeletal autoantigen filaggrin suggests that autoimmunity to cartilage-specific modified self might be a critical intermediate bridging recognition of PAD-modified extra-articular autoantigens with the disruption of tolerance to native cartilage constituents.

B lymphocytes and systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease characterized by B cell hyperactivity in association with autoantibodies, most prominently those directed to components of the cell nucleus. The source of the antigens that drive B cell responses in SLE is unknown, although recent studies suggest mechanisms by which the self-antigens become immunogenic and stimulate responses. Among these mechanisms, abnormalities in the generation of apoptotic cells or their clearance may increase the availability of nuclear antigens to drive responses. In addition, autoantibody crossreactivity may promote induction of responses to disparate antigens, foreign and self, and enable a single autoantibody to cause disease by crossreactive binding. In addition to reflecting increased exposure to self-antigen, autoantibody responses in SLE may result from abnormalities in B cell signaling and regulation by cytokines. New approaches to therapy aim to abrogate autoantibody production by targeting specific steps in B cell activation, including blockade of T cell costimulation.

Thymic Hyperplasia Presenting as Anterior Mediastinal Mass in 2 Patients With Graves Disease

Thymic Hyperplasia Presenting as Anterior Mediastinal Mass in 2 Patients With Graves Disease

Thymic Hyperplasia Presenting as Anterior Mediastinal Mass in 2 Patients With Graves Disease

Graves disease is an autoimmune thyroid condition characterized by the production of autoantibodies against the thyrotropin receptor. The autoantibodies mimic the effect of the hormone on thyroid cells, which stimulates autonomous production of thyroxine and triiodothyronine. It has been hypothesized that cross-reactivity of autoantibodies may result in Graves ophthalmopathy and dermopathy. A seldom-recognized feature of Graves disease is thymic hyperplasia. We report 2 patients with Graves disease and incidentally discovered anterior mediastinal masses presumed to be thymic hyperplasia. In both cases, these masses regressed spontaneously after treatment of hyperthyroidism.

Heparin-related thrombosis despite normal platelet counts in vascular surgery

Background Acute graft thrombosis is a severe complication in vascular surgery that may require limb amputation or even cause death. Because nearly all patients undergoing vascular surgery have had previous exposure to heparin, the presence of heparin-related anti-platelet antibodies typical for heparin-associated thrombocytopenia (HAT) is one underlying possible mechanism of acute graft thrombosis. Although thrombocytopenia is a typical finding of HAT, it is not clear whether the occurrence of clinically important HAT is necessarily associated with thrombocytopenia. Patients and methods Ten out of 246 patients undergoing vascular surgery were diagnosed with HAT because of otherwise unexplained acute graft thrombosis that required recurrent surgical interventions. Results In all of the 10 patients, heparin-related anti-platelet antibodies were detected although the platelet counts were within the normal range. When HAT was diagnosed, heparin administration was stopped and, after autoantibody cross-reactivity with the heparinoid Danaparoid had been excluded, anticoagulation was continued using this anticoagulant. After heparin therapy was discontinued none of the 10 patients developed further thrombotic complications. Conclusion The data presented demonstrate clearly that a normal platelet count does not exclude the possibility of HAT. As a consequence of this, HAT should be suspected in patients who develop thrombotic complications during heparin treatment, regardless of the actual platelet counts.

Dual Reactivity of Several Monoclonal Anti-nucleosome Autoantibodies for Double-stranded DNA and a Short Segment of Histone H3

We have shown previously that four IgG monoclonal autoantibodies (mAbs) reacted in ELISA with both double-stranded (ds) DNA and peptide 83-100 of histone H3. The peptide 83-100 contains a cysteine residue at position 96 and readily dimerizes at pH 7-8. We describe here that only the 83-100 dimers, and not the 83-100 monomers, are recognized by the four antibodies and inhibit in ELISA the binding of mAbs to dsDNA. The equilibrium affinity constants (Ka) and kinetic rate constants of two of these mAbs were measured in a biosensor system. Ka values were significantly higher when these mAbs were tested with dsDNA as compared with the 83-100 dimer. Further higher Ka values were measured with mononucleosomes containing DNA and histones. It is proposed that these four mAbs are directed against a topographic determinant formed by DNA and the region 83-100 of H3 present as a dimer at the surface of nucleosome, and that they react, although significantly less well, with DNA and peptide dimer tested separately. This study provides a quantitative and kinetic basis to interaction between several antibodies and distinct antigenic structures and allows us to better understand the structural basis of apparent autoantibody cross-reactivity.

Emerging concepts regarding B cells and autoantibodies in murine lupus nephritis. B cells have multiple roles; all autoantibodies are not equal.

Despite observations linking the severity of lupus nephritis to the quantity and location of glomerular immune deposits, it had been difficult to decipher the primary role of B cells and autoantibodies in this process. Newer technologies have provided the means to evaluate the roles of whole B cell populations and individual immunoglobulins in lupus lesions. In this review, recent advances in this area are summarized, with particular emphasis on work from the authors' laboratories. The results implicate a primary role for B cells and immunoglobulins in lupus nephritis, including glomerular, interstitial, and vascular lesions. Multiple antibody-ligand interactions participate in glomerular immune deposit formation in individuals with lupus nephritis. Recent evidence suggests that in situ formation of immune deposits by either cross-reactivity of autoantibodies with intrinsic glomerular antigens (i.e., anti-DNA antibodies with laminin) or direct interaction of autoantibodies with circulating autoantigens lodged within glomeruli (i.e., anti-DNA antibodies with histone/DNA). The predominant autoantibody-glomerular antigen interaction(s) in a given individual influences the principal location of immune deposition, which in turn influences the pathologic and clinical expression of disease. It is believed that these phenomena contribute to the phenotypic diversity commonly observed among individuals with lupus nephritis. Furthermore, these consequences are dependent on properties unique to both subsets of lupus autoantibodies and to their target antigen ligands within the glomerulus. Thus, the autoantibody variable or antigen binding region, along with the nature and location of the target glomerular antigen (or site of circulating antigen deposition), are influential in initiating these perturbations.

Sequence homology of the diabetes-associated autoantigen glutamate decarboxylase with coxsackie B4-2C protein and heat shock protein 60 mediates no molecular mimicry of autoantibodies.

Molecular mimicry between viral antigens and host proteins was often suggested to be involved in induction of autoimmune diseases. In type 1 diabetes where pancreatic beta cells are destroyed by autoimmune phenomena, a linear sequence homology between a major autoantigen, glutamate decarboxylase (GAD), and the 2C protein of coxsackie B4 was identified. In addition, a sequence homology between GAD and the mycobacterial heat shock protein 60 was described and the suggestions were made that molecular mimicry between GAD, coxsackievirus B4-2C protein, and/or heat shock protein 60 (hsp60) may be actively involved in an autoimmune reaction towards the pancreatic beta-cells. Our group was the first to isolate human monoclonal autoantibodies to GAD (MICA 1-6) from a patient with newly diagnosed type 1 diabetes. The MICA allowed a detailed characterization of the diabetes associated self-epitopes in GAD and represent a set of GAD autoantibodies present in sera from patients with type 1 diabetes. Using deletion mutants of GAD we demonstrated that the regions of GAD covering the homology sequences to coxsackievirus B4 and to the hsp60 were absolutely required for binding of the MICA to GAD. We now designed an antibody-based analysis to ask whether molecular mimicry between GAD and coxsackie B4-2C or hsp60 is relevant in type 1 diabetes. Since part of the MICA recognize conformational epitopes, they allow to test for conformational molecular mimicry in viruses that have been incriminated in the development of type 1 diabetes. Our data reveal no crossreactivity between the diabetes associated GAD epitopes defined by the MICA and hsp60, rubellavirus, cytomegalovirus, and coxsackie B1-B6 virus antigens. Neither coxsackie B4-specific antibodies in sera from normal individuals nor GAD-positive sera from patients with type 1 diabetes indicated a crossreactivity between coxsackie B4-2C and GAD. Although the regions in GAD homologous to coxsackie B4-2C and hsp60 represented parts of GAD indispensible for binding of diabetes associated autoantibodies they did not mediate a crossreactivity of autoantibodies between GAD and these two proteins. No evidence for molecular mimicry between GAD and a whole panel of foreign antigens was detected by autoantibodies in type 1 diabetes.