Common IgA and IgM rheumatoid factor idiotypes in autoimmune diseases

[Hepatitis A infection and Henoch-Schonlein purpura: a rare association]. Arch Pediatr. 2004;11:1202-1204. [PMID: 15475276 DOI: 10.1016/j.arcped.2004.06.014]

OBSERVATION

A 10-year-old boy presented cholestatic hepatitis A virus infection confirmed by IGM anti-HAV antibody. Three days after admission, he presented a palpable purpuric rash on the declivous regions, arthralgia and abdominal pain. He met all criteria set by the American College of Rheumatology (ACR) for Henoch Schonlein purpura. The evolution was gradually favorable with no renal involvement (recoil of 3 years and half).

CONCLUSION

Henoch Schonlein purpura is an exceptional extra-hepatic manifestation of hepatitis A infection.

Immunological aspects of juvenile rheumatoid arthritis

This article reviews the evidence from recent studies on immunological abnormalities associated with pathophysiologic mechanisms operating in three clinical subtypes of juvenile rheumatoid arthritis (JRA) (polyarticular, pauciarticular and systemic). The main discussion is focused on three hallmarks of immunopathological studies. First, abnormalities in phenotype and function of lymphocytes from peripheral blood and inflamed synovium are discussed. The aberrations of lymphocytes are elucidated by T and B cells expressing phenotypic cell-markers such as CD20, CD21, CD4, CD8 and DR in association with different subtypes and disease activity. The functional imbalance and impairment of T and B cells are mainly observed by abnormal proliferation and/or in vitro Ig production in response to mitogens and alloantigens. Second, because the appearance of rheumatoid factors (RF) in serum indicates that the pathogenesis of JRA may be based on the autoimmune mechanism, the prevalence of RF including IgM, IgA and IgG isotype, hidden IgM RF and cross-reactive idiotype RF, and their characteristic properties are discussed. Moreover, specific auto-antibodies (antinuclear antibodies and others) for JRA are illustrated in this paper. Third, the production of various pro-inflammatory cytokines resulting in the release of tissue-damaging chemical mediators is also discussed. This may play a central role in the generation of systemic inflammation and joint involvement in JRA.

Antiphospholipid antibodies differ in aPL cofactor requirement

Although autoimmune antiphospholipid antibodies (aPL) may require a serum cofactor, beta 2-glycoprotein I (beta 2GPI), for maximal binding in aPL ELISA, it is not known whether cofactor is absolutely required or is merely an enhancing factor for binding, nor is it clear whether aPL bind to cofactor itself, a cofactor-lipid complex, or a phospholipid modified in some way by cofactor. We therefore isolated and purified beta 2GPI and evaluated its relationship to both IgG and IgM aPL binding. aPL derived from different sera appear to have differing requirements for cofactor; the proportion of total binding attributable to cofactor varies from 46% to 95%. aPL do not bind to beta 2GPI in the absence of phospholipid. Enhanced binding to phospholipid is seen if beta 2GPI is provided either before or with the test antibody. Autoimmune aPL bind phospholipid better with human rather than bovine cofactor. The requirement for cofactor is greater for low-avidity aPL as measured in an IgG-human cofactor system. Cofactor requirement alone does not predict the presence or absence of associated clinical complications.

Monoclonal process in primary Sjögren's syndrome and cross-reactive idiotype associated with rheumatoid factor

Monoclonal or oligoclonal B cell products have been described in the sera and urine of patients with primary Sjögren's syndrome (PSS). In addition, monoclonal expansion of plasma cells has been found in the exocrine glands of PSS patients with circulating monoclonal B cell products. The goal of this study was to raise an anti-idiotype to a cryoprecipitable monoclonal IgM kappa rheumatoid factor (RF) from a PSS patient. Using the F(ab')2 fragments of the rabbit IgG anti-idiotype, an idiotype-specific ELISA was developed and sera from 32 patients with PSS (13 with monoclonal IgM kappa), 33 with rheumatoid arthritis, three with rheumatoid arthritis + Sjögren's syndrome (SS), 30 with systemic lupus erythematosus, six with Waldenström's macroglobulinaemia, and 20 healthy controls were tested. The idiotype was primarily found in PSS patients with circulating monoclonal IgM kappa and more often in those who had a ratio of kappa: lambda intracytoplasmically positive plasma cells greater than 3:1 in the lymphocytic infiltrates of minor salivary glands, and systemic manifestations. The idiotype was also found in PSS and rheumatoid arthritis patients without circulating monoclonal cryoglobulins as well as in two of the six patients with Waldenstrom's macroglobulinaemia. Our results suggest that the monoclonal process observed in PSS could involve restricted idiotypic clones that are susceptible to malignant transformation.

Structural characterization of the second major cross-reactive idiotype group of human rheumatoid factors. Association with the VH4 gene family

Rheumatoid factors (RF) are the most common type of functional antibodies among naturally occurring human monoclonal IgM proteins. A large subset of these autoantibodies use structurally homologous light chains of the kappa III subgroup, which bear the 6B6.6 cross-reactive idiotype (CRI). Although antibody binding activity requires both heavy and light chains, information about the heavy chains used by these autoantibodies is limited. To investigate these proteins, the murine monoclonal antibodies, 5-14 and 6-10, were generated by immunization with the heavy chains of the 6B6.6 CRI-positive RF, COR and LEW. These antiidiotypic antibodies reacted with 8 of 11 autoantibodies that coexpressed the 6B6.6 CRI. All 8 RF had heavy chains from the VH4 gene family, as assessed by reactivity with a VH4-specific primary sequence-dependent antibody. The same RF were also identified by the previously described murine monoclonal antiidiotype, LC1. Further experiments revealed that the LC1 antibody delineates a subfamily of VH4 heavy chains that is preferentially used in kappa III-6B6.6 CRI-positive IgM-RF. The cumulative data suggest that 13-22% of RF express both the kappa III-6B6.6 and VH4-LC1 CRI. These findings document that RF autoantibody activity requires specific VL-VH pairing, and that a subset of idiotypically related VH4 heavy chains is commonly expressed in disease-associated monoclonal IgM-RF.

Qualitative and quantitative expression of VHI associated cross reactive idiotopes within IgM rheumatoid factor from patients with early synovitis

Monoclonal rheumatoid factors (RFs) of the major Wa cross reactive idiotype group have been shown to express exclusively VKIII subgroup light chains and VHI subgroup heavy chains. A VKIII associated cross reactive idiotope (CRI) (17-109), however, was shown not to be exclusively expressed on IgM paraproteins having rheumatoid factor activity or to be present at increased levels in the sera of patients with rheumatoid arthritis (RA). Three VHI associated CRIs have been defined with monoclonal antibodies and quantitative studies of their representation are reported, together with VKIII, in IgM and IgM RF isolated from the sera of patients with early synovitis, some of whom progressed to classical RA. The results show (a) the probed CRIs were expressed predominantly on IgM RF rather than on non-RF IgM; (b) 5-10% of IgM RFs from patients with classical RA expressed the CRIs, but this represented a lower proportion of IgM RFs than observed for normal individuals or patients with self limiting synovitis; (c) VKIII light chains were highly associated with IgM RFs rather than non-RF IgM (75% and 25% respectively). It is suggested that the CRIs probed are markers for germline gene encoded antibodies or sequences resulting from minimal mutation of germline genes. The lowered proportion of RFs expressing CRIs in RA may therefore be evidence of polyclonal activation or specific antigenic stimulation, or both, resulting in maturation of the RF response with recruitment of further VH genes or extensive mutation of germline genes. These studies show that monoclonal RFs are relevant models of RF produced in RA and that the repertoire of RF autoantibodies may be encompassed within a small number of CRI expressing families.

Cross-reactive antiidiotypic antibodies against human rheumatoid factors from patients with juvenile rheumatoid arthritis

We prepared antiidiotypic (anti-Id) antibody to 2 polyclonal IgM rheumatoid factors (IgM-RF) and 2 polyclonal "hidden" IgM-RF. The anti-Id antibodies were isolated by chromatography on Sepharose 4B, to which was bound rabbit anti-human IgG Fc fragments. F(ab')2 fragments from the anti-Id antibodies were generated by pepsin digestion and isolated by gel filtration. The anti-Id antibodies directed against RF from 4 patients with juvenile rheumatoid arthritis (JRA) were tested by an inhibition hemolytic assay for cross-reactivity with IgM-RF from 4 adult patients with rheumatoid arthritis, 6 patients with JRA, and 13 JRA patients with hidden RF. The 4 anti-Id antibodies had variable cross-reactivity with the isolated adult RA RF, JRA RF, and JRA hidden RF. Similar results were obtained by a direct-binding enzyme-linked immunosorbent assay for the anti-Id antibodies. The broad pattern of cross-reactivity was apparently unrelated to a particular amino acid sequence, but was associated with the antigen-binding site of IgM-RF. These results suggest the possibility that the anti-Id antibodies prepared against isolated RF obtained from JRA patients bear the "internal image" of antigen; that is, the Fc region of human IgG. These anti-Id antibodies may be generated in JRA patients and may possess specific immunomodulatory properties.

A Subgroup of Rheumatoid Arthritis (RA) Associated with Selective Binding of Rheumatoid Factors to Antigen Structures of Cytomegalovirus (CMV)

We compared antibodies (Ab) with both, antiviral and anti IgG properties in patients with rheumatoid arthritis with malignant progress, short remissions and no improvement to therapy. The selective binding of Rheumatoid Factor (RF) to antigen structures of CMV were tested in 180 patients by a newly established ELISA with antiidiotypic goat antibodies of CMV neutralizing human monoclonal Ab and against the virus antigen directly. Displacement reactions on the idiotypic bindingsite as well as comparative ELISA gave proof of the special RF activity. 24,2% of the patients suffering from RA, with IgM RF, showed selective binding to antigen structures of CMV and anti IgG activity.

The evidence of the specific binding capacity of RF to the virus antigen in chronic CMV infection as well as their defined binding capacity to the Fc Fragment of IgG suggest CMV specific RF as the pathogenetic factor of malignant forms of inflammatory rheumatism.

Cryoglobulinemia: analysis of isotype, idiotype and antibody activity by composite gel electrophoresis and immunoblotting

Improved methods for high resolution composite gel electrophoresis under dissociating conditions and electrophoretic transfer of immunoglobulins (Mr 150,000-1,800,000) to nitrocellulose have been developed. Using these techniques and highly specific antisera to detect either light or heavy chains on nitrocellulose transfers, the immunoglobulin and clonal composition of washed cryoglobulins (3 micrograms each) could be determined within two days. The results were confirmed by isoelectric focusing and immunoblotting of selected samples. In addition, the method was used for detection of an idiotypic determinant and rheumatoid factor activity within components of the cryoglobulins.

Presence of shared idiotypes in serum and immune complexes in patients with IgA nephropathy

Patients with IgA nephropathy often present a large array of antibodies against diet antigens and this disease can be experimentally induced by alimentary antigens. In this report, we have described the isolation from a patient with IgA nephropathy of antibovine serum albumin (BSA)-antibody idiotypes that are specifically recognized by auto-and heteroantiidiotypic antibodies. The fact that antigen (BSA) but not monomeric or aggregated human IgG inhibited the binding of antiidiotypic antibodies to the idiotypes, suggested that the idiotypic determinants are in or near the antigen binding site and that it is not a rheumatoid factor. By means of the heteroantiidiotypic antibodies raised in rabbits we observed the presence of increased levels of shared idiotypes in serum and/or immune complexes (IC) of 48 out of 70 (68.5%) genetically unrelated patients with IgA nephropathy. The close correlation (P less than 0.005) between the presence of IgA-IC, measured by Raji cell assay, and the existence of high levels of serum idiotypes, suggest that a portion of circulating IC could consist of idiotype-antiidiotype. A strong concordance between the presence and levels of idiotypes and the clinical activity, as defined by the existence of haematuria, was also noted. The discrepancies and absence of correlation observed in our study among the levels of anti-BSA antibodies of different classes and serum levels of idiotypes, circulating IC and haematuria could suggest that the antibodies reacting with the heterologous antiidiotypic antibodies could be directed to other more pathogenic antigens than dietary antigens. All together, our results suggest that IgA nephropathy might belong to the group of diseases that occur in susceptible individuals with a limited potential in the immunological response repertoire.

IgM, IgG and IgA rheumatoid factors and circulating immune complexes in patients with AIDS and AIDS-related complex with serological abnormalities

To investigate some humoral aspects which may reflect the involvement of B lymphocytes in the acquired immunodeficiency syndrome (AIDS), we used an enzyme-linked immunoassay (ELISA) to determine the levels of IgM, IgG and IgA rheumatoid factors (RF) in 16 patients suffering from full-blown AIDS and 32 patients with AIDS-related complex (ARC), in the clinical form of lymphoadenopathy syndrome (LAS), compared with 40 healthy, young heterosexual subjects. Both AIDS and ARC patients showed a greater incidence of high IgM RF levels, with mean values significantly higher than controls, but with no differences between the two pathological groups. IgG RF behaviour was similar in the two patient populations and the healthy subjects. IgA RF were significantly raised in AIDS and ARC. Further information on RF was obtained by determination of the immunoglobulin levels of the respective isotypes in the same patients. Mean IgG levels were above normal in AIDS and ARC patients, but the latter group showed a higher incidence of increased values and higher mean levels. The IgA isotype was significantly increased mainly in AIDS patients. The behaviour of IgM was virtually the same in the three groups studied. A difference between AIDS and ARC patients was established by the detection of circulating immune-complexes (IC) by the C1q-binding and CIC-conglutinin assays. IC were significantly high, by both methods, only in the ARC group, but normal or very low in AIDS. These overall findings suggest once again the impairment of B cell function in AIDS, with prevalent hyperactivation in ARC and exhaustion in full-blown AIDS, and apparent preservation, in the latter group, of the antibody responses which are more closely related to the activity of subsets of T helper cells.

Spontaneous and pokeweed mitogen induced production of rheumatoid factor and immunoglobulins in type II essential mixed cryoglobulinaemia

In order to evaluate functional lymphocyte defects in type II essential mixed cryoglobulinaemia (EMC) in vitro production of immunoglobulins (Ig) and rheumatoid factor (RF) has been studied in basal conditions and under pokeweed mitogen (PWM) stimulation in 15 patients and in 17 control subjects. The major finding was a significantly high basal and inducible production of RF by EMC lymphocytes as compared with the RF production in controls, while synthesis of polyclonal Ig was unaffected. A good correlation existed between in vitro production and serum levels of RF. Peripheral blood SmIg+ and Ia+ cells were also significantly increased. The possibility that EMC shares some pathogenetic mechanism with rheumatoid arthritis on the one hand and with lymphoproliferative diseases on the other is considered.

Spectrotypic analysis of IgM and IgA rheumatoid factors

The spectrotypes of IgA and IgM rheumatoid factors (RF) were analysed in whole serum as well as immunoglobulin fractions and purified RF from patients with one of three autoimmune disorders. As predicted from the pI ranges of normal human serum IgM and IgA in agarose, IgM RF had near neutral pIs, whereas IgA RF showed more acidic (lower) pI values. Serum IgA and IgM RF from patients with rheumatoid arthritis or the sicca syndrome showed considerable charge heterogeneity whereas IgM RF from mixed cryoglobulinaemia or rheumatoid vasculitis patients showed monoclonal and oligoclonal banding patterns respectively. Clonotypic analysis was best achieved with isolated light and heavy chains from highly purified RF. The IgA RF spectrotypes from unmodified paired serum and saliva IgA were clearly different whereas after desialation, similar pI values and, in one case, similar spectrotypes were observed. These observations are compatible with the hypothesis that serum and saliva IgA RF are derived from similar clonal precursors. The methods used in these studies may also be of use in the analysis of IgA and IgM antibody diversity in a number of other situations.