IgA rheumatoid factor synthesis by dissociated synovial cells. Characterization and relationship to IgM rheumatoid factor synthesis

Altered Antibody Response to Epstein-Barr Virus in Patients With Rheumatoid Arthritis and Healthy Subjects Predisposed to the Disease. A Twin Study

Objectives: To study Epstein-Barr virus (EBV) antibody patterns in twin individuals with rheumatoid arthritis (RA) and their healthy co-twins, and to determine the heritability of antibody responses against the EBV encoded EBNA1 protein.

Methods: Isotypes of EBNA1 antibodies were measured in 137 RA affected- and 150 healthy twin pairs. We estimated the effect of RA and RA predisposition, anti-citrullinated antibodies (ACPA), IgM rheumatoid factor (RF), the shared epitope (SE) and the PTPN22-T allele (PTPN22) on the level of EBNA1 antibodies. We also determined the heritability of EBNA1 antibody levels.

Results: IgA-EBNA1 antibody levels were increased in twins from RA discordant twin pairs irrespective of RA, ACPA or IgM-RF status. The IgG-EBNA1 antibody level was elevated in healthy co-twins from RA discordant twin pairs but not in RA affected twins. The IgM-EBNA1 antibody level was elevated in both RA twins and their healthy co-twins. The effect of RA on the IgA-EBNA1 antibody level was reversed when SE was present and with no effect of PTPN22. The heritability of IgA-, IgG- and IgM-EBNA1 antibody level was 40.6, 65.5, and 54.3%, with no effect of environment shared by the twins.

Conclusion: EBNA1 antibody levels are distinctively different between patients with RA and healthy subjects but also between relatives of RA strongly predisposed to RA and healthy subjects. The high level of IgA EBNA1 antibodies associated with RA and a family predisposition to RA is attributable to both genetics incl. the shared epitope and environmental variation.

Tertiary Lymphoid Structures: Autoimmunity Goes Local

Tertiary lymphoid structures (TLS) are frequently observed in target organs of autoimmune diseases. TLS present features of secondary lymphoid organs such as segregated T and B cell zones, presence of follicular dendritic cell networks, high endothelial venules and specialized lymphoid fibroblasts and display the mechanisms to support local adaptive immune responses toward locally displayed antigens. TLS detection in the tissue is often associated with poor prognosis of disease, auto-antibody production and malignancy development. This review focuses on the contribution of TLS toward the persistence of the inflammatory drive, the survival of autoreactive lymphocyte clones and post-translational modifications, responsible for the pathogenicity of locally formed autoantibodies, during autoimmune disease development.

IgM and IgA rheumatoid factors purified from rheumatoid arthritis sera boost the Fc receptor- and complement-dependent effector functions of the disease-specific anti-citrullinated protein autoantibodies

Rheumatoid factors (RF) and the disease-specific anti-citrullinated protein autoantibodies (ACPA) coexist in the joints of rheumatoid arthritis (RA) patients where they probably contribute to synovitis. We investigated the influence of IgM and IgA RF on the FcR- and complement-dependent effects of ACPA immune complexes (ACPA-IC). When stimulated by ACPA-IC formed in the presence of IgM RF or IgA RF fractions purified from RA serum pools, M-CSF-generated macrophages skewed their cytokine response toward inflammation, with increases in the TNF-α/IL-10 ratio and in IL-6 and IL-8 secretion, and decreases in the IL-1Ra/IL-1β ratio. In the IgM RF-mediated amplification of the inflammatory response of macrophages, the participation of an IgM receptor was excluded, notably by showing that they did not express any established receptor for IgM. Rather, this amplification depended on the IgM RF-mediated recruitment of more IgG into the ACPA-IC. However, the macrophages expressed FcαRI and blocking its interaction with IgA inhibited the IgA RF-mediated amplification of TNF-α secretion induced by ACPA-IC, showing its major implication in the effects of RF of the IgA class. LPS further amplified the TNF-α response of macrophages to RF-containing ACPA-IC. Lastly, the presence of IgM or IgA RF increased the capacity of ACPA-IC to activate the complement cascade. Therefore, specifically using autoantibodies from RA patients, the strong FcR-mediated or complement-dependent pathogenic potential of IC including both ACPA and IgM or IgA RF was established. Simultaneous FcR triggering by these RF-containing ACPA-IC and TLR4 ligation possibly makes a major contribution to RA synovitis.

Synovial fluid levels of anti-cyclic citrullinated peptide antibodies and IgA rheumatoid factor in rheumatoid arthritis, psoriatic arthritis, and osteoarthritis

OBJECTIVE

To assess the levels of anti-cyclic citrullinated peptide (anti-CCP) and IgA rheumatoid factor (IgA-RF) in synovial fluids of patients with rheumatoid arthritis (RA), psoriatic arthritis (PsA), and osteoarthritis (OA).

METHODS

Knee effusions of 29 patients with RA (23 women, 6 men; mean +/- SD age 60 +/- 15 years), 20 with PsA (6 women, 14 men; mean age 51 +/- 12 years), and 19 with OA (9 women, 10 men; mean age 73 +/- 11.8 years) were aspirated, tested for white blood cell (WBC) counts, centrifuged, and stored at -20 degrees . Sera of 22, 11, and 12 of these patients with RA, PsA, and OA, respectively, were similarly stored. IgG anti-CCP and IgA-RF were detected by enzyme-linked immunosorbent assay. Erythrocyte sedimentation rate and C-reactive protein levels were used as measures of disease activity.

RESULTS

Mean levels of synovial fluid anti-CCP and IgA-RF were significantly increased in RA joint effusions compared with PsA and OA (anti-CCP: 150 +/- 134, 34 +/- 29, and 24 +/- 26 units, respectively [P < 0.003]; IgA-RF: 76 +/- 77, 15.7 +/- 10, and 18 +/- 20 units, respectively). No significant difference was noted between OA and PsA. A significant correlation was found between synovial fluid anti-CCP and serum anti-CCP and IgA-RF. In patients with RA, a significant correlation was found between synovial fluid WBC counts and IgA-RF (P = 0.03) and serum IgA-RF (P = 0.008), but not between synovial fluid and serum anti-CCP levels. In RA patients, C-reactive protein correlated with serum IgA-RF.

CONCLUSION

Anti-CCP and IgA-RF were significantly increased in synovial fluid of RA in comparison with PsA and OA patients.

In the rheumatoid pannus, anti-filaggrin autoantibodies are produced by local plasma cells and constitute a higher proportion of IgG than in synovial fluid and serum

IgG anti-filaggrin autoantibodies (AFA) are the most specific serological markers of rheumatoid arthritis (RA). They include the so-called 'anti-keratin antibodies' (AKA) and anti-perinuclear factor (APF), and recognize human epidermal filaggrin and other (pro)filaggrin-related proteins of various epithelial tissues. In this study we demonstrate that AFA are produced in rheumatoid synovial joints. In 31 RA patients, AFA levels were assayed at equal IgG concentrations in paired synovial fluids (SF) and sera. AFA titre-like values determined by indirect immunofluorescence and immunoblotting and AFA concentrations determined by ELISA were non-significantly different in serum and SF, clearly indicating that AFA are not concentrated in SF. In contrast, we demonstrated that AFA are enriched in RA synovial membranes, since the ELISA-determined AFA in low ionic-strength extracts of synovial tissue from four RA patients represented a 7.5-fold higher proportion of total IgG than in paired sera. When small synovial tissue explants from RA patients were cultured for a period of 5 weeks, the profile of IgG and AFA released in the culture supernatants was first consistent with passive diffusion of the tissue-infiltrating IgG (including AFA) over the first day of culture, then with a de novo synthesis of IgG and AFA. Therefore, AFA-secreting plasma cells are present in the synovial tissue of RA patients and AFA can represent a significant proportion of the IgG secreted within the rheumatoid pannus.

The B cell repertoire of patients with rheumatoid arthritis. II. Increased frequencies of IgG+ and IgA+ B cells specific for mycobacterial heat-shock protein 60 or human type II collagen in synovial fluid and tissue

OBJECTIVE

A qualitative and quantitative analysis of the functional, antigen-specific B cell receptor repertoire of patients with rheumatoid arthritis (RA) in synovial and peripheral compartments.

METHODS

B cells were activated to grow and differentiate at high efficiency in vitro under limiting-dilution conditions. Isotype and specificity of the secreted Ig were tested by enzyme-linked immunosorbent assay.

RESULTS

In contrast to peripheral B cells, most synovial B cells had already switched to IgG/IgA in vivo. The frequencies of B cells specifically recognizing foreign antigens were decreased within the synovial population, whereas the frequencies of B cells specific for type II collagen, mycobacterial heat-shock protein 60 (hsp60), or IgG Fc fragments were significantly increased, revealing a negative correlation in terms of frequencies.

CONCLUSION

B cells specific for human type II collagen, hsp60, and IgG Fc fragments are produced and/or expanded locally within the affected joints of RA patients. Thus, the specific immune system is definitely involved in the local inflammatory and destructive processes.

Galactose-deficient IgA1 in sera of IgA nephropathy patients is present in complexes with IgG

IgA1 proteins from sera of patients with IgA nephropathy (IgAN) are galactosylated to a lesser degree than those from healthy controls. The increased reactivity of intact or de-sialylated serum IgA1 with N-acetylgalactosamine (GalNAc)-specific lectins, Helix aspersa (HAA) and Caragana arborescens (CAA) and de-sialylated IgA1 with Helix pomatia (HPA) and Bauhinia purpurea (BPA) indicated that the Gal deficiency is in glycans located in the hinge region of IgA1 molecules. De-sialylated IgA from sera of 81 IgAN patients bound biotin-labeled lectin HAA more effectively than did de-sialylated IgA from 56 healthy controls (P < 0.0001). Similar results were observed for 67 IgAN patients and 52 controls with second lectin, CAA (P < 0.001). The binding patterns for 9 patients with mesangial proliferative glomerulonephritis of non-IgA origin were similar to those for controls. Incompletely galactosylated IgA1 capable of binding GalNAc-specific lectins was detected in complexes with IgG as demonstrated by ELISA, size-exclusion chromatography and sucrose gradient ultracentrifugation. The formation of IgA1-IgG complexes may affect the serum level of IgA1 by reducing the rate of its elimination and catabolic degradation by the liver.

Somatic mutation and CDR3 lengths of immunoglobulin kappa light chains expressed in patients with rheumatoid arthritis and in normal individuals

Immunoglobulin secretion by plasma cells infiltrating synovial membranes is a prominent feature of RA. Previous analyses of a cDNA library generated from synovium of RA patient BC revealed immunoglobulin kappa light chain transcripts with extensive somatic mutation, frequent N region addition, and unexpected variation in the lengths of CDR3 regions which form the center of the antigen binding site. To determine if these characteristics are present in other individuals, we performed reverse transcription-polymerase chain reaction amplification and sequenced > or = 10 V kappa-containing amplicons from nine tissue samples: synovia of three individuals with long-standing RA (including patient BC), PBLs of two of these individuals, and PBLs or splenocytes of four normal individuals. Increased levels of somatic mutation in PBLs appeared to correlate with increased age, which may reflect accumulation of circulating memory cells and/or decreased bone marrow production of naive B lymphocytes. Two of three RA synovial samples and both RA PBL samples exhibited increased proportions of clones with unusual CDR3 lengths. Enrichment for these antibody binding sites could be due to abnormal regulation of the emerging repertoire or to selection for B lymphocytes bearing antibodies of unusual specificity, and may play a role in the pathogenesis of RA.

Evidence for differential effects of sulphasalazine on systemic and mucosal immunity in rheumatoid arthritis

OBJECTIVE

To study the effects of sulphasalazine (SASP) on the systemic and mucosal humoral immune systems in patients with rheumatoid arthritis (RA).

METHODS

Serum concentrations of interleukin 6 (IL-6), class and subclass specific IgG, IgA and IgM, IgA and IgG antigliadin antibodies and rheumatoid factors (RF) of IgG, IgA (including IgA1 and IgA2 subclasses) and IgM isotypes were measured before and 16 weeks after sulphasalazine (SASP) therapy in 15 female and three male patients with RA. Amounts of immunoglobulins in saliva and jejunal fluid were measured as estimates of mucosal humoral immunity.

RESULTS

Serum concentrations of IgA and IgG decreased significantly during SASP therapy and correlated with reduced concentrations of IL-6. In addition, levels of circulating IgA RF, IgA anti-gliadin antibodies and IgM RF decreased significantly after the treatment. In contrast, immunoglobulin levels in saliva and jejunal fluid were unaltered.

CONCLUSION

SASP exerts powerful but selective inhibitory effects on systemic immunoglobulin production, whereas no effects on mucosal immunoglobulin production were observed. The decreased systemic B cell activity may be mediated by downregulation of the production of IL-6, a cytokine with Ig switching properties.

Discovery of endogenous catecholamines in lymphocytes and evidence for catecholamine regulation of lymphocyte function via an autocrine loop

Evidence has been obtained that catecholamines and their metabolites are present in single lymphocytes and extracts of T- and B-cell clones by use of capillary electrophoresis with electrochemical detection. Pharmacological inhibition of tyrosine hydroxylase reduces observed catecholamine levels, suggesting catecholamine synthesis by lymphocytes. Intracellular dopamine levels are shown to be increased by extra-cellular dopamine, suggesting a cellular-uptake mechanism. Furthermore, incubation with either dopamine or L-dihydroxyphenylalanine, a precursor of dopamine, results in a dose-dependent inhibition of lymphocyte proliferation and differentiation. Together, these results suggest the presence of an autocrine loop whereby lymphocytes down-regulate their own activity.

Associations of IgA and IgA-rheumatoid factor with disease features in patients with rheumatoid arthritis

In previous studies we have shown that levels of IgM-rheumatoid factor (RF) in plasma and peripheral blood mononuclear cell supernatants are correlated with disease activity and response to second-line therapy in patients with rheumatoid arthritis (RA). The present studies were designed to examine whether IgA-RF levels are also correlated with clinical features of this disease. Two groups of RA patients were studied. Group I consisted of 87 patients in whom extensive clinical data had been collected. Group II included nine patients beginning treatment with gold or methotrexate who were studied during the first year of therapy. Measurement of IgM, IgA, IgM-RF and IgA-RF in culture supernatants and plasma was done by an ELISA method. These data were examined for correlations with clinical and laboratory features. Levels of IgA-RF in supernatants and plasma were found not to be correlated with disease features in the cross-sectional analysis of Group I patients, while IgM-RF and total IgA levels did show significant clinical correlation. Treatment of Group II patients with gold or methotrexate was associated with significant decreases in plasma levels of total IgA and IgM-RF as well as a small but statistically significant decrease in plasma IgA-RF. Plasma levels of total IgM were not altered during therapy. These findings suggest that production of IgA but not IgA-RF is correlated with disease status in patients with RA.

Evidence of antigen receptor-influenced oligoclonal B lymphocyte expansion in the synovium of a patient with longstanding rheumatoid arthritis

Plasma cell infiltration of synovium is common in longstanding rheumatoid arthritis (RA). The mechanism(s) underlying synovial B cell proliferation remains unclear. One theory invokes nonspecific polyclonal stimuli; another implicates antigen as the driving force. Antigen-driven repertoires are characteristically enriched for related sets of V gene segments containing similar sequence in the antigen binding site (complementarity-determining regions; CDRs). To study the forces shaping B cell proliferation, we analyzed V kappa transcripts expressed in the synovium of an RA patient. We found Humkv325, a developmentally regulated V kappa III gene segment associated with autoantibody reactivity, in > 10% of randomly-chosen synovial C kappa cDNAs. Two sets of sequences contained identical charged amino acid residues at the V kappa-J kappa join, apparently due to N region addition. We generated "signature" oligonucleotides from these CDR3s and probed PCR amplified V kappa products from the synovium and PBLs of the same patient, and from PBLs and spleen of individuals without rheumatic disease. Significant expression of transcripts containing these unique CDR3 sequences occurred only in the patient's synovium. Thus, in this synovium there is expansion of a limited set of B cell clones expressing antigen receptors that bear evidence of antigen selection.

Rheumatoid factor production by mononuclear cells derived from different sites of patients with rheumatoid arthritis

To investigate the origin of circulating rheumatoid factor (RF) and the relation between RF production at different sites in patients with rheumatoid arthritis (RA), mononuclear cells derived from bone marrow, synovium and peripheral blood of patients with RA were examined for the presence of plasma cells and for their capacity to produce RF and other immunoglobulins in vitro. Analysis of culture supernatants for the presence of immunoglobulins demonstrated that cells derived from bone marrow, synovium and peripheral blood were all found to be capable of producing every immunoglobulin and RF isotype investigated. No significant correlations were found between concentrations of immunoglobulin isotypes produced by cells derived from different sites of one individual. Significant correlations were found, however, between concentrations of RF isotypes produced by cells derived from the three sites. These results indicate that the production of RF in the different compartments is not an autonomously regulated process. Mononuclear cells derived from bone marrow were found to be able to produce RF in similar quantities to cells dissociated from synovial tissue. In combination with the fact that circulating immunoglobulins are produced mainly in the bone marrow, this observation suggests that bone marrow is also a major source of circulating RF.

Use of a chimeric monoclonal anti-CD4 antibody in patients with refractory rheumatoid arthritis

OBJECTIVES

To evaluate the safety, immunogenicity, and biologic effects of chimeric monoclonal anti-CD4 (cM-T412) in patients with refractory rheumatoid arthritis (RA), and to obtain preliminary data on the clinical response to this treatment.

METHODS

Twenty-five patients with active refractory RA were treated with incremental doses (10 to 700 mg) of cM-T412 in an open-label, escalating-dose phase I trial.

RESULTS

Infusion with cM-T412 was followed by an immediate, rapid decline in CD4+ T cells. The level of circulating CD4+ T cells remained depressed in most patients even at 6 months posttreatment. Following antibody infusion, proliferative responses of peripheral blood lymphocytes to mitogens and antigens were determined; mitogen and antigen responses were decreased compared with pretreatment responses. Mitogen responses tended to return to baseline values more rapidly than did responses to antigen. Adverse events included fever (19 patients), which was associated with myalgias, malaise, and asymptomatic hypotension; these symptoms were self-limited and appeared to correlate with transient elevations in interleukin-6. No significant human antibody response to the cM-T412 variable region was detected; only 2 patients developed transiently low levels of antibodies reactive with cM-T412. Significant clinical improvement, defined as > or = 50% decrease in tender joint counts compared with baseline, was noted in 43% of patients at 5 weeks and 33% at 6 months following cM-T412 infusion.

CONCLUSIONS

Treatment of refractory RA with cM-T412 appears to be safe and is associated with sustained decreases in circulating CD4+ T cell counts and depressed in vitro T cell responses. No significant human antichimeric antibody response was detected. Nonblinded assessment of clinical end points suggests that treatment with cM-T412 may have beneficial effects in these patients with refractory RA. A double-blind clinical trial is warranted to determine its clinical efficacy in treating RA.

IgA rheumatoid factor in mucosal fluids and serum of patients with rheumatoid arthritis: immunological aspects and clinical significance

In order to gain insight into the production and clinical significance of IgA rheumatoid factor (IgA-RF) in mucosal fluids of patients with rheumatoid arthritis (RA), we examined tear fluid, saliva and serum from 80 patients with RA. Significant correlations were found between IgA-RF levels in tear fluid and saliva (P = 0.002, r = 0.57), saliva and serum (P < 0.001, r = 0.79), and serum and tear fluid (P < 0.001, r = 0.31). No significant correlations were found between total IgA levels in these fluids. Comparison between circulating and mucosal IgA-RF levels after correction for total IgA, revealed that mucosal IgA-RF levels are on average 2.5 times higher than circulating IgA-RF levels. Analysis of IgA-RF specificity showed that lacrimal and salivary IgA-RF reactivity with various IgG subclasses is similar and differs from serum IgA-RF specificity. These results indicate local production of IgA-RF in salivary and lacrimal glands and support the view of a common origin of IgA-RF producing B cells present in mucosal tissues. Mucosal and circulating levels of IgA and IgA-RF were not associated with tests that quantify tear fluid production. This indicates that mucosal and circulating levels of IgA and IgA-RF in patients with RA cannot be regarded as markers for the development of secondary Sjögren's syndrome.

The immunoglobulin kappa light chain repertoire expressed in the synovium of a patient with rheumatoid arthritis

OBJECTIVE

To analyze the nature of the B cell response in the synovial tissue of a patient with rheumatoid arthritis (RA). Specifically, we sought to determine if the pattern of immunoglobulin expression was consistent with polyclonal stimulation of B cells or an antigen-driven response.

METHODS

We generated an unrestricted complementary DNA (cDNA) library from the diseased synovium of a rheumatoid factor (RF)-positive patient with an 18-year history of RA. A random sample of kappa light chain recombinants was identified, and sequence analysis was performed. The variable domains were compared with an extensive database of germline and cDNA kappa sequences.

RESULTS

We found a light chain repertoire enriched for kappa transcripts containing 2 V kappa gene segments (Humkv325 and Humkv328) that are frequently associated with paraproteins expressing RF activity. Kappa variable domains from synovium contained numerous somatic mutations which resulted in frequent replacement of amino acids that encode the classic antigen-binding site. Unexpectedly, many of these kappa transcripts contained non-germline-encoded nucleotides (N regions) at the site of V kappa-J kappa joining. The combination of N-region addition and variation in the sites of V kappa-J kappa splicing generated unusually long complementarity-determining region 3 regions and charged amino acids near the V kappa-J kappa splice site.

CONCLUSION

The pattern of somatic mutations found in this patient sample supports the hypothesis that these synovium-derived plasma cells are the product of immunoglobulin receptor-dependent (i.e., antigen-driven) selection. The extent of N-region addition raised the additional possibility that these antibodies derive from an unusual set of B lymphocytes that have escaped normal regulation.

A prospective clinical five year follow up study after open synovectomy of the knee joint in patients with chronic inflammatory joint disease. The prognostic power of clinical, arthroscopic, histologic and immunohistologic variables

Arthroscopy and clinical examination was performed on the knee joint of 26 patients with chronic inflammatory joint disease, before and at 6 and 12 months after open synovectomy. Biopsies were examined by histologic and immunohistologic methods. Clinically the patients improved until 6 months after synovectomy, and the improvement was maintained for 5 years. Patients with the best clinical function prior to synovectomy also had the best long term results (p = 0.024). The state of the cartilage was the best predicting variable with a significant prognostic power (p = 0.01). Thus patients with normal cartilage at the time of synovectomy had the best clinical score five years later. The patients with most resynovitis 12 months after surgery did less well at five year clinical follow up (p = 0.032) than those with little or no resynovitis. Absence or low number of IgA-positive plasma cells in the cellular infiltrate at 12 months after surgery correlated with a good clinical score five years after surgery (p = 0.036). This suggests that a high number of IgA-positive plasma cells may be indicative of a more aggressive, destructive disease.

Subclass distribution and size of human IgA rheumatoid factor at mucosal and nonmucosal sites

Elevated serum levels of IgA, IgA1, and IgA2 rheumatoid factors (RF) were demonstrated by enzyme-linked immunosorbent assay in 69%, 73%, and 36%, respectively, of 100 patients with rheumatoid arthritis (RA), whereas fewer than 5% of 100 healthy donor sera contained elevated levels of these RFs. In serum samples from 125 controls with 4 different chronic diseases (systemic lupus erythematosus, ankylosing spondylitis, bronchial asthma, and polyarteritis nodosa), levels of IgA-, IgA1-, and IgA2-RF were found to be increased in 7%, 7%, and 8%, respectively. Comparison of RF levels in samples of serum, synovial fluid (SF), and saliva from RA patients indicated local production of both IgA-RF subclasses in salivary glands and in synovial tissue. Significant positive correlations were found between levels of IgA-RF subclasses in SF and serum, but not in serum and saliva or in SF and saliva. Fractionation of serum, SF, and saliva from patients with RA (by high performance liquid chromatography under acidic conditions) demonstrated that both IgA subclasses with RF activity occur mainly in fractions that also contain IgM. The results of this study show that 1) IgA-RF in serum and SF is mainly of IgA1 subclass, 2) both IgA-RF subclasses are produced locally in salivary glands and in synovial tissue, 3) the production of both IgA-RF subclasses at mucosal and nonmucosal sites is independent from each other, and 4) both IgA-RF subclasses occur predominantly in polymeric form in serum, SF, and saliva in RA patients.

Evidence for locally synthesized and clonally restricted immunoglobulin in the synovial fluid from rheumatoid arthritis patients

In this study, we examined the immunoglobulin (Ig) present in synovial fluid (SF) from patients with rheumatoid arthritis (RA) to determine if it was locally produced and to assess the presence of clonally restricted (oligoclonal) immunoglobulin. We studied SF/serum pairs from 55 RA patients and 23 patients with degenerative joint disease (DJD). We found increases in total protein, IgG, IgA, and IgM in RA vs DJD SF (P less than 0.01). The immunoglobulin present in RA appeared to be locally produced as evidenced by significant increases (P less than 0.01) in the immunoglobulin indices. Regression analysis among the levels of IgG, IgA, and IgM RF and the Ig indices suggested that only a minority of the locally synthesized Ig present was specific for RF. To provide evidence of clonal restriction, we further analyzed the SF specimens by isoelectric focusing and assessed the presence of oligoclonal bands present only in RA SF. In 7/55 RA specimens (13%) we found unique SF IgG bands. All bands were of similar isoelectric point (pI), being quite cathodic with pI greater than 7.5. Our evidence supports synthesis of Ig within RA synovium, with a minority of patients showing prominent and unique SF Ig bands. This suggests an oligoclonal response in SF of some patients, but polyclonal Ig synthesis in most.

Correlation of anti-cytoskeleton antibody activities in synovial fluid with interleukin-6 in patients with osteoarthritis and inflammatory joint disease

Synovial fluids and sera from patients with rheumatoid arthritis, psoriatic arthritis, yersinia arthritis, Behçet's syndrome, Crohn's disease, and osteoarthritis were tested for antinuclear antibodies and antibodies to five cytoskeletal components in sensitive enzyme-linked immunosorbent assay (ELISA) systems and for IL-6 concentrations in a proliferation assay (IL-6 dependent hybridoma cell line B13.29, subclone B9). Statistically significant correlations between antibody activities and IL-6 levels were found for vimentin antibodies (r = 0.56; p less than 0.05) and actin antibodies (r = 0.44; p less than 0.05). In patients with chronic and active disease like rheumatoid arthritis and psoriatic arthritis, optical densities measured by vimentin- and actin-ELISA were significantly different from those measured in patients with osteoarthritis. To date only a few reports exist concerning the incidence of antibodies in synovial fluids. We have shown to our knowledge for the first time that IL-6 seems to induce synovial fluid antibody activities restricted to cytoskeletal components of synoviocytes (i.e., vimentin and actin). Synovial fluid antibody activities against vimentin and actin appear to be markers of activity in patients with inflammatory joint disease.

Lymphocyte infiltration and the synthesis of IgM and IgA rheumatoid factors by rheumatoid synovial membrane

IgM and IgA rheumatoid factor (RF) synthesis by synovial membrane mononuclear cells was measured in 14 patients with rheumatoid arthritis (RA). The results were compared with blood mononuclear cell cultures and correlated with the intensity of lymphocyte infiltration of the synovium. IgM RF was produced by all synovial cultures compared with 56% of blood cultures; IgA RF was produced by 86% of synovial cultures and by 21% of blood cultures. A correlation was observed between synovial IgM RF synthesis, but not IgA RF synthesis, and the intensity of T cell and B cell infiltration of the synovial membrane.

IgG and IgA subclass distribution of total immunoglobulin and rheumatoid factors in rheumatoid tissue plasma cells

The subclass distribution of IgG and IgA plasma cells, and in IgG and IgA rheumatoid factor (RF) producing cells was studied in sections of synovial tissue from seropositive RA and various types of seronegative arthritis, including ankylosing spondylitis, psoriatic arthritis, and Reiter's syndrome. The study was performed with immunofluorescence technique and monoclonal IgG and IgA subclass specific antibodies. IgG RF producing cells were identified by their ability to bind and activate factors both in the early (C3) and late (C5b-9) part of the complement cascade. IgA RF cells were identified by double staining experiments with heat-aggregated IgG and monoclonal antibodies to IgA subclasses. In 23 tissues tested for total IgG, IgG1 cells were usually predominant, while the frequency of IgG3 cells was usually higher than that of IgG2. In 19 tissues also tested for IgA, both IgA subclasses were present in all tissues. IgA1 plasma cells were always predominant, with a mean ratio of IgA1 to IgA2 cells of approximately 10. In the 13 tissues tested for RF-producing cells, the highest frequency of IgG RF cells was found among the IgG3 cells, followed by IgG1 and IgG2. IgA RF cells were found in only one case, all cells being IgA1.

Secretion of antibodies to types I and II collagen by synovial tissue cells in patients with rheumatoid arthritis

Production of antibodies to IgG and to type I and type II collagen (CI and CII) was analyzed by enzyme-linked immunospot assay in patients with rheumatoid arthritis (RA) and patients with other inflammatory or degenerative joint diseases. Anti-CII-secreting cells, generally in high numbers, were found among mononuclear cells eluted from inflamed synovial tissue in 12 of 13 patients with seropositive RA and 9 of 14 patients with seronegative RA or with undetermined serum rheumatoid factor levels. In contrast, no anti-CII-producing B cells were present among synoviocytes from 4 patients with other joint diseases. In none of 7 RA sera did we find significant levels of anti-CII. Synovial B cells secreting antibodies specific for CI were observed less frequently in patients with RA. These results indicate that measurement of serum antibody levels is not adequate to assess actual autoantibody production in rheumatoid joints and that local autoimmune reactions to CII are common in RA, which implies that collagen-reactive T cells are present within the inflamed joints of RA patients. The possible role of a local collagen autoimmunity in RA is discussed, particularly in relation to its putative role in rheumatoid factor production.

Importance of intestinal mucosal immunity and luminal bacterial cell wall polymers in the aetiology of inflammatory joint diseases

The distal intestine contains bacterial cell wall polymers capable of inducing acute and chronic polyarthritis if systemically distributed. Parenteral injection of peptidoglycan-polysaccharide (PG-PS) polymers from certain bacterial species produces spontaneously relapsing erosive synovitis in susceptible rat strains, and normally subarthropathic amounts of PG-PS and lipopolysaccharide (endotoxin) can reactivate arthritis initially induced by PG-PS. These experimental results illustrate the inflammatory potential of luminal bacterial products and the importance of genetically determined host susceptibility factors in the pathogenesis of arthritis. Normally, luminal complexing by secretory IgA and an intact epithelial barrier limits uptake of luminal antigen; however, intestinal inflammation enhances mucosal uptake and systemic distribution of potentially injurious macromolecules, including PG-PS and lipopolysaccharide. Occult intestinal inflammation, which may be related to non-steroidal anti-inflammatory drugs or may be disease-associated, occurs in approximately two thirds of patients with rheumatoid arthritis, idiopathic reactive arthritis and ankylosing spondylitis. Enhanced mucosal permeability to macromolecules occurs in rheumatoid arthritis, enteric infections and idiopathic inflammatory bowel disease. Intestinal inflammation is associated with increased mucosal IgG production and circulating immune complexes. Hyperactive IgA synthesis occurs in many types of inflammatory joint disease. Polyclonal IgA is increased in rheumatoid arthritis, Sjögren's syndrome, ankylosing spondylitis, Reiter's syndrome, and reactive arthritis following Yersinia infection. Anti-Klebsiella IgA cross-reacts with HLA-B27 antigen, and antibodies to enteric bacteria are able to lyse lymphocytes from HLA-B27 patients with ankylosing spondylitis. Anti-Yersinia IgA is produced at the mucosa in increased quantities in patients who develop arthritis following Yersinia enteritis, possibly as a consequence of defective cellular immunity. Serum concentrations of IgA correlate with activity of rheumatoid arthritis and ankylosing spondylitis, and serum IgA immune complexes are associated with rheumatoid vasculitis, suggesting that IgA contributes to the pathogenesis of arthritis. We speculate that intestinal injury may also induce or perpetuate arthritis by systemic distribution of inflammatory mediators produced by intestinal immune effector cells.

Local production of IgA- and IgM-rheumatoid factors in adult periodontal disease

The enzyme-linked immunospot assay was used to enumerate both the number and the frequency of spontaneous IgG, IgA, and IgM immunoglobulin-secreting cells and IgA- and IgM-rheumatoid factor (RF)-producing cells present in the gingivae and peripheral blood of adult periodontitis patients. Cells from 29 patients were incubated on plates coated with human IgG, Fc, or F(ab')2 fragments and on plates coated with class-specific anti-human antibodies and secreted antibodies were subsequently visualized by means of an immunoenzymatic procedure. The data indicate that (1) IgA-RF- and IgM-RF-secreting cells are frequently present in the gingiva of adult periodontitis patients; (2) production of RF in gingivae of adult periodontitis patients occurs in the absence of demonstrable RF production by simultaneously obtained peripheral blood mononuclear cells, suggesting that local autoimmune reactions may occur in this disease; and (3) lack of correlation between IgA-RF and IgM-RF production in diseased gingiva suggests that the two RF isotypes are regulated independently of each other.

Occurrence of polymeric IgA1 rheumatoid factor in the acquired immune deficiency syndrome

The sera of 34 acquired immune deficiency syndrome (AIDS) patients and 20 healthy male homosexuals were examined for the presence of elevated levels of IgA and IgM rheumatoid factor (RF) and compared with results obtained with sera from 23 healthy laboratory volunteers. IgA RF levels were elevated (greater than 3 standard deviation units) in 9 of 34 (26%) patients with AIDS as compared to the panel of laboratory controls. Levels of IgM RF did not differ significantly in the AIDS patients and in the controls. There were no differences in levels of either IgA RF or IgM RF when the homosexual controls were compared with the laboratory volunteers. Sucrose-gradient ultracentrifugation experiments and assays using monoclonal reagents specific for IgA subclasses indicated that the IgA RF was predominantly of the polymeric configuration and restricted to the IgA1 subclass, respectively. Polyethylene glycol (PEG) precipitates of serum enriched for circulating immune complexes (CIC) were also assayed for the presence of IgA RF and IgM RF. Although levels of IgA RF in serum and in PEG precipitates did not correlate with levels of IgA- or IgA/IgG-containing CIC in AIDS patients, levels of IgA RF in both serum and CIC-enriched material were significantly elevated in the AIDS population when compared with the control panel. In contrast, levels of IgM RF in both serum and CIC-enriched material were low and not significantly different from those in healthy controls. These results indicate that both IgA-containing CIC and IgA RF occur in many AIDS patients and raise the possibility that IgA RF may contribute significantly to the formation of immune complexes in this disease.

Rheumatoid factors in Yersinia-triggered reactive arthritis

Total rheumatoid factor (RF) activity and RF isotypes were measured in the sera of 33 patients with Yersinia infection using enzyme-linked immunosorbent assay. Twenty out of 33 patients developed reactive arthritis as a postinfectious complication. Yersinia infection does not seem to stimulate formation of RFs. The serum samples were practically negative, except two consecutive samples of one patient with Yersinia enterocolitica 0:3 triggered reactive arthritis which were strongly positive for all RFs tested. Although in Yersinia triggered reactive arthritis continuous response against Yersinia is seen, especially in the form of persisting IgA response, RF do not seem to be involved.

Relation between bone erosions and rheumatoid factor IgA and IgM isotypes in recent onset rheumatoid arthritis

In this prospective study 58 patients with early rheumatoid arthritis were followed up for two years with six-monthly assessments including rheumatoid factors (RF) of IgA and IgM subtypes. Initial and mean serum levels of IgA-RFs were raised in patients with an erosive disease course in comparison to non erosive disease. The cases with initially increased serum levels of RFs of both isotypes developed more eroded joints in their hands and feet during the study period than the rest of the patients. None of the differences, however, were statistically significant. Of the tested parameters only clinical rheumatoid activity (Mallya-index) was significantly related to the number of eroded joints during the follow-up. We conclude that serum IgA-type RFs are raised in erosive RA, but the determination of RFs of any kind cannot be used to prognosticate erosiveness.

IgA immune complexes in patients with dermatitis herpetiformis occur in the absence of IgA rheumatoid factor

Thirty to forty percent of patients with dermatitis herpetiformis (DH) have IgA-containing circulating immune complexes (IgA-CIC); however, the antigenic composition of these complexes as well as the role they play in the pathogenesis of DH are unknown. The failure to detect wheat protein in these IgA-CIC, despite the association of DH with gluten-sensitive enteropathy, suggests that the IgA-CIC in DH may be similar to those seen in the IgA nephropathies and represent IgA rheumatoid factor (RF)-IgG complexes. We have examined the sera of 32 patients with DH, 16 non-DH patients positive for RF by latex fixation, and 15 normal subjects for IgA and IgM RF using enzyme-linked immunosorbent assays (ELISAs) and for IgA-CIC using an anti-C3 ELISA. Thirteen of 16 (81%) latex fixation test-positive patients had IgA RF by ELISA and 15/16 (94%) had IgM RF by ELISA. The total amount of RF detected by the ELISA (IgA + IgM RF) correlated with the latex fixation titer (r = 0.678, p = 0.004) in these latex fixation-positive patients. Six of the 16 (38%) latex fixation-positive patients also were found to have IgA-CIC. Solid phase absorption using goat antihuman C3 decreased the levels of immune complexes but not the level of IgA RF, suggesting the IgA-CIC detected do not represent uncomplexed IgA RF. In contrast, although 12 of 31 (39%) patients with DH had IgA-CIC ranging in amount from 0.331-26.0 micrograms IgA/ml (nl less than 0.150 microgram IgA/ml), only 1 of 32 (3%) DH patients had detectable levels of IgA RF (7.0 micrograms IgA/ml, nl less than 2.0 micrograms IgA/ml). Low levels of IgM RF were found in 8/32 (25%) of patients with DH (1.1-1.6 micrograms IgM/ml, nl less than 1.0 microgram IgM/ml). These data document that IgA RF is not present in the sera of patients with DH independent of the presence or absence of IgA-CIC and that it is unlikely that the IgA-CIC present are IgA RF complexed with autologous IgG.

Molecular forms of IgA rheumatoid factor in serum and synovial fluid of patients with rheumatoid arthritis

The distribution of molecular forms of serum IgA rheumatoid factor (IgA-RF) in 42 patients with rheumatoid arthritis was examined by solid-phase radioimmunoassay following fractionation by gel chromatography or ultracentrifugation in acidic buffer. Analysis of the fractions using phosphate buffered saline indicated that the IgA-RF in each serum was mainly polymeric. However, monomeric IgA-RF was detected in sera from approximately two-thirds of the patients, after dilution of chromatographic or ultracentrifugal fractions in diluent containing mouse monoclonal anti-human alpha chain antibody. The levels of monomeric IgA-RF (mean +/- SD 38 +/- 86 micrograms/ml) and the ratios of monomeric to polymeric IgA-RF (mean +/- SD 0.29 +/- 0.41) varied over a wide range. Paired synovial fluids from 9 of the patients were also examined. Monomeric IgA-RF was detected in each, although 2 samples demonstrated only minimal quantities. Neither form of IgA-RF was detected in serum from healthy adults when analyzed under the same conditions. Thus, both monomeric and polymeric IgA-RF can occur in serum and synovial fluid from patients with rheumatoid arthritis, and their proportions vary widely among patients.

Circulating immune complexes and immunoglobulin A rheumatoid factor in patients with mesangial immunoglobulin A nephropathies

Circulating immune complexes (CIC) containing IgA and C3 were elevated in 48% of IgA nephropathy patients; IgA1 was the predominant subclass. IgA1-IgG CIC were detected in 44%, IgA2-IgG CIC in 7%, and IgM-IgA1 CIC in 16% of the patients. No IgM-IgA2 CIC were detectable. Sucrose gradient ultracentrifugation indicated that IgG-IgA1 CIC were predominantly of intermediate (13-19S) size whereas IgA1-C3 CIC sedimented from 11S to 19S. At acid pH, isolated CIC revealed the presence of substantial amounts of 7S IgA. One third of the patients had elevated serum IgA rheumatoid factor (RF) of both polymeric and monomeric forms despite normal levels of IgM-RF; 87% of patients with elevated IgA-RF had IgA1-IgG CIC. These results indicate that the IgA1 component of CIC in patients with IgA nephropathy is not necessarily of mucosal origin and suggest that a portion of these CIC consists of IgA RF immunologically complexed with autologous IgG.