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

Elevated Membrane and Soluble CD64: A Novel Marker Reflecting Altered FcγR Function and Disease in Early Rheumatoid Arthritis That Can Be Regulated by Anti-Rheumatic Treatment

OBJECTIVES

Fc receptors (FcR) interacting with immune complexes (ICs) is a central event in the immune pathogenesis of rheumatoid arthritis (RA). Here we asked if a specific FcR is linked to RA pathogenesis and if FcR activities relate to disease and treatment outcome in early RA.

MATERIAL AND METHODS

Twenty autoantibody-positive RA patients and 33 HC were included. The patients were evaluated before and after treatment with methotrexate and prednisolone. At follow-up, the EULAR response criteria were applied to determine the individual treatment outcomes. Serum immunoglobulin levels were measured and the expression of FcR for IgG (FcγR) and IgA (FcαR) on peripheral blood monocytes were determined by flow cytometry. The monocytic FcγR function was evaluated by human IgG1 and IgG3 IC-binding and TNFα stimulated release. Plasma levels of soluble FcRs (sFcRs) were determined with ELISA.

RESULTS

The IgG1 and IgG3 levels were elevated in the RA sera. The RA monocytes expressed more CD64 and cell surface-bound IgG than HC monocytes, and showed an impaired FcγR function as reflected by changes in IC-binding and decreased IC-stimulated TNFα secretion. These findings correlated significantly with different disease activity markers. Furthermore, sFcRs were elevated in the patient plasma, and sCD64 was specific for RA (compared with a reference group of patients with active psoriatic arthritis). Following treatment, immunoglobulins and sFcR levels were reduced, whereas membrane CD64 was only decreased in patients with good response to treatment.

CONCLUSIONS

Early RA patients display increased membrane and soluble CD64 and an impaired FcγR function correlating with joint disease activity. Beneficial responses of anti-rheumatic treatment in patients reduce CD64. These data suggest sCD64 as an important objective biomarker in RA.

Improvement of refractory rheumatoid arthritis after depletion of B cells

OBJECTIVE

B cells are involved in the pathogenesis of rheumatoid arthritis (RA). To evaluate the effect of therapeutic B-cell depletion for treatment of RA, an open label study has been performed using the B-cell depleting anti-CD20 antibody rituximab.

METHODS

Five patients with refractory RA were treated weekly with four infusions of rituximab (375 mg/m2) alone, or in combination with ongoing methotrexate (MTX). Patients were followed for at least 44 weeks and monitored for safety and tolerability of treatment.

RESULTS

Treatment could be performed without serious side effects and resulted in peripheral B-cell depletion lasting between 36 weeks up to > 1 year. The follow-up revealed no significant treatment-associated side effects. At 22 weeks, 4/5 patients showed a significant improvement (> 1.2) of the Disease Activity Score (DAS28). The mean DAS28 of all patients declined from 6.2 to 4.1. At 44 weeks there was one drop-out, another patient still had a sustained response, and three patients showed slowly increasing disease activity (mean DAS28 of the remaining four patients: Week 0: 6.0; Week 22: 3.85; Week 44: 5.6). Despite relatively constant immunoglobulin levels, rheumatoid factor levels decreased parallel to disease activity.

CONCLUSION

In patients with refractory RA, B-cell depletion with rituximab is safe and well tolerated. A reduction of disease activity could be observed, which eventually deteriorated after B-cell repopulation. The findings give more evidence for B-cell targeted therapies in RA.

T cells, fibroblast-like synoviocytes, and granzyme B+ cytotoxic cells are associated with joint damage in patients with recent onset rheumatoid arthritis

OBJECTIVE

To determine immunohistological markers in synovial tissue of patients with early rheumatoid arthritis (RA) which are associated with unfavourable disease outcome.

METHODS

Synovial tissue was obtained from 36 patients with RA within 1 year after the initial symptoms and before starting disease modifying antirheumatic drug treatment. Clinical, laboratory, and radiological assessments (Larsen score) were performed at the time of the biopsy and at the end of follow up (mean 58 months, range 38-72). Immunohistological analysis was performed to detect T cells, B cells, plasma cells, fibroblast-like synoviocytes (FLS), macrophages, and granzyme B+ cytotoxic cells. The sections were evaluated by digital image analysis.

RESULTS

Patients were divided into two groups based upon the radiological progression per year of follow up: group I with mild progression (n = 20; Larsen <2 points/year); group II with more severe progression (n = 16; Larsen > or =2 points/year). Regression analysis with a univariate model showed that the numbers of granzyme B+ cytotoxic cells (relative risk (RR) = 12, p = 0.003), T cells (RR = 11, p = 0.013), and FLS (RR = 10, p = 0.020) discriminated between groups I and II. A multivariate model demonstrated that the numbers of T cells (RR = 1.2, p = 0.015) and FLS (RR = 1.4, p = 0.013) were independent discriminators between groups I and II.

CONCLUSION

The numbers of granzyme B+ cytotoxic cells, T cells, and FLS in synovial tissue of patients with RA are related to the severity of joint damage. The data suggest a pathogenetic role for these cells in the process of joint damage.

The amino acid sequence of a monoclonal gamma 3-heavy chain from a patient with articular gamma-heavy chain deposition disease

Abnormal deposition of proteins, including monoclonal immunoglobulin gamma-heavy chains, may cause tissue damage and organ dysfunction. We here report the amino acid sequence of the free gamma-heavy chains present in serum and urine of the first reported case (patient G. L.) of synovial heavy chain deposition disease. The protein was heavily deleted and consisted of the hinge, in addition to the CH2 and CH3 domains, in a dimeric form, thus lacking its variable domain as well as the CH1 domain. The sequence was consistent with the gamma 3 subclass (gamma 3GL). Gm typing revealed the gamma 3 allotypes G3m(b0) and G3m(b1) in accordance with the residues Pro123, Phe128, Thr171 and Phe268 in gamma 3GL. Furthermore, the gamma 3GL molecule was glycosylated at Asn in position 129. Finally, the gamma 3GL protein was shown to contain a typical binding site for the first complement component, C1q, namely the residues Glu150, Lys152 and Lys154, with the potential of binding and activating complement, causing tissue damage following deposition.

Is there a pathogenic link between gamma heavy chain disease and chronic arthritis?

In 1991, gamma heavy chain disease was diagnosed in a 43-year-old female, who 3 years earlier had contracted an erosive seronegative chronic arthropathy. In 1996, her lymphoproliferative disorder required treatment with melphalan and prednisolone. Laboratory studies revealed a gamma3 heavy chain monoclonal component in serum and urine. Massive localization of plasma cells and blasts with cytoplasmic or cell membrane staining for gamma3 chains, but no staining for light chains, was observed by immunohistochemical studies of bone marrow as well as affected synovial tissue. Large amounts of extracellular gamma3-chains were also deposited in the synovial membrane. This is the first documentation of gamma heavy chain deposition disease directly affecting articular structures. Whether it represents the primary pathogenic event followed by reactive inflammatory changes in the joints, or another example of gamma heavy chain disease preceded by chronic arthritis, remains elusive. Regardless, several common cellular and molecular mechanisms discussed here suggest a pathogenic link between the two disease processes.

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.

Monospecific but not polyreactive human hybridoma rheumatoid factors exhibit preferential binding specificities for IgG3 and IgG4

Among 38 human hybridoma-derived monoclonal rheumatoid factors (RFs) generated from patients with either rheumatoid arthritis (RA) or systemic lupus erythematosus (SLE), two groups of RFs can be identified. Monospecific RFs were derived primarily from patients with RA and are characterized by a binding specificity for IgG3 and/or IgG4. Polyreactive RFs were derived largely from patients with SLE and show a broader pattern of reactivity to all four isotypes of IgG. Neither population of RFs was exclusive to either disease. The binding specificities identified appear to be different from the RFs isolated from patients with mixed cryoglobulinemia and may reflect a different antigen selection mechanism.

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.