The distribution and abnormal morphology of plasma cells in rheumatoid synovium

Infiltrations of plasma cells in synovium are highly associated with synovial fluid levels of APRIL in inflamed peripheral joints of rheumatoid arthritis

Infiltration of plasma cells can be a histopathological hallmark of articular synovium with rheumatoid arthritis (RA). A proliferation-inducing ligand (APRIL) may have key roles in homeostasis and development of B cells, and the differentiation of B cells into plasma cells. This study was designed to explore the relationships between the infiltrations of plasma cells in synovium and the synovial fluid levels of APRIL in inflamed peripheral joints of RA. Synovium and synovial fluid were sampled from 21 RA patients underwent arthroscopic synovectomy for inflamed peripheral joints. The variants of rheumatoid synovium were classified into the follicular and diffuse synovitis by hematoxylin and eosin staining, and the infiltrations of plasma cells in rheumatoid synovium were quantified under the light microscope. The synovial fluid levels of APRIL were measured with the enzyme-linked immunosorbent assay. The mean number of infiltrating plasma cells in synovium and the mean synovial fluid level of APRIL were significantly increased in follicular synovitis compared with those in diffuse synovitis (P = 0.009, and P = 0.018, respectively), and there was a highly positive association between the infiltrations of plasma cells and the synovial fluid levels of APRIL among all of the RA patients (Rs = 0.776, P < 0.001). These findings suggest that the local production of APRIL may be associated with the ectopic lymphoid neogenesis in rheumatoid synovium and may have a role in contributing to the infiltration of plasma cells in synovium within inflamed peripheral joints of RA.

Clonal analysis of B cells in the synovial membrane of patients with rheumatoid arthritis

OBJECTIVE

To investigate the clonal characteristics of B cells in the synovial membranes of rheumatoid arthritis (RA) patients.

METHODS

The clonality of B cells at separate sites of the synovial membrane and other tissues from RA patients were investigated by a reverse transcriptase-polymerase chain reaction with a VH framework 3 consensus primer and a subsequent single-strand conformation polymorphism analysis.

RESULTS

Several dominant bands were observed in all synovial membrane samples and some of the dominants bands were common among the 2 or 3 separate regions of each synovial sample. The persistent existence of clonal B cells was observed in metachronous synovial fluid samples.

CONCLUSION

Infiltrating B cells are oligoclonal and antigen-driven mechanisms may play a role in the generation of clonal B cells in RA synovium. The stable presence of B cell clones in synovial fluid suggests the involvement of these clones in the perpetuation of the chronic inflammation in RA.

Highly enhanced expression of the disintegrin metalloproteinase MDC15 (metargidin) in rheumatoid synovial tissue

OBJECTIVE

The aim of the study was to analyze the expression of the disintegrin metalloproteinase MDC15 (metargidin, or ADAM15) at the messenger RNA (mRNA) and protein levels in synovial tissue from osteoarthritis (OA) and rheumatoid arthritis (RA) patients compared with normal specimens.

METHODS

Conventional immunohistochemistry and confocal laser scanning microscopy of immunofluorescently stained sections, as well as in situ hybridization experiments and reverse transcription-polymerase chain reaction were performed for analyses of MDC15 expression on normal, OA, and RA synovial tissue specimens.

RESULTS

In normal synovium, MDC15 expression was detectable at a very low level. MDC15 expression was considerably increased in OA-derived tissue samples, whereas a maximum of signal intensity for MDC15 mRNA and protein was seen in the RA lining layer. The CD68+ macrophage-like synoviocytes (type A) and the CD68- fibroblast-like synoviocytes (type B) were positive for MDC15. Moreover, a very strong expression of MDC15 was also found in CD138+ plasma cells in all RA tissues as well as in OA specimens that contained areas of mononuclear cell infiltrates. CD20+ B cells and CD4+ and CD8+ T cells, however, did not exhibit expression of MDC15, either in the synovial tissue in situ or in preparations of circulating lymphocytes made from the peripheral blood of RA patients or healthy controls.

CONCLUSION

Our results demonstrate high levels of MDC15 expression in macrophage-like and fibroblast-like synoviocytes as well as in plasma cells as a histologic feature most prominent in RA synovial tissue compared with normal or OA synovial tissue. This suggests a potential role of MDC15 in the pathogenesis of cartilage destruction in inflammatory joint disease.

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.

Differential use of immunoglobulin light chain genes and B lymphocyte expansion at sites of disease in rheumatoid arthritis (RA) compared with circulating B lymphocytes

The presence of germinal centre-like structures and clonotypic expansion of lymphocytes in RA synovia may indicate a site-specific immune response to local antigens, rather than passively entrapped immune cells, that sustains synovial inflammation. In this study we compare the nature of immunoglobulin light chain variable region gene use in the synovium of RA patients with peripheral B cells to determine the nature of the synovial immune response. Using Vlambda and Vkappa gene fingerprinting, which relies on differences in CDR3 length, we demonstrate differences in the pattern of Vlambda and Vkappa use and clonotypic expansion of B cells between the synovium and peripheral blood of RA patients. Further, we show that some synovial rearrangements with long CDR3 are selectively expanded. These longer than usual CDR3 were generated by a number of mechanisms including N-additions. However, the observed differences were not uniform in different patients. These observations suggest that local synovial antigens drive significant numbers of T and B lymphocytes selected from an existing repertoire shaped by genetic and environmental factors. Further, the data argue against passive retention of most B cells in the synovium of RA patients.

Expression of matrix metalloproteinases by human plasma cells and B lymphocytes

Matrix metalloproteinases (MMP) are proteolytic enzymes that play a key role in tissue remodelling during physiological and pathological processes, by initiating the degradation of extracellular matrix. MMP overexpression can lead to tissue destruction which is characteristic of chronic inflammatory diseases such as rheumatoid arthritis and scleritis. Plasma cells are often abundant at such sites of chronic inflammation. In the present study we investigated whether plasma cells could contribute to matrix degradation by their expression of MMP In situ hybridization and immunohistochemical analyses on diseased synovial and scleral tissue demonstrated the expression of stromelysin-1 (MMP-3) and gelatinase B (MMP-9), but little or no tissue inhibitor of matrix metalloproteinase 1 (TIMP-1) mRNA, by IgG-positive plasma cells. Northern blot analysis of RNA extracted from a human plasma cell line (ARH-77), Epstein-Barr virus-transformed B cells, and purified peripheral blood B cells, demonstrated expression of stromelysin mRNA. TIMP-1 mRNA was only detected by the more sensitive reverse transcription PCR method in these cell types. Plasma cells and B lymphocytes cultured in the presence of monensin demonstrated cytoplasmic gelatinase B. Gelatin and casein zymography on conditioned media (CM) derived from cytokine treated plasma cells revealed the induction of secreted gelatinase and stromelysin activity. Western blotting confirmed the presence of stromelysin-1 and TIMP-1 proteins in plasma cell CM. These data suggest that plasma cells are not only capable of modulating an inflammatory response by antibody and cytokine production, but also by their ability to produce MMP. Secretion of MMP from focal aggregates of plasma cells may play a critical role in tissue destructive diseases such as rheumatoid synovitis and scleritis.

Analysis of the synovial cell infiltrate in early rheumatoid synovial tissue in relation to local disease activity

OBJECTIVE

To define variations in the cellular infiltrate and in the expression of monokines in synovial tissue (ST) from rheumatoid arthritis (RA) patients with different durations of disease and different levels of disease activity.

METHODS

The immunohistologic features of synovial biopsy specimens from 31 patients with early RA (< 1 year) and 35 patients with longstanding RA (> 5 years) were compared. The possible associations between these features and local disease activity, as measured by the score for pain in the biopsied knee joint were also evaluated.

RESULTS

The immunohistologic features were not dependent on disease duration. We found a positive correlation between the scores for knee pain and the semiquantitative scores for the number of macrophages, as well as the expression of interleukin-6 and tumor necrosis factor alpha, whereas the correlation with the scores for CD4+ T cells was negative. Multivariate analysis showed that these correlations were highly statistically significant (P < 0.003).

CONCLUSION

The results do not support the view that inflammatory mechanisms in the synovial tissues of RA patients differ between early and late stages of the disease. The findings presented here are consistent with the concept that early RA is the result of a synovitis process of longer duration and that macrophage-derived cytokines play an important role in maintaining the clinical signs of inflammation.

Clonal analysis of immunoglobulin mRNA in rheumatoid arthritis synovium: characterization of expanded IgG3 populations

Plasma cells secreting IgG, M, and A abound in the synovium of patients with rheumatoid arthritis, yet their immunoglobulin repertoire and clonal relationship remain to be elucidated. Locally synthesized immunoglobulins probably contribute to the chronic joint inflammatory processes which are characteristic of these patients. To determine whether B lymphocyte proliferation contributes to the synovial plasma cell infiltrate, the clonality of IgG mRNA in individual synovial biopsies from an actively inflamed joint of patients with rheumatoid arthritis was investigated by a combination of cDNA length analysis and DNA sequencing. Particular sizes of immunoglobulin cDNA, detectable in subclasses 1, 3, or 4, were expressed in most synovial biopsies from one patient, suggesting their origin from expanded clones present in each biopsy. To prove a clonal relationship between recurrent cDNA lengths, immunoglobulin cDNA was cloned from three regions of synovium in three patients. The sequence of clones with a recurrent cDNA length was determined. An IgG3 clone found in most synovial biopsies of one patient was encoded by an unmutated copy of the V(H)1 gene, DP7. In contrast, IgG3 clones encoded by mutated versions of the V(H)3 gene DP49 or the V(H)4 gene DP63 were expanded in the other two patients. Different somatic mutants of these clones were isolated from different sites in these patients. The ratio of replacement/silent somatic mutations in these two families of clones suggests that the selective clonal expansion in the synovium of patients with rheumatoid arthritis is due to an antigen-driven immune response.