Autoimmunity in Rheumatoid Arthritis

Opposing Regulation of Interleukin-8 and NF-kB Responses by Lipoxin A4 and Serum Amyloid a via the Common Lipoxin a Receptor

Lipoxin A4 (LXA4) is a potent eicosanoid that inhibits IL-1β-induced activation of human fibroblast-like synoviocytes (FLS) via the LXA4 receptor (ALXR). Serum amyloid A (SAA) is an acute phase reactant with cytokine-like properties. SAA has been shown to bind the same seven transmembrane G protein-coupled receptor ligated by LXA4. Here we compared the inflammatory responses of lipid (LXA4) and peptide (SAA) ligands in human FLS via the shared ALX and characterized their downstream signaling. LXA4 induced stimulation of tissue inhibitors of metalloproteinase-2, whereas SAA induced interleukin-8 and matrix metalloproteinase-3 production. SAA up-regulated NF-kB and AP-1 DNA binding activity, while LXA4 markedly inhibited these responses after IL-1β stimulation. A human IL-8 promoter luciferase construct was transfected into CHO cells stably expressing ALXR in order to determine the role of NF-kB and/or AP-1 in the regulation of IL-8 gene expression. The NF-kB pathway proved to be the preeminent for the biological responses elicited by both ligands. These findings suggest that two endogenous molecules, targeting a common receptor, could participate in the pathogenesis of inflammatory arthritis by differentially regulating inflammatory responses in tissues expressing the ALXR.

Analysis of differentially expressed genes between rheumatoid arthritis and osteoarthritis based on the gene co-expression network

The aim of the current study was to investigate disease-associated genes and related molecular mechanisms of osteoarthritis (OA) and rheumatoid arthritis (RA). Using GSE7669 datasets downloaded from Gene Expression Omnibus databases, the differentially expressed genes (DEGs) between RA and OA synovial fibroblasts (SFBs) (n=6 each) were screened. DEG-associated co-expression and topological properties were analyzed to determine the rank of disease-associated genes. Specifically, the fold change of differentially expressed genes, the clustering coefficient and the degree of differential gene co-expression were integrated to determine the disease-associated gene ranking. The underlying molecular mechanisms of these crucial disease-associated genes were investigated by gene ontology (GO) enrichment analysis. A total of 1313 DEGs, including 1068 upregulated genes and 245 downregulated genes were observed. The top 20 disease-associated genes were identified, including proteoglycan 4, inhibin β B, carboxypeptidase M, alcohol dehydrogenase 1C and integrin β2. The major GO biological processes of these top 20 disease-associated genes were highly involved in the immune system, such as responses to stimuli, immune responses and inflammatory responses. This large-scale gene expression study observed disease-associated genes and their associated GO function in RA and OA, which may provide opportunities for biomarker development and novel insights into the molecular mechanisms of these two diseases.

Comparison of Tc-99m MDP, Tc-99m HSA and Tc-99m HIG uptake in rheumatoid arthritis and its variants

Tc-99m polyclonal immunoglobulin-G has been shown to be a successful agent in the depiction of active inflammation in rheumatoid arthritis (RA). The objective of this study was to compare the uptake behaviors of Tc-99m HIG and Tc-99m MDP in RA and variants of rheumatoid arthritis (VRA). Seventeen patients with RA and 8 patients with VRA presenting with active inflammation were included in this study. Ten subjects with well-diagnosed degenerative joint disease constituted the control group. All joints in patients were also imaged with Tc-99m HSA to evaluate the vascularization status of the joints. Tc-99m HIG and HSA scans were obtained at 2, 4 and 24 hours after the injection of 555 MBq Tc-99m HIG and 296 MBq Tc-99m HSA. Conventional bone scans were performed 4 hours after the injection of 740 MBq Tc-99m MDP. Target-to-background (T/B) ratios were obtained exclusively over the joint regions. Tc-99m HIG T/B ratios of the active joints in RA were significantly higher than those of the non-active joints and the control group (p < 0.05). Tc-99m HIG T/B ratios in active joints showed a progressive increase between 2 and 24 hour images (p < 0.05). In contrast, Tc-99m HSA T/B ratios decreased in all active joints significantly (p < 0.05) except the ankle joint region (p > 0.05). The T/B ratios in Tc-99m MDP bone scans were higher in all active joints than in non-active RA joints and joints of controls but significantly differences were only detected in wrist and elbow joints. All clinically active joints in VRA patients accumulated Tc-99m HIG and HSA, and showed increased Tc-99m MDP uptake. These joints had a very similar Tc-99m HIG retention pattern to the RA joints. The detection rate of active joint inflammation with Tc-99m HIG was much higher than that with Tc-99m MDP. The increasing Tc-99m HIG uptake ratio between 2 and 24 hours in contrast to Tc-99m HSA indicates the presence of other binding mechanisms besides increased vascularity in RA.

Analysis of bcl-2+ lymphocyte subpopulations in inflammatory synovial infiltrates by a double-immunostaining technique

We used a double-immunostaining technique to analyze the distribution of bcl-2+ B and T lymphocytes within the synovial membranes (SM) of 13 patients with rheumatic diseases: 11 with rheumatoid arthritis (RA), 1 with ankylosing spondylitis (AS), and 1 with osteoarthritis (OA). A high proportion (up to 50%) of the lymphocytes belonged to the B cell subset. Most of both T and B lymphocytes were positive for the bcl-2 protein. In germinal centers B lymphocytes were also negative for bcl-2 protein expression, comparable to the situation in germinal centers of secondary lymphatic organs. We conclude that bcl-2- B lymphocytes are submitted to antigen selection in the inflamed SMs while bcl-2 protein expression provides survival signals for their persistence in the infiltrates. The expression of bcl-2 may be an important factor in protecting lymphocytes in SM from apoptosis by glucocorticoids, cytostatic drugs, and irradiation.

B lymphocytes and humoral immune responses in rheumatoid arthritis

Although the etiology of rheumatoid arthritis (RA) remains unknown at present, major evidence implicates humoral immune mechanisms in the pathophysiology of this disease. The primary lesions occur in the synovium and are characterized by immunological activation and chronic inflammation. Activated B cells and plasma cells secrete antibodies including rheumatoid factors and anticollagen antibodies. These antibodies give rise to immune complex formation and activation of the inflammatory cascade. There is no evidence that rheumatoid factor secreting B cells act as antigen presenting cells and present immune complex to T cells, leading to perpetuation of the inflammatory response.

Expression of a human fetal anti-DNA antibody idiotype BEG-2 beta in the families of patients with rheumatoid arthritis

BEG-2 is a monoclonal antibody produced by the human-human hybridoma technique from a 12 weeks old human fetus. A polyclonal antiserum was raised in an (NZW x Half-lop hybrid) rabbit against BEG-2 and the anti-BEG-2 anti-idiotype was purified and characterised. Using this rabbit reagent the expression of the BEG-2 beta idiotype was analysed in 12 patients with active rheumatoid arthritis and their close family members (n = 54). Twenty five sera from healthy controls were analysed to establish a normal range. Ten of 12 patients (83%) with rheumatoid arthritis expressed the BEG-2 idiotype as well as 11 of 54 healthy unaffected relatives (20%).

Low molecular weight IgM and CD5 B lymphocytes in rheumatoid arthritis

OBJECTIVES

To evaluate the role of low molecular weight (LMW) IgM and CD5 B cells in rheumatoid arthritis (RA) and to explore the possibility that LMW IgM is derived selectively from this subset of B cells.

METHODS

LMW IgM in sera and culture supernatants was detected by a sensitive immunoblot technique with an enhanced chemiluminescence detection system. CD5 B cells were determined by FACScan cytometry. In vitro studies were established in culture plates containing pokeweed mitogen with or without 2-mercaptoethanol (2-ME). Supernatants were obtained from CD5 positive hybridomas and CD5 negative hybridomas. Other immunological indices were measured by laser nephelometry.

RESULTS

Circulating LMW IgM was detected in all rheumatoid patients with significantly higher levels being observed in sero-positive patients. LMW IgM correlated significantly with total IgM and RF. Peripheral blood mononuclear cells (PBMC) from the majority of the patients with RA secreted LMW IgM in vitro as did mononuclear cells from a synovial fluid sample. The addition of low concentrations of 2-ME to the culture medium enhanced the proportions of secreted monomeric IgM. In contrast, PBMC from healthy subjects secreted only trace quantities of LMW IgM. In RA no significant correlations were observed between CD5 B cells and LMW IgM and RF. LMW IgM could be detected in the supernatants from both CD5+ and CD5- B cell lines. Finally, CD5 B cells were not significantly elevated in RA and levels remained constant over time.

CONCLUSION

LMW IgM exists in high concentrations in RA sera and synovial fluid. Serum level correlates with RF and IgM. In vitro studies have suggested that the occurrence of LMW IgM may be due to an intrinsic defect(s) in the assembly of the IgM pentameric molecule. LMW IgM is unlikely to be derived solely from CD5 B cells.

Effects of exercise and polysulfated glycosaminoglycan on repair of articular cartilage defects in the equine carpus

Our aim was to determine if mild to moderate postoperative exercise and intra-articular polysulfated glycosaminoglycan result in improved repair of large, experimentally induced osteochondral defects in a weight-bearing surface of equine joints. Arthroscopic debridement was used to produce full-thickness defects in a weight-bearing area of the radial carpal bones in 18 ponies. The ponies were randomly assigned to two groups balanced for age: nine animals in the exercise and nine in the no exercise group. Six ponies in each group were medicated weekly for 5 weeks with an intra-articular injection of polysulfated glycosaminoglycan in one middle carpal joint beginning at the time of operation. Walking (twice daily) was begun 6 days postoperatively, and by the twelfth week postoperatively the ponies were trotting for 25 min and walking for 15 min twice daily. At the time of the ponies' death, 17 weeks postoperatively, each defect had an average of 50-75% coverage with repair tissue. Exercised, medicated joints had a significantly smaller area of coverage with repair tissue than exercised, nonmedicated joints. Cartilaginous repair tissue from exercised ponies contained significantly more glycosaminoglycan and type-II collagen (r = 0.53, p < 0.05). The ratio of hydroxylysine to hydroxyproline was significantly lower and the ratio of collagen content to total protein was significantly higher in the repair tissue of medicated joints than in the repair tissue of nonmedicated joints; this is consistent with the presence of less type-II collagen in the repair tissue in medicated joints. We concluded that postoperative exercise was beneficial and that the immediate postoperative use of intra-articular polysulfated glycosaminoglycan was detrimental to the development of cartilaginous repair tissue in large osteochondral defects of equine joints.

Human CD5-positive B cells in lymphoid malignancy and connective tissue diseases

The current literature on human CD5-positive B cells (CD5 + B cells) has been analysed, with a special emphasis on non organ-specific auto-immune diseases. Malignant cells of most of the chronic lymphoid leukaemias of the B cell lineage express the CD5 molecule. Antibodies of the IgM class produced by leukaemic B cells are multispecific auto-antibodies. The CD5 + B cell subset may be expanded in non organ-specific autoimmune diseases, such as rheumatoid arthritis, primary Sjögren's syndrome, systemic lupus erythematosus. This holds true for various conditions, including organ-specific auto-immune diseases. Since auto-immune features are common in lymphoproliferative disorders, and the latter be a complication in non organ-specific auto-immune diseases, CD5 + B cells may represent an intermediary between these auto-immune diseases and B cell lymphoproliferations. Studies on the regulation of CD5 + B cell production and function are likely to shed light on the aetiology of, and pathogenetic mechanisms operating in the different disease states.

CD5+ B lymphocytes and CD4+ CD45RA+ T cells in Graves' disease

Fifteen patients affected by new-onset Graves' disease with ophthalmopathy have been examined for lymphocyte subset phenotypes by two-colour cytometric analysis. CD5+ B cells were significantly increased in comparison to the normal population (43.2 +/- 20.6% versus 19.5 +/- 6.9%; p < 0.0009); total T cells showed a normal amount (70.4 +/- 9.6%), but the levels of THLADR+ cells were significantly increased in comparison to the control group (13.7 +/- 10.5% versus 4.7 +/- 3.2%; p < 0.007). The characterization of the subset suppressor-inducer CD4+ CD45RA+, evaluated as percentage of the total CD4+ T cells, showed a significant decrease in comparison with the control group (43.8 +/- 13.5% versus 52.3 +/- 6.5%; p < 0.03). Serum immunoglobulin evaluation showed a statistically significant increase of IgM (p < 0.05) and a significant decrease of IgA (p < 0.02). A statistical correlation between IgM levels and percentage of CD5+ B cells has been found (p < 0.04). The defect of suppressor-inducer T cell subset, along with the increase of CD5+ B cells may contribute to the pathogenetic mechanism of the disease in patients with a genetically-induced aberrant immune response.

Characteristics of immunocompetent cells in synovial membranes from multiple sites in patients with rheumatoid arthritis

The phenotypic characterization of enzymatically dissociated mononuclear cells in synovial membrane samples from multiple sites in two patients with rheumatoid arthritis (RA) were examined by fluorescence activated flow cytometry. In synovial membrane samples from each patient there was a consistent increase in the proportion of CD8+ cells (suppressor/cytotoxic), CD14+ cells (monocytes/macrophages), and HLA-DR+ cells compared with paired peripheral blood mononuclear cells. The proportion of CD4+ cells (helper/inducer) in synovial membrane was variable. Studies of in vitro production of IgM and IgM rheumatoid factor in one patient showed strikingly similar values for synovial membrane rheumatoid factor production at the two sites, which was enhanced compared with production in peripheral blood. These results suggest that in individual patients with RA the intra-articular immune response is comparable at multiple anatomical sites and that it is distinct from that in peripheral blood.

Cells in the marginal zone of the spleen

The marginal zone of the spleen forms an intriguing area in which a variety of cell types are combined. Several of these cell types seem to have a fixed position in the marginal zone, such as the marginal zone macrophages, the marginal metallophilic macrophages at the inner border, and, to a lesser extent, the marginal zone B cells. For other cell types--T lymphocytes, small B cells, and dendritic cells--the marginal zone is only a temporary residence. It is this combination of relatively sessile cell populations and the continuous influx and passing of bloodborne immunocompetent cells that turn the marginal zone into a dynamic area, particularly apt for antigen processing and recognition. In no other lymphoid organ can such a unique combination of cells and functions be found. The opening of the arterial blood stream in the marginal sinuses results in a reduction of the velocity of the blood stream, and antigens are initially screened in the marginal zone. To this, extremely potent phagocytic cells, the marginal zone macrophages, are present which can take up and phagocytize large foreign particles, such as bacteria and effete red blood cells. Further filtration of the blood takes place in the filtration beds of the red pulp. The marginal zone macrophages express membrane receptors for bacterial polysaccharides which lead to efficient phagocytosis, probably even in the absence of prior opsonization. Antigenic fragments produced this way can be taken up by dendritic cells that enter the spleen by the blood as part of a mobile surveillance immune system. Dendritic cells present antigen to T cells in the outer area of the T cell-dependent PALS, leading to clustering and enrichment of antigen-specific T cells. Antigens in the marginal zone can also directly associate with memory B cells thought to reside here for longer times, having intimate contact with the marginal zone macrophages. B memory cells then migrate into the PALS and present antigen to T cells. The marginal zone therefore functions not only as an area of initial filtration and phagocytosis of antigens from the blood, but also as a site of lymphocyte emigration. Some of the incoming T and B lymphocytes in the recirculating pool enter the white pulp from the marginal zone. The underlying force and selective molecular mechanisms that guide this migration are unknown. Both B and T lymphocytes recirculate through the outer PALS area on their way to the follicles and the inner PALS, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Immunohistochemical analysis of synovial membranes from inflammatory and non-inflammatory arthritides: scarcity of CD5 positive B cells and IL2 receptor bearing T cells

Rheumatoid Arthritis (RA) synovial membranes were examined by single and dual immunohistological techniques with a number of monoclonal antibodies against lymphocyte and macrophage related antigens. CD4 positive T lymphocytes frequently expressed MHC Class II antigens and were found in sublining collections in close association with activated macrophages as well as B lymphocytes. CD8 positive T cells surrounded these collections as well as being scattered throughout the membrane and also frequently expressed MHC Class II antigens. IL2 receptor (IL2r) expression on T cells and CD5 expression on B cells were rarely seen in these synovial membranes. Similar immunohistological architecture was found in synovial membranes from patients with psoriatic arthritis (PA) and Reiter's Syndrome (RS). Normal synovium contained few T cells, with few cells expressing MHC Class II antigens. Synovium from osteoarthritis (OA) patients also demonstrated similar immunohistological changes to those found in inflammatory arthritides, suggesting that there are only quantitative rather than qualitative differences between the synovial membrane immunohistological architecture from patients with inflammatory and noninflammatory arthritides.

Levels of CD5+ B cells are not increased in probands or relatives in a family study of primary Sjögren's syndrome

Levels of CD5+ B lymphocytes were assayed in a large family study of Primary Sjögren's syndrome. There was no significant difference in CD5 expression by index cases or their relatives when compared to controls. No association between CD5 expression, serological abnormalities or HLA haplotype was found and, furthermore, no evidence of linkage with HLA was observed. There was, however, variation in the expression of CD5+ B cells between the families. Levels in spouses were lower and reached statistical significance. The role for genetic and environmental factors influencing CD5 expression is discussed. Any genetic influence does not appear to involve the HLA region or genes in linkage disequilibrium.

B cells expressing CD5 antigen are markedly increased in peripheral blood and spleen lymphocytes from patients with immune thrombocytopenic purpura

By two-colour flow cytometric analysis, we examined the proportion of B lymphocytes bearing CD5 cell surface antigen (CD 5+ B cells), which are capable of producing autoantibodies, both in peripheral blood and spleen from patients with chronic immune thrombocytopenic purpura (ITP). The percentage of CD5+ B cells in peripheral blood lymphocytes (PBLs) was significantly increased (P less than 0.005) in patients with ITP (3.7 +/- 2.2%, n = 30) as compared with normal controls (1.7 +/- 0.7%, n = 28). However, there was no correlation between the percentages of circulating CD5+ B cells and platelet counts. The percentage of splenic CD5+ B cells in ITP patients was much more increased (9.0 +/- 4.5%, n = 9), P less than 0.005) compared with that of other disorders (3.2 +/- 0.5%, n = 5). Furthermore, isolated splenic CD5+ B cells from two out of five ITP patients produced high levels of IgM-type, platelet-bindable antibodies (PBIgM) after stimulation with Staphylococcus aureus Cowan I (SAC), while CD5- B cells isolated from the same spleen or splenic CD5+ B cells from other non-autoimmune disorders failed to produce significant amount of PBIgM. In three ITP patients, no increase in PBIgM was detected despite SAC stimulation. The increased proportion of CD5+ B cells in peripheral blood and spleen, and their ability to produce anti-platelet antibodies indicate that they are directly involved in the autoimmune pathogenesis in ITP.

Pre-B lymphocytes with intracytoplasmic mu chains in the peripheral blood of rheumatoid arthritis patients

A dysregulation of B-cell differentiation and activation has long been evidenced in rheumatoid arthritis (RA). Such analyses have, however, usually focused on the latest stages of B-cell development. Using a classical technique of immunofluorescence labeling on cytospins, we investigated the presence of peripheral pre-B lymphocytes in 92 RA patients and 23 controls. Cells with intracytoplasmic mu chains were evidenced in 58.7% of the RA patients studied, ranging between 0 and 30%, while small numbers of c-mu cells, never exceeding 6% of peripheral blood lymphocytes, were observed in 9 controls. Relationships between this feature and clinical or laboratory data were investigated, showing a negative correlation between the percentage of c-mu + lymphocytes and Ritchie's index (P = 0.05), the number of tender or swollen joints (P = 0.05), erythrocyte sedimentation rate (P = 0.005), seropositivity (P = 0.05), and disease duration (P = 0.01).

Lack of natural antibodies in rheumatic diseases

The prevalence and Ig class of natural antibodies in the sera of healthy individuals and of patients with rheumatic diseases were studied. The presence, even in high concentrations, of natural antibodies in normals was confirmed. In the rheumatic diseases tested, however, a discordance in the levels and Ig class of anti-actin, anti-myosin and anti-ssDNA antibodies was noted. IgM anti-actin antibodies occur infrequently, whereas IgM anti-myosin and anti-ssDNA are increased in these diseases. IgG anti-actin antibodies are increased in the sera of patients with RA, but not in patients with SLE, polymyositis or mixed connective tissue disease (MCTD). IgG anti-myosin as well as anti-ssDNA antibodies were increased in patients with RA and SLE, but not in patients with polymyositis or MCTD. These findings suggest that these natural antibodies are unlike the multispecific autoantibodies produced by lymphocytes from the CD5+ B cell lineage and that they may have undergone affinity maturation. Perhaps natural antibodies are a feature of health rather than of disease.

The relationship between CD5-expressing B lymphocytes and serologic abnormalities in rheumatoid arthritis patients and their relatives

The influence of genetic factors on the expression of CD5+ B lymphocytes and their relationship to a broad spectrum of autoantibodies was investigated in a study of 12 patients with rheumatoid arthritis (RA) and 52 of their healthy first-degree relatives. The proportion of CD5+ B cells was significantly higher in RA patients (mean +/- SEM 23.9 +/- 2.7%) compared with that in their relatives (18.3 +/- 1.1%, P less than 0.05) and compared with that in a group of healthy control subjects (16.1 +/- 1.8%; P less than 0.05). Much more striking, however, were the high levels of CD5+ B cells found in the patients and their relatives in 5 of the families studied. Increases in total immunoglobulin levels and autoantibody levels were frequently observed in RA patients (approximately 20-40%) and their relatives (approximately 10-20%). Furthermore, a statistically significant correlation (P less than 0.01) between IgM rheumatoid factor and the percentage of B lymphocytes expressing CD5 was observed.

'Fetal-type' B and T lymphocytes in rheumatoid arthritis and primary Sjögren's syndrome

B lymphocytes expressing CD5 (CD5+B cells) and T lymphocytes using the gamma and delta chains to form their antigen receptor (gamma delta +T cells) are major populations in developing fetuses, but become relatively minor in normal adults. However, both subsets are expanded in the peripheral blood of more than 50% of patients with rheumatoid arthritis and primary Sjögren's syndrome. We have examined the surface phenotype of these subsets using flow cytometry and have studied the frequency of IgM-producing lines after EBV-transformation of sorted CD5+B and CD5-B cells isolated from neonatal umbilical vein and RA peripheral blood. The intensity of CD5 expression on B cells was at least 10 times 'duller' than on T cells, CD5 'dull' cells were CD3 negative, and T cells bearing the gamma delta antigen receptor did not express either CD4 or CD8 on their surface. In vitro stimulation by Staphylococcus aureus Cowan I or transformation by Epstein-Barr virus of CD5+B cells resulted in loss of CD5 antigen from the surface of B cells. EBV-transformation of sorted CD5+B and CD5-B lymphocytes from neonatal blood gave rise to IgM-secretion in 100% of the Ig-secreting lines. CD5+B fraction isolated from RA blood also generated 100% IgM-secreting lines, whereas 29% of the Ig-secreting lines obtained from RA CD5-B fraction did not secrete IgM. The function of these 'fetal-type' T and B lymphocytes is unknown, however their expansion in rheumatoid arthritis and primary Sjögren's Syndrome suggests that they may play a role in autoimmune diseases.

The significance of CD5+ B cells in rheumatic diseases

The presence of autoantibodies in rheumatoid arthritis (RA) and primary Sjögren' syndrome (SS) is a feature of these diseases. Because of the probable role of autoantibodies in the pathogenesis of RA and primary SS, the study of the origin and regulation of B lymphocytes producing autoantibodies is of special importance. In mice, B lymphocytes can be divided into two populations of distinct lineages, the conventional bone marrow-derived B subset and the self-renewing peripheral subset. B lymphocytes of the latter express an antigen initially described as T cell specific, the Ly-1 or CD5 antigen. In human, such CD5+B cells are found in foetal lymphoid tissue but their frequency diminishes in adult life. We have found a significant increase in CD5+B cells in the peripheral blood of patients with RA and primary SS, and a small family study of relatives of two RA patients suggests that such 'high phenotype' could be a genetic trait. Furthermore, CD5+B cells appear enriched in autoantibody-producing cells since they produce IgM-rheumatoid and other autoantibodies when suitably activated in vitro. Our current hypothesis is that persistence of high numbers of CD5+B cells in adulthood may predispose to chronic inflammatory arthritis due to the reactivity of the antigen receptor of these cells with a variety of autoantigens in the joint. Such reactivity would allow an autoimmune reactions causing the perpetuation of chronic inflammation at the disease site.