B cell differentiation factor in synovial fluid of patients with rheumatoid arthritis

Castleman's Disease and Interleukin 6

Castleman's disease is a rare condition characterized by benign hyperplastic lymph nodes. Based on the morphological features, it has been divided into hyaline-vascular, plasma cell and intermediate types. The latter two types are frequently associated with a wide variety of clinical pictures such as fever, anemia with hypotransferrinemia, hyperimmunoglobulinemia and an increase in the concentration of C-reactive protein (CRP). Although immunological disturbances have been suggested to play important roles in the pathophysiology of Castleman's disease, the precise mechanisms for the generation of its clinical pictures are still unsettled. In this respect, we have reported a pediatric case with spontaneous production of high levels of B cell differentiation factor (BCDF) activity by the hyperplastic lymph node, and we demonstrated here the strong expression of interleukin 6 (IL-6) gene in the lymph node cells. On the other hand, recent studies have revealed that IL-6 is a multifunctional cytokine; IL-6 not only induces the immunoglobulin production but also induces the acute phase reaction, and functions as an endogeneous pyrogen. In the acute phase reaction, IL-6 may induce an increase in CRP concentration and hypotransferrinemia. These studies indicate that the overproduction of IL-6 by the hyperplastic lymph node may be closely related to the pathophysiology of Castleman's disease. Therefore, it is considered that this disease is a "disorder of IL-6 production".

Correlation between clinical/radiographic features and inflammatory cytokine networks produced by macrophages stimulated with endodontic content

INTRODUCTION

Macrophages are highly activated by endodontic contents. This study investigated the correlation between different clinical signs/symptoms and radiographic features according to the levels of interleukin (IL)-1β, tumor necrosis factor α (TNF-α), IL-6, IL-10, prostaglandin E(2) (PGE(2)), and their networks produced by endodontic content-stimulated macrophages collected from primary endodontic infection with apical periodontitis (PEIAP).

METHODS

Samples were taken from 21 root canals with PEIAP by using paper points. The presence of exudate (EX), pain on palpation (POP), tenderness to percussion (TTP), and the size of the radiographic lesion (SRL) were recorded. Polymerase chain reaction (16S rDNA) was used for bacterial detection and limulus amebocyte lysate (LAL) assay for endotoxin measurement. Raw 264.7 macrophages were stimulated with bacterial contents during 24 hs. The amounts of IL-1β, TNF-α, IL-6, IL-10 and PGE(2) were measured by enzyme-linked immunosorbent assay. Log-based data were correlated by multiple logistic regression (P < .05).

RESULTS

Bacteria and endotoxin were detected in 100% of the samples. IL-6 and TNF-α were positively correlated with SRL and EX, respectively (P < .05). Clinical signs/symptoms and radiographic findings were set as dependent variables for EX-positive correlations between PGE(2), IL-1β, and TNF-α (P < .05), whereas IL-6 and PGE(2) were positively correlated to each other in POP but negatively correlated in SRL (P < .05). When POP and TTP-POP were set as dependent variables, different cytokine networks were found.

CONCLUSIONS

Our findings suggest different roles for each cytokine in the development of apical periodontitis, whose effects of overlapping networks depend on the signs/symptoms and radiographic features found in endodontic infection.

IL-6 is the principal factor produced by synovia of patients with rheumatoid arthritis that induces B-lymphocytes to secrete immunoglobulins

First, IL-6 is produced by synovial tissue of patients with rheumatoid arthritis (RA) and is the principal mediator produced by that tissue inducing differentiation of B-lymphocytes into antibody-forming cells. The Leu-1+ subset of B-lymphocytes is induced by IL-6 to secrete rheumatoid factor (IgM with anti-Fc gamma specificity). Second, the main cell types producing IL-6 in cells dissociated from RA synovial tissue are mononuclear leukocytes. Connective tissue type cells (synoviocytes) cultured from RA synovial tissue produce IL-6 in response to IL-1 beta, and IL-6 formation is increased by TGF-beta. Glucocorticoids strongly inhibit and PGE2 slightly inhibits IL-1-induced IL-6 mRNA expression in synoviocytes. Production of IL-6 increases when undissociated RA synovial tissue is maintained in culture, thus suggesting release from inhibition by a factor or factors not yet identified. Third, the major known local effect of IL-6 in RA synovial tissue is the augmentation of antibody formation and the major known systemic effect is the induction of the synthesis by the liver of acute-phase proteins, especially C-reactive protein. Levels of circulating C-reactive protein are reported to decrease in RA patients receiving long-acting antirheumatic drugs, which would be consistent with the interpretation that immature monocyte-derived macrophages are major producers of IL-6 in these patients.

Modulating co-stimulation: a rational strategy in the treatment of rheumatoid arthritis?

Rheumatoid arthritis (RA) is a common destructive inflammatory disease that affects 0.5-1% of the population in many countries. Even though several new treatments have been introduced for patients with RA, a considerable proportion of patients do not benefit from these, and the need for alternative treatment strategies is clear. This review explores the potential for a therapy targeting the adaptive immune system by modulating co-stimulation of T cells with a CTLA4-Ig fusion protein (abatacept).

Elevated angiogenin levels in synovial fluid from patients with inflammatory arthritis and secretion of angiogenin by cultured synovial fibroblasts

Angiogenesis is a key process in the pathogenesis of inflammatory arthritis. Angiogenin is one of the most potent inducers of neovascularization in experimental models in vivo. To look for evidence that angiogenin is involved in inflammatory joint disease, we examined plasma and synovial fluid (SF) samples from rheumatology patients and synovial fibroblast cell culture supernatants. Angiogenin levels were determined by radioimmunoassay and ELISA. Plasma angiogenin concentrations ranged from 96 to 478 ng/ml, with no significant difference between patients and normal controls. In SF, angiogenin concentrations were significantly higher in patients with acute or chronic synovitis (rheumatoid arthritis (RA): median, 104 ng/ml; range 13-748, n = 14; crystal-induced arthritis (CIA): median, 149 ng/ml; range, 37-616, n = 14, and other chronic inflammatory arthritis: median, 42 ng/ml; range, 15-205; n = 9) than in the 18 patients with osteoarthritis (OA) (median, 20 ng/ml; range 8-116) (P < 0.0001, anova). Angiogenin levels in SF from RA patients in remission with secondary OA were similar to those achieved in primary OA, and decreased in parallel with the resolution of acute gout. Angiogenin protein was released by cultured synovial fibroblasts from OA and RA patients, and reached 1.18 ng/106 cells/day. These data suggest that angiogenin may mediate local inflammation in arthritis via effects on angiogenesis and leucocyte regulation.

Mediators of acute and chronic periradicular lesions

Multiple mechanisms are involved in the pathologic changes associated with formation of acute and chronic periradicular lesions. Mechanical injury to the periradicular tissues can cause activation of several pathways of inflammation and release of nonspecific mediators. Continuous irritation of periradicular tissues can cause activation of several pathways of inflammation and release of nonspecific mediators. Continuous egress of antigens from a pathologically involved root canal can also result in one or a combination of the various types of immunologic reactions. A number of these reactions participate in the destruction of periradicular tissues. Because of complex interactions between the various components of these systems, the dominance of any one pathway or substance may be difficult to establish.

Effects of glucocorticoids in rheumatoid arthritis. Diminished glucocorticoid receptors do not result in glucocorticoid resistance

OBJECTIVE

Lymphocytes of patients with rheumatoid arthritis (RA) have diminished receptor density; thus, patients with RA should show partial resistance to glucocorticoids. We investigated the glucocorticoid sensitivity of lymphocytes in RA patients compared with healthy subjects.

METHODS

We determined the effects of glucocorticoids on lymphocyte proliferation and cytokine release.

RESULTS

Proliferation and cytokine release were inhibited in RA patients to the same extent as in healthy controls.

CONCLUSION

Diminished receptor density in RA patients does not result in glucocorticoid resistance.

Protein-G binding material from synovial fluid of rheumatoid arthritis patients induces unorthodox autoantibodies (IgG1 rheumatoid factor) in NZB, NZW and (NZB x NZW)F1 mice

Our previous studies have demonstrated that injection of rheumatoid arthritis (RA) synovial fluid (SF) induces a marked increase mainly of IgG1 antibody-producing cells in autoimmune disease prone (NZB x NZW)F1 mice but not in CBA mice. In the present study, the in vivo effect of RA-SF on autoantibody production was tested in different strains of mice. Injection of RA-SF induced the production of unorthodox autoantibodies (IgG1 rheumatoid factor, RF) in young (NZB x NZW)F1 mice as well as in their parental strains NZB and NZW, but not in normal mice (CBA) or in mice with severe combined immunodeficiency, indicating that the response is not caused by a conventional immune response against RA-SF material. IgG1 RF production was rapidly induced and reached high levels already on day 7 and lasted for more than 90 days. The induction of IgG1 RF was not the result of polyclonal activation, since RA-SF did not stimulate the production of other antibodies, such as autoantibodies against double-stranded DNA, bromelain-treated mouse red blood cells, myosin, transferrin, cytochrome c, thyroglobulin or myoglobin or antibodies reactive with the hapten TNP. To elucidate the identity of the active substance in RA-SF, responsible for IgG1 RF production, bound and unbound material of RA-SF, eluted from a protein-G column was injected into (NZB x NZW)F1 mice. Only the protein-G binding material was active, indicating that the effect is mediated by autoantibodies or immune complexes in the synovial fluid. Further studies demonstrated that identical concentrations of protein obtained from a pool of normal human IgG or SF from seronegative RA and non-RA arthritides patients did not contain the same activity.

Selective presence of IgG2b inducing factor in synovial fluid of patients with rheumatoid arthritis

The factor, that we have defined and called IgG2b inducing factor, in synovial fluid of rheumatoid arthritis patients (RA-SF) has previously been well characterized both in vitro and in vivo revealing that RA-SF induces a significantly higher IgG2b antibody production in LPS activated murine spleen cells. This activity was separated from the hitherto identified cytokines or factors in RA-SF. In this study we have compared the IgG2b inducing activity in RA-SF with synovial fluid from patients with non-RA arthritides. Here we show that the IgG2b inducing activity is significantly enriched in patients with RA compared to patients with non-RA arthritides and it is not found in healthy, post-traumatic, control groups. We do not yet know the implications of this finding for the disease progress of rheumatoid arthritis, but we believe that the identification of this B cell differentiation factor might elucidate the mechanism leading to hyperactivation of B cells in rheumatoid arthritis.

Partial biochemical characterization and purification of IgG2b inducing factor as a new cytokine from synovial fluid of patients with rheumatoid arthritis

Rheumatoid arthritis synovial fluid (RA-SF) contains a novel biological activity, which selectively induces IgG2b antibody production in lipopolysaccharide (LPS)-activated mouse spleen cells in vitro and in vivo. Our previous studies have shown that this activity is not functionally identical to other well-known cytokines and interleukins. In this study we demonstrate the partial purification and biochemical characterization of the IgG2b inducing activity in RA-SF. Biochemical characterization revealed that the IgG2b inducing activity in RA-SF has the following properties: it is a protein, sensitive to pH > 11 and < 4, which is precipitated by 50% of saturated ammonium sulphate and has a molecular weight of 50-70 kDa; it binds to Cibacron-blue and heparin and its activity is not mediated by immunoglobulins or immune complexes, which are present in RA-SF. Biochemical characteristics of the IgG2b inducing activity also differ from other cytokines and interleukins. The term IgG2b inducing factor is proposed for this novel activity.

Synovial fluid cells in juvenile arthritis: evidence of selective T cell migration to inflamed tissue

The perpetuation of chronic synovitis in juvenile arthritis (JA) is a complex interaction of local and systemic regulatory mechanism. We examined the cell surface phenotype of synovial fluid cells and peripheral blood lymphocytes from 15 patients with JA to better understand the mechanism of local inflammation. Synovial fluid and peripheral blood mononuclear cells were analysed for cell surface expression of CD2, CD3, CD4, CD8, CD19, CD25, CD29, CD45R and Ia using flow cytometry. We found a very low percentage of B cells with a concomitant increase of T cells in synovial fluid as compared with peripheral blood. A large percentage of the synovial fluid T cells were HLA-DR+, or activated T cells, and there was a relative decrease in CD4+ cells in synovial fluid as compared with peripheral blood. There was only a minimal increase in CD25+ synovial fluid cells. The synovial fluid CD4+ cells were mainly of the CD2high, CD29+, CD45RO phenotype. This CD4 phenotype found on synovial fluid cells from patients with JA and in particular the CD29 cell surface marker, which recognizes a common beta-chain of adhesion molecules, is associated with binding to extracellular matrix proteins and is also associated with 'primed' T cells. Our results demonstrated the presence of T cells which either selectively migrate to synovium and synovial fluid or are activated in situ in the joint.

Rheumatoid arthritis synovial fluid enhances T cell effector functions

Rheumatoid arthritis is a chronic autoimmune joint disease of unknown etiology. T cells are believed to be important in the pathogenesis of rheumatoid arthritis since they infiltrate the joints and express several activation markers, such as MHC class II and IL-2R. In this study we have elucidated the effect on freshly isolated T cells of rheumatoid arthritis synovial fluid (RA-SF), which contains in vivo produced cytokines and enzymes. The mouse mixed lymphocyte culture (MLC) has been used as a model and specific cytotoxicity was evaluated against 51Cr-labelled sensitive target cells. Studies have shown that RA-SF contains a B cell differentiation activity that can cross-react between the human and murine species. Here we have shown that the addition of RA-SF strongly potentiates cytotoxic activity as well as lymphokine production by allogeneic activated effector T cells. The enhanced cytotoxicity induced by RA-SF was found to be due to a combined effect of increased cytotoxic T lymphocyte (CTL) precursor frequency, measured by limiting dilution analysis, and a more efficient killing on a per cell basis. Kinetic studies show that RA-SF must be added within 48 h after initiation of the MLC, otherwise the effect is lost. The target cell specificity of RA-SF was studied, using enriched CD4+ or CD8+ responder cells in the MLC. It was found that RA-SF could act directly on the CD8+ cells and potentiate their development to cytotoxic effector cells: this activity was not found when CD4+ responder cells were used instead. RA-SF could, on the other hand, greatly enhance IL-2 production by CD4+ responder cells. We suggest that B and T cell activity in RA-SF is important in the propagation of chronic inflammation in the joints of patients with rheumatoid arthritis.

[Current aspects of paraneoplastic acute polyarthritis]

Paraneoplastic acute polyarthritis (PAP) is a recognized rheumatological entity with semeiological features that are based only on a few published cases. We thought that it would be of interest to review the literature and present the current characteristics of PAP, taking into account only those cases where the acute polyarthritis and a neoplastic disease followed parallel courses. The clinical manifestations of PAP are extremely varied, making it difficult to distinguish this disease from some forms of rheumatoid arthritis, the RS3 PE syndrome or polymyalgia rheumatica. Clinicians must be vigilant when they are faced with a particularly progressive acute polyarthritis in a patient aged over 60, and particularly when this patient's general condition is altered and when fever and a clear-cut inflammatory syndrome are present. In such circumstances, it is mandatory to investigate for an underlying neoplasia.

Specific and non-specific autoreactive immunity

Most autoimmune diseases are HLA-associated which supports the notion that they are dependent upon specific immune activation of a limited set of T cell clones. Findings which imply that induction of autoimmune reactivity probably does not differ from normal immune responses are discussed. The possibility of transferring autoimmune disease using T cell clones indicates that target structures for auto-immune attack are also present in healthy individuals. In the present article, it is argued that autoimmune reactions and immunity against nominal conventional antigens in principle are effected and regulated by similar mechanisms. It is assumed that persistent tissue damage occurs if immune attack is directed against tissues that cannot be regenerated, such as in diabetes, or are only slowly reconstituted, such as in rheumatoid arthritis. Normal immune responses are regulated by various inflammatory mediators and cytokines/interleukins. The joint of patients with rheumatoid arthritis is discussed as a model for propagation of immune reactions and tissue destruction in autoimmune disease. Of the different cytokines which are present in the synovial fluid or produced by cells in the synovial tissue, most are presumed to have originated in macrophages/monocytes such as IL-1, IL-6, IL-8, TNF-alpha and TGF-beta. Even so, T cells are believed to have an important role for the continued reactivity associated with autoimmune disease. This discrepancy can be explained in different ways. T cell products might escape detection because they are short-lived, they are immediately consumed or they are produced only during short time intervals.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between IgG2b-inducing activity in rheumatoid arthritis synovial fluid and other well-known cytokines and inflammatory mediators

In the present study, we sought to identify the T cell-replacing factor which selectively induces IgG2b antibody formation in lipopolysaccharide-activated mouse spleen cells in vitro and in vivo, and which is present in the synovial fluid (SF) of rheumatoid arthritis (RA) patients. The protein A plaque assay was used to measure IgM, IgG1, IgG2b, and IgG3 plaque-forming cells. An enzyme-linked immunosorbent assay was used to measure interleukin-6 (IL-6) levels in RA SF. We found that IgG2b induction by RA SF is not caused by IL-6, IL-1, or any other inflammatory cytokines or mediators, such as transforming growth factor beta, platelet-derived growth factor, nerve growth factor, fibroblast growth factor, epidermal growth factor, elastase, collagenase, and phospholipase A2. IgG2b-inducing factor in RA SF has unique biological properties compared with those of the interleukins and inflammatory mediators known to be present in RA SF.

Identification of the major fibroblast growth factors released spontaneously in inflammatory arthritis as platelet derived growth factor and tumour necrosis factor-alpha

Rheumatoid arthritis is characterized by chronic inflammation and proliferation of a number of important elements within the joint including the synovial fibroblasts. Elevated levels of a number of cytokines such as Il-1, IL-2, IL-6, interferon-gamma (IFN-gamma), transforming growth factor-beta and tumour necrosis factor-alpha (TNF-alpha) have been detected in the synovial fluid of patients with rheumatoid arthritis and other inflammatory arthritides. It seems likely that local release of such mediators may be responsible for the proliferation and overgrowth of connective tissue elements in these disorders. In order to ascertain whether there was evidence to suggest local production or release of fibroblast growth factors in the joint in inflammatory arthritis, and to determine their identity, cells were obtained from the synovial fluid of 15 patients with chronic inflammatory arthritides. All subjects' synovial fluid cells spontaneously released growth factor activity for fibroblasts. This was present in large amounts, being detectable in culture supernatants diluted to a titre of at least 1/625. By a series of depletion experiments using solid-phase bound antibodies to cytokines, it was possible to demonstrate that this activity was due to TNF-alpha and platelet-derived growth factor (PDGF). Thus, this study showed for the first time that functionally active PDGF was released from synovial fluid cells. Both PDGF and TNF-alpha appeared to contribute in approximately equal amounts to this fibroblast growth factor activity, and were synergistic in effect. Thus this study provides evidence for the local production and release of these two cytokines and suggests that together they are the dominant factors in fibroblast proliferation within the synovial cavity.

Cytokines in rheumatoid arthritis

Joints with rheumatoid arthritis are a site for chronic inflammation involving T cells, B cells, macrophages and dendritic cells. When these cells interact cytokines are likely to be produced. The presence of different cytokines in the synovial fluid of patients with rheumatoid arthritis has been studied and the macrophage derived cytokines such as IL-1, IL-6, TNF-alpha, TGF-beta and PDGF have usually been detected in large quantities, whereas T cell produced cytokines (IL-2, IL-4, IFN-gamma) are absent or present in small quantities. IL-1, IL-6 and TNF-alpha have several functions which suggest that they participate in the chronic disease process of rheumatoid arthritis, such as increasing production of eicosanoid, collagenase and prostaglandin E2. Many synovial B cells are activated and produce large amounts of immunoglobulins. We searched for a B cell stimulatory activity in rheumatoid synovial fluid and found a B cell differentiation and helper activity. Cytokines in the joints of patients with rheumatoid arthritis seem central for the propagation of the disease process. Specific intervention in cytokine production or in its effects might help to relieve symptoms in rheumatoid patients.

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.

Interleukins and tumor necrosis factor in inflammation

Intense research efforts have been directed toward characterizing mediators that control the inflammatory response and regulate the growth, differentiation, and function of cells involved in inflammation. Tumor necrosis factor, or cachectin, and members of a heterogeneous group of peptides called interleukins exhibit a wide spectrum of activities, some of which appear to influence the evolution of inflammatory processes. This review outlines the observations that have led to our current understanding of the biology of tumor necrosis factor and the interleukins. Particular attention is directed toward the evidence suggesting that these cytokines function as mediators of inflammatory responses.

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.

Rheumatoid synovial fluid reconstitutes the B-cell defect in CBA/N mice

Synovial fluid from patients with rheumatoid arthritis (RA-SF) contains a biological activity which can replace T cells for activation of antibody secretion in human blood lymphoid cells and which can also induce the selective differentiation of IgG2b-secreting cells in lipopolysaccharide (LPS)-pre-activated mouse spleen cells. The B-cell activity of this factor was studied in CBA/N mice which have an X-linked B-cell immunodeficiency which manifests itself as a defective humoral response to certain thymus-independent antigens (TI-2). RA-SF has now been shown to reconstitute partly the B-cell deficiency in CBA/N splenic B cells in vitro. Addition of RA-SF to LPS-pretreated cell cultures results in IgG2b secretion in CBA/N spleen cells as well. In contrast to cells from normal CBA mice, cells from CBA/N mice cannot respond to interleukin 4 (IL-4) after addition of LPS with production of IgG1 antibodies in vitro. However, the addition of RA-SF completely restores a normal IL-4-induced IgG1 response. No other biologically active factors have been shown to allow the production of IgG antibody producing cells in CBA/N splenic B cells. It is postulated that the xid immunodeficiency could be the result of a deficient production of a biological activity which is abundant in RA-SF.

Immunotoxins, ligand-toxin conjugates and molecular targeting

Biotechnology provides tools for therapeutic exploitation following advances in the elucidation of protein-to-cell and cell-to-cell interactions. Molecular targeting of bacterial and plant toxins to the desired district of action can be achieved through effector molecules like monoclonal antibodies or protein ligands. Biochemical conjugation of these effectors to SO-6, a single-chain Ribosome Inactivating Protein from Saponaria officinalis, yielded powerful cytotoxic agents that are attractive candidates for therapeutic evaluation. Cloning of the gene for this plant toxin has been achieved. Technologies for expression of protein ligands, such as apolipoproteins or several growth factors, are available in recombinant microorganisms, providing adequate partners for the assembly of targeted chimaeras. Domain engineering of structural and functional regions in effector proteins is now possible and will be carried out with the available technologies to improve existing therapy.

Synovial fluid from rheumatoid arthritis patients induces polyclonal antibody formation in vivo

Our previous studies demonstrated the presence of a T-cell replacing factor in the synovial fluid (SF) of patients with rheumatoid arthritis (RA) and that RA-SF can activate, selectively, the induction of IgG2b antibody secreting cells in lipopolysaccharide (LPS)-pretreated mouse spleen cell cultures. In the present study the effect of RA-SF was tested in vivo in mice. Injection of the polyclonal activator LPS induced the production of IgM and IgG3 secreting cells in normal mice. However, the addition of RA-SF led to a selective increase in the production of IgG2b with a peak response on day 5 and IgG1 plaque-forming cells (PFC) with a peak on day 7. Neither the IgG2b nor IgG1 responses were caused by specific immunity against heterologous proteins present in RA-SF, as injection of in vitro inactive RA-SF samples did not induce PFC. The effect on B cells of RA-SF was further evaluated by injection of RA-SF in combination with LPS to the Xid B-cell deficient CBA/N mice. RA-SF had identical effects in CBA/N as in normal mice. The biological implication of these findings is discussed. Our earlier results support the idea that B cells are endogenously activated in RA patients. We have speculated that this activation is caused by the B-cell differentiation factor which is present in SF. Therefore, we also tested whether RA-SF could influence antibody-forming cells in mice that spontaneously develop autoimmunity. We found that injection of RA-SF alone, in the absence of any other activating substance, induced a very marked increase of IgG producing cells in (NZW x NZB) F1 hybrid mice. From a relatively high background level the RA-SF could still induce an up to 100-fold increase in the numbers of PFC in spleens of such mice.

The role of lymphokines in common variable hypogammaglobulinemia

Common variable (acquired) hypogammaglobulinemia (CVH) is a rare primary immunodeficiency disease of great interest as an immunological model of defects in antibody production. In this article, Gavin Spickett and John Farrant discuss evidence of abnormalities in lymphokine production and responses in the generation of the functional failure. It is not yet clear whether the B cell is intrinsically abnormal or lacks appropriate signals, but the block appears to occur in the differentiation phase of B cells, since membrane (but not secreted) IgG is made. Some T-cell defects also occur in this disease. The cause of CVH is unknown, although a viral aetiology has been suggested. Better understanding of lymphokine networks may allow the provision of specific signals to overcome the block in antibody production.

Enhanced production of interleukin-6 in mice with type II collagen-induced arthritis

We established an interleukin-6 (IL-6)-dependent cell line from murine plasmacytoma MOPC-104E cells. This cell line (designated PIL-6) was found to respond to murine and to human IL-6, but not to any other cytokines. We used this cell line to investigate the involvement of IL-6 production in type II collagen-induced arthritis in DBA/1 mice. Only marginal IL-6 activity was detected in sera from DBA/1 mice inoculated with Freund's complete adjuvant (FCA) alone, with an unrelated protein (bovine serum albumin) plus FCA, or with type II collagen plus Freund's incomplete adjuvant. However, enhanced IL-6 activity was observed in DBA/1 mice that had been injected with type II collagen plus FCA to induce arthritis. The elevated level of serum IL-6 activity was associated with high levels of IL-6 produced when lymph node cells from arthritic mice were stimulated in vitro with type II collagen. We also found that the L3T4+ T cell subset is responsible for the enhanced production of IL-6 in arthritic mice. The results are discussed in the context of potential roles of IL-6 in the induction and/or expression of chronic, progressive arthritis.

Cytotoxic activity of an interleukin 6-Pseudomonas exotoxin fusion protein on human myeloma cells

A chimeric toxin composed of human interleukin 6 (IL-6) attached to a portion of Pseudomonas exotoxin (PE) devoid of its own cell recognition domain has been produced in Escherichia coli. The fusion protein (IL-6-PE40) is cytotoxic to a human myeloma cell line expressing IL-6 receptors but has no effect on IL-6 receptor-negative cells. The specificity of IL-6-PE40 cytotoxicity was demonstrated through competition with excess IL-6 and neutralization with an antibody to IL-6. IL-6-PE40 may be useful in the selective elimination of myeloma cells and other cells with high numbers of IL-6 receptors.

Excessive production of interleukin 6/B cell stimulatory factor-2 in rheumatoid arthritis

High levels of interleukin 6 (IL 6/B cell stimulatory factor-2) were detected in synovial fluids from the joints of patients with active rheumatoid arthritis (RA). The cells found in freshly isolated synovial fluid constitutively expressed IL 6 mRNA. The synovial tissues obtained by joint biopsy were also found to produce IL 6 in vitro. Immunohistochemical analysis demonstrated that CD2+ T cells as well as CD20+ blastoid B cells in the synovial tissues produce IL 6. The data indicate that IL 6 is generated constitutively in RA and its overproduction may explain the local as well as the generalized symptoms of RA, since IL 6 can function as B cell growth and differentiation factor as well as hepatocyte-stimulating factor.

Interleukin-6 in synovial fluid and serum of patients with rheumatoid arthritis and other inflammatory arthritides

Interleukin-6 (IL-6), also called 26-kd protein, hybridoma plasmacytoma growth factor, beta 2-interferon, or B cell stimulatory factor 2, is a recently described human cytokine with multiple growth and differentiation activities. Using a very sensitive bioassay based on the growth factor activity of this protein for B cell hybridomas, we found that IL-6 activity was significantly elevated in synovial fluid from patients with rheumatoid arthritis (RA) or other inflammatory arthritides, as compared with that in a group of patients with osteoarthritis. Moreover, IL-6 was detected in about one-third of the serum samples from patients with RA. In the latter group, we found a significant correlation between serum IL-6 activity and serum levels of C-reactive protein, alpha 1-acid glycoprotein, alpha 1-antitrypsin, fibrinogen, and haptoglobin, which indicates that IL-6 is related to disease activity in patients with RA.

Biological characterization of T cell-replacing factor in the synovial fluid of rheumatoid arthritis patients

The synovial fluid of patients with rheumatoid arthritis (RA) contains a biologically active factor which has the ability to replace T cells for the induction of antibody secretion by human blood lymphoid cells stimulated by pokeweed mitogen (PWM) in vitro. This factor, which will be referred to as RA-SF (synovial fluid), also has the capacity to act as a B cell-stimulatory factor of mouse splenic lymphocytes in the presence of lipopolysaccharide (LPS). Using a test system developed for the definition of interleukin 4 (IL-4), which is a B cell-stimulating lymphokine which preferentially activates the synthesis of selected Ig classes in mouse lymphoid cells, we have shown that RA-SF has properties similar to IL-4 in that it induces differentiation of antibody secretion in the LPS-pretreated mouse cell, but unlike IL-4, which gives IgG1 and IgE, it selectively induces IgG2b synthesis. The present study demonstrates that RA-SF has a biological activity that is reminiscent of other B cell-stimulating mouse lymphokines, but it is biologically distinct from IL-2, IL-4, and IL-5. Recent data also indicate that it is distinct from gamma interferon (IFN-gamma). Therefore, we conclude that the biological activity of RA-SF has properties in common with a T-cell replacing (TRF) and B-cell differentiation factor (BCDF) and probably represents yet another biological activity which so far lacks an experimental counterpart. The relevance of this factor for autoantibody synthesis is discussed.

DNA is a potent immunogen for spleen cells and for guanosine-binding B lymphocytes

The production of antibodies to nucleic acids, and in particular to DNA, has been implicated in the pathogenesis of autoimmune diseases such as systemic lupus erythematosus (SLE). However, little is known about the conditions under which DNA is immunogenic, particularly in well-characterized in vitro systems. Therefore, we examined whether a source of cytokines, in conjunction with D-DNA, permitted a polyclonal or antigen-specific B-cell response. Spleen cells from MRL +/+ SLE-prone mice were incubated with supernatant from concanavalin A-stimulated spleen cells (Con A SN, a source of cytokines) and D-DNA. A potent antibody response developed to guanosine (GU) and D-DNA but not to fluorescein (FL), using as little as 10 ng D-DNA in conjunction with Con A SN. In order to further examine the cellular requirements for D-DNA to be immunogenic, populations of B cells which bound GU (an immunodominant epitope of DNA) or an irrelevant FL-binding population were purified and incubated with DNA and Con A SN. Interestingly, GU-binding, but not FL-binding B cells could be triggered by D-DNA derived from calf thymus, a result suggesting that DNA was not acting simply as a polyclonal B-cell activator. D-DNA optimally triggered GU+ B cells within a narrow dose range similar to many thymus-independent Type II antigens with repetitive determinants. If DNA were truly an autoantigen, then DNA derived from the MRL +/+ mouse should be capable of triggering GU-binding B cells. When this hypothesis was tested, D-DNA, but not N-DNA, functioned as a potent immunogen. These experiments document the ability of DNA to act as a specific immunogen and suggest that, under appropriate conditions, nucleic acid may induce autoantibody production in vivo.

The essential role of B cell stimulatory factor 2 (BSF-2/IL-6) for the terminal differentiation of B cells

The role of recombinant B cell stimulatory factor 2 (BSF-2/IL-6) in the regulation of growth and differentiation of B cells was investigated. rBSF-2 at 200 pg/ml could induce 50% of the maximum Ig production in B lymphoblastoid cell lines, the specific activity being estimated as 5 X 10(6) U/mg. rBSF-2 augmented PWM-induced IgM, IgG, and IgA production in mononuclear cells (MNC); the effect was exerted by directly acting on PWM-induced B blast cells to induce Ig production. However, rBSF-2 did not induce any growth of activated B cells. In contrast, rBSF-2 showed a potent growth activity on a murine hybridoma clone, MH60.BSF2. The concentration required for half-maximal [3H]TdR uptake was approximately 5 pg/ml, which was 40 times less than that required for Ig induction in a B cell line. Anti-BSF-2 antibody inhibited PWM-induced Ig production in MNC, but not PWM-induced proliferation. The antibody was effective even when added on day 4 of an 8-d culture, indicating that BSF-2 is one of the essential late-acting factors in PWM-induced Ig production.

Production of tumour necrosis factor-alpha, interferon-gamma and interleukin-2 by peripheral blood mononuclear cells of subjects suffering from rheumatoid arthritis

Using radio-immunoassay methods, the production of tumour necrosis factor-alpha (TNF-alpha), interleukin-2 (IL-2), and interferon-gamma (IFN-gamma) released by peripheral blood mononuclear cells (PBMC), maintained in culture and stimulated by phytohemagglutinin (PHA), was measured in normal subjects and patients with active or inactive rheumatoid arthritis (RA). Results indicated a dissociation between mitogenic response and secretion of mediators by PBMC under the influence of PHA in both normal controls and in patients with rheumatoid arthritis (RA). While [3H]thymidine incorporation was characterized by a rather bell-shaped curve with increasing concentrations of PHA, IL-2 and TNF-alpha displayed a linear dose-dependent increase. [3H]thymidine uptake by PBMC was in the same range in normal subjects as in patients with active and inactive RA, although cytokine secretion differed. The PBMC of patients with active RA produced less TNF-alpha, IL-2, and IFN-gamma than did those of the controls. In cases of inactive RA, the secretory response varied from subject to subject; mean values did not differ from those of normal subjects, except for those of IL-2 (p less than 0.01). The significance and the clinical relevance of these findings are discussed.

Characterization of IL-2 responsive synovial T lymphocytes in rheumatoid arthritis. II. Functional properties

Lymphocytes from peripheral blood (PBL) and synovial fluid (SFL) were obtained from patients with rheumatoid arthritis (RA) and cloned under limiting-dilution conditions without prior activation but in the presence of exogenous interleukin (IL)-2. The precursor frequencies of such in vivo activated IL-2-responsive cells were higher in RA SFL (1/83) than in RA PBL (1/201) or normal PBL (1/377). These HLA-Dr/Ia-positive clones expressed T-cell markers CD3 and T101 and were either CD4- or CD8-positive but lacked NK markers CD11, CD16, and HNK-1. All such clones were cytotoxic for NK-sensitive K562 targets and NK-insensitive Raji cell targets. These cells, which most closely resemble nonmajor histocompatibility complex (MHC) restricted cytotoxic T (CTL) cells, are present with increased frequency in RA synovial fluids.

T cytotoxic and helper cells are markedly increased, and T suppressor and inducer cells are markedly decreased, in rheumatoid synovial fluids

Synovial fluid lymphocytes and paired peripheral blood lymphocytes from 28 patients with rheumatoid arthritis were analyzed by 2-dimensional flow cytometry. We found that the composition of the lymphocyte population is different in synovial fluid compared with that in peripheral blood, in that there were increased proportions of Ia+ Leu-2a+/Leu-15- (T cytotoxic) cells and Leu-3a+/Leu-8- (T helper) cells, together with marked decreases in Leu-2a+/Leu-15+ (T suppressor) cells and Leu-3a+/Leu-8+ (T inducer) cells. These findings suggest that the unique composition of synovial fluid lymphocytes might be the result of T cell activation by some mechanism that is not known.

Age-associated changes in proliferative and differentiative response of human B cells and production of T cell-derived factors regulating B cell functions

The abilities of highly purified B cells to repeat replication for clonal expansion and to differentiate into immunoglobulin secreting cells (ISC) were examined in the aged and young groups. B cells from the aged showed twofold less proliferative response to B cell mitogen Cowan 1 (SAC) than those from the young. The original clone size of SAC responding B cells determined by colchicine block and [3H] thymidine [( 3H] TdR) uptake was not significantly reduced in the aged whereas the ability to repeat replication to expand clonal size was significantly reduced. B cells from aged and young persons were induced into ISC by combined stimulation with SAC and partially purified B cell differentiation factor (BCDF) free of IL-2 activity. ISCs for IgG and IgA were rather increased or at least not reduced in number in the aged as compared with those in the young. We also determined the IL-2 and BCDF activity produced by T cells from aged and young persons. Upon PHA stimulation, the aged T cells produced tenfold less IL-2 activity and threefold higher BCDF activity than did young T cells. Approximately threefold increase in spontaneous secretion of BCDF activity by aged T cells was found as compared with young T cells. The inverse correlation between the IL-2 activity and BCDF activity was found when both activities were determined in the same samples.

Modulation of spontaneous immunoglobulin production by natural killer cells in rheumatoid arthritis

Synovial fluid (SF) mononuclear cells obtained from patients with rheumatoid arthritis (RA) spontaneously produce large amounts of immunoglobulin. In the rheumatoid joint, natural killer (NK) cell activity is reduced in comparison with that in the peripheral blood (PB). We examined the ability of SF NK cells to modulate the spontaneous production of Ig in RA SF, and we contrasted this with the activity in PB from RA patients and from normal subjects. We found that the spontaneous production of IgG was greater in RA SF than in RA or normal PB. The baseline NK activity was significantly lower in RA SF than in RA or normal PB (P less than 0.005). Incubation with anti-Leu-11b and complement reduced NK activity in PB, but not in SF, and it significantly (P less than or equal to 0.021) increased IgG production in both RA SF and RA PB. Lysis of NK cells in this manner also resulted in a significant increase (P less than 0.02) in IgM production in RA SF. These results suggest that NK cells with a Leu-11b phenotype down-regulate the ongoing synthesis of IgG and IgM in the rheumatoid joint.

Stimulation of mouse B cells by a factor that coisolates with T-cell proteoglycan

We have isolated a factor that copurifies with chondroitin sulfate proteoglycan secreted by mouse splenocytes and some murine T-cell hybridomas. This factor will stimulate proliferation and plaque-forming cell differentiation of B lymphocytes from mouse spleens, even after T cells have been depleted (less than 2% Thy 1.2-bearing cells). Adherent macrophages enhance the activity of this factor, but their function can be replaced in macrophage- and T-cell-depleted populations by small concentrations of a protein mitogen from Salmonella typhimurium. The stimulatory fraction contains chondroitin sulfate, a major protein which has a molecular weight of 74,000 and a minor moiety at 50,000. Stimulatory activity of this material is destroyed by (i) boiling, (ii) mild alkali treatment, and (iii) protease digestion. It is unaffected by RNase and chondroitinase treatments, suggesting that the factor is a protein. Our data define a new B-cell stimulatory substance(s) and suggest that it may be associated with chondroitin sulfate proteoglycan secreted by immune cells.

A rheumatoid arthritis B cell subset expresses a phenotype similar to that in chronic lymphocytic leukemia

An abnormal subpopulation of B cells expressing the T1 antigen, which is normally restricted to T cells, was demonstrated in the peripheral blood of 16 patients with rheumatoid arthritis. This T1+ B cell population accounted for a mean of 19.6% (upper limit 48%) of the circulating B cells and did not correlate with clinical disease activity, rheumatoid factor, or drug treatment. The highest percentage of T1+ B cells found in the blood of 8 patients with connective tissue diseases, including systemic lupus erythematosus, was 5% of the B cells, and for normal controls, it was was 3% of the B cells. As previously reported, we confirmed that the T1+,Ig+ phenotype was a feature of leukemic cells in B-type chronic lymphocytic leukemia. The finding of increased numbers of T1+ B cells in patients with rheumatoid arthritis and those with B-type chronic lymphocytic leukemia raises the possibility that these cells play a role in a spectrum of diseases, including those involving autoimmunity and malignancy.

Effect of drug therapy on circulating and synovial fluid Ig-secreting cells in rheumatoid arthritis

A common immunological abnormality in rheumatoid arthritis (RA) is an increased spontaneous polyclonal B cell activation. In order to study the influence of drug therapy in RA on the functional activity of B cells we enumerated spontaneous plaque-forming cells (PFC) in peripheral blood lymphocytes (PBL) and synovial fluid lymphocytes (SFL) by a reverse haemolytic plaque assay. Spontaneous IgG-, IgM-, and IgA-PFC in PBL of 26 patients with classical erosive RA receiving either gold salts or D-penicillamine were similar to those observed in 20 healthy controls. In contrast, significantly higher numbers of IgG- and IgA-PFC, but not IgM-PFC, were found in PBL of nine patients with classical erosive RA receiving non-steroidal anti-inflammatory drugs (NSAID) alone. Furthermore, spontaneous PFC in SFL from 16 consecutive patients with RA receiving second-line drugs, as well as 17 patients with other forms of arthritis (non-RA) were generally low and significantly less than those observed in 20 RA patients on NSAID alone. Moreover, a wide individual variation in PFC, especially in relation to the IgG class, was recorded in the synovial lymphocytes. These studies imply that treatment with second-line drugs is associated with normalisation of B cell activity in RA patients, and that the effect can be detected at the cellular level both in blood and synovial fluid.

Adjuvants influence the immunoglobin subclass distribution of immune responses in vivo

Mice were immunized against fluorescein isothiocyanate (FITC)-labelled human gamma globulin (HGG) in the absence or presence of different adjuvants. The immune response was assayed every other day with regard to both total Ig-secreting cells and FITC-specific plaque-forming cells (PFC). The adjuvants influenced the type of immune response induced to the same antigenic determinant. Thus, addition of Freund's complete (FCA) or incomplete (FIA) adjuvant preferentially led to the secretion of IgG1 PFC of an average high affinity. Most newly appearing IgG-secreting cells were also detected as FITC-specific PFC. The use of lipopolysaccharide (LPS) as an adjuvant resulted in the induction of both IgM and IgG, particularly of the IgG3 and IgG2b subclasses. However, these antibodies had relatively low affinity, and a large number of total IgG-secreting cells induced by LPS had no detectable FITC specificity. The FCA/FIA- and LPS-induced responses to FITC-HGG were additive when injected together, indicating that they act on distinct subpopulations of B lymphoid cells. The adjuvant response to LPS, but not the response to FCA/FIA, was totally absent in mice of the C3H/Hej strain, which are non-responders to the polyclonal activating properties of LPS. Finally, the response induced by FCA or FIA was T-cell-dependent and the LPS response T-cell-independent as assayed in nude mice.

Subclasses of IgG produced in the rheumatoid synovium

The subclass distribution of IgG plasma cells was studied in sections of rheumatoid synovial tissue from 15 cases with seropositive rheumatoid arthritis and 8 cases with various types of seronegative arthritis, using the immunofluorescence technique and monoclonal IgG-subclass-specific antibodies. In most tissues, plasma cells of all the four subclasses were present, and IgG1 was usually the dominating subclass. The frequency of IgG3 plasma cells was usually higher than that of IgG2. The results are partly in contrast with previous observations and do not give evidence for a subclass-specific polyclonal B-cell activator, growth factor or differentiation factor.