Inhibitor of interleukin-2 synthesis and response in rheumatoid synovial fluid

Establishment of a natural suppressor cell line producing soluble suppressor factor other than transforming growth factor-beta

Natural suppressor (NS) cell line (Clone 59) was established from the bone marrow of adult C3H/Hej mice in the presence of WEHI-3 conditioned media. Clone 59 cells suppressed the generation of cytotoxic T lymphocytes from normal mouse spleen. This suppression was seen at a responder-to-suppressor cell ratio of 1000:1 and lacked antigen specificity or MHC restriction. Clone 59 cells expressed the 'null' surface phenotype (Thy1.2-, CD3-, Lyt-2-, L3T4-, surface Ig-, MAC-1-) by immunofluorescent staining. Clone 59 cells exhibited no cytolytic activity against NK cell-sensitive YAC-1 and natural cytotoxic L929 target cell lines. Non-specific suppression, with a cell-free supernatant from the Clone 59-NS cells, also was observed. The supernatant did not inhibit [3H]-thymidine uptake by CTLL-2 cells which were proliferating in response to IL-2. Anti-transforming growth factor-beta (TGF-beta) monoclonal antibody had no effect on suppression, suggesting that the non-specific suppression is mediated by some soluble factors other than TGF-beta. Clone 59 cells may be useful in identifying non-specific suppressor cells in adult bone marrow and studying their functional role in the regulation of tolerance and self-reactivity.

Impaired generation of high-affinity interleukin-2 receptors in the autologous mixed lymphocyte reaction in rheumatoid arthritis

We examined the expression of high-affinity interleukin (IL)-2 receptors (IL-2R) as well as Tac and HLA-DR antigens on peripheral blood (PB) T cells from 11 rheumatoid arthritis (RA) patients and 8 healthy controls induced in the autologous mixed lymphocyte reaction (AMLR). The proportion of HLA-DR- and Tac-bearing T cells and expression of these activation antigens were higher in patients relative to controls (P less than 0.01) in freshly isolated unstimulated PB mononuclear cells. AMLR stimulation of RA T cells failed to induce an increase in the proportion of HLA-DR and Tac-bearing T cells which was observed in health controls. After AMLR stimulation the number of high-affinity IL-2R were significantly lower in RA patients compared with controls (P less than 0.01). The number of high-affinity IL-2R on patient T cells correlated strongly with AMLR reactivity as measured by [3H]thymidine incorporation (r = 0.821, P = 0.002). The results suggest that the AMLR defect in RA may result from impaired generation of high-affinity IL-2R.

Mechanism of T-cell activation by mycobacterial antigens in inflammatory synovitis

Earlier studies demonstrated enhanced proliferative responses to an acetone precipitable Mycobacterium tuberculosis (AP-MT) antigenic complex by T lymphocytes from the synovial fluid, compared with the peripheral blood, of patients with inflammatory synovitis, including rheumatoid arthritis. In contrast, decreased proliferation and interleukin 2 (IL-2) production in response to mitogens by synovial fluid lymphocytes from patients with rheumatoid arthritis has been demonstrated. In order to determine if IL-2 was produced in response to AP-MT, the peripheral blood and synovial fluid of patients with inflammatory arthritis were analysed by measuring proliferation and IL-2 production in response to AP-MT and tetanus toxoid. A reduction of IL-2 production relative to proliferation was observed in some, but not all, synovial fluids of patients who responded to the AP-MT. Nevertheless, antibodies to IL-2 as well as interleukin 4 (IL-4), significantly inhibited proliferation of synovial fluid lymphocytes by AP-MT. There was no inhibition by antibodies to interleukin 6 (IL-6). We conclude that AP-MT induced proliferation by synovial fluid lymphocytes is mediated by both IL-2 and IL-4.

Synovial membrane histology and immunopathology in rheumatoid arthritis and osteoarthritis. In vivo effects of antirheumatic drugs

We examined the histologic and immunopathologic features of the synovial membrane of 18 patients with rheumatoid arthritis (RA) and 12 patients with osteoarthritis (OA) who had undergone total knee arthroplasty. Patients were classified into 5 groups according to therapeutic regimen and disease: RA treated with nonsteroidal antiinflammatory drugs (NSAIDs), RA treated with NSAIDs and prednisone, RA treated with NSAIDs and methotrexate (MTX), OA treated with analgesics, and OA treated with NSAIDs. There were no significant between-group differences in the percentages or the distribution pattern of the infiltrating T cell subsets (CD4, CD8), HLA-DR, or interleukin-2 receptor-bearing cells. However, inflammatory indices, which included the thickness of the lining cell layer and the density of the mononuclear cell infiltrate, were significantly higher in the RA patients treated with prednisone and those treated with MTX (P less than 0.05). Similarly, fibrosis was markedly reduced in these 2 groups. The RA patients treated with NSAIDs alone and the 2 groups of patients with OA demonstrated similar profiles. These data suggest that prednisone and MTX may inhibit the development of fibrosis without altering the subsets of the inflammatory cell population. This observation raises the possibility that the action of these 2 drugs may be partly mediated by the suppression of inflammatory mediators that are responsible for fibroblast activation.

Activation pathways of synovial T lymphocytes. Expression and function of the UM4D4/CDw60 antigen

Accumulating evidence implicates a central role for synovial T cells in the pathogenesis of rheumatoid arthritis, but the activation pathways that drive proliferation and effector function of these cells are not known. We have recently generated a novel monoclonal antibody against a rheumatoid synovial T cell line that recognizes an antigen termed UM4D4 (CDw60). This antigen is expressed on a minority of peripheral blood T cells, and represents the surface component of a distinct pathway of human T cell activation. The current studies were performed to examine the expression and function of UM4D4 on T cells obtained from synovial fluid and synovial membranes of patients with rheumatoid arthritis and other forms of inflammatory joint disease. The UM4D4 antigen is expressed at high surface density on about three-fourths of synovial fluid T cells and on a small subset of synovial fluid natural killer cells; in synovial tissue it is present on more than 90% of T cells in lymphoid aggregates, and on approximately 50% of T cells in stromal infiltrates In addition, UM4D4 is expressed in synovial tissue on a previously undescribed population of HLA-DR/DP-negative non-T cells with a dendritic morphology. Anti-UM4D4 was co-mitogenic for both RA and non-RA synovial fluid mononuclear cells, and induced IL-2 receptor expression. The UM4D4/CDw60 antigen may represent a functional activation pathway for synovial compartment T cells, which could play an important role in the pathogenesis of inflammatory arthritis.

Stimulation of rheumatoid synovial and blood T cells and lines by synovial fluid and interleukin-2: characterization of clones and recognition of a co-stimulatory effect

Rheumatoid arthritis (RA) is characterized by the presence of interleukin-2 (Il-2) receptor-positive T cells in the peripheral blood and synovial compartments. Utilizing the limiting dilution technique, the precursor frequencies of Il-2 responsive T cells were determined in peripheral blood and synovial sites from RA patients and in the blood of normal donors. The frequencies of Il-2 responsive T cells were significantly higher in RA patients (range from 1/180 to 1/7432) compared to normal donors (range from 1/400 to 1/8163). T-cell clones raised by the addition of Il-2 alone were predominantly of the CD4-positive phenotype. Peripheral blood T cells, synovial T-cell clones and lines derived from RA patients were co-stimulated with Il-2 and synovial fluid or supernatants from cultured synovial lining cells. This co-stimulation induced a strikingly enhanced proliferative T-cell response while synovial fluid alone was without effect. This stimulatory activity was found in the high molecular weight range (approximately 150 kDa) and could not be attributed to the action of immunoglobulins or known cytokines such as Il-2 or interleukin-1 (Il-1), suggesting the activity of a material that modulates the Il-2-dependent growth of T cells. The co-stimulatory capacity of synovial fluid with Il-2 may be relevant to the activated state, especially of synovial T cells.

Low levels of interleukin-4 and high levels of transforming growth factor beta in rheumatoid synovitis

Since interleukin-4 (IL-4) displays agonistic effects on both T and B cells, we studied whether this lymphokine is involved in rheumatoid synovitis, a disease characterized by intense T cell infiltration and B cell stimulation. Rheumatoid arthritis synovial fluids (RA SF) contained no (less than 15 pg/ml) or very low amounts (less than 25 pg/ml) of IL-4, as measured by a sensitive and specific enzyme-linked immunosorbent assay. No IL-4 was produced by unstimulated rheumatoid synovial membrane. RA SF were found to inhibit phorbol myristate acetate (PMA)-dependent proliferation of normal peripheral blood lymphocytes (PBL). An inhibitory fraction with an apparent molecular weight of 150 kd was isolated by gel filtration. The inhibitory fraction strongly blocked the proliferation of PBL induced by PMA, PMA + IL-2, or PMA + IL-4. However, this fraction was less effective in blocking the proliferation of PBL induced by PMA + IL-2 + IL-4. High levels of transforming growth factor beta (TGF beta) were found in these RA SF, and an anti-TGF beta antibody was able to partially reduce the inhibitory activity. RA SF were found to inhibit phytohemagglutinin-induced IL-4 production by PBL. These data indicate that IL-4, similar to other T cell lymphokines, cannot be detected in RA SF and that RA SF contains an inhibitory activity, related in part to TGF beta, which blocks mitogen-induced proliferation of PBL, at least in part through an inhibition of T cell-derived lymphokine release.

A study of the effect of rheumatoid synovial fluid on proliferation and IL-2 production by total mononuclear cells and purified CD4+ cells of synovial fluid and peripheral blood

T cells from synovial fluid (SF) of rheumatoid arthritis (RA) patients have previously been shown to proliferate less after mitogenic stimulation and produce less interleukin 2 (IL-2) than normal T cells. To test whether SF is responsible for the reduced T-cell responses, we studied the effect of inflammatory SF on peripheral blood (PB) RA and normal mononuclear cells (MNC) and CD4+ T cells and on RA SF MNC and CD4+ cells in vitro. Most rheumatoid SF present in concentrations of 50% and 5% during in vitro stimulation increased mitogen-induced IL-2 production and proliferative response by normal PB and RA MNC and CD4+ cells. Other rheumatoid SF samples did not influence the T cell responses, while only a few samples had an inhibitory effect. The results indicate that SF contain both stimulatory and inhibitory factors and that the resultant effect on T cells may depend on the net effect of these. The results do not support the hypothesis that the apparently impaired function of SF T cells is due to contact with SF.

Interleukin-2 inhibitor in rheumatoid arthritis synovial fluid does not inhibit mononuclear cell responses to mitogens

Synovial fluid (SF) from rheumatoid arthritis (RA) patients were tested for their ability to inhibit the proliferative responses of normal peripheral blood mononuclear cells (PBM) to mitogens and interleukin-2 (IL-2). SF significantly inhibited the responses to concanavalin A (CON A) and phytohaemagglutinin (PHA), but significantly enhanced the responses to IL-2. Similarly, SF mononuclear cells (SFM) were hyporesponsive to CON A and PHA compared with autologous PBM, but hyper-responsive to IL-2. It is concluded that an IL-2 inhibitor in RA SF is unlikely to be the cause of SFM hyporesponsiveness to mitogens.

A contra-IL-2 cytokine derived from mice suppressed for collagen-induced arthritis

The present study identifies and characterizes a cytokine derived from a T cell hybridoma which inhibits interleukin-2 (IL-2) function. The T cell hybridoma, T101N, was derived from somatic cell hybridization of lymphoid cells from mice suppressed for collagen-induced arthritis. Serial dilution of T101N cell culture medium reveals a concentration-dependent inhibition of recombinant IL-2 induced proliferation. Physiochemical properties of the inhibitor indicate that the contra-IL-2 activity is optimally resolved at 37 degrees C and neutral pH. Analysis of the molecular characteristics of the contra-IL-2 activity indicate that the cytokine activity is most biologically active as a pentimeric molecule of high molecular weight. Apparent molecular weight of monomeric contra-IL-2 is approximately 30,000-35,000 Da.

Soluble interleukin-2 receptor: elevated levels in serum and synovial fluid of patients with rheumatoid arthritis

Soluble interleukin-2 receptor (sIL-2R) levels were quantitated in the serum and synovial fluid (SF) of patients with rheumatoid arthritis (RA) and degenerative joint disease (DJD). A sandwich immunoassay, employing two monoclonal antibodies against distinct epitopes on the IL-2R, was utilized for measurement. We found a striking elevation of sIL-2R in RA SF as compared with DJD SF (RA, 1319 +/- 135; DJD, 416 +/- 59; p less than 0.001). RA serum sIL-2R levels were also significantly elevated over DJD levels. There was no interaction between rheumatoid factor (RF) and sIL-2R. RA patients with elevated sIL-2R levels had significantly longer disease duration, higher c-reactive protein (CRP) levels in serum and SF, and higher RF levels in serum and SF. The groups were similar in regard to other laboratory variables. The presence of elevated levels of sIL-2R in RA serum and SF confirms the presence of a heightened immune reactivity and in vivo activation of lymphocytes in RA.

T cell inhibitor secreted by macrophages and endothelial cells

On stimulation with lipopolysaccharide (LPS), normal human macrophages (M phi) and endothelial cells (EC) produced factors which inhibited interleukin 2 (IL-2)-dependent lymphocyte proliferation and PHA plus interleukin 1 (IL-1)-dependent mouse thymocyte proliferation but not IL-1-dependent human fibroblast proliferation, suggesting that they were inhibitors of the IL-2 response. In addition, these factors inhibited the production of IL-2 by normal human peripheral blood mononuclear cells (PBMC). The factors also inhibited PBMC proliferation in response to PHA and concanavalin (Con A) but did not inhibit the proliferation of EC, U937 cells, or Epstein-Barr virus-transformed B cells. On Sephadex G200 gel filtration, the inhibitory factors from both M phi and EC were detected almost entirely in a 130- to 150-kDa fraction, but active material was also detected in a 15- to 20-kDa fraction. On isoelectric chromatofocusing of the 130- to 150-kDa fraction, inhibitory activity was associated with fractions eluted at three isoelectric points, pH 7.0, 5.4, and 4.8. The isoelectric fractions isolated from M phi and EC showed similar patterns of inhibition. When 130- to 150-kDa fractions from Sephadex G200 of the M phi and EC supernatants were treated with an antibody against a macrophage-derived suppressor factor produced by the human monocytic leukemia cell line THP-1, the activity of both fractions was neutralized. The above findings suggest that normal M phi and EC secrete an identical or closely related inhibitor of IL-2 synthesis and IL-2 response, and this inhibitor regulates these IL-2-related functions by a suppressive action on the T lymphocyte.

New diagnostic tools and methodological approaches: an outlook to the future

In spite of recent progress, the aetio-pathogenesis of a large number of osteoarticular diseases is as yet not well known. This is apparent for commonly occurring diseases such as osteoarthritis (OA), rheumatoid arthritis (RA), type I osteoporosis (post-menopausal) and type II osteoporosis (senile). As a result of the lack of knowledge about these pathogenic factors, therapeutics often remain symptomatic and not completely satisfactory. Nowadays there is a need for methodological tools to explore the causes or pathogenic factors of these conditions. Moreover, in OA, there is at present no way to predict the development of this disease and to follow its evolution, hence, there is a need for specific markers. These biological and methodological developments are useful for searching for new molecules able to compensate for the pathogenic anomalies demonstrated in RA and OA. In this paper, we will discuss some of the methodological developments now in progress which may provide solutions to some of the aetiopathogenic, diagnostic and therapeutic problems related to RA and OA.

Defective induction of T-cell help and natural killing following anti-CD3 stimulation of autoimmune lymphocytes

Anti-CD3 monoclonal antibody (MoAb) stimulates T cells in normal peripheral blood to proliferate and develop cytotoxic activity against NK-sensitive tumor cell lines. We now find that anti-CD3 MoAb also generates cytotoxic activity against a cell line (MEL-21) resistant to classical NK cell killing. After activation in vitro with anti-CD3 MoAb for 18 h, normal peripheral blood mononuclear cells (PBMNC) develop more HLA-DR-positive helper than suppressor T cells, manifest a functional helper effect as measured by increased IgG synthesis (P less than 0.01), as well as kill MEL-21 target cells. PBMNC from rheumatoid arthritis (RA) patients respond normally but mononuclear cells from rheumatoid arthritis synovial fluid (RASF) respond poorly. PBMNC from systemic lupus erythematosus (SLE) patients also respond poorly to anti-CD3 stimulation. Thus, the ability of anti-CD3 to stimulate IgG production and generate enhanced natural cytolytic activity are defective in both RASF and SLE lymphocytes.