Serum concentrations of soluble interleukin 2 receptor in patients with rheumatoid arthritis: effect of second line drugs

Advances in interleukin 2 receptor targeted treatment

T cell activation and cellular immune responses are modulated by interleukin 2 (IL2) through binding to its corresponding cell surface receptor. Three forms of the receptor are recognised based on IL2 binding affinity. The high affinity receptor is a heterotrimer composed of alpha, beta, and gamma(c)-polypeptide chains. The 55 kDa alpha-chain also known as the Tac (T cell activation) antigen or CD-25 is a unique subunit of the high affinity IL2 receptor (IL2Ralpha). Resting T cells express few IL2Ralpha, however, when activated, the expression of ILR2alpha rapidly increases. The IL2Ralpha is shed from the cell surface and is measurable in the serum as a 45 kDa soluble form (s-Tac or s-IL2Ralpha). Serum concentrations of s-Tac can be used as a surrogate marker for T cell activation and IL2Ralpha expression. IL2Ralpha is over expressed by T cells in a number of autoimmune diseases, allograft rejection and a variety of lymphoid neoplasms. IL2 induced proliferation of T cells can be inhibited by the murine monoclonal antibody (anti-Tac) directed against the alpha-chain of the IL2R. Through molecular engineering, murine anti-Tac has been humanised reducing its immunogenicity without changing its specificity. Humanised anti-Tac (HAT) has been shown to reduce the incidence of renal and cardiac allograft rejection as well as decrease the severity of graft versus host disease in patients undergoing HLA matched allogeneic bone marrow transplantation. IL2Ralpha targeted treatment with radioimmunoconjugates of anti-Tac and immunotoxins has shown promise in the treatment of CD25 expressing lymphomas.

Serum interleukin-2 receptor for the early diagnosis of rheumatoid arthritis

The value of measuring soluble interleukin-2 receptor (sIL-2R) in the sera of patients with joint pain as a predicting parameter for the future development of rheumatoid arthritis (RA) was examined. sIL-2R was measured by the ELISA method. Sixty-four patients with joint pain (suspected RA: sus-RA) but no bone or joint destruction were enrolled over 2 years and 47 were selected for the study. Eleven patients whose diagnosis was sus-RA after a year of observation were successively followed-up for 5 years. Two-thirds of the patients whose sIL-2R levels were higher than those of normal healthy adults (< 82 pmol/l; mean +2SD) developed RA within a year. On the other hand, one-quarter of the patients with normal levels of sIL-2R also developed RA within a year. The presence of two or three of the following three items in patients with joint pain without any bone and joint destruction was thus indicated to be useful for the early diagnosis of RA: elevated CRP level (> or = 1.0 mg/dl), positive rheumatoid factor (RF) (> or = 30 IU/ml) and an elevated sIL-2R level (> or = 100 pmol/l). Sensitivity and specificity were 72.7% and 96.0%, respectively. The probability of development of RA is expressed as P = 1/[1 + exp(2.673 - 0.01784 x sIL-2R - 0.4398 x CRP - 0.004835 x RF)], with R2 = 0.3083 and p<0.0005. On the other hand, the sIL-2R levels did not correlate with any future bone or joint changes within a year of observation. The above criteria may therefore hopefully justify the early treatment of patients with joint pain using drugs that can modify the patients' immune function. However, the validity of these criteria still need to be examined more thoroughly in the future.

Effects of antirheumatic agents on cytokines

A review of the literature concerning the effects of traditional antirheumatic drugs on cytokines and the cytokine and anticytokine approaches already used in the therapy of rheumatoid arthritis (RA) is presented. Many antirheumatic drugs are capable of cytokine modulation in vitro. Corticosteroids inhibit the transcription of a broad spectrum of genes including those encoding monocyte, T cell-derived cytokines and several hemopoietic growth factors, whereas drugs such as cyclosporin A and D-penicillamine interfere with T cell activation more specifically by suppressing interleukin 2 (IL-2) production. The in vivo effects of drug therapy on cytokines in RA patients are less well established. Gold compounds reduce circulating IL-6 levels and the expression of monocyte-derived cytokines, such as IL-1, tumor necrosis factor (TNF), and IL-6, in the rheumatoid synovium. Decreases in circulating IL-6, soluble IL-2 (sIL-2R), and TNF receptors and in synovial fluid IL-1 levels have been reported with methotrexate. Reductions in circulating IL-6 and sIL-2R concentrations have also been observed with cyclosporin and corticosteroids, whereas azathioprine reduces IL-6 but not sIL-2R. Studies on sulfasalazine are conflicting and the in vivo effects of D-penicillamine and antimalarials have not been studied yet. Interferon gamma therapy is not effective in RA but may prove a useful antifibrotic for systemic sclerosis. Colony stimulating factors improve the granulocytopenia associated with Felty's syndrome or drug toxicities but can induce arthritis flares and should be reserved to treat infectious complications. Promising results are being obtained with selective antagonism of TNF and IL-1 in RA, and combinations of anticytokine strategies with traditional antirheumatic drugs have been already envisaged. These should preferably be based in a broader knowledge of the effects of antirheumatic agents on the cytokine network.

Serum soluble interleukin-2 receptor levels in rheumatoid arthritis: effect of methotrexate, sulphasalazine and hydroxychloroquine therapy

The aim of this study was to assess the correlations of the serum soluble interleukin 2 receptor (sIL-2R) concentrations with disease activity parameters and response to treatment with second line drugs in patients with rheumatoid arthritis (RA). Sixty-seven patients with active disease completed a 24-week, open, randomized study of methotrexate (MTX) versus sulphasalazine (SSZ) or hydroxychloroquine (HCQ). Serum sIL-2R levels were evaluated before entry and after 24 weeks by ELISA. Serum sIL-2R were significantly higher in RA patients than in controls (P = 0.0001) and correlated significantly only with erythrocyte sedimentation rate (P = 0.03) and with Chronic Arthritis Systemic Index (P = 0.01) at study entry. No correlation was found between serum sIL-2R and other laboratory and clinical indices of disease activity. After 24 weeks of treatment no differences in serum sIL-2R in comparison with basal levels were found in either responding or in non-responding patients, although the mean reduction of sIL-2R was more marked in the MTX-treated cohort than in the HCQ and SSZ-treated groups. These data suggest that in RA the measurement of sIL-2R should be used with caution as an isolated index of disease activity and that it is not a useful marker of response to treatment with second line drugs.

Effect of cyclosporin A on interleukin-6 and soluble interleukin-2 receptor in patients with rheumatoid arthritis

OBJECTIVE

To investigate the effect of cyclosporin A (CyA) therapy on circulating concentrations of interleukin-6 (IL-6) and soluble interleukin-2 receptor (sIL-2R) in patients with rheumatoid arthritis (RA).

METHODS

Twenty four RA patients with active disease were studied. Plasma was collected before and after 16 weeks of CyA treatment. IL-6 was measured by B9 bioassay and sIL-2R by enzyme linked immunosorbent assay (ELISA).

RESULTS

The initial median IL-6 concentration of 165 IU/ml decreased significantly to 71 IU/ml after 16 weeks (p < 0.05). Similarly, the initial median plasma sIL-2R value of 665 U/ml decreased significantly to 570 U/ml (p < 0.05). This decrease was accompanied by an improvement in clinical parameters of disease activity. Some association between sIL-2R, IL-6, haemoglobin, and platelets was also observed.

CONCLUSIONS

This study has demonstrated that, in vivo, CyA therapy in RA can significantly reduce circulating concentrations of IL-6 and sIL-2R. Modulation of both T and non-T cell derived cytokines may be one mechanism by which CyA improves rheumatoid disease. Whether this is a direct effect of CyA on the cells within the rheumatoid joint producing these cytokines or an indirect effect mediated by other cytokines which can influence IL-6 and Il-2R values remains to be determined.

Soluble interleukin-2 receptor in sera and synovial fluids of rheumatoid patients: correlations with disease activity

The measurement of serum soluble interleukin-2 receptor (sIL-2R), a sensitive marker of lymphocyte activation, has been proposed as an indicator of disease activity and "outcome" in patients with inflammatory diseases characterized by the activation of immune cells. Serum sIL-2R levels have been reported higher in rheumatoid patients than in controls. Using an enzyme-linked immunoabsorbent assay (ELISA), we evaluated soluble IL-2R levels in the serum of 34 patients with RA and in the synovial fluid of 25 of these patients and we compared it with levels found in the serum of 13 healthy controls. Serum sIL-2R levels were significantly elevated in RA patients compared with the healthy age-matched control group (P < 0.005). The mean level of soluble IL-2R in synovial fluids was significantly higher than the mean sera levels in RA patients (P < 0.0001). Moreover, we examined the correlation between serum and synovial fluid sIL-2R levels and disease activity measures. Serum sIL-2R correlated only with ESR (P < 0.04). The synovial fluid sIL-2R correlated with ESR (P < 0.02) and a visual analogue scale (VAS) pain score (P < 0.04). Both serum and synovial fluid sIL-2R levels correlated with the chronic arthritis systemic index (CASI; P < 0.04 and P < 0.005, respectively). Our data suggested that in RA the measurement of sIL-2R may certainly mirror the degree of chronic inflammation and the continuous activation of the immune cells in the joint, although the role of this molecule in the immune response is still unclear.

The effect of azathioprine on serum levels of interleukin 6 and soluble interleukin 2 receptor

Cytokine pathways are central to the perpetuation of synovial inflammation in rheumatoid arthritis (RA). Azathioprine (AZA) has disease modifying activity in RA. This study addressed the effect of AZA on serum IL-6 and soluble IL-2 receptor (sIL-2R) levels in RA. Over a 24 week period of therapy significant clinical improvement was observed. However, serum levels of both IL-6 and soluble IL-2R levels did not significantly change after AZA therapy. AZA therapy did not significantly alter the peripheral blood monocytes ability to produce IL-6 in vitro, either in the presence or absence of LPS. The mechanism by which AZA achieves clinical improvement in RA patients does not appear to be through IL-6 modulation or modification of synovial lymphocyte activation as assessed by serum sIL-2R levels.