ARTHRITIS & RHEUMATISM Volume 37 Number 6, June 1994, pp 898-901 0 1994, American College of Rheumatology 898 SERUM LEVELS OF SOLUBLE INTERLEUKIN-2 RECEPTOR A Marker of Disease Activity in Localized Scleroderma YOSEF UZIEL, BERNICE R. KRAFCHIK, BRIAN FELDMAN, EARL D. SILVERMAN, LAURENCE A. RUBIN, and RONALD M. LAXER Objective. To determine whether circulating serum levels of soluble interleukin-2 receptor (sIL-2R) are elevated in patients with localized scleroderma, and if levels of sIL-2R can differentiate between active and inactive disease. Methods. Seventeen patients with localized scleroderma were categorized by overall physician assessment into active, inactive, and indeterminate groups, according to disease activity. Serum sJL2R levels were analyzed and correlated with disease activity. Results. The mean sIL-2R level was significantly higher (P = 0.005) in those with active disease (1,675 f 823 unitshl) than in those with inactive disease (722 A 218 unitshl). Conclusion. Serum sIL-2R levels are elevated in patients with localized scleroderma. When present, elevated sIL-2R levels appear to be able to differentiate active from inactive disease. This fact also suggests cell-mediated immune activation in this condition. Further serial studies are required to assess the value and sensitivity of sIL-2R levels in measuring changes in disease activity. Localized scleroderma is a rare autoimmune disease that occurs primarily in children, and differs from systemic sclerosis (SSc) by being usually limited to the skin and subcutaneous tissues (1). Nevertheless, localized scleroderma can cause lifelong functional disability. There is neither a sensitive nor a specific laboratory test for measuring disease activity; monitoring is therefore done almost exclusively by clinical assessment. However, the slowly evolving nature of the lesion makes assessment of disease progression or regression difficult. These difficulties result in problems in determining the need for, and the efficacy of, drug therapy in patients with localized scleroderma. Levels of soluble interleukin-2 receptors (sIL2R) have been assayed in a variety of malignant, inflammatory, and infectious states (2), and appear to accurately reflect cell-mediated immune activity. Higher levels of sIL-2R have been found in patients with early generalized SSc and were correlated with disease outcome (3,4). We undertook this study to determine whether the measurement of sIL-2R levels can be used to reflect disease activity in patients with localized scleroderma. Yosef Uziel, MD, MSc: The Hospital for Sick Children, Toronto, Ontario, Canada; Bernice R. Krafchik, MB, ChB, FRCP(C): The Hospital for Sick Children; Brian Feldman, MD, FRCP(C): The Hospital for Sick Children; Earl D. Silverman, MD, FRCP(C): The Hospital for Sick Children; Laurence A. Rubin, MD, FRCP(C), FACP: Women’s College Hospital, University of Toronto, Toronto, Ontario, Canada; Ronald M. Laxer, MD, FRCP(C): The Hospital for Sick Children. Dr. Uziel is the recipient of an Abraham Shore Memorial Medical Fellowship and an American Physicians Fellowship. Drs. Silverman, Laxer are Associates of the Arthritis Society. Address reprint requests to Ronald M. Laxer, MD, FRCP(C), Division of Rheumatology, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, MSG 1x8,Canada. Submitted for publication August 10, 1993; accepted in revised form December 28, 1993. PATIENTS AND METHODS Patients. Serum samples were collected from 17 patients who were evaluated at the Localized Scleroderma Clinic at The Hospital for Sick Children. Localized scleroderma was diagnosed clinically by an experienced dermatologist (BRK) and rheumatologist (RML); no patient had internal organ involvement or systemic manifestations. A retrospective chart review was performed by an independent assessor (YU) who was unaware of the patients’ sIL-2R levels. Patients were divided into 3 groups according to their disease activity status. These groups were defined as follows: group 1, active phase, were those with new lesions, an increased size of previous lesions, or erythema or violaceous 899 SERUM s I L - ~ RAND LOCALIZED SCLERODERMA I-i n A A ACTIVE INACTIVE I INDETERMINATE Figure 1. Levels of soluble interleukin-2receptor (S-IL-2 R) in the 3 subgroups of patients with linear scleroderma. Shaded area shows the mean + 2 SD in 23 samples from healthy age-matched children. Bars show the mean 1 SD in individual patient groups. * color of the lesion; group 2, inactive phase, were those who had no new lesion and no change in size of previous lesions, but had softening and brownish discoloration of the skin; group 3, indeterminate, were those in whom it was unclear and difficult to determine clinically whether there was active skin inflammation or changes from the previous evaluation. Assays for sIL-2R. Serum samples were taken at the time of clinical assessments and stored at -70°C. Levels of sIL-2R were measured by enzyme-linked immunosorbent assay (ELISA) as previously described (5). The monoclonal antibodies used in the ELISA, anti-Tac (6) and 7G7/B6 (7), have been characterized and shown to bind distinct epitopes on the IL-2R molecule. Control samples were obtained from age-matched healthy children. Statistical analysis. An overall comparison of group means was made using one-way analysis of variance (ANOVA). Analysis of covariance was used to determine if age, erythrocyte sedimentation rate (ESR), or disease duration confounded the relationship between sIL-2R level and disease activity. Subsequently, the mean levels of sIL-2R in the active, indeterminate, and inactive disease groups were compared using pairwise t-tests, corrected by Fisher’s least squares difference for multiple significance testing. To determine the sIL-2R test characteristics, we calculated the sensitivity and specificity for various levels of sIL-2R. Statistical calculations were carried out on a Macintosh computer using Systat 5.2 (Systat, Inc., Evanston, IL). RESULTS Seventeen patients, 10 females and 7 males, were studied. The mean age at disease onset was 8.1 years, with a range of 1-14 years. The mean disease duration was 4.5 years. The mean f SD sIL-2R level for the 5 patients with active localized scleroderma was 1,675 5 823 units/ml (range 5742,399), that for the 8 patients with inactive disease was 722 2 218 units/rnl (range 384l,lOl), and that for the indeterminate group was 1,310 f 365 unitdm1 (range 1,06&1,838) (Figure 1). There were significant differences between the groups by ANOVA (P = 0.013), with a significantly increased mean level in the active group compared with the inactive group (P = 0.005). While there was a weakly negative correlation between patient age and sIL-2R levels (r = -0.325, P not significant), this did not alter the relationship between sIL-2R and disease activity. Furthermore, neither patient age, disease duration, ESR, nor eosinophilia changed the relationship between sIL-2R levels and disease activity. UZIEL ET AL 900 Table 1. Determination of best sIL-2R value for discriminating active from inactive localized scleroderma sIL-2R value (unitdml) Sensitivity ~ 500 600 700 800 1 ,OOo* 1,100 2,100 2,400 ~ 1 .O 0.8 0.8 0.8 0.8 0.6 0.4 0.0 Specificity ~ ~ ~ 0. I 0.4 0.6 0.8 0.9 0.9 1 .o 1.O * The best soluble interleukin-2 receptor (sIL-2R) value for discriminating active from inactive localized scleroderma is 1 ,OOO unitslml, with a sensitivity of 80% and a specificity of 90%. To determine the best cut-off level of sIL-2R that could be used to discriminate active from inactive disease, we calculated sensitivity and specificity at different sIL-2R values (Table 1). A cut-off level of 1,000 units/ml provided a sensitivity of 0.8 and specificity of 0.9 for the assessment of active disease. DISCUSSION To date, there are no sensitive or specific parameters for assessing disease activity in patients with localized scleroderma. ESR, peripheral eosinophilia, antinuclear antibodies (ANA), and serum immunoglobulin levels may be abnormal in the active phase of localized scleroderma but generally do not predict disease activity (1). The clinical changes of localized scleroderma evolve very slowly, and it is therefore difficult to accurately assess disease activity by either clinical evaluation or laboratory testing. This lack of precision makes the interpretation of any therapeutic intervention difficult. In the present study, we did not find any correlation between ESR, eosinophilia, ANA, or serum immunoglobulin levels and disease activity. We have previously shown that thermography demonstrated increased temperature in the active phase of localized scleroderma when new skin lesions appeared, but was difficult to interpret for slowly changing or inactive lesions (8). Highresolution B-mode ultrasound may eventually be helpful in defining disease activity but currently serves only as a research tool (9). At the present time, clinical evaluation seems to be the only practical way to monitor disease activity. The development of sensitive and specific laboratory or diagnostic imaging tests would be helpful in disease evaluation. In this study, we have shown that sIL-2R levels were significantly elevated in patients with active localized scleroderma as compared with patients with inactive disease. We have demonstrated that a cut-off level of 1,000 unitshl has both high sensitivity and high specificity for assessing the active phase of the disease. Previous studies have shown that serum levels of sIL-2R reflect disease activity in a variety of autoimmune disorders (2,lO). In rheumatoid arthritis, systemic lupus erythematosus, and polymyositis, high levels of sIL-2R have been more commonly found in the “active” disease states (10-13). In SSc, sIL-2R levels have been found to be markedly elevated in patients with early generalized disease, strongly associated with mortality, and inversely correlated with disease duration (3). In another study, Clements et a1 (4) reported higher sIL-2R levels in patients with early, untreated SSc. In our study, we did not find any correlation between disease duration and sIL-2R levels. Since our data include only single time-point measurements, we cannot yet draw conclusions about the relationship of changes in sIL-2R levels and changes in disease activity or long-term prognosis. Unlike SSc, there is no mortality associated with localized scleroderma, and the poor prognosis results from the local effect of a sclerodermatous band of tissue. This may be reflected by growth failure of an extremity, loss of range of motion where a lesion crosses a joint line, facial atrophy, seizure, uveitis, and severe cosmetic deformities. We are now collecting sera in a prospective manner to examine whether sIL-2R can not only serve to monitor disease activity, but also indicate subsequent clinical change and help predict outcome. A number of nonspecific laboratory abnormalities suggest an autoimmune basis for localized scleroderma. They include the presence of ANA and rheumatoid factor (1416), of anti-single-stranded DNA antibodies, which have been correlated with more extensive, active, and prolonged skin disease (16,17), of antibodies to histone, particularly in patients with more extensive skin involvement (17), and of increased levels of serum immunoglobulins. Rarely, anticentromere antibodies, which are generally associated with the CREST variant of SSc (calcinosis, Raynaud’s phenomenon, esophageal dysmotility, sclerodactyly , telangiectasias), have been reported in localized scleroderma (18). While a number of humoral immune abnormalities have been reported in patients with localized scleroderma, no previous investigations of cellmediated immune disturbances have been reported. SERUM s I L - ~ RAND LOCALIZED SCLERODERMA Our study is the first to document cell-mediated immune activation in localized scleroderma, as reflected by elevated levels of serum sIL-2R. In SSc, an increase in the number of helper memory T cells (CD4+,CD26+ and CD4+,CD25+) and a decrease in the number of suppressor killer T cells (CD8-t ,CD29+) was found in early disease and correlated with disease activity, suggesting a role for T cell-mediated immunity in SSc (19,20). The findings of elevated sIL-2R levels as well as increased levels of interleukin-2 (IL-2), IL-4, and B cell growth factor activity in culture supernatants further support the importance of T cell hyperactivity in SSc (21). Even though localized scleroderma usually is limited to the skin and subcutaneous tissues, the clinical presentation may be indistinguishable from SSc, and the skin histology is identical. These findings strongly suggest that the local pathogenic mechanism may be similar in both conditions. While the etiology of localized scleroderma is unknown, we hypothesized that, similar to SSc, activation of the immune system by an as-yet-unidentified antigen(s) results in cytokine release and a cascade of events that eventually leads to fibroblast proliferation, excessive collagen production, loss of subcutaneous tissue, fibrosis, and secondary deformity (22). We suggest that the cell-mediated immune activation in localized scleroderma leads to overproduction of collagen in the active phase of the disease, with the appearance of new lesions or an increase in the size of old lesions. When the skin was sclerosed or softened in the inactive phase, low levels of sIL-2R were demonstrated, indicating a reduction in immune T cell activation. In summary, our findings support a role for cell-mediated immune activation in localized scleroderma. Measurement of serum sIL-2R levels is a rapid, easy, and reliable method for assessing immune activation in vivo and, as such, may help delineate disease status and monitor disease activity, particularly with respect to evaluating a response to medical therapy, in localized scleroderma. Prospective serial studies are required to extend these initial observations. REFERENCES 1. Falanga V: Localized scleroderma. Med Clin North Am 73: 1143-1 156, 1989 2. Rubin LA, Nelson DL: The soluble interleukin-2-receptor: biology, function, and clinical application. Ann Intern Med 113:619-627, 1990 90 1 3. 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