Elevated serum levels of soluble interleukin‐2 receptor, neopterin and β‐2‐microglobulin in idiopathic dilated cardiomyopathy: relation to disease severity and autoimmune pathogenesis

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Abstract
Background: It has not been assessed whether high levels of soluble interleukin 2 receptor (sIL‐2R), neopterin and β‐2 microglobulin in idiopathic dilated cardiomyopathy reflect heart failure severity and/or an active autoimmune process. The aim of this study was to relate serum levels of these markers to clinical and autoimmune features.Methods: We studied 60 patients with idiopathic dilated cardiomyopathy, 67 controls with ischemic heart failure and 34 normals.Results: Abnormal levels of sIL‐2R, but not of neopterin and β‐2 microglobulin, were more frequent in idiopathic dilated cardiomyopathy than in ischemic patients (35% vs. 16%; P ‐ 0.02) or in normals (35% vs. 12%, P ‐ 0.01); mean sIL‐2R levels were, however, similar in idiopathic dilated cardiomyopathy and ischemic heart failure (842 ± 75 vs. 762 ± 93 U/ml, P ‐ NS). In idiopathic dilated cardiomyopathy abnormal levels of sIL‐2R were associated with lower peak oxygen consumption (P ‐ 0.008), higher neopterin and HLA class II expression in the myocardium (P ‐ 0.02), but were unrelated to cardiac autoantibody status or titer. In addition, abnormal levels of neopterin were associated with adverse prognosis and higher β‐2 microglobulin; abnormal levels of β‐2 microglobulin with lower echocardiographic percent fractional shortening, higher sIL‐2R and higher neopterin.Conclusions: There is no convincing evidence that abnormal sIL‐2R, neopterin and/or β‐2 microglobulin are disease‐specific markers of idiopathic dilated cardiomyopathy. The lack of association with cardiac autoantibodies suggests that these abnormalities are mainly related to heart failure severity rather than autoimmune pathogenesis. In keeping with this view, high levels of sIL‐2R, neopterin and/or β‐2 microglobulin identified a subset of idiopathic dilated cardiomyopathy patients with advanced disease and poor prognosis.

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