Detection of soluble interleukin-2 receptor in idiopathic thrombocytopenic purpura.

We measured soluble interleukin-2 receptor (sIL-2 R) in serum samples from 57 patients with idiopathic thrombocytopenic purpura (ITP). The sIL-2 R level was significantly increased in the ITP patients (481.3 +/- 378.5 U/ml) compared with controls (176.2 +/- 66.9 U/ml) (p < 0.001), and was significantly higher in 8 patients positive for hepatitis C virus (HCV) antibody positive (1,140.7 +/- 194.3 U/ml) than in 49 HCV-antibody negative patients (378.9 +/- 278.6 U/ml) (p < 0.0001). There was also a significant difference between the HCV-antibody negative ITP patients and the controls (p < 0.01). Elevated sIL-2 R levels correlated with the CD 4/8 ratio (p < 0.05), but not with the platelet count or the level of platelet-associated IgG. The increase of sIL-2 R in ITP may be related to the immunological abnormalities underlying this disease.