Clinical Information

The interleukin-2 (IL-2) receptor (CD25) is a membrane protein that is upregulated on activated T cells. Its soluble form, IL-2 receptor alpha soluble (sIL-2r alpha, soluble CD25) is notably elevated in lymphoproliferative disorders, such as hemophagocytic lymphohistiocytosis (HLH), autoimmune lymphoproliferative syndrome (ALPS), T-cell related leukemia-lymphoma and other conditions associated with T-cell activation.(1) Based on the HLH-2004 trial, the diagnosis of HLH syndrome should be based on compatible clinical presentation in the context of significantly elevated inflammatory markers, including ferritin, sIL-2r alpha, and CXCL9 (C-X-C motif chemokine ligand 9). sIL-2r alpha elevation at a significant level (2SD above age-adjusted laboratory-specific reference range) is a crucial diagnostic criterion.(2)

In addition to activated T cells, IL-2 receptor is also expressed on a certain subset of B cells, Regulatory Teg cells, granulocytes and natural killer (NK) cells.(3) Elevation of sIL-2r alpha can be observed in other chronic inflammatory conditions and malignancies.(4,5) In sarcoidosis patients with cardiac involvement, higher levels of sIL-2r alpha are associated with worse long-term clinical outcomes and increase systemic inflammatory activities.(6) In patients with hematological malignancies that express IL-2 receptors, sIL-2r alpha elevations are associated with poor prognosis or disease relapse.(4,7)