I-123-Interleukin-2: biochemical characterization and in vivo use for imaging autoimmune diseases

We describe in detail the labelling of interleukin-2 with I-123 (I-123-IL2), its biochemical characterization, the in vitro binding assay and its use for the in vivo detection of tissues infiltrated with mononuclear cells. Human recombinant IL2 was labelled using an enzymatic method and its biochemical characterization was performed using high performance liquid chromatography (HPLC) analysis of cyanogen bromide-cleaved protein. In vitro biological and binding assays were performed on CTLL-2 cell line and on activated peripheral blood lymphocytes. In vivo studies were performed 1 h after administration of 2-3 mCi of I-123-IL2 in 10 newly diagnosed type 1 diabetes patients, five pre-diabetic patients, 10 Hashimoto's thyroiditis patients, 10 coeliac disease patients and 10 normal volunteers. I-123-IL2 scintigraphy allowed the in vivo detection and quantification of activated mononuclear cells in several affected tissues. In detail, I-123-IL2 accumulation was detected in the thyroid of all patients affected by Hashimoto's thyroiditis, in the bowel of all coeliac disease patients and in the pancreas of all pre-type 1 diabetic patients. By contrast, in newly diagnosed type 1 diabetics, I-123-IL2 scan was positive in five of the 10 studied patients. I-123-IL2 scintigraphy may be useful for studying autoimmune phenomena in vivo and in diagnostic protocols to evaluate the presence of other tissue involvement in patients with an organ-specific autoimmune disease. ((C) 2003 Lippincott Williams Wilkins).