IL2 labelled with 123I (123I-IL2) and 99mTc (99mTc-IL2) has been used in vivo to detect activated lymphocytes in different autoimmune diseases, such as Coeliac disease [11], IDDM [12], Hashimoto’s thyroiditis, Takayasu’s arteritis [13], multiple-autoimmunity [14] and, recently, to detect immune infiltration on cancer [15]. This evidence concerns the gene IL2 and Hashimoto thyroiditis.