[en] IL-2 and the other cytokines labeled with ^99mTc are an interesting option to early diagnosis of autoimmune diseases and monitoring with nuclear medicine images. The aim of this study was to obtain by indirect method IL-2 labeled with ^99mTechnetium using Benzoyl MAG3 chelating agent, for in vivo diagnosis of lymphocytic infiltration. IL-2 is a small, relatively fragile protein, and it is essential to retain its receptor binding capacity after labeling. Two different methods of labeling have been proven: Pre-conjugation labeling method: we used NHS- Hynic as a chelator agent and labeled this conjugated protein with ^99mTc using tricine as coligand. Albumin was used as a model for the conjugation and labeling steps. The albumin was labeled by this method with a good labeling efficiency but the IL-2 protein could not be labeled with this approach. Post- conjugation labeling method: we used the bifunctional chelating agent, benzoyl MAG3, this ligand is first labeled with ^99mTc and then is conjugated to the protein. The N₃S Logan complex was incubated for 30 minutes and then measured by RP- HPLC. An active ester of the labeled Logan was formed and was incubated with Il-2 at room temperature and basic pH to promote the conjugation between the active ester and the protein. The labeling efficiency was determined by RP-HPLC using a C 18 column. The albumin protein was also labeled by this method and the radiochemical purity was measured by RP- HPLC using a GPC column and the labeling efficiency was 80%. The next objectives are to explore different strategies for purifying the ^99mTc-IL-2 and to evaluate the capacity of IL-2 to bind to its receptor after labeling. (author)