Use of interleukin-2 in the management of haematological malignancies: focus on minimal residual disease.

Interleukin (IL)-2 is a glycoprotein lymphokine which induces proliferation of all subclasses of T-lymphocytes, natural killer cells and lymphokine activated killer cells, differentiation of cytotoxic cells and secretion of other cytokines, especially interferon-gamma. A fundamental property of IL-2 activated effector cells is to selectively lyse freshly isolated tumour cells. Work carried out on animal tumour models and application in human therapeutics has suggested the potential value of an immunotherapeutic approach in haematological malignancies, especially in the setting of minimal residual disease. Extensive phase I/II trials have been conducted in all haematological diseases, but the most interesting results have been obtained in acute myeloid leukaemia and non-Hodgkin's lymphoma, where the possibility of achieving partial and complete responses in patients with advanced disease has been reported. The feasibility and immunomodulatory effects of IL-2 treatment in patients with minimal residual disease after high-dose chemotherapy have also been explored. However, the heterogeneity of cases treated and administration schedules used does not allow definitive conclusions to be drawn about the true impact of IL-2 treatment on the prognosis of these patients. The clearly encouraging results reported in the literature deserve further investigation from a biological and clinical point of view; until the role of IL-2 in haematological malignancies has been identified, it should be used only in the investigative setting of clinical trials.