The invention relates to polypeptides that have the same primary sequence as human IL-2, except that some amino acids have been mutated. The mutations introduced substantially reduce the capacity of these polypeptides for the in vitro and in vivo stimulation of regulatory T cells (T CD4+CD25+FoxP3+) and increase the efficacy of said polypeptides in the therapy of murine transplantable tumours. The invention also relates to the therapeutic uses of these variants, either alone or combined with vaccines, for the therapy of diseases, such as cancer or infections in which the activity of the regulatory T cells (Tregs) is relevant. The invention further relates to pharmaceutical compositions comprising the aforementioned polypeptides as an active principle. In addition, the invention relates to the therapeutic use of said polypeptides and pharmaceutical compositions, making use of their ability to modulate the immune system in relation to pathologies such as cancer and chronic infectious diseases.
