A recombinant chimeric antagonist formed by a 60 amino acid fragment of the N-terminal region of human interleukin 2 (IL-2) fused to the N-terminal of the extracellular region of the alpha subunit of the gamma IFN (IFN γ) receptor. In vitro this protein has a T cell growth stimulating activity, it inhibits the growth stimulating activity of IL-2 in T cells, it inhibits the induction of HLA-DR by IFN γ and it inhibits the antiproliferative activity of γ IFN. This invention can be applied in the field of medicine for the treatment of several pathologies such as autoimmune diseases, graft rejections, chronic inflammations, sepsis, ischemia and reperfusion syndrome and atherosclerosis.