Current invention is related to the molecular pharmacology branch particularly to a peptide belonging to the Interleukin-15 sequence (IL-15) which is able to inhibit IL-15 biological activity, analogues or mimetic of such peptides. In the current invention it is shown that the peptide inhibits both IL-15-induced T cells proliferation upon binding to the IL15 receptor a subunit (IL15R.alpha.) and TNF.alpha.-mediated apoptosis. Besides, this invention is related to the use of this peptide in the treatment of several pathologies where aberrant IL-15 or IL-15R.alpha. expression is associated to the disease progression.
