Method of preparing a derivative of interleukin-lalfa.

METHOD OF PREPARING A INTERLUUCINMA-1alpha derivative (IL-1alpha), having a modified sequence of amino acids. The method involves incubating a CELULA transformant having an expression vector (such as a virus or organelle CELL SUITABLE) including a gene coding for derivative IL-1alpha TO PRODUCE THE DERIVATIVE AND RECOPGER derivative thus produced REMAIN said derivative of IL-1alpha a polypeptide having a sequence modified amino acid meets certain. Some of the products obtained have pharmaceutical applications.