Abstract: The invention relates to an expression system containing one or more nucleic acid(s) comprising at least one nucleic acid for an interleukin 15/Fc (IL-15/Fc) fusion protein, at least one promotor, at least one nucleic acid for a CD5 leader and, where appropriate, at least one nucleic acid for a selectable marker gene; to a nucleic acid comprising the components of the said expression system and to a host cell containing the expression system or the nucleic acid. Furthermore, the invention relates to a process for preparing an IL-15/Fc fusion protein, using the expression system, and to the use of the expression system, the nucleic acid, the host cell or the CD5 leader for expression in host cells.

Abstract: The invention relates to fusion proteins consisting of a wild-type IL-15 and a IgG-Fc fragment, apart from a mouse IgG2b fragment, nucleic acids encoding said proteins, vectors, modified cells, and also to the use thereof for preparing drugs which are used, for example for preventing and/or curing disorders resulting from a transplantation and/or autoimmune diseases.