The present invention relates to an immunocytokine comprising (a) a conjugate and (b) an immunomodulatory antibody or a fragment thereof directly or indirectly linked by covalence to said conjugate wherein said conjugate comprises (i) a polypeptide comprising the amino acid sequence of the interleukin 15 or derivatives thereof and a polypeptide comprising the amino acid sequence of the sushi domain of the IL 15Ra or derivatives thereof and uses thereof.