The present invention relates to a new binder molecule useful e.g. as an immune suppressor. In particular, it has been recognized that the UL11 protein of human the cytomegalovirus, binds to the CD45 molecule, potentially altering the immune system of an individual. In addition, the present invention relates to binder molecules, in particular, fusion molecules containing the CD45 binding domain of the UL11 protein in combination with a second molecule of interest for delivery of said molecule to cells expressing the CD45 molecule. Moreover, the present invention relates to pharmaceutical compositions comprising the UL11 protein of human cytomegalovirus, or derivatives or homologs thereof, or a nucleic acid sequence encoding the same.
