Herein is reported a method for producing a thymocyte supernatant comprising the steps of co-cultivating thymocytes and mononuclear cells at a cell ratio of at least 0.5:1.2 in the presence of phorbol-12-myristate-13-acetate and Phytohemagglutinin M for up to 60 hours, and separating the co-cultivation medium from the cells and thereby producing the thymocyte supernatant.