Abstract: According to the invention there is described a method for ex vivo immunization of humans and animals comprising the following steps of: a) isolating autologous tumour cells; b) treating the tumour cells to prevent the survival thereof following reinfusion; c) incubating the thus treated tumour cells with intact heterologous bispecific and/or trisepcific antibodies showing the following properties: ?—binding to a T cell; ?—binding to at least one antigen on a tumour cell; ?—binding, by their Fc portion (in the case of bispecific antibodies), or by a third specificity (in the case of trispecific antibodies) to Fc receptor-positive cells.