The present invention generally embraces the treatment of diseases by targeting cells expressing an antigen on the cell surface. In particular the invention relates to a method for stimulating, priming and/or expanding in vivo T cells genetically modified to express a chimeric antigen receptor (CAR) targeted to an antigen, comprising contacting the T cells with the antigen or a variant thereof in vivo. In one embodiment, the antigen or variant thereof is provided by administering a nucleic acid encoding the antigen or variant thereof.
