The present invention provides a method of expressing an antigenic molecule or a part thereof on the surface of a cell using a photochemical internalisation method in which a cytokine, preferably GM-CSF, is used to enhance the method. The method may be used to stimulate an immune response and for various therapeutic or prophylactic methods. Pharmaceutical compositions or kits comprising the components for use in the method, cells produced by the method and their use in therapy and prophylaxis also form aspects of the invention.
