Disclosed is a method of expressing an antigenic molecule or a part thereof on the surface of a cell, comprising contacting said cell with said antigenic molecule, a photosensitising agent, and a Toll-like receptor (TLR) ligand, and irradiating the cell with light of a wavelength effective to activate the photosensitising agent, wherein said antigenic molecule is released into the cytosol of the cell and the antigenic molecule or a part thereof is subsequently presented on the cell&rsquo；s surface, wherein said method is performed in vitro, ex vivo or in a non-human animal in vivo. Also disclosed is the use of such cells in the manufacture of a medicament for stimulating an immune response in a subject.
