disclosed are cells and methods for treating or preventing tumor formation or infections with pathogens in a patient . the cells of the invention are antigen - presenting cells that have been loaded with rna derived from tumors or pathogens . by administering the rna - loaded antigen - presenting cells to a patient , tumor formation or pathogen infections can be treated or prevented . alternatively , the rna - loaded cells can be used as stimulator cells in the ex vivo expansion of ctl . such ctl can then be used in a variation of conventional adoptive immunotherapy techniques .