The invention provides compositions and methods for treating or preventing a target disease in a mammal by induction of memory T cells. The methods comprise (1) administering a sensitizing composition comprising a non-target antigen to a patient; and (2) administering a therapeutic composition comprising a non-target antigen and a target antigen to the patient, wherein the target antigen is associated with the disease, and wherein the therapeutic composition is administered after the sensitizing compositions, at an interval sufficient for induction of memory T cells. The methods can alternatively comprise administering a target antigen along with an inhibitory agent such as an inhibitor of DC apoptosis, an inhibitor of Granzyme B, a Granzyme-B-inducible mediator of apoptosis, an inhibitor of perforin, or a perforin-inducible mediator of apoptosis.