The overall objective of the proposed research is to gain greater understanding of the principles involved in the generation of allosensitized cytotoxic effector cells as they relate to tumor and allograft immunity. The main focus of the proposed studies will be: 1) To study allosensitization of CBA mice as a means to generate cytotoxic effector cells against AKR leukemia. 2) To investigate the nature of the antigenic target on AKR leukemia cells which enables effector cells from allosensitized, histocompatible donors to kill them. 3) To investigate the effector mechanism(s). 4) To transplant effector cells from allosensitized, histocompatible donors for adoptive immunotherapy of AKR mice bearing advanced spontaneous leukemia.