The present invention provides a method for enhancing the immunotherapeutic activity, e.g., cytotoxicity, of immune cells by depleting immune cells of a cell subset that down-regulates the immune response, such as either CD4.sup.+ or CD8.sup.+ lymphocytes. The remaining depleted immune cells are then cultured in the presence of interleukin-2 (IL-2) and an antibody to a lymphocyte surface receptor, preferably an anti-CD3 monoclonal antibody (MoAb). The present invention also provides a method of enhancing the immunotherapeutic activity, e.g., cytotoxicity, of immune cells by culturing immune cells in the presence of IL-2 and an antibody to a lymphocyte surface receptor, preferably an anti-CD3 MoAb; separating a cell subset capable of developing immunotherapeutic activity, e.g., cytotoxicity, from the cultured immune cells, e.g., either CD4.sup.+ or CD8.sup.+ lymphocytes; and then subculturing the separated lymphocytes in the presence of IL-2.