Vaccine- and immune-based therapy in chronic lymphocytic leukemia.

B-cell chronic lymphocytic leukemia (CLL) would appear to be an ideal target of T-cell-mediated responses against the cancer cell. The cancer arises in cells that can act as antigen-presenting cells (APCs), CLL cells express tumor antigens, and the cells can be a target of the allogeneic T cells in a graft-versus-leukemia effect. Despite these potential benefits, immune responses against CLL cells have been difficult to elicit. CLL induces immune defects in the host, the tumor cells are inefficient APCs, and therapies given to patients with CLL are themselves immunosuppressive. Successful vaccination approaches in this disease will require steps to overcome these difficulties, including steps to improve the immune defects in this disease, identification of the targets of the immune response to monitor immunologic responses, and improved presentation of antigen.