Figure 1. Two Approaches to Immunotherapy.

The two main approaches to immunotherapy for cancer are vaccine therapy and cell-transfer therapy. Three steps are required for effective treatment: there must be sufficient numbers of lymphocytes with avid recognition of tumor antigens; these lymphocytes must reach the tumor; and once there, they must be able to destroy the tumor cells. Cancer vaccines depend on the in vivo generation of immune cells by an immunizing vector. Yu et al.¹ used an approach that increases the exposure of T lymphocytes to tumor tissue; they immunized mice with cells modified to secrete a molecule that enhances the flow of naive lymphocytes into tumor tissue and, hence, their sensitization to tumor antigen. Cell-transfer therapies involve sensitizing autologous lymphocytes ex vivo, expanding the population, and then infusing the lymphocytes into the host.