Abstract
The role of immunity in cancer has been abundantly demonstrated in murine tumor models as well as in man. Induction of clinically effective antitumor immune responses, based on this information, in patients with cancer however, remains elusive. This is not because tumors lack recognizable antigens [in fact there is evidence that there are thousands of potential novel targets in each tumor cell] but rather due to the fact that the induction of responses is not adequate nor particularly well understood. Tumors seem to be rather effective at limiting immune responses. Many of the molecularly defined antigens that have been detected on tumor cells are derived from self-proteins and as such are subject to tolerizing mechanisms. Such tumors have also developed escape mechanisms capable of evading or suppressing immune responses. Understanding the role of dendritic cells during the effector phase of the immune response and the complex interactions of stromal, immune, and tumor cells in the tumor microenvironment represent the next challenges to be understood for tumor immunology.