Escape mechanisms in tumor immunity: an update.

Evidence that tumors are immunogenic continues to accumulate. Although they frequently do express antigens in a form recognizable by the host immune system, tumors commonly "escape" the immune response. Tumors may therefore progress by evolving variants that can evade immune responses or by developing other strategies to avoid immune control. The purpose of this review is to consider the current status of knowledge concerning these different tumor-escape strategies, in the form of an update of previous publications in this journal.