Immune Responses to Tumours: Parallels with Immunity to Intracellular Infection

Malignant transformation results in major changes in cellular growth control and interaction with surrounding cells. In many experimental systems, transformed cells are recognized specifically by the immune system; but in human cancer, evidence for such recognition remains equivocal. Rejection of experimental tumours depends primarily on cellular immune responses, although the relative importance of cytotoxic T cells, helper/inducer T cells, and less specific effector cells such as macrophages and NK cells varies between tumour systems. A variety of mechanisms by which tumours may escape immunological control have also been defined, including antigen loss, suppression and the development of factors which interfere with cellular immunity. Antibodies may be useful as an agent of immunological attack against tumours, either functioning with effector cells or complement, or as the vehicle to carry drugs or toxins to the tumour.