Escape of tumours from immunological destruction

This paper reviews the mechanisms of tumour escape from immune destruction that have been delineated in the past 2 decades. Current evidence indicates that the principal escape mechanisms are (i) weak or absent immunogenicity (ii) immunosuppression by tumour antigens or antigen-antibody complexes (iii) induction of suppressor cells and (iv) production of immunosuppressive factors. A classification of tumour escape mechanisms is presented.