Tumour immunology.

Antigens which distinguish neoplastic cells from their normal counterparts can be identified in some, but by no means all, experimental tumours. Specifically immunized hosts can in appropriate circumstances reject small tumours immunologically. The mechanisms of rejection remain unknown. The extent to which most human neoplasms excite a rejection reaction is still not clear. While the behaviour of neoplasms appears to be influenced by the immune system, the concept of immunological surveillance against neoplasia is losing support. Clinical immunotherapy has not yet achieved notable success, and remains empirical.