Immunological Surveillance

NK cells and cytotoxic T lymphocytes (killer cells) both recognize and destroy cells with foreign antigens in their membranes. Cancer cells have surface antigens that are not present in normal cells and thus can be recognized as foreign. it is believed that cancer cells routinely develop in the body but are soon recognized and destroyed by the killer cells that recognize the abnormal antigens. This process of recogni­tion and destruction is termed immunological surveillance. Clinically evident cancers develop when this surveillance is inadequate.