[Immunology and tumors. Effector cells].

Since Burnet expounded the theory of immune surveillance, various cells have been indicated as the "effectors" of the body immunological defence against tumours. Until recently, the ability to lyse tumour target cells was assigned to macrophages and the so-called thymus-dependent lymphocytes, known as killer T cells. The discovery of natural killer cells in mice recently has widened the number of effectors and the field of research in this sector. An examination is made of the features and main properties of these cell groups, and some questions are posed concerning their ability to cooperate in anti-neoplastic immunological defence.