Abstract

Cytotoxic lymphocytes play a central role in immune inflammatory responses against tumour cells, viruses and cells transplanted or infected with intracellular bacteria. The pivotal importance of lymphocytes in each of these immune responses has justified our continued interest in their cytotoxic function. Recent studies of cytotoxic lymphocytes have involved the characterisation of recognition structures on cytotoxic lymphocytes and the definition of two mechanisms of cytotoxicity. In contrast to normal cell death, which occurs during embryonic development and the formation and death of hematopoietic cell lineages, lymphocyte‐mediated cytotoxicity occurs in the context of an inflammatory response and the dying cells are lysed into the surroundings rather than phagocytosed. The roles of the two different forms of lymphocyte‐mediated cytotoxicity are quite distinct; however they both involve induction of an endogenous pathway of apoptosis in the targeted cell, and they do share features with all other forms of physiological cell death.