Death and the cell.

Cell death is an important component of many - perhaps all - immunological reactions. Target cells die after attack by complement, cytotoxic T lymphocytes, K cells, NK cells or lymphotoxins. In lymphoid cells themselves death occurs in parallel with proliferation in the normal thymus and in the periphery during immune responses. Cell death, therefore, is sometimes a pathological event and sometimes a physiological process, apparently as tightly regulated as cell proliferation. In this article Edward Duvall and Andrew Wyllie develop the theme that the internal organization and metabolism of nucleated cells determines their mode of death by one or other of two relatively stereotyped patterns, necrosis or apoptosis. They discuss the general mechanisms involved in each pattern, their relevance to immunology, and their biological significance.