Specific spontaneous cytotoxic activity in human T cell colonies.

Cells in T cell colonies grown in vitro from normal human peripheral blood leukocytes can kill a variety of different target cells against which the blood donor has not knowingly been previously sensitized, i.e., the colony cells exhibit spontaneous cytotoxicity. Tumor target cells are preferentially killed. The ability to kill two different targets segregates independently in different colonies, which implies that the effector cells are specificity restricted. A majority (perhaps all) of the effector cells possess receptors for sheep erythrocytes and do not possess receptors for the Fc end of IgG, making it unlikely that they are either "natural killer" (NK) cells of cells mediating antibody-dependent cellular cytotoxicity. They may, however, be cytotoxic T lymphocytes.