Spontaneous cytotoxic T cells in murine spleen-cell cultures. II. Distinguishing between spontaneous cytotoxic T cells and NK cells according to kinetics and target selectivity.

Cytotoxic T cells that arise spontaneously in cultures (SCTL) appear to be distinct from natural killer (NK) cells. The specificity of these two types of cytotoxic cell populations has been compared by direct cytotoxicity and cold target inhibition tests. The SCTL population consists of an array of cytotoxic cells each of which is specific for a series of target cells. The NK cells had a more limited range of target selectivity although at least two types of NK effector cells were detected on the basis of specificity measurements.