Characterization of murine lymphokine-activated killer cell cultures separated according to cell size

Incubation of murine splenocytes in high concentrations of the lymphokine interleukin 2 leads to the development of cytotoxic effector cells termed lymphokine-activated killer cells. Two populations of blast cells develop within these cultures, one of T origin and one of NK origin. The T blasts are CD8+, FcR gamma III- and exhibit slightly increased forward angle light scatter (FSC) and side angle light scatter (SSC). They have little or no oncolytic activity against the tumor target YAC-1. The NK blasts are CD8-, FcR gamma III+ and exhibit markedly increased FSC and SSC. They contain virtually all the lytic activity against the tumor target YAC-1. Cultures were split into multiple fractions on the basis of sedimentation velocity, which separates cells primarily on the basis of cell size. The sedimentation separation resolved both T and NK cells into resting (G0) small lymphocytes and cycling blast cells. NK blasts sedimented much more rapidly than all CD8+ cells such that most of the oncolytic activity could be separated relatively free of CD8+ cells.