Cloned lines of SJL/J spleen cells with cytotoxic reactivity.

Cultures of spleen cells from normal SJL/J mice were initiated and maintained in the presence of lectin-free interleukin-2 (IL-2). After about 8 weeks in culture, the frequency of progenitors of proliferative cells became quite high (1/8-1/10) and it was possible to obtain many clones by the limiting dilution technique. Some of the clones had high levels of cytotoxic reactivity against tumor target cells, even at low effector:target ratios, indicating that natural effector cells from this low-NK-reactive strain have the capability of expressing potent lytic effects. There was considerable heterogeneity among the clones in their patterns of cytotoxic activity, morphology and expression of T-cell-associated antigens. Although the overall pattern of reactivity resembled that of NK cells, some clones reacted against an anchorage-dependent lung cancer cell line, M109, without detectable effects against the other target cells tested, including the highly NK-susceptible lymphoma cell line, YAC-1. The pattern of cytotoxic reactivity by the clones did not correlate with the morphological appearance of large granular lymphocytes (LGL), which has been highly associated with NK activity of fresh, uncultured lymphoid cells.