MTT cell proliferation assay on LGL cell lines. (A) LGL cell lines were incubated with or without IL-2 and measured for their proliferation. As shown, the F8 and SC LGL cell lines have become independent of IL-2 for proliferation, but have retained their capability to respond to IL-2 (*P < .05). In contrast, the f197 and m388 cell lines are highly dependent on exogenous IL-2 for their proliferation (**P < .01). (B) The IL-2–dependent LGL cell lines, f197 and m388, were incubated with the cytokines found to be expressed in the peripheral tumor from which they were derived (IL-1α and IL-1β, IFNγ, and GM-CSF ) and examined for their proliferative effects. Incubation with IL-2 and media alone served as positive and negative controls, respectively. As shown, none of these cytokines was able to support the proliferation of these IL-2–dependent LGL cell lines.