Synergistic effects of LIF with other cytokines on the proliferative capacity of freshly purified human fetal BM CD34⁺ thy-1⁺ cells. See Fig 2 legend for additional information. (□), LIF; (◊), LIF + IL-3 + IL-6; (○), LIF + IL-3 + IL-6 + GM-CSF; (▵), LIF + IL-3 + IL-6 + GM-CSF + SCF.