The capacity of the cultured cells to enhance allogenic MLR. Allogenic MLR was performed using purified T cells (3 × 10⁵ cells per well in 96-round-well plates) as responder cells. The unfractionated nonadherent cells, which were derived from Lin⁻c-kit⁺ HPC cultures in the presence of mouse TNFα combined with GM-CSF and SCF at days 7 and 14, respectively, as described in the Materials and Methods, were irradiated and used as stimulators at the indicated cell numbers (A). In (B), the indicated cell populations were used as stimulator cells that were separated by using a cell sorter from Lin⁻c-kit⁺ HPC cultures stimulated with mouse TNFα in combination with GM-CSF and SCF for 14 days. The proliferation of T cells was measured by MTT assay after 5 days of culture. Results are expressed as the mean ± 1 SD of triplicate cultures. Results of each panel are representative of three independent experiments.