Summary of the cytokine-dependent proliferative responses.

G418 resistant TF-1 clones dependent on the cytokine present at the time of infection (ie, GM-CSF, IL-3, or IL-5) were tested for their resistance in a proliferative assay (as described in “Materials and methods”). The rates of proliferation were compared in the absence (▭) or presence ( after 3 days; •• after 5 days) of G418 for each cytokine. Results are represented as the relative ratio of [³H]-thymidine incorporation (cpm) obtained without G418 to that with G418. The G418 resistance was evaluated after 3 or 5 days of culture by the amount of [³H]-thymidine uptake. After 72 hours with G418, TF-1 cells did not incorporate [³H]-thymidine. (A) Representative profiles of clones derived from cells infected in the presence of GM-CSF (GM-50, GM-C), or IL-3 (IL-3-4) or IL-5 (IL-5-16). GM-C represents a clone in which no specific cytokine modulations occurred. (B) Schematic representation of the results of [³H]-thymidine incorporation for the selected clones from cells infected in the presence of GM-CSF (upper panel), IL-3 (left lower panel), or IL-5 (right lower panel) infected cells. −: no proliferation, +/−: difference in proliferation when compared with and without G418, +: similar proliferation with and without G418.