May-Giemsa stain of BMMNCs from mice injected with WEHI-3B cells expressing exogenous cytokines. BALB/c mice were injected with irradiated WEHI-3B–lacZ, WEHI-3B–GM-CSF plus WEHI-3B–TNF, or WEHI-3B–GM-CSF plus WEHI-3B–IL-4 cells. Seven days later, each BMMNC was analyzed by May-Giemsa stain.