Northern blot analysis of purified human lung MC. Human lung MC (purity, 91%) were cultured in RPMI 1640 medium with 10% FCS in the presence of rhSCF (100 ng/mL) or control medium (Co) for 2 hours. Thereafter, cells were harvested and the extracted mRNA hybridized with oligo-nucleotide probes specific for MCP-1, RANTES, MIP-1α, MIP-1β, IL-8, SCF or β-actin (as indicated). After each hybridization, blots were stripped. Unstimulated primary lung MC were found to express baseline levels of MCP-1 mRNA. However, incubation of MC with rhSCF resulted in a substantial increase in expression of MCP-1 mRNA (densitometry: control, 100%; rhSCF, 334%). Neither untreated nor SCF-treated MC expressed detectable amounts of transcripts specific for MIP-1α, MIP-1β, RANTES, or IL-8.