Detection of RAG-2 after culture with FL, supplemental cytokines, and SCM. CD34⁺Lin⁻DR⁻ cells were cultured in the presence of supplemental cytokines (IL-2, IL-3, IL-7, and KL) with or without SCM and FL. After 7 or 14 days, cells were harvested and mRNA amplified using RAG-2 primers. Five replicate samples for each culture condition are shown. Jurkat T-cell mRNA was used as a positive control (+C), and a template-free PCR reaction served as a negative control (−C). Shown is an autoradiograph after hybridization with a RAG-2 sequence-specific probe. The absence of genomic RAG-2 sequences was confirmed by amplification of mRNA without prior reverse transcription. Transcripts for β-actin were simultaneously amplified to confirm the presence of intact mRNA.