Lymphoid gene expression in fresh, double-sorted CD34⁺Lin⁻DR⁻ cells from human bone marrow. Total mRNA was extracted and subjected to PCR using sequence-specific primers for CD3γ, CD3δ, CD3ζ, CD3, RAG-1, RAG-2, Ikaros, CD10, and TdT. Shown are composite autoradiograph data after hybridization with sequence-specific probes. Sixteen separate replicate reactions were performed for each primer except Ikaros, where 10 replicates were performed. No amplified transcripts were present for CD3γ, CD3δ, CD3ζ, or RAG-2 (n = 16), whereas bands of the expected size were detected for CD3ε, RAG-1, Ikaros, CD10, and TdT. Mature T-cell–containing peripheral blood mononuclear cells or the Jurkat cell line was used as positive controls (+C) to confirm successful PCR reactions. For each primer set, a simultaneously run template-free PCR reaction was used to confirm the absence of carryover amplicons (not shown). Amplification of β-actin confirmed the presence of mRNA in all lanes.