Impact of quantitative single-cell analysis on gene expression profiles. Monoclonal CD8 T cells, 4 d after in vivo antigen stimulation were sorted (A) at 20 cells/well for population studies, and (B) as 20 single cells at one cell/well. RT and PCR conditions were the same in both A,B. Results show: (A) Real-time PCR amplification of Gzmb (solid line), Tgf-β (dashed line), Inf-γ (dash-dotted line), Prf-1 (dotted line). (B) Quantification of gene expression in individual cells, using quantitative single-cell multiplex PCR. Expression levels of each gene in each cell are shown as shades of gray, compared to the log scale in the left. The absolute number of mRNA molecules was obtained by comparing amplifications with a standard of a known number of RNA molecules that followed the same rules of RT and amplification.
