Observed TCRβ CDR3 sequence copy number per 5 mL whole blood. Frequency histograms of TCRβ CDR3 sequences observed in 4 different T-cell subsets distinguished by expression of CD4, CD8, and CD45RO and present in 5 mL blood of one male donor. For example, the square at 200,10 means that 10 unique sequences were each observed 200 times in the CD4⁺CD45RO⁺ (antigen-experienced) T-cell sample. The data were resampled from the sequences generated by the Genome Analyzer to approximate the expected CDR3 sequence distribution in the T cells present in 5 mL blood, as determined by flow cytometry. A small set of sequences found in the CD45RO⁺ compartments were found with very large copy number (> 10 000 copies) but are not displayed.