Method validation of TCR CDR3 size distribution analysis. A cDNA sample of sorted CD4⁺ and CD8⁺ T cells from a healthy bone marrow donor was serially diluted to determine the number of cells at which a near normal distribution of TCR CDR3 sizes (8 to 10 bands) in the majority of the TCRBV families could be obtained after a TCRBV-specific spectratype PCR. Shown are the size distributions for undiluted cDNA and a 5-, 10-, and 20-fold dilution representing 30 × 10³, 6.0 × 10³, 3.0 × 10³, and 1.5 × 10³ cells in each spectratype for TCRBV1, TCRBV2, and TCRBV3 in CD4⁺ and CD8⁺ T-cell subsets.