Clonality of T cells produced by limiting dilution and in bulk culture. T-cell clonality was determined by flow cytometric T-cell receptor (TCR) Vβ spectratyping (top) and by PCR amplification of clonal V-J rearrangements at the TCRγ locus (bottom). Representative results for T cells produced by limiting dilution (A) and in bulk culture (B) are shown. (A) T cells produced by limiting dilution (patient B), showing clonal expression of Vβ17 in 98% of CD8⁺ T cells by Vβ spectratyping (top; ■) and showing 2 predominant TCRγ rearrangements (bottom). Because each T-cell clone can rearrange one or both of its TCRγ alleles, the 2 PCR products could represent either 1 T-cell clone with biallelic TCRγ rearrangements or 2 singly rearranged clones, although the single predominant Vβ17 clone identified by spectratyping would favor a single doubly rearranged clone. (B) T cells produced in bulk culture (patient G) showing oligoclonal Vβ expression in CD8⁺ T cells (16% Vβ16; 9% Vβ7.1; 3% each Vβ3, Vβ13.2 and Vβ17; 2% each Vβ1 and Vβ13.1; and 1% each Vβ5.1, Vβ13.6, Vβ21.3, and Vβ23) and 7 distinct TCRγ rearrangements by PCR (bottom; ■) that could correspond to between 4 and 7 different T-cell clones, depending on the number of singly and doubly rearranged clones (see Table S1). The □ in both top panels represent the average expression levels for each Vβ chain in normal polyclonal T-cell populations.