LC15 is a clonal population. (A) Alignment of VDJ junctional regions of TRBV6-1 sequences amplified from LC15 by 5′-RACE, demonstrating that LC15 expresses a single, unique TCR β-chain. (B) A spectral karyotype of LC15 demonstrates 4 translocations; all autosomal breaks occurred at centromeres. These were clonal abnormalities.