DIRECT-SEQUENCE ANALYSIS OF TCR V-DELTA-2-D-DELTA-3 REARRANGEMENTS INCOMMON ACUTE LYMPHOBLASTIC-LEUKEMIA AND APPLICATION TO DETECTION OF MINIMAL RESIDUAL DISEASE

T cell receptor delta chain (TCRdelta) gene rearrangements were studie d by Southern blot analysis in 36 patients with common acute lymphobla stic leukaemia, including 14 adults and 22 children. The majority of p atients (68%) had either a rearrangement or deletion of one or more TC Rdelta genes. The most frequent rearrangement involved a partial recom bination of Vdelta2 to Ddelta3 (55%). Ddelta2-Ddelta3 rearrangements w ere present in five patients (14%). To investigate the TCRdelta rearra ngement as a tumour marker in minimal residual disease studies, presen tation samples from 18 patients were amplified by PCR and directly seq uenced. Although the size of the Vdelta2-Ddelta3 junction varied by on ly 40 bp, sequence analysis showed extensive diversity. This was deriv ed from four factors: deletion of the 5' end of Ddelta3 gene (15/18) a nd 3' end of Vdelta2 gene (16/18); the presence of Ddelta2 sequences ( 6/18); insertion of N nucleotides (15/18); association of P nucleotide s with intact Vdelta2 and Ddelta3 genes (5/18). N nucleotides were the major feature, contributing to 75% of the junction. Ddelta1 sequences were not involved. Twenty base oligonucleotide probes, constructed fr om the junctional sequences, were capable of detecting residual tumour cells at the 10(-4) sensitivity level. Cross hybridization studies co nfirmed the probes to be clone specific. Longitudinal studies on patie nts undergoing treatment were capable of detecting tumour in remission samples.