N. Kimura et al., HIGH PREVALENCE OF T-CELL RECEPTOR D-DELTA-2(D-DELTA)J-DELTA REARRANGEMENT IN CD7-POSITIVE EARLY T-CELL ACUTE LYMPHOBLASTIC-LEUKEMIA, Leukemia, 10(4), 1996, pp. 650-657
We have studied the molecular characterization of the T cell receptor
(TcR) genes in 16 patients with CD7(+) early T cell acute lymphoblasti
c leukemia (T-ALL), defined as being positive for CD7 but negative for
CD3/4/8, myeloperoxidase (MPO), and CD19/20. Using gene analysis, rea
rrangement was demonstrated in one patient for immunoglobulin heavy ch
ain (IgH) gene, five for TcR-beta gene, and four for TcR-gamma gene. F
ifteen patients (94%) had rearranged band(s) involving the joining reg
ion of the TcR-delta chain gene. In nine cases these were the only rea
rrangements, whereas in six cases TcR-beta and/or TcR-gamma gene rearr
angements were found as well. The D delta 2(D delta)J delta 1 rearrang
ement was demonstrated in 87.5% (14/16) of cases. D delta 2(D delta)J
delta 3 was recognized in one patient, D delta 2D delta 3 was found in
three, and V(D)DJ using only V delta 2 and V delta 3 was recognized i
n two patients. We found no V2D delta 3, V3D delta 3, or V1(D)DJ delta
rearrangement patterns. Five of nine cases with DDJ delta were positi
ve for cytoplasmic CD3 epsilon(CyCD3 epsilon). Our data suggest that D
DJ delta joining occurs at an early stage during T cell differentiatio
n, followed by rearrangements of V delta to the DDJ delta complex. Fur
thermore, our findings suggest that DDJ delta recombination occurs ear
lier than expression of CyCD3 epsilon protein products. DDJ delta rear
rangements have never been observed in non-T cell malignancies, such a
s precursor-B-ALL or acute myeloid leukemia. Therefore, detection of D
DJ delta rearrangement in the TcR-delta locus is a useful tool to esta
blish lineage and clonality of leukemic cells In the most immature sta
ges of T cell development.