High prevalence of T-cell receptor Vδ2-(D)-Dδ3 or Dδ1/2-Dδ3 rearrangements in B-precursor acute lymphoblastic leukemias

Abstract

Rearrangement of the immunoglobulin (Ig) and T-cell receptor (TcR) genes generally has been considered a useful marker of B- and T-cell lineage in lymphoproliferative disorders. However, concomitant rearrangements of Ig and TcR genes have been commonly reported in the most immature lymphoid malignancies, mainly in B-cell precursor acute lymphoblastic leukemia (ALL). To better characterize the nature of this lineage promiscuity, we have analyzed the configuration of the TcR δ locus in 75 B-precursor ALL. The large majority of cases (87%) displayed a rearrangement or deletion at the δ locus. Among the 57 nondeletional rearrangements, two patterns were predominant and both appeared to derive from partial joining: a Vδ-(D)-Dδ3 (32/57) and a Dδ1/2-Dδ3 (11/57) type. A single V δ gene (Vδ2) appeared to be involved in the first type of rearrangement. These findings are at variance with T-ALL, where rearrangements 5′ to Vδ2 are usually found. It remains to be elucidated whether this incomplete attempt of Vδ2 gene assembly is related to the neoplastic event or represents a physiologic predisposition occurring during early stages of the normal lymphocyte differentiation. © 1990 by The American Society of Hematology.