Comparison of T Cell Receptor a , , B , and y Gene Rearrangement and Expression in T Cell Acute Lymphoblastic Leukemia

We have analyzed the configuration of the T cell receptor (TCR) a gene using newly developed genomic joining region (Ja) probes, which cover 80 kb of the Ja region upstream from the constant region in 19 patients with T cell acute lymphoblastic leukemia (T-ALL) and in three CD3leukemic T cell lines (HSB2, CEM, and MOLT4). In parallel, trnscription of the TCR-a, ,B, and y genes was examined in 11 of these patients and in the T cell lines. All T-ALL and the three T cell lines exhibited both TCR-'y and , gene rearrangements. 8 of 10 T-ALL and all T cell lines expressed TCR--y transcripts. All samples tested expressed both TCR-jt and CD3-'y transcripts. TCR a transcripts were only observed in CD3+ T-ALL but not in CD3T-ALL or the CD3cell lines. Among the CD3+ T-ALL, eight had TCR-a gene rearrangements. In addition, TCR-a gene rearrangements were detected in one CD3T-ALL and all three T cell lines. These leukemic cells may represent a transient stage between rearrangement and expression and provide an opportunity for analyzing the mechanism regulating the expression of the TCR-a gene.