[Analyses of T cell receptor and its clinical implications in T cell neoplasms]

We studied gene rearrangement and expression of immunoglobulin heavy (IgH) chain, T cell receptor (TCR) beta, gamma and delta chains in neoplastic T cells from patients with leukemia and lymphoma. Rearrangements of TCR beta and gamma chain genes were observed in most of T cell neoplasms. TCR delta chain gene rearrangements or deletions were detected in all 77 T cell neoplasms; 6 of 9 CD3- T cell neoplasms showed rearrangement, whereas biallelic deletion of TCR delta chain gene was the most common pattern in CD3+ T cell neoplasm (65 of 68 patients). One patient with CD3- T cell leukemia had TCR delta chain gene rearrangement with a germline configuration of TCR beta, gamma and IgH chain genes. TCR gamma and delta chain gene transcripts were detected in most of the CD3- T cell neoplasms, whereas mature TCR alpha and beta chain mRNA were demonstrated in the majority of the CD3+ T cell neoplasms. In 6 patients with CD7+ CD3- CD4- CD8- MPO- leukemia, only 2 patients had rearrangements and weak expressions of IgH, TCR gamma and delta chain genes. We also present two cases of double negative (CD3+ CD4- CD8-) leukemia; one is TCR gamma delta bearing LGL, the other is TCR alpha beta bearing ATL. These results suggest that most of T cell neoplasms preserve a pattern of genotypic and phenotypic expression reflecting their developmental pathways and differentiation levels of TCR bearing normal T cells.