Novel TCR gene rearrangements and expression in radiation-induced thymic lymphomas

Using the intrathymic (i.t.) injection assay with a B10. Thy 1 congenic donor-host combination, we previously demonstrated that the pre-neoplastic cells (thymic prelymphoma cells) exist in immature T cell subpopulations; mainly in CD4-CD8- double negative (DN) and CD4-CD8+ single positive (SP) thymocytes and to some extent in CD4+CD8+ double positive (DP) thymocytes. Most thymic lymphomas that developed from these prelymphoma cells showed concomitant TCR α, β and γ gene rearrangements and expression. In these lymphomas, two lymphomas also showed TCR δ gene rearrangements. This represents the intermediate stages of TCR gene rearrangement. Every lymphoma, however, expressed CD3-associated α β TCR on the cell surface, but not γ δ TCR. Novel rearrangements of Vγ4 and Jγ4-Cγ4 segments with non-γ elements were found respectively in a concerted and symmetrical fashion. Recombinase-mediated inter-chromosomal exchanges characteristic of thymic lymphomas may function in radiation-induced lymphomagenesis. (author)