Genes encoding the Ti β subunit of the antigen/MHC receptor undergo rearrangement during intrathymic ontogeny prior to surface T3-Ti expression

To obtain further information about the ontogeny of the T-cell antigen/MHC receptor, a Ti β subunit cDNA probe and heteroantisera specific for the Ti α and Ti β subunits were utilized to characterize human T-lineage cells. Analysis of thymic tumors and normal thymocytes at both the DNA and protein levels demonstrates that Ti β gene rearrangement is evident in stage II (T11+T6+T3-) and stage III (T11+T6-T3+), but not stage I (T11+T6-T3-) thymocytes. In contrast, surface expression of Ti α and Ti β molecules is exclusively restricted to stage III thymocytes. Thus human T-lineage ontogeny is characterized by an orderly series of differentiation steps wherein Ti β gene rearrangement precedes surface expression of the T3-Ti molecular complex.