Developmentally regulated rearrangement and expression of genes encoding the T cell receptor-T3 complex

Human leukemic cells corresponding to the earliest identifiable stages of intrathymic T cell differentiation lack cell surface expression of the T cell receptor(TCRα/β)-T3 complex but transcribe TCRβ mRNA from either germ-line configuration ( 1 13 ) or partially (DJ) or fully (VDJ) rearranged ( 12 13 ) genes. These cells do not produce TCRα mRNA, but do contain T3δ and T3ϵ mRNA and accumulate T3 polypeptides, primarily in the perinuclear envelope. Equivalent normal T cells isolated from thymus have a predominantly germ-line configuration of TCRβ but contain intracellular T3 proteins. T3 gene expression is therefore a very early event in T cell differentiation. TCRα chain production appears to be the limiting maturation-linked event in the transport, assembly, and cell surface membrane insertion of the TCRα β -T3 complex.