Developmental regulation of T-cell receptor gene expression

In contrast to B cells or their antibody products, T lymphocytes have a dual specificity, for both the eliciting foreign antigen and for polymorphic determinants on cell surface glycoproteins encoded in the major histocompatibility complex (MHC restriction) 1–4 . The recent identification of T-cell receptor glycoproteins 5–7 as well as the genes encoding T-cell receptor subunits will help to elucidate whether MHC proteins and foreign antigens are recognized by two T-cell receptors or by a single receptor. An important feature of MHC restriction is that it appears to be largely acquired by a differentiating T-cell population under the influence of MHC antigens expressed in the thymus 8–10 , suggesting that precursor T cells are selected on the basis of their reactivity with MHC determinants expressed in the host thymus 9–11 . To understand this process of ‘thymus education’, knowledge of the developmental regulation of T-cell receptor gene expression is necessary. Here we report that whereas messenger RNAs encoding the β -and γ -subunits are relatively abundant in immature thymocytes, α mRNA levels are very low. Interestingly, whereas α mRNA levels increase during further development and β mRNA levels stay roughly constant, γ mRNA falls to very low levels in mature T cells, suggesting a role for the γ gene in T-cell differentiation.