No functional γ-chain transcripts detected in an alloreactive cytotoxic T-cell clone

Abstract

Three groups of genes that undergo rearrangements during T-cell maturation have been isolated from T cells^1–13. Two of them encode the α- and β-subunits of the T-cell antigen receptor and are shared between antigen-specific, major histocompatibility (MHC) class I-restricted cytotoxic T cells and antigen-specific, MHC class II-restricted helper T cells^1–10,14. The third group of genes, called γ, is preferentially transcribed in cytotoxic T cells^12,15. This led to the hypothesis that the unidentified γ-gene products could be part of a putative T-cell receptor responsible for MHC class I recognition^16,17. We report here on the isolation of three different types of γ-gene transcripts of an alloreactive cytotoxic T-cell clone (3F9). Two are derived from two rearrangements that have occurred at the same locus (V_γ 10.8A to J_γ 10.5 and transcribed with C_γ10.5), while the third involves a new V_γ-gene segment that is joined to J_γ13.4 and transcribed with C_γ13.4. All these rearrangements are abortive and lead to the formation of non-functional γ-chain genes because the proper translational reading frame is not maintained. Because the second copy of the C_γ13.4 gene segment is deleted and as C_γ7.5 is considered to be a pseudogene and has not undergone any rearrangements in 3F9, we conclude that the alloreactive cytotoxic T-cell clone 3F9 does not contain a functional transcript of a known γ-chain gene.