Subtractive complementary DNA cloning combined with partial protein sequencing has allowed identification of the genes encoding the α and β subunits of T-cell receptors1-7. The subtractive cDNA library prepared from the cytotoxic T lymphocyte (Tc) clone 2C has been found to contain a third type of clone encoding the γ chain5,8,9. The γ gene shares several features with the α and β genes: (1) Assembly from gene segments resembling immunoglobulin V, J and C (respectively variable, joining and constant region) DNA segments10; (2) rearrangement and expression in T cells and not in B cells8; (3) sequences reminiscent of transmembrane and intracytoplasmic regions of integral membrane proteins8; (4) a cysteine residue at the position expected for an interchain disulphide bond. The α and β genes are expressed at equivalent levels in both Tc cells and helper T cells (T H)4,5,9,11. The γ gene, obtained from 2C, has been found to be expressed in all Tc cells studied9. Here we present evidence that strongly suggests that TH cells do not require γ gene expression.
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