Expression of the T-cell-specific γ gene is unnecessary in T cells recognizing class II MHC determinants

Subtractive complementary DNA cloning combined with partial protein sequencing has allowed identification of the genes encoding the α and β subunits of T-cell receptors^1-7. The subtractive cDNA library prepared from the cytotoxic T lymphocyte (T_c) clone 2C has been found to contain a third type of clone encoding the γ chain^5,8,9. 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 T_c 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 T_c cells studied⁹. Here we present evidence that strongly suggests that T_H cells do not require γ gene expression.