Expression of the T-cell-specific gamma 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 alpha and beta subunits of T-cell receptors. 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 gamma chain. The gamma gene shares several features with the alpha and beta genes: (1) assembly from gene segments resembling immunoglobulin V, J and C (respectively variable, joining and constant region) DNA segments; (2) rearrangement and expression in T cells and not in B cells; (3) sequences reminiscent of transmembrane and intracytoplasmic regions of integral membrane proteins; (4) a cysteine residue at the position expected for an interchain disulphide bond. The alpha and beta genes are expressed at equivalent levels in both Tc cells and helper T cells (TH). The gamma gene, obtained from 2C, has been found to be expressed in all Tc cells studied. Here we present evidence that strongly suggests that TH cells do not require gamma gene expression.