Delta is the C_x-gene product in the γ/δ antigen receptor of dendritic epidermal cells

Most T cells bear an antigen receptor that is a protein of a disulphide-linked heterodimer composed of an a chain and a β chain associated with the non-polymorphic CD3 (T3) complex^1-7. A small subpopulation of thymic and peripheral T cells^8-17, as well as Thy-1 +dendritic epidermal cells (dEC) (refs 18-21), express an alternative CD3-associated dimeric receptor composed of the product of the T-cell antigen receptor (TCR) γ gene²² and a fourth chain, designated δ. Recently a new murine TCR constant-region gene, designated C_x, has been cloned and proposed as a candidate for the C_δ gene ²³. We have previously demonstrated that murine Thy-1⁺ dEC cell lines express a CD3-associated disulphide-linked heterodimer composed of a relative molecular mass M_r 41,000 (41K) γ chain and a 50K δ chain²¹. We have further analysed the receptor of one of these cloned dEC lines, 7-17.1, by endoglycosidase treatment of the isolated γ and δ chains. The γ chain was found to contain two N-linked oligosaccharide residues, consistent with the expression of a chain encoded by the V_γ3 and C_γ1 gene segments. The δ chain contains at least three N-linked oligosaccharides and has a core size of 38K. Northern blot analysis indicated the presence of abundant C_x messenger RNA in 7-17.1 cells. Immunoprecipitation with two antisera to peptides comprising distinct regions of the C_x sequence indicates that the δ chain is encoded by the C_x gene.