Use of a variable alpha region to create a functional T-cell receptor delta chain.

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Abstract
Two categories of T-cell antigen-specific receptor have been described. Most mature T lymphocytes have, on their membrane, an antigen receptor consisting of .alpha. and .beta. subunits, while early T cells and thymocytes possess a heterodimeric receptor termed .gamma.-.delta.. The DS6 clone, isolated from the peripheral blood of a patient with immunodeficiency, is a CD3+, CD4-, CD8- human T-cell line that expresses the disulfide-linked form of the .gamma.-.delta. antigen receptor. The nucleotide sequence analysis of DS6 cDNA makes clear that its variable region is a member of an .alpha. variable-region gene family. We have cloned and sequenced the germ-line joining and variable regions used to create the DS6 .delta. mRNA. Comparison of these sequences does not show evidence of extensive somatic mutations. The major difference between the germ-line and the T-cell antigen receptor .delta.-cDNA sequence is an insertion of three consecutive nucleotides between the variable and joining segments and is evocative of somatic diversification rather than of the use of a germ-line-encoded diversity region.