To defend against disease, the immune system must be able to recognize a wide variety of foreign antigens with a specificity fine enough to distinguish these foreign antigens from self molecules. For T cells, the T-cell receptor (TcR), a heterodimer composed of an α and a β chain is responsible for the recognition of antigen. Each of the TcR chains is composed of two domains: a constant domain, which is membrane-proximal, and a membrane-distal variable domain, which is responsible for antigen—MHC recognition. The variable domain is encoded by up to three different types of gene segments, which are noncontiguous in the germline; variable (V), joining (J), and at least in the β chain, diversity (D) segments. During T-cell maturation, one of each type is randomly selected and brought together by somatic recombination to form a mature T-cell receptor gene. Thus, the diversity of the T-cell receptor depends on two factors: the number of different gene segments in the germline and the combinatorial diversity generated during the rearrangement process. The murine TcR Vβ gene family consists of ~16 Vβ subfamilies encoding a total of 20 Vβ gene segments (Barth et al., 1985; Behlke et al., 1985). During T-cell ontogeny, these V gene segments undergo somatic DNA rearrangements to Dβ—Jβ or -Jα gene segments, resulting in a complete V-(D)-J assembly in a fashion similar to the rearrangement process undergone by immunoglobulin genes (Kronenberg et al., 1986).
KeywordsGene Segment Variable Region Gene Gene Transfer Experiment Versus Gene Segment Leader Segment
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