Figure 1.

Schematic map of the human TCR α/δ locus. Filled rectangles represent V_α, V_δ, C_δ and C_α gene segments, as well as the T-early-α (TEA) exon. Vertical lines represent D_δ, J_δ and J_α gene segments. E_δ and E_α are represented by •, and the TCR α locus control region (LCR) (to date defined only in mouse) is represented as a filled oval. Transcriptional orientation is left to right for all gene segments except V_δ3 (rearrangement of V_δ3 occurs by inversion of D_δ, J_δ, and C_δ gene segments). ψJ_α is a nonfunctional J_α thought to serve as an acceptor for initial rearrangement events into the J_α region (17). Restriction enzymes are K, KpnI; Bg, BglII; R, EcoRI; Bm, BamHI; N, NsiI; C, ClaI.