DOMINANTLY INHERITED EXPRESSION OF BID, AN INVARIANT UNDIVERSIFIED T-CELL RECEPTOR DELTA-CHAIN

In BALB/c lung and lymph node γδ T cells, a large fraction of the expressed Vδ5 genes consist of an invariant sequence, BID (for BALB/c invariant delta). BID results from a direct joining of the Vδ5, Dδ2, and Jδ1 segments, which conserve their complete germline coding sequences. In C57BL/6 (H-2b) mice, where identical and functional segments are present in the germline, BID is absent. It appears that BID+ γδ T cells are positively selected by factors encoded outside of the classical MHC region, as indicated by their dominance in F1( C57BL 6 × BALB c) and in BALB.B (H-2b) mice. Additional observations, including the expression of BID in BALB c nu/nu but not in C57BL 6 nu/nu mice, suggest that the expansion of BID+ T cells essentially occurs extrathymically. © 1990.