IN-FRAME TCR DELTA-GENE REARRANGEMENTS PLAY A CRITICAL ROLE IN THE ALPHA-BETA GAMMA-DELTA T-CELL LINEAGE DECISION/

Using a quantitative multiprobe Southern blot analysis, we demonstrate the surprising result that a significant proportion of alpha beta T c ells and thymocytes retain T cell receptor delta locus sequences. A su bstantial portion of the retained delta locus is in a fully V-to-D-to- J rearranged configuration and 20% of these delta rearrangements are f unctional, significantly less than the 33% predicted for random gene r earrangements. Our observations are in conflict with the idea that ap and gamma delta T cells derive from distinct precursors and suggest th at commitment of a common precursor to the gamma delta lineage depends upon expression of a ya T cell receptor. We propose that the intrathy mic T cell lineage decision is determined by a competition between the production of functional gamma delta and beta-pre-T cell receptor com plexes.