USE OF TCR ADV GENE SEGMENTS BY THE DELTA-CHAIN IS INDEPENDENT OF THEIR POSITION AND OF CD3 EXPRESSION

The CD3 signaling complex is required for cell surface expression and selection of both alpha beta and gamma delta TCR. In this study we ana lyzed TCRD transcripts in both wild-type and CD3-epsilon-deficient mic e. We show that the repertoire of ADV segments used by the delta chain is unchanged in the latter. Not all ADV genes participate in making u p the TCRD repertoire. However, their use does not depend on their dis tance from the other TCRD-forming segments. For example ADV12, situate d at more than 870 kb from the DD region, is expressed as part of TCRD transcripts, whereas ADV8, members of which are proximal to the DD re gion, is not. These data suggest that the accessibility of ADV8 gene s egments is differentially regulated during T cell development in the t hymus. Taken together, our results suggest that TCRA and TCRD rearrang ements are independently controlled, and that the absence of TCRA expr ession in CD3-epsilon-deficient, mice is not due to a lack of accessib ility of the ADV gene segments but rather to inaccessibility of the AJ gene region.