Both TCR alpha and TCR delta chain diversity are regulated during thymic ontogeny

TCR alpha and TCR delta chains are coded by a common genetic locus using a single set of V gene segments (ADV segments). This article addresses the qu estion of regulation of the use of the ADV segments by the TCR alpha and TC R delta chains. Using both qualitative and quantitative analyses we have st udied the use of 23 ADV gene families as part of TCR alpha and TCR delta tr anscripts. A number of previously undetected rearrangement and transcriptio n events are described, indicating that the intrathymic TCR delta repertoir e is much more diverse than previously supposed. Repertoire analysis at sev eral developmental time points allowed the description of regulated waves o f ADV gene use, not only for TCR delta chains, but also for TCR alpha chain s, during thymic ontogeny. Control of these waves appears to be linked dire ctly to the ADV segments and their local chromatin environment, which may c hange over the course of T cell differentiation.