Non-productive human TCR beta chain genes represent V-D-J diversity beforeselection upon function: Insight into biased usage of TCRBD and TCRBJ genes and diversity of CDR3 region length

The aim of the study was to assess the influence of constraints of V-D-J re arrangement on the nonrandom junctional diversity of productive T-cell rece ptor beta-chain genes in peripheral T-cells. Mature peripheral T lymphocyte s are expected to display a biased repertoire of T cell receptors (TCRs), e nriched for those that can recognize peptides presented by the major histoc ompatability complex (MHC) molecules. Therefore, functional TCR rearrangeme nts of peripheral T-cells are unsuitable to reveal the bias of the TCR repe rtoire, introduced by V-D-J rearrangement. To overcome this problem, we hav e studied nonfunctional TCR genes representing a repertoire of rearranged T CR gene sequences without any known post-rearrangement: selection. Detailed molecular analysis of a database generated from more than 500 functional ( TCRBV20S1) and nonfunctional (TCRBV10S1P and TCRBV19S1P) T-cell receptor ge nes from peripheral blood T-cells permitted a comparative analysis of recom bination frequencies of each germline-encoded V, D, and J-segments, as well as exonucleolytic nibbling and addition of nucleotides in functional and n onfunctional transcripts. Our data demonstrate that V-D-J recombination gen erates a more diverse CDR3 length distribution than found among productive TCRBV genes, suggesting that selection constrains the CDR3 to an optimal ju nctional region length. Furthermore, the well established biased patterns o f D- and J-usage in the rearranged TCRBV genes in human peripheral blood ly mphocytes were also present in nonfunctional transcripts. Therefore, V-D-J diversity is biased mainly by constraints of the rearrangement process rath er than intrathymic T-cell selection and peripheral expansion of particular T-tell clones. (C) American Society for Histocompatibility and Immunogenet ics, 1999, Published by Elsevier Science Inc.