The diversity of T-cell receptor repertoire of peripheral CD4+ lymphocytes in LEC mutant rats

Abstract

A novel mutant strain of rats, LEC, exhibits an arrest of T-cell maturation from CD4+CD8+ to CD4+CD8- but not the CD4-CD8+ cells in the thymus. Nevertheless, CD4+T cells arise in lymph nodes of LEC rats, implying extrathymic T-cell maturation. We analyzed the variable (V) and junctional region diversity of T-cell receptor (TCR) beta- chains in this population, since several reports have provided evidence that extrathymically matured T cells exhibit a biased expression of the TCR repertoire. CD4+ T cells in LEC rat lymph nodes exhibited a polymorphic V beta gene expression pattern. However, biased V beta gene expression was not identified in peripheral CD4+ T cells of LEC rats when compared with V beta gene expression in their thymocytes. Furthermore, junctional regions of TCR beta chains exhibited a vast diversity created by non-germline- encoded nucleotide (N nucleotide) additions. These results indicate that peripheral CD4+ T cells in LEC rats possess a vast diversity in the TCR repertoire as do thymocytes of the same rat, suggesting that they derive from the thymus.