THE DIVERSITY OF T-CELL RECEPTOR REPERTOIRE OF PERIPHERAL CD4(+) LYMPHOCYTES IN LEC MUTANT RATS

A novel mutant strain of rats, LEG, exhibits an arrest of T-cell matur ation from CD4(+)CD8(+) to CD4(+)CD8(-) but not to 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 variabl e (V) and junctional region diversity of T-cell receptor (TCR) beta-ch ains in this population, since several reports have provided evidence that extrathymically matured T cells exhibit a biased expression of th e TCR repertoire. CD4(+) T cells in LEC rat lymph nodes exhibited a po lymorphic 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. Furthe rmore, junctional regions of TCR beta chains exhibited a vast diversit y created by non-germline-encoded nucleotide (N nucleotide) additions. These results indicate that peripheral CD4(+) T cells in LEC rats pos sess a vast diversity in the TCR repertoire as do thymocytes of the sa me rat, suggesting that they derive from the thymus.