Down-regulation of the orphan nuclear receptor ROR gamma t is essential for T lymphocyte maturation

Thymocyte development is a tightly regulated process. CD4(+)CD8(+) double-p ositive (DP) immature thymocytes exhibit distinct phenotypic features from mature T cells; they express only 10% of surface TCR that are found on matu re T tells and do not proliferate and produce IL-2 in response to stimulati on. In this report we show that transgenic expression of the orphan nuclear receptor ROR gamma t in mature T cells down-regulates their surface TCR ex pression. The ROR gamma t transgene inhibits IL-2 production by mature T ce lls, and this inhibition may be partially due to the inhibitory effect of R OR gamma t on c-Rel transcription, Furthermore, ectopic expression of ROR g amma t inhibits the proliferation of mature and immature T cells. These res ults, together with its predominant expression in DP thymocytes, suggest th at ROR gamma t controls these distinct phenotypic features of DP thymocytes . Our data suggest that down-regulation of ROR gamma t expression in thymoc ytes is essential for their maturation.