To investigate rat T cell receptor, we adapted the 5\u27RACE (rapid amplificaton of cDNA ends) method, which has been proven as effective in analysis of TCRα chain. Here, a new TCR α chain gene was first identified in rat, and designated as rat V α14Jα281 (rVα14Jα281) gene because of its high sequence similarity to mouse Vα14Jα281 and human Vα24JαQ T cell receptor α chain gene. The similarity of rVα14Jα281 with mVα14Jα281 and with Vα24JαQ is 88.3%, and 76.0%, respectively. The rVα14 gene rearrangement with rJα281 has a non-diversity N-region at the VJ junction, named as rat invariant Vα14Jα281 (invariant rVα14Jα281). Our investigation also shown that invariant rVα14Jα281 was frequently expressed in total Vα14+ TCR at extrathymic sites in 36.1% and 94.6% of splenocytes and hepatic lymphocytes, respectively, although the frequency of invariant rVα14Jα281 is 5.4% in the thymus. Subsequently we investigated the expression of invariant rVα14Jα281 TCR in nude rat which lacked thymus. The data suggest that a unique lineage of invariant rVα14Jα281 TCR+ T cells matured through a selection process different from conventional αβ T cells and have an essential regulatory function for immunological responses
