Molecular genetic analysis of rat TCR chain - Identification of an invariant T cell receptor by 5′RACE

To investigate rat T cell receptor, we adapted the 5′RACE (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 Vα14Jα281 (rV α14Jα281) gene because of its high sequence similarity to mouse V α14Jα281 and human V α24JαQ T cell receptor α chain gene. The similarity of rV α14Jα281 with mV α14Jα281 and with V α24JαQ is 88.3%, and 76.0%, respectively. The rV α14 gene rearrangement with rJ α281 has a non-diversity N-region at the VJ junction, named as rat invariant V α14Jα281 (invariant rV α14Jα281). Our investigation also shown that invariant rV α14Jα281 was frequently expressed in total V α14⁺ TCR at extrathymic sites in 36.1% and 94.6% of splenocytes and hepatic lymphocytes, respectively, although the frequency of invariant rV α14Jα281 is 5.4% in the thymus. Subsequently we investigated the expression of invariant rV α14Jα281 TCR in nude rat which lacked thymus. The data suggest that a unique lineage of invariant rV α14Jα281 TCR⁺ T cells matured through a selection process different from conventional αβ T cells and have an essential regulatory function for immunological responses.