The Vβ repertoire of mouse gut homodimeric α CD8+ intraepithelial T cell receptor α/β+ lymphocytes reveals a major extrathymic pathway of T cell differentiation

Abstract

Gut intraepithelial lymphocytes (IEL) contain two independent T cell receptor α/β+ T cell populations, with different Vβ repertoires. In DBA/2 mice (Mlsa, IE+), the CD4+ and heterodimeric α/β CD8+ thymodependent T cell pool shows the same deletion of V/β6, 8.1, and 11+ cells as found in peripheral lymphoid organs. In contrast, such deletions are not observed in the pool of IEL bearing homodimeric α CD8+ chains, in which these Vβ families are frequently observed in high amounts. The size of this gut homodimeric α CD8+ IEL pool and its different Vβ repertoire selection demonstrate the existence of a major extrathymic pathway of T cell differentiation with a gut-restricted localization. The large amount of the thymo-independent, homodimeric α CD8+ IEL found in the small bowel may contribute to a first line of defense against exogenous superantigens.