AUTHOR=Manoharan Valerio Michael , Arana Kathya , Guan Jian , Chan Shiao Wei , Yang Xiaokun , Kurd Nadia , Lee Angus , Shastri Nilabh , Coscoy Laurent , Robey Ellen A. 

TITLE=The promiscuous development of an unconventional Qa1b-restricted T cell population

JOURNAL=Frontiers in Immunology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2023.1250316

DOI=10.3389/fimmu.2023.1250316

ISSN=1664-3224

ABSTRACT=<p>MHC-E restricted CD8 T cells show promise in vaccine settings, but their development and specificity remain poorly understood. Here we focus on a CD8 T cell population reactive to a self-peptide (FL9) bound to mouse MHC-E (Qa-1<sup>b</sup>) that is presented in response to loss of the MHC I processing enzyme ERAAP, termed QFL T cells. We find that mature QFL thymocytes are predominantly CD8αβ+CD4-, show signs of agonist selection, and give rise to both CD8αα and CD8αβ intraepithelial lymphocytes (IEL), as well as memory phenotype CD8αβ T cells. QFL T cells require the MHC I subunit β-2 microglobulin (β2m), but do not require Qa1<sup>b</sup> or classical MHC I for positive selection. However, QFL thymocytes do require Qa1<sup>b</sup> for agonist selection and full functionality. Our data highlight the relaxed requirements for positive selection of an MHC-E restricted T cell population and suggest a CD8αβ+CD4- pathway for development of CD8αα IELs.</p>