Frontiers in Immunology (Oct 2023)

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

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

DOI
https://doi.org/10.3389/fimmu.2023.1250316
Journal volume & issue
Vol. 14

Abstract

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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-1b) 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 Qa1b or classical MHC I for positive selection. However, QFL thymocytes do require Qa1b 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.

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