The Nonpolymorphic MHC Qa-1b Mediates CD8+ T Cell Surveillance of Antigen-processing Defects
Overview
General Medicine
Authors
Affiliations
The nonclassical major histocompatibility complex (MHC) Qa-1b accommodates monomorphic leader peptides and functions as a ligand for germ line receptors CD94/NKG2, which are expressed by natural killer cells and CD8+ T cells. We here describe that the conserved peptides are replaced by a novel peptide repertoire of surprising diversity as a result of impairments in the antigen-processing pathway. This novel peptide repertoire represents immunogenic neoantigens for CD8+ T cells, as we found that these Qa-1b-restricted T cells dominantly participated in the response to tumors with processing deficiencies. A surprisingly wide spectrum of target cells, irrespective of transformation status, MHC background, or type of processing deficiency, was recognized by this T cell subset, complying with the conserved nature of Qa-1b. Target cell recognition depended on T cell receptor and Qa-1b interaction, and immunization with identified peptide epitopes demonstrated in vivo priming of CD8+ T cells. Our data reveal that Qa-1b, and most likely its human homologue human leukocyte antigen-E, is important for the defense against processing-deficient cells by displacing the monomorphic leader peptides, which relieves the inhibition through CD94/NKG2A on lymphocytes, and by presenting a novel repertoire of immunogenic peptides, which recruits a subset of cytotoxic CD8+ T cells.
HLA-E: Immune Receptor Functional Mechanisms Revealed by Structural Studies.
Gillespie G, Quastel M, McMichael A Immunol Rev. 2025; 329(1):e13434.
PMID: 39753525 PMC: 11698700. DOI: 10.1111/imr.13434.
Ngiow S, Manne S, Huang Y, Azar T, Chen Z, Mathew D Cell. 2024; 187(16):4336-4354.e19.
PMID: 39121847 PMC: 11337978. DOI: 10.1016/j.cell.2024.07.018.
Unconventionally presenting an unconventional viral peptide.
Holly J, Yewdell J Nat Immunol. 2023; 24(11):1787-1789.
PMID: 37857826 DOI: 10.1038/s41590-023-01652-5.
Murine cytomegalovirus downregulates ERAAP and induces an unconventional T cell response to self.
Geiger K, Manoharan M, Coombs R, Arana K, Park C, Lee A Cell Rep. 2023; 42(4):112317.
PMID: 36995940 PMC: 10539480. DOI: 10.1016/j.celrep.2023.112317.
Different routes of MHC-I delivery to phagosomes and their consequences to CD8 T cell immunity.
Blander J Semin Immunol. 2023; 66:101713.
PMID: 36706521 PMC: 10023361. DOI: 10.1016/j.smim.2023.101713.