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The nonpolymorphic MHC Qa-1b mediates CD8+ T cell surveillance of antigen-processing defects.

Oliveira CC, van Veelen PA, Querido B, de Ru A, Sluijter M, Laban S, Drijfhout JW, van der Burg SH, Offringa R, van Hall T - J. Exp. Med. (2009)

Bottom Line: 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Clinical Oncology, Leiden University Medical Center, 2333 ZA Leiden, Netherlands.

ABSTRACT
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.

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The T cell receptor, but not NKG2A/C, mediates reactivity of the T cells. (A) Blocking antibody against Qa-1b demonstrated a direct role of this molecule for T cell recognition. Experiment was performed using EC7.1.Qa-1b target cells and repeated three times with similar outcome. (B) Blocking CD3 or CD8 with monoclonal antibodies decreased T cell reactivity against TAP-deficient EC7.1.Qa-1b target cells. Antibodies against NKG2A/C did not alter the T cell response, indicating that only the T cell receptor is critically involved in mediating reactivity. Data are representative of four experiments. (C) Exogenous peptide loading competes with endogenously presented epitopes on EC7.1.Qa-1b cells and inhibits the recognition of these target cells by Qa-1b–restricted CTL (left). Qdm (AMAPRTLLL) or Qdm L8K (AMAPRTLKL) peptides were loaded exogenously at the indicated concentrations on EC7.1.Qa-1b cells and IFN-γ release by CTL was measured. Control peptide was the Kb-binding 8-mer SIINFEKL from OVA. The Qdm L8K mutant peptide–Qa-1b complexes fail to interact with CD94/NKG2A or CD94/NKG2C (Kraft et al., 2000), indicating that the loaded peptides interfere with T cell receptor–mediated reactivity. Qdm-specific control CTL (right) was activated by the peptides. Means and standard deviations of triplicate wells are shown for one out of three comparable experiments.
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fig2: The T cell receptor, but not NKG2A/C, mediates reactivity of the T cells. (A) Blocking antibody against Qa-1b demonstrated a direct role of this molecule for T cell recognition. Experiment was performed using EC7.1.Qa-1b target cells and repeated three times with similar outcome. (B) Blocking CD3 or CD8 with monoclonal antibodies decreased T cell reactivity against TAP-deficient EC7.1.Qa-1b target cells. Antibodies against NKG2A/C did not alter the T cell response, indicating that only the T cell receptor is critically involved in mediating reactivity. Data are representative of four experiments. (C) Exogenous peptide loading competes with endogenously presented epitopes on EC7.1.Qa-1b cells and inhibits the recognition of these target cells by Qa-1b–restricted CTL (left). Qdm (AMAPRTLLL) or Qdm L8K (AMAPRTLKL) peptides were loaded exogenously at the indicated concentrations on EC7.1.Qa-1b cells and IFN-γ release by CTL was measured. Control peptide was the Kb-binding 8-mer SIINFEKL from OVA. The Qdm L8K mutant peptide–Qa-1b complexes fail to interact with CD94/NKG2A or CD94/NKG2C (Kraft et al., 2000), indicating that the loaded peptides interfere with T cell receptor–mediated reactivity. Qdm-specific control CTL (right) was activated by the peptides. Means and standard deviations of triplicate wells are shown for one out of three comparable experiments.

Mentions: To carefully determine the Qa-1b restriction of our isolated T cell clones, we examined their reactivity against two cell panels, based on the TAP-negative EC7.1 lymphoma and TAP-deficient B78H1 melanoma (Fig. 1; Howell et al., 2000; Chiang et al., 2003). Both cell lines are also devoid of MHC class I proteins and single class I molecules were reconstituted by gene transfer. All isolated T cell clones exhibited cytolytic activity (Fig. 1 A) and produced IFN-γ (Fig. 1 B and Fig. S2) against the Qa-1b–expressing cells, but not against cells in which only Db or Kb were introduced. These data convincingly demonstrated the Qa-1b restriction of our T cells and excluded cross-reactivity to the classical class I molecules. Qdm-specific control CTL did not recognize the TAP-deficient tumor targets, as the presentation of Qdm in Qa-1b is TAP dependent (Aldrich et al., 1994). Exogenous loading of Qdm conferred reactivity for this CTL clone (Fig. 1, right). A direct interaction with Qa-1b was revealed by the finding that anti–Qa-1b antibody strongly blocked the recognition by our CTL (Fig. 2 A).


The nonpolymorphic MHC Qa-1b mediates CD8+ T cell surveillance of antigen-processing defects.

Oliveira CC, van Veelen PA, Querido B, de Ru A, Sluijter M, Laban S, Drijfhout JW, van der Burg SH, Offringa R, van Hall T - J. Exp. Med. (2009)

The T cell receptor, but not NKG2A/C, mediates reactivity of the T cells. (A) Blocking antibody against Qa-1b demonstrated a direct role of this molecule for T cell recognition. Experiment was performed using EC7.1.Qa-1b target cells and repeated three times with similar outcome. (B) Blocking CD3 or CD8 with monoclonal antibodies decreased T cell reactivity against TAP-deficient EC7.1.Qa-1b target cells. Antibodies against NKG2A/C did not alter the T cell response, indicating that only the T cell receptor is critically involved in mediating reactivity. Data are representative of four experiments. (C) Exogenous peptide loading competes with endogenously presented epitopes on EC7.1.Qa-1b cells and inhibits the recognition of these target cells by Qa-1b–restricted CTL (left). Qdm (AMAPRTLLL) or Qdm L8K (AMAPRTLKL) peptides were loaded exogenously at the indicated concentrations on EC7.1.Qa-1b cells and IFN-γ release by CTL was measured. Control peptide was the Kb-binding 8-mer SIINFEKL from OVA. The Qdm L8K mutant peptide–Qa-1b complexes fail to interact with CD94/NKG2A or CD94/NKG2C (Kraft et al., 2000), indicating that the loaded peptides interfere with T cell receptor–mediated reactivity. Qdm-specific control CTL (right) was activated by the peptides. Means and standard deviations of triplicate wells are shown for one out of three comparable experiments.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2812552&req=5

fig2: The T cell receptor, but not NKG2A/C, mediates reactivity of the T cells. (A) Blocking antibody against Qa-1b demonstrated a direct role of this molecule for T cell recognition. Experiment was performed using EC7.1.Qa-1b target cells and repeated three times with similar outcome. (B) Blocking CD3 or CD8 with monoclonal antibodies decreased T cell reactivity against TAP-deficient EC7.1.Qa-1b target cells. Antibodies against NKG2A/C did not alter the T cell response, indicating that only the T cell receptor is critically involved in mediating reactivity. Data are representative of four experiments. (C) Exogenous peptide loading competes with endogenously presented epitopes on EC7.1.Qa-1b cells and inhibits the recognition of these target cells by Qa-1b–restricted CTL (left). Qdm (AMAPRTLLL) or Qdm L8K (AMAPRTLKL) peptides were loaded exogenously at the indicated concentrations on EC7.1.Qa-1b cells and IFN-γ release by CTL was measured. Control peptide was the Kb-binding 8-mer SIINFEKL from OVA. The Qdm L8K mutant peptide–Qa-1b complexes fail to interact with CD94/NKG2A or CD94/NKG2C (Kraft et al., 2000), indicating that the loaded peptides interfere with T cell receptor–mediated reactivity. Qdm-specific control CTL (right) was activated by the peptides. Means and standard deviations of triplicate wells are shown for one out of three comparable experiments.
Mentions: To carefully determine the Qa-1b restriction of our isolated T cell clones, we examined their reactivity against two cell panels, based on the TAP-negative EC7.1 lymphoma and TAP-deficient B78H1 melanoma (Fig. 1; Howell et al., 2000; Chiang et al., 2003). Both cell lines are also devoid of MHC class I proteins and single class I molecules were reconstituted by gene transfer. All isolated T cell clones exhibited cytolytic activity (Fig. 1 A) and produced IFN-γ (Fig. 1 B and Fig. S2) against the Qa-1b–expressing cells, but not against cells in which only Db or Kb were introduced. These data convincingly demonstrated the Qa-1b restriction of our T cells and excluded cross-reactivity to the classical class I molecules. Qdm-specific control CTL did not recognize the TAP-deficient tumor targets, as the presentation of Qdm in Qa-1b is TAP dependent (Aldrich et al., 1994). Exogenous loading of Qdm conferred reactivity for this CTL clone (Fig. 1, right). A direct interaction with Qa-1b was revealed by the finding that anti–Qa-1b antibody strongly blocked the recognition by our CTL (Fig. 2 A).

Bottom Line: 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Clinical Oncology, Leiden University Medical Center, 2333 ZA Leiden, Netherlands.

ABSTRACT
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.

Show MeSH
Related in: MedlinePlus