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Allelic variation of MHC structure alters peptide ligands to induce atypical partial agonistic CD8+ T cell function.

Lim DG, Slavik JM, Bourcier K, Smith KJ, Hafler DA - J. Exp. Med. (2003)

Bottom Line: Similar to the effects induced by antigenic altered peptide ligands, weak or partial agonistic T cell functions were identified in individual T cell clones with the recognition of MHC-altered peptide ligands (MAPLs).Whereas early intracellular signaling events were not efficiently induced by these MAPLs, phosphorylated c-Jun slowly accumulated with sustained long-term expression.These data indicate that MAPLs can induce atypical partial agonistic T cell function through structural and biochemical mechanisms similar to altered peptide ligands.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Immunology, Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Institutes of Medicine, Boston, MA 02115-5817, USA.

ABSTRACT
T cell receptors recognize small changes in peptide ligands leading to different T cell responses. Here, we analyzed a panel of HLA-A2-Tax11-19 reactive T cell clones to examine how small allelic variations of MHC molecules could alter the functional outcome of antigen recognition. Similar to the effects induced by antigenic altered peptide ligands, weak or partial agonistic T cell functions were identified in individual T cell clones with the recognition of MHC-altered peptide ligands (MAPLs). Interestingly, one subtype of HLA-A2 molecules induced an unusual type of partial agonistic function; proliferation without cytotoxicity. Modeling of crystallographic data indicated that polymorphic amino acids in the HLA-A2 peptide binding groove, especially the D-pocket, were responsible for this partial agonism. Reciprocal mutations of the Tax peptide side chain engaging the D-pocket indeed restored the agonist functions of the MHC-peptide complex. Whereas early intracellular signaling events were not efficiently induced by these MAPLs, phosphorylated c-Jun slowly accumulated with sustained long-term expression. These data indicate that MAPLs can induce atypical partial agonistic T cell function through structural and biochemical mechanisms similar to altered peptide ligands.

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Tax11-19–HLA-A*0201 reactive T cell clones were differentially restricted by HLA-A2 subtypes. (A) Peptide dose–response cytotoxic activities of T cell clones. LCLs were pulsed for 2 h at different peptide concentrations and used as targets in a 51Cr release assay. The E/T ratio was 10:1 and spontaneous release of 51Cr was <20%. The lysis of peptide nonpulsed cells was <5%, and SEM of triplicate wells were <10%. (B) Summary of CD8+ T cell clone functions with Tax11-19 presentation by different HLA-A2 subtype molecules. LCLs expressing different HLA-A2 subtypes were loaded with 50 μM Tax11-19 and used as target cells or APCs. Cytotoxic activity was tested by 51Cr release assay at an E/T ratio of 10:1. IFN-γ was measured in culture supernatants by ELISA after 48 h of incubation and the detection limit was 100 pg/ml. Proliferation was determined by 18 h [3H]thymidine incorporation assay at the end of a 72-h culture and expressed as S.I. (stimulation index). N.D., not determined.
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fig2: Tax11-19–HLA-A*0201 reactive T cell clones were differentially restricted by HLA-A2 subtypes. (A) Peptide dose–response cytotoxic activities of T cell clones. LCLs were pulsed for 2 h at different peptide concentrations and used as targets in a 51Cr release assay. The E/T ratio was 10:1 and spontaneous release of 51Cr was <20%. The lysis of peptide nonpulsed cells was <5%, and SEM of triplicate wells were <10%. (B) Summary of CD8+ T cell clone functions with Tax11-19 presentation by different HLA-A2 subtype molecules. LCLs expressing different HLA-A2 subtypes were loaded with 50 μM Tax11-19 and used as target cells or APCs. Cytotoxic activity was tested by 51Cr release assay at an E/T ratio of 10:1. IFN-γ was measured in culture supernatants by ELISA after 48 h of incubation and the detection limit was 100 pg/ml. Proliferation was determined by 18 h [3H]thymidine incorporation assay at the end of a 72-h culture and expressed as S.I. (stimulation index). N.D., not determined.

Mentions: The peptide-antigen dose–response curves measuring cytotoxic activity of six T cell clones against LCLs expressing different HLA-A2 subtypes showed a diverse pattern. As shown in Fig. 2 A, all of the T cell clones elicited a similar dose–response cytotoxic activity against LCLs expressing HLA-A*0201, with peptide concentrations inducing half maximal response ranging from 3 nM to 27 nM. LCLs expressing HLA-A*0206, which differs by only one amino acid from A*0201, were also lysed in a similar dose–response manner by all T cell clones, except for TP41 and KS2E11.7, which needed 10–100 times more peptide for the same level of cytolysis. Interestingly, the cytolysis pattern of LCLs expressing other HLA-A2 subtypes, which differ by three or four amino acids, was quite different depending on the individual T cell clones. HLA-A*0202 and A*0205 loaded with Tax11-19 peptide induced cytotoxic activity from the TP27 and TP49 T cell clones, but not from other T cell clones. In contrast, LCLs expressing the HLA-A*0203 subtype were lysed only by the TP41 and KS2E11.7 T cell clones, requiring a 10-fold higher dose of peptide compared with A*0201 (Fig. 2 A). Fig. 2 B summarizes the functional responsiveness including cytotoxicity, proliferation, and IFN-γ secretion of T cell clones when they were stimulated by peptide complexed with different subtypes of HLA-A2. Overall, A*0203 subtype did not elicit any functional responsiveness in four T cell clones, whereas A*0206 induced cytotoxic activities with or without other functions in all of the T cell clones. Unexpectedly, the A*0205 subtype induced proliferation with or without IFN-γ secretion in three out of four T cell clones that did not show cytotoxic activity to this HLA-A2 subtype. Thus, different functional responses of T cell clones to the same antigenic peptide presented by MHC class I molecules, which differ at only a few amino acids, mimic those induced by different antigenic peptides (full agonist, weak agonist, and partial agonist) presented on the same MHC class I molecule.


Allelic variation of MHC structure alters peptide ligands to induce atypical partial agonistic CD8+ T cell function.

Lim DG, Slavik JM, Bourcier K, Smith KJ, Hafler DA - J. Exp. Med. (2003)

Tax11-19–HLA-A*0201 reactive T cell clones were differentially restricted by HLA-A2 subtypes. (A) Peptide dose–response cytotoxic activities of T cell clones. LCLs were pulsed for 2 h at different peptide concentrations and used as targets in a 51Cr release assay. The E/T ratio was 10:1 and spontaneous release of 51Cr was <20%. The lysis of peptide nonpulsed cells was <5%, and SEM of triplicate wells were <10%. (B) Summary of CD8+ T cell clone functions with Tax11-19 presentation by different HLA-A2 subtype molecules. LCLs expressing different HLA-A2 subtypes were loaded with 50 μM Tax11-19 and used as target cells or APCs. Cytotoxic activity was tested by 51Cr release assay at an E/T ratio of 10:1. IFN-γ was measured in culture supernatants by ELISA after 48 h of incubation and the detection limit was 100 pg/ml. Proliferation was determined by 18 h [3H]thymidine incorporation assay at the end of a 72-h culture and expressed as S.I. (stimulation index). N.D., not determined.
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fig2: Tax11-19–HLA-A*0201 reactive T cell clones were differentially restricted by HLA-A2 subtypes. (A) Peptide dose–response cytotoxic activities of T cell clones. LCLs were pulsed for 2 h at different peptide concentrations and used as targets in a 51Cr release assay. The E/T ratio was 10:1 and spontaneous release of 51Cr was <20%. The lysis of peptide nonpulsed cells was <5%, and SEM of triplicate wells were <10%. (B) Summary of CD8+ T cell clone functions with Tax11-19 presentation by different HLA-A2 subtype molecules. LCLs expressing different HLA-A2 subtypes were loaded with 50 μM Tax11-19 and used as target cells or APCs. Cytotoxic activity was tested by 51Cr release assay at an E/T ratio of 10:1. IFN-γ was measured in culture supernatants by ELISA after 48 h of incubation and the detection limit was 100 pg/ml. Proliferation was determined by 18 h [3H]thymidine incorporation assay at the end of a 72-h culture and expressed as S.I. (stimulation index). N.D., not determined.
Mentions: The peptide-antigen dose–response curves measuring cytotoxic activity of six T cell clones against LCLs expressing different HLA-A2 subtypes showed a diverse pattern. As shown in Fig. 2 A, all of the T cell clones elicited a similar dose–response cytotoxic activity against LCLs expressing HLA-A*0201, with peptide concentrations inducing half maximal response ranging from 3 nM to 27 nM. LCLs expressing HLA-A*0206, which differs by only one amino acid from A*0201, were also lysed in a similar dose–response manner by all T cell clones, except for TP41 and KS2E11.7, which needed 10–100 times more peptide for the same level of cytolysis. Interestingly, the cytolysis pattern of LCLs expressing other HLA-A2 subtypes, which differ by three or four amino acids, was quite different depending on the individual T cell clones. HLA-A*0202 and A*0205 loaded with Tax11-19 peptide induced cytotoxic activity from the TP27 and TP49 T cell clones, but not from other T cell clones. In contrast, LCLs expressing the HLA-A*0203 subtype were lysed only by the TP41 and KS2E11.7 T cell clones, requiring a 10-fold higher dose of peptide compared with A*0201 (Fig. 2 A). Fig. 2 B summarizes the functional responsiveness including cytotoxicity, proliferation, and IFN-γ secretion of T cell clones when they were stimulated by peptide complexed with different subtypes of HLA-A2. Overall, A*0203 subtype did not elicit any functional responsiveness in four T cell clones, whereas A*0206 induced cytotoxic activities with or without other functions in all of the T cell clones. Unexpectedly, the A*0205 subtype induced proliferation with or without IFN-γ secretion in three out of four T cell clones that did not show cytotoxic activity to this HLA-A2 subtype. Thus, different functional responses of T cell clones to the same antigenic peptide presented by MHC class I molecules, which differ at only a few amino acids, mimic those induced by different antigenic peptides (full agonist, weak agonist, and partial agonist) presented on the same MHC class I molecule.

Bottom Line: Similar to the effects induced by antigenic altered peptide ligands, weak or partial agonistic T cell functions were identified in individual T cell clones with the recognition of MHC-altered peptide ligands (MAPLs).Whereas early intracellular signaling events were not efficiently induced by these MAPLs, phosphorylated c-Jun slowly accumulated with sustained long-term expression.These data indicate that MAPLs can induce atypical partial agonistic T cell function through structural and biochemical mechanisms similar to altered peptide ligands.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Immunology, Center for Neurologic Diseases, Brigham and Women's Hospital, Harvard Institutes of Medicine, Boston, MA 02115-5817, USA.

ABSTRACT
T cell receptors recognize small changes in peptide ligands leading to different T cell responses. Here, we analyzed a panel of HLA-A2-Tax11-19 reactive T cell clones to examine how small allelic variations of MHC molecules could alter the functional outcome of antigen recognition. Similar to the effects induced by antigenic altered peptide ligands, weak or partial agonistic T cell functions were identified in individual T cell clones with the recognition of MHC-altered peptide ligands (MAPLs). Interestingly, one subtype of HLA-A2 molecules induced an unusual type of partial agonistic function; proliferation without cytotoxicity. Modeling of crystallographic data indicated that polymorphic amino acids in the HLA-A2 peptide binding groove, especially the D-pocket, were responsible for this partial agonism. Reciprocal mutations of the Tax peptide side chain engaging the D-pocket indeed restored the agonist functions of the MHC-peptide complex. Whereas early intracellular signaling events were not efficiently induced by these MAPLs, phosphorylated c-Jun slowly accumulated with sustained long-term expression. These data indicate that MAPLs can induce atypical partial agonistic T cell function through structural and biochemical mechanisms similar to altered peptide ligands.

Show MeSH
Related in: MedlinePlus