期刊
JOURNAL OF IMMUNOLOGY
卷 177, 期 10, 页码 6911-6919出版社
AMER ASSOC IMMUNOLOGISTS
DOI: 10.4049/jimmunol.177.10.6911
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资金
- NIAID NIH HHS [AI61173, AI24157] Funding Source: Medline
- NIGMS NIH HHS [GM55767] Funding Source: Medline
TCRs exhibit a high degree of Ag specificity, even though their affinity for the peptide/MHC ligand is in the micromolar range. To explore how Ag specificity is achieved, we studied murine T cells expressing high-affinity TCRs engineered by in vitro evolution for binding to hemoglobin peptide/class II complex (Hb/1-E-k). These TCRs were shown previously to maintain Ag specificity, despite having up to 800-fold higher affinity. We compared the response of the high-affinity TCRs and the low-affinity 3.L2 TCR toward a comprehensive set of peptides containing single substitutions at each TCR contact residue. This specificity analysis revealed that the increase in affinity resulted in a dramatic increase in the number of stimulatory peptides. The apparent discrepancy between observed degeneracy in the recognition of single amino acid-substituted Hb peptides and overall Ag specificity of the high-affinity TCRs was examined by generating chimeric peptides between the stimulatory Hb and nonstimulatory moth cytochrome c peptides. These experiments showed that MHC anchor residues significantly affected TCR recognition of peptide. The high-affinity TCRs allowed us to estimate the affinity, in the millimolar range, of immunologically relevant interactions of the TCR with peptide/MHC ligands that were previously unmeasurable because of their weak nature. Thus, through the study of high-affinity TCRs, we demonstrated that a TCR is more tolerant of single TCR contact residue substitutions than other peptide changes, revealing that recognition of Ag by T cells can exhibit both specificity and degeneracy.
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