Distinct T Cell Interactions with HLA Class II Tetramers Characterize a Spectrum of TCR Affinities in the Human Antigen-Specific T Cell Response

Abstract

The polyclonal nature of T cells expanding in an ongoing immune response results in a range of disparate affinities and activation potential. Recently developed human class II tetramers provide a means to analyze this diversity by direct characterization of the trimolecular TCR-peptide-MHC interaction in live cells. Two HSV-2 VP16369–379-specific, DQA1*0102/DQB1*0602 (DQ0602)-restricted T cell clones were compared by means of T cell proliferation assay and HLA-DQ0602 tetramer staining. These two clones were obtained from the same subject, but show different TCR gene usage. Clone 48 was 10-fold more sensitive to VP16369–379 peptide stimulation than clone 5 as assayed by proliferation assays, correlating with differences in MHC tetramer binding. Clone 48 gave positive staining with the DQ0602/VP16369–379 tetramer at either 23 or 37°C. Weak staining was also observed at 4°C. Clone 5 showed weaker staining compared with clone 48 at 37°C, and no staining was observed at 23°C or on ice. Receptor internalization was not required for positive staining. Competitive binding indicates that the cell surface TCR of clone 48 has higher affinity for the DQ0602/VP16369–379 complex than clone 5. The higher binding affinity of clone 48 for the peptide-MHC complex also correlates with a slower dissociation rate compared with clone 5.