Contribution of T cell receptor affinity to overall avidity for virus-specific CD8+ T cell responses

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National Academy of Sciences

RESUMO

Prior analysis has characterized the clonal characteristics of effector CD8+ T cells specific for the prominent influenza A virus nucleoprotein (NP) and acid polymerase (PA) peptides presented by H2Db. Using a single-cell approach and determination of CDR3β profiles, a limited, predominantly “public” repertoire was found for CD8+DbNP366+Vβ8.3+ cells, whereas diverse and “private” T cell antigen receptor (TCR)β clonotypes were typical of the CD8+DbPA224+Vβ7+ response. This single-cell approach has now been used to relate the contributions of particular clonotypes (or affinities) to high-avidity TCRs, as defined by binding under conditions of limiting tetramer availability. At least by the measure of CDR3β usage, no difference could be found between total and high-avidity populations in the spectrum of TCR-pMHC affinities throughout the limited, and relatively public, CD8+DbNP366+Vβ8.3+ populations. Conversely, the more even (by clone size), diverse, and private CD8+DbPA224+Vβ7+ response was characterized by the clear partitioning of the largest T cell clones in the high-avidity compartment. These results suggest that the relatively constrained CD8+DbNP366+Vβ8.3+ set utilizes a relatively narrow range of affinities, whereas the broader CD8+DbPA224+Vβ7+ response is induced at a range of TCR-pMHC affinities. Thus, whereas TCR sequence (or affinity) appears to contribute substantially to the avidity profile of diverse virus-specific CD8+ populations, other mechanisms may be prominent where the TCR spectrum is more limited.

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