The role of T cell receptor avidity in determining T cell repertoires and responses

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T cells are an essential component of the immune system. CD8 T cells, in particular, play a vital role in the immune response to viruses and tumors, predominantly via killing of virally infected cells and tumor cells, as well as the release of inflammatory mediators. T cells must be activated before they can mediate such anti-viral or anti-tumor effects and this activation occurs through the binding of pathogen or tumor fragments (peptides) by a receptor on the surface of T cells (T cell receptor). Each individual has an entire repertoire of T cells with unique T cell receptors which interact with peptides with varying binding strengths. After stimulation of T cells by e.g. viral infection, a subset of the T cell repertoire will become expanded and dominate the anti-viral immune response. This study aims to investigate how, during a viral infection, the strength (or 'avidity') of the interaction between the T cell receptor and the peptide influences (i) whether or not a T cell clone is recruited into the immune response and, if so, its dominance over other clones within that response, and (ii) how efficiently a T cell is activated. It is anticipated that particular virus peptide-specific T cell populations with an overall high avidity will be better able to produce inflammatory mediators and kill infected cells compared to lower avidity T cell populations specific for a different virus peptide. It is also expected that the higher avidity populations will exhibit greater diversity of TCRs. Further, within peptide-specific populations, it is anticipated that the relatively high avidity T cell clones will dominate the specific response. This study will contribute to a greater understanding of factors contributing to T cell recruitment and activation. Armed with this knowledge we will be better able to design vaccines to elicit optimal T cell responses to viral infection.