The functional CD8 T cell memory recall repertoire responding to the influenza A M158–66 epitope is polyclonal and shows a complex clonotype distribution

The CD8 memory T cell repertoire to the influenza A derived M158–66 epitope shows a restricted V genes and CDR3 sequences usage. The repertoire is highly polyclonal and the clonotype distribution has been described as consisting of two components, one showing a power law-like distribution and the other composed of a few clonotypes with a very high relative frequency. The question is whether the complex repertoire defined by its ability to flourish in a short term recall culture corresponded to functional cells. Here we show that there is a relation between expression of the degranulation marker CD107 and cytotoxicity or IFN-γ production in CD8 T cell lines and clones. We then examine recently degranulated CD8 cells from recall cultures from four middle aged HLA-A2 subjects and show that these functional cells are polyclonal. The clonotype distributions of the CD8+CD107+ repertoires are complex in the same manner as previously reported. The clonotype composition of CD8+CD107+ repertoires is also very similar to CD8 only repertoires, and to CD8+HLA-A2-M158–66 pentamer positive repertoires. We postulate that multiple exposures during childhood to this conserved influenza A epitope has generated a complex functional repertoire in HLA-A2 individuals.