TBX21 and infection: To determine whether this loss of Tbet was also seen earlier during clone 13 infection, we examined Tbet expression at day 8 p.i. Tbet expression was already slightly reduced by day 8 p.i. (this reduction reached significance with the DbGP276-specific CD8 T cells but only a trend in the DbGP33-specific CD8 T cells) (figure 11G).