CD8A and cytomegalovirus infection: However, while CMV infection increased the size of the peripheral blood CD8 pool by a factor of 1.7 (Fig. 1C), this could not have explained the observed 10 or 12-fold differences in the frequency of flu-specific cells (see Fig. 6A), which was consistent with the absolute loss of CD8 response to LCMV challenge observed in old MCMV-infected mice (Mekker et al. submitted).