CD8A and infection: Corresponding to CD8+ T cells that develop in the infection with SFG rickettsiae, CD8+ T cells from R. typhi-infected BALB/c and C57BL/6 mice produce increased levels of IFNγ and Granzyme B upon in vitro restimulation with phorbol myristate acetate (PMA)/Ionomycin [121,122], indicating enhanced cytotoxic activity.