"PF inhibits activation-mediated loss of superantigen-reactive CD4 as well as CD8 T cells in vivo without significantly affecting their activation, and inhibits activation-induced death and caspase induction in stimulated CD4 as well as CD8 T cells in vitro without preventing the induction of activation markers.
Consistent with this ability to prevent activation-induced death in not only CD4 but also CD8 T cells, PF also enhances the persistence of CD8 T cell responses in vivo."