CD8A and cytomegalovirus infection: Increased CD8+CD28− is strongly associated with seropositivity to persistent infections such as cytomegalovirus (CMV),13–15 suggesting that CMV infection may be a driving force behind the accumulation of the CD8+CD28− effector cell expansions.16–18 The loss of the CD28 marker is also shown to be associated with increased CD57 expression on T cells13,19 which is a marker for replicative senescence.