CD8A and infection: CD25 is transiently expressed immediately following activation, prior to cell division,23, 24 while the active form of CD43 is maintained on effector cells until progression to a memory phenotype.25 Therefore, it is likely that during the course of the infection, the CD25+CD43+ CD8+ T cells progresses to the CD25−CD43+ phenotype; alternatively, these may be two distinct cell populations.