In this report we have inspected whether difficulties in controlling viral infections negatively impacts the generation of CD127high memory T cells. Using both MHC class I and II tetramers we reveal that CD127 low T cells are not necessarily rapidly deleted but can persist in a pseudoeffector state in which they display the hallmarks of activated effector cells but are functionally inferior. CD127high cells can, however, emerge if the infection is contained. We also show that in the absence of CD4 T cell help significant populations of CD127high CD8 T cells fail to emerge. Analyses of cytokine-producing activities by both mouse and human CD8 T cells further document that the extended maintenance of T cells in a CD127 low state has functional consequences which manifest as an impairment of IL-2 production. Copyright © 2005 by The American Association of Immunulogists, Inc.