title: Effector CD4 T cells are biochemically distinct from the memory subset: evidence for long-term persistence of effectors in vivo.
abstract: Memory T cell responses are believed to be mediated by long-lived memory T cells that arise directly from a subset of short-lived, activated effector T cells that have reverted to the resting state. Although widely accepted, definitive proof that memory T cells arise from effectors is lacking because of the inability to reliably distinguish these subsets based on known phenotypic or functional parameters. We have used a biochemical approach to distinguish effector and memory CD4 T cell subsets and follow the differentiative fate of effector cells in vivo. When examined biochemically, effector and memory CD4 T cells are strikingly distinct and exhibit qualitative and quantitative differences in tyrosine phosphorylation. These effector-specific patterns were identical in effectors derived either from naive CD4 T cells (primary effectors) or memory CD4 T cells (memory effectors). To monitor the fate of effector cells in vivo, Ag-activated CD4+ TCR-transgenic T cells were transferred into irradiated BALB/c mice. These TCR-transgenic CD4 T cells persisted in adoptive hosts for several months, gave a recall response to Ag, yet exhibited effector-specific biochemical profiles. These results suggest that a subset of effector CD4 T cells can persist in vivo and contribute to long-term immunity by mediating secondary immune responses.
authors.affiliation: Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA.
authors.forename: M
authors.initials: M
authors.lastname: Ahmadzadeh
authors.forename: S F
authors.initials: SF
authors.lastname: Hussain
authors.forename: D L
authors.initials: DL
authors.lastname: Farber
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000737:chemistry* / Q000166:cytology* / Q000378:metabolism / Q000637:transplantation; D002454:Cell Differentiation / Q000276:immunology; D002470:Cell Survival / Q000276:immunology; D007156:Immunologic Memory; D016130:Immunophenotyping; D007399:Interphase / Q000276:immunology; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D008822:Mice, Transgenic; D010766:Phosphorylation; D016176:T-Lymphocyte Subsets / Q000737:chemistry* / Q000166:cytology* / Q000378:metabolism / Q000637:transplantation