title: A biochemical signature for rapid recall of memory CD4 T cells.
abstract: Mechanisms for the rapid recall response mediated by memory T cells remain unknown. In this study, we present a novel, multiparameter analysis of TCR-coupled signaling and function in resting and activated naive and memory CD4 T cells, revealing a biochemical basis for immunological recall. We identify a striking elevation in expression of the proximal tyrosine kinase Zap70 in resting Ag-specific and polyclonal mouse memory vs naive CD4 T cells that is stably maintained independent of protein synthesis. Elevated Zap70 protein levels control effector function as IFN-gamma production occurs exclusively from the Zap70(high) fraction of activated T cells in vitro and in vivo, and specific down-modulation of Zap70 expression in memory CD4 T cells by small interfering RNA or protein inhibition significantly reduces rapid IFN-gamma production. Downstream of Zap70, we show quantitative differences in distal phosphorylation associated with effector function in naive and memory subsets, with low accumulation of phosphorylation in memory T cells producing IFN-gamma at early time points, contrasting extensive phosphorylation associated with IFN-gamma production following sustained activation of naive T cells. Our results reveal a novel biochemical signature imparted to memory CD4 T cells enabling efficacious responses through increased Zap70 expression and reduced accumulation of downstream signaling events.
authors.affiliation: Division of Transplantation, Department of Surgery, School of Medicine, University of Maryland, Baltimore, MD 21201, USA.
authors.forename: Meena R
authors.initials: MR
authors.lastname: Chandok
authors.forename: Francesca I
authors.initials: FI
authors.lastname: Okoye
authors.forename: Modesta P
authors.initials: MP
authors.lastname: Ndejembi
authors.forename: Donna L
authors.initials: DL
authors.lastname: Farber
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*; D015536:Down-Regulation / Q000276:immunology; D018984:Epitopes, T-Lymphocyte / Q000276:immunology; D007156:Immunologic Memory; D016130:Immunophenotyping; D007371:Interferon-gamma / Q000096:biosynthesis; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D008822:Mice, Transgenic; D010047:Ovalbumin / Q000276:immunology; D011948:Receptors, Antigen, T-Cell / Q000502:physiology; D016192:Resting Phase, Cell Cycle / Q000276:immunology; D015398:Signal Transduction / Q000276:immunology; D015854:Up-Regulation / Q000276:immunology; D051746:ZAP-70 Protein-Tyrosine Kinase / Q000096:biosynthesis / Q000502:physiology