title: Dynamics and requirements of T cell clonal expansion in vivo at the single-cell level: effector function is linked to proliferative capacity.
abstract: The adoptive transfer of TCR-transgenic T cells into syngeneic recipients allows characterization of individual T cells during in vivo immune responses. However, the proliferative behavior of individual T cells and its relationship to effector and memory function has been difficult to define. Here, we used a fluorescent dye to dissect and quantify T cell proliferative dynamics in vivo. We find that the average Ag-specific CD4+ T cell that undergoes division in vivo generates >20 daughter cells. TCR and CD28 signals cooperatively determine the degree of primary clonal expansion by increasing both the proportion of Ag-specific T cells that divide and the number of rounds of division the responding T cells undergo. Nonetheless, despite optimal signaling, up to one-third of Ag-specific cells fail to divide even though they show phenotypic evidence of Ag encounter. Surprisingly, however, transgenic T cells maturing on a RAG-2-/- background exhibit a responder frequency of 95-98% in vivo, suggesting that maximal proliferative potential requires either a naive phenotype or allelic exclusion at the TCRalpha locus. Finally, studies reveal division cycle-dependent expression of markers of T cell differentiation, such as CD44, CD45RB, and CD62L, and show also that expression of the cytokines IFN-gamma and IL-2 depends primarily on cell division rather than on receipt of costimulatory signals. These results provide a quantitative assessment of T cell proliferation in vivo and define the relationship between cell division and other parameters of the immune response including cytokine production, the availability of costimulation, and the capacity for memory.
authors.affiliation: Department of Medicine, University of Pennsylvania, Philadelphia 19104, USA.
authors.forename: H
authors.initials: H
authors.lastname: Gudmundsdottir
authors.forename: A D
authors.initials: AD
authors.lastname: Wells
authors.forename: L A
authors.initials: LA
authors.lastname: Turka
mesh_terms: D019264:Adoptive Transfer; D000483:Alleles; D000818:Animals; D018106:CD28 Antigens / Q000502:physiology; D018791:CD4 Lymphocyte Count; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism / Q000637:transplantation; D002453:Cell Cycle / Q000276:immunology; D002454:Cell Differentiation / Q000276:immunology; D002455:Cell Division / Q000235:genetics / Q000276:immunology; D002999:Clone Cells; D016207:Cytokines / Q000096:biosynthesis; D018984:Epitopes, T-Lymphocyte / Q000276:immunology; D008198:Lymph Nodes / Q000166:cytology / Q000276:immunology; D008213:Lymphocyte Activation / Q000235:genetics / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008822:Mice, Transgenic; D010047:Ovalbumin / Q000008:administration & dosage / Q000276:immunology; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics; D015398:Signal Transduction / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000166:cytology* / Q000276:immunology* / Q000378:metabolism
chemical_list: D018106:CD28 Antigens; D016207:Cytokines; D018984:Epitopes, T-Lymphocyte; D016693:Receptors, Antigen, T-Cell, alpha-beta; D010047:Ovalbumin