title: Contribution of naïve and memory T-cell populations to the human alloimmune response.
abstract: T-cell alloimmunity plays a dominant role in allograft rejection. The precise contribution of naïve and memory T cells to this response however remains unclear. To address this question, we established an ex vivo flow-cytometric assay that simultaneously measures proliferation, precursor frequency and effector molecule (IFNgamma, granzyme B/perforin) production of alloreactive T cells. By applying this assay to peripheral blood mononuclear cells from healthy volunteers, we demonstrate that the CD4+ and CD8+ populations mount similar proliferative responses and contain comparable frequencies of alloreactive precursors. Effector molecule expression, however, was significantly higher among CD8+ T cells. Analysis of sorted naïve and memory T cells showed that alloreactive precursors were equally present in both populations. The CD8+ effector and terminally differentiated effector memory subsets contained the highest proportion of granzyme B/perforin after allostimulation, suggesting that these cells present a significant threat to transplanted organs. Finally, we demonstrate that virus-specific lymphocytes contribute significantly to the alloresponse in certain responder-stimulator HLA combinations, underscoring the importance of T-cell cross-reactivity in alloimmunity. These results provide a quantitative assessment of the roles of naïve and memory T-cell subsets in the normal human alloimmune response and establish a platform for measuring T-cell alloreactivity pre- and posttransplantation.
authors.affiliation: Human Immunology Program, Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: C
authors.initials: C
authors.lastname: Macedo
authors.forename: E A
authors.initials: EA
authors.lastname: Orkis
authors.forename: I
authors.initials: I
authors.lastname: Popescu
authors.forename: B D
authors.initials: BD
authors.lastname: Elinoff
authors.forename: A
authors.initials: A
authors.lastname: Zeevi
authors.forename: R
authors.initials: R
authors.lastname: Shapiro
authors.forename: F G
authors.initials: FG
authors.lastname: Lakkis
authors.forename: D
authors.initials: D
authors.lastname: Metes
mesh_terms: D000328:Adult; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000378:metabolism; D049109:Cell Proliferation; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D053804:Granzymes / Q000494:pharmacology; D006680:HLA Antigens / Q000737:chemistry; D006801:Humans; D007156:Immunologic Memory / Q000276:immunology; D007371:Interferon-gamma / Q000378:metabolism; D008297:Male; D054353:Perforin / Q000378:metabolism; D016176:T-Lymphocyte Subsets / Q000276:immunology; D013601:T-Lymphocytes / Q000166:cytology*
chemical_list: D006680:HLA Antigens; D054353:Perforin; D007371:Interferon-gamma; D053804:Granzymes