title: Homeostatic proliferation of lymphocytes results in augmented memory-like function and accelerated allograft rejection.
abstract: Homeostatic proliferation is a normal physiological process triggered by lymphopenia to maintain a constant level of T cells. It becomes the predominant source of new T cells in adulthood after thymus regression. T cells that have undergone homeostatic proliferation acquire the memory phenotype, cause autoimmune disease, and are resistant to tolerance induction protocols. Transplantation is a rare example in which lymphopenia is deliberately induced for its immunosuppressive effect. However, it is not known whether the homeostatic proliferation that follows will have the opposite effect and accelerate rejection. We show that T cells that have undergone homeostatic proliferation acquire a memory phenotype, spontaneously skews toward the Th1 phenotype, even in the absence of antigenic stimulus. Interestingly, in contrast, the percentage of Foxp3(+) regulatory T cells increased by 28-fold following homeostatic proliferation. Using a mouse life-sustaining kidney transplant model, we showed that T cells that have gone through homeostatic proliferation in lymphopenic hosts transformed chronic rejection to acute rejection of a single MHC class II-mismatched kidney allograft. T cells that have undergone homeostatic proliferation consistently cause reliable rejection even when bona fide memory T cells cannot. These functional changes are long-lasting and not restricted to the acute phase of homeostatic proliferation. Our findings have important implications for tolerance induction or graft-prolonging protocols involving leukocyte depletion such as irradiation bone marrow chimera, T cell-depleting Abs, and lymphopenia induced by infections such as CMV and HIV.
authors.affiliation: Department of Nephrology and Transplantation, King's College London School of Medicine at Guy's, King's and St. Thomas' Hospital, London, United Kingdom.
authors.forename: Victoria F
authors.initials: VF
authors.lastname: Moxham
authors.forename: Julieta
authors.initials: J
authors.lastname: Karegli
authors.forename: Richard E
authors.initials: RE
authors.lastname: Phillips
authors.forename: Kathryn L
authors.initials: KL
authors.lastname: Brown
authors.forename: Thomas T
authors.initials: TT
authors.lastname: Tapmeier
authors.forename: Robert
authors.initials: R
authors.lastname: Hangartner
authors.forename: Steven H
authors.initials: SH
authors.lastname: Sacks
authors.forename: Wilson
authors.initials: W
authors.lastname: Wong
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D049109:Cell Proliferation; D002908:Chronic Disease; D006084:Graft Rejection / Q000276:immunology*; D018398:Homeodomain Proteins / Q000235:genetics; D006706:Homeostasis / Q000276:immunology*; D007156:Immunologic Memory; D016030:Kidney Transplantation / Q000276:immunology*; D016131:Lymphocyte Subsets / Q000166:cytology* / Q000276:immunology* / Q000637:transplantation; D017710:Lymphocyte Transfusion; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D013154:Spleen / Q000166:cytology / Q000276:immunology / Q000637:transplantation; D013997:Time Factors; D014184:Transplantation, Homologous / Q000276:immunology
chemical_list: D018398:Homeodomain Proteins; C064658:RAG-1 protein