title: Modulation of T cell homeostasis and alloreactivity under continuous FTY720 exposure.
abstract: The immunomodulator FTY720 inhibits lymph node (LN) and thymic egress, thereby constraining T cell circulation and reducing peripheral T cell numbers. Here, we analyzed in mouse models the as yet scarcely characterized impact of long-term (up to 6 months) FTY720 exposure on T cell homeostasis and possible consequences for alloreactivity. In green fluorescent protein (GFP) hemopoietic chimeras, the turnover of (initially GFP(-)) peripheral T cell pools was markedly delayed under FTY720, while normal homeostatic differences between CD4 and CD8 T cell sub-populations were retained or amplified further. Homeostatic proliferation was enhanced, and within shrinking T cell pools, the proportions of effector memory phenotype CD4 T cells (CD4T(PEM)) increased in spleens and LNs and of central memory phenotype CD8 T cells (CD8T(PCM)) in LNs. By contrast, the fractions of CD8T(PEM) and CD4T(PCM) remained stably small under FTY720. The enrichment for CD4T(PEM) and CD8T(PCM) correlated with larger proportions of IFNgamma-producing T cells upon nonspecific but not allospecific stimulation. Splenic CD4 T cells from FTY720-treated mice proliferated more strongly upon transfer to semi-allogeneic hosts. However, heart allograft survival was not compromised in FTY720 pre-treated recipients. It correlated with reduced intra-graft CD8 T cells, and the longest surviving transplants contained the highest numbers of CD4 T cells. Thus, continuous FTY720 exposure reveals differential homeostatic responses by memory phenotype CD4 and CD8 T cell sub-populations, and it may enhance alloreactive CD4 T cell proliferation and tissue infiltration without accelerating allograft rejection.
authors.affiliation: Department of Autoimmunity and Transplantation, Novartis Institutes for Biomedical Research, 4002 Basel, Switzerland. barbara.metzler@novartis.com
authors.forename: Barbara
authors.initials: B
authors.lastname: Metzler
authors.forename: Patrick
authors.initials: P
authors.lastname: Gfeller
authors.forename: Grazyna
authors.initials: G
authors.lastname: Wieczorek
authors.forename: Jianping
authors.initials: J
authors.lastname: Li
authors.forename: Barbara
authors.initials: B
authors.lastname: Nuesslein-Hildesheim
authors.forename: Andreas
authors.initials: A
authors.lastname: Katopodis
authors.forename: Matthias
authors.initials: M
authors.lastname: Mueller
authors.forename: Volker
authors.initials: V
authors.lastname: Brinkmann
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D018414:CD8-Positive T-Lymphocytes / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D005260:Female; D000068876:Fingolimod Hydrochloride; D006084:Graft Rejection; D006085:Graft Survival; D016027:Heart Transplantation / Q000276:immunology*; D006706:Homeostasis / Q000187:drug effects; D007156:Immunologic Memory; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D007371:Interferon-gamma / Q000096:biosynthesis / Q000276:immunology; D008198:Lymph Nodes / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D011409:Propylene Glycols / Q000494:pharmacology*; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D013154:Spleen / Q000166:cytology / Q000276:immunology
chemical_list: D007166:Immunosuppressive Agents; D011409:Propylene Glycols; D007371:Interferon-gamma; D000068876:Fingolimod Hydrochloride; D013110:Sphingosine