title: TLR agonists abrogate costimulation blockade-induced prolongation of skin allografts.
abstract: Costimulation blockade protocols are effective in prolonging allograft survival in animal models and are entering clinical trials, but how environmental perturbants affect graft survival remains largely unstudied. We used a costimulation blockade protocol consisting of a donor-specific transfusion and anti-CD154 mAb to address this question. We observed that lymphocytic choriomeningitis virus infection at the time of donor-specific transfusion and anti-CD154 mAb shortens allograft survival. Lymphocytic choriomeningitis virus 1) activates innate immunity, 2) induces allo-cross-reactive T cells, and 3) generates virus-specific responses, all of which may adversely affect allograft survival. To investigate the role of innate immunity, mice given costimulation blockade and skin allografts were coinjected with TLR2 (Pam3Cys), TLR3 (polyinosinic:polycytidylic acid), TLR4 (LPS), or TLR9 (CpG) agonists. Costimulation blockade prolonged skin allograft survival that was shortened after coinjection by TLR agonists. To investigate underlying mechanisms, we used "synchimeric" mice which circulate trace populations of anti-H2b transgenic alloreactive CD8+ T cells. In synchimeric mice treated with costimulation blockade, coadministration of all four TLR agonists prevented deletion of alloreactive CD8+ T cells and shortened skin allograft survival. These alloreactive CD8+ T cells 1) expressed the proliferation marker Ki-67, 2) up-regulated CD44, and 3) failed to undergo apoptosis. B6.TNFR2-/- and B6.IL-12R-/- mice treated with costimulation blockade plus LPS also exhibited short skin allograft survival whereas similarly treated B6.CD8alpha-/- and TLR4-/- mice exhibited prolonged allograft survival. We conclude that TLR signaling abrogates the effects of costimulation blockade by preventing alloreactive CD8+ T cell apoptosis through a mechanism not dependent on TNFR2 or IL-12R signaling.
authors.affiliation: Division of Diabetes, Department of Medicine, University of Massachusetts Medical School, Worcester, MA 01605, USA.
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Thornley
authors.forename: Michael A
authors.initials: MA
authors.lastname: Brehm
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Markees
authors.forename: Leonard D
authors.initials: LD
authors.lastname: Shultz
authors.forename: John P
authors.initials: JP
authors.lastname: Mordes
authors.forename: Raymond M
authors.initials: RM
authors.lastname: Welsh
authors.forename: Aldo A
authors.initials: AA
authors.lastname: Rossini
authors.forename: Dale L
authors.initials: DL
authors.lastname: Greiner
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage; D017209:Apoptosis / Q000276:immunology; D023201:CD40 Ligand / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000187:drug effects; D045744:Cell Line, Tumor; D017637:Clonal Deletion / Q000187:drug effects; D005260:Female; D006082:Graft Enhancement, Immunologic; D006084:Graft Rejection / Q000276:immunology / Q000517:prevention & control*; D006131:Growth Inhibitors / Q000008:administration & dosage*; D008070:Lipopolysaccharides / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D018345:Mice, Knockout; D008822:Mice, Transgenic; D011828:Radiation Chimera; D018123:Receptors, Interleukin / Q000378:metabolism; D053707:Receptors, Interleukin-12; D047889:Receptors, Tumor Necrosis Factor, Type II / Q000378:metabolism; D016038:Skin Transplantation / Q000276:immunology*; D051197:Toll-Like Receptor 4 / Q000378:metabolism; D051193:Toll-Like Receptors / Q000819:agonists*; D014184:Transplantation, Homologous
chemical_list: D000911:Antibodies, Monoclonal; D006131:Growth Inhibitors; D008070:Lipopolysaccharides; D018123:Receptors, Interleukin; D053707:Receptors, Interleukin-12; D047889:Receptors, Tumor Necrosis Factor, Type II; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D023201:CD40 Ligand