title: The regulatory T cell effector molecule fibrinogen-like protein 2 is necessary for the development of rapamycin-induced tolerance to fully MHC-mismatched murine cardiac allografts.
abstract: Therapies that promote tolerance in solid organ transplantation will improve patient outcomes by eliminating the need for long-term immunosuppression. To investigate mechanisms of rapamycin-induced tolerance, C3H/HeJ mice were heterotopically transplanted with MHC-mismatched hearts from BALB/cJ mice and were monitored for rejection after a short course of rapamycin treatment. Mice that had received rapamycin developed tolerance with indefinite graft survival, whereas untreated mice all rejected their grafts within 9 days. In vitro, splenic mononuclear cells from tolerant mice maintained primary CD4(+) and CD8(+) immune responses to donor antigens consistent with a mechanism that involves active suppression of immune responses. Furthermore, infection with lymphocytic choriomeningitis virus strain WE led to loss of tolerance suggesting that tolerance could be overcome by infection. Rapamycin-induced, donor-specific tolerance was associated with an expansion of regulatory T (Treg) cells in both the spleen and allograft and elevated plasma levels of fibrinogen-like protein 2 (FGL2). Depletion of Treg cells with anti-CD25 (PC61) and treatment with anti-FGL2 antibody both prevented tolerance induction. Tolerant allografts were populated with Treg cells that co-expressed FGL2 and FoxP3, whereas rejecting allografts and syngeneic grafts were nearly devoid of dual-staining cells. We examined the utility of an immunoregulatory gene panel to discriminate between tolerance and rejection. We observed that Treg-associated genes (foxp3, lag3, tgf-β and fgl2) had increased expression and pro-inflammatory genes (ifn-γ and gzmb) had decreased expression in tolerant compared with rejecting allografts. Taken together, these data strongly suggest that Treg cells expressing FGL2 mediate rapamycin-induced tolerance. Furthermore, a gene biomarker panel that includes fgl2 can distinguish between rejecting and tolerant grafts.
authors.affiliation: Multi-Organ Transplant Program, University Health Network, Toronto, ON, Canada.
authors.forename: Peter
authors.initials: P
authors.lastname: Urbanellis
authors.forename: Wendy
authors.initials: W
authors.lastname: Shyu
authors.forename: Ramzi
authors.initials: R
authors.lastname: Khattar
authors.forename: Jihong
authors.initials: J
authors.lastname: Wang
authors.forename: Anna
authors.initials: A
authors.lastname: Zakharova
authors.forename: Wei
authors.initials: W
authors.lastname: He
authors.forename: Hassan
authors.initials: H
authors.lastname: Sadozai
authors.forename: Achiya Z
authors.initials: AZ
authors.lastname: Amir
authors.forename: Itay
authors.initials: I
authors.lastname: Shalev
authors.forename: M James
authors.initials: MJ
authors.lastname: Phillips
authors.forename: Oyedele
authors.initials: O
authors.lastname: Adeyi
authors.forename: Heather
authors.initials: H
authors.lastname: Ross
authors.forename: David
authors.initials: D
authors.lastname: Grant
authors.forename: Gary A
authors.initials: GA
authors.lastname: Levy
authors.forename: Andrzej
authors.initials: A
authors.lastname: Chruscinski
mesh_terms: D064591:Allografts; D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000276:immunology; D005340:Fibrinogen / Q000235:genetics / Q000276:immunology*; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000276:immunology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics / Q000276:immunology; D006084:Graft Rejection / Q000235:genetics / Q000276:immunology / Q000473:pathology / Q000517:prevention & control*; D053804:Granzymes / Q000235:genetics / Q000276:immunology; D016027:Heart Transplantation; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D007371:Interferon-gamma / Q000235:genetics / Q000276:immunology; D008212:Lymphocyte Depletion / Q000379:methods; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D020123:Sirolimus / Q000494:pharmacology*; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000276:immunology; D023001:Transplantation Tolerance / Q000187:drug effects* / Q000235:genetics; D000093322:Lymphocyte Activation Gene 3 Protein
chemical_list: D015703:Antigens, CD; C490637:Fgl2 protein, mouse; D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse; D007166:Immunosuppressive Agents; D016212:Transforming Growth Factor beta; D007371:Interferon-gamma; D005340:Fibrinogen; D053804:Granzymes; C509214:Gzmb protein, mouse; D020123:Sirolimus; D000093322:Lymphocyte Activation Gene 3 Protein; C000720327:Lag3 protein, mouse
keywords: fgl2; regulatory T cell; tolerance; transplantation