title: Immunobiology of allograft rejection in the absence of IFN-gamma: CD8+ effector cells develop independently of CD4+ cells and CD40-CD40 ligand interactions.
abstract: Both wild-type (WT) and IFN-gamma-deficient (IFN-gamma(-/-)) C57BL/6 mice can rapidly reject BALB/c cardiac allografts. When depleted of CD8(+) cells, both WT and IFN-gamma(-/-) mice rejected their allografts, indicating that these mice share a common CD4-mediated, CD8-independent mechanism of rejection. However, when depleted of CD4(+) cells, WT mice accepted their allografts, while IFN-gamma(-/-) recipients rapidly rejected them. Hence, IFN-gamma(-/-), but not WT mice developed an unusual CD8-mediated, CD4-independent, mechanism of allograft rejection. Allograft rejection in IFN-gamma(-/-) mice was associated with intragraft accumulation of IL-4-producing cells, polymorphonuclear leukocytes, and eosinophils. Furthermore, this form of rejection was resistant to treatment with anti-CD40 ligand (CD40L) mAb, which markedly prolonged graft survival in WT mice. T cell depletion studies verified that anti-CD40L treatment failed to prevent CD8-mediated allograft rejection in IFN-gamma(-/-) mice. However, anti-CD40L treatment did prevent CD4-mediated rejection in IFN-gamma(-/-) mice, although grafts were eventually rejected when CD8(+) T cells repopulated the periphery. The IL-4 production and eosinophil influx into the graft that occurred during CD8-mediated rejection were apparently epiphenomenal, since treatment with anti-IL-4 mAb blocked intragraft accumulation of eosinophils, but did not interfere with allograft rejection. These studies demonstrate that a novel, CD8-mediated mechanism of allograft rejection, which is resistant to experimental immunosuppression, can develop when IFN-gamma is limiting. An understanding of this mechanism is confounded by its association with Th2-like immune events, which contribute unique histopathologic features to the graft but are apparently unnecessary for the process of allograft rejection.
authors.affiliation: Department of Surgery, Section of General Surgery, University of Michigan School of Medicine, Ann Arbor, MI 48109, USA. kbishop@umich.edu
authors.forename: D K
authors.initials: DK
authors.lastname: Bishop
authors.forename: S
authors.initials: S
authors.lastname: Chan Wood
authors.forename: E J
authors.initials: EJ
authors.lastname: Eichwald
authors.forename: C G
authors.initials: CG
authors.lastname: Orosz
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D019013:CD40 Antigens / Q000378:metabolism* / Q000502:physiology; D023201:CD40 Ligand / Q000378:metabolism* / Q000502:physiology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology; D002465:Cell Movement / Q000235:genetics / Q000276:immunology; D005260:Female; D006084:Graft Rejection / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D016027:Heart Transplantation / Q000276:immunology / Q000473:pathology; D007371:Interferon-gamma / Q000172:deficiency* / Q000235:genetics*; D015847:Interleukin-4 / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016176:T-Lymphocyte Subsets / Q000276:immunology / Q000378:metabolism; D014181:Transplantation Immunology / Q000235:genetics; D014184:Transplantation, Homologous
chemical_list: D019013:CD40 Antigens; D023201:CD40 Ligand; D015847:Interleukin-4; D007371:Interferon-gamma