title: Heme oxygenase-1 modulates the allo-immune response by promoting activation-induced cell death of T cells.
abstract: Heme oxygenase-1 (HO-1), which degrades heme into three products (carbon monoxide, free iron, and biliverdin), plays a protective role in many models of disease via its anti-inflammatory, anti-apoptotic, and anti-proliferative actions. Overexpression of HO-1 has been shown to suppress immune responses and prolong the survival of allografts; however, the underlying mechanism is not clear. We demonstrate two "new" properties of HO-1 that mediate activation induced cell death (AICD) of allo-antigen-responsive murine CD4+ T cells, resulting in immunomodulation. First, it functions in vivo and in vitro to "boost" the proliferative response of CD4+ T cells to allo-antigens in the early phase of allo-antigen-driven immune responses. This "boosting" effect is accompanied with a significant increase of activation markers and IL-2 production. Second, it exerts a pro-apoptotic effect in those activated T cells after the initial burst of proliferation. We further show that the AICD effect is mediated through the Fas/CD95-FasL signal transduction pathway. Correlating with the above-mentioned findings is the observed prolongation of mouse heart graft survival when HO-1 is expressed in vivo in both donor and recipient. In conclusion, induction of HO-1 expression accelerates clonal deletion of peripheral alloreactive CD4+ T cells by promoting AICD, which is presumably a key mechanism for its immunomodulatory effects such as in prolonging the survival of transplanted organs.
authors.affiliation: Immunobiology Research Center, Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: James
authors.initials: J
authors.lastname: McDaid
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Yamashita
authors.forename: Angelo
authors.initials: A
authors.lastname: Chora
authors.forename: Robert
authors.initials: R
authors.lastname: Ollinger
authors.forename: Terry B
authors.initials: TB
authors.lastname: Strom
authors.forename: Xian C
authors.initials: XC
authors.lastname: Li
authors.forename: Fritz H
authors.initials: FH
authors.lastname: Bach
authors.forename: Miguel P
authors.initials: MP
authors.lastname: Soares
mesh_terms: D000818:Animals; D017209:Apoptosis; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology* / Q000201:enzymology / Q000276:immunology*; D016923:Cell Death; D004790:Enzyme Induction / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects; D006419:Heme Oxygenase (Decyclizing) / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D051547:Heme Oxygenase-1; D006651:Histocytochemistry; D007150:Immunohistochemistry; D007376:Interleukin-2 / Q000032:analysis / Q000378:metabolism; D007519:Isoantigens / Q000276:immunology*; D008213:Lymphocyte Activation / Q000502:physiology*; D007959:Lymphocyte Culture Test, Mixed; D008297:Male; D008565:Membrane Proteins; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008817:Mice, Mutant Strains; D008822:Mice, Transgenic; D010047:Ovalbumin / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D019014:fas Receptor / Q000032:analysis
chemical_list: D007376:Interleukin-2; D007519:Isoantigens; D008565:Membrane Proteins; D012333:RNA, Messenger; D019014:fas Receptor; D010047:Ovalbumin; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; C496542:Hmox1 protein, mouse