title: Autoreactive T cells induce necrosis and not BCL-2-regulated or death receptor-mediated apoptosis or RIPK3-dependent necroptosis of transplanted islets in a mouse model of type 1 diabetes.
abstract: OBJECTIVE
  Type 1 diabetes results from T cell-mediated destruction of pancreatic beta cells. The mechanisms of beta cell destruction in vivo, however, remain unclear. We aimed to test the relative roles of the main cell death pathways: apoptosis, necrosis and necroptosis, in beta cell death in the development of CD4(+) T cell-mediated autoimmune diabetes.
  
  
  METHODS
  We altered expression levels of critical cell death proteins in mouse islets and tested their ability to survive CD4(+) T cell-mediated attack using an in vivo graft model.
  
  
  RESULTS
  Loss of the B cell leukaemia/lymphoma 2 (BCL-2) homology domain 3-only proteins BIM, PUMA or BID did not protect beta cells from this death. Overexpression of the anti-apoptotic protein BCL-2 or combined deficiency of the pro-apoptotic multi-BCL2 homology domain proteins BAX and BAK also failed to prevent beta cell destruction. Furthermore, loss of function of the death receptor Fas or its essential downstream signalling molecule Fas-associated death domain (FADD) in islets was also not protective. Using electron microscopy we observed that dying beta cells showed features of necrosis. However, islets deficient in receptor-interacting serine/threonine protein kinase 3 (RIPK3), a critical initiator of necroptosis, were still normally susceptible to CD4(+) T cell-mediated destruction. Remarkably, simultaneous inhibition of apoptosis and necroptosis by combining loss of RIPK3 and overexpression of BCL-2 in islets did not protect them against immune attack either.
  
  
  CONCLUSIONS
  Collectively, our data indicate that beta cells die by necrosis in autoimmune diabetes and that the programmed cell death pathways apoptosis and necroptosis are both dispensable for this process.
authors.affiliation: St Vincent's Institute of Medical Research, 41 Victoria Parade, Fitzroy, Melbourne, VIC, 3065, Australia.
authors.forename: Yuxing
authors.initials: Y
authors.lastname: Zhao
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Scott
authors.forename: Stacey
authors.initials: S
authors.lastname: Fynch
authors.forename: Lorraine
authors.initials: L
authors.lastname: Elkerbout
authors.forename: W Wei-Lynn
authors.initials: WW
authors.lastname: Wong
authors.forename: Kylie D
authors.initials: KD
authors.lastname: Mason
authors.forename: Andreas
authors.initials: A
authors.lastname: Strasser
authors.forename: David C
authors.initials: DC
authors.lastname: Huang
authors.forename: Thomas W H
authors.initials: TW
authors.lastname: Kay
authors.forename: Helen E
authors.initials: HE
authors.lastname: Thomas
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000502:physiology; D015551:Autoimmunity / Q000502:physiology*; D003921:Diabetes Mellitus, Experimental / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D006084:Graft Rejection / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D007515:Islets of Langerhans / Q000276:immunology / Q000378:metabolism / Q000473:pathology*; D016381:Islets of Langerhans Transplantation / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D016688:Mice, Inbred NOD; D008822:Mice, Transgenic; D009336:Necrosis / Q000235:genetics / Q000276:immunology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000502:physiology; D053422:Receptor-Interacting Protein Serine-Threonine Kinases / Q000235:genetics / Q000502:physiology; D053218:Receptors, Death Domain / Q000235:genetics / Q000502:physiology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D019253:Proto-Oncogene Proteins c-bcl-2; D053218:Receptors, Death Domain; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; C485615:Ripk3 protein, mouse