Transplantation of purified islet cells in diabetic BB rats

The ability to prepare purified islet Beta-cell aggregates was used to examine the survival of this cell type after allotransplantation in diabetic BB rats. The aggregates were intraportally implanted in numbers that were previously found to correct a streptozotocin-induced diabetic state in syngeneic or allogeneic Brown Norway recipients. When the grafts were prepared from RT1(u/l) donors, which shared the MHC-class I antigen with the BB recipients (RT1(u/u), their implant sites became diffusely infiltrated by inflammatory cells and their metabolic function was completely lost within 5 weeks. MHC-class I incompatible islet Beta-cell allografts (RT1(n/n) exhibited a longer survival, in particular when combined with other islet endocrine cells and/or when covered by a 5-week cyclosporin treatment. In the latter combination, 10 of 12 BB rat recipients remained normoglycaemic over the 10-week observation period, their liver implants presenting a comparable insulin reserve and similarly discrete mononuclear cell infiltration as streptozotocin-diabetic Brown Norway rats receiving this treatment. However, administration of cyclosporin to diabetic BB rats was associated with a morbidity that was not observed in drug-treated streptozotocin-diabetic Brown Norway animals or in untreated diabetic BB rats. It is concluded that MHC-incompatible in islet Beta cells can induce a long-term normalization in diabetic BB rats provided that they are implanted under conditions which allow allograft acceptance. The standardized preparation of purified islet Beta-cell grafts can help assessing the conditions for successful transplantations in diabetes with an autoimmune origin

Ian4 is required for mitochondrial integrity and T cell survival

Apoptosis is a regulated cell death program controlled by extrinsic and intrinsic signaling pathways. The intrinsic pathway involves stress signals that activate pro-apoptotic members of the Bcl-2 family, inducing permeabilization of mitochondria and release of apoptogenic factors. These proteins localize to the outer mitochondrial membrane. Ian4, a mitochondrial outer membrane protein with GTP-binding activity, is normally present in thymocytes, T cells, and B cells. We and others have recently discovered that a mutation in the rat Ian4 gene results in severe T cell lymphopenia that is associated with the expression of autoimmune diabetes. The mechanism by which Ian4 controls T cell homeostasis is unknown. Here we show that the absence of Ian4 in T cells causes mitochondrial dysfunction, increased mitochondrial levels of stress-inducible chaperonins and a leucine-rich protein, and T cell-specific spontaneous apoptosis. T cell activation and caspase 8 inhibition both prevented apoptosis, whereas transfection of T cells with Ian4-specific small interfering RNA recapitulated the apoptotic phenotype. The findings establish Ian4 as a tissue-specific regulator of mitochondrial integrity