The exact process that leads to the eruption of autoimmune reactions against β cells and the evolution of diabetes is not fully understood. Macrophages and T cells may launch an initial immune reaction against the pancreatic islets of Langerhans, provoking inflammation and destructive insulitis. The information on the molecular mechanisms of the emergence of β cell injury is controversial and points to possibly important roles for the perforin–granzyme, Fas–Fas-ligand (FasL) and tumor-necrosis-factor-mediated apoptotic pathways. FasL has several unique features that make (...) it a potentially ideal immunomodulatory tool. Most important, FasL is selectively toxic to cytotoxic T cells and less harmful to regulatory T cells. This review discusses the intrinsic sensitivity of β cells to FasL-mediated apoptosis, the conditions that underlie this β cell sensitivity, and the feasibility of using FasL to arrest autoimmunity and prevent islet allograft rejection. In both the autoimmune and transplant settings, it is imperative to progress from the administration of nonspecific immunosuppressive therapy to the concept of β-cell-specific immunomodulation. FasL evolves as a prime candidate for antigen-specific immunomodulation. BioEssays 28: 211–222, 2006. © 2006 Wiley periodicals, Inc. (shrink)

The exact process that leads to the eruption of autoimmune reactions against β cells and the evolution of diabetes is not fully understood. Macrophages and T cells may launch an initial immune reaction against the pancreatic islets of Langerhans, provoking inflammation and destructive insulitis. The information on the molecular mechanisms of the emergence of β cell injury is controversial and points to possibly important roles for the perforin–granzyme, Fas–Fas-ligand (FasL) and tumor-necrosis-factor-mediated apoptotic pathways. FasL has several unique features that make (...) it a potentially ideal immunomodulatory tool. Most important, FasL is selectively toxic to cytotoxic T cells and less harmful to regulatory T cells. This review discusses the intrinsic sensitivity of β cells to FasL-mediated apoptosis, the conditions that underlie this β cell sensitivity, and the feasibility of using FasL to arrest autoimmunity and prevent islet allograft rejection. In both the autoimmune and transplant settings, it is imperative to progress from the administration of nonspecific immunosuppressive therapy to the concept of β-cell-specific immunomodulation. FasL evolves as a prime candidate for antigen-specific immunomodulation. BioEssays 28: 211–222, 2006. © 2006 Wiley periodicals, Inc. (shrink)

A large body of evidence on the activity of regulatory T (Treg) cells was gathered during the last decade, and a similar number of reviews and opinion papers attempted to integrate the experimental findings. The abundant literature clearly delineates an exciting area of research but also underlines some major controversies. A linear cause–result interpretation of experimental maneuvers often ignores the fact that the activity of Treg cells is orchestrated with the effector T (Teff) cells within an intricate network of physiological (...) immune homeostasis. Every modulation of the activity of the effector (cytotoxic) immune system revolves to affect the activity of regulatory (suppressive) cells through elaborate feedback loops of negative and positive regulation. The lack of IL‐2 production by innate Treg cells makes this cytokine a prime coupler of the effector and suppressive mechanisms. Here we attempt to integrate evidence that delineates the involvement of IL‐2 in primary and secondary feedback loops that regulate the activity of suppressive cells within the elaborate network of physiological immune homeostasis.©2007 Wiley Periodicals, Inc BioEssays 30:875–888, 2008. © 2008 Wiley Periodicals, Inc. (shrink)