These APC upon presenting the loaded antigen more readily tolerize Teff and/or induce aTreg (229C232). As opposed to ME0328 delivering a cargo to APC, nanoparticles have also been used as surrogate APC (233, 234). pancreases have also demonstrated islet infiltrates consisting of CD8+ T cells and macrophages, and to a lesser extent CD4+ T cells, and B cells (29, 31, 43C52). However, T1D pancreases have been reported that lack T cell infiltrates suggesting that the immunopathology of human T1D is heterogeneous (53, 54). The prevalence of T cell-independent subsets of T1D is unclear, and thought to be primarily associated with adult T1D onset. On the other hand, evidence indicates that the rapid and severe T1D that develops in children and adolescents is T cell-mediated (44). For instance, recent reports show that childhood onset is marked by a broader and more aggressive cell-specific T cell response compared to adult T1D (29, 31, 43C52, 55C57). Multiple cell autoantigens are recognized by human CD4+ and CD8+ T cells found in peripheral blood, as well as the islets of T1D subjects; many of which are also targeted in the NOD mouse diabetogenic response (e.g., insulin, GAD65, IGRP, and ZnT8) (4, 25, 28, 57). Pathogenic cell-specific CD4+ and CD8+ Teff in NOD and human T1D typically exhibit a type 1 or T helper 1 (Th1) phenotype marked by IFN production (47, 58, 59). IL-17-producing CD4+ Th17?cells have also been implicated in mediating cell destruction (60C62). Differentiation and expansion of pathogenic Teff are in part attributed to aberrant peripheral immunoregulation (63C68). An impaired ME0328 pool of thymic-derived FoxP3-expressing immunoregulatory T cells (Foxp3+Treg) has been linked to T1D (68C70). In general, Foxp3+Treg play an essential role in maintaining peripheral self-tolerance through cytokine and contact-dependent mechanisms of suppression (71). Decreased survival of islet-resident ME0328 Foxp3+Treg is thought to be a key factor in promoting the progression from benign to pathogenic insulitis in NOD mice (69). Failure to maintain islet Foxp3+Treg numbers in NOD mice is due to insufficient local levels of IL-2, a critical cytokine needed for Foxp3+Treg survival, fitness, and function (69, 72C74). FOXP3+Treg from T1D subjects have defective IL-2 receptor (R) signaling which limits fitness and function of FOXP3+Treg (66, 75). Additionally, production of the proinflammatory cytokine IL-21, which is critical for T1D development, can inhibit IL-2 expression by T cells which negatively impacts Foxp3+Treg ME0328 viability and function (76). Human T1D is also marked by deficiencies in non-FoxP3-expressing adaptive (a) Treg. For example, the frequency of cell-specific IL-10-secreting Tr1 cells is reduced in T1D versus healthy subjects (77C79). In both NOD and human T1D, Teff exhibit a reduced sensitivity to Treg-mediated suppression, which further permits expansion of the diabetogenic Teff pool (63, 64). Dysregulation among antigen-presenting cells (APC), such as DC, macrophages, and B cells, has also been reported to contribute to T1D (80C85). Although detection of autoantibodies is a key indicator of cell autoimmunity, B cells are thought to play a critical role in the development of T1D by functioning primarily as an APC (86C88). APC exhibiting proinflammatory properties also skew differentiation of na?ve cell-specific T cells toward pathogenic Teff, as well as amplify islet inflammation and cell destruction. For instance cytokines, such as IFN, TNF, and IL-1 secreted by islet APC are cytotoxic to cells (89). The culmination of the adaptive and innate effector immune response within the islets results in cell destruction/dysfunction and elevated blood glucose levels (Figure ?(Figure11). Open in a separate window Figure 1 The progression and treatment of cell autoimmunity. an expanded pool of Foxp3+ Treg in the islets and draining pancreatic lymph nodes (69, 164, 165). Similarly, low-dose IL-2 in combination with rapamycin in recent onset T1D patients increases the frequency of Foxp3+Treg in blood (166). However, these patients also exhibit an accelerated rate of cell loss (166), suggesting an enhanced pathogenic response, and highlighting the key problem of administering a cytokine with pleiotropic effects (167, 168). Different strategies are being developed to enhance the efficacy of Rabbit Polyclonal to Collagen I alpha2 (Cleaved-Gly1102) IL-2 (and other cytokines), while avoiding unwanted.