The process of human islet isolation triggers a cascade of stressful events in the islets of Langerhans involving activation of apoptosis and necrosis and the production of proinflammatory molecules that negatively influence islet yield and function and may produce detrimental effects after islet transplantation. In this study, we showed that activation of nuclear factor-B (NF-B) and poly(ADP-ribose) polymerase (PARP), two of the major pathways responsible for cellular responses to stress, already occurs in pancreatic cells during the isolation procedure. NF-B؊dependent reactions, such as production and release of interleukin-6 and -8 and macrophage chemoattractant protein 1, were observed days after the isolation procedure in isolated purified islets. Under culture conditions specially designed to mimic isolation stress, islet proinflammatory responses were even more pronounced and correlated with higher islet cell loss and impaired secretory function. Here we present novel evidence that early interventions aimed at reducing oxidative stress of pancreatic cells and islets through the use of the catalytic antioxidant probe AEOL10150 (manganese [III] 5,10,15,20-tetrakis [1,3,-diethyl-2imidazoyl] manganese-porphyrin pentachloride [TDE-2,5-IP]) effectively reduces NF-B binding to DNA, the release of cytokines and chemokines, and PARP activation in islet cells, resulting in higher survival and better insulin release. These findings support the concept that the isolation process predisposes islets to subsequent damage and functional impairment. Blocking oxidative stress can be beneficial in reducing islet vulnerability and can potentially have a significant impact on transplantation outcome.

No abstract

Successful Ag activation of naive T helper cells requires at least two signals consisting of TCR and CD28 on the T cell interacting with MHC II and CD80/CD86, respectively, on APCs. Recent evidence demonstrates that a third signal consisting of proinflammatory cytokines and reactive oxygen species (ROS) produced by the innate immune response is important in arming the adaptive immune response. In an effort to curtail the generation of an Ag-specific T cell response, we targeted the synthesis of innate immune response signals to generate Ag-specific hyporesponsiveness. We have reported that modulation of redox balance with a catalytic antioxidant effectively inhibited the generation of third signal components from the innate immune response (TNF-α, IL-1β, ROS). In this study, we demonstrate that innate immune-derived signals are necessary for adaptive immune effector function and disruption of these signals with in vivo CA treatment conferred Ag-specific hyporesponsiveness in BALB/c, NOD, DO11.10, and BDC-2.5 mice after immunization. Modulating redox balance led to decreased Ag-specific T cell proliferation and IFN-γ synthesis by diminishing ROS production in the APC, which affected TNF-α levels produced by CD4+ T cells and impairing effector function. These results demonstrate that altering redox status can be effective in T cell-mediated diseases such as autoimmune diabetes to generate Ag-specific immunosuppression because it inhibits the third signal necessary for CD4+ T cells to transition from expansion to effector function.

Interleukin (IL)-1␤ and IL-18 are two cytokines associated with the immunopathogenesis of diabetes in NOD mice. Both of these cytokines are cleaved by caspase-1 to their biologically active forms. IL-1 is a proinflammatory cytokine linked to ␤-cell damage, and IL-18 stimulates production of interferon (IFN)␥ in synergy with IL-12. To examine the effects produced by caspase-1 deficiency on diabetes development in NOD/Lt mice, a disrupted Casp1 gene was introduced by a speed congenic technique. Casp1 ؊/؊ bone marrow-derived macrophages stimulated with lipopolysaccharide produced no detectable IL-18, fourfold lower IL-1␤, and 20 -30% less IL-1␣ than macrophages from wild-type Casp1 ؉/؉ or Casp1 ؉/؊ controls. Unexpectedly, despite reduced IL-1 and IL-18, there was no change in the rate of diabetes or in total incidence as compared with that in wild-type NOD mice. IL-1 reportedly makes an important pathological contribution in the multidose streptozotocin model of diabetes; however, there was no difference in sensitivity to streptozotocin between NOD mice and NOD.Casp1 ؊/؊ mice at 40 mg/kg body wt or at 25 mg/kg body wt dosage levels. These findings show that caspase-1 processing of IL-1␤ and IL-18 is not absolutely required for mediation of spontaneous or chemically induced diabetes pathogenesis in the NOD mouse.

The ability to generate, maintain, and use cloned lines of T cells reactive for self-antigens has opened up a new avenue of investigation for researchers. These T-cell clones allow the rapid induction of tissue-specific autoimmunity with the intent of dissecting the contribution of the different cell types involved. T cells from the diabetes-prone nonobese diabetic mouse are proving to be a vital asset for understanding the T-cell-mediated pathogenesis that leads to overt beta-cell destruction. T-cell clone adoptive transfer protocols have been developed for use in immunodeficient strains, thus reducing the complexity of mechanism of disease initiation. Furthermore, these T-cell clones have been used to derive T-cell receptor transgenic (TCR-Tg) animals carrying only self-reactive T cells. The use of these TCR-Tg animals to study pathogenesis has also evolved from the ability to generate, maintain, and use T-cell cloned lines. This chapter focuses on primary culture for the generation of T-cell lines and clones, their long-term maintenance, and their use in disease transfer for studying the pathogenesis of end-organ autoimmunity.

No abstract