Disruption of innate-mediated proinflammatory cytokine and reactive oxygen species third signal leads to antigen-specific hyporesponsiveness.

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-alpha, IL-1beta, 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-gamma synthesis by diminishing ROS production in the APC, which affected TNF-alpha 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.

Generation, maintenance, and adoptive transfer of diabetogenic T-cell lines/clones from the nonobese diabetic 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.

Mechanistic analysis of the immunomodulatory effects of a catalytic antioxidant on antigen-presenting cells: implication for their use in targeting oxidation-reduction reactions in innate immunity.

Reactive oxygen species (ROS) have an indispensable role in controlling the growth of pathogens. Recent evidence also suggests that they can function as second messengers and modulators of the immune system. The identification of many redox-sensitive signal transduction pathways that are necessary for initiating the innate proinflammatory immune response suggests that modulation of these oxidation-reduction reactions may provide a means of therapeutic benefit for controlling inflammatory-mediated diseases. In order to test this hypothesis we employed two catalytic antioxidants (AEOL 10113 and 10150) for the determination of the role of oxidation-reduction reactions in innate immune system activation. Catalytic antioxidants prevented the initiation of the innate immune response in LPS-stimulated macrophages as evidenced by the suppression of proinflammatory cytokines (TNF-alpha, IL-1beta) and ROS (NO2- and O2-). The suppression of proinflammatory cytokine and ROS production correlated with the inhibition of NF-kappaB DNA binding, without any effects on the mitogen-activated protein kinase signaling pathway. Catalytic antioxidants prevented NF-kappaB from binding DNA by an oxidation mechanism that was reversible with the addition of DTT. Although the primary use of these agents was to reduce and scavenge ROS, surprisingly, we also observed the ability of these compounds to exhibit oxidoreductase activity and oxidize redox-sensitive transcription factors such as NF-kappaB. Catalytic antioxidants exhibit antioxidant and pro-oxidant activities and our data further demonstrate the importance of redox balance for the initiation of proinflammation. The coupling of the innate with the adaptive immune response is dependent on TNF-alpha, IL-1beta, NO2-, and O2- generation; therefore, agents like catalytic antioxidants that decrease proinflammatory cytokines and ROS may provide protective effects in diseases in which chronic inflammation plays a pathogenic role.

Caspase-1 is not required for type 1 diabetes in the NOD mouse.

Interleukin (IL)-1 beta 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 beta-cell damage, and IL-18 stimulates production of interferon (IFN)gamma 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 beta, and 20-30% less IL-1 alpha 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 beta and IL-18 is not absolutely required for mediation of spontaneous or chemically induced diabetes pathogenesis in the NOD mouse.