The thiol-disulfide oxidoreductase thioredoxin-1 (Trx1) is known to be secreted by leukocytes and to exhibit cytokine-like properties. Extracellular effects of Trx1 require a functional active site, suggesting a redox-based mechanism of action. However, specific cell surface proteins and pathways coupling extracellular Trx1 redox activity to cellular responses have not been identified so far. Using a mechanism-based kinetic trapping technique to identify disulfide exchange interactions on the intact surface of living lymphocytes, we found that Trx1 catalytically interacts with a single principal target protein. This target protein was identified as the tumor necrosis factor receptor superfamily member 8 (TNFRSF8/CD30). We demonstrate that the redox interaction is highly specific for both Trx1 and CD30 and that the redox state of CD30 determines its ability to engage the cognate ligand and transduce signals. Furthermore, we confirm that Trx1 affects CD30-dependent changes in lymphocyte effector function. Thus, we conclude that receptor–ligand signaling interactions can be selectively regulated by an extracellular redox catalyst.

The transient inactivation of protein phosphatases contributes to the efficiency and temporal control of kinase-dependent signal transduction. In particular, members of the protein tyrosine phosphatase family are known to undergo reversible oxidation of their active site cysteine. The thiol oxidation step requires activation of co-localized NADPH oxidases and is mediated by locally produced ROS, in particular H2O2. How oxidized phosphatases are returned to the reduced active state is less well studied. Both major thiol reductive systems, the thioredoxin and the glutathione systems, have been implicated in the reactivation of phosphatases. Here, we show that the protein tyrosine phosphatase PTP1B and the dual-specificity phosphatase PTEN are preferentially reactivated by the thioredoxin system. We show that inducible depletion of TRX1 slows down PTEN re-activation in intact living cells. Finally, using a mechanism-based trapping approach we demonstrate direct thiol disulfide exchange between the active sites of thioredoxin and either phosphatase. The application of thioredoxin trapping mutants represents a complementary approach to direct assays of PTP oxidation in elucidating the significance of redox regulation of PTP function in the control of cell signaling.

NOD.Cg-Prkdcscid IL-2rg tm1Wjl /SzJ (NSG) mice are a valuable tool for studying Graftversus-Host-Disease (GvHD) induced by human immune cells. We used a model of acute GvHD by transfer of human peripheral blood mononuclear cells (PBMCs) into NSG mice. The severity of GvHD was reflected by weight loss and was associated with engraftment of human cells and the expansion of leukocytes, particularly granulocytes and monocytes. Pre-treatment of PBMCs with the anti-human CD4 antibody MAX.16H5 IgG1 or IgG4 attenuated GvHD. The transplantation of 2 3 10 7 PBMCs without anti-human CD4 pre-treatment induced a severe GvHD (0% survival). In animals receiving 2 3 10 7 PBMCs pre-incubated with MAX.16H5 IgG1 or IgG4, GvHD development was reduced and survival was increased. Immune reconstitution was measured by flow cytometry and confirmed for human leukocytes (CD45), CD3 /CD41 T helper cells. Human B cells (CD19) and monocytes (CD14) could not be detected. Histopathological analysis (TUNEL assay) of the gut of recipient animals showed significantly less apoptotic crypt cells in animals receiving a MAX.16H5 IgG1 pre-incubated graft. These findings indicate that preincubation of an allogeneic graft with an anti-human CD4 antibody may decrease the frequency and severity of GvHD after hematopoietic stem cell transplantation (HSCT) and the need of conventional immunosuppressive drugs. Moreover, this approach most probably provides a safer HSCT that must be confirmed in appropriate clinical trials in the future. V C 2016 International Society for Advancement of Cytometry

Inflammatory bowel diseases (IBD) are chronic relapsing disorders of the gastrointestinal tract. Several mouse models for IBD are available, but the acute dextran sulfate sodium (DSS)-induced colitis model is mostly used for preclinical studies. However, this model lacks chronicity and often leads to significant loss of mice. The aim of this study was to establish a refined and translationally relevant model of DSS chronic colitis in BALB/c mice. In the first part, we compared several standard therapeutic (ST) treatments for IBD in the acute DSS colitis model to identify the optimal treatment control for a DSS colitis model as compared to literature data. In the second part, we tested the two most effective ST treatments in a refined model of chronic DSS colitis. Cyclosporine A (CsA) and 6-thioguanine (6-TG) caused considerable reduction of clinical scores in acute DSS colitis. The clinical outcome was confirmed by the results for colon length and by histopathological evaluation. Moreover, CsA and 6-TG considerably reduced mRNA expression of several pro-inflammatory cytokines in spleen and colon. Both compounds also showed a substantial therapeutic effect in the refined model of chronic DSS colitis with regard to clinical scores and histopathology as well as the expression of inflammatory markers. The refined model of chronic DSS colitis reflects important features of IBD and is well suited to test potential IBD therapeutics.