Objective. To investigate whether Treg cells can suppress osteoclast differentiation, and to define a new potential link between the immune system and the skeleton.Methods. Regulatory CD4؉,CD25؉,Foxp3؉ T cells were isolated and purified from the spleen and cocultured with CD11b؉ osteoclast precursor cells isolated from bone marrow. Osteoclastogenesis and bone erosion were assessed by tartrate-resistant acid phosphatase staining and pit resorption assay, respectively. In addition, Transwell experiments and cytokineblocking experiments were performed to define the mechanisms of interaction between Treg cells and osteoclasts.Results. CD4؉,CD25؉,Foxp3؉ T cells, but not CD4؉,CD25؊ T cells, dose dependently inhibited macrophage colony-stimulating factor-and RANKLdependent osteoclast formation. Pit formation was inhibited by up to 80% when Treg cells were added. The blockade of osteoclast formation was not based on the alteration of RANKL/osteoprotegerin balance but was essentially dependent on direct cell-cell contact via CTLA-4. Treg cell-mediated expression of transforming growth factor ␤, interleukin-4 (IL-4), and IL-10 contributed but was not essential to the inhibitory effect on osteoclastogenesis.Conclusion. These data show that CD4؉,CD25؉,Foxp3؉ Treg cells suppress osteoclast formation, provide a new link between the immune system and bone, and extend our knowledge on regulation of bone homeostasis by the immune system.

Siglec-G is a negative regulator of BCR-mediated signaling in B1a cells. This population of B cells is highly increased in Siglec-G–deficient mice, but the mechanism of this expansion is not known so far. In this study, we demonstrate that Siglecg−/− B1a cells show a lower level of spontaneous apoptosis and a prolonged life span. Mechanistically, the lower apoptosis could result from higher expression levels of the transcription factor NFATc1 in Siglec-G–deficient B1a cells. Interestingly, Siglecg−/− B1a cells display an altered BCR repertoire compared with wild-type B1a cells. As the BCR repertoire and the VDJ composition of Igs of Siglecg−/− B1a cells resembles more the Abs produced by adult bone marrow-derived B cells rather than canonical fetal liver-derived B1a cells, this suggest that the selection into the B1a cell population is altered in Siglec-G–deficient mice.

Understanding the signaling that governs the immunogenicity of human dendritic cells (DCs) is a prerequisite for improving DC-based therapeutic vaccination strategies, in which the ability of DCs to induce robust and lasting Ag-specific CTL responses is of critical importance. Cytokine-matured DCs are regularly used, but to induce memorytype CTLs, they require additional activation stimuli, such as CD4 + T-cell help or TLR activation. One common denominator of these stimuli is the activation of NF-κB. Here, we show that human monocyte-derived, cytokine cocktail-matured DCs transfected with constitutively active mutants of IκB kinases (caIKKs) by mRNA electroporation, further upregulated maturation markers, and secreted enhanced amounts of cytokines, including IL-12p70, which was produced for more than 48 h after transfection. Most importantly, cytotoxic T cells induced by caIKK-transfected DCs combined high CD27 expression, indicating a more memory-like phenotype, and a markedly enhanced secondary expandability with a high lytic capacity. In contrast, CTLs primed and expanded with unmodified cytokine cocktail-matured DCs did not maintain their proliferative capacity upon repetitive stimulations. We hypothesize that "designer" DCs expressing constitutively active IκB kinases will prove highly immunogenic also in vivo and possibly emerge as a new strategy to improve the clinical efficacy of therapeutic vaccinations against cancer and other chronic diseases.Keywords: DC immunotherapy r Immunogenicity r NF-kappaB r T-cell memory Additional supporting information may be found in the online version of this article at the publisher's web-site

TPL-2 expression is required for efficient polarization of naïve T cells to Th1 effector cells in vitro, and for Th1-mediated immune responses. In the present study, we investigated the potential role of TPL-2 in Th17 cells. TPL-2 was found to be dispensable for Th17 cell differentiation in vitro, and for the initial priming of Th17 cells in experimental autoimmune encephalomyelitis (EAE), a Th17 cell-mediated disease model for multiple sclerosis. Nevertheless, TPL-2-deficient mice were protected from EAE, which correlated with reduced immune cell infiltration, demyelination and axonal damage in the CNS. Adoptive transfer experiments demonstrated that there was no T cell-intrinsic function for TPL-2 in EAE, and that TPL-2 signaling was not required in radiation-sensitive hematopoietic cells. Rather, TPL-2 signaling in radiation-resistant stromal cells promoted the effector phase of the disease. Importantly, using a newly generated mouse strain expressing a kinase-inactive form of TPL-2, we demonstrated that stimulation of EAE was dependent on TPL-2’s catalytic activity, and not its adaptor function to stabilize the associated ubiquitin-binding protein ABIN-2. Our data therefore raise the possibility that small molecule inhibitors of TPL-2 may be beneficial in multiple sclerosis therapy.

The architectural chromosomal protein high-mobility group box 1 protein (HMGB1) acts as an alarmin when released from cells. It is involved in the pathogenesis of inflammatory and autoimmune diseases. HMGB1 can undergo post-translational modifications including oxidation. However, the mechanisms and functional relevance of HMGB1 oxidation are not yet understood. Increased concentrations of reactive oxygen species (ROS) have been reported during apoptosis and necrosis. Hence, we investigated the oxidative status of HMGB1 in dead cells. Immunoblot analyses under reducing and non-reducing conditions revealed that HMGB1 is oxidized in dead cells. Moreover, tagging of oxidized cysteine residues by a maleimide moiety linked to polyethylene glycol showed that HMGB1 passively released from primary and secondary necrotic cells was predominantly oxidized. Also HMGB1 in plasma of patients with systemic lupus was reversibly oxidized. In conclusion, HMGB1 undergoes reversible oxidative modifications at cysteine residues during cell death, which may modulate its biological properties.

BZ and SRL represent promising drugs with anti-humoral activity in the situation of an already established chronic humoral or mixed alloimmune response after renal transplantation.

BackgroundThe molecular and cellular pathways driving the pathogenesis of severe asthma are poorly defined. Tumor progression locus 2 (TPL-2) (COT, MAP3K8) kinase activates the MEK1/2-extracellular-signal regulated kinase 1/2 MAP kinase signaling pathway following Toll-like receptor, TNFR1, and IL-1R stimulation.ObjectiveTPL-2 has been widely described as a critical regulator of inflammation, and we sought to investigate the role of TPL-2 in house dust mite (HDM)-mediated allergic airway inflammation.MethodsA comparative analysis of wild-type and Map3k8−/− mice was conducted. Mixed bone marrow chimeras, conditional knockout mice, and adoptive transfer models were also used. Differential cell counts were performed on the bronchoalveolar lavage fluid, followed by histological analysis of lung sections. Flow cytometry and quantitative PCR was used to measure type 2 cytokines. ELISA was used to assess the production of IgE, type 2 cytokines, and Ccl24. RNA sequencing was used to characterize dendritic cell (DC) transcripts.ResultsTPL-2 deficiency led to exacerbated HDM-induced airway allergy, with increased airway and tissue eosinophilia, lung inflammation, and IL-4, IL-5, IL-13, and IgE production. Increased airway allergic responses in Map3k8−/− mice were not due to a cell-intrinsic role for TPL-2 in T cells, B cells, or LysM+ cells but due to a regulatory role for TPL-2 in DCs. TPL-2 inhibited Ccl24 expression in lung DCs, and blockade of Ccl24 prevented the exaggerated airway eosinophilia and lung inflammation in mice given HDM-pulsed Map3k8−/− DCs.ConclusionsTPL-2 regulates DC-derived Ccl24 production to prevent severe type 2 airway allergy in mice.

BackgroundNaturally occurring CD4+CD25+Foxp3+ regulatory T (Treg) cells develop in the thymus and represent a mature T cell subpopulation critically involved in maintaining peripheral tolerance. The differentiation of Treg cells in the thymus requires T cell receptor (TCR)/CD28 stimulation along with cytokine-promoted Foxp3 induction. TCR-mediated nuclear factor kappa B (NF-κB) activation seems to be involved in differentiation of Treg cells because deletion of components of the NF-κB signaling pathway, as well as of NF-κB transcription factors, leads to markedly decreased Treg cell numbers in thymus and periphery.Methodology/Principal FindingsTo investigate if Treg cell-intrinsic NF-κB activation is required for thymic development and peripheral homeostasis of Treg cells we used transgenic (Tg) mice with thymocyte-specific expression of a stable IκBα mutant to inhibit NF-κB activation solely within the T cell lineage. Here we show that Treg cell-intrinsic NF-κB activation is important for the generation of cytokine-responsive Foxp3− thymic Treg precursors and their further differentiation into mature Treg cells. Treg cell development could neither be completely rescued by the addition of exogenous Interleukin 2 (IL-2) nor by the presence of wild-type derived cells in adoptive transfer experiments. However, peripheral NF-κB activation appears to be required for IL-2 production by conventional T cells, thereby participating in Treg cell homeostasis. Moreover, pharmacological NF-κB inhibition via the IκB kinase β (IKKβ) inhibitor AS602868 led to markedly diminished thymic and peripheral Treg cell frequencies.Conclusion/SignificanceOur results indicate that Treg cell-intrinsic NF-κB activation is essential for thymic Treg cell differentiation, and further suggest pharmacological NF-κB inhibition as a potential therapeutic approach for manipulating this process.