NIK-dependent RelB activation defines a unique signaling pathway for the development of V alpha 14i NKT cells

A defect in RelB, a member of the Rel/nuclear factor (NF)-kappa B family of transcription factors, affects antigen presenting cells and the formation of lymphoid organs, but its role in T lymphocyte differentiation is not well characterized. Here, we show that RelB deficiency in mice leads to a selective decrease of NKT cells. RelB must be expressed in an irradiation-resistant host cell that can be CD1d negative, indicating that the RelB expressing cell does not contribute directly to the positive selection of CD1d-dependent NKT cells. Like RelB-deficient mice, aly/aly mice with a mutation for the NF-kappa B-inducing kinase (NIK), have reduced NKT cell numbers. An analysis of NK1.1 and CD44 expression on NKT cells in the thymus of aly/aly mice reveals a late block in development. In vitro, we show that NIK is necessary for RelB activation upon triggering of surface receptors. This link between NIK and RelB was further demonstrated in vivo by analyzing RelB+/- x aly/+ compound heterozygous mice. After stimulation with alpha-GalCer, an antigen recognized by NKT cells, these compound heterozygotes had reduced responses compared with either RelB+/- or aly/+ mice. These data illustrate the complex interplay between hemopoietic and nonhemopoietic cell types for the development of NKT cells, and they demonstrate the unique requirement of NKT cells for a signaling pathway mediated by NIK activation of RelB in a thymic stromal cell

TLR4 and RAGE conversely mediate pro-inflammatory S100A8/9-mediated inhibition of proliferation-linked signaling in myeloproliferative neoplasms

Purpose Previously, the family of S 100A proteins has been found to be associated with inflammation and myelopoiesis and to be able to induce or support myeloproliferation during chronic inflammation. Here, we studied the inflammatory myeloid-related proteins Si 00A4, S 100A8, S 100A9 and S100Al2 in myeloproliferative neoplasms (MPNs) in order to assess the involvement of chronic inflammation in the pathogenesis of MPN. Methods We analyzed the S100A4, S100A8, S100A9 and S100Al2 mRNA and protein levels in the bone marrow and circulation of 140 patients with MPN and 15 healthy controls using Western blotting, microarray-based mRNA expression profiling and ELISA assays, respectively. In addition we performed functional studies on the proliferation-related AKT and ERK1/2 signaling pathways in MPN-derived granulocytes using Western blotting and proteomic analyses. Results We found that the S100A mRNA levels were increased in MPN patient-derived circulatory CD34(+ )cells, and that their protein expression levels were also augmented in their granulocytes and bone marrow stroma cells, depending on the JAK2V617F mutation allele burden. We also found that calreticulin (CALR) mutations were related to reduced S100A8 plasma levels in primary myelofibrosis (PMF). The S100A8 plasma levels were found to be increased in MPN, the S100A9 plasma levels in PMF and essential thrombocythemia (ET), and the S100A12 plasma levels in polycythemia vera (PV). These 5100A plasma levels showed a positive correlation with the systemic inflammation marker IL-8, as well as with the numbers of leukocytes and thrombocytes, depending on the JAK2V617F mutation status. Additionally, we found that heterodimeric S100A8/9 can inhibit the AKT pathway in MPN-derived granulocytes mediated by the Toll-like receptor 4 (TLR4), depending on the CALR mutation status. Conversely, we found that blocking of the receptor for advanced glycation end products (RAGE) increased the S100A8/9-mediated inhibition of AKT signaling in the MPN-derived granulocytes. Moreover, we found that heterodimeric S100A8/9 generally induced TLR4-mediated ERK1/2 dephosphorylation proportionally to the JAK2V617F mutation allele burden. TLR4/RAGE blocking prevented the S100A8/9-mediated inhibition of ERK1/2 phosphorylation in PV. Conclusions From our data we conclude that the 5100A8 and S100A9 granulocyte and plasma levels are increased in MPN patients, along with inflammation markers, depending on their JAK2V617F mutation allele burden. We also found that SIO0A8/9-mediated inhibition of the proliferation-related AKT and ERK1/2 signaling pathways can be decreased by CALR mutationdependent TLR4 blocking and increased by RAGE inhibition in MPN

Mesenteric B cells centrally inhibit CD4(+) T cell colitis through interaction with regulatory T cell subsets

Inflammatory bowel disease reflects an aberrant mucosal CD4(+) T cell response to commensal enteric bacteria. In addition to regulatory T cell subsets, recent studies have revealed a protective role of B cells in murine CD4(+) T cell colitis, but the relationship of their action to T cell immunoregulation is unknown. Here we report that mesenteric lymph node (MLN) B cells protect mice from colitis induced by Gαi2(–/–) CD4(+) T cells. Protection required the transfer of both B cells and CD8α(+) T cells; neither cell type alone was sufficient to inhibit CD4(+) T cell-mediated colitis. Similar results were also observed in colitis induced by CD4(+)CD45RB(hi) T cells. Immunoregulation was associated with localization of B cells and expansion of CD4(–)CD8(–) CD3(+)NK1.1(+) T cells in the secondary lymphoid compartment, as well as expansion of CD4(+)CD8α(+) T cells in the intestinal intraepithelial compartment. MLN B cells from Gαi2(–/–) mice were deficient in a phenotypic subset and failed to provide cotransfer colitis protection. These findings indicate that protective action of B cells is a selective trait of MLN B cells acquired through a Gαi2-dependent developmental process and link B cells with the formation of regulatory T cells associated with mucosal immune homeostasis