Transforming growth factor receptor III (Betaglycan) regulates the generation of pathogenic Th17 cells in EAE

The transforming growth factor receptor III (TβRIII) is commonly recognized as a co-receptor that promotes the binding of TGFβ family ligands to type I and type II receptors. Within the immune system, TβRIII regulates T cell development in the thymus and is differentially expressed through activation; however, its function in mature T cells is unclear. To begin addressing this question, we developed a conditional knock-out mouse with restricted TβRIII deletion in mature T cells, necessary because genomic deletion of TβRIII results in perinatal mortality. We determined that TβRIII null mice developed more severe autoimmune central nervous neuroinflammatory disease after immunization with myelin oligodendrocyte peptide (MOG_35-55) than wild-type littermates. The increase in disease severity in TβRIII null mice was associated with expanded numbers of CNS infiltrating IFNγ⁺ CD4⁺ T cells and cells that co-express both IFNγ and IL-17 (IFNγ⁺/IL-17⁺), but not IL-17 alone expressing CD4 T cells compared to Tgfbr3^fl/fl wild-type controls. This led us to speculate that TβRIII may be involved in regulating conversion of encephalitogenic Th17 to Th1. To directly address this, we generated encephalitogenic Th17 and Th1 cells from wild type and TβRIII null mice for passive transfer of EAE into naïve mice. Remarkably, Th17 encephalitogenic T cells from TβRIII null induced EAE of much greater severity and earlier in onset than those from wild-type mice. The severity of EAE induced by encephalitogenic wild-type and Tgfbr3^fl/fl.dLcKCre Th1 cells were similar. Moreover, in vitro restimulation of in vivo primed Tgfbr3^fl/fl.dLcKCre T cells, under Th17 but not Th1 polarizing conditions, resulted in a significant increase of IFNγ⁺ T cells. Altogether, our data indicate that TβRIII is a coreceptor that functions as a key checkpoint in controlling the pathogenicity of autoreactive T cells in neuroinflammation probably through regulating plasticity of Th17 T cells into pathogenic Th1 cells. Importantly, this is the first demonstration that TβRIII has an intrinsic role in T cells.

TCR signaling strength dependent regulation of T cell proliferation, survival and Th differentiation by TGF-βR3 (betaglycn)

TGF-β receptor 3 (TGFβ-R3) or betaglycan, promotes high-affinity binding of TGF-β (1, 2 and 3) to TGFβ-R1 and TGFβ-R2. Additionally, it is also a receptor for bone morphogenic proteins (BMPs) and inhibins. Although TGFβ-R3 is widely expressed on cells of both the innate and adaptive immune system, embryonic lethality of Tgfbr3 knock-outs has been a limitation to obtain a mechanistic understanding of its function in immune response. We therefore developed a Tgfbr3f/fmouse and bred with the CD4Cre mouse. Remarkably, thymic inactivation of TGFβ-R3 had no significant effect on T cell development nor did the mice develop spontaneous autoimmunity. This led us infer that TGFβ-R3 is unlikely to have a necessary function in enhancing TGF-β signaling from TGFβ-R1/R2. To interrogate the function of TGFβ-R3 in mature T cells, we generated OT2.Tgfbr3f/f.dLckCre mice and control littermates. We observed that TGFβR-R3 deficient T cells exhibited greater early proliferation than controls, however, their ability to persist was compromised. This effect of TGFβ-R3 was more pronounced with increasing concentrations of OVA323–339 peptide. The differentiation of TGFβ-R3 deficient to Th1 cells under polarizing conditions was significantly reduced in proportion and absolute numbers compared to Tgfbr3f/f T cells and this correlated with lower Tbet expression. Encephalitogenic Th1 cells generated from Tgfbr3f/f.dLckCre mice induced significantly less severe EAE in naïve mice than that from Tgfbr3f/f littermates. Overall or data reveal a novel role for TGFβR3 in promoting of Th1 differentiation and regulation of regulation T-cell activation and survival.

TGF-β receptor 3 (betaglycan) regulates Th1 differentiation and T dependent B cell responses

TGFβR3, also known as betaglycan, is a co-receptor for the TGFβ receptor and is predicted to have an important function in promoting high affinity binding of TGF-β to TGFβR1 or TGFβR2. TGFβR3 also binds inhibins with high affinity and antagonizes activin dependent activation of SMADs a function independent of TGFβR1/TGFβR2 signaling. Contrary to TGFβR1 and TGFβR2, our knowledge on the role of TGFβR3 in the immune system is very sparse. Its biology has been elusive because the knock-out of Tgfbr3 exhibit embryonic lethality. We developed the first Tgfbr3f/f mouse in which Cre mediated deletion of Tgfbr3 is very efficient. We found that deletion of TGFβR3 in thymic T cells (Tgfbr3f/f.CD4Cre) had no effect on CD4 or CD8 double positive (DP) or single positive (SP) T cell populations or peripheral T cell populations. Treg numbers in the thymus and periphery were unaltered and the mice did not develop spontaneous autoimmunity as observed when Tgfbr2 is deleted during thymic development. These observations indicated to us that TGFβR3 likely had a function independent of “classical” TGF-β signaling through TGFβR1/2 receptors. To test for this possibility we generated Tgfbr3f/f.dLckCre) mice in which is Tgfbr3 is selectively deleted in mature CD4 and CD8 T cells. We found that T dependent Ab responses, particularly of the IgG2c subclass, was greatly enhanced in mice with T-cell restricted loss of TGFβR3. We further determined that the differentiation of naïve CD4 T cells to IFN-γ expressing Th1 cells under polarizing and non-polarizing conditions was enhanced when TGFβR3 was deficient. These and other data indicate that regulation of Th1 differentiation by TGFβR3 is novel and independent of TGF-β signaling.

TREM-like transcript 2 is stored in human neutrophil primary granules and is up-regulated in response to inflammatory mediators

The triggering receptor expressed on myeloid cell locus encodes a family of receptors that is emerging as an important class of molecules involved in modulating the innate immune response and inflammation. Of the 4 conserved members, including triggering receptor expressed on myeloid cells 1 and 2 and triggering receptor expressed on myeloid cell-like transcripts 1 and 2, relatively little is known about triggering receptor expressed on myeloid cell-like transcript 2 expression and function, particularly in humans. In this study, experiments were performed to determine if triggering receptor expressed on myeloid cell-like transcript 2 expression is conserved between mouse and human, demonstrating that human triggering receptor expressed on myeloid cell-like transcript 2 is expressed on cells of the lymphoid, as well as myeloid/granuloid lineages, similar to murine triggering receptor expressed on myeloid cell-like transcript 2. Consistent with studies in the mouse, triggering receptor expressed on myeloid cell-like transcript 2 expression is up-regulated in response to inflammatory mediators on human neutrophils. Importantly, it was shown that triggering receptor expressed on myeloid cell-like transcript 2, in resting human neutrophils, is predominantly localized to intracellular vesicles, including secretory vesicles and primary granules; with the majority of triggering receptor expressed on myeloid cell-like transcript 2 stored in primary granules. In contrast to other primary granule proteins, triggering receptor expressed on myeloid cell-like transcript 2 is not expelled on neutrophil extracellular traps but is retained in the plasma membrane following primary granule exocytosis. In summary, these findings establish that triggering receptor expressed on myeloid cell-like transcript 2 expression is conserved between species and is likely to be important in regulating neutrophil antimicrobial function following primary granule exocytosis.

Inhibition of System Xc(-) Transporter Attenuates Autoimmune Inflammatory Demyelination

T cell infiltration into the CNS is a significant underlying pathogenesis in autoimmune inflammatory demyelinating diseases. Several lines of evidence suggest that glutamate dysregulation in the CNS is an important consequence of immune cell infiltration in neuroinflammatory demyelinating diseases; yet, the causal link between inflammation and glutamate dysregulation is not well understood. A major source of glutamate release during oxidative stress is the system Xc(-) transporter; however, this mechanism has not been tested in animal models of autoimmune inflammatory demyelination. We find that pharmacological and genetic inhibition of system Xc(-) attenuates chronic and relapsing-remitting experimental autoimmune encephalomyelitis (EAE). Remarkably, pharmacological blockade of system Xc(-) 7 d after induction of EAE attenuated T cell infiltration into the CNS, but not T cell activation in the periphery. Mice harboring a Slc7a11 (xCT) mutation that inactivated system Xc(-) were resistant to EAE, corroborating a central role for system Xc(-) in mediating immune cell infiltration. We next examined the role of the system Xc(-) transporter in the CNS after immune cell infiltration. Pharmacological inhibitors of the system Xc(-) transporter administered during the first relapse in a SJL animal model of relapsing-remitting EAE abrogated clinical disease, inflammation, and myelin loss. Primary coculture studies demonstrate that myelin-specific CD4(+) Th1 cells provoke microglia to release glutamate via the system Xc(-) transporter, causing excitotoxic death to mature myelin-producing oligodendrocytes. Taken together, these studies support a novel role for the system Xc(-) transporter in mediating T cell infiltration into the CNS as well as promoting myelin destruction after immune cell infiltration in EAE.

CD5 enhances Th17-cell differentiation by regulating IFN-γ response and RORγt localization

Mechanisms that modulate the generation of Th17 cells are incompletely understood. We report that the activation of casein kinase 2 (CK2) by CD5 is essential for the efficient generation of Th17 cells in vitro and in vivo. In our study, the CD5-CK2 signaling pathway enhanced TCR-induced activation of AKT and promoted the differentiation of Th17 cells by two independent mechanisms: inhibition of glycogen synthase kinase 3 (GSK3) and activation of mTOR. Genetic ablation of the CD5-CK2 signaling pathway attenuated TCR-induced AKT activation and consequently increased activity of GSK3 in Th17 cells. This resulted in increased sensitivity of Th17 cells to IFN-γ-mediated inhibition. In the absence of CD5-CK2 signaling, we observed decreased activity of S6K and attenuated nuclear translocation of RORγt (ROR is retinoic acid receptor related orphan receptor). These results reveal a novel and essential function of the CD5-CK2 signaling pathway and GSK3-IFN-γ axis in regulating Th-cell differentiation and provide a possible means to dampen Th17-type responses in autoimmune diseases.

CD5-dependent CK2 activation pathway regulates threshold for T cell anergy

CD5 activates casein kinase 2 (CK2), a serine/threonine kinase that constitutively associates with the CK2-binding domain at the end of its cytoplasmic tail. To determine the physiological significance of CD5-dependent CK2 activation in T cells, we generated a knock-in mouse that expresses a CD5 protein containing a microdeletion with selective inability to interact with CK2 (CD5ΔCK2BD). The levels of CD5 on developing and mature T cell populations from CD5ΔCK2BD mice and CD5 wild-type (WT) mice were similar. The thymus of CD5ΔCK2BD mice contained fewer double-positive thymocytes than did that of both CD5WT and CD5 knockout (KO) mice, although the numbers of all other immature and mature T cell populations were unaltered. CD5ΔCK2BD T cells hypoproliferated and exhibited enhanced activation-induced cell death when stimulated with anti-CD3 or cognate peptide in comparison with CD5WT T cells. We also found that functional CD5-dependent CK2 signaling was necessary for efficient differentiation of naive CD4+ T cells into Th2 and Th17 cells, but not Th1 cells. We previously showed that experimental autoimmune encephalomyelitis (EAE) in CD5KO mice was less severe and delayed in onset than in CD5WT mice. Remarkably, CD5ΔCK2BD mice recapitulated both EAE severity and disease onset of CD5KO mice. Increasing the immunization dose of myelin oligodendrocyte glycoprotein 35-55 peptide, a model that mimics high-dose tolerance, led to decreased severity of EAE in CD5WT mice but not in CD5KO or CD5ΔCK2BD mice. This property was recapitulated in in vitro restimulation assays. These results demonstrate that CD5-CK2 signaling sets the threshold for T cell responsiveness and is necessary for efficient generation of Th2 and Th17 cells.

Detection of IgG and IgM in sera from canines with blastomycosis using eight blastomyces dermatitidis yeast phase lysate antigens

The objective of this study was to compare the efficacy of eight Blastomyces dermatitidis yeast phase lysate antigens (T-58: dog, Tennessee; T-27: polar bear, Tennessee; ERC-2: dog, Wisconsin; B5894: human, Minnesota; SOIL: soil, Canada; B5896: human, Minnesota; 48089: human, Zaire; 48938: bat, India) in the detection of the immunoglobulins IgG and IgM in serum specimens from canines with blastomycosis. An indirect enzyme-linked immunosorbent assay (ELISA, peroxidase system) was used to analyze sera collected during four different intervals post-infection. The yeast lysate antigen 48938 was a reactive antigen for the detection of both IgG (mean absorbance value range: 1.198-2.934) and IgM (mean absorbance value range: 0.505-0.845). For the same sera, antigen T-27 was also effective in the detection of IgG (mean absorbance value range: 0.904-3.356) and antigen 48089 was useful for the detection of IgM (mean absorbance value range: 0.377-0.554). The yeast lysate antigen B5894 proved to be a poor antigen for the detection of both IgG and IgM (mean absorbance value ranges: 0.310-0.744 for IgG, 0.025-0.069 for IgM). Inherent variations in yeast lysate antigens such as these may be utilized to develop improved immunoassay procedures for the specific detection of IgG or IgM in cases of blastomycosis.