An IFN-γ-IL-18 signaling loop accelerates memory CD8+ T cell proliferation

Rapid proliferation is one of the important features of memory CD8+ T cells, ensuring rapid clearance of reinfection. Although several cytokines such as IL-15 and IL-7 regulate relatively slow homeostatic proliferation of memory T cells during the maintenance phase, it is unknown how memory T cells can proliferate more quickly than naïve T cells upon antigen stimulation. To examine antigen-specific CD8+ T cell proliferation in recall responses in vivo, we targeted a model antigen, ovalbumin(OVA), to DEC-205+ dendritic cells (DCs) with a CD40 maturation stimulus. This led to the induction of functional memory CD8+ T cells, which showed rapid proliferation and multiple cytokine production (IFN-γ, IL-2, TNF-α) during the secondary challenge to DC-targeted antigen. Upon antigen-presentation, IL-18, an IFN-γ-inducing factor, accumulated at the DC:T cell synapse. Surprisingly, IFN-γ receptors were required to augment IL-18 production from DCs. Mice genetically deficient for IL-18 or IFN-γ-receptor 1 also showed delayed expansion of memory CD8+ T cells in vivo. These results indicate that a positive regulatory loop involving IFN-γ and IL-18 signaling contributes to the accelerated memory CD8+ T cell proliferation during a recall response to antigen presented by DCs

A new triggering receptor expressed on myeloid cells (Trem) family member, Trem-like 4, binds to dead cells and is a DNAX activation protein 12-linked marker for subsets of mouse macrophages and dendritic cells

Dendritic cells (DCs) are professional APCs that can control immune responses against self and altered self, typically foreign, determinants. DCs can be divided into several subsets, including CD8α+ and CD8α- DCs. These subsets possess specific functions. For example, mouse splenic CD8α+, but not CD8α- DCs selectively take up dying cells and cross-present cell-associated Ags to naive T cells. In this study, we identified genes that were more expressed in CD8α+ than CD8α- DCs by microarray analysis. Only one of these genes, when the extracellular domains were linked to human IgG Fc domain, could bind to late apoptotic or necrotic cells. This gene was a new member of the triggering receptor expressed on myeloid cells (Trem) family, Trem-like 4 (Treml4). Treml4 mRNA and protein, the latter detected with a new mAb, were predominantly expressed in spleen. Treml4, like other Trem family members, could associate with the adaptor molecule DNAX activation protein 12 kDa, but neither DNAX activation protein 10 kDa nor FcRγ. Consistent with the microarray data, we confirmed that Treml4 protein was more expressed on CD8α+ than CD8α- DCs, and we also found that Treml4 was expressed at high levels on splenic macrophages in spleen, particularly red pulp and marginal metallophilic macrophages. In addition, Treml4 expression on DCs was not changed after maturation induced by TLR ligands. Thus, Treml4 is a new Trem family molecule that is abundantly expressed on CD8α+ DCs and subsets of splenic resident macrophages, and can recognize dead cells by different types of phagocytes in spleen

Glycolipid α-C-galactosylceramide is a distinct inducer of dendritic cell function during innate and adaptive immune responses of mice

α-Galactosylceramide (α-GalCer) is the prototype compound for studying the presentation of glycolipids on CD1d molecules to natural killer T (NKT) lymphocytes. A single i.v. dose of glycolipid triggers a cascade of events involving the production of several cytokines over the course of a day, a short-lived activation of NKT and natural killer (NK) cells, and a more prolonged adaptive T cell immune response if certain antigens are given together with α-GalCer. We find that a recently described analogue, α-C-galactosylceramide (α-C-GalCer), more potently induces these innate and adaptive immune responses in mice. α-C-GalCer acts as a more effective trigger for IL-12 and IFN-γ production, although it minimally elicits IL-4 and TNF-α release into the serum. Also, α-C-GalCer better mobilizes NKT and natural killer cells to resist B16 melanoma. To help understand these effects, we find that α-C-GalCer binds more stably to dendritic cells than α-GalCer and that dendritic cells loaded with α-C-GalCer induce larger and more long lasting NKT cell responses in vivo. When glycolipid is targeted to dendritic cells in spleen together with antigens in dying cells, such as irradiated tumor cells, α-C-GalCer is active as an adjuvant for T cell-mediated immunity at lower doses, just 20 ng per mouse, where it is also able to up-regulate the required CD40L costimulatory molecule on NKT cells. Therefore, α-C-GalCer represents a glycolipid that binds more stably to dendritic cells and acts as a more effective link between innate and adaptive immunity in vivo

Treml4, an Ig superfamily member, mediates presentation of several antigens to T cells in vivo, including protective immunity to HER2 protein

Members of the triggering expressed on myeloid cells (Trem) receptor family fine-tune inflammatory responses. We previously identified one of these receptors, called Treml4, expressed mainly in the spleen, as well as at high levels by CD8α + dendritic cells and macrophages. Like other Trem family members, Treml4 has an Ig-like extracellular domain and a short cytoplasmic tail that associates with the adaptor DAP12. To follow up on our initial results that Treml4-Fc fusion proteins bind necrotic cells, we generated a knockout mouse to assess the role of Treml4 in the uptake and presentation of dying cells in vivo. Loss of Treml4 expression did not impair uptake of dying cells by CD8α + dendritic cells or cross-presentation of cell-associated Ag to CD8 +T cells, suggesting overlapping function between Treml4 and other receptors in vivo. To further investigate Treml4 function, we took advantage of a newly generated mAb against Treml4 and engineered its H chain to express three different Ags (i.e., OVA, HIV GAGp24, and the extracellular domain of the breast cancer protein HER2). OVA directed to Treml4 was efficiently presented to CD8 + and CD4 + T cells in vivo. Anti-Treml4-GAGp24 mAbs, given along with a maturation stimulus, induced Th1 Ag-specific responses that were not observed in Treml4 knockout mice. Also, HER2 targeting using anti-Treml4 mAbs elicited combined CD4 + and CD8 + T cell immunity, and both T cells participated in resistance to a transplantable tumor. Therefore, Treml4 participates in Ag presentation in vivo, and targeting Ags with anti-Treml4 Abs enhances immunization of otherwise naive mice

Mammal fauna in the Higashi-Hiroshima Campus, Hiroshima University

2017年5月から翌年5月にかけて，東広島キャンパス内の哺乳類相の把握を目的とした調査を実施した。構内の8地点に自動撮影装置を設置し，並行してコウモリ類の音声調査および痕跡の記録を行った。その結果，4目12種の哺乳類の生息が確認され，いずれもキャンパスでの広範な分布が示された。その一方で，調査中にはイエネコが小動物を捕食する様子が複数回撮影され，これを含む4種の移入哺乳類による在来生物への影響が懸念された

Interferon-α and Interleukin-12 Are Induced Differentially by Toll-like Receptor 7 Ligands in Human Blood Dendritic Cell Subsets

Dendritic cells (DCs) play a crucial role in the immune responses against infections by sensing microbial invasion through toll-like receptors (TLRs). In humans, two distinct DC subsets, CD11c− plasmacytoid DCs (PDCs) and CD11c+ myeloid DCs (MDCs), have been identified and can respond to different TLR ligands, depending on the differential expression of cognate TLRs. In this study, we have examined the effect of TLR-7 ligands on human DC subsets. Both subsets expressed TLR-7 and could respond to TLR-7 ligands, which enhanced the survival of the subsets and upregulated the surface expression of costimulatory molecules such as CD40, CD80, and CD86. However, the cytokine induction pattern was distinct in that PDCs and MDCs produced interferon (IFN)-α and interleukin (IL)-12, respectively. In response to TLR-7 ligands, the Th1 cell supporting ability of both DC subsets was enhanced, depending on the cytokines the respective subsets produced. This study demonstrates that TLR-7 exerts its biological effect in a DC subset-specific manner

The Roles of Two IκB Kinase-related Kinases in Lipopolysaccharide and Double Stranded RNA Signaling and Viral Infection

Viral infection and stimulation with lipopolysaccharide (LPS) or double stranded RNA (dsRNA) induce phosphorylation of interferon (IFN) regulatory factor (IRF)-3 and its translocation to the nucleus, thereby leading to the IFN-β gene induction. Recently, two IκB kinase (IKK)–related kinases, inducible IκB kinase (IKK-i) and TANK-binding kinase 1 (TBK1), were suggested to act as IRF-3 kinases and be involved in IFN-β production in Toll-like receptor (TLR) signaling and viral infection. In this work, we investigated the physiological roles of these kinases by gene targeting. TBK1-deficient embryonic fibroblasts (EFs) showed dramatic decrease in induction of IFN-β and IFN-inducible genes in response to LPS or dsRNA as well as after viral infection. However, dsRNA-induced expression of these genes was residually detected in TBK1-deficient cells and intact in IKK-i–deficient cells, but completely abolished in IKK-i/TBK1 doubly deficient cells. IRF-3 activation, in response not only to dsRNA but also to viral infection, was impaired in TBK1-deficient cells. Together, these results demonstrate that TBK1 as well as, albeit to a lesser extent, IKK-i play a crucial role in the induction of IFN-β and IFN-inducible genes in both TLR-stimulated and virus-infected EFs

Atraumatic Femoral Insufficiency Fracture in Postmenopausal Women Taking Bisphosphonate

The patient was 85-year-old woman. Five years and 8 months previously, bisphosphonate was prescribed for osteoporosis at a local clinic. Deformity of the thigh occurred when she tried to stand after sitting. X-ray findings revealed a transverse fracture of the right femoral diaphysis. Intramedullary nailing of the right femur was performed. Bone union was slightly delayed, but it was eventually achieved. Bisphosphonates have been reported to severely suppress bone turnover, resulting in the occurrence of fractures at the diaphysis or metaphysis of the femur. This type of fracture is characteristically induced by minor trauma and usually shows a simple transverse fracture. Bone union is delayed and these patients complain of prodromal symptoms. Because our case met all of the above criteria, it was concluded that the cause of her fracture was severely suppressed bone turnover (SSBT). We treated a patient who had a pathologic fracture associated with bisphosphonate therapy. Careful follow-up will be required, because it has been reported that such fractures can also occur on the contralateral side

Toll-like receptor 9 mediates innate immune activation by the malaria pigment hemozoin

Malaria parasites within red blood cells digest host hemoglobin into a hydrophobic heme polymer, known as hemozoin (HZ), which is subsequently released into the blood stream and then captured by and concentrated in the reticulo-endothelial system. Accumulating evidence suggests that HZ is immunologically active, but the molecular mechanism(s) through which HZ modulates the innate immune system has not been elucidated. This work demonstrates that HZ purified from Plasmodium falciparum is a novel non-DNA ligand for Toll-like receptor (TLR)9. HZ activated innate immune responses in vivo and in vitro, resulting in the production of cytokines, chemokines, and up-regulation of costimulatory molecules. Such responses were severely impaired in TLR9−/− and myeloid differentiation factor 88 (MyD88)−/−, but not in TLR2, TLR4, TLR7, or Toll/interleukin 1 receptor domain–containing adaptor-inducing interferon β−/− mice. Synthetic HZ, which is free of the other contaminants, also activated innate immune responses in vivo in a TLR9-dependent manner. Chloroquine (CQ), an antimalarial drug, abrogated HZ-induced cytokine production. These data suggest that TLR9-mediated, MyD88-dependent, and CQ-sensitive innate immune activation by HZ may play an important role in malaria parasite–host interactions