Sho Hangai

HMGB proteins function as universal sentinels for nucleic-acid-mediated innate immune responses.

The activation of innate immune responses by nucleic acids is crucial to protective and pathological immunities and is mediated by the transmembrane Toll-like receptors (TLRs) and cytosolic receptors. However, it remains unknown whether a mechanism exists that integrates these nucleic-acid-sensing systems. Here we show that high-mobility group box (HMGB) proteins 1, 2 and 3 function as universal sentinels for nucleic acids. HMGBs bind to all immunogenic nucleic acids examined with a correlation between affinity and immunogenic potential. Hmgb1-/- and Hmgb2-/- mouse cells are defective in type-I interferon and inflammatory cytokine induction by DNA or RNA targeted to activate the cytosolic nucleic-acid-sensing receptors; cells in which the expression of all three HMGBs is suppressed show a more profound defect, accompanied by impaired activation of the transcription factors interferon regulatory factor 3 (IRF3) and nuclear factor (NF)-κB. The absence of HMGBs also severely impairs the activation of TLR3, TLR7 and TLR9 by their cognate nucleic acids. Our results therefore indicate a hierarchy in the nucleic-acid-mediated activation of immune responses, wherein the selective activation of nucleic-acid-sensing receptors is contingent on the more promiscuous sensing of nucleic acids by HMGBs. These findings may have implications for understanding the evolution of the innate immune system and for the treatment of immunological disorders.

A selective contribution of the RIG-I-like receptor pathway to type I interferon responses activated by cytosolic DNA

The activation of the innate immune responses by DNA exposed within the cytosol has gained much attention and, in this context, several cytosolic DNA sensors have been identified. However, previous studies revealed the operation of redundant and complex mechanisms and it still remains to be clarified how the DNA-mediated evocation of diverse innate immune responses can be achieved. Here we show that two RIG-I-like receptors (RLRs), RIG-I and MDA5, known as cytosolic RNA receptors, nonredundantly function as cytosolic DNA receptors that lead to the selective activation of type I IFN genes. We demonstrate that overexpression of otherwise IFN-inducible RIG-I or MDA5 in IFN signal-deficient cells results in a marked enhancement of type I IFN gene induction upon cytosolic DNA stimulation, while in their absence the induction is impaired. Interestingly, the DNA-mediated induction of other cytokine genes was barely affected by the absence of RLRs. Indeed, unlike the RNA-RLR pathway that activates the transcription factors IRF3 and NF-κB, the DNA-RLR pathway is primarily responsible for the IRF3 activation critical for type I IFN gene transcription, illustrating a deliberate divergence of the DNA signaling pathways. Expectedly, the RLR pathway also contributes to intricate innate immune responses against infection by a DNA virus. Our study may provide insights into the complexity of host defense mechanisms that thwart immune evasion by DNA-containing pathogens.

Recognition of tumor cells by Dectin-1 orchestrates innate immune cells for anti-tumor responses

The eradication of tumor cells requires communication to and signaling by cells of the immune system. Natural killer (NK) cells are essential tumor-killing effector cells of the innate immune system; however, little is known about whether or how other immune cells recognize tumor cells to assist NK cells. Here, we show that the innate immune receptor Dectin-1 expressed on dendritic cells and macrophages is critical to NK-mediated killing of tumor cells that express N-glycan structures at high levels. Receptor recognition of these tumor cells causes the activation of the IRF5 transcription factor and downstream gene induction for the full-blown tumoricidal activity of NK cells. Consistent with this, we show exacerbated in vivo tumor growth in mice genetically deficient in either Dectin-1 or IRF5. The critical contribution of Dectin-1 in the recognition of and signaling by tumor cells may offer new insight into the anti-tumor immune system with therapeutic implications. DOI: http://dx.doi.org/10.7554/eLife.04177.001

PGE2 induced in and released by dying cells functions as an inhibitory DAMP

Significance Inflammation is an integral part of the immune responses for the protection of the host to harmful stimuli. However, because inflammation can also underlie the initiation and/or exacerbation of a variety of diseases, it must be tightly regulated. Upon cell death, self-derived molecules, called damage-associated molecular patterns (DAMPs), are released to activate inflammatory responses. It has been unknown whether inhibitory molecules are also released to balance the magnitude of the inflammatory responses. In this study, biochemical and in vivo data demonstrate that prostaglandin E2 is a DAMP that negatively regulates cell death-induced inflammatory responses. These findings reveal an unprecedented facet in the regulation of inflammation via the combined activity of activating and inhibiting DAMPs, which may have clinical implications. Cellular components released into the external milieu as a result of cell death and sensed by the body are generally termed damage-associated molecular patterns (DAMPs). Although DAMPs are conventionally thought to be protective to the host by evoking inflammatory responses important for immunity and wound repair, there is the prevailing notion that dysregulated release of DAMPs can also underlie or exacerbate disease development. However, the critical issue for how resultant DAMP-mediated responses are regulated has heretofore not been fully addressed. In the present study, we identify prostaglandin E2 (PGE2) as a DAMP that negatively regulates immune responses. We show that the production of PGE2 is augmented under cell death-inducing conditions via the transcriptional induction of the cyclooxygenase 2 (COX2) gene and that cell-released PGE2 suppresses the expression of genes associated with inflammation, thereby limiting the cell’s immunostimulatory activities. Consistent with this, inhibition of the PGE2 synthesis pathway potentiates the inflammation induced by dying cells. We also provide in vivo evidence for a protective role of PGE2 released upon acetaminophen-induced liver injury as well as a pathogenic role for PGE2 during tumor cell growth. Our study places this classically known lipid mediator in an unprecedented context—that is, an inhibitory DAMP vis-à-vis activating DAMPs, which may have translational implications for designing more effective therapeutic regimens for inflammation-associated diseases.

The innate immune receptor Dectin-2 mediates the phagocytosis of cancer cells by Kupffer cells for the suppression of liver metastasis.

Significance The liver is a common site for metastatic disease, and liver metastasis is strongly correlated with poor prognosis. Therefore, an understanding of how liver metastasis is regulated by the immune system is one of the most important issues in cancer immunology. Liver-resident immune cells may either suppress or promote liver metastasis. In this study, we show that Dectin-2 and macrophage C-type lectin, both of which belong to the C-type lectin family of innate receptors, is expressed on resident liver macrophages known as Kupffer cells and play critical roles in the suppression of liver metastasis by enhancing the cells’ phagocytotic activity against cancer cells. Our study sheds light on the protective role of Kupffer cells in liver metastasis with therapeutic implications. Tumor metastasis is the cause of most cancer deaths. Although metastases can form in multiple end organs, the liver is recognized as a highly permissive organ. Nevertheless, there is evidence for immune cell-mediated mechanisms that function to suppress liver metastasis by certain tumors, although the underlying mechanisms for the suppression of metastasis remain elusive. Here, we show that Dectin-2, a C-type lectin receptor (CLR) family of innate receptors, is critical for the suppression of liver metastasis of cancer cells. We provide evidence that Dectin-2 functions in resident macrophages in the liver, known as Kupffer cells, to mediate the uptake and clearance of cancer cells. Interestingly, Kupffer cells are selectively endowed with Dectin-2–dependent phagocytotic activity, with neither bone marrow-derived macrophages nor alveolar macrophages showing this potential. Concordantly, subcutaneous primary tumor growth and lung metastasis are not affected by the absence of Dectin-2. In addition, macrophage C-type lectin, a CLR known to be complex with Dectin-2, also contributes to the suppression of liver metastasis. Collectively, these results highlight the hitherto poorly understood mechanism of Kupffer cell-mediated control of metastasis that is mediated by the CLR innate receptor family, with implications for the development of anticancer therapy targeting CLRs.

Role of procalcitonin and C-reactive protein for discrimination between tumor fever and infection in patients with hematological diseases

Abstract Tumor fever is a common complication in patients with hematological malignancies. We retrospectively analyzed the levels of C-reactive protein (CRP) and procalcitonin (PCT) in patients with lymphoid malignancies and fever that was attributed to tumor (39 episodes, group I) or infection (26 episodes, group II) before chemotherapy, and bloodstream infection (26 episodes, group III) after chemotherapy. The PCT level and PCT/CRP ratio were significantly higher in groups II and III than in group I (p = 0.003, p = 0.0005, respectively for groups II and I, and p = 0.003, p = 0.00002, respectively for groups III and I). At the cut-off level of 0.071 or 0.014 for PCT/CRP, the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of PCT/CRP were 53.8% or 96.2%, 89.7% or 53.8%, 77.8% or 58.1% and 74.5% or 95.5%, respectively, for discrimination between groups I and II or groups I and III. PCT/CRP ratio was the best marker for discrimination between tumor fever and infection.

An indeterminate result of QuantiFERON-TB Gold In-Tube for miliary tuberculosis due to a high level of IFN-γ production

The QuantiFERON-TB Gold In-Tube® test has excellent specificity for Mycobacterium tuberculosis. However, diagnosis of miliary tuberculosis remains challenging, and the interpretation of QuantiFERON® results in immunocompromised individuals has not been fully established. Here, we present a patient with military tuberculosis who showed an indeterminate QuantiFERON® result. A 76-year-old male presented with fever and pancytopenia. Radiological tests did not show the classical miliary pattern. Acid-fast staining and polymerase chain reaction of several specimens were negative for M. tuberculosis. The QuantiFERON® responses were indeterminate on two separate tests, as interferon-γ (IFN-γ) concentration was high in the negative control. The patient did not respond to anti-microbiological therapy, and developed sepsis and disseminated intravascular coagulation, leading to lethal intracranial hemorrhage. An autopsy showed miliary tuberculosis and aplastic anemia. A literature review suggests a tendency towards indeterminate or false-negative QuantiFERON® results in immunocompromised individuals or patients with miliary tuberculosis due to low production of IFN-γ. Our patient, however, showed substantial amounts of IFN-γ despite lymphocytopenia, which has not been reported in the literature. The present case suggests that indeterminate results of QuantiFERON® should be interpreted with caution, as IFN-γ production in patients with miliary tuberculosis can vary significantly, even with sustained lymphocytopenia.

Primary gastrointestinal follicular lymphoma with histological transformation.

Dear Editor, Primary gastrointestinal follicular lymphoma (GI-FL) accounts for 30 to 40 % of primary extranodal FL [1]. The disease usually manifests as multiple small polyps in the duodenum or terminal ileum. Histological grade at presentation is low in most cases (95.8 %) and histological transformation (HT) is very rare [2]. Moreover, primary GI-FL is not visualized by fluorodeoxyglucose (FDG)-positron emission tomography (PET), which is in sharp contrast to nodal FL [1, 3]. Here, we describe a case of primary GI-FL with HT at initial presentation. A 45-year-old male was referred to our institution for evaluation of epigastralgia. Gastroduodenoscopy detected multiple and homogeneous small polyps without mass formation in the descending portion of the duodenum (Fig. 1a). A total of seven specimens were randomly taken from the polyps. Among them, six specimens showed proliferation of atypical lymphocytes with follicle formation (Fig. 1b). The immunophenotypes were CD3−, CD10+, CD20+, and bcl-2+. Fluorescence in situ hybridization analysis disclosed a BCL2-IGH fusion signal. These findings were consistent with FL. One specimen, however, showed transformation to large cell lymphoma with the same immunophenotype (Fig. 1c). FDG-PET combined with computed tomography scan was unremarkable including the descending duodenum (Fig. 1d). There was no evidence of bone marrow involvement. Finally, we made the diagnosis of primary GI-FL with HT. The patient underwent six cycles of cyclophosphamide, doxorubicin, vincristine, and prednisolone chemotherapy plus rituximab. Gastroduodenoscopy after the treatment confirmed complete regression of the polypoid lesion. In the present case, aggressive biopsy led to an unexpected detection of HT. A study by Shia et al. demonstrated that 4 (15 %) of 26 primary GI-FL cases were found to have large cell lymphoma admixed with FL at initial diagnosis [4]. Therefore, HT within a GI-FL lesion at initial presentation is a recurrent phenomenon, although it has not been reconfirmed in later studies [2, 5]. Clinical features of the Shias cases and ours provide important clues to characterize primary GI-FL with HT. Firstly, three (75 %) of four cases manifested as multiple nodules without mass formation on endoscopic examination. It is therefore likely that HT in primary GI-FL cannot be suspected by mere morphology. Secondly, all the patients were alive at 5 to 102 months after treatment with standard chemotherapy. HT inGI-FLmight be associatedwith a less aggressive outcome than HT in usual FL. S. Hangai : F. Nakamura :Y. Kamikubo :M. Ichikawa : M. Kurokawa Department of Hematology and Oncology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan

Erythroleukemia showing early erythroid and cytogenetic responses to azacitidine therapy

Dear Editor, Hypomethylating agents exert cytotoxic effects and induce differentiation of hematopoietic cells. Azacitidine therapy for myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) with multi-lineage dysplasia resulted in a significant survival advantage over conventional treatment [1–3]. Nevertheless, its efficacy against a specific subtype of MDS/AML has not been fully unveiled. Here, we characterize the response to azacitidine therapy in patients with erythroleukemia. The first case is a 79-year-old male presenting with progressive pancytopenia and red cell transfusion dependency. His hemoglobin level was 82 g/L, white blood cell (WBC) count 1.8×10/L with 1.5 % blasts, platelet count 5.5×10/L, and erythroblast count 27 per 100 WBCs. The bone marrow was hypercellular with multilineage dysplasia and erythroid dominance (Fig. 1a). Myeloblasts accounted for 40 % of non-erythroid cells

Successful transarterial embolization for recurrent pseudoaneurysm of the right hepatic artery with acute cholecystitis

Pseudoaneurysm of the right hepatic artery is an extremely rare complication of acute cholecystitis. We report a patient with a right hepatic artery pseudoaneurysm associated with acute cholecystitis who was treated successfully by transarterial embolization. We also review the literature on right hepatic artery pseudoaneurysm secondary to acute cholecystitis. A 50-year-old male visited Fujieda General Municipal Hospital with an episode of sudden headache. He was diagnosed with a subarachnoid hemorrhage and treated successfully by microcoil embolization on hospital day 4. On hospital day 54, he developed fever and right upper quadrant tenderness. Abdominal ultrasonography revealed acute cholecystitis, while color Doppler imaging showed a low-echogenic mass with a pulsatile wave pattern inside the gallbladder. Contrast-enhanced computed tomography (CE-CT) demonstrated a pseudoaneurysm in the gallbladder, and angiography disclosed a right hepatic artery pseudoaneurysm. Selective transarterial embolization (TAE) was then performed using a steel coil. Abdominal pain and fever continued after TAE, with CE-CT showing re-bleeding from the previous pseudoaneurysm. Selective angiography identified extravasation at the same place as the previous pseudoaneurysm from the posterior superior pancreaticoduodenal artery and the inferior pancreaticoduodenal artery via the epicholedochal arterial plexus. TAE was performed resulting in successful occlusion of the pseudoaneurysm.