Publications by authors named "Ayako Kaitani"

21 Publications

  • Page 1 of 1

A possible association between a novel NLRP1 mutation and an autoinflammatory disease involving liver cirrhosis.

Hepatology 2021 Mar 19. Epub 2021 Mar 19.

Atopy (Allergy) Research Center, Juntendo University Graduate School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan.

The nucleotide-binding domain leucine-rich repeat (LRR)-containing protein family pyrin domain (PYD)-containing protein 1 (NLRP1) forms an inflammasome complex with apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) and caspase-1. Inflammasome-activated caspase-1 cleaves pro-IL-1β or pro-IL-18 to produce its mature form and induces a type of cell death called pyroptosis through gasdermin D (GSDMD) activation.
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http://dx.doi.org/10.1002/hep.31818DOI Listing
March 2021

Orally desensitized mast cells form a regulatory network with Treg cells for the control of food allergy.

Mucosal Immunol 2020 Dec 10. Epub 2020 Dec 10.

Department of Mucosal Immunology, The University of Tokyo Distinguished Professor Unit, The Institute of Medical Science, The University of Tokyo, Tokyo, 108-8639, Japan.

Oral immunotherapy (OIT) is an effective approach to controlling food allergy. Although the detailed molecular and cellular mechanisms of OIT are unknown currently, they must be understood to advance the treatment of allergic diseases in general. To elucidate the mechanisms of OIT, especially during the immunological transition from desensitization to allergy regulation, we generated a clinical OIT murine model and used it to examine immunological events of OIT. We found that in mice that completed OIT successfully, desensitized mast cells (MCs) showed functionally beneficial alterations, such as increased induction of regulatory cytokines and enhanced expansion of regulatory T cells. Importantly, these regulatory-T-cell-mediated inhibitions of allergic responses were dramatically decreased in mice lacking OIT-induced desensitized MC. Collectively, these findings show that the desensitization process modulates the activation of MCs, leading directly to enhanced induction of regulatory-T-cell expansion and promotion of clinical allergic unresponsiveness. Our results suggest that efficiently inducing regulatory MCs is a novel strategy for the treatment of allergic disease.
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http://dx.doi.org/10.1038/s41385-020-00358-3DOI Listing
December 2020

Notch signaling contributes to the establishment of sustained unresponsiveness to food allergens by oral immunotherapy.

J Allergy Clin Immunol 2021 Mar 24;147(3):1063-1076.e9. Epub 2020 Jul 24.

Department of Pediatrics and Adolescent Medicine, Juntendo University Graduate School of Medicine, Tokyo, Japan.

Background: Oral immunotherapy (OIT) aims to establish desensitization and sustained unresponsiveness (SU) in patients with food allergy by ingestion of gradually increasing doses of specific food allergens. However, little is known about the mechanisms by which OIT induces SU to specific allergens.

Objectives: We investigated the role of Notch signaling, which controls cell fate decisions in many types of immune cells in the induction of SU by OIT treatment.

Methods: Two types of mouse models, ovalbumin-induced food allergy and OIT, were generated. To elucidate the role of Notch signaling in OIT-induced SU, mice were intraperitoneally injected with the Notch signaling inhibitor N-[(3,5-difluorophenyl)acetyl]-l-alanyl-2-phenylglycine-1,1-dimethylethyl ester during the OIT treatment period.

Results: Ovalbumin-sensitized mice were desensitized and also had SU induced by OIT treatment, whereas repeated challenges with ovalbumin caused the development of severe allergic reactions in ovalbumin-sensitized mice. Administration of N-[(3,5-difluorophenyl)acetyl]-l-alanyl-2-phenylglycine-1,1-dimethylethyl ester to mice during the OIT treatment period inhibited the establishment of SU to ovalbumin but did not affect the induction of desensitization. OIT induced a systemic expansion of IL-10-producing CD4 T cells, including T2 cells, and myeloid-derived suppressor cells (MDSCs), particularly the monocytic MDSC subpopulation. Inhibition of Notch signaling prevented the OIT-induced expansion of those cells. In vitro cultures of bone marrow cells showed that Notch signaling directly promoted the generation of monocytic MDSCs. In addition, the contribution of MDSCs to OIT-induced SU was confirmed by MDSC depletion with the anti-Gr1 antibody.

Conclusion: Notch signaling contributes to the establishment of SU induced by OIT through systemic expansion of immunosuppressive cells, such as IL-10-producing CD4 T cells and MDSCs.
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http://dx.doi.org/10.1016/j.jaci.2020.07.011DOI Listing
March 2021

The phytosphingosine-CD300b interaction promotes zymosan-induced, nitric oxide-dependent neutrophil recruitment.

Sci Signal 2019 01 15;12(564). Epub 2019 Jan 15.

Division of Cellular Therapy/Division of Stem Cell Signaling, The Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.

Zymosan is a glucan that is a component of the yeast cell wall. Here, we determined the mechanisms underlying the zymosan-induced accumulation of neutrophils in mice. Loss of the receptor CD300b reduced the number of neutrophils recruited to dorsal air pouches in response to zymosan, but not in response to lipopolysaccharide (LPS), a bacterial membrane component recognized by Toll-like receptor 4 (TLR4). An inhibitor of nitric oxide (NO) synthesis reduced the number of neutrophils in the zymosan-treated air pouches of wild-type mice to an amount comparable to that in mice. Treatment with clodronate liposomes decreased the number of NO-producing, CD300b inflammatory dendritic cells (DCs) in wild-type mice, thus decreasing NO production and neutrophil recruitment. Similarly, CD300b deficiency decreased the NO-dependent recruitment of neutrophils to zymosan-treated joint cavities, thus ameliorating subsequent arthritis. We identified phytosphingosine, a lipid component of zymosan, as a potential ligand of CD300b. Phytosphingosine stimulated NO production in inflammatory DCs and promoted neutrophil recruitment in a CD300b-dependent manner. Together, these results suggest that the phytosphingosine-CD300b interaction promotes zymosan-dependent neutrophil accumulation by inducing NO production by inflammatory DCs and that CD300b may contribute to antifungal immunity.
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http://dx.doi.org/10.1126/scisignal.aar5514DOI Listing
January 2019

The Fab fragment of anti-IgE Cε2 domain prevents allergic reactions through interacting with IgE-FcεRIα complex on rat mast cells.

Sci Rep 2018 09 24;8(1):14237. Epub 2018 Sep 24.

Atopy (Allergy) Research Center, Juntendo University Graduate School of Medicine, Juntendo University Graduate School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, Japan.

Immunoglobulin E (IgE) plays a central role in the pathogenesis of Type I hypersensitivity through interaction with a high-affinity receptor (FcεRIα). For therapeutic applications, substantial attention has been focused recently on the blockade of the IgE interaction with FcεRIα. While exploring better options for preventing allergic diseases, we found that the Fab fragment of the rat anti-murine IgE antibody (Fab-6HD5) strongly inhibited passive cutaneous anaphylaxis (PCA) in vivo, as well as spleen tyrosine kinase (Syk) activity and β-hexosaminidase release from basophilic leukemia cells in vitro. The in vivo effects of Fab-6HD5 pre-administration were maintained over a long period of time for at least 10 days. Using flow cytometry analysis, we also found that Fab-6HD5 did not recognize the IgE Cε3 domain containing specific binding sites for FcεRIα. Furthermore, deletion-mapping studies revealed that Fab-6HD5 recognized conformational epitopes on the Cε2 domain of IgE. Given that the Cε2 domain plays a key role in stabilizing the interaction of IgE with FcRIα, our results suggest that the specific binding of Fab-6HD5 to the Cε2 domain prevents allergic reactions through destabilizing the preformed IgE-FcεRIα complex on rat mast cells. Although the present study was performed using animal models, these findings support the idea that a certain antibody directed against IgE CH domains may contribute to preventing allergic diseases through interacting with IgE-FcεRIα complex.
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http://dx.doi.org/10.1038/s41598-018-32200-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6155129PMC
September 2018

Leukocyte mono-immunoglobulin-like receptor 8 (LMIR8)/CLM-6 is an FcRγ-coupled receptor selectively expressed in mouse tissue plasmacytoid dendritic cells.

Sci Rep 2018 05 29;8(1):8259. Epub 2018 May 29.

Atopy (Allergy) Research Center, Juntendo University Graduate School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan.

Plasmacytoid dendritic cells (pDCs) produce large amounts of type-I interferon (IFN) in response to viral infection or self nucleic acids. Leukocyte mono-immunoglobulin-like receptor 8 (LMIR8), also called CMRF-35-like molecule-6 (CLM-6), is a putative activating receptor among mouse LMIR/CLM/CD300 members; however, the expression and function of LMIR8 remain unclear. Here, we characterize mouse LMIR8 as a pDC receptor. Analysis of Flag-tagged LMIR8-transduced bone marrow (BM)-derived mast cells demonstrated that LMIR8 can transmit an activating signal by interacting with immunoreceptor tyrosine-based activating motif (ITAM)-containing FcRγ. Flow cytometric analysis using a specific antibody for LMIR8 showed that LMIR8 expression was restricted to mouse pDCs residing in BM, spleen, or lymph node. FcRγ deficiency dampened surface expression of LMIR8 in mouse pDCs. Notably, LMIR8 was detected only in pDCs, irrespective of TLR9 stimulation, suggesting that LMIR8 is a suitable marker for pDCs in mouse tissues; LMIR8 is weakly expressed in Flt3 ligand-induced BM-derived pDCs (BMpDCs). Crosslinking of transduced LMIR8 in BMpDCs with anti-LMIR8 antibody did not induce IFN-α production, but rather suppressed TLR9-mediated production of IFN-α. Taken together, these observations indicate that LMIR8 is an FcRγ-coupled receptor selectively expressed in mouse tissue pDCs, which might suppress pDC activation through the recognition of its ligands.
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http://dx.doi.org/10.1038/s41598-018-25646-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5974347PMC
May 2018

The CD300e molecule in mice is an immune-activating receptor.

J Biol Chem 2018 03 22;293(10):3793-3805. Epub 2018 Jan 22.

From the Atopy (Allergy) Research Center, Juntendo University Graduate School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421,

CD300 molecules (CD300s) belong to paired activating and inhibitory receptor families, which mediate immune responses. Human CD300e (hCD300e) is expressed in monocytes and myeloid dendritic cells and transmits an immune-activating signal by interacting with DNAX-activating protein 12 (DAP12). However, the CD300e ortholog in mice (mCD300e) is poorly characterized. Here, we found that mCD300e is also an immune-activating receptor. We found that mCD300e engagement triggers cytokine production in mCD300e-transduced bone marrow-derived mast cells (BMMCs). Loss of DAP12 and another signaling protein, FcRγ, did not affect surface expression of transduced mCD300e, but abrogated mCD300e-mediated cytokine production in the BMMCs. Co-immunoprecipitation experiments revealed that mCD300e physically interacts with both FcRγ and DAP12, suggesting that mCD300e delivers an activating signal via these two proteins. Binding and reporter assays with the mCD300e extracellular domain identified sphingomyelin as a ligand of both mCD300e and hCD300e. Notably, the binding of sphingomyelin to mCD300e stimulated cytokine production in the transduced BMMCs in an FcRγ- and DAP12-dependent manner. Flow cytometric analysis with an mCD300e-specific Ab disclosed that mCD300e expression is highly restricted to CD115Ly-6C peripheral blood monocytes, corresponding to CD14CD16 human nonclassical and intermediate monocytes. Loss of FcRγ or DAP12 lowered the surface expression of endogenous mCD300e in the CD115Ly-6C monocytes. Stimulation with sphingomyelin failed to activate the CD115Ly-6C mouse monocytes, but induced hCD300e-mediated cytokine production in the CD14CD16 human monocytes. Taken together, these observations indicate that mCD300e recognizes sphingomyelin and thereby regulates nonclassical and intermediate monocyte functions through FcRγ and DAP12.
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http://dx.doi.org/10.1074/jbc.RA117.000696DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5846139PMC
March 2018

Role of the Ceramide-CD300f Interaction in Gram-Negative Bacterial Skin Infections.

J Invest Dermatol 2018 05 5;138(5):1221-1224. Epub 2017 Dec 5.

Atopy (Allergy) Research Center, Juntendo University Graduate School of Medicine, Tokyo, Japan; Division of Cellular Therapy/Division of Stem Cell Signaling, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan. Electronic address:

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http://dx.doi.org/10.1016/j.jid.2017.11.025DOI Listing
May 2018

Disrupting ceramide-CD300f interaction prevents septic peritonitis by stimulating neutrophil recruitment.

Sci Rep 2017 06 27;7(1):4298. Epub 2017 Jun 27.

Atopy Research Center, Juntendo University Graduate School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan.

Sepsis is a serious clinical problem. Negative regulation of innate immunity is associated with sepsis progression, but the underlying mechanisms remains unclear. Here we show that the receptor CD300f promotes disease progression in sepsis. CD300f mice were protected from death after cecal ligation and puncture (CLP), a murine model of septic peritonitis. CD300f was highly expressed in mast cells and recruited neutrophils in the peritoneal cavity. Analysis of mice (e.g., mast cell-deficient mice) receiving transplants of wild-type or CD300f mast cells or neutrophils indicated that CD300f deficiency did not influence intrinsic migratory abilities of neutrophils, but enhanced neutrophil chemoattractant production (from mast cells and neutrophils) in the peritoneal cavity of CLP-operated mice, leading to robust accumulation of neutrophils which efficiently eliminated Escherichia coli. Ceramide-CD300f interaction suppressed the release of neutrophil chemoattractants from Escherichia coli-stimulated mast cells and neutrophils. Administration of the reagents that disrupted the ceramide-CD300f interaction prevented CLP-induced sepsis by stimulating neutrophil recruitment, whereas that of ceramide-containing vesicles aggravated sepsis. Extracellular concentrations of ceramides increased in the peritoneal cavity after CLP, suggesting a possible role of extracellular ceramides, CD300f ligands, in the negative-feedback suppression of innate immune responses. Thus, CD300f is an attractive target for the treatment of sepsis.
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http://dx.doi.org/10.1038/s41598-017-04647-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5487349PMC
June 2017

Ceramide-CD300f Binding Inhibits Lipopolysaccharide-induced Skin Inflammation.

J Biol Chem 2017 02 10;292(7):2924-2932. Epub 2017 Jan 10.

From the Atopy Research Center and

LPS triggers inflammatory responses; however, the negative regulation of LPS responses remains poorly understood. CD300f is an inhibitory receptor among the CD300 family of paired activating and inhibitory receptors. We have previously identified ceramide as a ligand for CD300f and shown that the binding of ceramide to CD300f inhibits IgE-mediated mast cell activation and allergic responses in mouse models. Here we identify the critical role of CD300f in inhibiting LPS-induced skin inflammation. CD300f deficiency remarkably enhanced LPS-induced skin edema and neutrophil recruitment in mice. Higher levels of factors that increase vascular permeability and of factors that induce neutrophil recruitment were detected in LPS-injected skin pouch exudates of mice as compared with wild-type mice. CD300f was highly expressed in mast cells and recruited neutrophils, but not in macrophages, among skin myeloid cells. CD300f deficiency failed to influence the intrinsic migratory ability of neutrophils. Ceramide-CD300f binding suppressed the release of chemical mediators from mast cells and from neutrophils in response to LPS. Adoptive transfer experiments indicated that mast cells mediated enhanced edema in LPS-stimulated skin of mice, whereas mast cells together with recruited neutrophils mediated robust neutrophil accumulation. Importantly, administering a ceramide antibody or ceramide-containing vesicles enhanced or suppressed LPS-induced skin inflammation of wild-type mice, respectively. Thus, ceramide-CD300f binding inhibits LPS-induced skin inflammation, implicating CD300f as a negative regulator of Toll-like receptor 4 (TLR4) signaling .
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http://dx.doi.org/10.1074/jbc.M116.768366DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5314187PMC
February 2017

Ceramide-CD300f binding suppresses experimental colitis by inhibiting ATP-mediated mast cell activation.

Gut 2016 May 11;65(5):777-87. Epub 2015 Feb 11.

Division of Cellular Therapy, Advanced Clinical Research Center, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan Atopy Research Center, Juntendo University School of Medicine, Tokyo, Japan.

Objective: Extracellular ATP mediates mast cell-dependent intestinal inflammation via P2X7 purinoceptors. We have previously shown that CD300f (also called the leucocyte mono-immunoglobulin-like receptor 3 (LMIR3)) suppresses immunoglobulin E-dependent and mast cell-dependent allergic responses by binding to ceramide. The aim of the present study was to clarify the role of ceramide-LMIR3 interaction in the development of IBD.

Design: The dextran sodium sulfate (DSS)-induced colitis model was used in wild-type (WT), LMIR3(-/-), mast cell-deficient Kit(W-sh/W-sh), Kit(W-sh/W-sh)LMIR3(-/-) or Kit(W-sh/W-sh) mice engrafted with WT or LMIR3(-/-) bone marrow-derived mast cells (BMMCs). The severity of colitis was determined by clinical and histological criteria. Lamina propria cell populations were assessed by flow cytometry. Production of chemical mediators from lamina propria cells was measured by real-time reverse transcription PCR. Production of chemical mediators from ATP-stimulated BMMCs in the presence or absence of ceramide was measured by ELISA. The severity of DSS-induced colitis was assessed in mice given either an Fc fusion protein containing an extracellular domain of LMIR3, and anticeramide antibody, or ceramide liposomes.

Results: LMIR3 deficiency exacerbated DSS-induced colitis in mice. Kit(W-sh/W-sh) mice harbouring LMIR3(-/-) mast cells exhibited more severe colitis than those harbouring WT mast cells. Ceramide-LMIR3 interaction inhibited ATP-stimulated activation of BMMCs. DSS-induced colitis was aggravated by disrupting the ceramide-LMIR3 interaction, whereas it was suppressed by treating with ceramide liposomes.

Conclusions: LMIR3-deficient colonic mast cells were pivotal in the exacerbation of DSS-induced colitis in LMIR3(-/-) mice. Ceramide liposomes attenuated DSS-induced colitis by inhibiting ATP-mediated activation of colonic mast cells through ceraimide-LMIR3 binding.
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http://dx.doi.org/10.1136/gutjnl-2014-308900DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4853571PMC
May 2016

Sphingomyelin and ceramide are physiological ligands for human LMIR3/CD300f, inhibiting FcεRI-mediated mast cell activation.

J Allergy Clin Immunol 2014 Jan 12;133(1):270-3.e1-7. Epub 2013 Sep 12.

Division of Cellular Therapy, The Institute of Medical Science, University of Tokyo, Tokyo, Japan. Electronic address:

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http://dx.doi.org/10.1016/j.jaci.2013.08.008DOI Listing
January 2014

Human CD300C delivers an Fc receptor-γ-dependent activating signal in mast cells and monocytes and differs from CD300A in ligand recognition.

J Biol Chem 2013 Mar 31;288(11):7662-7675. Epub 2013 Jan 31.

Division of Cellular Therapy, Advanced Clinical Research Center, The Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan. Electronic address:

CD300C is highly homologous with an inhibitory receptor CD300A in an immunoglobulin-like domain among the human CD300 family of paired immune receptors. To clarify the precise expression and function of CD300C, we generated antibodies discriminating between CD300A and CD300C, which recognized a unique epitope involving amino acid residues CD300A(F56-L57) and CD300C(L63-R64). Notably, CD300C was highly expressed in human monocytes and mast cells. Cross-linking of CD300C by its specific antibody caused cytokine/chemokine production of human monocytes and mast cells. Fc receptor γ was indispensable for both efficient surface expression and activating functions of CD300C. To identify a ligand for CD300A or CD300C, we used reporter cell lines expressing a chimera receptor harboring extracellular CD300A or CD300C and intracellular CD3ζ, in which its unknown ligand induced GFP expression. Our results indicated that phosphatidylethanolamine (PE) among the lipids tested and apoptotic cells were possible ligands for both CD300C and CD300A. PE and apoptotic cells more strongly induced GFP expression in the reporter cells through binding to extracellular CD300A as compared with CD300C. Differential recognition of PE by extracellular CD300A and CD300C depended on different amino acid residues CD300A(F56-L57) and CD300C(L63-R64). Interestingly, GFP expression induced by extracellular CD300C-PE binding in the reporter cells was dampened by co-expression of full-length CD300A, indicating the predominance of CD300A over CD300C in PE recognition/signaling. PE consistently failed to stimulate cytokine production in monocytes expressing CD300C with CD300A. In conclusion, specific engagement of CD300C led to Fc receptor γ-dependent activation of mast cells and monocytes.
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http://dx.doi.org/10.1074/jbc.M112.434746DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3597807PMC
March 2013

The receptor LMIR3 negatively regulates mast cell activation and allergic responses by binding to extracellular ceramide.

Immunity 2012 Nov 1;37(5):827-39. Epub 2012 Nov 1.

Division of Cellular Therapy, Advanced Clinical Research Center, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo, Japan.

Mast cells (MCs) are key effector cells in allergic reactions. However, the inhibitory mechanism that prevents excessive activation of MCs remains elusive. Here we show that leukocyte mono-immunoglobulin-like receptor 3 (LMIR3; also called CD300f) is a negative regulator of MC activation in vivo. LMIR3 deficiency exacerbated MC-dependent allergic responses in mice, including anaphylaxis, airway inflammation, and dermatitis. Both physical binding and functional reporter assays via an extracellular domain of LMIR3 showed that several extracellular lipids (including ceramide) and lipoproteins were possible ligands for LMIR3. Importantly, MCs were frequently surrounded by extracellular ceramide in vivo. Upon engagement of high-affinity immunoglobulin E receptor, extracellular ceramide-LMIR3 binding inhibited MC activation via immunoreceptor tyrosine-based inhibitory and switch motifs of LMIR3. Moreover, pretreatment with LMIR3-Fc fusion protein or antibody against either ceramide or LMIR3 interfered with this binding in vivo, thereby exacerbating passive cutaneous anaphylaxis. Thus, the interaction between extracellular ceramide and LMIR3 suppressed MC-dependent allergic responses.
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http://dx.doi.org/10.1016/j.immuni.2012.08.018DOI Listing
November 2012

A soluble form of LMIR5/CD300b amplifies lipopolysaccharide-induced lethal inflammation in sepsis.

J Immunol 2012 Aug 6;189(4):1773-9. Epub 2012 Jul 6.

Division of Cellular Therapy, Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo 108-8639, Japan;

Leukocyte mono-Ig-like receptor 5 (LMIR5, also called CD300b) is an activating receptor expressed in myeloid cells. We have previously demonstrated that T cell Ig mucin 1 works as a ligand for LMIR5 in mouse ischemia/reperfusion injury of the kidneys. In this article, we show that LMIR5 is implicated in LPS-induced sepsis in mice. Notably, neutrophils constitutively released a soluble form of LMIR5 (sLMIR5) through proteolytic cleavage of surface LMIR5. Stimulation with TLR agonists augmented the release of sLMIR5. LPS administration or peritonitis induction increased serum levels of sLMIR5 in mice, which was substantially inhibited by neutrophil depletion. Thus, neutrophils were the main source of LPS-induced sLMIR5 in vivo. On the other hand, i.p. administration of LMIR5-Fc, a surrogate of sLMIR5, bound to resident macrophages (M) and stimulated transient inflammation in mice. Consistently, LMIR5-Fc induced in vitro cytokine production of peritoneal M via its unknown ligand. Interestingly, LMIR5 deficiency profoundly reduced systemic cytokine production and septic mortality in LPS-administered mice, although it did not affect in vitro cytokine production of LPS-stimulated peritoneal M. Importantly, the resistance of LMIR5-deficient mice to LPS- or peritonitis-induced septic death was decreased by LMIR5-Fc administration, implicating sLMIR5 in LPS responses in vivo. Collectively, neutrophil-derived sLMIR5 amplifies LPS-induced lethal inflammation.
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http://dx.doi.org/10.4049/jimmunol.1201139DOI Listing
August 2012

Characterization of leukocyte mono-immunoglobulin-like receptor 7 (LMIR7)/CLM-3 as an activating receptor: its similarities to and differences from LMIR4/CLM-5.

J Biol Chem 2010 Nov 3;285(46):35274-83. Epub 2010 Sep 3.

Division of Cellular Therapy, Advanced Clinical Research Center, Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.

Here we characterize leukocyte mono-Ig-like receptor 7 (LMIR7)/CLM-3 and compare it with an activating receptor, LMIR4/CLM-5, that is a counterpart of an inhibitory receptor LMIR3/CLM-1. LMIR7 shares high homology with LMIR4 in the amino acid sequences of its Ig-like and transmembrane domains. Flow cytometric analysis demonstrated that LMIR4 was predominantly expressed in neutrophils, whereas LMIR7 was highly expressed in mast cells and monocytes/macrophages. Importantly, LMIR7 engagement induced cytokine production in bone marrow-derived mast cells (BMMCs). Although FcRγ deficiency did not affect surface expression levels of LMIR7, it abolished LMIR7-mediated activation of BMMCs. Consistently we found significant interaction of LMIR7-FcRγ, albeit with lower affinity compared with that of LMIR4-FcRγ. Our results showed that LMIR7 transmits an activating signal through interaction with FcRγ. In addition, like LMIR4, LMIR7 synergizes with TLR4 in signaling. Analysis of several chimera receptors composed of LMIR4 and LMIR7 revealed these findings: 1) the transmembrane of LMIR7 with no charged residues maintained its surface expression at high levels in the absence of FcRγ; 2) the extracellular juxtamembrane region of LMIR7 had a negative effect on its surface expression levels; and 3) the strong interaction of LMIR4 with FcRγ depended on the extracellular juxtamembrane region as well as the transmembrane domain of LMIR4. Thus, LMIR7 shares similarities with LMIR4, although they are differentially regulated in their distribution, expression, and function.
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http://dx.doi.org/10.1074/jbc.M110.137166DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2975151PMC
November 2010

TIM1 is an endogenous ligand for LMIR5/CD300b: LMIR5 deficiency ameliorates mouse kidney ischemia/reperfusion injury.

J Exp Med 2010 Jul 21;207(7):1501-11. Epub 2010 Jun 21.

Division of Cellular Therapy, The Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo 108-8639, Japan.

Leukocyte mono-immunoglobulin (Ig)-like receptor 5 (LMIR5)/CD300b is a DAP12-coupled activating receptor predominantly expressed in myeloid cells. The ligands for LMIR have not been reported. We have identified T cell Ig mucin 1 (TIM1) as a possible ligand for LMIR5 by retrovirus-mediated expression cloning. TIM1 interacted only with LMIR5 among the LMIR family, whereas LMIR5 interacted with TIM4 as well as TIM1. The Ig-like domain of LMIR5 bound to TIM1 in the vicinity of the phosphatidylserine (PS)-binding site within the Ig-like domain of TIM1. Unlike its binding to TIM1 or TIM4, LMIR5 failed to bind to PS. LMIR5 binding did not affect TIM1- or TIM4-mediated phagocytosis of apoptotic cells, and stimulation with TIM1 or TIM4 induced LMIR5-mediated activation of mast cells. Notably, LMIR5 deficiency suppressed TIM1-Fc-induced recruitment of neutrophils in the dorsal air pouch, and LMIR5 deficiency attenuated neutrophil accumulation in a model of ischemia/reperfusion injury in the kidneys in which TIM1 expression is up-regulated. In that model, LMIR5 deficiency resulted in ameliorated tubular necrosis and cast formation in the acute phase. Collectively, our results indicate that TIM1 is an endogenous ligand for LMIR5 and that the TIM1-LMIR5 interaction plays a physiological role in immune regulation by myeloid cells.
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http://dx.doi.org/10.1084/jem.20090581DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2901072PMC
July 2010

An activating and inhibitory signal from an inhibitory receptor LMIR3/CLM-1: LMIR3 augments lipopolysaccharide response through association with FcRgamma in mast cells.

J Immunol 2009 Jul 26;183(2):925-36. Epub 2009 Jun 26.

Division of Cellular Therapy, Advanced Clinical Research Center, The Institute of Medical Science, The University of Tokyo, Tokyo, Japan.

Leukocyte mono-Ig-like receptor 3 (LMIR3) is an inhibitory receptor mainly expressed in myeloid cells. Coengagement of Fc epsilonRI and LMIR3 impaired cytokine production in bone marrow-derived mast cells (BMMCs) induced by Fc epsilonRI crosslinking alone. Mouse LMIR3 possesses five cytoplasmic tyrosine residues (Y241, Y276, Y289, Y303, Y325), among which Y241 and Y289 (Y241/289) or Y325 fit the consensus sequence of ITIM or immunotyrosine-based switch motif (ITSM), respectively. The inhibitory effect was abolished by the replacement of Y325 in addition to Y241/289 with phenylalanine (Y241/189/325/F) in accordance with the potential of Y241/289/325 to cooperatively recruit Src homology region 2 domain-containing phosphatase 1 (SHP)-1 or SHP-2. Intriguingly, LMIR3 crosslinking alone induced cytokine production in BMMCs expressing LMIR3 (Y241/276/289/303/325F) mutant as well as LMIR3 (Y241/289/325F). Moreover, coimmunoprecipitation experiments revealed that LMIR3 associated with ITAM-containing FcRgamma. Analysis of FcRgamma-deficient BMMCs demonstrated that both Y276/303 and FcRgamma played a critical role in the activating function of this inhibitory receptor. Importantly, LMIR3 crosslinking enhanced cytokine production of BMMCs stimulated by LPS, while suppressing production stimulated by other TLR agonists or stem cell factor. Thus, an inhibitory receptor LMIR3 has a unique property to associate with FcRgamma and thereby functions as an activating receptor in concert with TLR4 stimulation.
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http://dx.doi.org/10.4049/jimmunol.0900552DOI Listing
July 2009