[show abstract][hide abstract] ABSTRACT: Plasmacytoid dendritic cells (PDCs) produce type I interferons (IFNs) in response to viral nucleic acids to exert antiviral immunity. However, PDCs are related to the progress and severity of autoimmune diseases, such as systemic lupus erythematosus, because they respond to host DNA. Therefore, the regulation of PDC activation is critical for maintaining adequate immune responses. Here we show that an inhibitory major histocompatibility complex class I receptor, paired immunoglobulin-like receptor B (PIR-B), suppressed Fms-like tyrosine kinase 3 ligand-induced PDC differentiation in BM cells, as well as Toll-like receptor 9-mediated IFN-α production by PDCs, through the dephosphorylation of STAT1/STAT2. In particular, PIR-B inhibited IFN-α-mediated STAT phosphorylation, suggesting that PIR-B negatively regulates the positive feedback mechanism of IFN-α secretion triggered by Toll-like receptor 9. These results demonstrate a novel regulatory role for PIR-B in PDCs.
[show abstract][hide abstract] ABSTRACT: The Runx1 transcription factor is abundantly expressed in naive T cells but rapidly downregulated in activated T cells, suggesting that it plays an important role in a naive stage. In the current study, Runx1(-/-)Bcl2(tg) mice harboring Runx1-deleted CD4(+) T cells developed a fatal autoimmune lung disease. CD4(+) T cells from these mice were spontaneously activated, preferentially homed to the lung, and expressed various cytokines, including IL-17 and IL-21. Among these, the deregulation of IL-21 transcription was likely to be associated with Runx binding sites located in an IL-21 intron. IL-17 produced in Runx1-deleted cells mobilized innate immune responses, such as those promoted by neutrophils and monocytes, whereas IL-21 triggered humoral responses, such as plasma cells. Thus, at an initial stage, peribronchovascular regions in the lung were infiltrated by CD4(+) lymphocytes, whereas at a terminal stage, interstitial regions were massively occupied by immune cells, and alveolar spaces were filled with granular exudates that resembled pulmonary alveolar proteinosis in humans. Mice suffered from respiratory failure, as well as systemic inflammatory responses. Our data indicate that Runx1 plays an essential role in repressing the transcription of cytokine genes in naive CD4(+) T cells and, thereby, maintains cell quiescence.
The Journal of Immunology 05/2012; 188(11):5408-20. · 5.52 Impact Factor
[show abstract][hide abstract] ABSTRACT: Cells in the immune system are regulated positively or negatively by sets of receptor pairs that conduct balanced, activating, or inhibitory intracellular signaling. One such receptor pair termed paired Ig-like receptor (PIR) is composed of the inhibitory PIR-B and its activating isoform, PIR-A. Upon binding to their shared ligand, MHC class I molecules, these receptors control the threshold for immune cell activation. Gene-targeting studies on PIR-B in mice revealed the importance of the inhibition mediated by the PIR-B-MHC interaction in the immune system. Recent studies also revealed the significance of the interaction of PIR-B with neurite outgrowth inhibitors, including Nogo in the CNS. The coordinated regulation by PIR-B and PIR-A is considered to be primarily dependent on their expression balance in cells. However, the mechanism underlying transcriptional control of the genes for PIR-B and PIR-A (Pirb and Pira, respectively) remains to be clarified. In this study, we identified the major cis-acting promoter segment for Pirb and Pira in B cells as the -212 to -117 region upstream from the translation initiation codon. PU.1 and Runx3 were found to bind to this Pirb promoter. Truncation of the PU.1-binding motif significantly reduced the promoter activity, whereas the influence of elimination of the Runx3 site was marginal in B lymphoma BCL1-B20 cells. Unexpectedly, PU.1, but not Runx3, knockdown reduced the levels of both the Pirb and Pira transcripts. We conclude that the major promoter of Pirb, and probably Pira as well, is activated dominantly by PU.1 and marginally by Runx3 in B cells.
The Journal of Immunology 06/2011; 186(12):7050-9. · 5.52 Impact Factor
[show abstract][hide abstract] ABSTRACT: Binding of class I MHC molecules (MHCI) to an inhibitory receptor, PIR-B, expressed on B cells and myeloid cells provides constitutive cellular inhibition, thus ensuring peripheral tolerance. Recent unexpected findings pointed to a novel inhibitory role of PIR-B in neurite regeneration through binding to three axonal outgrowth inhibitors of myelin, including Nogo. Thus, it becomes interesting to determine whether the actions of the inhibitory myelin proteins and MHCI could coexist independently or be mutually exclusive as to the PIR-B-mediated immune and neural cell inhibition. Here, we present data supporting the competition of Nogo- and MHCI-mediated inhibition where they coexist. Kinetic analyses of Nogo and MHCI binding to the whole or a part of the recombinant PIR-B ectodomain revealed that PIR-B binds with higher affinity to Nogo than MHCI and that the MHCI binding only occurred with the N-terminal domains of PIR-B, whereas Nogo binding occurred with either the N- or C-terminal ectodomains. Importantly, kinetic tests indicated that the binding to PIR-B of Nogo and MHCI was competitive. Both endogenous and exogenous Nogo intensified the PIR-B-mediated suppression of interleukin-6 release from lipopolysaccharide-stimulated wild-type, but not PIR-B-deficient, cultured mast cells, indicating that PIR-B mediates Nogo-induced inhibition. Thus, we propose a novel mechanism by which PIR-B-mediated regulation is achieved differentially but competitively via MHCI and Nogo in cells of the immune system.
Journal of Biological Chemistry 06/2011; 286(29):25739-47. · 4.65 Impact Factor
[show abstract][hide abstract] ABSTRACT: Binding of class I MHC molecules (MHCI) to an inhibitory receptor, PIR-B, expressed on B cells and myeloid cells provides
constitutive cellular inhibition, thus ensuring peripheral tolerance. Recent unexpected findings pointed to a novel inhibitory
role of PIR-B in neurite regeneration through binding to three axonal outgrowth inhibitors of myelin including Nogo. Thus,
it becomes interesting to determine whether the actions of the inhibitory myelin proteins and MHCI could coexist independently
or be mutually exclusive as to the PIR-B-mediated immune and neural cell inhibition. Here we present data supporting the competition
of Nogo- and MHCI-mediated inhibition where they coexist. Kinetic analyses of Nogo and MHCI binding to the whole or a part
of the recombinant PIR-B ectodomain revealed that PIR-B binds with higher affinity to Nogo than MHCI and that the MHCI binding
only occurred with the N-terminal domains of PIR-B, whereas the Nogo binding occurred with either the N- or C-terminal ectodomains.
Importantly, kinetic tests indicated that the binding to PIR-B of Nogo and MHCI was competitive. Both endogenous and exogenous
Nogo intensified the PIR-B-mediated suppression of interleukin-6 release from lipopolysaccharide-stimulated wild-type, but
not PIR-B-deficient, cultured mast cells, indicating that PIR-B mediates the Nogo-induced inhibition. Thus, we propose a novel
mechanism by which PIR-B-mediated regulation is achieved differentially but competitively via MHCI and Nogo in cells of the
Journal of Biological Chemistry 06/2011; · 4.65 Impact Factor
[show abstract][hide abstract] ABSTRACT: Paired immunoglobulin-like receptor B (PIR-B) partially mediates the regeneration-inhibiting effects of the myelin-derived protein Nogo, myelin-associated glycoprotein (MAG), and oligodendrocyte-myelin glycoprotein (OMgp). In this study, we report that inhibition of the PIR-B signaling cascades in neurons enhances axon regeneration in the central nervous system (CNS). Binding of MAG to PIR-B led to the association of PIR-B with tropomyosin receptor kinase (Trk) neurotrophin receptors. Src homology 2-containing protein tyrosine phosphatase (SHP)-1 and SHP-2, which were recruited to PIR-B upon MAG binding, functioned as Trk tyrosine phosphatases. Further, SHP-1 and SHP-2 inhibition reduced MAG-induced dephosphorylation of Trk receptors and abolished the inhibitory effect of MAG on neurite growth. Thus, PIR-B associated with Trk to downregulate basal and neurotrophin-regulated Trk activity through SHP-1/2 in neurons. Moreover, in vivo transfection of small interfering RNA (siRNA) for SHP-1 or SHP-2 induced axonal regeneration after optic nerve injury in mice. Our results thus identify a new molecular target to enhance regeneration of the injured CNS.
The EMBO Journal 03/2011; 30(7):1389-401. · 9.82 Impact Factor
[show abstract][hide abstract] ABSTRACT: The Nogo receptor and paired immunoglobulin-like receptor B (PIR-B) are receptors for three myelin-derived axon-growth inhibitors, including myelin-associated glycoprotein (MAG). In this study, we report that the p75 receptor is required for the signal transduction of PIR-B, which interacted with p75 upon ligand binding. In addition, p75 was required for activation of Src homology 2-containing protein tyrosine phosphatase (SHP), which is induced by MAG binding to PIR-B. Mice carrying a mutation in the p75 gene showed promotion of axonal regeneration after optic nerve injury. Thus, our results indicate that p75 has a critical role in axon growth inhibition in specific neuronal tracts.
Cell Death & Disease 01/2011; 2:e198. · 6.04 Impact Factor
[show abstract][hide abstract] ABSTRACT: PIR-B, an inhibitory receptor expressed on murine B cells and myeloid cells, regulates humoral and cellular immune responses via its constitutive binding to the ligand, MHC class I molecules, on the same cells (cis) or on different cells (trans). Although it has been speculated that PIR-B is important for maintaining peripheral tolerance, PIR-B single deficiency does not cause overt autoimmune diseases. Recently, however, the combination of its deficiency with the Fas lpr mutation was found to result in augmented production of autoantibodies such as IgG rheumatoid factor and anti-DNA IgG, leading to glomerulonephritis in mice. Although the precise molecular mechanism for the overall scenario is unclear, PIR-B was found to suppress TLR9-mediated production of naturally autoreactive antibodies by innate B cells or B-1 cells by inhibiting the activation of Bruton's tyrosine kinase. Thus, PIR-B is an important regulator of innate immunity mediated by TLR9 in B-1 cells, which can otherwise provoke autoimmunity when overactivated.
BioMed Research International 01/2011; 2011:275302. · 2.88 Impact Factor
[show abstract][hide abstract] ABSTRACT: Aqueous magnetic suspension was prepared by dispersing amphiphilic co-polymers coated monodispersed magnetite nanoparticles synthesized through thermal decomposition of iron(III) acetylacetonate (Fe(acac) 3) in the mixture of oleic acid and oleylamine. The average diameter of narrow size-distributed magnetite nanoparticles varied between 5 and 12 nm depending on the experimental parameters such as the ratio between Fe(acac) 3 and the oleic acid-oleylamine mixture and reaction temperature. Though the as-synthesized particles were coated with oleic acid and dispersible in organic solvent, their surfaces were modified using amphiphilic co-polymers composed of poly(maleic anhydride−alt−1−octadecene) and polyethylene glycol methyl ether and made dispersible in water. Infrared spectra of the sample indicated the existence of −COOH groups on the surface for further conjugation to biomolecules.
Journal of Magnetism and Magnetic Materials 01/2010; 323(10). · 1.83 Impact Factor
[show abstract][hide abstract] ABSTRACT: We report the results of the study undertaken to determine relative contributions of Néel and Brownian relaxations on magnetic heat dissipation by investigating the physical, magnetic and heating characteristics of magnetite suspension dispersing particles ranging in average diameter from 10.0 to 15.7 nm. Heating characteristics depended on the primary particle size and the viscosity of the medium. In the case of the sample with average diameter of 12.5 nm, the effective specific absorption rate dropped by 27% (22.9×10−9 to 16.8×10−9 Wg−1Oe−2Hz−1). In contrast, the decrease of 67% (29.5×10−9 to 9.7×10−9 Wg−1Oe−2Hz−1) was observed for the sample with average diameter of 15.7 nm. The potential of these particles as thermal seeds was tested by feeding the macrophage and exposing them to an alternative current magnetic field strength and frequency of 40 Oe and 600 kHz, respectively. The uptake of magnetite particles by the macrophage was adequate to raise the temperature of cell suspension b y 8 °C required for thermal necrosis.
[show abstract][hide abstract] ABSTRACT: Activated mature T cells induce various inhibitory receptors implicated in maintaining peripheral tolerance in response to the trans-acting ligands. Interestingly, paired Ig-like receptor (PIR)-B, an inhibitory MHC class I receptor on B cells and myeloid cells, could be involved in regulating early T cell development because epitope for PIR is detected on pre-thymic T/NK progenitors but not on thymocytes or mature T cells. We hypothesized that PIR-B is not only a regulator for T cell development but is also detrimental if expressed on mature T cells. Here we demonstrated, using PIR-B-deficient fetuses, that PIR-B is indeed expressed on the T cell progenitors but failed to identify its distinctive roles in the development. Forced expression of PIR-B in thymocytes and mature T cells also resulted in no abnormalities in development. However, upon antigenic or allogeneic stimulation, peripheral T cells with the ectopic PIR-B showed reduced T(h) type 1 responses due to the suppression of proximal TCR signaling by constitutive binding of PIR-B to MHC class I on the same cell surface. Our findings suggest that T cell expression of PIR-B with the cis-interacting MHC class I is strictly prohibited in periphery so as to secure prompt immune responses.
International Immunology 09/2009; 21(10):1151-61. · 3.14 Impact Factor
[show abstract][hide abstract] ABSTRACT: Osteoclasts, cells of myeloid lineage, play a unique role in bone resorption, maintaining skeletal homeostasis in concert with bone-producing osteoblasts. Osteoclast development and maturation (osteoclastogenesis) is driven by receptor activator of NF-kappaB ligand and macrophage-colony stimulating factor and invariably requires a signal initiated by immunoreceptor tyrosine-based activation motif (ITAM)-harboring Fc receptor common gamma chain or DNAX-activating protein (DAP)12 (also referred to as KARAP or TYROBP) that associates with the cognate immunoreceptors. Here, we show that a third adaptor, YINM costimulatory motif-harboring DAP10, triggers osteoclastogenesis and bone remodeling. DAP10-deficient (DAP10(-/-)) mice become osteopetrotic with age, concomitant with a reduction in osteoclasts. The DAP10-associating receptor was identified as myeloid DAP12-associating lectin-1 (MDL-1), whose physiologic function has not been found. MDL-1-mediated stimulation of osteoclast precursor cells resulted in augmented osteoclastogenesis in vitro. MDL-1 associates with both DAP12 and DAP10 in osteoclasts and bone marrow-derived macrophages, where DAP10 association depends almost entirely on DAP12, suggesting a formation of MDL-1-DAP12/DAP10 trimolecular complexes harboring ITAM/YINM stimulatory/costimulatory motifs within a complex that could be a novel therapeutic target for skeletal and inflammatory diseases.
Proceedings of the National Academy of Sciences 03/2009; 106(12):4816-21. · 9.74 Impact Factor
[show abstract][hide abstract] ABSTRACT: Osteoclasts, multinucleated cells of myeloid-monocytic origin, are responsible for bone resorption, which is crucial for maintenance of bone homeostasis in concert with bone-forming osteoblasts of nonhematopoietic, mesenchymal origin. Receptor activator of NF-kappaB ligand (RANKL) and M-CSF, expressed on the surface of and secreted by osteoblasts, respectively, are essential factors that facilitate osteoclast formation. In contrast to the activation processes for osteoclast formation, inhibitory mechanisms for it are poorly understood. Herein we demonstrate that inhibitory Ig-like receptors recruiting Src homology 2 domain-containing tyrosine phosphatase 1 (SHP-1) are expressed on osteoclast precursor cells like other myeloid cells, and that they play a regulatory role in the development of osteoclasts. We detected cell-surface expression of paired Ig-like receptor (PIR)-B and four isoforms of leukocyte Ig-like receptor (LILR)B on cultured osteoclast precursor cells of mouse and human origin, respectively, and showed that all of these ITIM-harboring inhibitory receptors constitutively recruit SHP-1 in the presence of RANKL and M-CSF, and that some of them can suppress osteoclast development in vitro. Fluorescence energy transfer analyses have suggested that the constitutive binding of either murine PIR-B or its human ortholog LILRB1 to MHC class I molecules on the same cell surface comprises one of the mechanisms for developmental regulation. These results constitute the first evidence of the regulation of osteoclast formation by cell-surface, ITIM-harboring Ig-like receptors. Modulation of these regulatory receptors may be a novel way to control various skeletal system disorders and inflammatory arthritis.
The Journal of Immunology 11/2008; 181(7):4742-51. · 5.52 Impact Factor
[show abstract][hide abstract] ABSTRACT: Priming of cytotoxic T lymphocytes (CTLs) by dendritic cells (DCs) is crucial for elimination of pathogens and malignant cells. To activate CTLs, DCs present antigenic peptide-complexed MHC class I molecules (MHC-I) that will be recognized by the CTLs with T cell receptors and CD8 molecules. Here we show that paired Ig-like receptor (PIR)-B, an MHC-I receptor expressed on antigen-presenting cells, can regulate CTL triggering by blocking the access of CD8 molecules to MHC-I. PIR-B-deficient DCs evoked CTLs more efficiently, leading to accelerated graft and tumor rejection. PIR-B(+) non-DC transfectant cells served as less efficient stimulators and targets for CTLs than PIR-B(-) cells at the effector phase in vitro. On surface plasmon resonance analysis, PIR-B and CD8alpha alpha were revealed to compete in binding to MHC-I. Our results may provide a novel strategy for regulating CTL-mediated immunity and diseases in a sterical manner.
Proceedings of the National Academy of Sciences 10/2008; 105(38):14515-20. · 9.74 Impact Factor
[show abstract][hide abstract] ABSTRACT: Dendritic cells (DC) play pivotal roles in the induction and regulation of both innate and acquired immunity. DC express several cell-surface immune inhibitory receptors. However, little is known about their potential immunoregulatory functions in the context of T-cell activation. Here we report that murine gp49B, a member of the immunoglobulin superfamily, harboring immunoreceptor tyrosine-based inhibitory motifs, is expressed on DC and downregulates cellular activity to prevent the excessive activation of T cells in vitro and in vivo. Bone marrow-derived DC (BMDC) from newly generated gp49B-deficient (gp49B(-/-)) mice induced enhanced proliferation and IL-2 release of antigen-specific CD4(+) and CD8(+) T cells compared with BMDC from wild-type mice, in a cell-cell contact manner. The enhanced proliferation by gp49B(-/-) BMDC was also observed in allogeneic CD4(+) and CD8(+) T cells. Moreover, the transfer of allogeneic BALB/c splenocytes into C57BL/6 gp49B(-/-) mice induced severe acute graft-versus-host disease with an augmented upregulation of CD86 on CD11c(+) splenic gp49B(-/-) DC, while transfer of C57BL/6 gp49B(-/-) splenocytes into BALB/c mice did not, suggesting the exacerbation of the disease was due, at least in part, to augmented activation of recipient gp49B(-/-) DC. These findings demonstrate a novel regulatory role of gp49B in the function of DC.
European Journal of Immunology 10/2008; 38(9):2426-37. · 4.97 Impact Factor
[show abstract][hide abstract] ABSTRACT: The uptake of an antigen and its presentation to specific T cells by dendritic cells (DCs) is a primary event in initiation of humoral and cellular immune responses as well as the induction of cytotoxic T cells (CTLs). DCs are induced by culturing bone marrow cells in the presence of GM-CSF. However, the resulting DCs are short-lived and the culture usually contains CD11c-negative non-DC cells, which adversely affects reproducibility and makes interpretation of the experimental results difficult. Therefore, it would be useful if DCs could be readily immortalized with their functions being retained. In this study we established a novel, immortalized murine DC line with antigen-presenting capacity in vitro as well as an augmenting effect on humoral and cellular immune responses in vivo, utilizing bone marrow cells from transgenic mice harboring the temperature-sensitive SV40 large T-antigen gene. In the presence of GM-CSF, the resulting DC line, termed SVDC, could be continuously subcultured for more than 12 months. When pulsed with OVA alone or OVA-IgG immune complexes via Fcgamma receptors, SVDC augmented OVA-specific T cell proliferation efficiently in vitro, and elicited OVA-specific IgG production in vivo on the adoptive transfer of pulsed SVDC into naive mice. Interestingly, SVDC exhibited significantly high cross-priming ability compared to DCs in a short-term culture, thus leading to their extremely high effectiveness in inducing anti-tumor immunity in vivo. Thus, SVDC is useful for the detailed characterization of antigen presentation, and for research on the various therapeutic benefits of DC vaccination to elicit specific immune responses in immunodeficiencies, infectious diseases and cancer.
Journal of Biochemistry 10/2004; 136(3):321-8. · 2.72 Impact Factor
[show abstract][hide abstract] ABSTRACT: It is well established that activating-type Fc receptors for IgG (FcgammaR), such as FcgammaRI and FcgammaRIII, are essential for inducing inflammatory responses, whereas a unique inhibitory FcgammaR, FcgammaRIIB, inhibits intracellular signaling upon ligation of IgG-immune complexes, and can suppress inflammation and autoimmunity. Although antigen presentation is a crucial step for evoking inflammatory responses, the contribution of FcgammaRIIB to antigen presentation is controversial as to whether it regulates antigen-presenting cells (APC), particularly dendritic cells (DC), positively or negatively. In the present report, we show that the antigen targeting to both activating-type FcgammaRs, FcgammaRI/III, and inhibitory FcgammaRIIB on bone marrow-derived DC and macrophages and primary epidermal Langerhans' cells augmented T cell proliferation in vitro and elicited humoral responses upon adoptive transfer of the antigen-pulsed DC. The DC lacking FcgammaRIIB showed a reduction in IC-uptake ability and a decreased T-cell stimulation, and induced less efficient IgG production than those of DC from wild-type mice. On the other hand, the DC lacking FcR common gamma subunit, which only expresses FcgammaRIIB, showed significant up-regulations of IC-uptake, T-cell proliferation, and IgG production compared to those of FcgammaR null DC, demonstrating a positive regulation of FcgammaRIIB for the efficient antigen presentation of IgG-complexed antigens. These results support the therapeutic benefits of antigen-targeting to FcgammaR on APC in the various inflammatory disorders.