RESUMEN
Epithelial tissues continually undergo apoptosis. Commensal organisms that inhabit the epithelium influence tissue homeostasis, in which regulatory T cells (Treg cells) have a central role. However, the physiological importance of epithelial cell apoptosis and how the number of Treg cells is regulated are both incompletely understood. Here we found that apoptotic epithelial cells negatively regulated the commensal-stimulated proliferation of Treg cells. Gut commensals stimulated CX3CR1(+)CD103(-)CD11b(+) dendritic cells (DCs) to produce interferon-ß (IFN-ß), which augmented the proliferation of Treg cells in the intestine. Conversely, phosphatidylserine exposed on apoptotic epithelial cells suppressed IFN-ß production by the DCs via inhibitory signaling mediated by the cell-surface glycoprotein CD300a and thus suppressed Treg cell proliferation. Our findings reveal a regulatory role for apoptotic epithelial cells in maintaining the number of Treg cell and tissue homeostasis.
Asunto(s)
Apoptosis/inmunología , Epidermis/inmunología , Células Epiteliales/inmunología , Microbioma Gastrointestinal/inmunología , Interferón beta/inmunología , Mucosa Intestinal/inmunología , Mucosa Respiratoria/inmunología , Linfocitos T Reguladores/inmunología , Alérgenos/toxicidad , Animales , Colitis/inducido químicamente , Colitis/inmunología , Colitis/patología , Colon/citología , Colon/inmunología , Células Dendríticas/inmunología , Dermatitis Alérgica por Contacto/etiología , Dermatitis Alérgica por Contacto/inmunología , Dermatitis Alérgica por Contacto/patología , Sulfato de Dextran/toxicidad , Células Epidérmicas , Citometría de Flujo , Inmunohistoquímica , Mucosa Intestinal/citología , Células de Langerhans/inmunología , Pulmón/citología , Pulmón/inmunología , Ratones , Ratones Noqueados , Ovalbúmina/toxicidad , Reacción en Cadena en Tiempo Real de la Polimerasa , Receptores Inmunológicos/genética , Mucosa Respiratoria/citología , Infecciones por Salmonella/inmunología , Salmonella typhimuriumRESUMEN
The intestinal barrier consists of mucosal, epithelial, and immunological barriers and serves as a dynamic interface between the host and its environment. Disruption of the intestinal barrier integrity is a leading cause of various gastrointestinal diseases, such as inflammatory bowel disease. The homeostasis of the intestinal barrier is tightly regulated by crosstalk between gut microbes and the immune system; however, the implication of the immune system on the imbalance of gut microbes that disrupts barrier integrity remains to be fully elucidated. An inhibitory immunoglobulin-like receptor, Allergin-1, is expressed on mast cells and dendritic cells and inhibits Toll-like receptor (TLR)-2 and TLR-4 signaling in these cells. Since TLRs are major sensors of microbiota and are involved in local epithelial homeostasis, we investigated the role of Allergin-1 in maintaining intestinal homeostasis. Allergin-1-deficient (Milr1-/-) mice exhibited more severe dextran sulfate sodium (DSS)-induced colitis than did wild-type (WT) mice. Milr1-/- mice showed an enhanced intestinal permeability compared with WT mice even before DSS administration. Treatment of Milr1-/- mice with neomycin, but not ampicillin, restored intestinal barrier integrity. The 16S rRNA gene sequencing analysis demonstrated that Bifidobacterium pseudolongum was the dominant bacterium in Milr1-/- mice after treatment with ampicillin. Although the transfer of B. pseudolongum to germ-free WT mice had no effect on intestinal permeability, its transfer into ampicillin-treated WT mice enhanced intestinal permeability. These results demonstrated that Allergin-1 deficiency enhanced intestinal dysbiosis with expanded B. pseudolongum, which contributes to intestinal barrier dysfunction in collaboration with neomycin-sensitive and ampicillin-resistant microbiota.
Asunto(s)
Disbiosis , Mucosa Intestinal , Ratones Endogámicos C57BL , Ratones Noqueados , Animales , Disbiosis/inmunología , Ratones , Mucosa Intestinal/inmunología , Mucosa Intestinal/microbiología , Mucosa Intestinal/metabolismo , Sulfato de Dextran , Microbioma Gastrointestinal/inmunología , Colitis/inmunología , Colitis/microbiología , Receptores Inmunológicos/metabolismo , Receptores Inmunológicos/genética , Receptores Inmunológicos/inmunología , Neomicina/farmacología , PermeabilidadRESUMEN
Anaphylaxis is a life-threatening immediate hypersensitivity reaction triggered by antigen capture by immunoglobulin E (IgE) bound to the high-affinity IgE receptor (FcvarepsilonRI) on mast cells. However, the regulatory mechanism of mast cell activation is not completely understood. Here we identify an immunoglobulin-like receptor, Allergin-1, that contains an immunoreceptor tyrosine-based inhibitory motif (ITIM)-like domain, and show it was preferentially expressed on mast cells. Mouse Allergin-1 recruited the tyrosine phosphatases SHP-1 and SHP-2 and the inositol phosphatase SHIP. Coligation of Allergin-1 and FcvarepsilonRI suppressed IgE-mediated degranulation of bone marrow-derived cultured mast cells. Moreover, mice deficient in Allergin-1 developed enhanced passive systemic and cutaneous anaphylaxis. Thus, Allergin-1 suppresses IgE-mediated, mast cell-dependent anaphylaxis in mice.
Asunto(s)
Degranulación de la Célula , Hipersensibilidad Inmediata/inmunología , Mastocitos/metabolismo , Anafilaxis Cutánea Pasiva/inmunología , Receptores Inmunológicos/metabolismo , Secuencia de Aminoácidos , Animales , Células de la Médula Ósea/patología , Células Cultivadas , Humanos , Hipersensibilidad Inmediata/genética , Hipersensibilidad Inmediata/metabolismo , Inmunoglobulina E/metabolismo , Inositol Polifosfato 5-Fosfatasas , Mastocitos/inmunología , Mastocitos/patología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Datos de Secuencia Molecular , Monoéster Fosfórico Hidrolasas/metabolismo , Proteína Tirosina Fosfatasa no Receptora Tipo 11/metabolismo , Proteína Tirosina Fosfatasa no Receptora Tipo 6/metabolismo , Agregación de Receptores/inmunología , Receptores de IgE/metabolismo , Receptores Inmunológicos/química , Receptores Inmunológicos/genética , Receptores Inmunológicos/inmunologíaRESUMEN
House dust mite (HDM) allergens are leading causes of allergic asthma characterized by Th2 responses. The lung-resident CD11b+ dendritic cells (DCs) play a key role in Th2 cell development in HDM-induced allergic asthma. However, the regulatory mechanism of HDM-induced CD11b+ DC activation remains incompletely understood. In this study, we demonstrate that mice deficient in an inhibitory immunoreceptor, Allergin-1, showed exacerbated HDM-induced airway eosinophilia and serum IgE elevation. By using bone marrow-chimeric mice that were sensitized with adoptively transferred HDM-stimulated wild-type or Allergin-1-deficient CD11b+ bone marrow-derived cultured DCs (BMDCs), followed by challenge with HDM, we show that Allergin-1 on the BMDCs suppressed HDM-induced allergic airway inflammation. We also show that Allergin-1 suppressed HDM-induced PGE2 production from CD11b+ BMDCs by inhibiting Syk tyrosine kinase activation through recruitment of SHP-1, subsequently leading to negative regulation of Th2 responses. These results suggest that Allergin-1 plays an important role in regulation of HDM-induced allergic airway inflammation.
Asunto(s)
Asma/inmunología , Hipersensibilidad/inmunología , Neumonía/inmunología , Pyroglyphidae/inmunología , Receptores Inmunológicos/inmunología , Animales , Células Dendríticas/inmunología , Ratones , Ratones Endogámicos BALB CRESUMEN
Although allergic contact dermatitis (ACD) is the most common T cell-mediated inflammatory responses against an allergen in the skin, the pathogenesis of ACD remains incompletely understood. In the sensitization phase in ACD, hapten-bearing dermal dendritic cells (DCs) play a pivotal role in the transport of an antigen to the lymph nodes (LNs), where they present the antigen to naïve T cells. Here we report that Allergin-1, an inhibitory immunoreceptor containing immunoreceptor tyrosine-based inhibitory motif (ITIM) in the cytoplasmic region, is highly expressed on dermal DCs. Mice deficient in Allergin-1 exhibited exacerbated fluorescein isothiocyanate (FITC)-induced type 2 contact hypersensitivity (CHS) such as ear swelling and skin eosinophilia. Allergin-1-deficient mice also showed larger numbers of CD4+ T cells and FITC-bearing DCs and greater expressions of type 2 cytokines, including IL-5, IL-10 and IL-13, in the draining LNs than did wild type mice. In sharp contrast, Allergin-1-deficient mice showed comparable level of type 1 CHS induced by 2,4-dinitrofluorobenzene (DNFB). These results suggest that Allergin-1 on dermal DC inhibits type 2, but not type 1, immune responses in the sensitization phase of CHS.
Asunto(s)
Células Dendríticas/metabolismo , Dermatitis por Contacto/metabolismo , Fluoresceína-5-Isotiocianato/química , Receptores Inmunológicos/fisiología , Piel/metabolismo , Animales , Linfocitos T CD4-Positivos/citología , Células Dendríticas/citología , Dinitrofluorobenceno/química , Femenino , Hipersensibilidad Inmediata , Interleucina-10/biosíntesis , Interleucina-13/biosíntesis , Interleucina-5/biosíntesis , Ratones , Ratones Endogámicos BALB C , Receptores Inmunológicos/metabolismoRESUMEN
Mast cells (MCs) are present in various organs including the skin, peritoneal cavity, lung, and intestine and involved in the development of allergic diseases and host defense against infection. However, the regulatory mechanism of mast cell activation remains incompletely understood. We found in a database that Clec12b encoding a C-type lectin receptor Clec12b is preferentially expressed in skin MCs in mice. However, neither MCs in other tissues such as trachea, tongue, esophagus, or peritoneal cavity nor most lymphocytes and myeloid cells express Clec12b. To analyze the protein expression of Clec12b, we newly generated a monoclonal antibody (named TX109), which recognizes both mouse and human Clec12b. Consistent with the gene expression profile, flow cytometry analysis demonstrated that Clec12b is expressed only on MCs in the skin, but not on any other immune cell types in various tissues, in mice. Similarly, Clec12b is also expressed on skin MCs, but not on circulating lymphocytes and myeloid cells, in humans. Our results suggest that Clec12b plays an important role in the regulation of MCs activation in the skin.
Asunto(s)
Anticuerpos Monoclonales/inmunología , Lectinas Tipo C/metabolismo , Mastocitos/metabolismo , Receptores Mitogénicos/metabolismo , Piel/metabolismo , Animales , Diferenciación Celular , Células Cultivadas , Citometría de Flujo/métodos , Humanos , Lectinas Tipo C/inmunología , Mastocitos/citología , Mastocitos/inmunología , Ratones , Receptores Mitogénicos/inmunología , Piel/citología , Piel/inmunologíaRESUMEN
Mast cells (MCs) play a critical role in oral allergen-induced anaphylaxis. However, the contribution of basophils to the anaphylaxis remains unclear. The inhibitory immunoreceptor Allergin-1 is highly expressed on MCs and basophils and inhibits FcεRI-mediated signaling in MCs. Here, we show that Allergin-1-deficient (Milr1-/-) mice developed more severe hypothermia, a higher mortality rate and a greater incidence of diarrhea than did wild-type (WT) mice in an oral ovalbumin (OVA)-induced food allergy model. MC-deficient Mas-TRECK mice, which had been reconstituted with either WT or Milr1-/- bone marrow-derived cultured MCs, did not develop hypothermia in this food allergy model. On the other hand, depletion of basophils by injection of anti-CD200R3 antibody rescued Milr1-/- mice from lethal hypothermia but not from diarrhea. In vitro analyses demonstrated that Allergin-1 inhibits IgE-dependent activation of both human and mouse basophils. Thus, Allergin-1 on basophils selectively suppresses oral allergen-induced anaphylaxis.
Asunto(s)
Anafilaxia/inmunología , Basófilos/inmunología , Receptores Inmunológicos/inmunología , Animales , Modelos Animales de Enfermedad , Femenino , Hipersensibilidad a los Alimentos/inmunología , Inmunoglobulina E/inmunología , Ratones , Ratones Endogámicos BALB C , Ratones Noqueados , Receptores Inmunológicos/administración & dosificación , Receptores Inmunológicos/deficienciaRESUMEN
Although airway hyperresponsiveness (AHR) is a prominent feature of asthma, how it is regulated remains incompletely understood. Allergin-1, an inhibitory immunoglobulin-like receptor containing an immunoreceptor tyrosine-based inhibitory motif (ITIM), is expressed on human and mouse mast cells (MCs) and inhibits high-affinity receptor for IgE (FcεRI)-mediated signaling. Using MC-deficient KitW-sh/W-sh mice and Mas-TRECK mice, which carries a diphtheria toxin (DT)-induced MC deletion system based on il4 enhancer elements, we demonstrate here that MCs are involved in the induction of house dust mite (HDM)-induced AHR. Further, we show that MCs deficient in Allergin-1 exacerbated HDM-induced AHR, but had no effect on airway inflammation. In vitro analysis demonstrated that Allergin-1 inhibited anti-HDM allergen antibody-dependent HDM allergen-mediated degranulation by MCs. Thus, Allergin-1 on MCs plays an important role in the regulation of HDM-induced AHR.
Asunto(s)
Mastocitos/inmunología , Pyroglyphidae/inmunología , Receptores Inmunológicos/inmunología , Hipersensibilidad Respiratoria/inmunología , Animales , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Hipersensibilidad Respiratoria/patologíaAsunto(s)
Anafilaxia , Basófilos , Humanos , Ratones , Animales , Alérgenos , Inmunoglobulina E , Inmunoglobulina G , MastocitosRESUMEN
Mast cells (MCs) play pivotal roles in allergic reactions and the host defense against microbial infection through the IgE-dependent and IgE-independent signaling pathways. MC lines that can be analyzed both in vitro and in vivo would be useful for the study of MC-dependent immune responses. Here, we investigated the functional characteristics of a mouse embryonic stem cell-derived MC-like cell line, MEDMC-BRC6. The cell line expressed FcεRI and c-Kit and showed degranulation and production of inflammatory cytokines and chemokines, including TNF-α, IL-6 and MCP-1, upon cross-linking FcεRI with IgE. These cytokines and chemokines were also produced by the cell line by stimulation of TLR2 and TLR4. MEDMC-BRC6 survived in the peritoneal cavity and the ear skin for at least 6 months after the transfer into genetically compatible MC-deficient KitW-sh/W-sh mice, in which systemic anaphylaxis was successfully induced. Thus, MEDMC-BRC6 cells represent a potent tool for investigating the functions of MCs in vitro and in vivo.
Asunto(s)
Anafilaxia/inmunología , Línea Celular/metabolismo , Mastocitos/metabolismo , Células Madre Embrionarias de Ratones/citología , Traslado Adoptivo , Animales , Degranulación de la Célula , Diferenciación Celular , Quimiocina CCL2/metabolismo , Inmunoglobulina E/inmunología , Interleucina-6/metabolismo , Mastocitos/citología , Mastocitos/trasplante , Ratones , Ratones Endogámicos C57BL , Ratones Mutantes , Proteínas Proto-Oncogénicas c-kit/genética , Receptores de IgG/metabolismo , Receptor Toll-Like 2/metabolismo , Receptor Toll-Like 4/metabolismo , Factor de Necrosis Tumoral alfa/metabolismoRESUMEN
TLR2 recognizes cell wall components of Staphylococcus aureus, which colonizes >90% of atopic eczematous skin lesions. The regulatory mechanisms of TLR2 signaling in the skin remain unclear. Allergin-1, an inhibitory immunoglobulin-like receptor containing an ITIM, is expressed on mast cells (MCs) and inhibits IgE-mediated anaphylaxis in mice. Here, we show that Allergin-1 inhibits TLR2-mediated activation of, and inflammatory cytokine production by, MCs in vitro Compared with wild-type mice, Allergin-1-deficient mice showed enhanced ear swelling with enhanced collagen deposition and greater Ly6G+ neutrophil recruitment after intra-dermal injection of Pam2CSK4 into pinnae. Using Mas-TRECK mice, which is an MC deletion system based on il4 enhancer elements, we also demonstrated that Allergin-1 on MCs is responsible for the Pam2CSK4-induced ear swelling. These results suggest that Allergin-1 on skin MCs suppresses TLR2-induced dermatitis.
Asunto(s)
Dermatitis/inmunología , Mastocitos/inmunología , Receptores Inmunológicos/inmunología , Receptor Toll-Like 2/antagonistas & inhibidores , Animales , Dermatitis/patología , Mastocitos/citología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Receptores Inmunológicos/deficiencia , Receptor Toll-Like 2/inmunologíaRESUMEN
Although Th1 and Th2 cells are known to be involved in allergic inflammatory diseases, the molecular mechanisms underlying their differentiation are incompletely understood. In this study, we identified CD155 as a costimulatory molecule on CD4(+) T cells. Importantly, CD155-mediated signaling induced Th1 development in both humans and mice, as evidenced by production of IFN-γ and upregulation of Tbx21 transcription; these effects were independent of IL-12 but dependent on NF-κB-induced autocrine IFN-γ that triggered positive feedback via STAT1 activation. Mice genetically deficient in CD155 or treated with anti-CD155 Ab exhibited attenuated Th1-type contact hypersensitivity. Thus, CD155 plays an important regulatory role in helper T cell differentiation and allergic diseases.
Asunto(s)
Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD4-Positivos/metabolismo , Hipersensibilidad/inmunología , Hipersensibilidad/metabolismo , Receptores Virales/metabolismo , Transducción de Señal , Animales , Anticuerpos Monoclonales/administración & dosificación , Anticuerpos Monoclonales/farmacología , Dermatitis por Contacto/tratamiento farmacológico , Dermatitis por Contacto/inmunología , Dermatitis por Contacto/metabolismo , Modelos Animales de Enfermedad , Humanos , Hipersensibilidad/tratamiento farmacológico , Interferón gamma/metabolismo , Interleucina-12/metabolismo , Ratones , Ratones Noqueados , Fosforilación , Receptores Virales/antagonistas & inhibidores , Receptores Virales/genética , Células TH1/inmunología , Células TH1/metabolismoRESUMEN
Recruitment of circulating monocytes and neutrophils to infection sites is essential for host defense against infections. Here, we identified a previously unannotated gene that encodes an immunoglobulin-like receptor, designated CD300H, which is located in the CD300 gene cluster. CD300H has a short cytoplasmic tail and associates with the signaling adaptor proteins, DAP12 and DAP10. CD300H is expressed on CD16(+) monocytes and myeloid dendritic cells. Ligation of CD300H on CD16(+) monocytes and myeloid dendritic cells with anti-CD300H monoclonal antibody induced the production of neutrophil chemoattractants. Interestingly, CD300H expression varied among healthy subjects, who could be classified into two groups according to "positive" and "negative" expression. Genomic sequence analysis revealed a single-nucleotide substitution (rs905709 (G â A)) at a splice donor site on intron 1 on either one or both alleles. The International HapMap Project database has demonstrated that homozygosity for the A allele of single nucleotide polymorphism (SNP) rs905709 ("negative" expression) is highly frequent in Han Chinese in Beijing, Japanese in Tokyo, and Europeans (A/A genotype frequencies 0.349, 0.167, and 0.138, respectively) but extremely rare in Sub-Saharan African populations. Together, these results suggest that CD300H may play an important role in innate immunity, at least in populations that carry the G/G or G/A genotype of CD300H.
Asunto(s)
Inmunidad Innata/inmunología , Familia de Multigenes , Receptores Inmunológicos/inmunología , Secuencia de Aminoácidos , Animales , Pueblo Asiatico/genética , Línea Celular Tumoral , Células Cultivadas , Citocinas/genética , Citocinas/inmunología , Citocinas/metabolismo , Células Dendríticas/inmunología , Células Dendríticas/metabolismo , Frecuencia de los Genes , Genotipo , Células HEK293 , Humanos , Inmunidad Innata/genética , Immunoblotting , Ratones , Datos de Secuencia Molecular , Neutrófilos/inmunología , Neutrófilos/metabolismo , Filogenia , Polimorfismo de Nucleótido Simple/genética , Polimorfismo de Nucleótido Simple/inmunología , Isoformas de Proteínas/genética , Isoformas de Proteínas/inmunología , Isoformas de Proteínas/metabolismo , Receptores Inmunológicos/genética , Receptores Inmunológicos/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Homología de Secuencia de Aminoácido , Células U937 , Población Blanca/genéticaRESUMEN
The recently identified cell surface immunoreceptor MILR1 (mast cell immunoglobulin-like receptor 1; synonyms, Allergin-1) has been shown to suppress immunoglobulin E (IgE)-mediated, mast cell-dependent responses in both mice and humans. We performed a mutation search of MILR1 together with a genetic association study to determine whether polymorphisms in MILR1 are associated with atopy in human. Mutation screening of MILR1 was performed using DNA from 146 unrelated Japanese. Genotyping of the identified polymorphisms was done with 1505 individuals from the general Japanese adult population. Atopy, as defined by positive responses for specific IgEs against at least one of the 26 common allergens, was evaluated using MAST-26. Five polymorphisms (rs6504230, c.-170_-166delAGGAA, rs8071835, rs143526766 and rs12936887) and two rare missense variants (Val273Ala and Leu311Val) were identified by mutation screening. The C allele of rs6504230 had protective effects against atopy (P=0.002). A luciferase reporter assay using the promoter region of MILR1 revealed that the C allele of rs6504230 was associated with increased expression of MILR1, which was in accordance with the results of expression quantitative trait loci analysis using human leukocytes. Our data indicates that the rs6504230 polymorphism affects MILR1 expression levels in humans, leading to a susceptibility to producing specific IgE antibodies against common allergens.
Asunto(s)
Expresión Génica , Hipersensibilidad Inmediata/genética , Polimorfismo de Nucleótido Simple , Regiones Promotoras Genéticas/genética , Receptores Inmunológicos/genética , Adulto , Anciano , Anciano de 80 o más Años , Alérgenos/inmunología , Estudios de Casos y Controles , Estudios Transversales , Análisis Mutacional de ADN , Frecuencia de los Genes , Genotipo , Células HEK293 , Humanos , Hipersensibilidad Inmediata/inmunología , Inmunoglobulina E/inmunología , Células K562 , Masculino , Persona de Mediana Edad , Mutación Missense , Fenotipo , Receptores Inmunológicos/inmunología , Adulto JovenRESUMEN
Acute graft-versus-host disease (GVHD) is a life-threatening complication following bone marrow transplantation; however, no effective molecular-targeting therapy has been determined. Here, we show that mice that received allogeneic splenocytes deficient in DNAX accessory molecule-1 (DNAM-1) had significantly milder GVHD and lower mortality than those that received allogeneic WT splenocytes. Donor CD8(+) T cells deficient in DNAM-1 showed significantly less proliferation and infiltration of the liver and intestines of recipient mice and produced less IFN-γ after coculture with allogeneic splenocytes than WT CD8(+) T cells. Mice prophylactically treated with an anti-DNAM-1 antibody showed milder GVHD and lower mortality than those treated with a control antibody. Moreover, treatment with a single administration of the antibody after the overt onset of GVHD ameliorated GVHD and prolonged survival. Finally, we show that the anti-DNAM-1 antibody therapy also ameliorated the overt GVHD in lethally irradiated mice after MHC-matched, minor antigen-mismatched bone marrow transplantation. These results indicate that DNAM-1 plays an important role in the development of GVHD and is an ideal molecular target for therapeutic approaches to GVHD.
Asunto(s)
Antígenos de Diferenciación de Linfocitos T/inmunología , Enfermedad Injerto contra Huésped/etiología , Enfermedad Injerto contra Huésped/inmunología , Enfermedad Aguda , Animales , Anticuerpos Monoclonales/uso terapéutico , Antígenos de Diferenciación de Linfocitos T/genética , Trasplante de Médula Ósea/efectos adversos , Trasplante de Médula Ósea/inmunología , Trasplante de Médula Ósea/patología , Linfocitos T CD4-Positivos/inmunología , Linfocitos T CD8-positivos/inmunología , Linfocitos T CD8-positivos/patología , Proliferación Celular , Femenino , Enfermedad Injerto contra Huésped/patología , Enfermedad Injerto contra Huésped/terapia , Interferón gamma/biosíntesis , Ligandos , Masculino , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C3H , Ratones Endogámicos C57BL , Ratones Noqueados , Trasplante HomólogoRESUMEN
CD300a is a member of CD300 family molecules consisting of seven genes on human chromosome 17 and nine genes in mouse chromosome 11. CD300a has a long cytoplasmic region containing the consensus immunoreceptor tyrosine-based inhibitory motif (ITIM) sequence. Upon crosslinking with antibodies against CD300a, CD300a mediates an inhibitory signal in myeloid cells. However, the ligand for CD300a has not been identified and the physiological role of CD300a remained unclear. Here, we demonstrate that the chimeric fusion protein of CD300a extracellular domain with the Fc portion of human IgG specifically bound phosphatidylserine (PS), which is exposed on the outer leaflet of the plasma membrane of apoptotic cells. PS binding to CD300a induced SHP-1 recruitment by CD300a in mast cells in response to LPS. These results indicated that CD300a is a new PS receptor.
Asunto(s)
Antígenos CD/inmunología , Fosfatidilserinas/inmunología , Receptores Inmunológicos/inmunología , Animales , Antígenos CD/química , Antígenos CD/genética , Membrana Celular/inmunología , Humanos , Fragmentos Fc de Inmunoglobulinas/química , Fragmentos Fc de Inmunoglobulinas/genética , Fragmentos Fc de Inmunoglobulinas/inmunología , Inmunoglobulina G/química , Inmunoglobulina G/genética , Inmunoglobulina G/inmunología , Células Jurkat , Ligandos , Mastocitos/inmunología , Ratones , Estructura Terciaria de Proteína , Receptores Inmunológicos/química , Receptores Inmunológicos/genética , Proteínas Recombinantes de Fusión/química , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/inmunologíaRESUMEN
IgM is an antibody class common to all vertebrates that plays a primary role in host defenses against infection. Binding of IgM with an antigen initiates the complement cascade, accelerating cellular and humoral immune responses. However, the functional role of the Fc receptor for IgM in such immune responses remains obscure. Here we show that mice deficient in Fc alpha/muR, an Fc receptor for IgM expressed on B cells and follicular dendritic cells (FDCs), have enhanced germinal center formation and affinity maturation and memory induction of IgG3(+) B cells after immunization with T-independent (TI) antigens. Moreover, Fc alpha/muR-deficient mice show prolonged antigen retention by marginal zone B (MZB) cells and FDCs. In vitro studies demonstrate that interaction of the IgM immune complex with Fc alpha/muR partly suppress TI antigen retention by MZB cells. We further show that downregulation of complement receptor (CR)1 and CR2 or complement deprivation by in vivo injection with anti-CR1/2 antibody or cobra venom factor attenuates antigen retention by MZB cells and germinal center formation after immunization with TI antigens in Fc alpha/muR(-/-) mice. Taken together, these results suggest that Fc alpha/muR negatively regulates TI antigen retention by MZB cells and FDCs, leading to suppression of humoral immune responses against T-independent antigens.
Asunto(s)
Formación de Anticuerpos/inmunología , Antígenos T-Independientes/inmunología , Receptores Fc/deficiencia , Receptores Fc/inmunología , Animales , Afinidad de Anticuerpos/inmunología , Especificidad de Anticuerpos/inmunología , Linfocitos B/citología , Linfocitos B/inmunología , Proteínas del Sistema Complemento/inmunología , Células Dendríticas Foliculares/citología , Células Dendríticas Foliculares/inmunología , Centro Germinal/citología , Centro Germinal/inmunología , Inmunización , Inmunoglobulina G/inmunología , Memoria Inmunológica , RatonesRESUMEN
Upon antigen recognition by the T cell receptor, lymphocyte function-associated antigen 1 (LFA-1) physically associates with the leukocyte adhesion molecule CD226 (DNAM-1) and the protein tyrosine kinase Fyn. We show that lentiviral vector-mediated mutant (Y-F322) CD226 transferred into naive CD4+ helper T cells (Ths) inhibited interleukin (IL)-12-independent Th1 development initiated by CD3 and LFA-1 ligations. Moreover, proliferation induced by LFA-1 costimulatory signal was suppressed in mutant (Y-F322) CD226-transduced naive CD4+ and CD8+ T cells in the absence of IL-2. These results suggest that CD226 is involved in LFA-1-mediated costimulatory signals for triggering naive T cell differentiation and proliferation. We also demonstrate that although LFA-1, CD226, and Fyn are polarized at the immunological synapse upon stimulation with anti-CD3 in CD4+ and CD8+ T cells, lipid rafts are polarized in CD4+, but not CD8+, T cells. Moreover, proliferation initiated by LFA-1 costimulatory signal is suppressed by lipid raft disruption in CD4+, but not CD8+, T cells, suggesting that the LFA-1 costimulatory signal is independent of lipid rafts in CD8+ T cells.