RESUMO
Pathogen-specific antibody responses need to be tightly regulated to generate protective but limit self-reactive immune responses. While loss of humoral tolerance has been associated with microbial infections, the pathways involved in balancing protective versus autoreactive antibody responses in humans are incompletely understood. Studies in classical mouse model systems have provided evidence that balancing of immune responses through inhibitory receptors is an important quality control checkpoint. Genetic differences between inbred mouse models and the outbred human population and allelic receptor variants not present in mice; however, argue for caution when directly translating these findings to the human system. By studying Borrelia burgdorferi infection in humanized mice reconstituted with human hematopoietic stem cells from donors homozygous for a functional or a non-functional FcγRIIb allele, we show that the human inhibitory FcγRIIb is a critical checkpoint balancing protective and autoreactive immune responses, linking infection with induction of autoimmunity in the human immune system.
Assuntos
Anticorpos Antibacterianos/imunologia , Formação de Anticorpos/imunologia , Doença de Lyme/imunologia , Receptores de IgG/imunologia , Animais , Autoanticorpos/imunologia , Autoimunidade/imunologia , Borrelia burgdorferi/imunologia , Células-Tronco Hematopoéticas , Humanos , CamundongosRESUMO
Constitutive JAK2 signaling is central to myeloproliferative neoplasm (MPN) pathogenesis and results in activation of STAT, PI3K/AKT, and MEK/ERK signaling. However, the therapeutic efficacy of current JAK2 inhibitors is limited. We investigated the role of MEK/ERK signaling in MPN cell survival in the setting of JAK inhibition. Type I and II JAK2 inhibition suppressed MEK/ERK activation in MPN cell lines in vitro, but not in Jak2V617F and MPLW515L mouse models in vivo. JAK2 inhibition ex vivo inhibited MEK/ERK signaling, suggesting that cell-extrinsic factors maintain ERK activation in vivo. We identified PDGFRα as an activated kinase that remains activated upon JAK2 inhibition in vivo, and PDGF-AA/PDGF-BB production persisted in the setting of JAK inhibition. PDGF-BB maintained ERK activation in the presence of ruxolitinib, consistent with its function as a ligand-induced bypass for ERK activation. Combined JAK/MEK inhibition suppressed MEK/ERK activation in Jak2V617F and MPLW515L mice with increased efficacy and reversal of fibrosis to an extent not seen with JAK inhibitors. This demonstrates that compensatory ERK activation limits the efficacy of JAK2 inhibition and dual JAK/MEK inhibition provides an opportunity for improved therapeutic efficacy in MPNs and in other malignancies driven by aberrant JAK-STAT signaling.
Assuntos
Neoplasias Hematológicas/tratamento farmacológico , Janus Quinase 2/antagonistas & inibidores , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Mutação de Sentido Incorreto , Transtornos Mieloproliferativos/tratamento farmacológico , Proteínas de Neoplasias/antagonistas & inibidores , Inibidores de Proteínas Quinases/farmacologia , Substituição de Aminoácidos , Animais , Becaplermina/genética , Becaplermina/metabolismo , Linhagem Celular Tumoral , Sistemas de Liberação de Medicamentos , Neoplasias Hematológicas/enzimologia , Neoplasias Hematológicas/genética , Neoplasias Hematológicas/patologia , Humanos , Janus Quinase 2/genética , Janus Quinase 2/metabolismo , Sistema de Sinalização das MAP Quinases/genética , Camundongos , Transtornos Mieloproliferativos/enzimologia , Transtornos Mieloproliferativos/genética , Transtornos Mieloproliferativos/patologia , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , Fator de Crescimento Derivado de Plaquetas/genética , Fator de Crescimento Derivado de Plaquetas/metabolismo , Receptor alfa de Fator de Crescimento Derivado de Plaquetas/genética , Receptor alfa de Fator de Crescimento Derivado de Plaquetas/metabolismo , Receptor beta de Fator de Crescimento Derivado de Plaquetas/genética , Receptor beta de Fator de Crescimento Derivado de Plaquetas/metabolismo , Receptores de Trombopoetina/genética , Receptores de Trombopoetina/metabolismoRESUMO
Flt3 ligand (Flt3L) promotes survival of lymphoid progenitors in the bone marrow and differentiation of dendritic cells (DCs), but its role in regulating innate lymphoid cells (ILCs) during fetal and adult life is not understood. By using Flt3L knockout and transgenic mice, we demonstrate that Flt3L controls ILC numbers by regulating the pool of α4ß7(-) and α4ß7(+) lymphoid tissue inducer cell progenitors in the fetal liver and common lymphoid progenitors in the bone marrow. Deletion of flt3l severely reduced the number of fetal liver progenitors and lymphoid tissue inducer cells in the neonatal intestine, resulting in impaired development of Peyer's patches. In the adult intestine, NK cells and group 2 and 3 ILCs were severely reduced. This effect occurred independently of DCs as ILC numbers were normal in mice in which DCs were constitutively deleted. Finally, we could show that administration of Flt3L increased the number of NKp46(-) group 3 ILCs in wild-type and even in Il7(-/-) mice, which generally have reduced numbers of ILCs. Taken together, Flt3L significantly contributes to ILC and Peyer's patches development by targeting lymphoid progenitor cells during fetal and adult life.
Assuntos
Imunidade Inata/imunologia , Células Progenitoras Linfoides/imunologia , Linfopoese/imunologia , Proteínas de Membrana/imunologia , Nódulos Linfáticos Agregados/imunologia , Transferência Adotiva , Animais , Diferenciação Celular/imunologia , Separação Celular , Feto , Citometria de Fluxo , Imuno-Histoquímica , Células Progenitoras Linfoides/citologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Nódulos Linfáticos Agregados/citologiaRESUMO
Group 3 innate lymphoid cells (ILC3s) have emerged as important cellular players in tissue repair and innate immunity. Whether these cells meaningfully regulate adaptive immune responses upon activation has yet to be explored. Here we show that upon IL-1ß stimulation, peripheral ILC3s become activated, secrete cytokines, up-regulate surface MHC class II molecules, and express costimulatory molecules. ILC3s can take up latex beads, process protein antigen, and consequently prime CD4(+) T-cell responses in vitro. The cognate interaction of ILC3s and CD4(+) T cells leads to T-cell proliferation both in vitro and in vivo, whereas its disruption impairs specific T-cell and T-dependent B-cell responses in vivo. In addition, the ILC3-CD4(+) T-cell interaction is bidirectional and leads to the activation of ILC3s. Taken together, our data reveal a novel activation-dependent function of peripheral ILC3s in eliciting cognate CD4(+) T-cell immune responses.
Assuntos
Linfócitos T CD4-Positivos/imunologia , Interleucina-1beta/imunologia , Ativação Linfocitária/imunologia , Linfócitos/imunologia , Transdução de Sinais/imunologia , Animais , Apresentação de Antígeno/imunologia , Linfócitos B/imunologia , Linfócitos T CD4-Positivos/efeitos dos fármacos , Linfócitos T CD4-Positivos/metabolismo , Proliferação de Células/efeitos dos fármacos , Células Cultivadas , Citocinas/imunologia , Citocinas/metabolismo , Antígenos de Histocompatibilidade Classe II/imunologia , Imunidade Celular/imunologia , Interleucina-1beta/farmacologia , Ativação Linfocitária/efeitos dos fármacos , Linfócitos/efeitos dos fármacos , Linfócitos/metabolismo , Camundongos , Camundongos Endogâmicos C57BLRESUMO
Genetic differences between humans and in vivo model systems, including mice and nonhuman primates, make it difficult to predict the efficacy of immunoglobulin G (IgG) activity in humans and understand the molecular and cellular mechanisms underlying that activity. To bridge this gap, we established a small-animal model system that allowed us to study human IgG effector functions in the context of an intact human immune system without the interference of murine Fcγ receptors expressed on mouse innate immune effector cells in vivo. Using a model of B cell depletion with different human IgG variants that recognize CD20, we show that this humanized mouse model can provide unique insights into the mechanism of human IgG activity in vivo. Importantly, these studies identify the bone marrow as a niche with low therapeutic IgG activity.
Assuntos
Linfócitos B/imunologia , Medula Óssea/imunologia , Imunoglobulina G/imunologia , Receptores de IgG/imunologia , Animais , Humanos , Camundongos , Modelos AnimaisRESUMO
Maintenance of immunological tolerance is crucial to prevent development of autoimmune disease. The production of autoantibodies is a hallmark of many autoimmune diseases and studies in mouse model systems suggest that inhibitory signaling molecules may be important checkpoints of humoral tolerance. By generating humanized mice with normal and functionally impaired Fcγ receptor IIB (FcγRIIB) variants, we show that the inhibitory Fcγ-receptor is a checkpoint of humoral tolerance in the human immune system in vivo. Impaired human FcγRIIB function resulted in the generation of higher levels of serum immunoglobulins, the production of different autoantibody specificities, and a higher proportion of human plasmablasts and plasma cells in vivo. Our results suggest that the inhibitory FcγRIIB may be an important checkpoint of humoral tolerance in the human immune system.
Assuntos
Autoanticorpos/química , Lúpus Eritematoso Sistêmico/imunologia , Receptores de IgG/metabolismo , Animais , Variação Genética , Genótipo , Haplótipos , Homozigoto , Humanos , Sistema Imunitário , Imunidade Humoral , Imunoglobulina G/imunologia , Imunoglobulina M/imunologia , Imunoglobulinas/química , Camundongos , Camundongos Endogâmicos C57BL , Plasmócitos/citologiaRESUMO
Intravenous immunoglobulin (IVIg) has been used for nearly three decades as an efficient anti-inflammatory therapeutic regimen in a growing number of autoimmune diseases. Despite this their success in clinical application, the mechanism of action of IVIg therapy remains elusive. During the last few years, several mechanisms dependent on either the IgG variable or constant fragment have been proposed to explain the potent immunomodulatory activity of IVIg. This review will discuss which molecular and cellular pathways might be involved in the anti-inflammatory activity of IVIg and for which types of autoimmune diseases they might be relevant.
Assuntos
Anti-Inflamatórios não Esteroides/farmacologia , Doenças Autoimunes/tratamento farmacológico , Imunoglobulinas Intravenosas/farmacologia , Animais , Anti-Inflamatórios não Esteroides/uso terapêutico , Autoanticorpos/imunologia , Ensaios Clínicos como Assunto , Células Dendríticas/imunologia , Humanos , Imunoglobulina G/imunologia , Região Variável de Imunoglobulina/imunologia , Imunoglobulinas Intravenosas/uso terapêutico , Macrófagos/imunologia , Camundongos , Monócitos/imunologia , Ácido N-Acetilneuramínico/imunologia , Púrpura Trombocitopênica Idiopática/tratamento farmacológico , Ratos , Receptores Fc/imunologiaRESUMO
INTRODUCTION: The clinically known importance of patient sex as a major risk factor for compromised bone healing is poorly reflected in animal models. Consequently, the underlying cellular mechanisms remain elusive. Because mesenchymal stem cells (MSCs) are postulated to regulate tissue regeneration and give rise to essential differentiated cell types, they may contribute to sex-specific differences in bone healing outcomes. METHODS: We investigated sex-specific variations in bone healing and associated differences in MSC populations. A 1.5 mm osteotomy gap in the femora of 8 male and 8 female 12-month-old Sprague-Dawley rats was stabilized by an external fixator. Healing was analyzed in terms of biomechanical testing, bridging and callus size over time (radiography at 2, 4, and 6 weeks after surgery), and callus volume and geometry by microCT at final follow-up. MSCs were obtained from bone marrow samples of an age-matched group of 12 animals (6 per gender) and analyzed for numbers of colony-forming units (CFUs) and their capacity to differentiate and proliferate. The proportion of senescent cells was determined by beta-galactosidase staining. RESULTS: Sex-specific differences were indicated by a compromised mechanical competence of the callus in females compared with males (maximum torque at failure, p=0.028). Throughout the follow-up, the cross-sectional area of callus relative to bone was reduced in females (p< or =0.01), and the bridging of callus was delayed (p(2weeks)=0.041). microCT revealed a reduced callus size (p=0.003), mineralization (p=0.003) and polar moment of inertia (p=0.003) in female animals. The female bone marrow contained significantly fewer MSCs, represented by low CFU numbers in both femora and tibiae (p(femur)=0.017, p(tibia)=0.010). Functional characteristics of male and female MSCs were similar. CONCLUSION: Biomechanically compromised and radiographically delayed bone formation were distinctive in female rats. These differences were concomitant with a reduced number of MSCs, which may be causative for the suboptimal bone healing.
Assuntos
Osso e Ossos/patologia , Células-Tronco Mesenquimais/citologia , Caracteres Sexuais , Cicatrização , Animais , Fenômenos Biomecânicos , Osso e Ossos/diagnóstico por imagem , Calo Ósseo/diagnóstico por imagem , Calo Ósseo/patologia , Contagem de Células , Ensaio de Unidades Formadoras de Colônias , Feminino , Humanos , Masculino , Ratos , Ratos Sprague-Dawley , Microtomografia por Raio-XRESUMO
The inhibitory Fc-gamma receptor FcgammaRIIB, expressed on myeloid and B cells, has a critical role in the balance of tolerance and autoimmunity, and is required for the antiinflammatory activity of intravenous Ig (IVIG) in various murine disease models. However, the function of FcgammaRIIB and its regulation by IVIG in human autoimmune diseases are less well understood. Chronic inflammatory demyelinating polyneuropathy (CIDP) is the most common treatable acquired chronic polyneuropathy, and IVIG is widely used as a first-line initial and maintenance treatment. We found that untreated patients with CIDP, compared with demographically matched healthy controls, showed consistently lower FcgammaRIIB expression levels on naive B cells, and failed to up-regulate or to maintain up-regulation of FcgammaRIIB as B cells progressed from the naive to the memory compartment. Concomitantly, the rare -386C/-120A FcgammaRIIB promoter polymorphism resulting in reduced promoter activity previously associated with autoimmune phenotypes was overrepresented in CIDP. Also, FcgammaRIIB protein expression was up-regulated on monocytes and B cells after clinically effective IVIG therapy. Thus, our results suggest that the inhibitory FcgammaRIIB is impaired at a critical B cell differentiation checkpoint in CIDP, and that modulating FcgammaRIIB expression might be a promising approach to efficiently limit antibody-mediated immunopathology in CIDP.