RESUMO
Clearance of viral infections, such as SARS-CoV-2 and influenza A virus (IAV), must be fine-tuned to eliminate the pathogen without causing immunopathology. As such, an aggressive initial innate immune response favors the host in contrast to a detrimental prolonged inflammation. The complement pathway bridges innate and adaptive immune system and contributes to the response by directly clearing pathogens or infected cells, as well as recruiting proinflammatory immune cells and regulating inflammation. However, the impact of modulating complement activation in viral infections is still unclear. In this work, we targeted the complement decay-accelerating factor (DAF/CD55), a surface protein that protects cells from non-specific complement attack, and analyzed its role in IAV infections. We found that DAF modulates IAV infection in vivo, via an interplay with the antigenic viral proteins hemagglutinin (HA) and neuraminidase (NA), in a strain specific manner. Our results reveal that, contrary to what could be expected, DAF potentiates complement activation, increasing the recruitment of neutrophils, monocytes and T cells. We also show that viral NA acts on the heavily sialylated DAF and propose that the NA-dependent DAF removal of sialic acids exacerbates complement activation, leading to lung immunopathology. Remarkably, this mechanism has no impact on viral loads, but rather on the host resilience to infection, and may have direct implications in zoonotic influenza transmissions.
Assuntos
Antígenos CD55/fisiologia , Vírus da Influenza A Subtipo H1N1/isolamento & purificação , Pulmão/imunologia , Viremia/imunologia , Animais , Líquido da Lavagem Broncoalveolar/imunologia , Antígenos CD55/química , Antígenos CD55/deficiência , Quimiotaxia de Leucócito , Ativação do Complemento , Glicoproteínas de Hemaglutininação de Vírus da Influenza/fisiologia , Adaptação ao Hospedeiro , Especificidade de Hospedeiro , Interações Hospedeiro-Patógeno , Vírus da Influenza A Subtipo H1N1/enzimologia , Vírus da Influenza A Subtipo H1N1/patogenicidade , Vírus da Influenza A Subtipo H1N1/fisiologia , Interferon gama/análise , Pulmão/patologia , Pulmão/virologia , Camundongos , Camundongos Endogâmicos C57BL , Ácido N-Acetilneuramínico , Neuraminidase/fisiologia , Infecções por Orthomyxoviridae/imunologia , Infecções por Orthomyxoviridae/patologia , Carga Viral , Proteínas Virais/fisiologia , Virulência , Replicação Viral , Redução de PesoRESUMO
A role for NKT cells has been implicated in sepsis, but the mechanism by which NKT cells contribute to sepsis remains unclear. Here, we examined WT and NKT-cell-deficient mice of C57BL/6 background during cecal ligation and puncture-induced sepsis. The levels of C5a, IFN-γ, and IL-10 were higher in the serum and peritoneal fluid of WT mice than in those of CD1d(-/-) mice, while the mortality rate was lower in CD1d(-/-) mice than in WT mice. C5a blockade decreased mortality of WT mice during sepsis, whereas it did not alter that of CD1d(-/-) mice. As assessed by intracellular staining, NKT cells expressed IFN-γ, while neutrophils expressed IL-10. Upon coculture, IL-10-deficient NKT cells enhanced IL-10 production by WT, but not IFN-γR-deficient, neutrophils. Meanwhile, CD1d(-/-) mice exhibited high CD55 expression on neutrophils during sepsis, whereas those cells from WT mice expressed minimal levels of CD55. Recombinant IL-10 administration into CD1d(-/-) mice reduced CD55 expression on neutrophils. Furthermore, adoptive transfer of sorted WT, but not IFN-γ-deficient, NKT cells into CD1d(-/-) mice suppressed CD55 expression on neutrophils, but increased IL-10 and C5a levels. Taken together, IFN-γ-producing NKT cells enhance C5a generation via IL-10-mediated inhibition of CD55 expression on neutrophils, thereby exacerbating sepsis.
Assuntos
Antígenos CD55/fisiologia , Complemento C5a/biossíntese , Interferon gama/fisiologia , Interleucina-10/fisiologia , Células T Matadoras Naturais/imunologia , Neutrófilos/imunologia , Sepse/imunologia , Animais , Antígenos CD1d/fisiologia , Complemento C5a/análise , Camundongos , Camundongos Endogâmicos C57BLRESUMO
CD55 is a glycosylphosphatidylinositol-anchored protein, which inhibits complement activation by acting on the complement C3 convertases. CD55 is widely localized in the cholesterol rich regions of the cell plasma membrane termed membrane rafts. CD55 is attached to these specialized regions via a GPI link on the outer leaflet of the plasma membrane. Membrane rafts anchor many important signaling proteins, which control several cellular functions within the cell. For example, we recently demonstrated that the membrane raft protein and complement inhibitor CD59 also controls insulin secretion by an intracellular mechanism. Therefore, we have in this study aimed at addressing the expression and function of CD55 in pancreatic beta cells. To this end, we observe that CD55 is highly expressed in INS1 832/13 beta cells as well as human pancreatic islets. Diabetic human islets show a tendency for increased expression of CD55 when compared to the healthy controls. Importantly, silencing of CD55 in INS1 832/13 cells does not affect their insulin secretory capacity. On the other hand, silencing of CD55 diminished the intensity of membrane rafts as determined by Atto-SM staining. We hence conclude that CD55 expression is affected by glycemic status in human islets and plays a critical role in maintaining the conserved structure of rafts in pancreatic islets, which is similar to that of the related complement inhibitor CD59. However CD55 does not interfere with insulin secretion in beta cells, which is in sharp contrast to the action of the complement inhibitor CD59.
Assuntos
Antígenos CD55/fisiologia , Insulina/metabolismo , Ilhotas Pancreáticas/metabolismo , Microdomínios da Membrana/metabolismo , Animais , Antígenos CD55/genética , Linhagem Celular , Perfilação da Expressão Gênica , Humanos , Secreção de Insulina , RatosRESUMO
CC chemokine ligand 2 (CCL2) recruits macrophages to reduce inflammatory responses. Decay-accelerating factor (DAF) is a membrane regulator of the classical and alternative pathways of complement activation. In view of the link between complement genes and retinal diseases, we evaluated the retinal phenotype of C57BL/6J mice and mice lacking Ccl2 and/or Daf1 at 12 months of age, using scanning laser ophthalmoscopic imaging, electroretinography (ERG), histology, immunohistochemistry, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) analysis. In comparison to C57BL/6J mice, mutant mice had an increased number of autofluorescent foci, with the greatest number in the Ccl2(-/-)/Daf1(-/-) retina. ERG amplitudes in Ccl2(-/-)/Daf1(-/-), Ccl2(-/-) and Daf1(-/-) mice were reduced, with the greatest reduction in Ccl2(-/-)/Daf1(-/-) mice. TUNEL-positive cells were not seen in C57BL/6J retina, but were prevalent in the outer and inner nuclear layers of Ccl2(-/-)Daf1(-/-) mice and were present at reduced density in Ccl2(-/-) or Daf1(-/-) mice. Cell loss was most pronounced in the outer and inner nuclear layers of Ccl2(-/-)/Daf1(-/-) mice. The levels of the endoplasmic reticulum chaperone GPR78 and transcription factor ATF4 were significantly increased in the Ccl2(-/-)/Daf1(-/-) retina. In comparison to the C57BL/6J retina, the phosphorylation of NF-κB p65, p38, ERK and JNK was significantly upregulated while SIRT1 was significantly downregulated in the Ccl2(-/-)/Daf1(-/-) retina. Our results suggest that loss of Ccl2 and Daf1 causes retinal neuronal death and degeneration which is related to increased endoplasmic reticulum stress, oxidative stress and inflammation.
Assuntos
Antígenos CD55/fisiologia , Quimiocina CCL2/fisiologia , Degeneração Retiniana/etiologia , Degeneração Retiniana/fisiopatologia , Neurônios Retinianos/patologia , Fator 4 Ativador da Transcrição/metabolismo , Animais , Apoptose , Modelos Animais de Doenças , Eletrorretinografia , Chaperona BiP do Retículo Endoplasmático , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Proteínas de Choque Térmico/metabolismo , Imuno-Histoquímica , Marcação In Situ das Extremidades Cortadas , Proteínas Quinases JNK Ativadas por Mitógeno/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , NF-kappa B/metabolismo , Degeneração Retiniana/metabolismo , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
Enveloped viruses can incorporate host cell membrane proteins during the budding process. Here we demonstrate that mumps virus (MuV) and vesicular stomatitis virus (VSV) assemble to include CD46 and CD55, two host cell regulators which inhibit propagation of complement pathways through distinct mechanisms. Using viruses which incorporated CD46 alone, CD55 alone, or both CD46 and CD55, we have tested the relative contribution of these regulators in resistance to complement-mediated neutralization. Virion-associated CD46 and CD55 were biologically active, with VSV showing higher levels of activity of both cofactors, which promoted factor I-mediated cleavage of C3b into iC3b as well as decay-accelerating factor (DAF) activity against the C3 convertase, than MuV. Time courses of in vitro neutralization with normal human serum (NHS) showed that both regulators could delay neutralization, but viruses containing CD46 alone were neutralized faster and more completely than viruses containing CD55 alone. A dominant inhibitory role for CD55 was most evident for VSV, where virus containing CD55 alone was not substantially different in neutralization kinetics from virus harboring both regulators. Electron microscopy showed that VSV neutralization proceeded through virion aggregation followed by lysis, with virion-associated CD55 providing a delay in both aggregation and lysis more substantial than that conferred by CD46. Our results demonstrate the functional significance of incorporation of host cell factors during virion envelope assembly. They also define pathways of virus complement-mediated neutralization and suggest the design of more effective viral vectors.
Assuntos
Antígenos CD55/fisiologia , Ativação do Complemento/fisiologia , Proteína Cofatora de Membrana/fisiologia , Vírus da Caxumba/imunologia , Vesiculovirus/imunologia , Animais , Antígenos CD55/genética , Células CHO , Ativação do Complemento/genética , Cricetinae , Cricetulus , Interações Hospedeiro-Patógeno/imunologia , Humanos , Proteína Cofatora de Membrana/genética , Microscopia Imunoeletrônica , Vírus da Caxumba/fisiologia , Vírus da Caxumba/ultraestrutura , Testes de Neutralização , Vesiculovirus/fisiologia , Vesiculovirus/ultraestrutura , Montagem de VírusRESUMO
The essential event in picornavirus entry is the delivery of the RNA genome to the cytoplasm of a target cell, where replication occurs. In the past several years progress has been made in understanding the structural changes in the virion important for uncoating and RNA release. In addition, for several viruses the endocytic mechanisms responsible for internalization have been identified, as have the cellular sites at which uncoating occurs. It has become clear that entry is not a passive process, and that viruses initiate specific signals required for entry. And we have begun to recognize that for a given virus, there may be multiple routes of entry, depending on the particular target cell and the receptors available on that cell.
Assuntos
Picornaviridae/fisiologia , Internalização do Vírus , Animais , Antígenos CD55/fisiologia , Proteína de Membrana Semelhante a Receptor de Coxsackie e Adenovirus/fisiologia , Endocitose , Humanos , Picornaviridae/ultraestrutura , Receptores Virais/fisiologia , Ligação ViralRESUMO
For the last two decades, there had been remarkable advancement in understanding the role of complement regulatory proteins in autoimmune disorders and importance of complement inhibitors as therapeutics. Systemic lupus erythematosus is a prototype of systemic autoimmune disorders. The disease, though rare, is potentially fatal and afflicts women at their reproductive age. It is a complex disease with multiorgan involvement, and each patient presents with a different set of symptoms. The diagnosis is often difficult and is based on the diagnostic criteria set by the American Rheumatology Association. Presence of antinuclear antibodies and more specifically antidouble-stranded DNA indicates SLE. Since the disease is multifactorial and its phenotypes are highly heterogeneous, there is a need to identify multiple noninvasive biomarkers for SLE. Lack of validated biomarkers for SLE disease activity or response to treatment is a barrier to the efficient management of the disease, drug discovery, as well as development of new therapeutics. Recent studies with gene knockout mice have suggested that membrane-bound complement regulatory proteins (CRPs) may critically determine the sensitivity of host tissues to complement injury in autoimmune and inflammatory disorders. Case-controlled and followup studies carried out in our laboratory suggest an intimate relation between the level of DAF, MCP, CR1, and CD59 transcripts and the disease activity in SLE. Based on comparative evaluation of our data on these four membrane-bound complement regulatory proteins, we envisaged CR1 and MCP transcripts as putative noninvasive disease activity markers and the respective proteins as therapeutic targets for SLE. Following is a brief appraisal on membrane-bound complement regulatory proteins DAF, MCP, CR1, and CD59 as biomarkers and therapeutic targets for SLE.
Assuntos
Proteínas do Sistema Complemento/efeitos dos fármacos , Proteínas do Sistema Complemento/fisiologia , Lúpus Eritematoso Sistêmico/tratamento farmacológico , Proteínas de Membrana/efeitos dos fármacos , Proteínas de Membrana/fisiologia , Animais , Biomarcadores , Antígenos CD55/fisiologia , Antígenos CD59/efeitos dos fármacos , Antígenos CD59/fisiologia , Humanos , Proteína Cofatora de Membrana/antagonistas & inibidores , Proteína Cofatora de Membrana/fisiologia , Receptores de Complemento/antagonistas & inibidores , Receptores de Complemento/fisiologiaRESUMO
In this chapter, we present a concise historic prospective and a summary of accumulated knowledge on steroid hormones, DAF expression, and therapeutic implication of steroid hormone treatment on multiple pathologies, including infection and the host-pathogen interactions. DAF/CD55 plays multiple physiologic functions including tissue protection from the cytotoxic complement injury, an anti-inflammatory function due to its anti-adherence properties which enhance transmigration of monocytes and macrophages and reduce tissue injury. DAF physiologic functions are essential in many organ systems including pregnancy for protection of the semiallogeneic fetus or for preventing uncontrolled infiltration by white cells in their pro- and/or anti-inflammatory functions. DAF expression appears to have multiple regulatory tissue-specific and/or menstrual cycle-specific mechanisms, which involve complex signaling mechanisms. Regulation of DAF expression may involve a direct or an indirect effect of at least the estrogen, progesterone, and corticosteroid regulatory pathways. DAF is exploited in multiple pathologic conditions by pathogens and viruses in chronic tissue infection processes. The binding of Escherichia coli bearing Dr adhesins to the DAF/CD55 receptor is DAF density dependent and triggers internalization of E. coli via an endocytic pathway involving CD55, lipid rafts, and microtubules. Dr+ E. coli or Dr antigen may persist in vivo in the interstitium for several months. Further understanding of such processes should be instrumental in designing therapeutic strategies for multiple conditions involving DAF's protective or pathologic functions and tailoring host expression of DAF.
Assuntos
Antígenos CD55/fisiologia , Interações Hospedeiro-Patógeno/efeitos dos fármacos , Esteroides/farmacologia , Esteroides/uso terapêutico , Adulto , Animais , Antígenos CD55/biossíntese , Antígenos CD55/efeitos dos fármacos , Proteínas do Sistema Complemento/imunologia , Feminino , Terapia de Reposição Hormonal , Humanos , Nefropatias/complicações , Óxido Nítrico/fisiologia , Trabalho de Parto Prematuro , Comunicação Parácrina/fisiologia , Gravidez , Progesterona/fisiologia , Esteroides/fisiologiaRESUMO
Generation of the alternative pathway C3-convertase, the central amplification enzyme of the complement cascade, initiates by the binding of factor B (fB) to C3b to form the proconvertase, C3bB. C3bB is subsequently cleaved by factor D (fD) at a single site in fB, producing Ba and Bb fragments. Ba dissociates from the complex, while Bb remains bound to C3b, forming the active alternative pathway convertase, C3bBb. Using single-particle electron microscopy we have determined the 3-dimensional structures of the C3bB and the C3bBb complexes at approximately 27A resolution. The C3bB structure shows that fB undergoes a dramatic conformational change upon binding to C3b. However, the C3b-bound fB structure was easily interpreted after independently fitting the atomic structures of the isolated Bb and Ba fragments. Interestingly, the divalent cation-binding site in the von Willebrand type A domain in Bb faces the C345C domain of C3b, whereas the serine-protease domain of Bb points outwards. The structure also shows that the Ba fragment interacts with C3b separately from Bb at the level of the alpha'NT and CUB domains. Within this conformation, the long and flexible linker between Bb and Ba is likely exposed and accessible for cleavage by fD to form the active convertase, C3bBb. The architecture of the C3bB and C3bBb complexes reveals that C3b could promote cleavage and activation of fB by actively displacing the Ba domain from the von Willebrand type A domain in free fB. These structures provide a structural basis to understand fundamental aspects of the activation and regulation of the alternative pathway C3-convertase.
Assuntos
C3 Convertase da Via Alternativa do Complemento/metabolismo , Complemento C3b/química , Fator B do Complemento/química , Antígenos CD55/fisiologia , C3 Convertase da Via Alternativa do Complemento/química , Fator H do Complemento/fisiologia , Precursores Enzimáticos/química , Humanos , Imageamento Tridimensional , Microscopia Eletrônica , Conformação Proteica , Estrutura Terciária de Proteína , Receptores de Complemento 3b/fisiologiaRESUMO
In the January 13 issue of Cell, Coyne and Bergelson describe an "Open sesame!" strategy developed by coxsackieviruses to invade the organism through the intestinal epithelium. The strategy involves coopting intrinsic signaling abilities of the apical GPI-anchored protein DAF to open the tight junction barrier, gain access to the primary receptor CAR, and activate virus internalization by a caveolin-dependent pathway.
Assuntos
Enterovirus Humano B/patogenicidade , Junções Íntimas/virologia , Sítios de Ligação , Antígenos CD55/fisiologia , Humanos , Mucosa Intestinal/virologia , Modelos BiológicosRESUMO
A major obstacle to gene transduction by viral vectors is inactivation by human complement in vivo. One way to overcome this is to incorporate complement regulatory proteins, such as CD55/decay accelerating factor (DAF), into viral particles. Lentivirus vectors pseudotyped with the baculovirus envelope protein GP64 have been shown to acquire more potent resistance to serum inactivation and longer transgene expression than those pseudotyped with the vesicular stomatitis virus (VSV) envelope protein G. However, the molecular mechanisms underlying resistance to serum inactivation in pseudotype particles bearing the GP64 have not been precisely elucidated. In this study, we generated pseudotype and recombinant VSVs bearing the GP64. Recombinant VSVs generated in human cell lines exhibited the incorporation of human DAF in viral particles and were resistant to serum inactivation, whereas those generated in insect cells exhibited no incorporation of human DAF and were sensitive to complement inactivation. The GP64 and human DAF were detected on the detergent-resistant membrane and were coprecipitated by immunoprecipitation analysis. A pseudotype VSV bearing GP64 produced in human DAF knockdown cells reduced resistance to serum inactivation. In contrast, recombinant baculoviruses generated in insect cells expressing human DAF or carrying the human DAF gene exhibited resistance to complement inactivation. These results suggest that the incorporation of human DAF into viral particles by interacting with baculovirus GP64 is involved in the acquisition of resistance to serum inactivation.
Assuntos
Baculoviridae/genética , Antígenos CD55/genética , Proteínas Inativadoras do Complemento/genética , Proteínas Virais de Fusão/genética , Vírion/fisiologia , Animais , Bombyx , Antígenos CD55/fisiologia , Células Cultivadas , Proteínas Inativadoras do Complemento/fisiologia , Terapia Genética , Glicosilação , Humanos , Spodoptera , Vírus da Estomatite Vesicular Indiana/genéticaRESUMO
Complement activation is thought to contribute to the pathogenesis of preterm labor (PTL). Decay-accelerating factor (DAF) is a natural complement pathway inhibitor. Our hypothesis was that DAF expression on maternal white blood cells (WBCs) in women with preterm labor is elevated compared with women with no preterm labor. Our secondary objective was to determine if differences in upregulation of DAF levels correlated with clinical outcomes. Serial blood samples were obtained from 30 patients with a clinical diagnosis of PTL and a control group of 30 pregnant individuals (same gestational age range) to determine DAF expression in peripheral WBCs in both groups. DAF expression was higher in women with PTL (less than 37 weeks) compared with the control group without PTL. Subjects with PTL who delivered before 34 weeks had less DAF expression and different kinetics of expression compared with those carrying pregnancies beyond 34 weeks. These data suggest that women with a clinical diagnosis of preterm labor have increased DAF expression on peripheral WBCs. Furthermore, it appears that failure to elevate DAF expression is associated with a risk of early premature delivery.
Assuntos
Antígenos CD55/fisiologia , Ativação do Complemento/fisiologia , Trabalho de Parto Prematuro/fisiopatologia , Adulto , Antígenos CD55/metabolismo , Feminino , Idade Gestacional , Humanos , Leucócitos/metabolismo , Trabalho de Parto Prematuro/metabolismo , Gravidez , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Regulação para Cima/fisiologia , Adulto JovemRESUMO
Neutrophil migration across mucosal epithelium during inflammatory episodes involves the precise orchestration of a number a cell surface molecules and signaling pathways. After successful migration to the apical epithelial surface, apically localized epithelial proteins may serve to retain PMN at the lumenal surface. At present, identification of apical epithelial ligands and their PMN counter-receptors remain elusive. Therefore, to define the existence of apical epithelial cell surface proteins involved in PMN-epithelial interactions, we screened a panel of antibodies directed against epithelial plasma membranes. This strategy identified one antibody (OE-1) that both localized to the apical cell membrane and significantly inhibited PMN transmigration across epithelial monolayers. Microsequence analysis revealed that OE-1 recognized human decay-accelerating factor (DAF, CD55). DAF is a highly glycosylated, 70-80-kD, glycosyl-phosphatidyinositol-linked protein that functions predominantly as an inhibitor of autologous complement lysis. DAF suppression experiments using antisense oligonucleotides or RNA interference revealed that DAF may function as an antiadhesive molecule promoting the release of PMN from the lumenal surface after transmigration. Similarly, peptides corresponding to the antigen recognition domain of OE-1 resulted in accumulation of PMN on the apical epithelial surface. The elucidation of DAF as an apical epithelial ligand for PMN provides a target for novel anti-inflammatory therapies directed at quelling unwanted inflammatory episodes.
Assuntos
Antígenos CD55/fisiologia , Neutrófilos/fisiologia , Sequência de Aminoácidos , Sítios de Ligação , Antígenos CD55/química , Adesão Celular , Movimento Celular , Células Cultivadas , Células Epiteliais/fisiologia , Humanos , Dados de Sequência Molecular , Mucosa/citologiaRESUMO
PURPOSE: There is increasing evidence that ischemic postconditioning may noticeably attenuate renal ischemic-reperfusion injury, although the specific mechanisms are not fully clear. We examined the role of the complement system, especially membrane bound complement regulatory proteins, in postconditioning after renal ischemic-reperfusion injury in a right nephrectomy rat model. MATERIALS AND METHODS: After right nephrectomy the left renal pedicles were occluded for 60 minutes, followed by 24-hour reperfusion. Postconditioning was induced by 6 cycles of 10-second ischemia and 10-second reperfusion before reperfusion. After 24-hour reperfusion without a control blood samples were obtained via the vena cava. Renal samples were also obtained. DAF, CD46, CD59, C3aR and C5aR mRNA and protein expression was examined by reverse transcriptase-polymerase chain reaction, Western blot and immunohistochemistry. C3/C9 deposition in tissue was detected by immunofluorescence. Renal function, histology and cellular apoptosis were also observed. RESULTS: In renal tissue postconditioning prevents DAF down-regulation, which is induced by ischemic-reperfusion injury. It results in the decreased renal necrosis caused by ischemic-reperfusion injury mediated complement activation. However, in all experimental groups renal CD46/CD59 expression was not altered. Increased DAF expression due to postconditioning may decrease C5aR expression in renal tissues compared with ischemic-reperfusion injury, which can decrease apoptosis. C3aR expression did not differ among the experimental groups. CONCLUSIONS: These findings provide new evidence that postconditioning protects kidneys from ischemic-reperfusion injury, at least in part, by preventing DAF down-regulation.
Assuntos
Antígenos CD55/fisiologia , Regulação para Baixo , Rim/irrigação sanguínea , Traumatismo por Reperfusão/prevenção & controle , Animais , Masculino , Ratos , Ratos WistarRESUMO
Complement activation on human platelets is known to cause platelet degranulation and activation. To evaluate how normal platelets escape complement attack in vivo, we studied the fate of murine platelets deficient in 2 membrane complement regulatory proteins using an adoptive transfer model. We show here that deficiency of either decay-accelerating factor (DAF) or complement receptor 1-related gene/protein y (Crry) on murine platelets was inconsequential, whereas DAF and Crry double deficiency led to rapid clearance of platelets from circulation in a complement- and macrophage-dependent manner. This finding contrasted with the observation on erythrocytes, where Crry deficiency alone resulted in complement susceptibility. Quantitative flow cytometry showed DAF and Crry were expressed at similar levels on platelets, whereas Crry expression was 3 times higher than DAF on erythrocytes. Antibody blocking or gene ablation of the newly identified complement receptor CRIg, but not complement receptor 3 (CR3), rescued DAF/Crry-deficient platelets from complement-dependent elimination. Surprisingly, deficiency of CRIg, CR3, and other known complement receptors failed to prevent Crry-deficient erythrocytes from complement-mediated clearance. These results show a critical but redundant role of DAF and Crry in platelet survival and suggest that complement-opsonized platelets and erythrocytes engage different complement receptors on tissue macrophages in vivo.
Assuntos
Plaquetas/imunologia , Antígenos CD55/fisiologia , Macrófagos/imunologia , Fagocitose , Receptores de Complemento/fisiologia , Animais , Sobrevivência Celular , Ativação do Complemento , Proteínas do Sistema Complemento , Eritrócitos/imunologia , Camundongos , Receptores de Complemento 3bRESUMO
Decay-accelerating factor (DAF) is a cell surface regulator that accelerates the dissociation of C3/C5 convertases and thereby prevents the amplification of complement activation on self cells. In the context of transplantation, DAF has been thought to primarily regulate antibody-mediated allograft injury, which is in part serum complement-dependent. Based on our previously delineated link between DAF and CD4 T cell responses, we evaluated the effects of donor Daf1 (the murine homolog of human DAF) deficiency on CD8 T cell-mediated cardiac allograft rejection. MHC-disparate Daf1(-/-) allografts were rejected with accelerated kinetics compared with wild-type grafts. The accelerated rejection predominantly tracked with DAF's absence on bone marrow-derived cells in the graft and required allograft production of C3. Transplantation of Daf1(-/-) hearts into wild-type allogeneic hosts augmented the strength of the anti-donor (direct pathway) T cell response, in part through complement-dependent proliferative and pro-survival effects on alloreactive CD8 T cells. The accelerated allograft rejection of Daf1(-/-) hearts occurred in recipients lacking anti-donor Abs. The results reveal that donor DAF expression, by controlling local complement activation on interacting T cell APC partners, regulates the strength of the direct alloreactive CD8(+) T cell response. The findings provide new insights into links between innate and adaptive immunity that could be exploited to limit T cell-mediated injury to an allograft following transplantation.
Assuntos
Antígenos CD55/genética , Rejeição de Enxerto/imunologia , Transplante de Coração/imunologia , Linfócitos T/imunologia , Animais , Antígenos CD55/biossíntese , Antígenos CD55/fisiologia , Linfócitos T CD8-Positivos/imunologia , Linfócitos T CD8-Positivos/metabolismo , Células Cultivadas , Ativação do Complemento/genética , Ativação do Complemento/imunologia , Citotoxicidade Imunológica/genética , Rejeição de Enxerto/genética , Rejeição de Enxerto/metabolismo , Rejeição de Enxerto/patologia , Transplante de Coração/patologia , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C3H , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos SCID , Camundongos Transgênicos , Projetos Piloto , Linfócitos T/metabolismoRESUMO
The Old World hantaviruses, members of the family Bunyaviridae, cause hemorrhagic fever with renal syndrome (HFRS). Transmission to humans occurs via inhalation of aerosols contaminated with the excreta of infected rodents. The viral antigen is detectable in dendritic cells, macrophages, lymphocytes, and, most importantly, microvascular endothelial cells. However, the site and detailed mechanism of entry of HFRS-causing hantaviruses in polarized epithelial cells have not yet been defined. Therefore, this study focused on the entry of the pathogenic hantaviruses Hantaan and Puumala into African green monkey kidney epithelial cells and primary human endothelial cells. The polarized epithelial and endothelial cells were found to be susceptible to hantavirus infection exclusively from the apical surface. Treatment with phosphatidylinositol-specific phospholipase C, which removes glycosylphosphatidylinositol (GPI)-anchored proteins from the cell surface, protects cells from infection, indicating that hantaviruses require a GPI-anchored protein as a cofactor for entry. Decay-accelerating factor (DAF)/CD55 is a GPI-anchored protein of the complement regulatory system and serves as a receptor for attachment to the apical cell surface for a number of viruses. Infection was reduced by the pretreatment of hantaviral particles with human recombinant DAF. Moreover, the treatment of permissive cells with DAF-specific antibody blocked infection. These results demonstrate that the Old World hantaviruses Hantaan and Puumala enter polarized target cells from the apical site and that DAF is a critical cofactor for infection.
Assuntos
Antígenos CD55/fisiologia , Polaridade Celular , Febres Hemorrágicas Virais/virologia , Orthohantavírus/fisiologia , Internalização do Vírus , Animais , Células Cultivadas , Chlorocebus aethiops , Células Endoteliais/citologia , Células Endoteliais/virologia , Endotélio Vascular/citologia , Endotélio Vascular/virologia , Células Epiteliais/citologia , Células Epiteliais/virologia , Vírus Hantaan , Febres Hemorrágicas Virais/etiologia , Humanos , Nefropatias/virologia , Virus Puumala , Ligação ViralRESUMO
Paroxysmal nocturnal hemoglobinuria is a rare acquired clonal of the hematopoietic stem cell due to acquired mutation of the PIG-A gene. This results in the lack of two GPI-anchored membrane proteins involved in the inhibition of complement attack, thus explaining red cells hemolysis. The development of an anti-C5 monoclonal antibody (eculizumab) had profoundly modified the treatment of the the hemolytic form of the disease.
Assuntos
Anticorpos Monoclonais/uso terapêutico , Complemento C5/antagonistas & inibidores , Hemoglobinúria Paroxística/tratamento farmacológico , Anticorpos Monoclonais Humanizados , Transplante de Medula Óssea , Antígenos CD55/fisiologia , Antígenos CD59/fisiologia , Ensaios Clínicos como Assunto , Ativação do Complemento , Complemento C5/imunologia , Complemento C5/fisiologia , Glicosilfosfatidilinositóis/fisiologia , Hemoglobinúria Paroxística/diagnóstico , Hemoglobinúria Paroxística/genética , Hemoglobinúria Paroxística/imunologia , Hemoglobinúria Paroxística/cirurgia , Hemólise , Humanos , Proteínas de Membrana/deficiência , Proteínas de Membrana/genética , Modelos Biológicos , Transplante Homólogo , Adulto JovemRESUMO
Comparative sequence of the structural part of genomes pf the original daf+ clone and two derived daf- mutant clones (101 and 103) was analyzed to map mutations responsible for the loss of affinity for the receptor glycoprotein DAF (CD55). The obtained nucleotide sequences (EU167520, EU167521, EU167522) were deposited in the GenBank. There were single point mutations causing amino acid changes in VP2 protein: S145 --> N in clone 101 and G162 --> E in clone 103.
Assuntos
Antígenos CD55/fisiologia , Enterovirus Humano B/genética , Enterovirus Humano B/fisiologia , Genoma Viral , Mutação Puntual/genética , Sequência de Aminoácidos , Substituição de Aminoácidos , Animais , Humanos , Dados de Sequência MolecularRESUMO
It has long been understood that the control and surveillance of tumors within the body involves an intricate dance between the adaptive and innate immune systems. At the center of the interplay between the adaptive and innate immune response sits the complement system-an evolutionarily ancient response that aids in the destruction of microorganisms and damaged cells, including cancer cells. Membrane-bound complement regulatory proteins (mCRPs), such as CD46, CD55, and CD59, are expressed throughout the body in order to prevent over-activation of the complement system. These mCRPs act as a double-edged sword however, as they can also over-regulate the complement system to the extent that it is no longer effective at eliminating cancerous cells. Recent studies are now indicating that mCRPs may function as a biomarker of a malignant transformation in numerous cancer types, and further, are being shown to interfere with anti-tumor treatments. This highlights the critical roles that therapeutic blockade of mCRPs can play in cancer treatment. Furthermore, with the complement system having the ability to both directly and indirectly control adaptive T-cell responses, the use of a combinatorial approach of complement-related therapy along with other T-cell activating therapies becomes a logical approach to treatment. This review will highlight the biomarker-related role that mCRP expression may have in the classification of tumor phenotype and predicted response to different anti-cancer treatments in the context of an emerging understanding that complement activation within the Tumor Microenvironment (TME) is actually harmful for tumor control. We will discuss what is known about complement activation and mCRPs relating to cancer and immunotherapy, and will examine the potential for combinatorial approaches of anti-mCRP therapy with other anti-tumor therapies, especially checkpoint inhibitors such as anti PD-1 and PD-L1 monoclonal antibodies (mAbs). Overall, mCRPs play an essential role in the immune response to tumors, and understanding their role in the immune response, particularly in modulating currently used cancer therapeutics may lead to better clinical outcomes in patients with diverse cancer types.