RESUMO
IgE is an ancient and conserved immunoglobulin isotype with potent immunological function. Nevertheless, the regulation of IgE responses remains an enigma, and evidence of a role for IgE in host defense is limited. Here we report that topical exposure to a common environmental DNA-damaging xenobiotic initiated stress surveillance by γδTCR+ intraepithelial lymphocytes that resulted in class switching to IgE in B cells and the accumulation of autoreactive IgE. High-throughput antibody sequencing revealed that γδ T cells shaped the IgE repertoire by supporting specific variable-diversity-joining (VDJ) rearrangements with unique characteristics of the complementarity-determining region CDRH3. This endogenous IgE response, via the IgE receptor FcεRI, provided protection against epithelial carcinogenesis, and expression of the gene encoding FcεRI in human squamous-cell carcinoma correlated with good disease prognosis. These data indicate a joint role for immunosurveillance by T cells and by B cells in epithelial tissues and suggest that IgE is part of the host defense against epithelial damage and tumor development.
Assuntos
Linfócitos B/fisiologia , Carcinoma de Células Escamosas/imunologia , Células Epiteliais/fisiologia , Imunoglobulina E/metabolismo , Linfócitos Intraepiteliais/fisiologia , Neoplasias Experimentais/imunologia , Receptores de Antígenos de Linfócitos T gama-delta/metabolismo , Receptores de IgE/metabolismo , Animais , Antracenos/toxicidade , Carcinoma de Células Escamosas/diagnóstico , Morte Celular , Células Cultivadas , Regiões Determinantes de Complementaridade/genética , Dano ao DNA , Feminino , Sequenciamento de Nucleotídeos em Larga Escala , Switching de Imunoglobulina , Imunoglobulina E/genética , Vigilância Imunológica , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neoplasias Experimentais/induzido quimicamente , Piperidinas/toxicidade , Prognóstico , Receptores de Antígenos de Linfócitos T gama-delta/genéticaRESUMO
Regulation of neutrophil activation is critical for disease control. Neutrophil extracellular traps (NETs), which are web-like structures composed of DNA and neutrophil-derived proteins, are formed following pro-inflammatory signals; however, if this process is uncontrolled, NETs contribute to disease pathogenesis, exacerbating inflammation and host tissue damage1,2. Here we show that myeloid inhibitory C-type lectin-like (MICL), an inhibitory C-type lectin receptor, directly recognizes DNA in NETs; this interaction is vital to regulate neutrophil activation. Loss or inhibition of MICL functionality leads to uncontrolled NET formation through the ROS-PAD4 pathway and the development of an auto-inflammatory feedback loop. We show that in the context of rheumatoid arthritis, such dysregulation leads to exacerbated pathology in both mouse models and in human patients, where autoantibodies to MICL inhibit key functions of this receptor. Of note, we also detect similarly inhibitory anti-MICL autoantibodies in patients with other diseases linked to aberrant NET formation, including lupus and severe COVID-19. By contrast, dysregulation of NET release is protective during systemic infection with the fungal pathogen Aspergillus fumigatus. Together, we show that the recognition of NETs by MICL represents a fundamental autoregulatory pathway that controls neutrophil activity and NET formation.
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The local regulation of type 2 immunity relies on dialog between the epithelium and the innate and adaptive immune cells. Here we found that alarmin-induced expression of the co-stimulatory molecule OX40L on group 2 innate lymphoid cells (ILC2s) provided tissue-restricted T cell co-stimulation that was indispensable for Th2 and regulatory T (Treg) cell responses in the lung and adipose tissue. Interleukin (IL)-33 administration resulted in organ-specific surface expression of OX40L on ILC2s and the concomitant expansion of Th2 and Treg cells, which was abolished upon deletion of OX40L on ILC2s (Il7raCre/+Tnfsf4fl/fl mice). Moreover, Il7raCre/+Tnfsf4fl/fl mice failed to mount effective Th2 and Treg cell responses and corresponding adaptive type 2 pulmonary inflammation arising from Nippostrongylus brasiliensis infection or allergen exposure. Thus, the increased expression of OX40L in response to IL-33 acts as a licensing signal in the orchestration of tissue-specific adaptive type 2 immunity, without which this response fails to establish.
Assuntos
Imunidade Adaptativa/imunologia , Imunidade Inata/imunologia , Glicoproteínas de Membrana/imunologia , Linfócitos T Reguladores/imunologia , Células Th2/imunologia , Fatores de Necrose Tumoral/imunologia , Animais , Diferenciação Celular/imunologia , Interleucina-33/imunologia , Ativação Linfocitária/imunologia , Linfócitos/imunologia , Camundongos , Ligante OX40RESUMO
Wnt signaling plays critical roles in development of various organs and pathogenesis of many diseases, and augmented Wnt signaling has recently been implicated in mammalian aging and aging-related phenotypes. We here report that complement C1q activates canonical Wnt signaling and promotes aging-associated decline in tissue regeneration. Serum C1q concentration is increased with aging, and Wnt signaling activity is augmented during aging in the serum and in multiple tissues of wild-type mice, but not in those of C1qa-deficient mice. C1q activates canonical Wnt signaling by binding to Frizzled receptors and subsequently inducing C1s-dependent cleavage of the ectodomain of Wnt coreceptor low-density lipoprotein receptor-related protein 6. Skeletal muscle regeneration in young mice is inhibited by exogenous C1q treatment, whereas aging-associated impairment of muscle regeneration is restored by C1s inhibition or C1qa gene disruption. Our findings therefore suggest the unexpected role of complement C1q in Wnt signal transduction and modulation of mammalian aging.
Assuntos
Envelhecimento/metabolismo , Complemento C1q/metabolismo , Via de Sinalização Wnt , Animais , Complemento C1s/metabolismo , Humanos , Proteína-6 Relacionada a Receptor de Lipoproteína de Baixa Densidade/metabolismo , Camundongos , Soro/metabolismoRESUMO
For many years complement activation in systemic lupus erythematosus (SLE) was viewed as a major cause of tissue injury. However, human and murine studies showed that complement plays a protective as well as a proinflammatory role in tissue damage. A hierarchy is apparent with early classical pathway components, particularly C1q, exerting the greatest influence. Understanding the mechanisms underlying the protective function(s) of complement remains an important challenge for the future and has implications for the use of complement therapy in SLE. We review recent advances in the field and give a new perspective on the complement conundrum in SLE.
Assuntos
Ativação do Complemento , Proteínas do Sistema Complemento , Lúpus Eritematoso Sistêmico , Lúpus Eritematoso Sistêmico/imunologia , Humanos , Animais , Ativação do Complemento/imunologia , Proteínas do Sistema Complemento/imunologia , Proteínas do Sistema Complemento/metabolismo , Complemento C1q/imunologia , Complemento C1q/metabolismo , Camundongos , Via Clássica do Complemento/imunologiaRESUMO
Multidrug-resistant Neisseria gonorrhoeae is a global health problem. Monoclonal antibody (mAb) 2C7 recognizes a gonococcal lipooligosaccharide epitope that is expressed by >95% of clinical isolates and hastens gonococcal vaginal clearance in mice. Chimeric mAb 2C7 (human immunoglobulin G1 [IgG1]) with an E430G Fc modification that enhances Fc:Fc interactions and hexamerization following surface-target binding and increases complement activation (HexaBody technology) showed significantly greater C1q engagement and C4 and C3 deposition compared to mAb 2C7 with wild-type Fc. Greater complement activation by 2C7-E430G Fc translated to increased bactericidal activity in vitro and, consequently, enhanced efficacy in mice, compared with "Fc-unmodified" chimeric 2C7. Gonococci bind the complement inhibitors factor H (FH) and C4b-binding protein (C4BP) in a human-specific manner, which dampens antibody (Ab)-mediated complement-dependent killing. The variant 2C7-E430G Fc overcame the barrier posed by these inhibitors in human FH/C4BP transgenic mice, for which a single 1 µg intravenous dose cleared established infection. Chlamydia frequently coexists with and exacerbates gonorrhea; 2C7-E430G Fc also proved effective against gonorrhea in gonorrhea/chlamydia-coinfected mice. Complement activation alone was necessary and sufficient for 2C7 function, evidenced by the fact that (1) "complement-inactive" Fc modifications that engaged Fc gamma receptor (FcγR) rendered 2C7 ineffective, nonetheless; (2) 2C7 was nonfunctional in C1q-/- mice, when C5 function was blocked, or in C9-/- mice; and (3) 2C7 remained effective in neutrophil-depleted mice and in mice treated with PMX205, a C5a receptor (C5aR1) inhibitor. We highlight the importance of complement activation for antigonococcal Ab function in the genital tract. Elucidating the correlates of protection against gonorrhea will inform the development of Ab-based gonococcal vaccines and immunotherapeutics.
Assuntos
Ativação do Complemento/imunologia , Gonorreia/imunologia , Neisseria gonorrhoeae/imunologia , Animais , Anticorpos Antibacterianos/imunologia , Anticorpos Monoclonais/metabolismo , Antígenos de Bactérias , Proteína de Ligação ao Complemento C4b/imunologia , Fator H do Complemento/imunologia , Proteínas do Sistema Complemento/imunologia , Proteínas do Sistema Complemento/metabolismo , Epitopos/imunologia , Feminino , Voluntários Saudáveis , Humanos , Imunoglobulina G/imunologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Neisseria gonorrhoeae/patogenicidadeRESUMO
[This corrects the article DOI: 10.1371/journal.ppat.1005678.].
RESUMO
Novel therapeutics against multidrug-resistant Neisseria gonorrhoeae are urgently needed. Gonococcal lipooligosaccharide often expresses lacto-N-neotetraose (LNnT), which becomes sialylated in vivo, enhancing factor H (FH) binding and contributing to the organism's ability to resist killing by complement. We previously showed that FH domains 18-20 (with a D-to-G mutation at position 1119 in domain 19) fused to Fc (FHD1119G/Fc) displayed complement-dependent bactericidal activity in vitro and attenuated gonococcal vaginal colonization of mice. Gonococcal lipooligosaccharide phase variation can result in loss of LNnT expression. Loss of sialylated LNnT, although associated with a considerable fitness cost, could decrease efficacy of FHD1119G/Fc. Similar to N. meningitidis, gonococci also bind FH domains 6 and 7 through Neisserial surface protein A (NspA). In this study, we show that a fusion protein comprising FH domains 6 and 7 fused to human IgG1 Fc (FH6,7/Fc) bound to 15 wild-type antimicrobial resistant isolates of N. gonorrhoeae and to each of six lgtA gonococcal deletion mutants. FH6,7/Fc mediated complement-dependent killing of 8 of the 15 wild-type gonococcal isolates and effectively reduced the duration and burden of vaginal colonization of three gonococcal strains tested in wild-type mice, including two strains that resisted complement-dependent killing but on which FH6,7/Fc enhanced C3 deposition. FH/Fc lost efficacy when Fc was mutated to abrogate C1q binding and in C1q-/- mice, highlighting the requirement of the classical pathway for its activity. Targeting gonococci with FH6,7/Fc provides an additional immunotherapeutic approach against multidrug-resistant gonorrhea.
Assuntos
Gonorreia , Fragmentos Fc das Imunoglobulinas , Imunoterapia/métodos , Proteínas Recombinantes de Fusão/farmacologia , Animais , Fator H do Complemento , Humanos , Imunoglobulina G , Camundongos , Neisseria gonorrhoeae/imunologiaRESUMO
The complement cascade is crucial for clearance and control of invading pathogens, and as such is a key target for pathogen mediated host modulation. C3 is the central molecule of the complement cascade, and plays a vital role in opsonization of bacteria and recruitment of neutrophils to the site of infection. Streptococcal species have evolved multiple mechanisms to disrupt complement-mediated innate immunity, among which ScpA (C5a peptidase), a C5a inactivating enzyme, is widely conserved. Here we demonstrate for the first time that pyogenic streptococcal species are capable of cleaving C3, and identify C3 and C3a as novel substrates for the streptococcal ScpA, which are functionally inactivated as a result of cleavage 7 amino acids upstream of the natural C3 convertase. Cleavage of C3a by ScpA resulted in disruption of human neutrophil activation, phagocytosis and chemotaxis, while cleavage of C3 generated abnormally-sized C3a and C3b moieties with impaired function, in particular reducing C3 deposition on the bacterial surface. Despite clear effects on human complement, expression of ScpA reduced clearance of group A streptococci in vivo in wildtype and C5 deficient mice, and promoted systemic bacterial dissemination in mice that lacked both C3 and C5, suggesting an additional complement-independent role for ScpA in streptococcal pathogenesis. ScpA was shown to mediate streptococcal adhesion to both human epithelial and endothelial cells, consistent with a role in promoting bacterial invasion within the host. Taken together, these data show that ScpA is a multi-functional virulence factor with both complement-dependent and independent roles in streptococcal pathogenesis.
Assuntos
Adesinas Bacterianas/imunologia , Ativação do Complemento/imunologia , Endopeptidases/imunologia , Evasão da Resposta Imune/imunologia , Infecções Estreptocócicas/imunologia , Animais , Western Blotting , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Reação em Cadeia da Polimerase , Streptococcus pyogenes/imunologiaRESUMO
Microglia and non-professional immune cells (endothelial cells, neurons) participate in the recognition and removal of pathogens and tissue debris in the injured central nervous system through major pro-inflammatory processes. However, the mechanisms involved in regulating these responses remain ill-characterized. We herein show that CD93, also known as complement C1qRp/AA4 stem cell marker, has an important role in the regulation of inflammatory processes. The role of CD93 was evaluated in two models of neuroinflammation. We used the MOG-experimental autoimmune encephalomyelitis (EAE) model and the antibody-dependent EAE (ADEAE), which were induced in wild-type and CD93 knockout mice. We found that CD93 was highly expressed by neurons, endothelial cells and microglia (ramified >> amoeboid). Astrocytes and oligodendrocytes did not to express CD93. We further observed that CD93-deficient (CD93-/- ) mice presented a more robust brain and spinal cord inflammation in EAE and ADEAE. Encephalitis in CD93-/- was characterized by increased numbers of infiltrating M1 macrophages (CD11c+ CD206- ) and amoeboid microglia exhibiting a more activated phenotype (Tomato Lectinhigh Cox2high ). Damage to and leakage through the blood-brain barrier was increased in CD93-/- animals and was associated with a more robust neuronal injury when compared with wild-type EAE mice. We propose that CD93 is an important neuro-immune regulator to control central nervous system inflammation.
Assuntos
Encefalomielite Autoimune Experimental/imunologia , Regulação da Expressão Gênica/imunologia , Glicoproteínas de Membrana/imunologia , Microglia/imunologia , Receptores de Complemento/imunologia , Medula Espinal/imunologia , Animais , Encefalomielite Autoimune Experimental/genética , Encefalomielite Autoimune Experimental/patologia , Inflamação/genética , Inflamação/imunologia , Inflamação/patologia , Glicoproteínas de Membrana/genética , Camundongos , Camundongos Knockout , Microglia/patologia , Especificidade de Órgãos/genética , Especificidade de Órgãos/imunologia , Receptores de Complemento/genética , Medula Espinal/patologiaRESUMO
Spores of Bacillus anthracis, the causative agent of anthrax, are known to persist in the host lungs for prolonged periods of time, however the underlying mechanism is poorly understood. In this study, we demonstrated that BclA, a major surface protein of B. anthracis spores, mediated direct binding of complement factor H (CFH) to spores. The surface bound CFH retained its regulatory cofactor activity resulting in C3 degradation and inhibition of downstream complement activation. By comparing results from wild type C57BL/6 mice and complement deficient mice, we further showed that BclA significantly contributed to spore persistence in the mouse lungs and dampened antibody responses to spores in a complement C3-dependent manner. In addition, prior exposure to BclA deletion spores (ΔbclA) provided significant protection against lethal challenges by B. anthracis, whereas the isogenic parent spores did not, indicating that BclA may also impair protective immunity. These results describe for the first time an immune inhibition mechanism of B. anthracis mediated by BclA and CFH that promotes spore persistence in vivo. The findings also suggested an important role of complement in persistent infections and thus have broad implications.
Assuntos
Antraz/imunologia , Fator H do Complemento/imunologia , Tolerância Imunológica/imunologia , Glicoproteínas de Membrana/imunologia , Esporos Bacterianos/imunologia , Animais , Antraz/metabolismo , Bacillus anthracis/imunologia , Bacillus anthracis/metabolismo , Fator H do Complemento/metabolismo , Modelos Animais de Doenças , Ensaio de Imunoadsorção Enzimática , Citometria de Fluxo , Glicoproteínas de Membrana/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Esporos Bacterianos/metabolismoRESUMO
[This corrects the article DOI: 10.1371/journal.ppat.1005678.].
RESUMO
The complement component C1q is known to play a controversial role in the pathogenesis of systemic lupus erythematosus, but the underlying mechanisms remain poorly understood. Intraperitoneal injection of pristane induces a lupus-like syndrome whose pathogenesis implicates the secretion of type I IFN by CD11b(+) Ly6C(high) inflammatory monocytes in a TLR7-dependent fashion. C1q was also shown to influence the secretion of IFN-α. In this study, we explored whether C1q deficiency could affect pristane-induced lupus. Surprisingly, C1qa(-/-) mice developed lower titers of circulating Abs and milder arthritis compared with the controls. In keeping with the clinical scores, 2 wk after pristane injection the peritoneal recruitment of CD11b(+) Ly6C(high) inflammatory monocytes in C1qa(-/-) mice was impaired. Furthermore, C1q-deficient pristane-primed resident peritoneal macrophages secreted significantly less CCL3, CCL2, CXCL1, and IL-6 when stimulated in vitro with TLR7 ligand. Replenishing C1q in vivo during the pristane-priming phase rectified this defect. Conversely, pristane-primed macrophages from C3-deficient mice did not show impaired cytokine production. These findings demonstrate that C1q deficiency impairs the TLR7-dependent chemokine production by pristane-primed peritoneal macrophages and suggest that C1q, and not C3, is involved in the handling of pristane by phagocytic cells, which is required to trigger disease in this model.
Assuntos
Complemento C1q/deficiência , Complemento C1q/imunologia , Lúpus Eritematoso Sistêmico/imunologia , Macrófagos Peritoneais/imunologia , Terpenos/administração & dosagem , Receptor 7 Toll-Like/imunologia , Animais , Artrite/imunologia , Autoanticorpos/biossíntese , Quimiocinas/biossíntese , Citocinas/biossíntese , Modelos Animais de Doenças , Indutores de Interferon/farmacologia , Interferon-alfa/metabolismo , Lúpus Eritematoso Sistêmico/fisiopatologia , Ativação de Macrófagos , Macrófagos Peritoneais/efeitos dos fármacos , Camundongos Endogâmicos BALB C , Monócitos/imunologia , Poli I-C/farmacologiaRESUMO
Complement C1q is part of the C1 macromolecular complex that mediates the classical complement activation pathway: a major arm of innate immune defense. C1q is composed of A, B, and C chains that require post-translational prolyl 4-hydroxylation of their N-terminal collagen-like domain to enable the formation of the functional triple helical multimers. The prolyl 4-hydroxylase(s) that hydroxylate C1q have not previously been identified. Recognized prolyl 4-hydroxylases include collagen prolyl-4-hydroxylases (CP4H) and the more recently described prolyl hydroxylase domain (PHD) enzymes that act as oxygen sensors regulating hypoxia-inducible factor (HIF). We show that several small-molecule prolyl hydroxylase inhibitors that activate HIF also potently suppress C1q secretion by human macrophages. However, reducing oxygenation to a level that activates HIF does not compromise C1q hydroxylation. In vitro studies showed that a C1q A chain peptide is not a substrate for PHD2 but is a substrate for CP4H1. Circulating levels of C1q did not differ between wild-type mice or mice with genetic deficits in PHD enzymes, but were reduced by prolyl hydroxylase inhibitors. Thus, C1q is hydroxylated by CP4H, but not the structurally related PHD hydroxylases. Hence, reduction of C1q levels may be an important off-target side effect of small molecule PHD inhibitors developed as treatments for renal anemia.
Assuntos
Complemento C1q/metabolismo , Prolina Dioxigenases do Fator Induzível por Hipóxia/metabolismo , Hipóxia/metabolismo , Macrófagos/metabolismo , Pró-Colágeno-Prolina Dioxigenase/metabolismo , Inibidores de Prolil-Hidrolase/farmacologia , Anemia/tratamento farmacológico , Anemia/etiologia , Animais , Linhagem Celular , Complemento C1q/análise , Via Clássica do Complemento , Feminino , Humanos , Hidroxilação , Nefropatias/sangue , Nefropatias/tratamento farmacológico , Nefropatias/patologia , Macrófagos/efeitos dos fármacos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Pró-Colágeno-Prolina Dioxigenase/antagonistas & inibidores , Inibidores de Prolil-Hidrolase/uso terapêutico , Processamento de Proteína Pós-TraducionalRESUMO
Irradiation followed by bone marrow transplantation (BM-Tx) is a frequent therapeutic intervention causing pathology to the lung. Although alveolar epithelial type II (AE2) cells are essential for lung function and are damaged by irradiation, the long-term consequences of irradiation and BM-Tx are not well characterized. In addition, it is unknown whether surfactant protein D (SP-D) influences the response of AE2 cells to the injurious events. Therefore, wildtype (WT) and SP-D-/- mice were subjected to a myeloablative whole body irradiation dose of 8 Gy and subsequent BM-Tx and compared with age- and sex-matched untreated controls. AE2 cell changes were investigated quantitatively by design-based stereology. Compared with WT, untreated SP-D-/- mice showed a higher number of larger sized AE2 cells and a greater amount of surfactant-storing lamellar bodies. Irradiation and BM-Tx induced hyperplasia and hypertrophy in WT and SP-D-/- mice as well as the formation of giant lamellar bodies. The experimentally induced alterations were more severe in the SP-D-/- than in the WT mice, particularly with respect to the surfactant-storing lamellar bodies which were sometimes extremely enlarged in SP-D-/- mice. In conclusion, irradiation and BM-Tx have profound long-term effects on AE2 cells and their lamellar bodies. These data may explain some of the clinical pulmonary consequences of this procedure. The data should also be taken into account when BM-Tx is used as an experimental procedure to investigate the impact of bone marrow-derived cells for the phenotype of a specific genotype in the mouse.
Assuntos
Células Epiteliais Alveolares/metabolismo , Transplante de Medula Óssea , Raios gama , Proteína D Associada a Surfactante Pulmonar/metabolismo , Células Epiteliais Alveolares/citologia , Animais , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteína D Associada a Surfactante Pulmonar/deficiência , Irradiação Corporal TotalRESUMO
OBJECTIVES: TNFSF4 (encodes OX40L) is a susceptibility locus for systemic lupus erythematosus (SLE). Risk alleles increase TNFSF4 expression in cell lines, but the mechanism linking this effect to disease is unclear, and the OX40L-expressing cell types mediating the risk are not clearly established. Blockade of OX40L has been demonstrated to reduce disease severity in several models of autoimmunity, but not in SLE. We sought to investigate its potential therapeutic role in lupus. METHODS: We used a conditional knockout mouse system to investigate the function of OX40L on B and T lymphocytes in systemic autoimmunity. RESULTS: Physiologically, OX40L on both B and T cells contributed to the humoral immune response, but B cell OX40L supported the secondary humoral response and antibody affinity maturation. Our data also indicated that loss of B cell OX40L impeded the generation of splenic T follicular helper cells. We further show that in two models of SLE-a spontaneous congenic model and the H2-IAbm12 graft-versus-host-induced model-loss of B cell OX40L ameliorates the autoimmune phenotype. This improvement was, in each case, accompanied by a decline in T follicular helper cell numbers. Importantly, the germline knockout did not exhibit a markedly different phenotype from the B cell knockout in these models. CONCLUSIONS: These findings contribute to a model in which genetically determined increased OX40L expression promotes human SLE by several mechanisms, contingent on its cellular expression. The improvement in pathology in two models of systemic autoimmunity indicates that OX40L is an excellent therapeutic target in SLE.
Assuntos
Autoimunidade/imunologia , Linfócitos B/imunologia , Lúpus Eritematoso Sistêmico/imunologia , Glicoproteínas de Membrana/imunologia , Linfócitos T Auxiliares-Indutores/imunologia , Fatores de Necrose Tumoral/imunologia , Animais , Autoanticorpos/imunologia , Camundongos , Camundongos Knockout , Ligante OX40RESUMO
Objectives: The aim was to investigate whether the signalling lymphocyte activation molecule (SLAM) signalling pathways contribute to LN and whether SLAM receptors could be valuable biomarkers of disease activity. Methods: Peripheral blood mononuclear cells from 30National Research Ethics Service SLE patients with biopsy-proven LN were analysed by flow cytometry. Clinical measures of disease activity were assessed. The expression of the SLAM family receptors on T-cell subpopulations [CD4, CD8 and double negative (DN) T cells] was measured and compared between lupus patients with active renal disease and those in remission. Results: The frequency of CD8 T cells expressing SLAMF3, SLAMF5 and SLAMF7 was significantly lower in LN patients who were in remission. In contrast, these subsets were similar in patients with active renal disease and in healthy individuals. Patients with active nephritis had an increased percentage of circulating monocytes, consistent with a potential role played by these cells in glomerular inflammation. Changes in the frequency of DN T cells positive for SLAMF2, SLAMF4 and SLAMF7 were observed in lupus patients irrespective of the disease activity. We detected alterations in the cellular expression of the SLAM family receptors, but these changes were less obvious and did not reveal any specific pattern. The percentage of DN T cells expressing SLAMF6 could predict the clinical response to B-cell depletion in patients with LN. Conclusion: Our study demonstrates altered expression of the SLAM family receptors in SLE T lymphocytes. This is consistent with the importance of the SLAM-associated pathways in lupus pathogenesis.
Assuntos
Linfócitos T CD4-Positivos/imunologia , Nefrite Lúpica/tratamento farmacológico , Nefrite Lúpica/imunologia , Rituximab/uso terapêutico , Proteína Associada à Molécula de Sinalização da Ativação Linfocitária/metabolismo , Adulto , Antígenos CD/metabolismo , Linfócitos B/efeitos dos fármacos , Linfócitos B/imunologia , Biomarcadores/metabolismo , Biópsia por Agulha , Linfócitos T CD4-Positivos/metabolismo , Linfócitos T CD8-Positivos/metabolismo , Estudos de Coortes , Progressão da Doença , Feminino , Humanos , Imuno-Histoquímica , Infusões Intravenosas , Leucócitos Mononucleares/metabolismo , Nefrite Lúpica/patologia , Ativação Linfocitária/imunologia , Masculino , Pessoa de Meia-Idade , Valor Preditivo dos Testes , Medição de Risco , Índice de Gravidade de Doença , Proteína Associada à Molécula de Sinalização da Ativação Linfocitária/imunologia , Estatísticas não Paramétricas , Resultado do TratamentoRESUMO
Apoptotic cells are a source of autoantigens and impairment of their removal contributes to the development of autoimmunity in C1q deficiency. However, the lack of complement component 3 (C3), the predominant complement opsonin, does not predispose to autoimmunity, suggesting a modifying role of C3 in disease pathogenesis. To explore this hypothesis, here we investigated the role of C3 in the T-cell response to apoptotic cell-associated antigens. By comparing the phagosome maturation and the subsequent MHC class II presentation of a peptide derived from the internalized cargo between C3-deficient or C3-sufficient dendritic cells, we found that C3 deficiency accelerated the fusion of the apoptotic cargo with lysosomes. As a result, C3 deficiency led to impaired antigen-specific T-cell proliferation in vitro and in vivo. Notably, preopsonization of the apoptotic cells with C3 activation fragments rectified the trafficking and T-cell stimulation defects. These data indicate that activated C3 may act as a "chaperone" in the intracellular processing of an apoptotic cargo and, thus, may modulate the T-cell response to self-antigens displayed on dying cells.
Assuntos
Apoptose , Autoantígenos/imunologia , Complemento C3/metabolismo , Endocitose , Proteínas Opsonizantes/metabolismo , Linfócitos T/imunologia , Animais , Camundongos , Camundongos Knockout , Receptor 4 Toll-Like/genética , Receptor 4 Toll-Like/imunologiaRESUMO
We have previously shown that C1q is expressed on endothelial cells (ECs) of newly formed decidual tissue. Here we demonstrate that C1q is deposited in wound-healing skin in the absence of C4 and C3 and that C1q mRNA is locally expressed as revealed by real-time PCR and in situ hybridization. C1q was found to induce permeability of the EC monolayer, to stimulate EC proliferation and migration, and to promote tube formation and sprouting of new vessels in a rat aortic ring assay. Using a murine model of wound healing we observed that vessel formation was defective in C1qa(-/-) mice and was restored to normal after local application of C1q. The mean vessel density of wound-healing tissue and the healed wound area were significantly increased in C1q-treated rats. On the basis of these results we suggest that C1q may represent a valuable therapeutic agent that can be used to treat chronic ulcers or other pathological conditions in which angiogenesis is impaired, such as myocardial ischemia.
Assuntos
Complemento C1q/fisiologia , Células Endoteliais/efeitos dos fármacos , Neovascularização Fisiológica/genética , Cicatrização/genética , Animais , Proliferação de Células/efeitos dos fármacos , Complemento C1q/genética , Complemento C1q/farmacologia , Primers do DNA/genética , Células Endoteliais/fisiologia , Ensaio de Imunoadsorção Enzimática , Células Endoteliais da Veia Umbilical Humana , Humanos , Immunoblotting , Imuno-Histoquímica , Hibridização In Situ , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neovascularização Fisiológica/fisiologia , Ratos , Ratos Wistar , Reação em Cadeia da Polimerase em Tempo Real , Cicatrização/fisiologiaRESUMO
The complement-mediated renal diseases C3 glomerulopathy (C3G) and atypical hemolytic uremic syndrome (aHUS) strongly associate with inherited and acquired abnormalities in the regulation of the complement alternative pathway (AP). The major negative regulator of the AP is the plasma protein complement factor H (FH). Abnormalities in FH result in uncontrolled activation of C3 through the AP and associate with susceptibility to both C3G and aHUS. Although previously developed FH-deficient animal models have provided important insights into the mechanisms underlying susceptibility to these unique phenotypes, these models do not entirely reproduce the clinical observations. FH is predominantly synthesized in the liver. We generated mice with hepatocyte-specific FH deficiency and showed that these animals have reduced plasma FH levels with secondary reduction in plasma C3. Unlike mice with complete FH deficiency, hepatocyte-specific FH-deficient animals developed neither plasma C5 depletion nor accumulation of C3 along the glomerular basement membrane. In contrast, subtotal FH deficiency associated with mesangial C3 accumulation consistent with C3G. Although there was no evidence of spontaneous thrombotic microangiopathy, the hepatocyte-specific FH-deficient animals developed severe C5-dependent thrombotic microangiopathy after induction of complement activation within the kidney by accelerated serum nephrotoxic nephritis. Taken together, our data indicate that subtotal FH deficiency can give rise to either spontaneous C3G or aHUS after a complement-activating trigger within the kidney and that the latter is C5 dependent.