RESUMO
Ficolins recognize pathogen associated molecular patterns and activate the lectin pathway of complement system. However, our knowledge regarding pathogen recognition of human ficolins is still limited. We therefore set out to explore and investigate the possible interactions of the two main serum ficolins, ficolin-2 and ficolin-3 with different Gram-negative bacteria. We used recombinant ficolin molecules and normal human serum, which were detected with anti-ficolin monoclonal antibodies. In addition we investigated the capacity of these pathogens to activate the lectin pathway of complement system. We show for the first time that human ficolin-2 recognizes the nonpathogenic spirochete Leptospira biflexa serovar Patoc, but not the pathogenic Leptospira interrogans serovar Kennewicki strain Fromm. Additionally, human ficolin-2 and ficolin-3 recognize pathogenic Pasteurella pneumotropica, enteropathogenic Escherichia coli (EPEC) serotype O111ab:H2 and enteroaggregative E. coli (EAEC) serogroup O71 but not four enterohemorrhagic E. coli, three EPEC, three EAEC and two nonpathogenic E. coli strains (DH5α and HB101). The lectin pathway was activated by Pasteurella pneumotropica, EPEC O111ab:H2 and EAEC O71 after incubation with C1q depleted human serum. In conclusion, this study provide novel insight in the binding and complement activating capacity of the lectin pathway initiation molecules ficolin-2 and ficolin-3 towards relevant Gram-negative pathogens of pathophysiological relevance.
Assuntos
Lectina de Ligação a Manose da Via do Complemento/imunologia , Escherichia coli/imunologia , Glicoproteínas/imunologia , Lectinas/imunologia , Leptospira/imunologia , Pasteurella pneumotropica/imunologia , Humanos , Proteínas Recombinantes/imunologia , FicolinasRESUMO
BACKGROUND/AIMS: Lupus nephritis (LN) is one of the most serious manifestations of SLE occurring in 66-90% of these patients. The complement system is part of the innate immunity and modulator of inflammation and the adaptative immune response. Mannan-binding lectin (MBL) and Ficolin-2 (FCN-2) are important members of the lectin pathway of complement activation. Despite the significant participation of complement in the pathogenesis of the LN, there are few reports demonstrating "in situ" deposition of complement components in renal biopsy specimens in this disorder. The present study investigated the deposition of complement components in kidney specimens of LN patients. METHODS: Renal biopsies of 11 patients with SLE and LN were evaluated for immunofluorescence staining for IgG, IgA, IgM, C3, and C1q. Additionally, MBL, FCN-2 and C5b-9 were researched using monoclonal antibodies. RESULTS: All the biopsies were positive for IgG, C3, and C1q, eight were positive IgM and five had IgA deposition in glomerular tissue. The terminal complex of complement C5b9 was positive in all cases, MBL in nine (82%) cases; seven (63.6%) of them presenting concomitantly FCN-2 deposition. Patients presenting MBL deposition had higher mean of urinary proteins (9.0 g/day) than patients with negative MBL deposition (mean of 2.3g/day). CONCLUSIONS: In this study, we demonstrated in situ the participation of complement in the renal injury, including MBL and FCN-2 of the lectin pathway; also the strong role of C5b-9 in the pathogenesis of LN.
Assuntos
Lectina de Ligação a Manose da Via do Complemento/imunologia , Proteínas do Sistema Complemento/imunologia , Nefrite Lúpica/imunologia , Nefrite Lúpica/patologia , Adulto , Complexo Antígeno-Anticorpo/imunologia , Complexo Antígeno-Anticorpo/metabolismo , Biópsia , Proteínas do Sistema Complemento/metabolismo , Feminino , Humanos , Isotipos de Imunoglobulinas/imunologia , Isotipos de Imunoglobulinas/metabolismo , Rim/imunologia , Rim/patologia , Glomérulos Renais/imunologia , Glomérulos Renais/metabolismo , Glomérulos Renais/patologia , Nefrite Lúpica/metabolismo , Masculino , Microscopia de Fluorescência , Adulto JovemRESUMO
Due to its importance both in the clearance of pathogens that contribute as rheumatic etiological agents and in the disposal of apoptotic bodies and potential autoimmune initiators, deficiencies of the components of the lectin pathway of complement have been found to increase susceptibility and modulate the severity of most rheumatic disorders. This chapter introduces the general aspects of the structure, function, and genetics of lectin pathway components and summarizes current knowledge of the field regarding rheumatic diseases predisposition and modulation.
Assuntos
Artrite Reumatoide/metabolismo , Lectina de Ligação a Manose da Via do Complemento/imunologia , Lúpus Eritematoso Sistêmico/metabolismo , Lectinas de Ligação a Manose/metabolismo , Febre Reumática/metabolismo , Síndrome de Sjogren/metabolismo , Artrite Reumatoide/imunologia , Artrite Reumatoide/fisiopatologia , Proteínas do Sistema Complemento/imunologia , Proteínas do Sistema Complemento/metabolismo , Humanos , Lúpus Eritematoso Sistêmico/imunologia , Lúpus Eritematoso Sistêmico/fisiopatologia , Lectinas de Ligação a Manose/química , Lectinas de Ligação a Manose/genética , Lectinas de Ligação a Manose/imunologia , Polimorfismo Genético , Febre Reumática/imunologia , Febre Reumática/fisiopatologia , Síndrome de Sjogren/imunologia , Síndrome de Sjogren/fisiopatologiaRESUMO
Paracoccidioides brasiliensis (Pb) is a dimorphic fungal pathogen that causes paracoccidioidomycosis, the most severe deep mycosis from South America. Although cell mediated immunity is considered the most efficient protective mechanism against Pb infection, mechanisms of innate immunity are poorly defined. Herein, we investigated the interaction of the complement system with high and low virulence isolates of Pb. We demonstrated that Pb18, a high virulence Pb isolate, when incubated with normal human serum (NHS) induces consumption of hemolytic complement and, when immobilized, promotes binding of C4b, C3b and C5b-C9. Both, low virulence (Pb265) and high virulence (Pb18) isolates consumed C4, C3 and mannose-binding lectin (MBL) of MBL-sufficient, but not of MBL-deficient serum as revealed by deposition of residual C4, C3 and MBL on immune complexes and mannan. However, higher complement components consumption was observed with Pb265, as compared with Pb18. The suggested relationship between low virulence and significant complement activation properties of Pb isolates, was confirmed by the demonstration that virulence attenuation of Pb 18 results in acquisition of the ability to activate complement. Conversely, reactivation of attenuated Pb18, results in loss of the ability to activate complement. Our results demonstrate for the first time that Pb yeasts activate the complement system by the lectin pathway, and there is an inverse correlation between complement activating ability and Pb virulence. These differences could exert an influence on innate immunity and severity of the disease developed by infected hosts.
Assuntos
Lectina de Ligação a Manose da Via do Complemento/imunologia , Paracoccidioides/imunologia , Paracoccidioidomicose/imunologia , Transdução de Sinais/imunologia , Animais , Ensaio de Imunoadsorção Enzimática , Humanos , Lectina de Ligação a Manose/imunologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Knockout , Paracoccidioides/patogenicidade , VirulênciaRESUMO
Paracoccidioides brasiliensis (Pb) is a dimorphic fungal pathogen that causes paracoccidioidomycosis, the most severe deep mycosis from South America. Although cell mediated immunity is considered the mostefficient protective mechanism against Pb infection, mechanisms of innate immunity are poorly defined. Herein, we investigated the interaction of the complement system with high and low virulence isolates of Pb. We demonstrated that Pb18, a high virulence Pb isolate, when incubated with normal human serum (NHS) induces consumption of hemolytic complement and, when immobilized, promotes binding of C4b, C3b and C5b-C9. Both, low virulence (Pb265) and high virulence (Pb18) isolates consumed C4, C3 and mannose-binding lectin (MBL) of MBL-sufficient, but not of MBL-deficient serum as revealed bydeposition of residual C4, C3 and MBL on immune complexes and mannan. However, higher complementcomponents consumption was observed with Pb265, as compared with Pb18. The suggested relationshipbetween low virulence and significant complement activation properties of Pb isolates, was confirmed by the demonstration that virulence attenuation of Pb 18 results in acquisition of the ability to activate complement. Conversely, reactivation of attenuated Pb18, results in loss of the ability to activate complement. Our results demonstrate for the first time that Pb yeasts activate the complement system by the lectin pathway, and there is an inverse correlation between complement activating ability and Pbvirulence. These differences could exert an influence on innate immunity and severity of the disease developed by infected hosts.
Assuntos
Humanos , Lectina de Ligação a Manose da Via do Complemento/imunologia , Micoses , Micoses/imunologia , Paracoccidioidomicose/enzimologia , Paracoccidioidomicose/imunologia , Paracoccidioidomicose/metabolismoRESUMO
The complement system is the first line of defence against pathogen infection and can be activated by the classic, alternative and lectin pathways. Trypanosoma cruzi, the causative agent of Chagas disease, has to evade complement system killing and invade the host cells to progress in infection. T. cruzi infectious stages resist complement-mediated killing by expressing surface receptors, which dissociate or prevent C3 convertase formation. Here, we present the first evidence that T. cruzi activates the complement lectin pathway. We detected rapid binding of mannan-binding lectin, H-ficolin, and L-ficolin to the surface of T. cruzi, and found that serum depleted of these molecules failed to kill parasites. Furthermore, lectin pathway activation by T. cruzi required the MBL-associated serine protease 2 (MASP2) activity resulting in C2 factor cleavage. In addition, we demonstrate that the infectious stage of T. cruzi inhibits the lectin pathway activation and complement killing expressing the complement C2 receptor inhibitor trispanning (CRIT) protein. Transgenic parasites overexpressing CRIT were highly resistant to complement-mediated killing. CRIT-derived peptides inhibited both C2 binding to the surface of T. cruzi and parasite killing. Biochemical studies revealed that the CRIT extracellular domain 1 inhibits MASP2 cleavage of C2 factor and thereby impairs C3 convertase formation. Our findings establish that the complement lectin pathway recognizes T. cruzi and provide molecular insights into how the infectious stage inhibits this activation to resist complement system killing.