RESUMO
Intravenous immunoglobulin (IVIg) preparations are known to modulate autoimmune/inflammatory diseases through several F(ab')(2)- and Fc-dependent mechanisms. In this study, we show that the in vitro and the in vivo exposure of B lymphocytes from lupus-prone and from healthy mice to IVIg results in an increased expression of their surface inhibitory FcgammaIIB receptors. Further, this exposure enhanced the ability of a chimeric antibody, cross-linking FcgammaRIIB and immunoglobulin receptors on DNA-specific B lymphocytes, to suppress IgG anti-DNA antibody production. F(ab')(2) fragments of IVIg had a similar activity as the intact preparation, whereas Fc fragments had no effect. This study describes a novel approach with clinical relevance for modulating B lymphocyte activity.
Assuntos
Linfócitos B/efeitos dos fármacos , Imunoglobulinas Intravenosas/farmacologia , Receptores de IgG/metabolismo , Animais , Linfócitos B/imunologia , Linfócitos B/metabolismo , Células Cultivadas , Avaliação Pré-Clínica de Medicamentos , Feminino , Ativação Linfocitária/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Transgênicos , Regulação para Cima/efeitos dos fármacosRESUMO
Intravenous immunoglobulin (IVIG) are purified IgG preparations made from the pooled plasma from thousands of healthy donors and are being tested in preclinical mouse models. Inherent challenges, however, are the pluripotency of IVIG and its xenogeneicity in animals. IVIG can alter the viability of human neutrophils via agonistic antibodies to Fas and Siglec-9. In this study, we compared the effects of IVIG on human and mouse neutrophils using different death assays. Different commercial IVIG preparations similarly induced cytokine-dependent death in human neutrophils, whereas they had no effects on the survival of either peripheral blood or bone marrow neutrophils from C57BL/6 or BALB/c mice. F(ab')2 but not Fc fragments of IVIG induced death of human neutrophils, whereas neither of these IVIG fragments, nor agonistic monoclonal antibodies to human Fas or Siglec-9 affected the viability of mouse neutrophils. Pooled mouse IgG, which exhibited a different immunoprofile compared to IVIG, also had no effect on mouse cells. Together, these observations demonstrate that effects of IVIG on neutrophil survival are not adequately reflected in current mouse models, despite the key role of these cells in human inflammatory and autoimmune diseases.
Assuntos
Sobrevivência Celular/efeitos dos fármacos , Imunoglobulina G/imunologia , Imunoglobulinas Intravenosas/administração & dosagem , Neutrófilos/efeitos dos fármacos , Animais , Anticorpos Monoclonais/administração & dosagem , Anticorpos Monoclonais/imunologia , Antígenos CD/imunologia , Sobrevivência Celular/imunologia , Humanos , Fragmentos Fc das Imunoglobulinas/imunologia , Imunoglobulina G/administração & dosagem , Imunoglobulinas Intravenosas/imunologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Neutrófilos/imunologia , Lectinas Semelhantes a Imunoglobulina de Ligação ao Ácido Siálico/imunologia , Receptor fas/imunologiaRESUMO
IgG molecules are exposed on a regular basis to acidic conditions during immunoaffinity purification procedures, as well as during the production of some therapeutic immunoglobulin preparations. This exposure is known to induce in them an antigen-binding polyreactivity. The molecular mechanisms and the possible biological significance of this phenomenon remain, however, poorly understood. In addition to the previously reported ability of these modified IgG antibodies to interact with a large panel of self-antigens, enhanced binding to non-self-antigens (bacterial), an increased ability to engage in F(ab')(2)/F(ab')(2) (idiotype/anti-idiotype) interactions and an increased functional antigen-binding affinity are reported here. The newly acquired 'induced polyreactivity' of low-pH buffer-exposed IgG is related to structural changes in the immunoglobulin molecules, and is at least partly attributable to the enhanced role of the hydrophobic effect in their interactions with antigen. Our results suggest that data from many previous studies on monoclonal and polyclonal IgG antibodies purified by low-pH buffer elution from protein A or protein G immunoaffinity columns should be reconsidered, as the procedure itself may have dramatically affected their antigen-binding behavior and biological activity. Low-pH buffer-treated pooled therapeutic immunoglobulins acquire novel beneficial properties, as passive immunotherapy with the pH 4.0 buffer-exposed, but not with the native therapeutic intravenous immunoglobulin preparation, improves the survival of mice with bacterial lipopolysaccharide-induced septic shock.
Assuntos
Imunoglobulinas Intravenosas/química , Imunoglobulinas Intravenosas/uso terapêutico , Sepse/terapia , Naftalenossulfonato de Anilina/química , Animais , Anticorpos Anti-Idiotípicos/imunologia , Anticorpos Monoclonais/química , Anticorpos Monoclonais/imunologia , Afinidade de Anticorpos/imunologia , Especificidade de Anticorpos/imunologia , Reações Antígeno-Anticorpo/imunologia , Antígenos de Bactérias/imunologia , Autoantígenos/imunologia , Western Blotting , Soluções Tampão , Proteína C-Reativa/imunologia , Ensaio de Imunoadsorção Enzimática , Escherichia coli/imunologia , Corantes Fluorescentes/química , Humanos , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Imunoglobulinas Intravenosas/imunologia , Interferon gama/imunologia , Cinética , Camundongos , Camundongos Endogâmicos ICR , Microscopia de Fluorescência , Conformação Proteica , Proteínas Recombinantes , Análise de SobrevidaRESUMO
Normal pooled human IVIg are produced using various blood protein fractionation technologies and as a result they may well differ in their biological properties. We have demonstrated that exposure of IVIg, for a period as short as 15 min, to protein-destabilizing agents like acidic pH, ROS or pro-oxidative ferrous ions dramatically increases the panel of recognized Ag including pro-inflammatory cytokines. We now show that exposure of IVIg to ferrous ions modifies some IgG molecules without denaturating them and enhances the protective activity of the preparation in experimental septic shock.