RESUMEN
The strategies that allow Brucella abortus to persist for years inside macrophages subverting host immune responses are not completely understood. Immunity against this bacterium relies on the capacity of IFN-γ to activate macrophages, endowing them with the ability to destroy intracellular bacteria. We report here that infection with B. abortus down-modulates the expression of the type I receptor for the Fc portion of IgG (FcγRI, CD64) and FcγRI-restricted phagocytosis regulated by IFN-γ in human monocytes/macrophages. Both phenomena were not dependent on bacterial viability, since they were also induced by heat-killed B. abortus (HKBA), suggesting that they were elicited by a structural bacterial component. Accordingly, a prototypical B. abortus lipoprotein (L-Omp19), but not its unlipidated form, inhibited both CD64 expression and FcγRI-restricted phagocytosis regulated by IFN-γ. Moreover, a synthetic lipohexapeptide that mimics the structure of the protein lipid moiety also inhibited CD64 expression, indicating that any Brucella lipoprotein could down-modulate CD64 expression and FcγRI-restricted phagocytosis. Pre-incubation of monocytes/macrophages with anti-TLR2 mAb blocked the inhibition of the CD64 expression mediated by HKBA and L-Omp19. These results, together with our previous observations establish that B. abortus utilizes its lipoproteins to inhibit the monocytes/macrophages activation mediated by IFN-γ and to subvert host immunonological responses.
Asunto(s)
Brucella abortus/fisiología , Interferón gamma/antagonistas & inhibidores , Macrófagos/inmunología , Monocitos/inmunología , Receptores de IgG/biosíntesis , Receptor Toll-Like 2/metabolismo , Antígenos Bacterianos/metabolismo , Proteínas de la Membrana Bacteriana Externa/metabolismo , Brucella abortus/química , Brucella abortus/metabolismo , Células Cultivadas , Citometría de Flujo , Interacciones Huésped-Patógeno , Humanos , Interferón gamma/inmunología , Interferón gamma/metabolismo , Lipoproteínas/metabolismo , Macrófagos/microbiología , Monocitos/microbiología , Fagocitosis/fisiología , Receptores de IgG/antagonistas & inhibidores , Receptores de IgG/metabolismo , Estadísticas no ParamétricasRESUMEN
The interaction between immune complexes (IC) and the receptors for the Fc portion of IgG (FcgammaRs) triggers regulatory and effector functions in the immune system. In this study, we investigated the effects of IC on differentiation, maturation, and functions of human monocyte-derived dendritic cells (DC). When IC were added on day 0, DC generated on day 6 (IC-DC) showed lower levels of CD1a and increased expression of CD14, MHC class II, and the macrophage marker CD68, as compared with normally differentiated DC. The use of specific blocking FcgammaR mAbs indicated that the effect of IC was exerted mainly through their interaction with FcgammaRI and to a lesser extend with FcgammaRII. Immature IC-DC also expressed higher levels of CD83, CD86, and CD40 and the expression of these maturation markers was not further regulated by LPS. The apparent lack of maturation following TLR stimulation was associated with a decreased production of IL-12, normal secretion of IL-10 and CCL22, and increased production of CXCL8 and CCL2. IC-DC displayed low endocytic activity and a reduced ability to induce allogeneic T cell proliferation both at basal and LPS-stimulated conditions. Altogether, these data reveal that IC strongly affect DC differentiation and maturation. Skewing of DC function from Ag presentation to a proinflammatory phenotype by IC resembles the state of activation observed in DC obtained from patients with chronic inflammatory autoimmune disorders, such as systemic lupus erythematosus disease and arthritis. Therefore, the altered maturation of DC induced by IC may be involved in the pathogenesis of autoimmune diseases.
Asunto(s)
Complejo Antígeno-Anticuerpo/fisiología , Diferenciación Celular/inmunología , Linaje de la Célula/inmunología , Células Dendríticas/citología , Células Dendríticas/inmunología , Inhibidores de Crecimiento/fisiología , Monocitos/citología , Monocitos/inmunología , Animales , Complejo Antígeno-Anticuerpo/sangre , Enfermedades Autoinmunes/inmunología , Enfermedades Autoinmunes/metabolismo , Enfermedades Autoinmunes/patología , Células Cultivadas , Células Dendríticas/metabolismo , Células Dendríticas/patología , Relación Dosis-Respuesta Inmunológica , Inhibidores de Crecimiento/sangre , Humanos , Inmunoglobulina G/metabolismo , Lupus Eritematoso Sistémico/inmunología , Lupus Eritematoso Sistémico/metabolismo , Lupus Eritematoso Sistémico/patología , Activación de Linfocitos/inmunología , Prueba de Cultivo Mixto de Linfocitos , Monocitos/metabolismo , Monocitos/patología , Conejos , Receptores de IgG/antagonistas & inhibidores , Receptores de IgG/biosíntesis , Receptores de IgG/fisiología , Linfocitos T/inmunología , Factores de TiempoRESUMEN
In a 20-year period in a single institution, 34 patients with chronic, refractory autoimmune thrombocytopenic purpura were prospectively treated with ex vivo anti-D opsonized autologous red blood cells. All patients had received previous treatment with steroids and/or immunosuppressive agents, and 11 had been splenectomized. Twenty one patients had an increase in the platelet count; in five cases, the increase was more than 50 x 10(9)/L platelets and in 16 the increase was more than 100 x 10(9)/L platelets. Early responses were observed in 20 patients and late responses in seven, whereas seven patients (20%) did not respond at all. Nine of the 20 individuals who achieved an ER had a subsequent drop in the platelet count; however, only three had a drop below 50 x 10(9)/L. When last censored, of the 34 patients, 24 (70%) had a platelet count above 50 x 10(9)/L. The 84-month thrombocytopenia-free (over 50 x 10(9)/L platelets) status of the whole group is 70%, whereas the 84-month complete remission (over 100 x 10(9)/L platelets) status of the whole group is 50%. It is concluded that the use of ex vivo anti-D opsonized red blood cells may represent another, substantially cheaper treatment of patients with chronic, refractory, autoimmune thrombocytopenic purpura.
Asunto(s)
Transfusión de Eritrocitos , Terapia de Inmunosupresión/métodos , Isoanticuerpos/uso terapéutico , Proteínas Opsoninas/uso terapéutico , Púrpura Trombocitopénica Idiopática/tratamiento farmacológico , Receptores de IgG/antagonistas & inhibidores , Adolescente , Adulto , Anciano , Preescolar , Terapia Combinada/economía , Costos de los Medicamentos , Resistencia a Medicamentos , Femenino , Humanos , Terapia de Inmunosupresión/economía , Inmunosupresores/uso terapéutico , Lactante , Masculino , Persona de Mediana Edad , Recuento de Plaquetas , Estudios Prospectivos , Púrpura Trombocitopénica Idiopática/inmunología , Púrpura Trombocitopénica Idiopática/cirugía , Inducción de Remisión , Sistema del Grupo Sanguíneo Rh-Hr/inmunología , Globulina Inmune rho(D) , EsplenectomíaRESUMEN
N-Formyl peptides are cleavage products of bacterial and mitochondrial proteins that have pro-inflammatory activities and play an important role in antibacterial host defence. FcgammaRI is a receptor for the Fc portion of immunoglobulin G expressed in monocytes that mediates cytotoxicity and is upregulated by interferon-gamma (IFN-gamma) and interleukin-10 (IL-10). In this report, we demonstrate that N-formyl-methionyl-leucyl-phenylalanine (FMLP) downregulates the expression of FcgammaRI in IFN-gamma-treated monocytes, but not in IL-10-treated monocytes. We determine that supernatants obtained from monocytes treated with IFN-gamma and then exposed to FMLP induce the downregulation of FcgammaRI in naïve monocytes. This effect is abrogated by the protease inhibitors phenylmethylsulphonyl fluoride and phosphoramidon, which inhibit serine and metalloproteases, respectively. Supernatants from FMLP-treated neutrophils also induce the downregulation of FcgammaRI, when added to naïve monocytes. Similar observations were obtained in vivo in a mouse model of chronic inflammation. In vivo, FMLP also downregulates the expression of FcgammaRs in IFN-gamma-activated macrophages. Our results support the existence of a new mechanism through which FMLP could modulate the activity of monocytes/macrophages during bacterial infections.
Asunto(s)
Interferón gamma/inmunología , Macrófagos/inmunología , N-Formilmetionina Leucil-Fenilalanina/inmunología , Receptores de IgG/biosíntesis , Animales , Citotoxicidad Celular Dependiente de Anticuerpos/inmunología , Regulación hacia Abajo/efectos de los fármacos , Femenino , Citometría de Flujo , Humanos , Inflamación/inmunología , Inflamación/metabolismo , Interferón gamma/farmacología , Interleucina-10/inmunología , Activación de Macrófagos/efectos de los fármacos , Activación de Macrófagos/inmunología , Macrófagos/efectos de los fármacos , Macrófagos/metabolismo , Ratones , Ratones Endogámicos BALB C , Monocitos/efectos de los fármacos , Monocitos/inmunología , Monocitos/metabolismo , N-Formilmetionina Leucil-Fenilalanina/farmacología , Inhibidores de Proteasas/farmacología , Receptores de IgG/antagonistas & inhibidores , Receptores de IgG/inmunologíaRESUMEN
Human polymorphonuclear neutrophils (PMN) participate in different cellular functions, including phagocytosis, antibody-dependent cell-mediated cytotoxicity (ADCC), and release of reactive oxygen intermediates. Each of these functions can be triggered by receptors for the Fc portion of IgG molecules (Fc gamma R). Normal resting neutrophils possess Fc gamma RII and Fc gamma RIIIB receptors. They also have specific membrane receptors for formylated peptides such as the prototype N-formylmethionylleucylphenylalanine (FMLP). In this report, we present evidence that preincubation of PMN with FMLP inhibits different PMN Fc gamma R-dependent functions such as phagocytosis, ADCC, and immune complex-dependent cytotoxicity. These inhibitory effects can be explained, at least in part, by downregulation of both Fc gamma RII and Fc gamma RIII. Unexpectedly, preincubation of FMLP with PMN was not necessary for ADCC inhibition. Taking into account that the FMLP-dependent Fc gamma R downregulation is not observed before 30 min of incubation, and the onset of ADCC occurs rapidly (seconds), it is possible that FMLP can modify this function by altering early intracellular events.