RESUMEN
Effective host defense against Mycobacterium tuberculosis requires the induction of Th1 cytokine responses. We investigated the regulated expression and functional role of the inducible costimulator (ICOS), a receptor known to regulate Th cytokine production, in the context of human tuberculosis. Patients with active disease, classified as high responder (HR) or low responder (LR) patients according to their in vitro T cell responses against the Ag, were evaluated for T cell expression of ICOS after M. tuberculosis-stimulation. We found that ICOS expression significantly correlated with IFN-gamma production by tuberculosis patients. ICOS expression levels were regulated in HR patients by Th cytokines: Th1 cytokines increased ICOS levels, whereas Th2-polarizing conditions down-regulated ICOS in these individuals. Besides, in human polarized Th cells, engagement of ICOS increased M. tuberculosis IFN-gamma production with a magnitude proportional to ICOS levels on those cells. Moreover, ICOS ligation augmented Ag-specific secretion of the Th1 cytokine IFN-gamma from responsive individuals. In contrast, neither Th1 nor Th2 cytokines dramatically affected ICOS levels on Ag-stimulated T cells from LR patients, and ICOS activation did not enhance IFN-gamma production. However, simultaneous activation of ICOS and CD3 slightly augmented IFN-gamma secretion by LR patients. Together, our data suggest that the regulation of ICOS expression depends primarily on the response of T cells from tuberculosis patients to the specific Ag. IFN-gamma released by M. tuberculosis-specific T cells modulates ICOS levels, and accordingly, ICOS ligation induces IFN-gamma secretion. Thus, ICOS activation may promote the induction of protective Th1 cytokine responses to intracellular bacterial pathogens.
Asunto(s)
Antígenos de Diferenciación de Linfocitos T/fisiología , Interferón gamma/biosíntesis , Tuberculosis Pulmonar/inmunología , Anticuerpos Monoclonales/metabolismo , Antígenos de Diferenciación de Linfocitos T/biosíntesis , Antígenos de Diferenciación de Linfocitos T/inmunología , Antígenos de Diferenciación de Linfocitos T/metabolismo , Línea Celular , Células Cultivadas , Regulación de la Expresión Génica/fisiología , Humanos , Proteína Coestimuladora de Linfocitos T Inducibles , Líquido Intracelular/inmunología , Líquido Intracelular/metabolismo , Líquido Intracelular/microbiología , Ligandos , Linfocitos T Colaboradores-Inductores/inmunología , Linfocitos T Colaboradores-Inductores/metabolismo , Linfocitos T Colaboradores-Inductores/microbiología , Células TH1/inmunología , Células TH1/metabolismo , Células TH1/microbiologíaRESUMEN
T cell production of IFN-gamma contributes to host defense against infection by intracellular pathogens, including mycobacteria. Lepromatous leprosy, the disseminated form of infection caused by Mycobacterium leprae, is characterized by loss of cellular response against the pathogen and diminished Th1 cytokine production. Relieving bacterial burden in Ag-unresponsive patients might be achieved through alternative receptors that stimulate IFN-gamma production. We have previously shown that ligation of signaling lymphocytic activation molecule (SLAM) enhances IFN-gamma in mycobacterial infection; therefore, we investigated molecular pathways leading from SLAM activation to IFN-gamma production in human leprosy. The expression of the SLAM-associated protein (an inhibitory factor for IFN-gamma induction) on M. leprae-stimulated cells from leprosy patients was inversely correlated to IFN-gamma production. However, SLAM ligation or exposure of cells from lepromatous patients to a proinflammatory microenvironment down-regulated SLAM-associated protein expression. Moreover, SLAM activation induced a sequence of signaling proteins, including activation of the NF-kappaB complex, phosphorylation of Stat1, and induction of T-bet expression, resulting in the promotion of IFN-gamma production, a pathway that remains quiescent in response to Ag in lepromatous patients. Therefore, our findings reveal a cascade of molecular events during signaling through SLAM in leprosy that cooperate to induce IFN-gamma production and strongly suggest that SLAM might be a focal point for therapeutic modulation of T cell cytokine responses in diseases characterized by dysfunctional Th2 responses.
Asunto(s)
Adyuvantes Inmunológicos/fisiología , Glicoproteínas/fisiología , Inmunoglobulinas/fisiología , Líquido Intracelular/inmunología , Líquido Intracelular/microbiología , Péptidos y Proteínas de Señalización Intracelular , Mycobacterium leprae/inmunología , Transducción de Señal/inmunología , Células TH1/inmunología , Células TH1/metabolismo , Adyuvantes Inmunológicos/metabolismo , Antígenos CD , Proteínas Portadoras/antagonistas & inhibidores , Proteínas Portadoras/biosíntesis , Células Cultivadas , Citocinas/fisiología , Proteínas de Unión al ADN/metabolismo , Regulación hacia Abajo/inmunología , Glicoproteínas/inmunología , Glicoproteínas/metabolismo , Humanos , Inmunoglobulinas/inmunología , Inmunoglobulinas/metabolismo , Líquido Intracelular/enzimología , Líquido Intracelular/metabolismo , Lepra/enzimología , Lepra/inmunología , Lepra/metabolismo , Ligandos , Activación de Linfocitos/inmunología , FN-kappa B/metabolismo , Transporte de Proteínas/inmunología , Proteínas Tirosina Quinasas/metabolismo , Proteínas Proto-Oncogénicas/biosíntesis , Proteínas Proto-Oncogénicas/metabolismo , Proteínas Proto-Oncogénicas c-fyn , Receptores de Superficie Celular , Factor de Transcripción STAT1 , Índice de Severidad de la Enfermedad , Proteína Asociada a la Molécula de Señalización de la Activación Linfocitaria , Miembro 1 de la Familia de Moléculas Señalizadoras de la Activación Linfocitaria , Proteínas de Dominio T Box , Células TH1/enzimología , Células TH1/microbiología , Transactivadores/metabolismo , Factores de Transcripción/biosíntesisRESUMEN
Production of the Th1 cytokine IFN-gamma by T cells is considered crucial for immunity against Mycobacterium tuberculosis infection. We evaluated IFN-gamma production in tuberculosis in the context of signaling molecules known to regulate Th1 cytokines. Two populations of patients who have active tuberculosis were identified, based on their T cell responses to the bacterium. High responder tuberculosis patients displayed significant M. tuberculosis-dependent T cell proliferation and IFN-gamma production, whereas low responder tuberculosis patients displayed weak or no T cell responses to M. tuberculosis. The expression of the signaling lymphocytic activation molecule (SLAM)-associated protein (SAP) on cells from tuberculosis patients was inversely correlated with IFN-gamma production in those individuals. Moreover, patients with a nonfunctional SAP gene displayed immune responses to M. tuberculosis similar to those of high responder tuberculosis patients. In contrast to SAP, T cell expression of SLAM was directly correlated with responsiveness to M. tuberculosis Ag. Our data suggest that expression of SAP interferes with Th1 responses whereas SLAM expression contributes to Th1 cytokine responses in tuberculosis. The study further suggests that SAP and SLAM might be focal points for therapeutic modulation of T cell cytokine responses in tuberculosis.
Asunto(s)
Proteínas Portadoras/biosíntesis , Regulación hacia Abajo/inmunología , Glicoproteínas/metabolismo , Inmunoglobulinas/metabolismo , Interferón gamma/antagonistas & inhibidores , Interferón gamma/biosíntesis , Péptidos y Proteínas de Señalización Intracelular , Tuberculosis/inmunología , Adyuvantes Inmunológicos/metabolismo , Adyuvantes Inmunológicos/fisiología , Anticuerpos Monoclonales/metabolismo , Antígenos CD , Proteínas Portadoras/genética , Proteínas Portadoras/metabolismo , Proteínas Portadoras/fisiología , Células Cultivadas , Cromosomas Humanos X/inmunología , Glicoproteínas/fisiología , Humanos , Inmunidad Celular/genética , Inmunoglobulinas/fisiología , Interferón gamma/farmacología , Interleucina-12/farmacología , Ligandos , Trastornos Linfoproliferativos/genética , Trastornos Linfoproliferativos/inmunología , Mycobacterium tuberculosis/inmunología , Receptores de Superficie Celular , Índice de Severidad de la Enfermedad , Transducción de Señal/genética , Transducción de Señal/inmunología , Proteína Asociada a la Molécula de Señalización de la Activación Linfocitaria , Miembro 1 de la Familia de Moléculas Señalizadoras de la Activación Linfocitaria , Tuberculosis/genética , Tuberculosis/microbiología , Regulación hacia Arriba/inmunologíaRESUMEN
T cell production of IFN-gamma contributes to host defense against infections by intracellular pathogens, including mycobacteria. Lepromatous leprosy, the dissminated from of infection caused by Mycobacterium leprae, is characterized by loss of cellular response against the pathogen and diminished Th1 cytokine production. Relieving bacterial burden in Ag-unresponsive patients might be achieved through alternative receptors that stimulate IFN-gamma production. We have previously shown that ligation of signaling lymphocytic activation molecule (SLAM) enhances IFN-gamma in mycobacterial infection; therefore, we investigated molecular pathways leading from SLAM activation to IFN-gamma production in human leprosy. The expression of the SLAM-associated protein (an inhibitory factor for IFN-gamma induction) on M. leprae-stimulated cells from leprosy patients was inversely correlated to IFN-gamma production. Howevwe, SLAM ligation or exposure of cell from lepromatous patients to a proinflammatory microenvironment down-regulated SLAM-associated protein expression. Moreover. SALAM activation induced a sequence of signaling proteins, including activation of the NF-kB complex, phosphorylation of Stat1, and induction of T-bet expression, resulting in the promotion a cascade of molecular events during signaling through SLAM in leprosy that cooperate to induce INF-gamma production and strongly suggest that SLAM might be a focal point for therapeutic modulation of the cell cytokine responses in diseases characterized by dysfunctional Th2 responses
Asunto(s)
Humanos , Lepra/inmunología , Lepra/microbiología , Interleucinas/inmunología , Interleucinas/sangre , Linfocitos T/inmunología , Linfocitos T/microbiología , Linfocitos/inmunología , Linfocitos/microbiología , Mycobacterium leprae/inmunología , Mycobacterium leprae/patogenicidadRESUMEN
Nerve damage is a clinical hallmark of leprosy and a major source of patient morbidity. We investigated the possibility that human Schwann cells are susceptible to cell death through the activation of Toll-like receptor 2 (TLR2), a pattern recognition receptor of the innate immune system. TLR2 was detected on the surface of human Schwann cell line ST88-14 and on cultured primary human Schwann cells. Activation of the human Schwann cell line and primary human Schwann cell cultures with a TLR2 agonist, a synthetic lipopeptide comprising the N-terminal portion of the putative Mycobacterium leprae 19-kDa lipoprotein, triggered an increase in the number of apoptotic cells. The lipopeptide-induced apoptosis of Schwann cells could be blocked by an anti-TLR2 monoclonal antibody. Schwann cells in skin lesions from leprosy patients were found to express TLR2. It was possible to identify in the lesions Schwann cells that had undergone apoptosis in vivo. The ability of M. leprae ligands to induce the apoptosis of Schwann cells through TLR2 provides a mechanism by which activation of the innate immune response contributes to nerve injury in leprosy.
Asunto(s)
Humanos , Apoptosis , Células Cultivadas , Células de Schwann/patología , Daño del ADN , Glicoproteínas de Membrana/análisis , Glicoproteínas de Membrana/fisiología , Lepra/inmunología , Lepra/patología , Inmunidad Innata , Lipoproteínas/fisiología , Receptores de Superficie Celular/análisis , Receptores de Superficie Celular/fisiologíaRESUMEN
The expression and activation of Toll-like receptors (TLRs) was investigated in leprosy, a spectral disease in which clinical manifestations correlate with the type of immune response mounted toward Mycobacterium leprae. TLR2-TLR1 heterodimers mediated cell activation by killed M. leprae, indicating the presence of triacylated lipoproteins. A genome-wide scan of M. leprae detected 31 putative lipoproteins. Synthetic lipopeptides representing the 19-kD and 33-kD lipoproteins activated both monocytes and dendritic cells. Activation was enhanced by type-1 cytokines and inhibited by type-2 cytokines. In addition, interferon (IFN)-gamma and granulocyte-macrophage colony-stimulating factor (GM-CSF) enhanced TLR1 expression in monocytes and dendritic cells, respectively, whereas IL-4 downregulated TLR2 expression. TLR2 and TLR1 were more strongly expressed in lesions from the localized tuberculoid form (T-lep) as compared with the disseminated lepromatous form (L-lep) of the disease. These data provide evidence that regulated expression and activation of TLRs at the site of disease contribute to the host defense against microbial pathogens.
Asunto(s)
Humanos , Animales , Ratones , Citocinas/fisiología , Glicoproteínas de Membrana/análisis , Glicoproteínas de Membrana/fisiología , Lepra/inmunología , Inmunidad Innata , Lipoproteínas/análisis , Receptores de Superficie Celular/análisis , Receptores de Superficie Celular/fisiologíaAsunto(s)
/biosíntesis , /fisiología , /genética , /metabolismo , Citocinas/biosíntesis , Células TH1/inmunología , Células TH1/metabolismo , Glicoproteínas de Membrana/biosíntesis , Glicoproteínas de Membrana/fisiología , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/metabolismo , Lepra Tuberculoide/inmunología , Lepra Tuberculoide/metabolismo , Lepra Tuberculoide/patología , Lepra Lepromatosa/inmunología , Lepra Lepromatosa/metabolismo , Lepra Lepromatosa/patología , Inmunidad Celular , /biosíntesis , Ligandos , Monocitos/inmunología , Monocitos/metabolismo , Mycobacterium leprae/inmunologíaAsunto(s)
Antígenos CD1/inmunología , Antígenos CD1/metabolismo , Antígenos Bacterianos/inmunología , Antígenos Bacterianos/metabolismo , Antígenos/biosíntesis , Glucolípidos/inmunología , Glucolípidos/metabolismo , Lepra/inmunología , Lepra/patología , Mycobacterium leprae/inmunología , Proteínas/biosíntesis , Receptores Inmunológicos/biosíntesis , Ácidos Micólicos/inmunología , Ácidos Micólicos/metabolismoRESUMEN
Reported herein are 13 borderline lepromatous (BL) or subpolar lepromatous (LLs) patients who presented with or developed delayed-type hypersensitivity (DTH) reactions after initiation of antibacterial therapy, but who subsequently developed erythema nodosum leprosum (ENL), the DTH to ENL group. During the same time, three LLs patients had ENL followed by relapse-associated DTH, a significant (p < 0.05) difference in sequence of the two conditions. The DTH to ENL group had statistically significant higher biopsy indexes at the time of diagnosis of the DTH reaction compared with two DTH control groups, 7 multibacillary patients presenting with DTH reactions and 15 BL or LLs who developed DTH reactions after starting treatment but had no ENL. DTH-associated histologic changes were less well developed in the DTH to ENL group than in either of the two control groups. In the DTH to ENL group, 77% required prednisone in addition to thalidomide to achieve a complete remission in contrast to only 10% of 21 ENL clinical controls. In the DTH to ENL group, the classical histologic ENL pattern was present in only 31% of these patients, in contrast to 88% of 33 ENL histologic controls. In 9 of 9 of the DTH to ENL patients studied, after the ENL remitted, Mycobacterium leprae-sonicate-stimulated lymphocyte transformation tests gave stimulation indexes within the range of our tuberculoid (TT) and borderline tuberculoid (BT) patients, in contrast to absent responses in 6 ordinary, longterm-treated patients who had had ENL.