RESUMO
Tuberculosis (TB) is one of the world's most pernicious diseases mainly due to immune evasion strategies displayed by its causative agent Mycobacterium tuberculosis (Mtb). Blood monocytes (Mos) represent an important source of DCs during chronic infections; consequently, the alteration of their differentiation constitutes an escape mechanism leading to mycobacterial persistence. We evaluated whether the CD16(+)/CD16(-) Mo ratio could be associated with the impaired Mo differentiation into DCs found in TB patients. The phenotype and ability to stimulate Mtb-specific memory clones DCs from isolated Mo subsets were assessed. We found that CD16(-) Mos differentiated into CD1a(+) DC-SIGN(high) cells achieving an efficient recall response, while CD16(+) Mos differentiated into a CD1a(-) DC-SIGN(low) population characterized by a poor mycobacterial Ag-presenting capacity. The high and sustained phosphorylated p38 expression observed in CD16(+) Mos was involved in the altered DC profile given that its blockage restored DC phenotype and its activation impaired CD16(-) Mo differentiation. Furthermore, depletion of CD16(+) Mos indeed improved the differentiation of Mos from TB patients toward CD1a(+) DC-SIGN(high) DCs. Therefore, Mos from TB patients are less prone to differentiate into DCs due to their increased proportion of CD16(+) Mos, suggesting that during Mtb infection Mo subsets may have different fates after entering the lungs.
Assuntos
Células Dendríticas/patologia , Monócitos/patologia , Receptores de IgG/metabolismo , Tuberculose/imunologia , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismo , Adulto , Antígenos CD1/imunologia , Antígenos CD1/metabolismo , Diferenciação Celular/imunologia , Células Dendríticas/enzimologia , Células Dendríticas/imunologia , Células Dendríticas/metabolismo , Feminino , Proteínas Ligadas por GPI/imunologia , Proteínas Ligadas por GPI/metabolismo , Humanos , Masculino , Pessoa de Meia-Idade , Monócitos/enzimologia , Monócitos/imunologia , Monócitos/metabolismo , Mycobacterium tuberculosis/imunologia , Receptores de IgG/imunologia , Transdução de Sinais/imunologia , Transdução de Sinais/fisiologia , Tuberculose/enzimologia , Tuberculose/metabolismo , Tuberculose/microbiologia , Adulto Jovem , Proteínas Quinases p38 Ativadas por Mitógeno/imunologiaRESUMO
DTH (delayed type hypersensitivity) reactions are secondary cellular immune responses that appear 24-72 h after antigen exposure. Tuberculous pleurisy is a common manifestation of extrapulmonary TB (tuberculosis) and is considered a human model of Th1-mediated DTH. In order to identify functional cross-talk among cellular populations sited in this inflammatory microenvironment, we analysed phenotypic and functional features of human B-cells isolated from the PF (pleural fluid) of TB patients. Freshly isolated PF-B-cells displayed a lower expression of CD20, CD1d and HLA-DR, and a higher expression of CD95, CD38, CD25, CXCR3 (CXC chemokine receptor 3) and CXCR4 (CXC chemokine receptor 4) than their PB (peripheral blood) counterparts, suggesting a non-classical in situ activation. Although memory PF-T-cell frequencies were increased, the frequencies of memory PF-B-cells were not. We demonstrated that, upon stimulation with γ-irradiated M. tuberculosis, mycobacterially secreted proteins or a lectin mitogen, PF-B-cells had a strong activation and produced IL-10 by a mechanism that was dependent on bystander activation of CD19(-) PF cells. Besides, within PF cells, B-cells diminished in vitro M. tuberculosis-induced IFN (interferon)-γ production by T-cells and NK (natural killer) cells in an IL-10-dependent manner. Finally, we found that the lower the frequency of B-cells, the higher the ratio of IFN-γ/IL-10 within PF. Thus our results suggest that B-cells can regulate a human DTH reaction induced by M. tuberculosis.
Assuntos
Linfócitos B/metabolismo , Hipersensibilidade Tardia/imunologia , Interferon gama/biossíntese , Células Matadoras Naturais/metabolismo , Linfócitos T/metabolismo , Tuberculose Pleural/microbiologia , Linfócitos B/imunologia , Humanos , Imunidade Celular/imunologia , Interleucina-10/imunologia , Células Matadoras Naturais/imunologia , Mycobacterium tuberculosis/imunologia , Linfócitos T/imunologia , Tuberculose Pleural/imunologiaRESUMO
Tuberculosis pathogenesis was earlier thought to be mainly related to the host but now it appears to be clear that bacterial factors are also involved. Genetic variability of Mycobacterium tuberculosis (Mtb) could be slight but it may lead to sharp phenotypic differences. We have previously reported that nonopsonized Mtb H37Rv induce apoptosis of polymorphonuclear neutrophils (PMNs) by a mechanism that involves the p38 pathway. Here we evaluated the capability to induce PMN apoptosis of two prevalent Mtb lineages in Argentina, the Latin America and Mediterranean (LAM), and Haarlem, using the H37Rv as a reference strain. Results showed that LAM strains strongly induced apoptosis of PMN which correlated with the induction of reactive oxygen species (ROS) production and p38 activation. Interestingly, the highly prosperous multidrug-resistant M strain, belonging to the Haarlem lineage, lacked the ability to activate and to induce PMN apoptosis as a consequence of (1) a weak ROS production and (2) the contribution of antiapoptotic mechanisms mediated at least by ERK. Although with less skill, M is able to enter the PMN so that phenotypic differences could lead PMN to be a reservoir allowing some pathogens to prevail and persist over other strains in the community.
Assuntos
Apoptose/imunologia , Mycobacterium tuberculosis/imunologia , Neutrófilos/imunologia , Explosão Respiratória/imunologia , Antígenos CD/metabolismo , Antígeno CD11b/metabolismo , Moléculas de Adesão Celular/metabolismo , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Proteínas Ligadas por GPI/metabolismo , Humanos , Mycobacterium tuberculosis/isolamento & purificação , Neutrófilos/metabolismo , Neutrófilos/microbiologia , Fagocitose/imunologia , Espécies Reativas de Oxigênio/metabolismo , Regulação para Cima/imunologia , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
BACKGROUND: The proinflammatory cytokine interleukin 17 (IL-17) plays an important role in immune responses but it is also associated with tissue-damaging inflammation. So, we evaluated the ability of Mycobacterium tuberculosis clinical isolates to induce IL-17 in tuberculosis (TB) patients and in healthy human tuberculin reactors (PPD(+)HD). METHODS: IL-17, interferon γ (IFN-γ), and interleukin 23 (IL-23) receptor expression were evaluated ex vivo and cultured peripheral blood mononuclear cells from TB and PPD(+)HD stimulated with irradiated clinical isolates from multidrug resistant (MDR) outbreaks M (Haarlem family) and Ra (Latin American-Mediterranean family), as well as drug-susceptible isolates belonging to the same families and laboratory strain H37Rv for 48 hours in T-cell subsets by flow cytometry. RESULTS: We observed that: (1) MDR strains M and Ra are stronger IL-17 inducers than drug-susceptible Mtb strains of the Haarlem and Latin American-Mediterranean families, (2) MDR-TB patients show the highest IL-17 expression that is independent on the strain, (3) IL-17 expression is dependent on CD4(+) and CD8(+) T cells associates with persistently high antigen load. CONCLUSIONS: IL-17--producing T cells could play an immunopathological role in MDR-TB promoting severe tissue damage, which may be associated with the low effectiveness of the second-line drugs employed in the treatment.
Assuntos
Antígenos de Bactérias/imunologia , Linfócitos T CD4-Positivos/metabolismo , Linfócitos T CD8-Positivos/metabolismo , Mycobacterium tuberculosis/imunologia , Subpopulações de Linfócitos T/imunologia , Tuberculose Resistente a Múltiplos Medicamentos/imunologia , Adulto , Células Cultivadas , Feminino , Humanos , Interferon gama/metabolismo , Interleucina-17/metabolismo , Masculino , Pessoa de Meia-Idade , Receptores de Antígenos de Linfócitos T gama-delta/imunologia , Receptores de Antígenos de Linfócitos T gama-delta/metabolismo , Receptores de Interleucina/metabolismo , Subpopulações de Linfócitos T/metabolismo , Adulto JovemRESUMO
We previously demonstrated that Bordetella pertussis, the etiologic agent of whooping cough, is able to survive inside human macrophages. The aim of this study was to examine the influence of macrophage polarization in the development of B. pertussis intracellular infections. To this end, primary human monocytes were differentiated into M1, M2a, or M2c macrophages and further infected with B. pertussis. Infected M1 macrophages showed a proinflammatory response evidenced by the production of TNF-α, IL-12p70, and IL-6. Conversely, infection of M2a and M2c macrophages did not induce TNF-α, IL-12p70, nor IL-6 at any time postinfection but showed a significant increase of M2 markers, such as CD206, CD163, and CD209. Interestingly, anti-inflammatory cytokines, like IL-10 and TGF-ß, were induced after infection in the 3 macrophage phenotypes. B. pertussis phagocytosis by M1 macrophages was lower than by M2 phenotypes, which may be ascribed to differences in the expression level of B. pertussis docking molecules on the surface of the different phenotypes. Intracellular bactericidal activity was found to be significantly higher in M1 than in M2a or M2c cells, but live bacteria were still detected within the 3 phenotypes at the late time points after infection. In summary, this study shows that intracellular B. pertussis is able to survive regardless of the macrophage activation program, but its intracellular survival proved higher in M2 compared with the M1 macrophages, being M2c the best candidate to develop into a niche of persistence for B. pertussis.
Assuntos
Ativação de Macrófagos , Coqueluche , Bordetella pertussis , Humanos , Interleucina-6/metabolismo , Macrófagos/metabolismo , Fator de Necrose Tumoral alfa/metabolismo , Coqueluche/metabolismoRESUMO
Tuberculous pleurisy, one of the most common manifestations of extrapulmonary tuberculosis, is characterized by a T-cell-mediated hypersensitivity reaction along with a Th1 immune profile. In this study, we investigated functional cross-talk among T and NK cells in human tuberculous pleurisy. We found that endogenously activated pleural fluid-derived NK cells express high ICAM-1 levels and induce T-cell activation ex vivo through ICAM-1. Besides, upon in vitro stimulation with monokines and PAMP, resting peripheral blood NK cells increased ICAM-1 expression leading to cellular activation and Th1 polarization of autologous T cells. Furthermore, these effects were abolished by anti-ICAM-1 Ab. Hence, NK cells may contribute to the adaptive immune response by a direct cell-contact-dependent mechanism in the context of Mycobacterium tuberculosis infection.
Assuntos
Molécula 1 de Adesão Intercelular/metabolismo , Células Matadoras Naturais/imunologia , Mycobacterium tuberculosis , Linfócitos T/imunologia , Tuberculose Pleural/imunologia , Adulto , Antígeno CD11a/imunologia , Antígeno CD56/imunologia , Comunicação Celular/imunologia , Cisteína/análogos & derivados , Cisteína/farmacologia , Humanos , Molécula 1 de Adesão Intercelular/efeitos dos fármacos , Molécula 1 de Adesão Intercelular/imunologia , Interleucina-12/farmacologia , Interleucina-15/farmacologia , Interleucina-18/farmacologia , Lipopolissacarídeos/farmacologia , Lipoproteínas/farmacologia , Pessoa de Meia-Idade , Fosfotransferases (Aceptor do Grupo Fosfato)RESUMO
During a chronic infection such as tuberculosis, the pool of tissue dendritic cells (DC) must be renewed by recruitment of both circulating DC progenitors and monocytes (Mo). However, the microenvironment of the inflammatory site affects Mo differentiation. As DC are critical for initiating a Mycobacterium tuberculosis-specific T-cell response, we argue that interference of M. tuberculosis with a correct DC generation would signify a mechanism of immune evasion. In this study, we showed that early interaction of γ-irradiated M. tuberculosis with Mo subverts DC differentiation in vitro. We found that irradiated M. tuberculosis effect involves (1) the loss of a significant fraction of monocyte population and (2) an altered differentiation process of the surviving monocyte subpopulation. Moreover, in the absence of irradiated M. tuberculosis, DC consist in a major DC-specific intercellular adhesion molecule 3-grabbing non-integrin receptor (DC-SIGN(high))/CD86(low) and minor DC-SIGN(low)/CD86(high) subpopulations, whereas in the presence of bacteria, there is an enrichment of DC-SIGN(low)/CD86(high) population. Besides, this population enlarged by irradiated M. tuberculosis, which is characterized by a reduced CD1b expression, correlates with a reduced induction of specific T-lymphocyte proliferation. The loss of CD1molecules partially involves toll-like receptors (TLR-2)/p38 MAPK activation. Finally, several features of Mo, which have been differentiated into DC in the presence of irradiated M. tuberculosis, resemble the features of DC obtained from patients with active tuberculosis. In conclusion, we suggest that M. tuberculosis escapes from acquired immune response in tuberculosis may be caused by an altered differentiation into DC leading to a poor M. tuberculosis-specific T-cell response.
Assuntos
Células Dendríticas/imunologia , Células Dendríticas/microbiologia , Adulto , Antígenos CD1/metabolismo , Antígeno B7-2/metabolismo , Moléculas de Adesão Celular/metabolismo , Diferenciação Celular/imunologia , Proliferação de Células , Células Cultivadas , Humanos , Interleucina-10/metabolismo , Lectinas Tipo C/metabolismo , Teste de Cultura Mista de Linfócitos , Macrófagos/imunologia , Receptor de Manose , Lectinas de Ligação a Manose/metabolismo , Pessoa de Meia-Idade , Mycobacterium tuberculosis/patogenicidade , Receptores de Superfície Celular/metabolismo , Receptor 2 Toll-Like/metabolismo , Tuberculose/imunologia , Tuberculose/fisiopatologia , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
In Argentina, multidrug-resistant tuberculosis (MDR-TB) outbreaks emerged among hospitalized patients with AIDS in the early 1990s and thereafter disseminated to the immunocompetent community. Epidemiological, bacteriological, and genotyping data allowed the identification of certain MDR Mycobacterium tuberculosis outbreak strains, such as the so-called strain M of the Haarlem lineage and strain Ra of the Latin America and Mediterranean lineage. In the current study, we evaluated the immune responses induced by strains M and Ra in peripheral blood mononuclear cells from patients with active MDR-TB or fully drug-susceptible tuberculosis (S-TB) and in purified protein derivative-positive healthy controls (group N). Our results demonstrated that strain M was a weaker gamma interferon (IFN-gamma) inducer than H37Rv for group N. Strain M induced the highest interleukin-4 expression in CD4+ and CD8+ T cells from MDR- and S-TB patients, along with the lowest cytotoxic T-lymphocyte (CTL) activity in patients and controls. Hence, impairment of CTL activity is a hallmark of strain M and could be an evasion mechanism employed by this strain to avoid the killing of macrophages by M-specific CTL effectors. In addition, MDR-TB patients had an increased proportion of circulating regulatory T cells (Treg cells), and these cells were further expanded upon in vitro M. tuberculosis stimulation. Experimental Treg cell depletion increased IFN-gamma expression and CTL activity in TB patients, with M- and Ra-induced CTL responses remaining low in MDR-TB patients. Altogether, these results suggest that immunity to MDR strains might depend upon a balance between the individual host response and the ability of different M. tuberculosis genotypes to drive Th1 or Th2 profiles.
Assuntos
Subpopulações de Linfócitos T/imunologia , Linfócitos T Reguladores/imunologia , Células Th1/imunologia , Tuberculose Resistente a Múltiplos Medicamentos/genética , Tuberculose Resistente a Múltiplos Medicamentos/imunologia , Argentina , Citocinas/biossíntese , Citocinas/imunologia , Surtos de Doenças , Citometria de Fluxo , Humanos , Tuberculose Resistente a Múltiplos Medicamentos/epidemiologiaRESUMO
The role of CD16(-) and CD16(+) Mo subsets in human TB remains unknown. Our aim was to characterize Mo subsets from TB patients and to assess whether the inflammatory milieu from TB pleurisy modulate their phenotype and recruitment. We found an expansion of peripheral CD16(+) Mo that correlated with disease severity and with TNF-α plasma levels. Circulating Mo from TB patients are activated, showing a higher CD14, CD16, and CD11b expression and Mtb binding than HS. Both subsets coexpressed CCR2/CCR5, showing a potential ability to migrate to the inflammatory site. In tuberculous PF, the CD16(+) subset was the main Mo/MΦ population, accumulation that can be favored by the induction of CD16 expression in CD16(-) Mo triggered by soluble factors found in this inflammatory milieu. CD16(+) Mo in PF were characterized by a high density of receptors for Mtb recognition (DC-SIGN, MR, CD11b) and for lipid-antigens presentation (CD1b), allowing them to induce a successful, specific T cell proliferation response. Hence, in tuberculous PF, CD16(+) Mo constitute the main APC population; whereas in PB, their predominance is associated with the severity of pulmonary TB, suggesting a paradoxical role of the CD16(+) Mo subset that depends on the cellular localization.
Assuntos
Monócitos/imunologia , Receptores CCR2/análise , Receptores CCR5/análise , Receptores de IgG/análise , Tuberculose Pleural/imunologia , Tuberculose/imunologia , Adulto , Idoso , Células Apresentadoras de Antígenos/imunologia , Células Apresentadoras de Antígenos/metabolismo , Separação Celular , Citocinas/análise , Citocinas/sangue , Ensaio de Imunoadsorção Enzimática , Feminino , Citometria de Fluxo , Proteínas Ligadas por GPI/análise , Proteínas Ligadas por GPI/imunologia , Proteínas Ligadas por GPI/metabolismo , Humanos , Masculino , Pessoa de Meia-Idade , Monócitos/metabolismo , Derrame Pleural/imunologia , Derrame Pleural/metabolismo , Receptores CCR2/imunologia , Receptores CCR2/metabolismo , Receptores CCR5/imunologia , Receptores CCR5/metabolismo , Receptores de IgG/imunologia , Receptores de IgG/metabolismo , Tuberculose/metabolismo , Tuberculose Pleural/metabolismoRESUMO
Tuberculous pleurisy allows the study of human cells at the site of active Mycobacterium tuberculosis infection. In this study, we found that among pleural fluid (PF) lymphocytes, natural killer (NK) cells are a major source of early gamma interferon (IFN-gamma) upon M. tuberculosis stimulation, leading us to investigate the mechanisms and molecules involved in this process. We show that the whole bacterium is the best inducer of IFN-gamma, although a high-molecular-weight fraction of culture filtrate proteins from M. tuberculosis H37Rv and the whole-cell lysate also induce its expression. The mannose receptor seems to mediate the inhibitory effect of mannosylated lipoarabinomannan, and Toll-like receptor 2 and 4 agonists activate NK cells but do not induce IFN-gamma like M. tuberculosis does. Antigen-presenting cells (APC) and NK cells bind M. tuberculosis, and although interleukin-12 is required, it is not sufficient to induce IFN-gamma expression, indicating that NK cell-APC contact takes place. Indeed, major histocompatibility complex class I, adhesion, and costimulatory molecules as well as NK receptors regulate IFN-gamma induction. The signaling pathway is partially inhibited by dexamethasone and sensitive to Ca2+ flux and cyclosporine. Inhibition of p38 and extracellular-regulated kinase mitogen-activated protein kinase pathways reduces the number of IFN-gamma+ NK cells. Phosphorylated p38 (p-p38) is detected in ex vivo PF-NK cells, and M. tuberculosis triggers p-p38 in PF-NK cells at the same time that binding between NK and M. tuberculosis reaches its maximum value. Thus, interplay between M. tuberculosis and NK cells/APC triggering IFN-gamma would be expected to play a beneficial role in tuberculous pleurisy by helping to maintain a type 1 profile.
Assuntos
Células Apresentadoras de Antígenos/imunologia , Interferon gama/biossíntese , Células Matadoras Naturais/imunologia , Lectinas Tipo C/imunologia , Lectinas de Ligação a Manose/imunologia , Mycobacterium tuberculosis/imunologia , Receptores de Superfície Celular/imunologia , Receptor 2 Toll-Like/imunologia , Receptor 4 Toll-Like/imunologia , Tuberculose Pleural/imunologia , Adulto , Idoso , Células Apresentadoras de Antígenos/microbiologia , Antígenos de Superfície/imunologia , Aderência Bacteriana , Proteínas de Bactérias/imunologia , Misturas Complexas/imunologia , MAP Quinases Reguladas por Sinal Extracelular/antagonistas & inibidores , Antígenos de Histocompatibilidade Classe I/imunologia , Humanos , Células Matadoras Naturais/microbiologia , Lipopolissacarídeos/imunologia , Receptor de Manose , Pessoa de Meia-Idade , Derrame Pleural/imunologia , Derrame Pleural/microbiologia , Tuberculose Pleural/microbiologia , Proteínas Quinases p38 Ativadas por Mitógeno/antagonistas & inibidoresRESUMO
Tuberculous pleuritis usually shows lymphocytic preponderance, but neutrophils are also present. Therefore, pleuritis is a good model for the study of neutrophil fate at sites of active Mycobacterium tuberculosis infection. We have previously demonstrated in vitro that M. tuberculosis-induced neutrophil apoptosis involves p38 mitogen protein kinase activation through Toll-like receptor 2. Herein, we demonstrate that, in tuberculous pleuritis, neutrophil apoptosis increases together with the expression of Toll-like receptor 2 and phosphorylated p38 (p-p38) kinase. In addition, receptors associated with activation/apoptotis (CD11b, CD64, tumor necrosis factor receptor, and Fas ligand) are up-regulated, together with a loss of CD16 expression. However, neutrophils express CD86, CD83, and major histocompatibility complex class II antigens, acquiring dendritic cell (DC) characteristics. Therefore, the cytokine milieu in the pleural space may influence signaling pathways on activated neutrophils, thereby inducing apoptosis and inhibiting their proinflammatory capacity, as well as allowing them acquire DC characteristics that influence the immune response.
Assuntos
Apoptose/fisiologia , Diferenciação Celular/fisiologia , Células Dendríticas/patologia , Neutrófilos/patologia , Derrame Pleural/sangue , Tuberculose Pulmonar/sangue , Antígenos CD/sangue , Células Dendríticas/fisiologia , Citometria de Fluxo , Humanos , Neutrófilos/fisiologia , Fenótipo , Valores de ReferênciaRESUMO
Tuberculous pleuritis is a good model for the study of specific cells at the site of active Mycobacterium tuberculosis (Mtb) infection. We investigated the frequency and phenotype of NK cells in paired samples of peripheral blood and pleural fluid (PF) from patients with tuberculosis (TB) or parapneumonic infection. We demonstrated for the first time a reduction of NK cells in PF from TB with an enrichment in the CD56brightCD16- subset. In agreement, in PF NK cells we observed an increased expression of CD94, NKG2A, CD62L, and CCR7 molecules and lower expression of Bcl-2 and perforin. The activation markers CD69 and HLA-DR were also increased. The enrichment in the CD56bright subset was due to an increased susceptibility to apoptosis of CD56+CD16+ NK cells mediated by heat-labile and stable soluble factors present in tuberculous effusions and not in PF from other etiologies. Furthermore, in TB patients, Mtb-induced IFN-gamma production by PF NK cells was not dependent on the presence of CD3+, CD19+, and CD14+ cells, suggesting a direct interaction of CD56bright cells with Mtb and/or the involvement of other accessory cells present at the site of Mtb infection.
Assuntos
Apoptose/imunologia , Células Matadoras Naturais/imunologia , Células Matadoras Naturais/patologia , Tuberculose Pleural/imunologia , Tuberculose Pleural/patologia , Adulto , Idoso , Antígenos CD/metabolismo , Antígenos CD19/metabolismo , Complexo CD3/metabolismo , Antígeno CD56/metabolismo , Proteínas Ligadas por GPI , Humanos , Técnicas In Vitro , Interferon gama/biossíntese , Células Matadoras Naturais/classificação , Receptores de Lipopolissacarídeos/metabolismo , Subpopulações de Linfócitos/imunologia , Subpopulações de Linfócitos/patologia , Pessoa de Meia-Idade , Fenótipo , Derrame Pleural/imunologia , Derrame Pleural/patologia , Receptores de IgG/metabolismoRESUMO
The activation of circulating polymorphonuclear neutrophils (PMN) from patients with active tuberculosis (TB-PMN) may be associated with induction of apoptosis. Spontaneous or Mycobacterium tuberculosis (MTB)-induced apoptosis of PMN were evaluated by microscopy, DNA content, and their binding to Annexin V at 0, 3, and 18 h. In addition, the expression of CD11b and of CD16 were evaluated as parameters of activation and apoptosis, respectively. Recently isolated TB-PMN showed a higher CD11b expression than normal PMN (N-PMN), but there were no features of apoptosis, even though an enhancement of Fas expression was observed. Spontaneous apoptosis was accelerated in TB-PMN at 3 h, but no differences were observed in TB- and N-PMN at 18 h of culture. When stimulated with MTB, both TB- and N-PMN steadily increased CD11b expression along the culture period. MTB induced apoptosis of N-PMN at 3 h with loss of CD16 expression. By contrast, MTB delayed the apoptotic rate of TB-PMN, preserving the CD16 receptor at 3 h, whereas it accelerated apoptosis at 18 h, increasing at the same time the expression of CD11b. Taken together, these data suggest that the acceleration of apoptosis observed in TB-PMN could be associated with the MTB-induced activation.
Assuntos
Mycobacterium tuberculosis/patogenicidade , Neutrófilos/microbiologia , Neutrófilos/patologia , Tuberculose/sangue , Anexina A5/metabolismo , Apoptose/fisiologia , Antígeno CD11b/metabolismo , Células Cultivadas , Humanos , Interleucina-8/metabolismo , Neutrófilos/metabolismo , Receptores de IgG/metabolismo , Tuberculose/microbiologia , Fator de Necrose Tumoral alfa/metabolismo , Receptor fas/metabolismoRESUMO
Polymorphonuclear neutrophils (PMN) exposed to Mycobacterium tuberculosis display bactericidal responses and produce inflammatory proteins. This PMN-mediated inflammatory response is regulated by an activation of the apoptotic program, which collaborates to avoid tissue injury. In vitro, circulating PMN from patients with tuberculosis (TB) show an increased spontaneous apoptosis, and M. tuberculosis-induced activation accelerates the PMN apoptosis. In this study, we evaluated the mechanisms involved in spontaneous and M. tuberculosis-induced apoptosis. We demonstrate that apoptosis of PMN is not induced by lipoarabinomannan or by a whole-cell lysate of M. tuberculosis and that neither tumor necrosis factor alpha nor CD11b, CD14, and Fcgamma receptors are involved. Apoptosis of PMN from patients with active TB (TB-PMN) is induced by the interaction with the whole M. tuberculosis via Toll-like receptor 2 (TLR2), and, in contrast to spontaneous apoptosis, it involves the p38 mitogen-activated protein kinase (MAPK) pathway. These results correlate with a high expression of phosphorylated p38 (p-p38) in circulating TB-PMN and with the ability of M. tuberculosis to induce in vitro the expression of p-p38 in PMN. Therefore, when the bacterial burden is low, TB-PMN could be detecting nonopsonized M. tuberculosis via TLR2, leading to the activation of the p38 MAPK pathway, which in turn would induce PMN activation and apoptosis. This mechanism needs further confirmation at the site of infection.