RESUMO
Controversial results have been observed in mouse models regarding the role of lymphoid tissues in prion pathogenesis. To investigate the role of dendritic cells (DC), we used a transgenic mouse model. In this model (CD11c-N17Rac1), a significant reduction of CD8+ CD11c(hi) DC has been described, and the remaining CD8+ DC demonstrate a reduced capacity for the uptake of apoptotic cells. After intraperitoneal prion infection, significantly longer incubation times were observed in CD11c-N17Rac1 mice than in controls, indicating that a defect in CD8+ CD11c(hi) DC significantly impedes neuroinvasion after intraperitoneal infection. In contrast, no distinct differences were observed between CD11c-N17Rac1 mice and controls after oral infection. This provides evidence that oral and intraperitoneal prion infections differ in lymphoreticular requirements.
Assuntos
Encéfalo/metabolismo , Células Dendríticas Foliculares/metabolismo , Doenças Priônicas/transmissão , Príons/metabolismo , Administração Oral , Animais , Antígeno CD11c/metabolismo , Antígenos CD8/metabolismo , Imuno-Histoquímica , Injeções Intraperitoneais , Camundongos , Camundongos Transgênicos , Doenças Priônicas/metabolismo , Príons/administração & dosagemRESUMO
In addition to their bridging function between innate and adaptive immunity, dendritic cells (DCs) may also contribute to primary resistance against infection. Here we analyzed the role of DCs during infection with Listeria monocytogenes by performing systemic in vivo depletion of these cells. We showed that CD8alpha(+) DCs were crucial for L. monocytogenes spreading and proliferation in the spleen. Efficient and rapid uptake of L. monocytogenes by CD8alpha(+) DCs required the small GTPase Rac1 and is a general characteristic of this DC subpopulation in filtering particles out of the blood. Thus, CD8alpha(+) DCs appear to play an important role for efficient bacterial entry into the spleen, which is of relevance for subsequent immune responses.
Assuntos
Antígenos CD8/análise , Células Dendríticas/imunologia , Listeria monocytogenes , Listeriose/imunologia , Baço/microbiologia , Animais , Antígeno CD11c/análise , Células Dendríticas/microbiologia , Células Dendríticas/transplante , Granulócitos/imunologia , Listeriose/enzimologia , Ativação Linfocitária , Camundongos , Camundongos Endogâmicos , Neuropeptídeos/genética , Neuropeptídeos/metabolismo , Baço/citologia , Baço/imunologia , Linfócitos T/imunologia , Proteínas rac de Ligação ao GTP/genética , Proteínas rac de Ligação ao GTP/metabolismo , Proteínas rac1 de Ligação ao GTPRESUMO
To better understand the influence of cytoskeletal regulation on dendritic cell (DC) function in vivo, the Rho guanosine triphosphatase (GTPase) Rac1 was selectively inhibited in DCs in transgenic (Tg) mice. Although transgene expression did not interfere with the migratory capacities of DC in vivo, a decreased uptake of fluorescent probes was observed. Interestingly, the absence of full Rac1 function most strongly affected the development and function of CD8+ DCs. Apoptotic cell uptake was severely reduced in Tg mice, impairing subsequent DC-mediated cross-presentation and priming of bacteria-specific T-cell responses. These findings highlight a special role for Rac1 in the capacity of CD8+ DCs to endocytose apoptotic cells and prime T cells via cross-presentation.
Assuntos
Apresentação de Antígeno/imunologia , Células Dendríticas/imunologia , Células Dendríticas/metabolismo , Proteínas rac1 de Ligação ao GTP/genética , Proteínas rac1 de Ligação ao GTP/metabolismo , Animais , Apoptose/imunologia , Antígeno CD11c/genética , Antígeno CD11c/metabolismo , Antígenos CD8/metabolismo , Diferenciação Celular/imunologia , Movimento Celular/imunologia , Células Dendríticas/citologia , Endocitose/imunologia , Feminino , Listeriose/imunologia , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos MutantesRESUMO
H2-M3-restricted T cells respond more rapidly to primary Listeria monocytogenes infection than conventional MHC class Ia-restricted T cells. Reinfection with L. monocytogenes, while inducing explosive proliferation of H2-K(d)-restricted T cells, does not stimulate significant expansion of H2-M3-restricted CTL. These disparate responses to reinfection are apparent within 5 days of primary L. monocytogenes infection. However, H2-M3-restricted memory T cells are generated, and are indistinguishable from classically restricted T cells in terms of cell surface memory markers and longevity. Early responses of H2-M3- and H2-K(d)-restricted memory T cells to reinfection are similar, with increases in size and expression of activation markers. Interestingly, priming of H2-M3-restricted T cells with an L. monocytogenes-derived N-formyl peptide plus anti-CD40 generates memory T cells that expand upon re-exposure to Ag during L. monocytogenes infection. Our data indicate that disparate H2-M3- and MHC class Ia-restricted memory T cell responses reflect intrinsic differences between these T cell populations. Although distinct proliferative programs appear to be hardwired in these populations during primary L. monocytogenes infection, under different inflammatory circumstances M3-restricted T cell populations can maintain the ability to expand upon re-exposure to Ag.
Assuntos
Toxinas Bacterianas , Antígenos de Histocompatibilidade Classe I/imunologia , Memória Imunológica , Ativação Linfocitária , Subpopulações de Linfócitos T/citologia , Subpopulações de Linfócitos T/imunologia , Animais , Antígenos de Bactérias/imunologia , Biomarcadores/análise , Divisão Celular/genética , Divisão Celular/imunologia , Sobrevivência Celular/genética , Sobrevivência Celular/imunologia , Feminino , Antígenos H-2/análise , Proteínas de Choque Térmico/imunologia , Proteínas Hemolisinas , Antígenos de Histocompatibilidade Classe I/análise , Imunização , Imunização Secundária , Memória Imunológica/genética , Listeria monocytogenes/imunologia , Listeriose/imunologia , Listeriose/microbiologia , Ativação Linfocitária/genética , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Fragmentos de Peptídeos/imunologia , Subpopulações de Linfócitos T/metabolismo , Subpopulações de Linfócitos T/microbiologia , Linfócitos T Citotóxicos/citologia , Linfócitos T Citotóxicos/imunologia , Linfócitos T Citotóxicos/metabolismo , Linfócitos T Citotóxicos/microbiologiaRESUMO
Several recent studies have demonstrated that T-helper cell-dependent events during the initial priming period are required for the generation of CD8(+) T cell-mediated protective immunity. The underlying mechanisms of this phenomenon have not yet been determined, mostly because of difficulties in studying memory T cells or their precursor populations at early stages during immune responses. We identified IL-7 receptor (CD127) surface expression as a marker for long-living memory T cells, most importantly allowing the distinction between memory and effector T cells early after in vivo priming. The combination of surface staining for CD127 and CD62L further separates between two functionally distinct memory cell subsets, which are similar (if not identical) to cell subsets recently described as central memory T cells (CD127(high) and CD62L(high)) and peripheral effector memory T cells (CD127(high) and CD62L(low)). Using this new tool of memory T cell analysis, we demonstrate that CD8(+) T cell priming in the absence of T cell help or CD40L specifically alters the generation of the effector memory T cell subset, which appears to be crucial for immediate memory responses and long-term maintenance of effective protective immunity. Our data reveal a unique strategy to obtain information about the quality of long-term protective immunity early during an immune response, a finding that may be applied in a variety of clinical settings, including the rapid monitoring of vaccination success.
Assuntos
Ligante de CD40/imunologia , Linfócitos T CD8-Positivos/imunologia , Memória Imunológica , Receptores de Interleucina-7/biossíntese , Subpopulações de Linfócitos T/imunologia , Animais , Biomarcadores/análise , Linfócitos T CD8-Positivos/citologia , Linfócitos T CD8-Positivos/metabolismo , Linfócitos T CD8-Positivos/transplante , Citotoxicidade Imunológica , Antígenos de Histocompatibilidade Classe II/genética , Antígenos de Histocompatibilidade Classe II/imunologia , Imunofenotipagem , Interferon gama/biossíntese , Interferon gama/imunologia , Listeriose/imunologia , Fígado/citologia , Pulmão/citologia , Linfonodos/citologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Receptores de Interleucina-7/análise , Receptores de Interleucina-7/química , Baço/citologia , Coloração e Rotulagem/métodos , Subpopulações de Linfócitos T/citologiaRESUMO
Adaptive immune responses in which CD8(+) T cells recognize pathogen-derived peptides in the context of major histocompatibility complex class I molecules play a major role in the host defense against infection with intracellular pathogens. Cells infected with intracellular bacteria such as Listeria monocytogenes, Salmonella enterica serovar Typhimurium, or Mycobacterium tuberculosis are directly lysed by cytotoxic CD8(+) T cells. For this reason, current vaccines for intracellular pathogens, such as subunit vaccines or viable bacterial vaccines, aim to generate robust cytotoxic T-cell responses. In order to investigate the capacity of a herpes simplex virus type 1 (HSV-1) vector to induce strong cytotoxic effector cell responses and protection from infection with intracellular pathogens, we developed a replication-deficient, recombinant HSV-1 (rHSV-1) vaccine. We demonstrate in side-by-side comparison with DNA vaccination that rHSV-1 vaccination induces very strong CD8(+) effector T-cell responses. While both vaccines provided protection from infection with L. monocytogenes at low, but lethal doses, only rHSV-1 vaccines could protect from higher infectious doses; HSV-1 induced potent memory cytotoxic T lymphocytes that, upon challenge by pathogens, efficiently protected the animals. Despite the stimulation of relatively low humoral and CD4-T-cell responses, rHSV-1 vectors are strong candidates for future vaccine strategies that confer efficient protection from subsequent infection with intracellular bacteria.
Assuntos
Infecções Bacterianas/prevenção & controle , Herpesvirus Humano 1/imunologia , Vacinas Virais/farmacologia , Animais , Infecções Bacterianas/imunologia , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD8-Positivos/imunologia , Herpesvirus Humano 1/genética , Herpesvirus Humano 1/fisiologia , Listeriose/imunologia , Listeriose/prevenção & controle , Camundongos , Camundongos Transgênicos , Mutação , Linfócitos T Citotóxicos/imunologia , Vacinas Sintéticas/farmacologia , Replicação Viral/genéticaRESUMO
Murine infection with the Gram-positive intracellular bacterium Listeria monocytogenes activates CD8(+) T cells that recognize bacterially derived N-formyl methionine peptides in the context of H2-M3 MHC class Ib molecules. Three peptides, fMIGWII, fMIVIL, and fMIVTLF, are targets of L. monocytogenes-specific CD8(+) T cells. To investigate epitope cross-recognition by H2-M3-restricted CD8(+) T cells, we deleted the sequence encoding fMIGWII from a virulent strain of L. monocytogenes. Infection with fMIGWII-deficient L. monocytogenes unexpectedly primed CD8(+) T cells that stain with fMIGWII/H2-M3 tetramers and lyse fMIGWII-coated target cells in vivo. Because the fMIGWII sequence is nonredundant, we speculated that other bacterially derived Ags are priming these responses. HPLC peptide fractionation of bacterial culture supernatants revealed several distinct L. monocytogenes-derived peptides that are recognized by fMIGWII-specific T cells. Our results demonstrate that the dominant H2-M3-restricted CD8(+) T cell population, although reactive with fMIGWII, is primed by other, non-fMIGWII peptides derived from L. monocytogenes. Although this degree of Ag receptor promiscuity is unusual for the adaptive immune system, it may be a more common feature of T cell responses restricted by nonpolymorphic MHC class Ib molecules.