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CpG-matured murine plasmacytoid dendritic cells are capable of in vivo priming of functional CD8 T cell responses to endogenous but not exogenous antigens.

Salio M, Palmowski MJ, Atzberger A, Hermans IF, Cerundolo V - J. Exp. Med. (2004)

Bottom Line: In vitro experiments have shown that upon maturation, human and murine PDCs develop into potent immunostimulatory cells; however, their ability to prime an immune response in vivo remains to be addressed.In contrast, immature PDCs are unable to prime antigen-specific CTLs.Our results underline the heterogeneity and plasticity of different antigen-presenting cells, and reveal an important role of mature PDCs in priming CD8 responses to endogenous antigens, in addition to their previously reported ability to modulate antiviral responses via type I IFN.

View Article: PubMed Central - PubMed

Affiliation: Cancer Research Tumor Immunology Unit, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Headley Way, OX3 9DS Oxford, UK. mariolina.salio@imm.ox.ac.uk

ABSTRACT
Plasmacytoid dendritic cells (PDCs) are a unique leukocyte population capable of secreting high levels of type I interferon (IFN) in response to viruses and bacterial stimuli. In vitro experiments have shown that upon maturation, human and murine PDCs develop into potent immunostimulatory cells; however, their ability to prime an immune response in vivo remains to be addressed. We report that CpG-matured murine PDCs are capable of eliciting in naive mice antigen-specific CTLs against endogenous antigens as well as exogenous peptides, but not against an exogenous antigen. Type I IFN is not required for priming, as injection of CpG-matured PDCs into type I IFN receptor-deficient mice elicits functional CTL responses. Mature PDCs prime CTLs that secrete IFN-gamma and protect mice from a tumor challenge. In contrast, immature PDCs are unable to prime antigen-specific CTLs. However, mice injected with immature PDCs are fully responsive to secondary antigenic challenges, suggesting that PDCs have not induced long-lasting tolerance via anergic or regulatory T cells. Our results underline the heterogeneity and plasticity of different antigen-presenting cells, and reveal an important role of mature PDCs in priming CD8 responses to endogenous antigens, in addition to their previously reported ability to modulate antiviral responses via type I IFN.

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Intravenous injection of CpG-matured male splenic PDCs induces CTL responses. C57BL/6 mice (n = 3) were injected i.v. with 0.5 × 105 male splenic MDC or PDCs (isolated from CpG-treated animals) and boosted after 1 wk with UV-inactivated vaccinia-UTY246–254 minigene. (A) CTL responses were assessed in the blood by ex vivo FACS® analysis using UTY246–254-H-2-Db tetramers 8 d after boosting. Mean proportions of tetramer+ cells as a percentage of CD8 cells (± SEM) for each group are shown. (B) IFN-γ ELISPOT was performed on splenocytes to assess responsiveness to 10 μg/ml UTY246–254 peptide 9 d after boosting. All animals showed comparable responses to PHA stimulation (not depicted).
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fig5: Intravenous injection of CpG-matured male splenic PDCs induces CTL responses. C57BL/6 mice (n = 3) were injected i.v. with 0.5 × 105 male splenic MDC or PDCs (isolated from CpG-treated animals) and boosted after 1 wk with UV-inactivated vaccinia-UTY246–254 minigene. (A) CTL responses were assessed in the blood by ex vivo FACS® analysis using UTY246–254-H-2-Db tetramers 8 d after boosting. Mean proportions of tetramer+ cells as a percentage of CD8 cells (± SEM) for each group are shown. (B) IFN-γ ELISPOT was performed on splenocytes to assess responsiveness to 10 μg/ml UTY246–254 peptide 9 d after boosting. All animals showed comparable responses to PHA stimulation (not depicted).

Mentions: It has been shown previously that freshly isolated splenic PDCs are less mature than their bone marrow–derived counterparts, hence they are also less immunostimulatory (15). Preliminary experiments showed that injection of immature splenic MDCs, in contrast to bone marrow–derived MDCs, did not elicit UTY246–254-specific CTLs detectable by ex vivo tetramer staining (unpublished data). Therefore, we isolated splenic PDCs and MDCs from male mice previously injected with CpG to induce in vivo DC maturation. Both MDCs and PDCs elicited UTY246–254-specific CTLs, although responses were much weaker than those elicited by equal numbers of bone marrow–derived DCs and were detectable only upon in vivo restimulation with vaccinia virus encoding the UTY246–254 minigene (Fig. 5 A). UTY246–254-specific CTLs primed by mature splenic PDCs and MDCs were functional, as shown by IFN-γ secretion in response to the cognate peptide in an ex vivo ELISPOT assay (Fig. 5 B).


CpG-matured murine plasmacytoid dendritic cells are capable of in vivo priming of functional CD8 T cell responses to endogenous but not exogenous antigens.

Salio M, Palmowski MJ, Atzberger A, Hermans IF, Cerundolo V - J. Exp. Med. (2004)

Intravenous injection of CpG-matured male splenic PDCs induces CTL responses. C57BL/6 mice (n = 3) were injected i.v. with 0.5 × 105 male splenic MDC or PDCs (isolated from CpG-treated animals) and boosted after 1 wk with UV-inactivated vaccinia-UTY246–254 minigene. (A) CTL responses were assessed in the blood by ex vivo FACS® analysis using UTY246–254-H-2-Db tetramers 8 d after boosting. Mean proportions of tetramer+ cells as a percentage of CD8 cells (± SEM) for each group are shown. (B) IFN-γ ELISPOT was performed on splenocytes to assess responsiveness to 10 μg/ml UTY246–254 peptide 9 d after boosting. All animals showed comparable responses to PHA stimulation (not depicted).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2211835&req=5

fig5: Intravenous injection of CpG-matured male splenic PDCs induces CTL responses. C57BL/6 mice (n = 3) were injected i.v. with 0.5 × 105 male splenic MDC or PDCs (isolated from CpG-treated animals) and boosted after 1 wk with UV-inactivated vaccinia-UTY246–254 minigene. (A) CTL responses were assessed in the blood by ex vivo FACS® analysis using UTY246–254-H-2-Db tetramers 8 d after boosting. Mean proportions of tetramer+ cells as a percentage of CD8 cells (± SEM) for each group are shown. (B) IFN-γ ELISPOT was performed on splenocytes to assess responsiveness to 10 μg/ml UTY246–254 peptide 9 d after boosting. All animals showed comparable responses to PHA stimulation (not depicted).
Mentions: It has been shown previously that freshly isolated splenic PDCs are less mature than their bone marrow–derived counterparts, hence they are also less immunostimulatory (15). Preliminary experiments showed that injection of immature splenic MDCs, in contrast to bone marrow–derived MDCs, did not elicit UTY246–254-specific CTLs detectable by ex vivo tetramer staining (unpublished data). Therefore, we isolated splenic PDCs and MDCs from male mice previously injected with CpG to induce in vivo DC maturation. Both MDCs and PDCs elicited UTY246–254-specific CTLs, although responses were much weaker than those elicited by equal numbers of bone marrow–derived DCs and were detectable only upon in vivo restimulation with vaccinia virus encoding the UTY246–254 minigene (Fig. 5 A). UTY246–254-specific CTLs primed by mature splenic PDCs and MDCs were functional, as shown by IFN-γ secretion in response to the cognate peptide in an ex vivo ELISPOT assay (Fig. 5 B).

Bottom Line: In vitro experiments have shown that upon maturation, human and murine PDCs develop into potent immunostimulatory cells; however, their ability to prime an immune response in vivo remains to be addressed.In contrast, immature PDCs are unable to prime antigen-specific CTLs.Our results underline the heterogeneity and plasticity of different antigen-presenting cells, and reveal an important role of mature PDCs in priming CD8 responses to endogenous antigens, in addition to their previously reported ability to modulate antiviral responses via type I IFN.

View Article: PubMed Central - PubMed

Affiliation: Cancer Research Tumor Immunology Unit, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Headley Way, OX3 9DS Oxford, UK. mariolina.salio@imm.ox.ac.uk

ABSTRACT
Plasmacytoid dendritic cells (PDCs) are a unique leukocyte population capable of secreting high levels of type I interferon (IFN) in response to viruses and bacterial stimuli. In vitro experiments have shown that upon maturation, human and murine PDCs develop into potent immunostimulatory cells; however, their ability to prime an immune response in vivo remains to be addressed. We report that CpG-matured murine PDCs are capable of eliciting in naive mice antigen-specific CTLs against endogenous antigens as well as exogenous peptides, but not against an exogenous antigen. Type I IFN is not required for priming, as injection of CpG-matured PDCs into type I IFN receptor-deficient mice elicits functional CTL responses. Mature PDCs prime CTLs that secrete IFN-gamma and protect mice from a tumor challenge. In contrast, immature PDCs are unable to prime antigen-specific CTLs. However, mice injected with immature PDCs are fully responsive to secondary antigenic challenges, suggesting that PDCs have not induced long-lasting tolerance via anergic or regulatory T cells. Our results underline the heterogeneity and plasticity of different antigen-presenting cells, and reveal an important role of mature PDCs in priming CD8 responses to endogenous antigens, in addition to their previously reported ability to modulate antiviral responses via type I IFN.

Show MeSH
Related in: MedlinePlus