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Dendritic Cell-Mediated Phagocytosis but Not Immune Activation Is Enhanced by Plasmin.

Borg RJ, Samson AL, Au AE, Scholzen A, Fuchsberger M, Kong YY, Freeman R, Mifsud NA, Plebanski M, Medcalf RL - PLoS ONE (2015)

Bottom Line: Plasmin also promoted phagocytosis of protease-resistant microparticles by diverse mouse dendritic cell sub-types both in vitro and in vivo.Together with an increased phagocytic capacity, plasmin-treated dendritic cells maintain an immature phenotype, exhibit reduced migration to lymph nodes, increase their expression/release of the immunosuppressive cytokine TGF-β, and lose their capacity to mount an allogeneic response.Collectively, our findings support a novel role for plasmin formed on dead cells and other phagocytic targets in maintaining tissue homeostasis by increasing the phagocytic function of dendritic cells while simultaneously decreasing their immunostimulatory capacity consistent with producing an immunosuppressive state.

View Article: PubMed Central - PubMed

Affiliation: Australian Centre for Blood Diseases, Monash University, Alfred Medical Research and Education Precinct, Melbourne, 3004, Victoria Australia.

ABSTRACT
Removal of dead cells in the absence of concomitant immune stimulation is essential for tissue homeostasis. We recently identified an injury-induced protein misfolding event that orchestrates the plasmin-dependent proteolytic degradation of necrotic cells. As impaired clearance of dead cells by the innate immune system predisposes to autoimmunity, we determined whether plasmin could influence endocytosis and immune cell stimulation by dendritic cells - a critical cell that links the innate and adaptive immune systems. We find that plasmin generated on the surface of necrotic cells enhances their phagocytic removal by human monocyte-derived dendritic cells. Plasmin also promoted phagocytosis of protease-resistant microparticles by diverse mouse dendritic cell sub-types both in vitro and in vivo. Together with an increased phagocytic capacity, plasmin-treated dendritic cells maintain an immature phenotype, exhibit reduced migration to lymph nodes, increase their expression/release of the immunosuppressive cytokine TGF-β, and lose their capacity to mount an allogeneic response. Collectively, our findings support a novel role for plasmin formed on dead cells and other phagocytic targets in maintaining tissue homeostasis by increasing the phagocytic function of dendritic cells while simultaneously decreasing their immunostimulatory capacity consistent with producing an immunosuppressive state.

No MeSH data available.


Related in: MedlinePlus

Intradermal plasmin injection increases the phagocytosis of microparticles by multiple mouse dendritic cell types in vivo, but does not trigger their maturation or migration to the draining lymph nodes.Mice were intradermally injected with microparticles in the presence/absence of 0.02 pmol of t-PA, 0.1 pmol of plasminogen or 10 μg of LPS. 24 h after injection, the draining inguinal lymph nodes were harvested and single cell suspensions were stained for cell-surface markers (CD11c, CD11b, MHC class II, CD86 and B220) and subjected to flow cytometry. Events were gated into three populations: CD11cpositive MHC class IIpositive conventional dendritic cells (left column), CD11bpositive B220positive plasmacytoid dendritic cells (middle column) and CD11cpositive MHC class IIpositive CD11bpositive CD207positive CD103negative Langerhans cells (right column, note that CD86 analysis was not included for Langerhans cells). Within each dendritic cell population the percentage of cells with internalized particles (top row), their maturation status as determined by relative mean fluorescence intensity of CD86-staining (middle row), and their number relative to all cells within the draining lymph nodes (LN; bottom row) were determined. Data are shown as mean ± s.e.m. (n = 8–11 independent experiments). *p<0.05, **p<0.01, **p<0.001 and ***p<0.0001 by 1-way ANOVA with Newman-Keuls post-hoc analysis. Two outliers were identified by Grubb’s test and excluded from the analysis.
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pone.0131216.g006: Intradermal plasmin injection increases the phagocytosis of microparticles by multiple mouse dendritic cell types in vivo, but does not trigger their maturation or migration to the draining lymph nodes.Mice were intradermally injected with microparticles in the presence/absence of 0.02 pmol of t-PA, 0.1 pmol of plasminogen or 10 μg of LPS. 24 h after injection, the draining inguinal lymph nodes were harvested and single cell suspensions were stained for cell-surface markers (CD11c, CD11b, MHC class II, CD86 and B220) and subjected to flow cytometry. Events were gated into three populations: CD11cpositive MHC class IIpositive conventional dendritic cells (left column), CD11bpositive B220positive plasmacytoid dendritic cells (middle column) and CD11cpositive MHC class IIpositive CD11bpositive CD207positive CD103negative Langerhans cells (right column, note that CD86 analysis was not included for Langerhans cells). Within each dendritic cell population the percentage of cells with internalized particles (top row), their maturation status as determined by relative mean fluorescence intensity of CD86-staining (middle row), and their number relative to all cells within the draining lymph nodes (LN; bottom row) were determined. Data are shown as mean ± s.e.m. (n = 8–11 independent experiments). *p<0.05, **p<0.01, **p<0.001 and ***p<0.0001 by 1-way ANOVA with Newman-Keuls post-hoc analysis. Two outliers were identified by Grubb’s test and excluded from the analysis.

Mentions: To explore whether plasmin could similarly modulate dendritic cell function in vivo, fluorescent microparticles were injected intradermally into the base of the tail of wild-type mice in the presence or absence of t-PA and plasminogen (alone or in combination). In addition, mice were co-injected with LPS and microparticles to serve as a positive control for enhanced maturation and migration by dendritic cells. Cells within the draining lymph nodes were collected 24 h after injection, and three major dendritic cell types (conventional, plasmacytoid and Langerhans cells) were stained and assessed for microparticle uptake, maturation status and overall number. Consistent with our in vitro data, plasmin generation increased the in vivo phagocytic capacity of all three dendritic cell populations (Fig 6; top panels). Moreover, this increase in phagocytosis did not result in maturation, as determined by CD86 expression (Fig 6; middle panels). Plasmin generation also caused a significant reduction in the number of conventional dendritic cells (cDCs) entering the draining lymph nodes with similar albeit non-significant trends seen for plasmacytoid dendritic cells (pDCs) and Langerhans cells (Fig 6; bottom panels). The reason for a plasmin-mediated reduction in dendritic cell migration to the draining lymph nodes may relate to plasmin acting as a chemotaxic agent [26,30], whereby plasmin discourages the migration of dendritic cells away from the injection site. Injection of either t-PA or plasminogen alone failed to alter any of the measured dendritic cell parameters indicating that the observed effects require plasmin formation. As expected, and in contrast to the influence of plasmin, LPS injection caused maturation and reduced microparticle uptake in all dendritic cell subtypes. LPS also increased migration of conventional dendritic cells and Langerhans cells to the draining lymph nodes (Fig 6). These in vivo observations are consistent with the notion that plasmin modulates dendritic cells by increasing their phagocytic capacity in a manner that simultaneously avoids their maturation and migration to draining lymph nodes.


Dendritic Cell-Mediated Phagocytosis but Not Immune Activation Is Enhanced by Plasmin.

Borg RJ, Samson AL, Au AE, Scholzen A, Fuchsberger M, Kong YY, Freeman R, Mifsud NA, Plebanski M, Medcalf RL - PLoS ONE (2015)

Intradermal plasmin injection increases the phagocytosis of microparticles by multiple mouse dendritic cell types in vivo, but does not trigger their maturation or migration to the draining lymph nodes.Mice were intradermally injected with microparticles in the presence/absence of 0.02 pmol of t-PA, 0.1 pmol of plasminogen or 10 μg of LPS. 24 h after injection, the draining inguinal lymph nodes were harvested and single cell suspensions were stained for cell-surface markers (CD11c, CD11b, MHC class II, CD86 and B220) and subjected to flow cytometry. Events were gated into three populations: CD11cpositive MHC class IIpositive conventional dendritic cells (left column), CD11bpositive B220positive plasmacytoid dendritic cells (middle column) and CD11cpositive MHC class IIpositive CD11bpositive CD207positive CD103negative Langerhans cells (right column, note that CD86 analysis was not included for Langerhans cells). Within each dendritic cell population the percentage of cells with internalized particles (top row), their maturation status as determined by relative mean fluorescence intensity of CD86-staining (middle row), and their number relative to all cells within the draining lymph nodes (LN; bottom row) were determined. Data are shown as mean ± s.e.m. (n = 8–11 independent experiments). *p<0.05, **p<0.01, **p<0.001 and ***p<0.0001 by 1-way ANOVA with Newman-Keuls post-hoc analysis. Two outliers were identified by Grubb’s test and excluded from the analysis.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4488505&req=5

pone.0131216.g006: Intradermal plasmin injection increases the phagocytosis of microparticles by multiple mouse dendritic cell types in vivo, but does not trigger their maturation or migration to the draining lymph nodes.Mice were intradermally injected with microparticles in the presence/absence of 0.02 pmol of t-PA, 0.1 pmol of plasminogen or 10 μg of LPS. 24 h after injection, the draining inguinal lymph nodes were harvested and single cell suspensions were stained for cell-surface markers (CD11c, CD11b, MHC class II, CD86 and B220) and subjected to flow cytometry. Events were gated into three populations: CD11cpositive MHC class IIpositive conventional dendritic cells (left column), CD11bpositive B220positive plasmacytoid dendritic cells (middle column) and CD11cpositive MHC class IIpositive CD11bpositive CD207positive CD103negative Langerhans cells (right column, note that CD86 analysis was not included for Langerhans cells). Within each dendritic cell population the percentage of cells with internalized particles (top row), their maturation status as determined by relative mean fluorescence intensity of CD86-staining (middle row), and their number relative to all cells within the draining lymph nodes (LN; bottom row) were determined. Data are shown as mean ± s.e.m. (n = 8–11 independent experiments). *p<0.05, **p<0.01, **p<0.001 and ***p<0.0001 by 1-way ANOVA with Newman-Keuls post-hoc analysis. Two outliers were identified by Grubb’s test and excluded from the analysis.
Mentions: To explore whether plasmin could similarly modulate dendritic cell function in vivo, fluorescent microparticles were injected intradermally into the base of the tail of wild-type mice in the presence or absence of t-PA and plasminogen (alone or in combination). In addition, mice were co-injected with LPS and microparticles to serve as a positive control for enhanced maturation and migration by dendritic cells. Cells within the draining lymph nodes were collected 24 h after injection, and three major dendritic cell types (conventional, plasmacytoid and Langerhans cells) were stained and assessed for microparticle uptake, maturation status and overall number. Consistent with our in vitro data, plasmin generation increased the in vivo phagocytic capacity of all three dendritic cell populations (Fig 6; top panels). Moreover, this increase in phagocytosis did not result in maturation, as determined by CD86 expression (Fig 6; middle panels). Plasmin generation also caused a significant reduction in the number of conventional dendritic cells (cDCs) entering the draining lymph nodes with similar albeit non-significant trends seen for plasmacytoid dendritic cells (pDCs) and Langerhans cells (Fig 6; bottom panels). The reason for a plasmin-mediated reduction in dendritic cell migration to the draining lymph nodes may relate to plasmin acting as a chemotaxic agent [26,30], whereby plasmin discourages the migration of dendritic cells away from the injection site. Injection of either t-PA or plasminogen alone failed to alter any of the measured dendritic cell parameters indicating that the observed effects require plasmin formation. As expected, and in contrast to the influence of plasmin, LPS injection caused maturation and reduced microparticle uptake in all dendritic cell subtypes. LPS also increased migration of conventional dendritic cells and Langerhans cells to the draining lymph nodes (Fig 6). These in vivo observations are consistent with the notion that plasmin modulates dendritic cells by increasing their phagocytic capacity in a manner that simultaneously avoids their maturation and migration to draining lymph nodes.

Bottom Line: Plasmin also promoted phagocytosis of protease-resistant microparticles by diverse mouse dendritic cell sub-types both in vitro and in vivo.Together with an increased phagocytic capacity, plasmin-treated dendritic cells maintain an immature phenotype, exhibit reduced migration to lymph nodes, increase their expression/release of the immunosuppressive cytokine TGF-β, and lose their capacity to mount an allogeneic response.Collectively, our findings support a novel role for plasmin formed on dead cells and other phagocytic targets in maintaining tissue homeostasis by increasing the phagocytic function of dendritic cells while simultaneously decreasing their immunostimulatory capacity consistent with producing an immunosuppressive state.

View Article: PubMed Central - PubMed

Affiliation: Australian Centre for Blood Diseases, Monash University, Alfred Medical Research and Education Precinct, Melbourne, 3004, Victoria Australia.

ABSTRACT
Removal of dead cells in the absence of concomitant immune stimulation is essential for tissue homeostasis. We recently identified an injury-induced protein misfolding event that orchestrates the plasmin-dependent proteolytic degradation of necrotic cells. As impaired clearance of dead cells by the innate immune system predisposes to autoimmunity, we determined whether plasmin could influence endocytosis and immune cell stimulation by dendritic cells - a critical cell that links the innate and adaptive immune systems. We find that plasmin generated on the surface of necrotic cells enhances their phagocytic removal by human monocyte-derived dendritic cells. Plasmin also promoted phagocytosis of protease-resistant microparticles by diverse mouse dendritic cell sub-types both in vitro and in vivo. Together with an increased phagocytic capacity, plasmin-treated dendritic cells maintain an immature phenotype, exhibit reduced migration to lymph nodes, increase their expression/release of the immunosuppressive cytokine TGF-β, and lose their capacity to mount an allogeneic response. Collectively, our findings support a novel role for plasmin formed on dead cells and other phagocytic targets in maintaining tissue homeostasis by increasing the phagocytic function of dendritic cells while simultaneously decreasing their immunostimulatory capacity consistent with producing an immunosuppressive state.

No MeSH data available.


Related in: MedlinePlus