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Depletion of dendritic cells enhances innate anti-bacterial host defense through modulation of phagocyte homeostasis.

Autenrieth SE, Warnke P, Wabnitz GH, Lucero Estrada C, Pasquevich KA, Drechsler D, Günter M, Hochweller K, Novakovic A, Beer-Hammer S, Samstag Y, Hämmerling GJ, Garbi N, Autenrieth IB - PLoS Pathog. (2012)

Bottom Line: DC depletion was accompanied by an increase in the serum levels of CXCL1, G-CSF, IL-1α, and CCL2 and an increase in the numbers of splenic phagocytes.Cellular studies further showed that this was due to an increased production of reactive oxygen species (ROS) by neutrophils.In summary, we could show that DC depletion triggers phagocyte accumulation in the spleen and enhances their anti-bacterial killing capacity upon bacterial infection.

View Article: PubMed Central - PubMed

Affiliation: Interfakultäres Institut für Mikrobiologie und Infektionsmedizin, Universität Tübingen, Tübingen, Germany. Stella.Autenrieth@medizin.uni-tuebingen.de

ABSTRACT
Dendritic cells (DCs) as professional antigen-presenting cells play an important role in the initiation and modulation of the adaptive immune response. However, their role in the innate immune response against bacterial infections is not completely defined. Here we have analyzed the role of DCs and their impact on the innate anti-bacterial host defense in an experimental infection model of Yersinia enterocolitica (Ye). We used CD11c-diphtheria toxin (DT) mice to deplete DCs prior to severe infection with Ye. DC depletion significantly increased animal survival after Ye infection. The bacterial load in the spleen of DC-depleted mice was significantly lower than that of control mice throughout the infection. DC depletion was accompanied by an increase in the serum levels of CXCL1, G-CSF, IL-1α, and CCL2 and an increase in the numbers of splenic phagocytes. Functionally, splenocytes from DC-depleted mice exhibited an increased bacterial killing capacity compared to splenocytes from control mice. Cellular studies further showed that this was due to an increased production of reactive oxygen species (ROS) by neutrophils. Adoptive transfer of neutrophils from DC-depleted mice into control mice prior to Ye infection reduced the bacterial load to the level of Ye-infected DC-depleted mice, suggesting that the increased number of phagocytes with additional ROS production account for the decreased bacterial load. Furthermore, after incubation with serum from DC-depleted mice splenocytes from control mice increased their bacterial killing capacity, most likely due to enhanced ROS production by neutrophils, indicating that serum factors from DC-depleted mice account for this effect. In summary, we could show that DC depletion triggers phagocyte accumulation in the spleen and enhances their anti-bacterial killing capacity upon bacterial infection.

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Replacement of DCs by monocytes and neutrophils upon DC depletion.(A–D) Mice were treated daily with diphtheria toxin (DT) (A and B) starting one day before infection and were injected with 5×104 Ye pYV+ for 24 h (C and D). (A) Representative dot plots showing analysis of monocytes (left) and neutrophils (right) in spleen from control (black) and DC-depleted (red) mice. Numbers adjacent to outlined areas indicate frequency of monocytes and neutrophils. Graphs show the frequency of monocytes (left) and neutrophils (right) per spleen. (B) Bioplex assay or ELISA of chemokine concentrations in sera from control and DC-depleted mice 24 h after DT-treatment. (C) Flow cytometry analysis of the frequency of monocytes (left) and neutrophils (right) in the spleen at the indicated times post Ye infection. (D) Bioplex assay or ELISA of chemokine and cytokine concentrations in sera from control and DC-depleted mice 24 h after Ye infection. Each symbol represents an individual mouse; small horizontal lines indicate the mean ± SD. * indicates statistically significant differences between control and DC-depleted mice (Student's t-test). Data are from 5 (A) or one representative out of 2 or more (B, C and D) independent experiments.
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ppat-1002552-g002: Replacement of DCs by monocytes and neutrophils upon DC depletion.(A–D) Mice were treated daily with diphtheria toxin (DT) (A and B) starting one day before infection and were injected with 5×104 Ye pYV+ for 24 h (C and D). (A) Representative dot plots showing analysis of monocytes (left) and neutrophils (right) in spleen from control (black) and DC-depleted (red) mice. Numbers adjacent to outlined areas indicate frequency of monocytes and neutrophils. Graphs show the frequency of monocytes (left) and neutrophils (right) per spleen. (B) Bioplex assay or ELISA of chemokine concentrations in sera from control and DC-depleted mice 24 h after DT-treatment. (C) Flow cytometry analysis of the frequency of monocytes (left) and neutrophils (right) in the spleen at the indicated times post Ye infection. (D) Bioplex assay or ELISA of chemokine and cytokine concentrations in sera from control and DC-depleted mice 24 h after Ye infection. Each symbol represents an individual mouse; small horizontal lines indicate the mean ± SD. * indicates statistically significant differences between control and DC-depleted mice (Student's t-test). Data are from 5 (A) or one representative out of 2 or more (B, C and D) independent experiments.

Mentions: As DC-depleted mice displayed a significantly lower bacterial load in the spleen, already 1 dpi compared to control mice (Figure 1B) we hypothesized that this could reflect an altered splenocyte composition following DC depletion prior to infection. In fact, single DT treatment of uninfected mice led to a 3 to 4-fold increase in the frequency of inflammatory monocytes (Gr-1+Ly6G−Ly6ChiCD11b+) and neutrophils (Gr-1hiLy6G+Ly6C−/intCD11bhi, see Figure S2 for detailed gating strategy) after 24 h in the spleen of DC-depleted mice compared to DT-treated control mice (Figure 2A and [25]). Similarly, increased numbers of neutrophils and monocytes were observed in peripheral blood (data not shown). However, we did not observe differences in the frequency of B cells, T cells or NK cells (data not shown and [25]).


Depletion of dendritic cells enhances innate anti-bacterial host defense through modulation of phagocyte homeostasis.

Autenrieth SE, Warnke P, Wabnitz GH, Lucero Estrada C, Pasquevich KA, Drechsler D, Günter M, Hochweller K, Novakovic A, Beer-Hammer S, Samstag Y, Hämmerling GJ, Garbi N, Autenrieth IB - PLoS Pathog. (2012)

Replacement of DCs by monocytes and neutrophils upon DC depletion.(A–D) Mice were treated daily with diphtheria toxin (DT) (A and B) starting one day before infection and were injected with 5×104 Ye pYV+ for 24 h (C and D). (A) Representative dot plots showing analysis of monocytes (left) and neutrophils (right) in spleen from control (black) and DC-depleted (red) mice. Numbers adjacent to outlined areas indicate frequency of monocytes and neutrophils. Graphs show the frequency of monocytes (left) and neutrophils (right) per spleen. (B) Bioplex assay or ELISA of chemokine concentrations in sera from control and DC-depleted mice 24 h after DT-treatment. (C) Flow cytometry analysis of the frequency of monocytes (left) and neutrophils (right) in the spleen at the indicated times post Ye infection. (D) Bioplex assay or ELISA of chemokine and cytokine concentrations in sera from control and DC-depleted mice 24 h after Ye infection. Each symbol represents an individual mouse; small horizontal lines indicate the mean ± SD. * indicates statistically significant differences between control and DC-depleted mice (Student's t-test). Data are from 5 (A) or one representative out of 2 or more (B, C and D) independent experiments.
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Related In: Results  -  Collection

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ppat-1002552-g002: Replacement of DCs by monocytes and neutrophils upon DC depletion.(A–D) Mice were treated daily with diphtheria toxin (DT) (A and B) starting one day before infection and were injected with 5×104 Ye pYV+ for 24 h (C and D). (A) Representative dot plots showing analysis of monocytes (left) and neutrophils (right) in spleen from control (black) and DC-depleted (red) mice. Numbers adjacent to outlined areas indicate frequency of monocytes and neutrophils. Graphs show the frequency of monocytes (left) and neutrophils (right) per spleen. (B) Bioplex assay or ELISA of chemokine concentrations in sera from control and DC-depleted mice 24 h after DT-treatment. (C) Flow cytometry analysis of the frequency of monocytes (left) and neutrophils (right) in the spleen at the indicated times post Ye infection. (D) Bioplex assay or ELISA of chemokine and cytokine concentrations in sera from control and DC-depleted mice 24 h after Ye infection. Each symbol represents an individual mouse; small horizontal lines indicate the mean ± SD. * indicates statistically significant differences between control and DC-depleted mice (Student's t-test). Data are from 5 (A) or one representative out of 2 or more (B, C and D) independent experiments.
Mentions: As DC-depleted mice displayed a significantly lower bacterial load in the spleen, already 1 dpi compared to control mice (Figure 1B) we hypothesized that this could reflect an altered splenocyte composition following DC depletion prior to infection. In fact, single DT treatment of uninfected mice led to a 3 to 4-fold increase in the frequency of inflammatory monocytes (Gr-1+Ly6G−Ly6ChiCD11b+) and neutrophils (Gr-1hiLy6G+Ly6C−/intCD11bhi, see Figure S2 for detailed gating strategy) after 24 h in the spleen of DC-depleted mice compared to DT-treated control mice (Figure 2A and [25]). Similarly, increased numbers of neutrophils and monocytes were observed in peripheral blood (data not shown). However, we did not observe differences in the frequency of B cells, T cells or NK cells (data not shown and [25]).

Bottom Line: DC depletion was accompanied by an increase in the serum levels of CXCL1, G-CSF, IL-1α, and CCL2 and an increase in the numbers of splenic phagocytes.Cellular studies further showed that this was due to an increased production of reactive oxygen species (ROS) by neutrophils.In summary, we could show that DC depletion triggers phagocyte accumulation in the spleen and enhances their anti-bacterial killing capacity upon bacterial infection.

View Article: PubMed Central - PubMed

Affiliation: Interfakultäres Institut für Mikrobiologie und Infektionsmedizin, Universität Tübingen, Tübingen, Germany. Stella.Autenrieth@medizin.uni-tuebingen.de

ABSTRACT
Dendritic cells (DCs) as professional antigen-presenting cells play an important role in the initiation and modulation of the adaptive immune response. However, their role in the innate immune response against bacterial infections is not completely defined. Here we have analyzed the role of DCs and their impact on the innate anti-bacterial host defense in an experimental infection model of Yersinia enterocolitica (Ye). We used CD11c-diphtheria toxin (DT) mice to deplete DCs prior to severe infection with Ye. DC depletion significantly increased animal survival after Ye infection. The bacterial load in the spleen of DC-depleted mice was significantly lower than that of control mice throughout the infection. DC depletion was accompanied by an increase in the serum levels of CXCL1, G-CSF, IL-1α, and CCL2 and an increase in the numbers of splenic phagocytes. Functionally, splenocytes from DC-depleted mice exhibited an increased bacterial killing capacity compared to splenocytes from control mice. Cellular studies further showed that this was due to an increased production of reactive oxygen species (ROS) by neutrophils. Adoptive transfer of neutrophils from DC-depleted mice into control mice prior to Ye infection reduced the bacterial load to the level of Ye-infected DC-depleted mice, suggesting that the increased number of phagocytes with additional ROS production account for the decreased bacterial load. Furthermore, after incubation with serum from DC-depleted mice splenocytes from control mice increased their bacterial killing capacity, most likely due to enhanced ROS production by neutrophils, indicating that serum factors from DC-depleted mice account for this effect. In summary, we could show that DC depletion triggers phagocyte accumulation in the spleen and enhances their anti-bacterial killing capacity upon bacterial infection.

Show MeSH
Related in: MedlinePlus