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Migratory dermal dendritic cells act as rapid sensors of protozoan parasites.

Ng LG, Hsu A, Mandell MA, Roediger B, Hoeller C, Mrass P, Iparraguirre A, Cavanagh LL, Triccas JA, Beverley SM, Scott P, Weninger W - PLoS Pathog. (2008)

Bottom Line: Surprisingly, we found that, under homeostatic conditions, DDC were highly motile, continuously crawling through the interstitial space in a Galpha(i) protein-coupled receptor-dependent manner.Together, our study has visualized the dynamics and microenvironmental context of parasite encounter by an innate immune cell subset during the initiation of the immune response.Our results uncover a unique migratory tissue surveillance program of DDC that ensures the rapid detection of pathogens.

View Article: PubMed Central - PubMed

Affiliation: The Wistar Institute, Philadelphia, Pennsylvania, USA.

ABSTRACT
Dendritic cells (DC), including those of the skin, act as sentinels for intruding microorganisms. In the epidermis, DC (termed Langerhans cells, LC) are sessile and screen their microenvironment through occasional movements of their dendrites. The spatio-temporal orchestration of antigen encounter by dermal DC (DDC) is not known. Since these cells are thought to be instrumental in the initiation of immune responses during infection, we investigated their behavior directly within their natural microenvironment using intravital two-photon microscopy. Surprisingly, we found that, under homeostatic conditions, DDC were highly motile, continuously crawling through the interstitial space in a Galpha(i) protein-coupled receptor-dependent manner. However, within minutes after intradermal delivery of the protozoan parasite Leishmania major, DDC became immobile and incorporated multiple parasites into cytosolic vacuoles. Parasite uptake occurred through the extension of long, highly dynamic pseudopods capable of tracking and engulfing parasites. This was then followed by rapid dendrite retraction towards the cell body. DDC were proficient at discriminating between parasites and inert particles, and parasite uptake was independent of the presence of neutrophils. Together, our study has visualized the dynamics and microenvironmental context of parasite encounter by an innate immune cell subset during the initiation of the immune response. Our results uncover a unique migratory tissue surveillance program of DDC that ensures the rapid detection of pathogens.

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Phenotypic characterization of CD11c-YFP+ cells in ear skin.Flow cytometric analyses of surface markers expressed by epidermal and dermal cells from CD11c-YFP mice. The histogram plots were pre-gated on forward (FSC) and side-scatter (SSC) profiles. SSC/CD45 and FSC/YFP plots are shown for clear distinction of individual cell populations. Representative plots from 3 to 4 animals are shown.
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ppat-1000222-g001: Phenotypic characterization of CD11c-YFP+ cells in ear skin.Flow cytometric analyses of surface markers expressed by epidermal and dermal cells from CD11c-YFP mice. The histogram plots were pre-gated on forward (FSC) and side-scatter (SSC) profiles. SSC/CD45 and FSC/YFP plots are shown for clear distinction of individual cell populations. Representative plots from 3 to 4 animals are shown.

Mentions: In order to visualize the behavior of LC and DDC, we made use of CD11c-YFP mice [19], in which DC express high levels of cytoplasmic YFP. To ascertain that skin DC expressed YFP, we analyzed single cell suspensions prepared from separated epidermis and dermis by flow cytometry (Figure 1). CD45+YFP+ epidermal cells were CD11c+CD11b+F4/80+I-Ab+ (Figure 1), and immunofluorescence staining of tissue sections showed that langerin expressing YFP+ cells displayed the characteristic morphology of LC (data not shown). In the dermis, CD45+YFP+ cells were CD11c+CD11b+F4/80+I-Ab-high, and therefore represented DDC [20]. We also detected a subset of CD45+YFPlow cells within the dermis. However, this signal was due to autofluorescence, rather than specific YFP expression, as a similar population of cells was also found in wildtype animals (Figure S1A). These cells were CD11c−CD11b+F4/80+Moma-2+I-Ab-low thereby resembling dermal macrophages [20]. The fluorescence intensity of these cells was, on average, 50 times dimmer than the YFP signal from DDC. Since, under our 2P imaging conditions, we did not detect any signal in the dermis of wildtype animals (Figure S1B), we concluded that LC and DDC in CD11c-YFP mice can be detected by means of specific YFP expression, while other hematopoietic cell subsets remain undetectable.


Migratory dermal dendritic cells act as rapid sensors of protozoan parasites.

Ng LG, Hsu A, Mandell MA, Roediger B, Hoeller C, Mrass P, Iparraguirre A, Cavanagh LL, Triccas JA, Beverley SM, Scott P, Weninger W - PLoS Pathog. (2008)

Phenotypic characterization of CD11c-YFP+ cells in ear skin.Flow cytometric analyses of surface markers expressed by epidermal and dermal cells from CD11c-YFP mice. The histogram plots were pre-gated on forward (FSC) and side-scatter (SSC) profiles. SSC/CD45 and FSC/YFP plots are shown for clear distinction of individual cell populations. Representative plots from 3 to 4 animals are shown.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2583051&req=5

ppat-1000222-g001: Phenotypic characterization of CD11c-YFP+ cells in ear skin.Flow cytometric analyses of surface markers expressed by epidermal and dermal cells from CD11c-YFP mice. The histogram plots were pre-gated on forward (FSC) and side-scatter (SSC) profiles. SSC/CD45 and FSC/YFP plots are shown for clear distinction of individual cell populations. Representative plots from 3 to 4 animals are shown.
Mentions: In order to visualize the behavior of LC and DDC, we made use of CD11c-YFP mice [19], in which DC express high levels of cytoplasmic YFP. To ascertain that skin DC expressed YFP, we analyzed single cell suspensions prepared from separated epidermis and dermis by flow cytometry (Figure 1). CD45+YFP+ epidermal cells were CD11c+CD11b+F4/80+I-Ab+ (Figure 1), and immunofluorescence staining of tissue sections showed that langerin expressing YFP+ cells displayed the characteristic morphology of LC (data not shown). In the dermis, CD45+YFP+ cells were CD11c+CD11b+F4/80+I-Ab-high, and therefore represented DDC [20]. We also detected a subset of CD45+YFPlow cells within the dermis. However, this signal was due to autofluorescence, rather than specific YFP expression, as a similar population of cells was also found in wildtype animals (Figure S1A). These cells were CD11c−CD11b+F4/80+Moma-2+I-Ab-low thereby resembling dermal macrophages [20]. The fluorescence intensity of these cells was, on average, 50 times dimmer than the YFP signal from DDC. Since, under our 2P imaging conditions, we did not detect any signal in the dermis of wildtype animals (Figure S1B), we concluded that LC and DDC in CD11c-YFP mice can be detected by means of specific YFP expression, while other hematopoietic cell subsets remain undetectable.

Bottom Line: Surprisingly, we found that, under homeostatic conditions, DDC were highly motile, continuously crawling through the interstitial space in a Galpha(i) protein-coupled receptor-dependent manner.Together, our study has visualized the dynamics and microenvironmental context of parasite encounter by an innate immune cell subset during the initiation of the immune response.Our results uncover a unique migratory tissue surveillance program of DDC that ensures the rapid detection of pathogens.

View Article: PubMed Central - PubMed

Affiliation: The Wistar Institute, Philadelphia, Pennsylvania, USA.

ABSTRACT
Dendritic cells (DC), including those of the skin, act as sentinels for intruding microorganisms. In the epidermis, DC (termed Langerhans cells, LC) are sessile and screen their microenvironment through occasional movements of their dendrites. The spatio-temporal orchestration of antigen encounter by dermal DC (DDC) is not known. Since these cells are thought to be instrumental in the initiation of immune responses during infection, we investigated their behavior directly within their natural microenvironment using intravital two-photon microscopy. Surprisingly, we found that, under homeostatic conditions, DDC were highly motile, continuously crawling through the interstitial space in a Galpha(i) protein-coupled receptor-dependent manner. However, within minutes after intradermal delivery of the protozoan parasite Leishmania major, DDC became immobile and incorporated multiple parasites into cytosolic vacuoles. Parasite uptake occurred through the extension of long, highly dynamic pseudopods capable of tracking and engulfing parasites. This was then followed by rapid dendrite retraction towards the cell body. DDC were proficient at discriminating between parasites and inert particles, and parasite uptake was independent of the presence of neutrophils. Together, our study has visualized the dynamics and microenvironmental context of parasite encounter by an innate immune cell subset during the initiation of the immune response. Our results uncover a unique migratory tissue surveillance program of DDC that ensures the rapid detection of pathogens.

Show MeSH
Related in: MedlinePlus