Identification of functionally-distinct macrophage subpopulations regulated by efferocytosis in Drosophila

AbstractMacrophages are a highly heterogeneous population of cells, with this diversity stemming in part from the existence of tissue resident populations and an ability to adopt a variety of activation states in response to stimuli. Drosophila blood cells (hemocytes) are dominated by a lineage of cells considered to be the functional equivalents of mammalian macrophages (plasmatocytes). Until very recently plasmatocytes were thought to be a homogeneous population. Here, we identify enhancer elements that label subpopulations of plasmatocytes, which vary in abundance across the lifecourse of the fly. We demonstrate that these plasmatocyte subpopulations behave in a functionally-distinct manner when compared to the overall population, including more potent migratory responses to injury and decreased clearance of apoptotic cells within the developing embryo. Additionally, these subpopulations display differential localisation and dynamics in pupae and adults, hinting at the presence of tissue-resident macrophages in the fly. Our enhancer analysis also allows us to identify novel candidate genes involved in plasmatocyte behaviour in vivo. Misexpression of one such enhancer-linked gene (calnexin14D) in all plasmatocytes improves wound responses, causing the overall population to behave more like the subpopulation marked by the calnexin14D-associated enhancer. Finally, we show that, we are able to modulate the number of cells within some subpopulations via exposure to increased levels of apoptotic cell death, thereby decreasing the number of plasmatocytes within more wound-responsive subpopulations. Taken together our data demonstrates the existence of macrophage heterogeneity in Drosophila and identifies mechanisms involved in the specification and function of these plasmatocyte subpopulations. Furthermore, this work identifies key molecular tools with which Drosophila can be used as a highly genetically-tractable, in vivo system to study the biology of macrophage heterogeneity.

Download Full-text

Identification of functionally distinct macrophage subpopulations in Drosophila

eLife ◽

10.7554/elife.58686 ◽

2021 ◽

Vol 10 ◽

Author(s):

Jonathon Alexis Coates ◽

Elliot Brooks ◽

Amy Louise Brittle ◽

Emma Louise Armitage ◽

Martin Peter Zeidler ◽

...

Keyword(s):

Cell Death ◽

Apoptotic Cell ◽

Homogeneous Population ◽

Cell Numbers ◽

Functional Differences ◽

Heterogeneous Cell Population ◽

Wound Responses ◽

Macrophage Subpopulations ◽

And Function

Vertebrate macrophages are a highly heterogeneous cell population, but whileDrosophilablood is dominated by a macrophage-like lineage (plasmatocytes), until very recently these cells were considered to represent a homogeneous population. Here, we present our identification of enhancer elements labelling plasmatocyte subpopulations, which vary in abundance across development. These subpopulations exhibit functional differences compared to the overall population, including more potent injury responses and differential localisation and dynamics in pupae and adults. Our enhancer analysis identified candidate genes regulating plasmatocyte behaviour: pan-plasmatocyte expression of one such gene (Calnexin14D) improves wound responses, causing the overall population to resemble more closely the subpopulation marked by theCalnexin14D-associated enhancer. Finally, we show that exposure to increased levels of apoptotic cell death modulates subpopulation cell numbers. Taken together this demonstrates macrophage heterogeneity inDrosophila, identifies mechanisms involved in subpopulation specification and function and facilitates the use ofDrosophilato study macrophage heterogeneity in vivo.

Download Full-text

Overexposure to apoptosis via disrupted glial specification perturbs Drosophila macrophage function and reveals roles of the CNS during injury

10.1101/2020.03.04.977546 ◽

2020 ◽

Cited By ~ 1

Author(s):

Emma Louise Armitage ◽

Hannah Grace Roddie ◽

Iwan Robert Evans

Keyword(s):

Inflammatory Responses ◽

Apoptotic Cell ◽

Calcium Waves ◽

Apoptotic Cells ◽

Phagocytic Cells ◽

Macrophage Function ◽

Apoptotic Cell Clearance ◽

Cell Clearance ◽

Wound Responses

AbstractApoptotic cell clearance by phagocytes is a fundamental process during development, homeostasis and the resolution of inflammation. However, the demands placed on phagocytic cells such as macrophages by this process, and the limitations these interactions impose on subsequent cellular behaviours are not yet clear. Here we seek to understand how apoptotic cells affect macrophage function in the context of a genetically-tractable Drosophila model in which macrophages encounter excessive amounts of apoptotic cells. We show that loss of the glial transcription factor repo, and corresponding removal of the contribution these cells make to apoptotic cell clearance, causes macrophages in the developing embryo to be challenged with large numbers of apoptotic cells. As a consequence, macrophages become highly vacuolated with cleared apoptotic cells and their developmental dispersal and migration is perturbed. We also show that the requirement to deal with excess apoptosis caused by a loss of repo function leads to impaired inflammatory responses to injury. However, in contrast to migratory phenotypes, defects in wound responses cannot be rescued by preventing apoptosis from occurring within a repo mutant background. In investigating the underlying cause of these impaired inflammatory responses, we demonstrate that wound-induced calcium waves propagate into surrounding tissues, including neurons and glia of the ventral nerve cord, which exhibit striking calcium waves on wounding, revealing a previously unanticipated contribution of these cells during responses to injury. Taken together these results demonstrate important insights into macrophage biology and how repo mutants can be used to study macrophage-apoptotic cell interactions in the fly embryo.Furthermore, this work shows how these multipurpose cells can be ‘overtasked’ to the detriment of their other functions, alongside providing new insights into which cells govern macrophage responses to injury in vivo.

Download Full-text

Fas ligation induces apoptosis of CD40-activated human B lymphocytes.

Journal of Experimental Medicine ◽

10.1084/jem.182.5.1265 ◽

1995 ◽

Vol 182 (5) ◽

pp. 1265-1273 ◽

Cited By ~ 283

Author(s):

P Garrone ◽

E M Neidhardt ◽

E Garcia ◽

L Galibert ◽

C van Kooten ◽

...

Keyword(s):

B Cells ◽

B Cell ◽

B Lymphocytes ◽

Cell Clone ◽

Apoptotic Cell ◽

Gradient Centrifugation ◽

Cd40 Ligand ◽

Activated T Cells ◽

And Function

Since CD40/CD40 ligand (CD40Lig) interactions are essential in vivo for the generation of germinal center B cells that express Fas (Apo-1/CD95), we explored whether CD40 engagement may modulate Fas expression and function on human B lymphocytes. Resting tonsil B cells, isolated by density gradient centrifugation, express either absent or low levels of Fas. They could be induced to promptly express Fas after ligation of their CD40, however, using either a recombinant human CD40Lig or a cross-linked anti-CD40 mAb. In contrast, engagement of the B cell antigen receptor by immobilized anti-kappa and -lambda antibodies did not turn on Fas expression. Addition of anti-Fas mAb CH11 inhibited the later phases of CD40-induced B cell growth as a result of apoptotic cell death. Furthermore, Fas ligation inhibited proliferation and Ig secretion of CD40-activated B cells in response to recombinant cytokines such as interleukin (IL)-2, IL-4, and IL-10, as well as a cytokine-rich supernatant of phytohemagglutinin-activated T cells, indicating that none of those B cell tropic factors were able to prevent the Fas-induced death. Taken together, the present results show that engagement of CD40 antigen on B cells induces Fas expression and sensitizes them to Fas-mediated apoptosis. The delayed functional response to Fas ligation after CD40 activation may represent a way to limit the size of a specific B cell clone that is generated during T-B cell interactions.

Download Full-text

Apoptotic Regulation in Primitive Hematopoietic Precursors

Blood ◽

10.1182/blood.v92.6.2041.418k34_2041_2052 ◽

1998 ◽

Vol 92 (6) ◽

pp. 2041-2052 ◽

Cited By ~ 1

Author(s):

Rowayda Peters ◽

Serge Leyvraz ◽

Lucien Perey

Keyword(s):

Cell Death ◽

Ex Vivo ◽

Apoptotic Cell ◽

Ex Vivo Expansion ◽

Single Population ◽

Homogeneous Population ◽

Hla Dr ◽

Cd34 Cells ◽

Related Proteins

Bcl-2 and bcl-xL function as suppressors of programmed cell death. The expression of bcl-2 protein in vivo is associated with long-lived hematopoietic cells such as mature lymphocytes and early myeloid progenitors. Bcl-xL, a homologue of bcl-2, is also expressed in lymphocytes and thymocytes. In contrast, the bcl-2-related proteins (bax, bad, and bak) act by promoting apoptotic cell death as shown from their expression in hematopoietic cell lines. We analyzed the expression of bcl-2 and bcl-x proteins in hematopoietic precursors obtained from various cell sources in adult mobilized peripheral blood collected from 13 patients with solid tumors, 8 adult bone marrow, and 12 umbilical cord blood. The analysis was based on the expression of the proliferation and activation specific antigens, CD38 and class II (HLA-DR). Similarly, we analyzed the expression of bcl-2-related proteins bcl-xL, bax, bad, and bak before and during ex-vivo expansion. Hematopoietic precursors expressing strongly the CD34 antigen (CD34s+) and lacking CD38 or HLA-DR expression were analyzed by using three-color immunofluorescence staining. The majority of CD34+ cells expressed bcl-2 and unexpectedly showed a bimodal distribution of low and high expression. More cells that lacked or expressed low density CD38 expressed low bcl-2 than the more differentiated counterparts (those with high density CD38). Immaturity (ie, little or no HLA-DR) is associated with the expression of low bcl-2 compared with HLA-DR+. However, HLA-DR−/low population contained a lower number of cells expressing low bcl-2 (30% to 40%) than CD38−/low in comparable samples. The hematopoietic precursors with bcl-2low and bcl-2high formed a homogeneous population of undifferentiated lymphoid-like cells having a similar forward scatter. These cells expressed strongly the bcl-xL protein (>95%) but were bax low (4% to 12%), bad low (0% to 0.8%), and bak low (0% to 3%). The expression of apoptosis specific protein (ASP) was also low (3.4% ± 3.1%) as was Annexin V. In addition, the CD34+/CD38−showed low cell cycle activity (<2.2%). Induction of apoptosis by overnight incubation of CD34 cells in serum-deprived medium resulted in the upregulation of bcl-2 as a single population histogram. Thus, these results suggest that in quiescent hematopoietic precursors, the bcl-2 protein plays a less prominent role as a survival promoter than bcl-xL and that the low bcl-2 expression did not promote apoptosis. During day 10 of ex vivo expansion of CD34+cells in liquid culture containing stem cell factor, interleukin-3 (IL-3), IL-6, IL-1β, and erythropoietin, the CD34+/CD38− cells expressed high bcl-2 as a single population histogram, and greater than 90% were bcl-xL high. However, the expression of pro- and apoptotic antigens increased: bax (10% to 15%), bad (5% to 8%), bak (6% to 14%), and ASP (6% to 10%). These results show the importance of monitoring the expression of these proteins when defining the culture conditions for ex vivo expansion. © 1998 by The American Society of Hematology.

Download Full-text

Expression of the Phosphatase Ppef2 Controls Survival and Function of CD8+ Dendritic Cells

10.1101/374652 ◽

2018 ◽

Author(s):

Markus Zwick ◽

Thomas Ulas ◽

Yi-Li Cho ◽

Christine Ried ◽

Leonie Grosse ◽

...

Keyword(s):

Dendritic Cells ◽

Protein Phosphatase ◽

Apoptotic Cell ◽

Model Systems ◽

Toll Like Receptor ◽

Cell Responses ◽

Ef Hands ◽

And Function ◽

Dc Maturation

AbstractApoptotic cell death of Dendritic cells (DCs) is critical for immune homeostasis. Although intrinsic mechanisms controlling DC death have not been fully characterized up to now, experimentally enforced inhibition of DC-death causes various autoimmune diseases in model systems. We have generated mice deficient for Protein Phosphatase with EF-Hands 2 (Ppef2), which is selectively expressed in CD8+ DCs, but not in other related DC subtypes such as tissue CD103+ DCs. Ppef2 is down-regulated rapidly upon maturation of DCs by toll-like receptor stimuli, but not upon triggering of CD40. Ppef2-deficient CD8+ DCs accumulate the pro-apoptotic Bcl-2-like protein 11 (Bim) and show increased apoptosis and reduced competitve repopulation capacities. Furthermore, Ppef2−/−CD8+ DCs have strongly diminished antigen presentation capacities in vivo, as CD8+ T cells primed by Ppef2−/− CD8+ DCs undergo reduced expansion. In conclusion, our data suggests that Ppef2 is crucial to support survival of immature CD8+ DCs, while Ppef2 down-regulation during DC-maturation limits T cell responses.

Download Full-text

Apoptotic Regulation in Primitive Hematopoietic Precursors

Blood ◽

10.1182/blood.v92.6.2041 ◽

1998 ◽

Vol 92 (6) ◽

pp. 2041-2052 ◽

Cited By ~ 64

Author(s):

Rowayda Peters ◽

Serge Leyvraz ◽

Lucien Perey

Keyword(s):

Cell Death ◽

Ex Vivo ◽

Apoptotic Cell ◽

Ex Vivo Expansion ◽

Single Population ◽

Homogeneous Population ◽

Hla Dr ◽

Cd34 Cells ◽

Related Proteins

Abstract Bcl-2 and bcl-xL function as suppressors of programmed cell death. The expression of bcl-2 protein in vivo is associated with long-lived hematopoietic cells such as mature lymphocytes and early myeloid progenitors. Bcl-xL, a homologue of bcl-2, is also expressed in lymphocytes and thymocytes. In contrast, the bcl-2-related proteins (bax, bad, and bak) act by promoting apoptotic cell death as shown from their expression in hematopoietic cell lines. We analyzed the expression of bcl-2 and bcl-x proteins in hematopoietic precursors obtained from various cell sources in adult mobilized peripheral blood collected from 13 patients with solid tumors, 8 adult bone marrow, and 12 umbilical cord blood. The analysis was based on the expression of the proliferation and activation specific antigens, CD38 and class II (HLA-DR). Similarly, we analyzed the expression of bcl-2-related proteins bcl-xL, bax, bad, and bak before and during ex-vivo expansion. Hematopoietic precursors expressing strongly the CD34 antigen (CD34s+) and lacking CD38 or HLA-DR expression were analyzed by using three-color immunofluorescence staining. The majority of CD34+ cells expressed bcl-2 and unexpectedly showed a bimodal distribution of low and high expression. More cells that lacked or expressed low density CD38 expressed low bcl-2 than the more differentiated counterparts (those with high density CD38). Immaturity (ie, little or no HLA-DR) is associated with the expression of low bcl-2 compared with HLA-DR+. However, HLA-DR−/low population contained a lower number of cells expressing low bcl-2 (30% to 40%) than CD38−/low in comparable samples. The hematopoietic precursors with bcl-2low and bcl-2high formed a homogeneous population of undifferentiated lymphoid-like cells having a similar forward scatter. These cells expressed strongly the bcl-xL protein (>95%) but were bax low (4% to 12%), bad low (0% to 0.8%), and bak low (0% to 3%). The expression of apoptosis specific protein (ASP) was also low (3.4% ± 3.1%) as was Annexin V. In addition, the CD34+/CD38−showed low cell cycle activity (<2.2%). Induction of apoptosis by overnight incubation of CD34 cells in serum-deprived medium resulted in the upregulation of bcl-2 as a single population histogram. Thus, these results suggest that in quiescent hematopoietic precursors, the bcl-2 protein plays a less prominent role as a survival promoter than bcl-xL and that the low bcl-2 expression did not promote apoptosis. During day 10 of ex vivo expansion of CD34+cells in liquid culture containing stem cell factor, interleukin-3 (IL-3), IL-6, IL-1β, and erythropoietin, the CD34+/CD38− cells expressed high bcl-2 as a single population histogram, and greater than 90% were bcl-xL high. However, the expression of pro- and apoptotic antigens increased: bax (10% to 15%), bad (5% to 8%), bak (6% to 14%), and ASP (6% to 10%). These results show the importance of monitoring the expression of these proteins when defining the culture conditions for ex vivo expansion. © 1998 by The American Society of Hematology.

Download Full-text

Selective Rac1 inhibition in dendritic cells diminishes apoptotic cell uptake and cross-presentation in vivo

Blood ◽

10.1182/blood-2004-05-1891 ◽

2005 ◽

Vol 105 (2) ◽

pp. 742-749 ◽

Cited By ~ 36

Author(s):

Kristen M. Kerksiek ◽

Florence Niedergang ◽

Philippe Chavrier ◽

Dirk H. Busch ◽

Thomas Brocker

Keyword(s):

Transgene Expression ◽

Apoptotic Cell ◽

Cell Uptake ◽

Special Role ◽

Cross Presentation ◽

Cell Responses ◽

Cytoskeletal Regulation ◽

Guanosine Triphosphatase ◽

And Function

Abstract 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.

Download Full-text

Osseointegration interface of calcified bone and endosseous implants

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100130110 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1096-1097

Author(s):

K.E. Krizan ◽

J.E. Laffoon ◽

M.J. Buckley

Keyword(s):

Structure And Function ◽

Titanium Implants ◽

En Bloc ◽

Endosseous Implants ◽

Ultrastructural Studies ◽

The Past ◽

Cacodylate Buffer ◽

One Year ◽

And Function

With increase use of tissue-integrated prostheses in recent years it is a goal to understand what is happening at the interface between haversion bone and bulk metal. This study uses electron microscopy (EM) techniques to establish parameters for osseointegration (structure and function between bone and nonload-carrying implants) in an animal model. In the past the interface has been evaluated extensively with light microscopy methods. Today researchers are using the EM for ultrastructural studies of the bone tissue and implant responses to an in vivo environment. Under general anesthesia nine adult mongrel dogs received three Brånemark (Nobelpharma) 3.75 × 7 mm titanium implants surgical placed in their left zygomatic arch. After a one year healing period the animals were injected with a routine bone marker (oxytetracycline), euthanized and perfused via aortic cannulation with 3% glutaraldehyde in 0.1M cacodylate buffer pH 7.2. Implants were retrieved en bloc, harvest radiographs made (Fig. 1), and routinely embedded in plastic. Tissue and implants were cut into 300 micron thick wafers, longitudinally to the implant with an Isomet saw and diamond wafering blade [Beuhler] until the center of the implant was reached.

Download Full-text

Functional characterization of human brown adipose tissue metabolism

Biochemical Journal ◽

10.1042/bcj20190464 ◽

2020 ◽

Vol 477 (7) ◽

pp. 1261-1286 ◽

Cited By ~ 3

Author(s):

Marie Anne Richard ◽

Hannah Pallubinsky ◽

Denis P. Blondin

Keyword(s):

Adipose Tissue ◽

Brown Adipose Tissue ◽

Functional Characterization ◽

Human Infants ◽

Positron Emission ◽

Brown Adipose ◽

Treatment Of Obesity ◽

And Function

Brown adipose tissue (BAT) has long been described according to its histological features as a multilocular, lipid-containing tissue, light brown in color, that is also responsive to the cold and found especially in hibernating mammals and human infants. Its presence in both hibernators and human infants, combined with its function as a heat-generating organ, raised many questions about its role in humans. Early characterizations of the tissue in humans focused on its progressive atrophy with age and its apparent importance for cold-exposed workers. However, the use of positron emission tomography (PET) with the glucose tracer [18F]fluorodeoxyglucose ([18F]FDG) made it possible to begin characterizing the possible function of BAT in adult humans, and whether it could play a role in the prevention or treatment of obesity and type 2 diabetes (T2D). This review focuses on the in vivo functional characterization of human BAT, the methodological approaches applied to examine these features and addresses critical gaps that remain in moving the field forward. Specifically, we describe the anatomical and biomolecular features of human BAT, the modalities and applications of non-invasive tools such as PET and magnetic resonance imaging coupled with spectroscopy (MRI/MRS) to study BAT morphology and function in vivo, and finally describe the functional characteristics of human BAT that have only been possible through the development and application of such tools.

Download Full-text