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Persistence of apoptotic cells without autoimmune disease or inflammation in CD14-/- mice.

Devitt A, Parker KG, Ogden CA, Oldreive C, Clay MF, Melville LA, Bellamy CO, Lacy-Hulbert A, Gangloff SC, Goyert SM, Gregory CD - J. Cell Biol. (2004)

Bottom Line: Significantly, CD14(-/-) macrophages in vivo are defective in clearing apoptotic cells in multiple tissues, suggesting a broad role for CD14 in the clearance process.However, the resultant persistence of apoptotic cells does not lead to inflammation or increased autoantibody production, most likely because, as we show, CD14(-/-) macrophages retain the ability to generate anti-inflammatory signals in response to apoptotic cells.We conclude that CD14 plays a broad tethering role in apoptotic cell clearance in vivo and that apoptotic cells can persist in the absence of proinflammatory consequences.

View Article: PubMed Central - PubMed

Affiliation: Medical Research Council Centre for Inflammation Research, University of Edinburgh, Edinburgh, Scotland, UK.

ABSTRACT
Interaction of macrophages with apoptotic cells involves multiple steps including recognition, tethering, phagocytosis, and anti-inflammatory macrophage responses. Defective apoptotic cell clearance is associated with pathogenesis of autoimmune disease. CD14 is a surface receptor that functions in vitro in the removal of apoptotic cells by human and murine macrophages, but its mechanism of action has not been defined. Here, we demonstrate that CD14 functions as a macrophage tethering receptor for apoptotic cells. Significantly, CD14(-/-) macrophages in vivo are defective in clearing apoptotic cells in multiple tissues, suggesting a broad role for CD14 in the clearance process. However, the resultant persistence of apoptotic cells does not lead to inflammation or increased autoantibody production, most likely because, as we show, CD14(-/-) macrophages retain the ability to generate anti-inflammatory signals in response to apoptotic cells. We conclude that CD14 plays a broad tethering role in apoptotic cell clearance in vivo and that apoptotic cells can persist in the absence of proinflammatory consequences.

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Inefficient interaction of apoptotic thymocytes with resident peritoneal macrophages in CD14−/− mice. Fluorescent (green) autologous apoptotic thymocytes in PBS were introduced into the peritoneal cavity of CD14+/+ or CD14−/− mice by i.p. injection. Control animals received i.p. PBS alone. After 15 min, peritoneal cells were harvested, stained with F4/80, and analyzed by flow cytometry. Similar numbers of resident F4/80+ peritoneal macrophages were obtained from CD14+/+ and CD14−/− animals. (A) Representative flow cytometric dot plots of apoptotic (green) cells (AC) versus (red) F4/80+ events (macrophages). (B) Collated data from CD14+/+ and CD14−/− mice tested (means ± SEM; n = 3 animals in each case). ANOVA: *, P < 0.05.
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fig4: Inefficient interaction of apoptotic thymocytes with resident peritoneal macrophages in CD14−/− mice. Fluorescent (green) autologous apoptotic thymocytes in PBS were introduced into the peritoneal cavity of CD14+/+ or CD14−/− mice by i.p. injection. Control animals received i.p. PBS alone. After 15 min, peritoneal cells were harvested, stained with F4/80, and analyzed by flow cytometry. Similar numbers of resident F4/80+ peritoneal macrophages were obtained from CD14+/+ and CD14−/− animals. (A) Representative flow cytometric dot plots of apoptotic (green) cells (AC) versus (red) F4/80+ events (macrophages). (B) Collated data from CD14+/+ and CD14−/− mice tested (means ± SEM; n = 3 animals in each case). ANOVA: *, P < 0.05.

Mentions: To define more precisely if CD14−/− mice display defects in their ability to clear apoptotic cells in vivo, we determined the extent to which apoptotic cells administered i.p. could be cleared by resident macrophages. To this end, CD14+/+ or CD14−/− mice were injected i.p. with fluorescent, apoptotic thymocytes and after 15 min coincubation in situ the proportion of peritoneal macrophages interacting with apoptotic cells was enumerated by flow cytometry following F4/80 immunofluorescence staining (Fig. 4). As shown, effective discrimination of apoptotic thymocytes, F4/80+ macrophages, and macrophages interacting with apoptotic thymocytes was possible (Fig. 4 A). Microscopic analyses of sorted populations indicated that those events displaying dual fluorescence (i.e., F4/80+, apoptotic cell+) represented macrophages with bound and/or engulfed apoptotic thymocytes (unpublished data). Quantitative analysis of multiple experiments (Fig. 4 B) showed that peritoneal macrophages from CD14−/− animals were markedly reduced in their ability to interact with apoptotic cells to a level that was approximately half the capacity of CD14+/+ macrophages. These results provide further evidence that apoptotic cells persist in CD14−/− mice as a result of defective clearance by macrophages.


Persistence of apoptotic cells without autoimmune disease or inflammation in CD14-/- mice.

Devitt A, Parker KG, Ogden CA, Oldreive C, Clay MF, Melville LA, Bellamy CO, Lacy-Hulbert A, Gangloff SC, Goyert SM, Gregory CD - J. Cell Biol. (2004)

Inefficient interaction of apoptotic thymocytes with resident peritoneal macrophages in CD14−/− mice. Fluorescent (green) autologous apoptotic thymocytes in PBS were introduced into the peritoneal cavity of CD14+/+ or CD14−/− mice by i.p. injection. Control animals received i.p. PBS alone. After 15 min, peritoneal cells were harvested, stained with F4/80, and analyzed by flow cytometry. Similar numbers of resident F4/80+ peritoneal macrophages were obtained from CD14+/+ and CD14−/− animals. (A) Representative flow cytometric dot plots of apoptotic (green) cells (AC) versus (red) F4/80+ events (macrophages). (B) Collated data from CD14+/+ and CD14−/− mice tested (means ± SEM; n = 3 animals in each case). ANOVA: *, P < 0.05.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2172617&req=5

fig4: Inefficient interaction of apoptotic thymocytes with resident peritoneal macrophages in CD14−/− mice. Fluorescent (green) autologous apoptotic thymocytes in PBS were introduced into the peritoneal cavity of CD14+/+ or CD14−/− mice by i.p. injection. Control animals received i.p. PBS alone. After 15 min, peritoneal cells were harvested, stained with F4/80, and analyzed by flow cytometry. Similar numbers of resident F4/80+ peritoneal macrophages were obtained from CD14+/+ and CD14−/− animals. (A) Representative flow cytometric dot plots of apoptotic (green) cells (AC) versus (red) F4/80+ events (macrophages). (B) Collated data from CD14+/+ and CD14−/− mice tested (means ± SEM; n = 3 animals in each case). ANOVA: *, P < 0.05.
Mentions: To define more precisely if CD14−/− mice display defects in their ability to clear apoptotic cells in vivo, we determined the extent to which apoptotic cells administered i.p. could be cleared by resident macrophages. To this end, CD14+/+ or CD14−/− mice were injected i.p. with fluorescent, apoptotic thymocytes and after 15 min coincubation in situ the proportion of peritoneal macrophages interacting with apoptotic cells was enumerated by flow cytometry following F4/80 immunofluorescence staining (Fig. 4). As shown, effective discrimination of apoptotic thymocytes, F4/80+ macrophages, and macrophages interacting with apoptotic thymocytes was possible (Fig. 4 A). Microscopic analyses of sorted populations indicated that those events displaying dual fluorescence (i.e., F4/80+, apoptotic cell+) represented macrophages with bound and/or engulfed apoptotic thymocytes (unpublished data). Quantitative analysis of multiple experiments (Fig. 4 B) showed that peritoneal macrophages from CD14−/− animals were markedly reduced in their ability to interact with apoptotic cells to a level that was approximately half the capacity of CD14+/+ macrophages. These results provide further evidence that apoptotic cells persist in CD14−/− mice as a result of defective clearance by macrophages.

Bottom Line: Significantly, CD14(-/-) macrophages in vivo are defective in clearing apoptotic cells in multiple tissues, suggesting a broad role for CD14 in the clearance process.However, the resultant persistence of apoptotic cells does not lead to inflammation or increased autoantibody production, most likely because, as we show, CD14(-/-) macrophages retain the ability to generate anti-inflammatory signals in response to apoptotic cells.We conclude that CD14 plays a broad tethering role in apoptotic cell clearance in vivo and that apoptotic cells can persist in the absence of proinflammatory consequences.

View Article: PubMed Central - PubMed

Affiliation: Medical Research Council Centre for Inflammation Research, University of Edinburgh, Edinburgh, Scotland, UK.

ABSTRACT
Interaction of macrophages with apoptotic cells involves multiple steps including recognition, tethering, phagocytosis, and anti-inflammatory macrophage responses. Defective apoptotic cell clearance is associated with pathogenesis of autoimmune disease. CD14 is a surface receptor that functions in vitro in the removal of apoptotic cells by human and murine macrophages, but its mechanism of action has not been defined. Here, we demonstrate that CD14 functions as a macrophage tethering receptor for apoptotic cells. Significantly, CD14(-/-) macrophages in vivo are defective in clearing apoptotic cells in multiple tissues, suggesting a broad role for CD14 in the clearance process. However, the resultant persistence of apoptotic cells does not lead to inflammation or increased autoantibody production, most likely because, as we show, CD14(-/-) macrophages retain the ability to generate anti-inflammatory signals in response to apoptotic cells. We conclude that CD14 plays a broad tethering role in apoptotic cell clearance in vivo and that apoptotic cells can persist in the absence of proinflammatory consequences.

Show MeSH
Related in: MedlinePlus