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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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CD14 dependence of interaction of apoptotic cells with human and murine macrophages. (A) Interaction (binding and phagocytosis) of 7-d HMDMs with apoptotic BL cells. Interaction between HMDMs and apoptotic BL cells (AC) was assessed after 60-min coculture at 37°C in the presence or absence of CD14 mAbs 61D3 or 63D3. Background interaction of apoptotic cells in the macrophage cultures without added BL cells is also shown (Alone). Results represent the percentage of macrophages interacting with apoptotic cells. Data shown are means ± SEM (n = 2). ANOVA: **, P < 0.01. (B) Interaction of 10-d BMDMs from CD14+/+ (gray bar) and CD14−/− (black bar) mice with apoptotic BL cells assessed after 30-min coculture at 37°C. Data shown are means ± SEM (n = 3). ANOVA: *, P < 0.05. Similar results were observed when syngeneic apoptotic thymocytes were tested in place of BL cells. (C) Photomicrographs showing 10-d BMDMs' interaction with apoptotic BL cells, comprising binding (arrowheads) and phagocytic (arrows) events. (D) Interaction of IgG-opsonized BL cells with the same macrophages as in B. Data are means ± SEM (n = 3). (E) Interaction of peritoneal macrophages from CD14+/+ (gray bar) and CD14−/− (black bar) mice with apoptotic BL cells assessed after 30-min coculture at 37°C. Data shown are means ± SEM (n = 3). ANOVA: *, P < 0.05.
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fig1: CD14 dependence of interaction of apoptotic cells with human and murine macrophages. (A) Interaction (binding and phagocytosis) of 7-d HMDMs with apoptotic BL cells. Interaction between HMDMs and apoptotic BL cells (AC) was assessed after 60-min coculture at 37°C in the presence or absence of CD14 mAbs 61D3 or 63D3. Background interaction of apoptotic cells in the macrophage cultures without added BL cells is also shown (Alone). Results represent the percentage of macrophages interacting with apoptotic cells. Data shown are means ± SEM (n = 2). ANOVA: **, P < 0.01. (B) Interaction of 10-d BMDMs from CD14+/+ (gray bar) and CD14−/− (black bar) mice with apoptotic BL cells assessed after 30-min coculture at 37°C. Data shown are means ± SEM (n = 3). ANOVA: *, P < 0.05. Similar results were observed when syngeneic apoptotic thymocytes were tested in place of BL cells. (C) Photomicrographs showing 10-d BMDMs' interaction with apoptotic BL cells, comprising binding (arrowheads) and phagocytic (arrows) events. (D) Interaction of IgG-opsonized BL cells with the same macrophages as in B. Data are means ± SEM (n = 3). (E) Interaction of peritoneal macrophages from CD14+/+ (gray bar) and CD14−/− (black bar) mice with apoptotic BL cells assessed after 30-min coculture at 37°C. Data shown are means ± SEM (n = 3). ANOVA: *, P < 0.05.

Mentions: We first demonstrated a role for CD14 in the clearance of apoptotic cells by human macrophages using the inhibitory mAb 61D3. The capacity of this CD14 mAb (but not the CD14 mAb 63D3) to inhibit interaction of apoptotic cells with macrophages is confirmed in Fig. 1 A. To determine whether macrophages from CD14-deficient mice were similarly inhibited in their capacity to interact with apoptotic cells, peritoneal or bone marrow–derived macrophages (BMDMs) from CD14+/+ versus CD14−/− mice were compared. As shown in Fig. 1 (B and C), BMDMs from CD14−/− mice were substantially less efficient than their CD14+/+ counterparts in interacting with apoptotic cells, including both binding and phagocytic phases (Fig. 1 C). In contrast, phagocytosis of IgG-opsonized cells was equivalent for both CD14−/− and CD14+/+ BMDMs (Fig. 1 D). Macrophages isolated from the peritoneal cavities of CD14−/− mice were also less effective in interacting with apoptotic cells than their CD14+/+ counterparts, although the difference was less marked than with BMDMs (Fig. 1 E). These results confirm and extend previous observations demonstrating a role for macrophage CD14 as a receptor for apoptotic cells.


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)

CD14 dependence of interaction of apoptotic cells with human and murine macrophages. (A) Interaction (binding and phagocytosis) of 7-d HMDMs with apoptotic BL cells. Interaction between HMDMs and apoptotic BL cells (AC) was assessed after 60-min coculture at 37°C in the presence or absence of CD14 mAbs 61D3 or 63D3. Background interaction of apoptotic cells in the macrophage cultures without added BL cells is also shown (Alone). Results represent the percentage of macrophages interacting with apoptotic cells. Data shown are means ± SEM (n = 2). ANOVA: **, P < 0.01. (B) Interaction of 10-d BMDMs from CD14+/+ (gray bar) and CD14−/− (black bar) mice with apoptotic BL cells assessed after 30-min coculture at 37°C. Data shown are means ± SEM (n = 3). ANOVA: *, P < 0.05. Similar results were observed when syngeneic apoptotic thymocytes were tested in place of BL cells. (C) Photomicrographs showing 10-d BMDMs' interaction with apoptotic BL cells, comprising binding (arrowheads) and phagocytic (arrows) events. (D) Interaction of IgG-opsonized BL cells with the same macrophages as in B. Data are means ± SEM (n = 3). (E) Interaction of peritoneal macrophages from CD14+/+ (gray bar) and CD14−/− (black bar) mice with apoptotic BL cells assessed after 30-min coculture at 37°C. Data shown are means ± SEM (n = 3). ANOVA: *, P < 0.05.
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fig1: CD14 dependence of interaction of apoptotic cells with human and murine macrophages. (A) Interaction (binding and phagocytosis) of 7-d HMDMs with apoptotic BL cells. Interaction between HMDMs and apoptotic BL cells (AC) was assessed after 60-min coculture at 37°C in the presence or absence of CD14 mAbs 61D3 or 63D3. Background interaction of apoptotic cells in the macrophage cultures without added BL cells is also shown (Alone). Results represent the percentage of macrophages interacting with apoptotic cells. Data shown are means ± SEM (n = 2). ANOVA: **, P < 0.01. (B) Interaction of 10-d BMDMs from CD14+/+ (gray bar) and CD14−/− (black bar) mice with apoptotic BL cells assessed after 30-min coculture at 37°C. Data shown are means ± SEM (n = 3). ANOVA: *, P < 0.05. Similar results were observed when syngeneic apoptotic thymocytes were tested in place of BL cells. (C) Photomicrographs showing 10-d BMDMs' interaction with apoptotic BL cells, comprising binding (arrowheads) and phagocytic (arrows) events. (D) Interaction of IgG-opsonized BL cells with the same macrophages as in B. Data are means ± SEM (n = 3). (E) Interaction of peritoneal macrophages from CD14+/+ (gray bar) and CD14−/− (black bar) mice with apoptotic BL cells assessed after 30-min coculture at 37°C. Data shown are means ± SEM (n = 3). ANOVA: *, P < 0.05.
Mentions: We first demonstrated a role for CD14 in the clearance of apoptotic cells by human macrophages using the inhibitory mAb 61D3. The capacity of this CD14 mAb (but not the CD14 mAb 63D3) to inhibit interaction of apoptotic cells with macrophages is confirmed in Fig. 1 A. To determine whether macrophages from CD14-deficient mice were similarly inhibited in their capacity to interact with apoptotic cells, peritoneal or bone marrow–derived macrophages (BMDMs) from CD14+/+ versus CD14−/− mice were compared. As shown in Fig. 1 (B and C), BMDMs from CD14−/− mice were substantially less efficient than their CD14+/+ counterparts in interacting with apoptotic cells, including both binding and phagocytic phases (Fig. 1 C). In contrast, phagocytosis of IgG-opsonized cells was equivalent for both CD14−/− and CD14+/+ BMDMs (Fig. 1 D). Macrophages isolated from the peritoneal cavities of CD14−/− mice were also less effective in interacting with apoptotic cells than their CD14+/+ counterparts, although the difference was less marked than with BMDMs (Fig. 1 E). These results confirm and extend previous observations demonstrating a role for macrophage CD14 as a receptor for apoptotic cells.

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