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Visualization of Plasmodium falciparum-endothelium interactions in human microvasculature: mimicry of leukocyte recruitment.

Ho M, Hickey MJ, Murray AG, Andonegui G, Kubes P - J. Exp. Med. (2000)

Bottom Line: More importantly, already adherent cells quickly detached.The residual rolling after anti-CD36 treatment was largely inhibited by an anti-ICAM-1 antibody.These findings provide conclusive evidence that infected erythrocytes interact within the human microvasculature in vivo by a multistep adhesive cascade that mimics the process of leukocyte recruitment.

View Article: PubMed Central - PubMed

Affiliation: Immunology Research Group, University of Calgary, Calgary, Alberta, Canada T2N 4N1. mho@ucalgary.ca

ABSTRACT
Plasmodium falciparum-infected erythrocytes roll on and/or adhere to CD36, intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1, and P-selectin under shear conditions in vitro. However, the lack of an adequate animal model has made it difficult to determine whether infected erythrocytes do indeed interact in vivo in microvessels. Therefore, we made use of an established model of human skin grafted onto severe combined immunodeficient (SCID) mice to directly visualize the human microvasculature by epifluorescence intravital microscopy. In all grafts examined, infected erythrocytes were observed to roll and/or adhere in not just postcapillary venules but also in arterioles. In contrast, occlusion of capillaries by infected erythrocytes was noted only in approximately half of the experiments. Administration of an anti-CD36 antibody resulted in a rapid reduction of rolling and adhesion. More importantly, already adherent cells quickly detached. The residual rolling after anti-CD36 treatment was largely inhibited by an anti-ICAM-1 antibody. Anti-ICAM-1 alone reduced the ability of infected erythrocytes to sustain rolling and subsequent adhesion. These findings provide conclusive evidence that infected erythrocytes interact within the human microvasculature in vivo by a multistep adhesive cascade that mimics the process of leukocyte recruitment.

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Interactions of infected erythrocytes and human endothelial cells in the human skin graft model. Panels a–c illustrate the same vascular field within the human skin graft. To aid identification, the vascular walls are indicated by lines. Adherent or slowly moving (rolling) infected erythrocytes are visible as discrete circular objects, while noninteracting infected erythrocytes are observed as streaks in the centerline of blood flow. Uninfected erythrocytes are unlabeled. Panels a and b are separated by ∼3 s. Arrows indicate infected erythrocytes undergoing rolling interactions with the endothelial surface of a postcapillary venule within the graft. Over the 3-s time course, the rolling infected erythrocytes have moved slowly along the vascular wall. At the same time, the patency of the microcirculation is apparent as rapidly-moving, noninteracting infected erythrocytes are observed throughout this period. Panel c illustrates the same area of microvasculature after dual treatment with mAbs against human CD36 and ICAM-1. Very few interacting infected erythrocytes are observed despite many cells continuing to pass through the graft microvasculature. Videos illustrating the above points are explained in the online supplemental material section and are available at http://www.jem.org.cgi/content/full/192/8/1205/DC1.
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Figure 2: Interactions of infected erythrocytes and human endothelial cells in the human skin graft model. Panels a–c illustrate the same vascular field within the human skin graft. To aid identification, the vascular walls are indicated by lines. Adherent or slowly moving (rolling) infected erythrocytes are visible as discrete circular objects, while noninteracting infected erythrocytes are observed as streaks in the centerline of blood flow. Uninfected erythrocytes are unlabeled. Panels a and b are separated by ∼3 s. Arrows indicate infected erythrocytes undergoing rolling interactions with the endothelial surface of a postcapillary venule within the graft. Over the 3-s time course, the rolling infected erythrocytes have moved slowly along the vascular wall. At the same time, the patency of the microcirculation is apparent as rapidly-moving, noninteracting infected erythrocytes are observed throughout this period. Panel c illustrates the same area of microvasculature after dual treatment with mAbs against human CD36 and ICAM-1. Very few interacting infected erythrocytes are observed despite many cells continuing to pass through the graft microvasculature. Videos illustrating the above points are explained in the online supplemental material section and are available at http://www.jem.org.cgi/content/full/192/8/1205/DC1.

Mentions: Rhodamine-labeled infected erythrocytes containing trophozoites and schizonts were injected intravenously into the animals. Infected erythrocytes continued to circulate in significant numbers for ∼10–15 min, after which parasite accumulation was apparent in the spleen. In all eight grafts examined, infected erythrocytes were observed to roll and/or adhere in postcapillary venules of the human skin graft (Fig. 2). Surprisingly, infected erythrocytes also interacted with arterioles in 75% of grafts examined. The percentages of infected erythrocytes that undergo rolling on and adhesion to both sides of the microvasculature are shown in Fig. 3. In postcapillary venules, ∼6% of the total number of passing infected erythrocytes underwent rolling interactions, whereas 10% rolled in arterioles. Adhesion of infected erythrocytes was also observed. Significant adhesion of infected erythrocytes was observed in postcapillary venules in seven of eight grafts and in arterioles in one of four grafts. Approximately two-thirds of the adherent infected erythrocytes rolled for various distances before becoming arrested, while the rest appeared to bypass the rolling event and adhered immediately after tethering. In addition, occlusion of some capillaries by infected erythrocytes was observed after parasite injection in five of eight grafts. Infected erythrocytes did not interact with murine blood vessels in the surrounding skin, consistent with the species specificity of the infection.


Visualization of Plasmodium falciparum-endothelium interactions in human microvasculature: mimicry of leukocyte recruitment.

Ho M, Hickey MJ, Murray AG, Andonegui G, Kubes P - J. Exp. Med. (2000)

Interactions of infected erythrocytes and human endothelial cells in the human skin graft model. Panels a–c illustrate the same vascular field within the human skin graft. To aid identification, the vascular walls are indicated by lines. Adherent or slowly moving (rolling) infected erythrocytes are visible as discrete circular objects, while noninteracting infected erythrocytes are observed as streaks in the centerline of blood flow. Uninfected erythrocytes are unlabeled. Panels a and b are separated by ∼3 s. Arrows indicate infected erythrocytes undergoing rolling interactions with the endothelial surface of a postcapillary venule within the graft. Over the 3-s time course, the rolling infected erythrocytes have moved slowly along the vascular wall. At the same time, the patency of the microcirculation is apparent as rapidly-moving, noninteracting infected erythrocytes are observed throughout this period. Panel c illustrates the same area of microvasculature after dual treatment with mAbs against human CD36 and ICAM-1. Very few interacting infected erythrocytes are observed despite many cells continuing to pass through the graft microvasculature. Videos illustrating the above points are explained in the online supplemental material section and are available at http://www.jem.org.cgi/content/full/192/8/1205/DC1.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2195873&req=5

Figure 2: Interactions of infected erythrocytes and human endothelial cells in the human skin graft model. Panels a–c illustrate the same vascular field within the human skin graft. To aid identification, the vascular walls are indicated by lines. Adherent or slowly moving (rolling) infected erythrocytes are visible as discrete circular objects, while noninteracting infected erythrocytes are observed as streaks in the centerline of blood flow. Uninfected erythrocytes are unlabeled. Panels a and b are separated by ∼3 s. Arrows indicate infected erythrocytes undergoing rolling interactions with the endothelial surface of a postcapillary venule within the graft. Over the 3-s time course, the rolling infected erythrocytes have moved slowly along the vascular wall. At the same time, the patency of the microcirculation is apparent as rapidly-moving, noninteracting infected erythrocytes are observed throughout this period. Panel c illustrates the same area of microvasculature after dual treatment with mAbs against human CD36 and ICAM-1. Very few interacting infected erythrocytes are observed despite many cells continuing to pass through the graft microvasculature. Videos illustrating the above points are explained in the online supplemental material section and are available at http://www.jem.org.cgi/content/full/192/8/1205/DC1.
Mentions: Rhodamine-labeled infected erythrocytes containing trophozoites and schizonts were injected intravenously into the animals. Infected erythrocytes continued to circulate in significant numbers for ∼10–15 min, after which parasite accumulation was apparent in the spleen. In all eight grafts examined, infected erythrocytes were observed to roll and/or adhere in postcapillary venules of the human skin graft (Fig. 2). Surprisingly, infected erythrocytes also interacted with arterioles in 75% of grafts examined. The percentages of infected erythrocytes that undergo rolling on and adhesion to both sides of the microvasculature are shown in Fig. 3. In postcapillary venules, ∼6% of the total number of passing infected erythrocytes underwent rolling interactions, whereas 10% rolled in arterioles. Adhesion of infected erythrocytes was also observed. Significant adhesion of infected erythrocytes was observed in postcapillary venules in seven of eight grafts and in arterioles in one of four grafts. Approximately two-thirds of the adherent infected erythrocytes rolled for various distances before becoming arrested, while the rest appeared to bypass the rolling event and adhered immediately after tethering. In addition, occlusion of some capillaries by infected erythrocytes was observed after parasite injection in five of eight grafts. Infected erythrocytes did not interact with murine blood vessels in the surrounding skin, consistent with the species specificity of the infection.

Bottom Line: More importantly, already adherent cells quickly detached.The residual rolling after anti-CD36 treatment was largely inhibited by an anti-ICAM-1 antibody.These findings provide conclusive evidence that infected erythrocytes interact within the human microvasculature in vivo by a multistep adhesive cascade that mimics the process of leukocyte recruitment.

View Article: PubMed Central - PubMed

Affiliation: Immunology Research Group, University of Calgary, Calgary, Alberta, Canada T2N 4N1. mho@ucalgary.ca

ABSTRACT
Plasmodium falciparum-infected erythrocytes roll on and/or adhere to CD36, intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1, and P-selectin under shear conditions in vitro. However, the lack of an adequate animal model has made it difficult to determine whether infected erythrocytes do indeed interact in vivo in microvessels. Therefore, we made use of an established model of human skin grafted onto severe combined immunodeficient (SCID) mice to directly visualize the human microvasculature by epifluorescence intravital microscopy. In all grafts examined, infected erythrocytes were observed to roll and/or adhere in not just postcapillary venules but also in arterioles. In contrast, occlusion of capillaries by infected erythrocytes was noted only in approximately half of the experiments. Administration of an anti-CD36 antibody resulted in a rapid reduction of rolling and adhesion. More importantly, already adherent cells quickly detached. The residual rolling after anti-CD36 treatment was largely inhibited by an anti-ICAM-1 antibody. Anti-ICAM-1 alone reduced the ability of infected erythrocytes to sustain rolling and subsequent adhesion. These findings provide conclusive evidence that infected erythrocytes interact within the human microvasculature in vivo by a multistep adhesive cascade that mimics the process of leukocyte recruitment.

Show MeSH
Related in: MedlinePlus