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Direct evidence for activated CD8+ T cell transmigration across portal vein endothelial cells in liver graft rejection

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ABSTRACT

Background: Lymphocyte recruitment into the portal tract is crucial not only for homeostatic immune surveillance but also for many liver diseases. However, the exact route of entry for lymphocytes into portal tract is still obscure. We investigated this question using a rat hepatic allograft rejection model.

Methods: A migration route was analyzed by immunohistological methods including a recently developed scanning electron microscopy method. Transmigration-associated molecules such as selectins, integrins, and chemokines and their receptors expressed by hepatic vessels and recruited T-cells were analyzed by immunohistochemistry and flow cytometry.

Results: The immunoelectron microscopic analysis clearly showed CD8β+ cells passing through the portal vein (PV) endothelia. Furthermore, the migrating pathway seemed to pass through the endothelial cell body. Local vascular cell adhesion molecule-1 (VCAM-1) expression was induced in PV endothelial cells from day 2 after liver transplantation. Although intercellular adhesion molecule-1 (ICAM-1) expression was also upregulated, it was restricted to sinusoidal endothelia. Recipient T-cells in the graft perfusate were CD25+CD44+ICAM-1+CXCR3+CCR5– and upregulated α4β1 or αLβ2 integrins. Immunohistochemistry showed the expression of CXCL10 in donor MHCIIhigh cells in the portal tract as well as endothelial walls of PV.

Conclusions: We show for the first time direct evidence of T-cell transmigration across PV endothelial cells during hepatic allograft rejection. Interactions between VCAM-1 on endothelia and α4β1 integrin on recipient effector T-cells putatively play critical roles in adhesion and transmigration through endothelia. A chemokine axis of CXCL10 and CXCR3 also may be involved.

Electronic supplementary material: The online version of this article (doi:10.1007/s00535-016-1169-1) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus

TEM image of T-cell transmigration through endothelial cells of the portal vein. a Toluidine blue staining of a semi-thin-section of the portal tract on day 3 after LTx. Red or black arrows indicate transmigrating mononuclear cells. b TEM image of serial sections (dotted line area in a). c Magnified TEM image in dotted line area in b. Note a mononuclear cell, probably a lymphocyte (red arrow), inside an endothelial cell (E: outlined by arrowheads). Also note some protrusion at the leading edge (asterisks in c). Bd bile duct, PV portal vein. Scale bars: a 20 μm; b 10 μm; c 5 μm
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Fig3: TEM image of T-cell transmigration through endothelial cells of the portal vein. a Toluidine blue staining of a semi-thin-section of the portal tract on day 3 after LTx. Red or black arrows indicate transmigrating mononuclear cells. b TEM image of serial sections (dotted line area in a). c Magnified TEM image in dotted line area in b. Note a mononuclear cell, probably a lymphocyte (red arrow), inside an endothelial cell (E: outlined by arrowheads). Also note some protrusion at the leading edge (asterisks in c). Bd bile duct, PV portal vein. Scale bars: a 20 μm; b 10 μm; c 5 μm

Mentions: Light microscopy of semi-thin-sections of the day 3 graft showed binding of several blood cells to the walls of large vessels. Anatomically, these vessels were defined as PVs by the presence of bile ducts in their vicinity (Fig. 3a). TEM observation of serial sections clearly revealed a mononuclear round cell, probably a lymphocyte, passing through an endothelial cell of the PV (Fig. 3b, c). It is noteworthy that its migrating pathway seemed to be a transcellular route, in which migrating cells directly penetrate through the endothelial cell body, rather than an intercellular route. In addition, lamellipodia-like structures were also detected at the leading edge (Fig. 3c, asterisk).Fig. 3


Direct evidence for activated CD8+ T cell transmigration across portal vein endothelial cells in liver graft rejection
TEM image of T-cell transmigration through endothelial cells of the portal vein. a Toluidine blue staining of a semi-thin-section of the portal tract on day 3 after LTx. Red or black arrows indicate transmigrating mononuclear cells. b TEM image of serial sections (dotted line area in a). c Magnified TEM image in dotted line area in b. Note a mononuclear cell, probably a lymphocyte (red arrow), inside an endothelial cell (E: outlined by arrowheads). Also note some protrusion at the leading edge (asterisks in c). Bd bile duct, PV portal vein. Scale bars: a 20 μm; b 10 μm; c 5 μm
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Fig3: TEM image of T-cell transmigration through endothelial cells of the portal vein. a Toluidine blue staining of a semi-thin-section of the portal tract on day 3 after LTx. Red or black arrows indicate transmigrating mononuclear cells. b TEM image of serial sections (dotted line area in a). c Magnified TEM image in dotted line area in b. Note a mononuclear cell, probably a lymphocyte (red arrow), inside an endothelial cell (E: outlined by arrowheads). Also note some protrusion at the leading edge (asterisks in c). Bd bile duct, PV portal vein. Scale bars: a 20 μm; b 10 μm; c 5 μm
Mentions: Light microscopy of semi-thin-sections of the day 3 graft showed binding of several blood cells to the walls of large vessels. Anatomically, these vessels were defined as PVs by the presence of bile ducts in their vicinity (Fig. 3a). TEM observation of serial sections clearly revealed a mononuclear round cell, probably a lymphocyte, passing through an endothelial cell of the PV (Fig. 3b, c). It is noteworthy that its migrating pathway seemed to be a transcellular route, in which migrating cells directly penetrate through the endothelial cell body, rather than an intercellular route. In addition, lamellipodia-like structures were also detected at the leading edge (Fig. 3c, asterisk).Fig. 3

View Article: PubMed Central - PubMed

ABSTRACT

Background: Lymphocyte recruitment into the portal tract is crucial not only for homeostatic immune surveillance but also for many liver diseases. However, the exact route of entry for lymphocytes into portal tract is still obscure. We investigated this question using a rat hepatic allograft rejection model.

Methods: A migration route was analyzed by immunohistological methods including a recently developed scanning electron microscopy method. Transmigration-associated molecules such as selectins, integrins, and chemokines and their receptors expressed by hepatic vessels and recruited T-cells were analyzed by immunohistochemistry and flow cytometry.

Results: The immunoelectron microscopic analysis clearly showed CD8β+ cells passing through the portal vein (PV) endothelia. Furthermore, the migrating pathway seemed to pass through the endothelial cell body. Local vascular cell adhesion molecule-1 (VCAM-1) expression was induced in PV endothelial cells from day 2 after liver transplantation. Although intercellular adhesion molecule-1 (ICAM-1) expression was also upregulated, it was restricted to sinusoidal endothelia. Recipient T-cells in the graft perfusate were CD25+CD44+ICAM-1+CXCR3+CCR5– and upregulated α4β1 or αLβ2 integrins. Immunohistochemistry showed the expression of CXCL10 in donor MHCIIhigh cells in the portal tract as well as endothelial walls of PV.

Conclusions: We show for the first time direct evidence of T-cell transmigration across PV endothelial cells during hepatic allograft rejection. Interactions between VCAM-1 on endothelia and α4β1 integrin on recipient effector T-cells putatively play critical roles in adhesion and transmigration through endothelia. A chemokine axis of CXCL10 and CXCR3 also may be involved.

Electronic supplementary material: The online version of this article (doi:10.1007/s00535-016-1169-1) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus