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Epithelial ICAM-1 and ICAM-2 regulate the egression of human T cells across the bronchial epithelium.

Porter JC, Hall A - FASEB J. (2008)

Bottom Line: We, therefore, looked for other epithelial ligands for LFA-1 and demonstrate that ICAM-2, but not ICAM-3, is expressed on the bronchial epithelium.Inhibition of LFA-1/ICAM-1 and ICAM-2 interactions on the basolateral epithelium does not prevent egressing T cells from adhering, polarizing, or moving over the basal epithelium, but it does prevent their recognition of the interepithelial junctions.In conclusion, we show that egression of T cells involves three distinct sequential steps: adhesion, junctional recognition, and diapedesis; we further demonstrate that ICAM-2 is expressed on the bronchial epithelium and, together with ICAM-1, has an essential function in the clearance of T cells from the lung.

View Article: PubMed Central - PubMed

Affiliation: Medical Research Council Laboratory of Molecular Cell Biology, University College London, London, UK. joanna.porter@ucl.ac.uk

ABSTRACT
Egression of inflammatory cells from the lung interstitium into the airway lumen is critical for the resolution of inflammation, but the underlying mechanisms of this egression are unclear. Here, we use an in vitro system, in which human T cells migrate across a bronchial epithelial monolayer, to investigate the molecules involved. We show that although inhibition of T-cell LFA-1 blocks egression by 75 +/- 5.6% (P<0.0001), inhibition of the LFA-1-ligand ICAM-1 on the epithelium only inhibits by 52.7 +/- 0.06% (P=0.0001). We, therefore, looked for other epithelial ligands for LFA-1 and demonstrate that ICAM-2, but not ICAM-3, is expressed on the bronchial epithelium. Blocking ICAM-2 inhibits egression by 50.95 +/- 10.79% (P=0.04), and blocking both ICAM-1 and ICAM-2 inhibits egression by 69.6 +/- 5.2% (P< 0.0001). Inhibition of LFA-1/ICAM-1 and ICAM-2 interactions on the basolateral epithelium does not prevent egressing T cells from adhering, polarizing, or moving over the basal epithelium, but it does prevent their recognition of the interepithelial junctions. In conclusion, we show that egression of T cells involves three distinct sequential steps: adhesion, junctional recognition, and diapedesis; we further demonstrate that ICAM-2 is expressed on the bronchial epithelium and, together with ICAM-1, has an essential function in the clearance of T cells from the lung.

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Effect of cytochalasin D and wiskostatin on the redistribution of epithelial ICAM-1. Epithelial monolayers were left untreated (A–C, J), or treated with 2 μm cytochalasin D (D–F, K) or 50 μm wiskostatin (G–I, L) for 2 h, before washing out the inhibitor, fixing the monolayers, and staining on both sides of the monolayer with a mAb against ICAM-1. Panels show confocal images, collected under identical conditions and settings, of 2.5-μm stacks from different regions of the epithelium: basal (A, D, G, J–L), middle (B, E, H), and apical (C, F, I). Panels J–L show higher magnifications of representative areas of panels A, D, and G, respectively. One representative experiment of 3 is shown. Scale bars = 10 μm.
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Figure 7: Effect of cytochalasin D and wiskostatin on the redistribution of epithelial ICAM-1. Epithelial monolayers were left untreated (A–C, J), or treated with 2 μm cytochalasin D (D–F, K) or 50 μm wiskostatin (G–I, L) for 2 h, before washing out the inhibitor, fixing the monolayers, and staining on both sides of the monolayer with a mAb against ICAM-1. Panels show confocal images, collected under identical conditions and settings, of 2.5-μm stacks from different regions of the epithelium: basal (A, D, G, J–L), middle (B, E, H), and apical (C, F, I). Panels J–L show higher magnifications of representative areas of panels A, D, and G, respectively. One representative experiment of 3 is shown. Scale bars = 10 μm.

Mentions: Wiskostatin treatment of the epithelium-inhibited T-cell egression at a step that took place after adhesion but before diapedesis, and it did so despite loosening the tight junctions. This inhibition was indistinguishable from that caused by inhibiting LFA-1/ICAM-1 and ICAM-2 binding. We therefore investigated the effect of wiskostatin on epithelial ICAM-1 expression. Epithelial monolayers were left untreated (Fig. 7A–C, J) or were treated with 2 μm cytochalasin D (Fig. 7D–F, K) or 50 μm wiskostatin (Fig. 7G–I, L) for 2 h, before washing out the inhibitor, fixing the monolayers, and staining them with a mAb directed against ICAM-1. Confocal images were taken of 2.5-μm stacks from the three different regions of the epithelium; basal (Fig. 7A, D, G, J–L), middle (Fig. 7B, E, H), and apical (Fig. 7C, F, I). In the control monolayers, the majority of the ICAM-1 was seen on the apical surface (Fig. 7C) and in the epithelial cell-cell contact areas (Fig. 7A–C). Treatment with cytochalasin D caused clustering of the ICAM-1 at cell-cell contacts (Fig. 7D–F) but did not dramatically increase the amount of ICAM-1 seen on the basal surface (Fig. 7D, K). Wiskostatin treatment increased the amount of ICAM-1 seen at the cell-cell junctions (Fig. 7G–I) but also on the basal surface of the epithelium (Fig. 7L). Thus, wiskostatin caused a redistribution of ICAM-1 on the bronchial epithelium, resulting in expression of ICAM-1 on both the basal and apical epithelial surfaces, which might disrupt the normal ICAM-1 gradient.


Epithelial ICAM-1 and ICAM-2 regulate the egression of human T cells across the bronchial epithelium.

Porter JC, Hall A - FASEB J. (2008)

Effect of cytochalasin D and wiskostatin on the redistribution of epithelial ICAM-1. Epithelial monolayers were left untreated (A–C, J), or treated with 2 μm cytochalasin D (D–F, K) or 50 μm wiskostatin (G–I, L) for 2 h, before washing out the inhibitor, fixing the monolayers, and staining on both sides of the monolayer with a mAb against ICAM-1. Panels show confocal images, collected under identical conditions and settings, of 2.5-μm stacks from different regions of the epithelium: basal (A, D, G, J–L), middle (B, E, H), and apical (C, F, I). Panels J–L show higher magnifications of representative areas of panels A, D, and G, respectively. One representative experiment of 3 is shown. Scale bars = 10 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2630786&req=5

Figure 7: Effect of cytochalasin D and wiskostatin on the redistribution of epithelial ICAM-1. Epithelial monolayers were left untreated (A–C, J), or treated with 2 μm cytochalasin D (D–F, K) or 50 μm wiskostatin (G–I, L) for 2 h, before washing out the inhibitor, fixing the monolayers, and staining on both sides of the monolayer with a mAb against ICAM-1. Panels show confocal images, collected under identical conditions and settings, of 2.5-μm stacks from different regions of the epithelium: basal (A, D, G, J–L), middle (B, E, H), and apical (C, F, I). Panels J–L show higher magnifications of representative areas of panels A, D, and G, respectively. One representative experiment of 3 is shown. Scale bars = 10 μm.
Mentions: Wiskostatin treatment of the epithelium-inhibited T-cell egression at a step that took place after adhesion but before diapedesis, and it did so despite loosening the tight junctions. This inhibition was indistinguishable from that caused by inhibiting LFA-1/ICAM-1 and ICAM-2 binding. We therefore investigated the effect of wiskostatin on epithelial ICAM-1 expression. Epithelial monolayers were left untreated (Fig. 7A–C, J) or were treated with 2 μm cytochalasin D (Fig. 7D–F, K) or 50 μm wiskostatin (Fig. 7G–I, L) for 2 h, before washing out the inhibitor, fixing the monolayers, and staining them with a mAb directed against ICAM-1. Confocal images were taken of 2.5-μm stacks from the three different regions of the epithelium; basal (Fig. 7A, D, G, J–L), middle (Fig. 7B, E, H), and apical (Fig. 7C, F, I). In the control monolayers, the majority of the ICAM-1 was seen on the apical surface (Fig. 7C) and in the epithelial cell-cell contact areas (Fig. 7A–C). Treatment with cytochalasin D caused clustering of the ICAM-1 at cell-cell contacts (Fig. 7D–F) but did not dramatically increase the amount of ICAM-1 seen on the basal surface (Fig. 7D, K). Wiskostatin treatment increased the amount of ICAM-1 seen at the cell-cell junctions (Fig. 7G–I) but also on the basal surface of the epithelium (Fig. 7L). Thus, wiskostatin caused a redistribution of ICAM-1 on the bronchial epithelium, resulting in expression of ICAM-1 on both the basal and apical epithelial surfaces, which might disrupt the normal ICAM-1 gradient.

Bottom Line: We, therefore, looked for other epithelial ligands for LFA-1 and demonstrate that ICAM-2, but not ICAM-3, is expressed on the bronchial epithelium.Inhibition of LFA-1/ICAM-1 and ICAM-2 interactions on the basolateral epithelium does not prevent egressing T cells from adhering, polarizing, or moving over the basal epithelium, but it does prevent their recognition of the interepithelial junctions.In conclusion, we show that egression of T cells involves three distinct sequential steps: adhesion, junctional recognition, and diapedesis; we further demonstrate that ICAM-2 is expressed on the bronchial epithelium and, together with ICAM-1, has an essential function in the clearance of T cells from the lung.

View Article: PubMed Central - PubMed

Affiliation: Medical Research Council Laboratory of Molecular Cell Biology, University College London, London, UK. joanna.porter@ucl.ac.uk

ABSTRACT
Egression of inflammatory cells from the lung interstitium into the airway lumen is critical for the resolution of inflammation, but the underlying mechanisms of this egression are unclear. Here, we use an in vitro system, in which human T cells migrate across a bronchial epithelial monolayer, to investigate the molecules involved. We show that although inhibition of T-cell LFA-1 blocks egression by 75 +/- 5.6% (P<0.0001), inhibition of the LFA-1-ligand ICAM-1 on the epithelium only inhibits by 52.7 +/- 0.06% (P=0.0001). We, therefore, looked for other epithelial ligands for LFA-1 and demonstrate that ICAM-2, but not ICAM-3, is expressed on the bronchial epithelium. Blocking ICAM-2 inhibits egression by 50.95 +/- 10.79% (P=0.04), and blocking both ICAM-1 and ICAM-2 inhibits egression by 69.6 +/- 5.2% (P< 0.0001). Inhibition of LFA-1/ICAM-1 and ICAM-2 interactions on the basolateral epithelium does not prevent egressing T cells from adhering, polarizing, or moving over the basal epithelium, but it does prevent their recognition of the interepithelial junctions. In conclusion, we show that egression of T cells involves three distinct sequential steps: adhesion, junctional recognition, and diapedesis; we further demonstrate that ICAM-2 is expressed on the bronchial epithelium and, together with ICAM-1, has an essential function in the clearance of T cells from the lung.

Show MeSH
Related in: MedlinePlus