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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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ICAM-1 and ICAM-2, but not ICAM-3 expression on bronchial epithelial cells. A, B) FACS analysis of ICAM-1 and ICAM-2 expression on 16HBE cells (A) and primary human bronchial epithelial cells (B). Peaks are labeled to their right and show unlabeled epithelial cells, isotype-matched control (anti-CD3), ICAM-1, ICAM-2, and ICAM-3. One experiment representative of 3 similar experiments is shown. LSCM was used to image ICAM-2 staining of a bronchial epithelial monolayer grown on a filter. (MAb to ICAM-2 was presented on both sides of the monolayer). C) The cartoon demonstrates the position of the serial Z series. D–H′) Monolayers are stained for actin (D–H) and ICAM-2 (D′–H′). Projected Z series of 5 images taken at 0.1-μm intervals are shown for basal (D, D′), middle (E, E′–F, F′), apical (G, G′), and luminal epithelium (H, H′). One representative experiment of 3 is shown.
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Figure 2: ICAM-1 and ICAM-2, but not ICAM-3 expression on bronchial epithelial cells. A, B) FACS analysis of ICAM-1 and ICAM-2 expression on 16HBE cells (A) and primary human bronchial epithelial cells (B). Peaks are labeled to their right and show unlabeled epithelial cells, isotype-matched control (anti-CD3), ICAM-1, ICAM-2, and ICAM-3. One experiment representative of 3 similar experiments is shown. LSCM was used to image ICAM-2 staining of a bronchial epithelial monolayer grown on a filter. (MAb to ICAM-2 was presented on both sides of the monolayer). C) The cartoon demonstrates the position of the serial Z series. D–H′) Monolayers are stained for actin (D–H) and ICAM-2 (D′–H′). Projected Z series of 5 images taken at 0.1-μm intervals are shown for basal (D, D′), middle (E, E′–F, F′), apical (G, G′), and luminal epithelium (H, H′). One representative experiment of 3 is shown.

Mentions: Although blocking basolateral ICAM-1 inhibited transepithelial migration, the effect was not as complete as blocking leukocyte LFA-1 (Fig. 1H; P=0.004), pointing to another epithelial ligand for LFA-1. As well as ICAM-1, LFA-1 can also bind ICAM-2 and ICAM-3, but the expression of ICAM-2 and ICAM-3 is thought to be restricted to hematopoietic cells and endothelium; neither has been found on bronchial epithelium. However, FACS analysis showed that ICAM-2 is expressed by the human bronchial epithelial cell line, 16HBE cells (Fig. 2A), and by primary human lung epithelial cells (Fig. 2B), though these cells do not express ICAM-3 (Fig. 2B). Expression of ICAM-1 is increased by CXCL11 (9), but we found no change in the levels of ICAM-2 under the same conditions (data not shown).


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

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

ICAM-1 and ICAM-2, but not ICAM-3 expression on bronchial epithelial cells. A, B) FACS analysis of ICAM-1 and ICAM-2 expression on 16HBE cells (A) and primary human bronchial epithelial cells (B). Peaks are labeled to their right and show unlabeled epithelial cells, isotype-matched control (anti-CD3), ICAM-1, ICAM-2, and ICAM-3. One experiment representative of 3 similar experiments is shown. LSCM was used to image ICAM-2 staining of a bronchial epithelial monolayer grown on a filter. (MAb to ICAM-2 was presented on both sides of the monolayer). C) The cartoon demonstrates the position of the serial Z series. D–H′) Monolayers are stained for actin (D–H) and ICAM-2 (D′–H′). Projected Z series of 5 images taken at 0.1-μm intervals are shown for basal (D, D′), middle (E, E′–F, F′), apical (G, G′), and luminal epithelium (H, H′). One representative experiment of 3 is shown.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: ICAM-1 and ICAM-2, but not ICAM-3 expression on bronchial epithelial cells. A, B) FACS analysis of ICAM-1 and ICAM-2 expression on 16HBE cells (A) and primary human bronchial epithelial cells (B). Peaks are labeled to their right and show unlabeled epithelial cells, isotype-matched control (anti-CD3), ICAM-1, ICAM-2, and ICAM-3. One experiment representative of 3 similar experiments is shown. LSCM was used to image ICAM-2 staining of a bronchial epithelial monolayer grown on a filter. (MAb to ICAM-2 was presented on both sides of the monolayer). C) The cartoon demonstrates the position of the serial Z series. D–H′) Monolayers are stained for actin (D–H) and ICAM-2 (D′–H′). Projected Z series of 5 images taken at 0.1-μm intervals are shown for basal (D, D′), middle (E, E′–F, F′), apical (G, G′), and luminal epithelium (H, H′). One representative experiment of 3 is shown.
Mentions: Although blocking basolateral ICAM-1 inhibited transepithelial migration, the effect was not as complete as blocking leukocyte LFA-1 (Fig. 1H; P=0.004), pointing to another epithelial ligand for LFA-1. As well as ICAM-1, LFA-1 can also bind ICAM-2 and ICAM-3, but the expression of ICAM-2 and ICAM-3 is thought to be restricted to hematopoietic cells and endothelium; neither has been found on bronchial epithelium. However, FACS analysis showed that ICAM-2 is expressed by the human bronchial epithelial cell line, 16HBE cells (Fig. 2A), and by primary human lung epithelial cells (Fig. 2B), though these cells do not express ICAM-3 (Fig. 2B). Expression of ICAM-1 is increased by CXCL11 (9), but we found no change in the levels of ICAM-2 under the same conditions (data not shown).

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