We demonstrate an additional step and a positive feedback loop in leukocyte accumulation on inflamed endothelium. Leukocytes in shear flow bind to adherent leukocytes through L-selectin/ligand interactions and subsequently bind downstream and roll on inflamed endothelium, purified E-selectin, P-selectin, L-selectin, VCAM-1, or peripheral node addressin. Thus adherent leukocytes nucleate formation of strings of rolling cells and synergistically enhance leukocyte accumulation. Neutrophils, monocytes, and activated T cell lines, but not peripheral blood T lymphocytes, tether to each other through L-selectin. L-selectin is not involved in direct binding to either E- or P-selectin and is not a major counterreceptor of endothelial selectins. Leukocyte-leukocyte tethers are more tolerant to high shear than direct tethers to endothelial selectins and, like other L-selectin-mediated interactions, require a shear threshold. Synergism between leukocyte-leukocyte and leukocyte-endothelial interactions introduces novel regulatory mechanisms in recruitment of leukocytes in inflammation.
Interactions through L-selectin between leukocytes and adherent leukocytes nucleate rolling adhesions on selectins and VCAM-1 in shear flow.
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R Alon, R C Fuhlbrigge, E B Finger, T A Springer; Interactions through L-selectin between leukocytes and adherent leukocytes nucleate rolling adhesions on selectins and VCAM-1 in shear flow.. J Cell Biol 1 November 1996; 135 (3): 849–865. doi: https://doi.org/10.1083/jcb.135.3.849
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