title: The effects of monocytes on the transendothelial migration of T lymphocytes.
abstract: In vivo cell-mediated immune reactions are characterized by mixtures of monocytes and T cells. The purpose of this study was to investigate the role of monocytes on T-cell migration and induction of endothelial adhesion molecules. The in vitro model consisted of adding peripheral blood mononuclear cells (PBMC), T cells or mixtures of monocytes and T cells, to endothelial cells on a porous membrane and using flow cytometry to distinguish between the monocyte and lymphocyte components. PBMC and PBMC supernatants were highly potent at upregulating intercellular adhesion molecule-1 (ICAM-1) and inducing expression of vascular cell adhesion molecule-1 (VCAM-1) and E-selectin. Induction by supernatants was inhibited by antibodies to tumour necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL)-1 beta. Using monocyte-enriched populations, as few as one monocyte to 100 endothelial cells was sufficient to upregulate adhesion molecules. Fixed monocytes also induced adhesion molecules and expressed surface-bound cytokines. In contrast, highly purified unstimulated T cells were not found to induce adhesion molecules at 4, 6, 24 or 48 hr of coculture. Purified T cells showed low-level migration through resting (VCAM-1 negative) endothelium, which was approximately doubled by addition of small numbers of monocytes or TNF-alpha. In conclusion, monocytes, via cell surface or released cytokines play an essential role in allowing large-scale recruitment of T cells to inflammatory sites in vivo.
authors.affiliation: Division of Cardiothoracic Surgery, National Heart and Lung Institute, Imperial College of Science, Technology and Medicine, Harefield Hospital, Middlesex, UK.
authors.forename: E A
authors.initials: EA
authors.lastname: Lidington
authors.forename: A M
authors.initials: AM
authors.lastname: McCormack
authors.forename: M H
authors.initials: MH
authors.lastname: Yacoub
authors.forename: M L
authors.initials: ML
authors.lastname: Rose
mesh_terms: D015496:CD4-Positive T-Lymphocytes / Q000502:physiology; D018414:CD8-Positive T-Lymphocytes / Q000502:physiology; D002450:Cell Communication / Q000276:immunology; D018929:Cell Culture Techniques; D002465:Cell Movement / Q000276:immunology; D019040:E-Selectin / Q000378:metabolism; D004730:Endothelium, Vascular / Q000276:immunology*; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D007375:Interleukin-1 / Q000378:metabolism; D009000:Monocytes / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D015854:Up-Regulation / Q000276:immunology; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism
chemical_list: D019040:E-Selectin; D007375:Interleukin-1; D014409:Tumor Necrosis Factor-alpha; D019010:Vascular Cell Adhesion Molecule-1; D018799:Intercellular Adhesion Molecule-1