Abstract
Increased adherence to and subsequent migration of leukocytes across cultured human peritoneal mesothelial cell monolayers takes place after pretreatment of the mesothelial cells with interleukin-1 β. The contribution of the leukocyte β 2 integrins (CD11/CD18) and the mesothelial adhesion protein intercellular adhesion molecule-1 (ICAM-1) and the role of the cytokines interleukin-8, platelet-activating factor (PAF), and transforming growth factor- β (TGF- β) were studied in a three-dimensional model system for neutrophil-mesothelial monolayer interaction. Polymorphonuclear leukocytes (PMNs) showed minimal adherence to and migration across unactivated mesothelial monolayers, despite an extensive amount of ICAM-1 on the mesothelial membrane. Pretreatment of the monolayers with rIL-1 β induced enhanced PMN adherence to the mesothelial monolayer together with a further increase in ICAM-1 expression on the mesothelial membrane. PMN migration was observed across rIL-1 β- activoted mesothelial cell (MC) monolayers whenever cytokines secreted by the MCs were present during migration. Monoclonal antibody (mAb) R6.5 against ICAM-1 and mAb CLB-LFA1/1 against CD18 both reduced the migration of PMNs across mesothelial monolayers with a predominant inhibitory effect of CLBLFA1/1, indicating a significant role of the β 2 integrins of PMNs in this process. Interleukin-8 was the major cytokine synthesized by the MCs to stimulate the migration of PMNs; both PAF and TGF- β had a more modest role in our system. Adherence of PMNs to MC monolayers was not dependent on these latter cytokines. Neuraminidase did not have any effect, indicating that selectins were not involved in the adherence process. rIL-1 β-pretreated MCs induced a rapid increase in intracellular Ca 2+ in PMNs; actinomycin D blocked this effect and was also able to prevent adhesion of neutrophils to activated MC monolayers. Neutrophil migration across activated cultured MCs is thus a cascade of events in which the MCs are actively involved.
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