NEUTROPHIL ADHERENCE TO AND MIGRATION ACROSS MONOLAYERS OF HUMAN PERITONEAL MESOTHELIAL CELLS - THE ROLE OF MESOTHELIUM IN THE INFLUX OF NEUTROPHILS DURING PERITONITIS

Increased adherence to and subsequent migration of leukocytes across c ultured human peritoneal mesothelial cell monolayers takes place after pretreatment of the mesothelial cells with interleukin-l beta. The co ntribution of the leukocyte beta(2) integrins (CD11/CD18) and the meso thelial adhesion protein inter-cellular adhesion molecule-1 (ICAM-1) a nd the role of the cytokines interleukin-8, platelet-activating factor (PAF), and transforming growth factor-beta (TGF-beta) were studied in a three-dimensional model system for neutrophil-mesothelial monolayer interaction. Polymorphonuclear leukocytes (PMNs) showed minimal adher ence to and migration across unactivated mesothelial monolayers, despi te an extensive amount of ICAM-1 on the mesothelial membrane. Pretreat ment of the monolayers with rlL-1 beta 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 a cross rlL-1 beta-activated mesothelial cell (MC) monolayers whenever c ytokines secreted by the MCs were present during migration. Monoclonal antibody (mAb) R6.5 against ICAM-1 and mAb CLB-LFA1/1 against CD18 bo th reduced the migration of PMNs across mesothelial monolayers with a predominant inhibitory effect of CLB-LFA1/1, indicating a significant role of the beta(2) integrins of PMNs in this process. Interleukin-8 w as the major cytokine synthesized by the MCs to stimulate the migratio n of PMNs; both PAF and TGF-beta 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 sele ctins were not involved in the adherence process. rlL-1 beta-pretreate d MCs induced a rapid increase in intracellular Ca2+ in PMNs; actinomy cin D blocked this effect and was also able to prevent adhesion of neu trophils to activated MC monolayers. Neutrophil migration across activ ated cultured MCs is thus a cascade of events in which the MCs are act ively involved.