The objectives of this proposal are to examine and to elucidate, further, the factors and mechanisms involved in the interaction between circulating polymorphonuclear leukocytes (PMN) and the endothelial lining of blood vessels, particularly with respect to those events that occur during the acute inflammatory processes. Many factors have been shown to modulate this interaction such as divalent cations, chemotactic agents and prostaglandins; however, the mechanisms of action have not been elucidated clearly. In many instances, it is not yet known if these findings are relevant to the in vivo situation. In this proposal, we want to examine, in vivo and in vitro, the PMN and endothelium and their interactions with respect to (1) effects of chemotactic agents on endothelium, i.e., mitogenesis and chemotaxis; (2) role of prostaglandins; (3) effect of toxic oxygen products released by stimulated PMN on the viability and integrity of the endothelium; (4) role of the extracellular matrix; (5) ultrastructural and fluorescent localization of chemotactic peptides on endothelium; (6) characterization of the surface of both cells using biochemical and monoclonal antibody techniques; (7) how lipid modulation, in particular cholesterol, may affect the interactions and (8) ultrastructural changes that may occur during the inflammatory process. The experiments will be carried out on an in vitro system consisting of cultured endothelial cells (large vessel and capillary) and PMN from different species and on in vivo systems which have been shown to be easily manipulated for perfusion, observation and isolation - the mesentery and the cremasteric muscle of the mouse and rat. We will attempt to correlate functional properties (adhesion, growth, and chemotaxis) with ultrastructural, biochemical and immunological properties in both the in vitro and in vivo systems. Results of the experiments will lead to a better understanding of the interaction between these two cells and provide a basis for the possible development of a means to modulate the acute inflammatory processes.