Activation of human blood monocytes by adherence to tissue culture plastic surfaces

Human monocytes, purified by countercurrent centrifugal elutriation, were cultured either in plastic dishes or in Teflon vials to determine if attachment would result in activation. beta-Glucuronidase activity, 5'-nucleotidase activity, plasminogen activator, and superoxide anion generation were measured as markers of monocyte activation. Conditioned media and cell lysates were assayed at 2, 4, 8, and 10 hr and then daily for 6 days. Monocytes cultured in plastic dishes secreted a significantly greater proportion of their beta-glucuronidase into the medium than those cultured in Teflon vials. The activity of 5'-nucleotidase was lower in monocytes cultured in plastic dishes, consistent with greater activation. Cellular plasminogen activator levels and the capacity for superoxide anion generation were enhanced in cells cultured in plastic dishes, relative to monocytes cultured in Teflon vials. These observations indicate that monocyte attachment in plastic surfaces results in their activation, a phenomenon that may influence the nature and interpretation of experimental data derived from cultured adherent monocytes or macrophages.