Demonstration of leukocyte-immobilizing activity in normal human plasma

The effect of normal human plasma on random migration of polymorphonuclear leukocytes (PMNs) in agarose micro-droplet assay was studied. Plasma, even at a concentration as low as 1%, inhibits leukocyte motility and this immobilizing activity seems to be related to a specific factor which present in human sera and is stable at 56 degrees C for 30 min. The immobilizing effect of heat-inactivated sera was abolished in vitro by indomethacin at a concentration of 0.1 micrograms/ml and it was significantly decreased by anti PGE2 antibody. Spontaneous migration of leukocytes failed to be enhanced by indomethacin (0.1 microgram/ml) alone. Anti-PGE2 alone moderately enhanced PMN motility. Immobilizing activity in human sera decreased 2 hours after indomethacin administration (Indomethacinum CHINOIN, 50 mg orally). No direct enhancing effect of indomethacin on leukocyte motility was shown in vivo. The data indicate a leukocyte-immobilizing activity of human sera. This effect is mediated by prostaglandin production induced by serum factor(s). The factor(s) responsible for the above activity may have a role in regulating leukocyte distribution and motility in vivo.