Leukocyte migration inhibition activity of nonimmune acute inflammatory pleural exudate.

Material with leuckocyte migration inhibition (LMI) activity has been demonstrated in various types of nonimmunologically induced acute pleural inflammatory exudates. This activity is present in inflammatory cell-free exudate and appears to involved the deposition of fibrin around the migrating leukocyte, resulting in "cell-trapping." This is supported by the fact that removal or inhibition of fibrin formation leads to loss of exudate LMI activity. Both fibrinogen and complement as well as vitamin K-dependent clotting factors appear to be required for LMI activity. The mechanism involved in the LMI reaction and its significance in nonimmune and cell-mediated immune inflammation are discussed.