Mechanism of CD11b down-regulation from phorbol myristate acetate stimulated polymorphonuclear neutrophils.

Objective: To investigate the mechanism of CD11b down-regulation in phorbol myristate acetate (PMA) stimulated polymorphonuclear leukocytes (PMN).

Methods: Purified PMN were stimulated with PMA in the presence, or absence, of various enzyme inhibitors. Following stimulation, PMN CD11b expression was examined by flow cytometry and Western-blotting. The entire work was carried out at Liverpool University between the period of 1998 and 2001.

Results: Stimulation of PMN with PMA induced the down-regulation of CD11b by a mechanism involving a combination of an oxidant and a serine protease; most likely the primary granule derived elastase.

Conclusion: The present study shows for the first time the cooperation of both oxidants and enzymes in the down-regulation of PMN adhesion receptors.