@article {528841, title = {Subcellular localization and dynamics of Mac-1 (αMβ2) in human neutrophils}, journal = {J. Clin. Invest.}, volume = {92}, number = {3}, year = {1993}, note = {Reprint Status: In File}, pages = {1467-1476}, abstract = {The subcellular localization of Mac-1 was determined in resting and stimulated human neutrophils after disruption by nitrogen cavitation and fractionation on two-layer Percoll density gradients. Light membranes were further separated by high voltage free flow electrophoresis. Mac-1 was determined by an ELISA with monoclonal antibodies that were specific for the alpha-chain (CD11b). In unstimulated neutrophils, 75\% of Mac-1 colocalized with specific granules including gelatinase granules, 20\% with secretory vesicles and the rest with plasma membranes. Stimulation with nanomolar concentrations of FMLP resulted in the translocation of Mac-1 from secretory vesicles to the plasma membrane, and only minimal translocation from specific granules and gelatinase granules. Stimulation with PMA or Ionomycin resulted in full translocation of Mac-1 from secretory vesicles and gelatinase granules to the plasma membrane, and partial translocation of Mac-1 from specific granules. These findings were corroborated by flow cytometry, which demonstrated a 6-10-fold increase in the surface membrane content of Mac-1 in response to stimulation with FMLP, granulocyte-macrophage colony stimulating factor, IL-8, leukotriene B4, platelet-activating factor, TNF-alpha, and zymosan-activated serum, and a 25-fold increase in response to Ionomycin. Thus, secretory vesicles constitute the most important reservoir of Mac-1 that is incorporated into the plasma membrane during stimulation with inflammatory mediators.}, author = {Sengelov,H. and Kjeldsen,L. and Diamond,M.S. and Springer, T.A. and Borregaard,N.} }