Subcellular localization and dynamics of Mac-1 (alpha m beta 2) in human neutrophils

J Clin Invest. 1993 Sep;92(3):1467-76. doi: 10.1172/JCI116724.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Cell Compartmentation
  • Cell Membrane / metabolism
  • Cytoplasmic Granules / metabolism
  • Humans
  • In Vitro Techniques
  • Macrophage-1 Antigen / metabolism*
  • N-Formylmethionine Leucyl-Phenylalanine / pharmacology
  • Neutrophils / metabolism*
  • Neutrophils / ultrastructure
  • Subcellular Fractions / chemistry


  • Macrophage-1 Antigen
  • N-Formylmethionine Leucyl-Phenylalanine