title: Endocytosis of beta 2 integrins by stimulated human neutrophils analyzed by flow cytometry.
abstract: Flow cytometry and fluorescently labeled monoclonal antibodies were used to investigate endocytosis of human neutrophil beta 2 integrins following cellular activation. CD18 initially present on the cell surface cycled in two phases after exposure to formyl peptide or platelet-activating factor. The first phase lasted 3 min at 37 degrees C; after a lag, CD18 was specifically internalized at approximately 20%/min. Subsequently a second phase was detectable consisting of exponential reduction of internal fluorescence with a half-time of approximately 2 min, representing probe reexpression. At peak endocytosis approximately 40% of CD18 was internalized. All of the internalized CD18 was associated with alpha M (CR3); no endocytosis of alpha L (LFA-1) was observed. When neutrophils were stimulated with phorbol esters or calcium ionophore, CD18 was internalized much more slowly (t1/2 = 5 min) and probe was not reexpressed. Endocytosis of CD18 may participate in regulating neutrophil adhesiveness, removing activated receptors, or permitting receptor recycling.
authors.affiliation: La Jolla Institute for Experimental Medicine, California 92037.
authors.forename: J D
authors.initials: JD
authors.lastname: Chambers
authors.forename: S I
authors.initials: SI
authors.lastname: Simon
authors.forename: E M
authors.initials: EM
authors.lastname: Berger
authors.forename: L A
authors.initials: LA
authors.lastname: Sklar
authors.forename: K E
authors.initials: KE
authors.lastname: Arfors
mesh_terms: D000911:Antibodies, Monoclonal; D015703:Antigens, CD / Q000032:analysis; D018821:CD18 Antigens; D004705:Endocytosis / Q000187:drug effects; D005434:Flow Cytometry; D006801:Humans; D007140:Immunoglobulin Fab Fragments; D066298:In Vitro Techniques; D016023:Integrins / Q000378:metabolism*; D007700:Kinetics; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects / Q000502:physiology*; D016028:Receptors, Leukocyte-Adhesion / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018821:CD18 Antigens; D007140:Immunoglobulin Fab Fragments; D016023:Integrins; D016169:Lymphocyte Function-Associated Antigen-1; D016028:Receptors, Leukocyte-Adhesion; D009240:N-Formylmethionine Leucyl-Phenylalanine