title: Early endocytotic steps in elicited macrophages: omega-shaped plasma membrane vesicles at their cell surface.
abstract: Fluid-phase and receptor-mediated endocytosis were studied in Freund's adjuvant elicited macrophages. These cells were found to bind and internalize significantly larger amounts of peroxidase-antiperoxidase (PAP) immune complex than resident macrophages. Similarly the rate of the fluid-phase uptake was higher in elicited cells. When studying the early steps of endocytotic processes, omega-shaped plasma membrane pits (d approximately 90 nm) were found at the macrophage cell surface. Although occurring occasionally in resident cells, their number was highly increased after elicitation in 30% of the macrophage cell population. The different morphology of these cells coincided with a lower endocytotic activity and a very strong ecto Ca(2+)-ATPase reaction. The present findings indicate that the elicited macrophage population is heterogenous and consists of different subclasses.
authors.affiliation: Laboratory I of Electron Microscopy, Semmelweis University of Medicine, Budapest, Hungary.
authors.forename: A L
authors.initials: AL
authors.lastname: Kiss
authors.forename: A
authors.initials: A
authors.lastname: Kittel
mesh_terms: D000818:Animals; D000936:Antigen-Antibody Complex / Q000502:physiology; D002462:Cell Membrane / Q000502:physiology; D002478:Cells, Cultured; D003594:Cytoplasmic Granules / Q000502:physiology*; D004705:Endocytosis; D005620:Freund's Adjuvant; D017737:Macrophages, Peritoneal / Q000502:physiology* / Q000648:ultrastructure; D008854:Microscopy, Electron; D009195:Peroxidase / Q000276:immunology; D051381:Rats
chemical_list: D000936:Antigen-Antibody Complex; D005620:Freund's Adjuvant; D009195:Peroxidase