Specialization of the macrophage plasma membrane at sites of interaction with opsonized erythrocytes.
We incubated mouse peritoneal macrophages for 3-8 min at 37 degrees C with antibody-coated sheep erythrocytes and examined regions of close interaction between the two cell types by electron microscopy. At sites of focal macrophage-erythrocyte contact we observed a distinctive specialization of the macrophage plasma membrane consisting of a prominent subplasmalemmal band of electron-dense material, approximately 25-35 nm in thickness. In many instances, this band showed a periodic substructure similar to that seen in clathrin coats. Moreover, many slender erythrocyte processes penetrated into invaginations of the macrophage surface which were bristle-coated at their blind extremity. As previously shown for clathrin-coated pits, the segments of the macrophage plasma membrane beneath which the defense material was found were selectively resistant to the membrane-perturbing effect of the antibiotic, filipin. This structural specialization of the macrophage plasma membrane at sites of ligand-receptor interaction during immune phagocytosis of antibody-coated erythrocytes may represent the morphological counterpart of the zipper mechanism of phagocytosis previously demonstrated by functional studies.
D000818:Animals; D002450:Cell Communication; D002462:Cell Membrane / Q000648:ultrastructure*; D004912:Erythrocytes / Q000166:cytology*; D008264:Macrophages / Q000276:immunology / Q000648:ultrastructure*; D051379:Mice; D008807:Mice, Inbred BALB C; D008854:Microscopy, Electron; D010587:Phagocytosis; D012756:Sheep