Differences in the mode of phagocytosis with Fc and C3 receptors in macrophages

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Published on: August 26, 2016

G Kaplan

    Scandinavian Journal of Immunology
    |January 1, 1977
    PubMed

    Insights

    Macrophages internalize antibody-coated (IgG) or complement-coated (IgM) sheep red blood cells (Erythrocytes) using distinct mechanisms. Fc receptor-mediated phagocytosis involves membrane extensions, while C3 receptor uptake is more direct, with microfilaments crucial for Fc-mediated processes.

    Area of Science:

    • Immunology
    • Cell Biology
    • Microscopy

    Background:

    • Macrophages are key immune cells involved in phagocytosis.
    • Internalization of opsonized particles is mediated by Fc and complement receptors.
    • Distinct mechanisms may exist for Fc and complement receptor-mediated phagocytosis.

    Purpose of the Study:

    • To investigate the distinct mechanisms of macrophage internalization of IgG-opsonized and IgM-complement-opsonized erythrocytes.
    • To characterize the role of macrophage receptors and cytoskeletal elements in phagocytosis.

    Main Methods:

    • In vitro and in vivo activation of mouse macrophages.
    • Internalization assays using sheep erythrocytes opsonized with IgG or IgM and complement.
    • Scanning and transmission electron microscopy for ultrastructural analysis.
    • Phagocytosis inhibition studies using cytochalasin B.

    Main Results:

    • Fc receptors were more abundant at the macrophage periphery.
    • IgG-opsonized erythrocytes were ingested via cup-like membrane extensions, followed by internalization.
    • IgM-complement-opsonized erythrocytes were internalized directly into the cytoplasm.
    • Microfilaments were essential for Fc-mediated phagocytosis but less so for C3 receptor-mediated uptake.

    Conclusions:

    • Macrophage phagocytosis of IgG-opsonized and IgM-complement-opsonized erythrocytes occurs via distinct pathways.
    • Fc receptor-mediated phagocytosis involves actin-dependent membrane remodeling.
    • C3 receptor-mediated phagocytosis is less dependent on microfilaments.

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