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Updated: Sep 20, 2026
Culture of Macrophage Colony-stimulating Factor Differentiated Human Monocyte-derived Macrophages
Published on: June 30, 2016
Differential requirements for cellular cytoskeleton in human macrophage complement receptor- and Fc receptor-mediated
S L Newman1, L K Mikus, M A Tucci
1Department of Internal Medicine, University of Cincinnati College of Medicine, OH 45267.
Abstract:
We investigated the requirement for cellular cytoskeleton in CR- and FcR-mediated phagocytosis by human monocyte-derived macrophages (M phi). Inhibition of actin microfilament (MF) assembly and stability by cytochalasins B and D completely inhibited M phi phagocytosis of sheep E coated with C3b (EC3b), iC3b (EC3bi), and IgG (EIgG) via CR1, CR3, and FcR, respectively. Ligand-binding to either CR or FcR was not effected by cytochalasins. Nocodazole (NOC), which prevents microtubule (MT) polymerization, and taxol, which causes random polymerization of MT inhibited M phi phagocytosis of EC3b(i) but not EIgG. However, the combination of taxol (5 x 10(-4) M) and NOC (2 x 10(-6) M) augmented M phi CR-mediated phagocytosis. In addition, agents known to increase intracellular cGMP augmented phagocytosis of EC3b(i). Conversely, agents that increase intracellular cAMP inhibited CR-mediated phagocytosis. These agents had no effect on FcR-mediated phagocytosis, and did not effect ligand-binding to CR or FcR. PMA markedly enhanced CR- but not FcR-mediated phagocytosis, and augmentation of CR-mediated phagocytosis by PMA was inhibited by both CD and NOC. In contrast, the synthetic diacylglycerol, 1-oleoyl-2-acetoyl-sn-3-glycerol augmented, and inhibitors of protein kinase C inhibited M phi phagocytosis via CR and FcR. These data indicate that for adherently cultured human M phi: 1) binding of ligand-coated E to CR or FcR does not require an intact cytoskeleton; 2) intact actin microfilament are required for phagocytosis via CR and FcR; 3) phagocytosis via CR1 and CR3 but not FcR is dependent on MT assembly; 4) PMA most likely augments CR-mediated phagocytosis through promotion of MT assembly; and 5) PKC activity is involved in the phagocytic signal generated by both CR and FcR.
Insights
The cytoskeleton, particularly actin microfilaments, is essential for macrophage phagocytosis via complement and Fc receptors. Microtubules are crucial for complement receptor-mediated uptake, but not Fc receptor-mediated uptake.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Phagocytosis is a critical cellular process mediated by receptors like complement receptors (CR) and Fc receptors (FcR) on macrophages.
- The role of the cellular cytoskeleton, including actin microfilaments and microtubules, in regulating these phagocytic pathways is not fully elucidated.
Purpose of the Study:
- To investigate the specific requirements of the actin microfilament and microtubule cytoskeleton for complement receptor (CR)- and Fc receptor (FcR)-mediated phagocytosis by human monocyte-derived macrophages.
Main Methods:
- Human monocyte-derived macrophages were cultured and treated with various agents to inhibit or modulate actin microfilament and microtubule assembly.
- Phagocytosis assays were performed using sheep erythrocytes coated with C3b (EC3b), iC3b (EC3bi), or IgG (EIgG) to assess CR- and FcR-mediated uptake.
- Ligand binding to CR and FcR was evaluated independently of phagocytosis.
Main Results:
- Inhibition of actin microfilament assembly completely abolished phagocytosis via CR and FcR, without affecting ligand binding.
- Microtubule disruption inhibited CR-mediated phagocytosis of EC3b(i) but not FcR-mediated phagocytosis of EIgG.
- Modulation of intracellular cGMP and cAMP levels, as well as protein kinase C (PKC) activity, differentially affected CR- and FcR-mediated phagocytosis.
Conclusions:
- Intact actin microfilaments are indispensable for both CR- and FcR-mediated phagocytosis in human macrophages.
- Microtubule assembly is specifically required for CR-mediated phagocytosis, but not FcR-mediated phagocytosis.
- PKC signaling plays a role in the phagocytic pathways initiated by both CR and FcR.
