Complement-mediated binding of monocytes to intermediate filaments in vitro.

Area of Science:

• Immunology
• Cell Biology

Background:

• Complement (C) activation is vital in immune responses and cellular debris clearance.
• Cytoskeletal intermediate filaments (IMF) are known to interact with immune components.

Purpose of the Study:

• To develop an in vitro model demonstrating complement-mediated monocyte binding to injured cells.
• To elucidate the role of intermediate filaments in this process.

Main Methods:

• Cultured cells (fibroblasts, endothelial, epithelial) were permeabilized and treated with human serum.
• Immunohistochemistry and electron microscopy were used to analyze complement component binding and monocyte attachment.
• Mononuclear cells were incubated with treated target cells to assess monocyte adhesion.

Main Results:

• Permeabilized cells treated with serum showed binding of C1q, C4, and C3 to IMF.
• Monocytes preferentially attached to serum-treated cells, exhibiting activated morphology and phagocytosis.
• Monocyte attachment was dependent on serum treatment, with a 10:1 ratio compared to controls.

Conclusions:

• Intermediate filaments activate the classical complement pathway, facilitating monocyte binding to injured cells.
• This model highlights a mechanism for macrophage-mediated clearance of damaged cells in inflammatory conditions.
• The findings suggest a role for complement-opsonized IMF in inflammatory responses and cell removal.