Activation of complement by intermediate filaments of glomerular epithelial cells

Glomerular visceral epithelial cells, podocytes, have been shown by immunofluorescence and immunoperoxidase staining methods to bind serum complement (C) components in vitro. Binding of Clq, C4, and C3 was demonstrated and the C4 and C3 binding could be inhibited by EDTA. Thus complement binding had the capacity to cause antibody-independent activation of the "classical" C pathway. The C-binding structures had the same distribution as intermediate filaments (IMFs) of vimentin but not desmin or keratin types. By ultrastructural immunohistochemical staining C3 was observed in association with cytoskeletal IMFs.