DNA topoisomerase I binding to fibroblasts induces monocyte adhesion and activation in the presence of anti-topoisomerase I autoantibodies from systemic sclerosis patients.

Abstract

OBJECTIVE:

Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrosis due to excessive and dysregulated collagen production by fibroblasts. Previously, we reported that anti-DNA topoisomerase I (anti-topo I) antibodies bound specifically to fibroblast surfaces; however, we had not identified their antigenic target. We undertook this study to characterize the target of anti-topo I antibodies on fibroblasts and the effects of their binding.

METHODS:

Purified topo I or topo I released from apoptotic cells was tested for surface binding to a number of human cell types by cell-based enzyme-linked immunosorbent assay, flow cytometry, and indirect immunofluorescence. Antibodies purified from SSc patient and normal control sera were used to detect topo I binding. The consequences of topo I and anti-topo I binding to fibroblasts were assessed by coculture with THP-1 monocytes.

RESULTS:

The autoantigen topo I itself was found to bind specifically to fibroblasts in a dose-dependent and saturable manner, where it was recognized by anti-topo I from SSc patients. The binding of anti-topo I subsequently stimulated adhesion and activation of cocultured monocytes. Topo I released from apoptotic endothelial cells was also found to bind specifically to fibroblasts.

CONCLUSION:

The findings of this study thus confirm and extend the findings of our previous study by showing that topo I binding to fibroblast surfaces is both necessary and sufficient for anti-topo I binding. Second, topo I-anti-topo I complex binding can then trigger the adhesion and activation of monocytes, thus providing a plausible model for the amplification of the fibrogenic cascade in anti-topo I-positive SSc patients.

• Authors: Jill Hénault, Geneviève Robitaille, Jean-Luc Senécal, Yves Raymond
• Journal: Arthritis and rheumatism (Arthritis Rheum) Vol. 54 Issue 3 Pg. 963-73 (Mar 2006) ISSN: 0004-3591 [Print] United States
• PMID: 16508979 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Autoantibodies
• DNA Topoisomerases, Type I

Topics

• Apoptosis
• Autoantibodies (immunology)
• Cell Adhesion (immunology)
• Cells, Cultured
• DNA Topoisomerases, Type I (immunology)
• Electrophoresis
• Enzyme-Linked Immunosorbent Assay
• Fibroblasts (immunology)
• Flow Cytometry
• Fluorescent Antibody Technique
• Humans
• Immunoblotting
• Microscopy, Confocal
• Monocytes (immunology)
• Scleroderma, Systemic (immunology)