Anti-endothelial cell antibodies from lupus patients bind to apoptotic endothelial cells promoting macrophage phagocytosis but do not induce apoptosis.

Abstract

OBJECTIVE:

Anti-endothelial cell antibodies (AECA) have been reported to induce apoptosis. We investigated the induction of apoptosis by these autoantibodies and their involvement in the removal of apoptotic cells.

METHODS:

AECA isolated from patients with active systemic lupus erythematosus (SLE) were incubated with human umbilical vein endothelial cells (HUVECs). AECA-positive sera were identified using a cell-based ELISA. Apoptosis was measured by morphology and phosphatidylserine externalization using flow cytometry with fluorescein isothiocyanate (FITC)-conjugated annexin V. Flow cytometry was used to investigate AECA binding to apoptotic cells using FITC-conjugated anti-human immunoglobulin G (IgG). Apoptotic endothelial cells were stained with a red dye (PKH26) and co-cultured with macrophages, and phagocytosis was visualized under phase contrast microscopy.

RESULTS:

AECA from patients with SLE did not induce apoptosis compared with normal IgG (nIgG) at any time point, as assessed by morphology (at 24 h, P = 0.167) or phosphatidylserine externalization (at 24 h, P = 0.098). However, there was increased binding of AECA to apoptotic endothelial cells (48.8 +/- 11.9 compared with 25.8 +/- 6.7% AECA binding to freshly isolated cells, P< 0.001). These opsonized endothelial cells showed greater phagocytosis by macrophages (mean phagocytic index 24.9 +/- 4.5%) when cells opsonized with nIgG were compared with AECA (34.8 +/- 3.4% n = 5, P = 0.01).

CONCLUSION:

In conclusion, AECA bind to apoptotic endothelial cells but do not induce endothelial cell apoptosis. Macrophage phagocytosis is increased by opsonization of apoptotic endothelial cells by AECA, a proinflammatory mechanism of cell removal.

• Authors: J M Williams, R Colman, C J Brookes, C O Savage, L Harper
• Journal: Rheumatology (Oxford, England) (Rheumatology (Oxford)) Vol. 44 Issue 7 Pg. 879-84 (Jul 2005) ISSN: 1462-0324 [Print] England
• PMID: 15827042 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Autoantibodies
• Immunoglobulin G
• anti-endothelial cell antibody

Topics

• Adolescent
• Adult
• Apoptosis (immunology)
• Autoantibodies (immunology)
• Cells, Cultured
• Coculture Techniques
• Dose-Response Relationship, Immunologic
• Endothelial Cells (immunology)
• Enzyme-Linked Immunosorbent Assay (methods)
• Female
• Humans
• Immunoglobulin G (immunology)
• Lupus Erythematosus, Systemic (immunology)
• Macrophages (immunology)
• Male
• Microscopy, Phase-Contrast
• Middle Aged
• Phagocytosis (immunology)