Natural immune response involving anti-endothelial cell antibodies in normal and lupus pregnancy

Detection of Antibodies In Vitro Binding to Endothelial Cells in the Sera from Women with Normal Pregnancy and Preeclampsia

Activity of serum antibodies in vitro binding to endothelial cells in women with normal pregnancy and preeclampsia was studied. Flow cytometry detected peculiarities of antibody binding to endothelial cells in health and disease. Detection of antiendothelial antibodies in trimesters II and III can be diagnostically important in preeclampsia.

Antiendothelial cells autoantibodies in vasculitis-associated systemic diseases

Antiendothelial cell antibodies (AECA) have been detected in healthy individuals, as well as in autoimmune and systemic inflammatory diseases, including systemic vasculitides. AECA have been reported in large vessel vasculitides such as giant cell arteritis and Takayasu arteritis; medium-sized vessel vasculitides, such as polyarteritis nodosa related to hepatitis B virus infection and Kawasaki disease; and small-sized vessel vasculitides, such as Wegener's granulomatosis, microscopic polyangiitis, and Henoch-Schonlein purpura. In Takayasu arteritis and antineutrophil cytoplasm antibody-positive vasculitides, AECA have been reported to correlate with disease activity. A cell-based enzyme-linked immunosorbent assay (ELISA) using cultured human umbilical vein endothelial cells (HUVEC) represent one of the reference techniques for AECA detection, although flow cytometry and immunobloting have also been proposed. AECA might contribute to the pathogenesis of systemic vasculitides and vasculitis-associated diseases through (1) activation of endothelial cells (EC), (2) direct cytotoxic effect due to complement-dependent cytotoxicity or indirect cytotoxic effect secondary to antibody-dependent cytotoxicity, (3) induction of coagulation, (4) induction of apoptosis through the binding of phospholipids or heat-shock protein 60, and (5) induction of EC activation. None of the identified target antigens of AECA is specific for EC, and EC-specific target antigens of AECA remain to be identified in systemic vasculitides.

Identification of target antigens of antiendothelial cell antibodies in healthy individuals: A proteomic approach

In order to identify target antigens of anti-endothelial cell (anti-EC) antibodies (AECA) in healthy individuals, we have used a proteomic approach combining 2-DE and immunoblotting. Whole cell protein extracts obtained from human umbilical vein EC (HUVEC) cultures were used as a source of antigens. Serum IgG from 12 healthy blood donors were tested at a concentration of 200 microg/mL. Targeted spots were identified by MS. The HUVEC proteome was composed of 884 protein spots. Among these, 61 +/- 25.8 (mean +/- SD) spots were recognized by serum IgG from healthy individuals, with marked differences from one individual to another. Among these spots, 11 were recognized by serum IgG from all healthy individuals tested. These spots corresponded to six different proteins with several spots corresponding to different isoforms of the same protein. Target antigens were: cytoskeletal proteins (beta-actin, alpha-tubulin, and vimentin); glycolytic enzymes (glucose-3-phosphate-deshydrogenase and alpha-enolase); and prolyl-4-hydroxylase beta subunit, a member of the disulfide isomerase family. This study shows that the repertoire of IgG AECA is heterogeneous among healthy individuals. IgG from all of the healthy individuals tested recognized a restricted set of highly conserved ubiquitous proteins playing key roles in cell biology and maintenance of homeostasis.

Natural anti-endothelial cell antibodies

Anti-endothelial cell antibodies (AECA) are detectable in a heterogenous group of autoimmune and inflammatory conditions. These antibodies have also been detected in healthy individuals. Nevertheless, most of the literature focuses on AECA in pathological conditions and their targets and functions in healthy individuals remain to be clarified. Recently, proteome-based technologies have been successfully used for the identification of antigens targeted by natural AECA. Thus, it has been shown that IgG AECA can be detected in sera from healthy individuals that recognize a restricted set of proteins among a whole protein extract of umbilical vein endothelial cells. These proteins correspond to ubiquitous proteins belonging to highly conserved protein families and exerting pivotal roles in cell physiology, including cytoskeletal proteins (beta actin, vimentin, alpha tubulin) and glycolytic enzymes (glyceraldehyde-3-phosphate-deshydrogenase and alpha-enolase). As reported for other types of natural autoantibodies, natural AECA could exert anti-inflammatory and anti-thrombotic functions. In addition, they could play a role in the control of EC activation.

Pathogenic mechanisms of anti-endothelial cell antibodies (AECA): their prevalence and clinical relevance

Anti‐endothelial cell antibodies (AECA) represent a heterogeneous family of autoantibodies directed against structural endothelial proteins, as well as antigens adhering to endothelial cells. Although AECA immunoassays still show a high‐interlaboratory variability, several findings suggest a pathogenic role of these autoantibodies in diseases characterized by endothelial damage. In this chapter, we analyze the knowledge about AECA prevalence, clinical relevance, and their pathogenic role in autoimmune diseases focusing in particular on systemic lupus erythematosus, antiphospholipid syndrome, systemic sclerosis (SSc), and systemic vasculitis.