Endothelial cell-binding activity of anti-U1-ribonucleoprotein antibodies in patients with connective tissue diseases.
In order to elucidate the immunological properties of anti-U1-ribonucleoprotein (RNP) antibody, one of the autoantibodies detected in patients with connective tissue diseases (CTDs), we tested the endothelial cell-binding by anti-U1-RNP antibodies and epitopes on human pulmonary artery endothelial cells (HPAECs) to which the autoantibody bound. IgG fractions positive for anti-U1-RNP from patients with CTDs bound to the HPAECs. Furthermore, intact and F(ab')2 IgG anti-U1-RNP purified by affinity chromatography also bound to endothelial cells. The binding activity of IgG fractions positive for anti-U1-RNP to the endothelial cells could be effectively absorbed by U1-RNP-Sepharose. An immunoblotting assay of purified IgG anti-U1-RNP antibodies showed that these antibodies could bind to various membrane proteins of NP40-treated HPAECs such as 68, 48, 43, 38, 33, 29, 28 and 24 kDa. Some bands, 68, 33, 28 and 24 kDa, seemed to correspond to components of U1-RNP, i.e. 68 kDa, A, B' and C peptides, respectively. We confirmed that the anti-U1-RNP antibody from patients with CTDs can directly recognize a variety of antigens on the endothelial surface of the pulmonary artery, including the components of U1-RNP or other unknown polypeptides. These results suggest that binding to pulmonary artery endothelial cells of this autoantibody may be one of the triggers of endothelial cell inflammation in CTDs.
Okawa-Takatsuji
M
M
Division of Clinical Immunology, Research Institute, International Medical Center of Japan, Tokyo, Japan. okawat@ri.imcj.go.jp
Aotsuka
S
S
Uwatoko
S
S
Takaono
M
M
Iwasaki
K
K
Kinoshita
M
M
Sumiya
M
M
D000818:Animals; D001323:Autoantibodies / Q000097:blood / Q000378:metabolism*; D001324:Autoantigens; D001665:Binding Sites; D016022:Case-Control Studies; D002478:Cells, Cultured; D003240:Connective Tissue Diseases / Q000276:immunology*; D003429:Cross Reactions; D004730:Endothelium, Vascular / Q000276:immunology*; D007140:Immunoglobulin Fab Fragments / Q000097:blood / Q000378:metabolism; D007074:Immunoglobulin G / Q000097:blood / Q000378:metabolism; D066298:In Vitro Techniques; D007249:Inflammation / Q000209:etiology; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000276:immunology*
D001323:Autoantibodies; D001324:Autoantigens; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D017412:Ribonucleoprotein, U1 Small Nuclear