Anti-apolipoprotein A-I autoantibody: characterization of monoclonal autoantibodies from patients with systemic lupus erythematosus.
OBJECTIVE
The autoantibody to apolipoprotein A-I (apoA-I), a major constituent of high density lipoproteins (HDL), has been detected in sera of patients with systemic lupus erythematosus (SLE). We established a series of monoclonal anti-apoA-I antibodies (MAAI) from 2 patients with SLE and report the reactivities of MAAI with oxidized HDL, anionic substances, and blood coagulation factors.


METHODS
Peripheral blood B cells from patients with SLE were immortalized by Epstein-Barr virus, and B cells secreting anti-apoA-I antibodies (AAI) were fused with mouse myeloma cells. Six MAAI reactive with human apoA-I in both ELISA and immunoblotting analysis were established. The reactivities of MAAI with HDL, ssDNA and dsDNA, phospholipids such as cardiolipin (CL), and coagulation factors were examined by ELISA.


RESULTS
Although all MAAI bound effectively to apoA-I after the protein had been denatured and transferred to the filter membrane (in immunoblotting analyses), they bound less effectively to apoA-I present in HDL. Both oxidation of HDL in the presence of Mn2+ and an association of apoA-I with autoxidized trilinolein strongly enhanced the binding of MAAI to apoA-I, suggesting that MAAI recognize a defined region of apoA-I, which is exposed upon interacting with oxidatively modified lipids. MAAI showed a functional heterogeneity in their cross-reactivity with self-components: some MAAI were shown to cross-react with anionic substances such as CL and ssDNA, and one MAAI was shown to bind effectively to thrombin.


CONCLUSIONS
We identified a novel family of AAI that shows preferential binding to apoA-I in oxidatively modified HDL. These AAI are composed of antibodies with heterogeneous cross-reactivities to various self-components such as anionic phospholipids, ssDNA, and thrombin.
Abe
H
H
Third Department of Internal Medicine, Tokyo Medical University, Japan. haruoa@aqua.plata.or.jp
Tsuboi
N
N
Suzuki
S
S
Sakuraba
H
H
Takanashi
H
H
Tahara
K
K
Tonozuka
N
N
Hayashi
T
T
Umeda
M
M
D000911:Antibodies, Monoclonal / Q000097:blood / Q000276:immunology*; D016632:Apolipoprotein A-I / Q000276:immunology*; D001323:Autoantibodies / Q000097:blood / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology; D001667:Binding, Competitive / Q000187:drug effects / Q000276:immunology; D002308:Cardiolipins / Q000276:immunology; D003429:Cross Reactions; D004277:DNA, Single-Stranded / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D008077:Lipoproteins, LDL / Q000276:immunology; D008180:Lupus Erythematosus, Systemic / Q000276:immunology*; D010743:Phospholipids / Q000276:immunology; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D013917:Thrombin / Q000276:immunology; D014280:Triglycerides / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D016632:Apolipoprotein A-I; D001323:Autoantibodies; D002308:Cardiolipins; D004277:DNA, Single-Stranded; D008077:Lipoproteins, LDL; D010743:Phospholipids; D010975:Platelet Aggregation Inhibitors; D014280:Triglycerides; C099252:oxidized low density lipoprotein; D013917:Thrombin; C009564:trilinolein