Beta-2-glycoprotein specificity of human anti-phospholipid antibody resides on the light chain: a novel mechanism for acquisition of cross-reactivity by an autoantibody.
We have recently shown that the anti-cardiolipin activity of human anti-phospholipid antibody UK4 (lambda) resides on its heavy chain. We now show that UK4 possesses strong reactivity to the plasma-protein beta2-Glycoprotein I (beta2-GPI) also. Utilizing chain shuffling experiments involving an unrelated anti-p185 antibody 4D5 (kappa) with no reactivity to beta2-GPI, we now demonstrate that both the constructs possessing the auto-antibody-derived light chain exhibited significant binding to beta2-GPI. However, the construct possessing UK4 heavy chain in association with 4D5 light chain, exhibited no anti-beta2-GPI activity. Furthermore, there was a low increase (approximately 10%) in the binding of UK4 to cardiolipin in the presence of beta2-GPI. The results demonstrate that anti-beta2-GPI activity resides on UK4 light chain and, importantly, this activity could be transferred to a novel antibody construct via the light chain alone. Computer-generated models of the three-dimensional structures of UK4 and its hybrids, suggest predominant interaction of UK4 light chain with domain IV of beta2-GPI. Molecular docking experiments highlight a number of potential sites on beta2-GPI for interaction of UK4 and indicate as to how beta2-GPI recognition may occur primarily via the autoantibody light chain. The study provides first demonstration of the occurrence of anti-phospholipid and anti-beta2-GPI activities separately on heavy and light chains of an autoantibody. The possible mechanisms that such antibodies may employ to recognise their antigens, are discussed.
Kumar
Sanjeev
S
Department of Medicine, Centre for Rheumatology, Bloomsbury Rheumatology Unit, University College London Hospital, Arthur Stanley House, 40-50 Tottenham Street, London W1P 9PG, UK. sanjeev.kumar@antisoma.com
Nagl
Sylvia
S
Kalsi
Jatinderpal K
JK
Ravirajan
Chelliah T
CT
Athwal
Dee
D
Latchman
David S
DS
Pearl
Laurence H
LH
Isenberg
David A
DA
D017152:Antibodies, Antiphospholipid / Q000276:immunology*; D000918:Antibody Specificity; D001323:Autoantibodies / Q000276:immunology*; D001665:Binding Sites; D003001:Cloning, Molecular; D003429:Cross Reactions / Q000276:immunology*; D006023:Glycoproteins / Q000276:immunology*; D006801:Humans; D007147:Immunoglobulin Light Chains / Q000276:immunology; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D015202:Protein Engineering; D053482:beta 2-Glycoprotein I
D017152:Antibodies, Antiphospholipid; D001323:Autoantibodies; D006023:Glycoproteins; D007147:Immunoglobulin Light Chains; D053482:beta 2-Glycoprotein I