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136 Pages·2003·4.33 MB·English

β
-glycoprotein I
2
Its role in the antiphospholipid syndrome
Bianca C. H. Lutters
Cover illustration: J. Ruitenburg
Printed by: Optima, Rotterdam
ISBN: 90-393-3250-9
β
-glycoprotein I
2
Its role in the antiphospholipid syndrome
β -glycoprotein I
2
De rol in het antifosfolipiden syndroom
(met een samenvatting in het Nederlands)
Proefschrift
ter verkrijging van de graad van doctor aan de
Universiteit van Utrecht op gezag van de Rector Magnificus,
Prof. Dr. WH Gispen, in gevolge het besluit van het
College voor Promoties in het openbaar te verdedigen
op dinsdag 4 februari 2003 des middags te 14.30 uur
door
Bianca Catharina Henrica Lutters
geboren op 18 januari 1976, te Weert
Promotoren: Prof. Dr. J.W.J. Bijlsma
Faculteit Geneeskunde, Universiteit Utrecht
Prof. Dr. Ph. G. de Groot
Faculteit Geneeskunde, Universiteit Utrecht
Co-promotor: Dr. R.H.W.M. Derksen
Faculteit Geneeskunde, Universiteit Utrecht
The study described in this thesis was supported by a grant of the Netherlands Heart Foun-
dation (NHF-98.060).
Financial support by the Netherlands Heart Foundation for the publication of this thesis was
gratefully acknowledged.
Additional financial support for the publication of this thesis by Dr. Ir. van de Laar Stichting,
Sanofi-Synthelabo B.V., Pharmacia B.V., and NODIA B.V. is gratefully acknowledged.
Aan Rutger
Aan mijn ouders

Contents
Abbreviations
Chapter 1 General introduction 9
Chapter 2 β-glycoprotein I – a key player in the antiphospholipid syndrome – 29
2
Israelian Medical Association Journal; 4(suppl), 958-962,
2002
Chapter 3 Dimers of β -glycoprotein I mimic the in vitro effects of β- 43
2 2
glycoprotein I-anti-β-glycoprotein I antibody complexes.
2
Journal of Biological Chemistry 276, 3060-3067, 2001
Chapter 4 An explanation for arterial thrombosis in the antiphospholipid 63
syndrome: Dimers of β-glycoprotein I increase platelet deposition
2
to collagen via interaction with phospholipids and a cellular receptor.
Chapter 5 Comparison of the effects of anti-β-glycoprotein I and anti- 83
2
prothrombin antibodies on platelet depostion in an in vitro flow
system.
Chapter 6 Anti-β-glycoprotein I antibodies do not affect platelet aggregation. 97
2
Chapter 7 Binding of β-glycoprotein I and dimers of β-glycoprotein I to 101
2 2
members of the low-density lipoprotein receptor superfamily:
implications for the antiphospholipid syndrome.
Chapter 8 General discussion 115
Nederlandse samenvatting 127
Dankwoord 133
Curriculum Vitae 136
Abbreviations
βGPI β-glycoprotein I LRP LDL receptor-related protein
2 2
aCL anticardiolipin antibodies NO nitric oxide
ADP adenosine 5’-diphosphate OPD o-phenylene diamine
ANOVA analysis of variance PAI plasminogen activator inhibitor
APC activated protein C PAPS primary antiphospholipid syndrome
aPL antiphosphospholipid antibodies PBS phosphate-buffered saline
ApoER2 apolipoprotein E receptor-2 PC phosphatidylcholine
APS antiphospholipid syndrome PE phosphatidylethanolamine
aPTT activated partial thromboplastin time PoAb polyconal antibody
AT anti-thrombin PPD para-phenylene diamine
BCA bichinchoninic acid PRP platelet-rich plasma
BSA bovine serum albumine PS phosphatidyl serine
C4BP C4b-binding protein PT prothrombin time
CCP complement control protein RAMPO peroxidase-labeled rabbit-anti-mouse
CI-M6PR cation-independent mannose-6-phosphate antibody
receptor RAP receptor-associated protein
dPT dilute prothrombin time SAPS secondary antiphospholipid syndrome
dRVVT dilute Russell’s viper venom time SCR short consensus repeat
EGF epidermal growth factor SD standard deviation
ELISA enzyme-linked immunosorbent assay SDS-PAGE SDS-polyacrylamide gel electrophoresis
EPCR endothelial cell protein C receptor SLE systemic lupus erythematosus
ER endoplasmic reticulum SPR surface plasmon resonance
FCS fetal calf serum TAFI thrombin activatable fibrinolysis
FII prothrombin inhibitor
FITC fluorescein isothiocyanate TBS tris-buffered saline
Gla γ-carboxyglutamic acid TF tissue factor
GPIb glycoprotein Ib TFPI tissue factor pathway inhibitor
GPVI glycoprotein VI tPA tissue-type plasminogen activator
HMWK high molecular weight kininogen TRITC tetramethyl rhodamine isothiocyanate
HUVEC human umbilical vein endothelial cell TxA thromboxane A
2 2
KCT kaolin clotting time TxB thromboxane B
2 2
LAC lupus anticoagulant uPA urinary-type plasminogen activator
LDL low-density lipoprotein VLDL very-low-density lipoprotein
LMWH low molecular weight heparin vWF von Willebrand factor
Chapter 1 General introduction
1
9
The antiphospholipid syndrome
The term ‘antiphospholipid syndrome’ (APS) refers to patients with arterial or venous
thrombosis, pregnancy loss, and thrombocytopenia, in which so-called antiphospholipid
antibodies (aPL) are repeatedly detected in their plasmas. The antiphospholipid syndrome
was originally described in patients with systemic lupus erythematosus (SLE), a systemic
autoimmune disorder. The association between SLE with APS is called secondary
antiphospholipid syndrome (SAPS). Over the years, APS in the absence of an underlying
autoimmune disease has been recognized in many more patients (defined as primary
antiphospholipid syndrome (PAPS)).
The antiphospholipid antibodies can be detected in an enzyme-linked immuno-
sorbent assay (ELISA) and in in vitro coagulation assays. Traditionally, antibodies against
the anionic phospholipid cardiolipin (aCL) are detected by ELISA. Using in vitro coagulation
assays, antibodies are detected by their ability to prolong phospholipid-dependent clotting
assays. These antibodies are termed lupus anticoagulants (LAC).
Historical background
10
The history of antiphospholipid antibodies started about 50 years ago with the
observation that some SLE patients showed a biologically false-positive tests for syphilis,
without having syphilis 1-3. Positive reactions were found in tests, such as the VDRL-
flocculation test, in which the main antigen is a phospholipid that could be extracted from
beef heart, and therefore was named cardiolipin 4. In a large retrospective study of these
biologically false-positive plasmas, a group with a transient false positive reaction and a
group with a chronic false positive reaction were defined 1. In this latter group, the incidence
of autoimmune disorders, notably SLE, was high, whereas transient positive reactions related
to infectious diseases. These chronic false positive reactors are at present known as auto-
immune anticardiolipin antibodies.
In 1952, a peculiar circulating anticoagulant was described in two SLE patients. This
anticoagulant was able to prolong the prothrombin time, even when the plasma was diluted
with normal plasma to correct for coagulation factor defiencies 5. Surprisingly, it was not
associated with a bleeding tendency. This anticoagulant was mainly found in SLE patients
and therefore termed lupus anticoagulant 6. Later, it became clear that lupus anticoagulant
was not restricted to SLE patients alone, but that it was also found in association with certain
drugs, infections, malignancies, and even in healthy individuals 7-10. However, the name
lupus anticoagulant is still in general use. The clinical importance of anticardiolipin and LAC-
inducing antiphospholipid antibodies only became clear in the 1980s, when it was
demonstrated that the presence of LAC is associated with thrombosis, thrombocytopenia
and fetal loss 11.
In 1988, it became evident that anticardiolipin antibodies and antibodies with LAC
activity are not necessarily the same antibodies, as was demonstrated by separating both
types of antibodies from a single plasma 12-14.