The antiphospholipid-protein syndrome

Antiphospholipid and antioangiogenic activity in females with recurrent miscarriage and antiphospholipid syndrome

Background Antiphospholipid syndrome is an autoimmune disease characterized by thrombosis, fetal losses and thrombocytopenia associated to antiphospholipid antibodies. They are directed to phospholipids, such as cardiolipins (anticardiolipin) and lupus anticoagulant or to complexes formed by phospholipids and protein cofactors, such as β2 glycoprotein 1 (a-β2GP1) and annexin V (a-annexin V). These auto-antibodies may be considered as a family of antibodies involved in thrombotic events and antiphospholipid activity. On the other hand, some proangiogenic factors are involved in the normal development of placental vasculature, such as the vascular endothelial growth factor. Overexpression of vascular endothelial growth factor receptor in its soluble form (sVEGFR-1) has been associated to a higher antiangiogenic activity. Our aim was to analyse the association between anticardiolipin, lupus anticoagulant, a-β2GP1, a-annexin V and sVEGFR-1 with recurrent miscarriage before week 10 of gestation in females with antiphospholipid syndrome. Methods We studied 24 females (primary or secondary antiphospholipid syndrome), who were divided into two groups: females with recurrent miscarriage before week 10 of gestation (M; n = 12) and females with no history of fetal loss (NM; n = 12). Anticardiolipin, a-β2GP1, a-annexin V and sVEGF-R1 concentrations were assessed by ELISA, while lupus anticoagulant was assessed by screening and confirmatory tests. Results A significant association was observed between the number of positive biomarkers and the belonging group ( P < 0.05). Besides, a positive result for lupus anticoagulant and a-β2GP1 was found to be significantly associated to the M group ( P < 0.05). Conclusions Lupus anticoagulant and a-β2GP1 may be implicated in pregnancies complicated by recurrent miscarriage in females with antiphospholipid syndrome.

Newer antiphospholipid antibodies predict adverse outcomes in patients with acute coronary syndrome

Antiphospholipid antibodies (aPLs) have been implicated in atherogenesis. We studied 344 patients with acute coronary syndromes; approximately 40% were aPL+ in 1 or more tests and 60% aPL-. In 215 patients, coronary artery disease (CAD) was angiographically documented, with 43.7% positive for aPL vs 34.9% of patients without CAD positive for aPLs. Anti-beta(2)-glycoprotein I (beta2GPI; 54%) and anti-oxidized low-density lipoprotein (oxLDL)/beta2GPI (48%) were most frequent, accounting for 87% of all aPL+ CAD cases. aPLs correlated with severity of CAD (P = .012). Adverse events occurred in 16.7% of patients with CAD, more frequently in patients who were aPL+ (P = .0006; relative risk, 2.9; 95% confidence interval, 1.5-5.6). Patients who were aPL+ with severe CAD had more adverse events than patients who were aPL- with severe CAD (P = .005) and aPL+ patients undergoing revascularization procedures (P = .001). Vascular events occurred in 21.7% of aPL+ patients compared with 7.1% of aPL- patients (P = .005). Anti-beta2GPI and anti-oxLDL/beta2GPI were associated with CAD severity and adverse outcomes.

High incidence of autoantibodies in Fabry disease patients

Fabry disease (FD) is an X-linked disorder of glycosphingolipid catabolism that results from a deficiency of the lysosomal enzyme alpha-galactosidase A. This defect leads to the accumulation of its substrates, mainly globotriaosylceramide, in lysosomes of cells of different tissues. Different studies have shown the involvement of immunopathologies in different sphingolipidoses. The coexistence of FD and immune disorders such as systemic lupus erythematosus, rheumatoid arthritis and IgA nephropathy, has been described in the literature. The aim of this study was to evaluate the prevalence of a group of autoantibodies in a series of Argentine FD patients. Autoantibodies against extractable nuclear antigens (ENAs), double-stranded DNA, anticardiolipin and phosphatidylserine were assayed by ELISA. Lupus anticoagulants were also tested. Fifty-seven per cent of the samples showed reactivity with at least one autoantigen. Such reactivities were more frequent among males than among females. Antiphospholipid autoantibodies were detected in 45% of our patients. The high rate of thrombosis associated with FD could be related, at least in part, to the presence of antiphospholipid autoantibodies in Fabry patients. We found the presence of ENAs, which are a characteristic finding of rheumatological diseases, previous a frequent misdiagnosis of FD, in around 39% of the cases. The detection of a high level of autoantibodies must be correlated clinically to determine the existence of an underlying autoimmune disease. With the recent development of therapy, the life expectancy in FD will increase and autoimmune diseases might play an important role in the morbidity of FD.

Antiphospholipid syndrome and recurrent miscarriages

Sixty percent of recurrent spontaneous abortions are unexplained. Antiphospholipid syndrome is a multisystem disease with the predominant features of venous and arterial thrombosis, recurrent pregnancy loss, foetal death and the presence of antiphospholipid antibodies. Many epidemiological studies focus on antiphospholipid autoantibodies syndrome (APS) as a cause of recurrent spontaneous abortion (RSA). It is found that 7-25% of RSA would have APS as the main risk factor. 'Association not being synonymous with cause', the proportion of abortions due to the APS is difficult to estimate for several reasons: definition of recurrent abortion is variable, the assays for antiphospholipid antibodies are not well standardised, inclusion of patients in the study group according to the antibodies titre is author dependent. Recent studies suggest association of antiphospholipid antibodies syndrome not only with recurrent abortions but also with infertility. New mechanisms are described by which antiphospholipid antibodies could cause placental thrombosis and infarction, acting directly on the surface anticoagulant expressed on trophoblastic cells. Only lupus anticoagulant (LA) and anticardiolipin antibodies (aCL) assays are sufficiently standardised to be usable in routine. Testing for other antiphospholipid antibodies (aPLs) should remain investigational. Several treatments have been proposed: low doses of aspirin, low or immunosuppressive doses of corticosteroids, and preventive or effective dose of heparin, intravenous immunoglobulin.

Lipid domains in the endocytic pathway

Whereas endosomes connect with both exocytic and endocytic organelle via extensive lipid and protein traffic, each endosome has a distinct lipid and protein composition. Recent observations suggest that different lipid membrane domains exist even in the same endosome. These lipid domains, together with low pH milieu, may present a variety of micro-environments to cargo molecules. Evidence is accumulating which suggests that the alteration of these lipid microdomains may be involved in a number of pathological conditions.

Iliofemoral vein thrombosis and pulmonary embolism associated with a transient ischemic attack in a patient with antiphospholipid syndrome

Several clinical conditions, such as deep vein thrombosis, cerebral infarct, pulmonary infarct, skin ulcers, renal failure, and habitual abortion, are thought to be associated with the antiphospholipid syndrome. The authors describe a 32-year-old woman who had characteristics of the antiphospholipid syndrome including increased immunoglobulin G-cardiolipin antibody titers, iliofemoral vein thrombosis, pulmonary embolism, headache, visual disturbances, and habitual abortion. During hospitalization, she suddenly experienced right-sided weakness. A Tc-99m HMPAO brain scan showed the probability of a transient ischemic attack in the left frontotemporal cortex.

Pathophysiology of the catastrophic antiphospholipid syndrome (CAPS)

Antiphospholipid antibodies (APA) are a common cause of acquired thrombophilia. APA recognize plasma phospholipid-binding proteins (e. g., beta(2)-glycoprotein I, prothrombin, annexin V, etc.). Catastrophic antiphospholipid syndrome (CAPS) is an uncommon variant of the antiphospholipid syndrome. CAPS patients often present with multiorgan failure. Precipitating factors include surgical procedures, drugs, and discontinuation of anticoagulant therapy. Increasingly, infections are recognized as a major precipitating condition. The majority of patients present with renal involvement as well as evidence of acute respiratory distress syndrome (ARDS). This review discusses the clinical and pathophysiologic aspects of CAPS as well as the differenital diagnosis.

Autoimmune antiphospholipid antibodies and cryoglobulinemia

In addition to their role in the thrombotic manifestations of the antiphospholipid syndrome (APS), autoimmune antiphospholipid (aPL) antibodies may also be responsible for direct injury to the blood vessel wall, although the mechanism is unclear. Cryoglobulinemia has been reported infrequently in patients with APS and is one potential means of blood vessel injury. The aim of the present study was to determine if autoimmune aPL antibodies and their target antigens contribute to the formation of cryoprecipitates. Cryoglobulins were identified and isolated from 5 of 8 patients with autoimmune aPL antibodies. Using identical concentrations of immunoglobulins isolated from matched sera and washed cryoprecipitates there was a significant enrichment (at least 100%) of aCL antibodies in the cryoprecipitates from 4 of 5 patients. This involved IgG, IgM and IgA isotypes with specificity for both beta2-glycoprotein I (GPI) and prothrombin (PT). The target antigens were detected in cryoprecipitates from all 5 aPL positive patients and in cryoprecipitates from 3 controls. These results suggest that anti-beta2-GPI and anti-PT antibodies in association with their target antigens are integrally involved in the formation of cryoprecipitates in patients with autoimmune aPL antibodies and provide insight into a potential mechanism for blood vessel injury.

Anti-beta2-glycoprotein I (GPI) autoantibodies, annexin V binding and the anti-phospholipid syndrome

We examined the role of autoantibodies to beta2-GPI and prothrombin (PT) in the inhibition of annexin V binding to cardiolipin (CL) and the association with clinical manifestations of the anti-phospholipid syndrome (APS). Plasma samples from 59 patients with anti-phospholipid (aPL) antibodies were studied. Affinity purification of total IgG and IgG anti-ss2-GPI antibodies was performed using staphylococcal protein A and phospholipid liposomes. Annexin V binding to CL was significantly inhibited by 31/59 (53%) aPL+ plasma samples. There was a significant association between annexin V inhibition and elevated levels of IgG anti-cardiolipin (aCL) (r = -0.62; P < 0.001), IgG anti-ss2-GPI (r = -0.67; P < 0. 001) and a weaker association with lupus anti-coagulant (r = -0.27; P = 0.05). There was no association with other isotypes of aCL and anti-ss2-GPI or with anti-PT of any isotype. In patients with clinical manifestations of the APS there were higher levels of IgG aCL (median (range) Z score): 10.0 (0-17.6) versus 5.0 (0-16.1); P = 0.03), IgG anti-ss2-GPI (4.5 (0-11.3) versus 0.9 (0-9.7); P = 0.02) and greater inhibition of annexin V binding to CL (-3.4 (-11.4-0.6) versus -1.1 (-10.8-1.2); P = 0.22). Odds ratios for the laboratory assays and the presence of clinical manifestations of the APS varied between 0.38 and 4.16, with the highest values for IgG aCL (4.16), IgG anti-ss2-GPI (3.28) and annexin V inhibition (2.85). Additional experiments with affinity-purified IgG antibodies indicated that inhibition of annexin V binding was dependent upon the concentration of ss2-GPI and anti-ss2-GPI antibodies. These results indicate that inhibition of annexin V binding to procoagulant phospholipid surfaces is dependent upon anti-ss2-GPI antibodies and suggest a role for annexin V in the pathogenesis of the APS.

Broadsheet number 56: Mechanisms of fetal loss

The most significant task of the pathologist examining a fetal death is, if possible, the provision of an explanation for the event, which will allow the clinical attendants to counsel the family in an informed and relevant manner. In some cases, no adequate explanation will be possible, though many conditions will be excluded and the importance of this exercise is worth emphasising. Often, however, a combination of fetal, maternal or placental conditions can be found and a full or partial explanation offered, and it is the purpose of this broadsheet to highlight some of these conditions and provide suggestions as to sources of further practical help.

Testing for the antiphospholipid syndrome: importance of IgA anti-beta 2-glycoprotein I

BACKGROUND

Testing for the antiphospholipid syndrome (APS) using anticardiolipin antibodies (aCL) has been problematic. Titers may fluctuate or even become negative. Anti-beta 2-glycoprotein I assays (abeta2-GPI) may be more reliable for diagnosis.

METHODS

In a prospective, blinded study over a nine-month period we retested all patients seen for routine follow-up visits in our clinic who had previously been evaluated for aCL-associated illnesses. Patients were stratified into two groups: group A-patients previously positive for aCL; group B-patients previously negative for aCL. Both groups were further classified according to disease severity. Patients were retested for both aCL and abeta2-GPI (isotypes G, M, A for each) using uniform testing standards.

RESULTS

118 patients with previously positive aCL (group A) were retested. Repeat aCL were positive in 52/118 (44%), abeta2-GPI positive in 69/118 (58%) and 82/118 (69.5%) were positive for one or both assays. In patients with serious organ damage (92% with documented APS), 48.6% were aCL positive, 64% positive for abeta2-GPI, and 75.7% were positive for one or both assays. When only one assay was positive, abeta2-GPI was most frequent (P=0.0096). Overall, IgA abeta2-GPI was the most frequent isotype found (60.9%). On retesting of 73 aCL-negative patients (group B), 9/73 (12%) were aCL positive, 27/73 (36%) were abeta2-GPI positive, with 24/73 (32.9%) having isolated abeta2-GPI. Of those positive for abeta2-GPI, IgA abeta2-GPI was present in 74. 1%. Many of these patients had documented APS.

CONCLUSION

Based on our data, abeta2-GPI assays are superior to aCL assays for diagnosis of APS. The combined use of both assays enhance positive testing results in up to 75% of patients with APS at any stage of illness. ACL negative patients suspected of having APS should be retested for both abeta2-GPI and aCL. IgA abeta2-GPI appears to be the most important isotype detected.

Membrane-induced conformational change of proteins

Many proteins exhibit both a water-soluble and a membrane-bound state. The proteins in the membrane-bound state obtain a distinct structure from that in the bulk, which exists in many important biological processes. In the present paper we would stress that the variation of the physical chemistry properties of the microenvironment adjacent to the membrane-surface region play an important role in the process of the membrane-induced conformational changes of the proteins.

Lipid membrane domains in cell surface and vacuolar systems

Detergent insoluble sphingolipid-cholesterol enriched 'raft'-like membrane microdomains have been implicated in a variety of biological processes including sorting, trafficking, and signaling. Mutant cells and knockout animals of sphingolipid biosynthesis are clearly useful to understand the biological roles of lipid components in raft-like domains. It is suggested that raft-like domains distribute in internal vacuolar membranes as well as plasma membranes. In addition to sphingolipid-cholesterol-rich membrane domains, recent studies suggest the existence of another lipid-membrane domain in the endocytic pathway. This domain is enriched with a unique phospholipid, lysobisphosphatidic acid (LBPA) and localized in the internal membrane of multivesicular endosome. LBPA-rich membrane domains are involved in lipid and protein sorting within the endosomal system. Possible interaction between sphingolipids and LBPA in sphingolipid-storage disease is discussed.

Interaction of anti-phospholipid antibodies with late endosomes of human endothelial cells

Anti-phospholipid antibodies (APLAs) are associated with thrombosis and/or recurrent pregnancy loss. APLAs bind to anionic phospholipids directly or indirectly via a cofactor such as beta(2)-glycoprotein 1 (beta(2)GPI). The lipid target of APLA is not yet established. Recently, we observed that APLAs in vitro can bind lysobisphosphatidic acid (LBPA). The internal membranes of late endosomes are enriched in this phospholipid. The current study was undertaken to determine to what extent binding of APLA to LBPA is correlated with binding to cardiolipin and to beta(2)GPI and to determine whether patient antibodies interact with late endosomes of human umbilical vein endothelial cells (HUVECs) and thus modify the intracellular trafficking of proteins. Binding of patient immunoglobulin G (n=37) to LBPA was correlated significantly with binding to cardiolipin. Although LBPA binding was correlated to a lesser extent with beta(2)GPI binding, we observed that beta(2)GPI binds with high affinity to LBPA. Immunofluorescence studies showed that late endosomes of HUVECs contain LBPA. Patient but not control antibodies recognized late endosomes, but not cardiolipin-rich mitochondria, even when we used antibodies that were immunopurified on cardiolipin. Incubation of HUVECs with patient plasma samples immunoreactive toward LBPA resulted in an accumulation of the antibodies in late endosomes and led to a redistribution of the insulinlike growth factor 2/mannose-6-phosphate receptor from the Golgi apparatus to late endosomes. Our results suggest that LBPA is an important lipid target of APLA in HUVECs. These antibodies are internalized by the cells and accumulate in late endosomes. By modifying the intracellular trafficking of proteins, APLA could contribute to several of the proposed pathogenic mechanisms leading to the antiphospholipid syndrome.

Increased soluble vascular cell adhesion molecule 1 concentrations in patients with primary or systemic lupus erythematosus-related antiphospholipid syndrome: correlations with the severity of thrombosis

OBJECTIVE

Recent studies have shown that in vitro endothelial cells are activated by antiphospholipid antibodies and may support leukocyte adhesion. We studied levels of soluble intercellular adhesion molecule 1 (sICAM-1, sCD54), soluble vascular cell adhesion molecule 1 (sVCAM-1, sCD106), and soluble E-selectin (soluble endothelial leukocyte adhesion molecule 1 [sELAM-1, sCD62E]) in sera from patients with primary antiphospholipid syndrome (primary APS), and compared them with those from patients with systemic lupus erythematosus-associated APS (SLE-APS) or pure SLE, as well as with those from 2 control groups composed of healthy volunteers and patients with thrombosis unrelated to autoimmune diseases.

METHODS

Serum samples from 24 patients with primary APS, 15 patients with SLE-APS, 22 patients with pure SLE, 48 control patients with thrombosis, and 18 healthy volunteers were examined using enzyme-linked immunosorbent assays specific for sICAM-1, sVCAM-1, and sELAM-1.

RESULTS

Serum levels of sVCAM-1, but not sICAM-1 or sELAM-1, were significantly increased in all patient study groups compared with thrombosis control patients and healthy volunteers, but did not differ between the groups of patients with primary APS, SLE-APS, or pure SLE. Concentrations of sVCAM-1 were significantly higher in primary APS or SLE-APS patients with severe, recurrent thrombosis and were negatively correlated with platelet counts in primary APS patients. In patients with primary APS, sVCAM-1 levels were higher if there was thrombotic kidney involvement and correlated with creatinemia.

CONCLUSION

Serum sVCAM-1 concentrations are increased in patients with primary APS, especially those with repeated thrombotic events or kidney involvement. These findings suggest that endothelial/ monocyte interaction may be important in the pathogenesis of primary APS.

Intrinsic fluorescence study of the interaction of human apolipoprotein H with phospholipid vesicles

Apolipoprotein H (ApoH) is a plasma glycoprotein with its in vivo physiological and pathogenic roles being closely related to its interaction with negatively charged membranes. In this paper, the interaction of ApoH with phospholipid vesicles was characterized by (i) detecting the wavelength shift of the fluorescence spectrum of ApoH and (ii) measuring the fluorescence quenching extent of ApoH by the membrane resident quencher 1-palmitoyl-2-stearoyl-(5-doxyl)-sn-glycero-3-phosphocholine (DPC). The observed blue shift upon addition of DMPG vesicles indicated that the tryptophan residues of ApoH moved from a polar to a nonpolar environment. The insertion ability of ApoH into PG-containing vesicles did not depend on the PG content in a stoichiometric way as did the blue shift, indicating that the negatively charged DMPG does not serve as a specific binding site but rather provides a suitable microenvironment for ApoH interaction. The finding that the detachment effect of cations on the blue shift is remarkably different from that on the quenching extent suggests that ApoH is capable of existing in two different conformations when membrane-bound.

Anti-phospholipid antibodies in patients with multiple sclerosis and MS-like illnesses: MS or APS?

OBJECTIVE

To describe the frequency, clinical, and laboratory features of patients diagnosed with multiple sclerosis (MS) or MS-like illnesses (MSL) among a large, prospectively followed cohort of anti-phospholipid antibody (aPL)-positive patients.

METHODS

Between 1990 and 1995 patients referred to a university-affiliated rheumatology clinic were prospectively evaluated for aPL based on questionnaires designed to detect aPL-related symptoms and/or a family history of aPL-related illnesses. Magnetic resonance imaging (MRI) was performed when significant neurological features were present. A subgroup of all patients diagnosed with MS or MSL was identified and their clinical, laboratory, and imaging findings were reviewed.

RESULTS

Of 322 patients evaluated for aPL-related symptoms or events, 189 (59%) were positive for at least one class of aPL. Twenty-six of 322 patients (8%) carried a diagnosis of MS or MSL, either at the initial evaluation or during the study period. Twenty-three of the 26 individuals (88%) tested positive for aPL, while the remaining 3 (11%) tested repeatedly negative. Eighteen of the 23 patients (78%) had either more than one class of aPL or had multiple positive titers. IgM aCL was noted in 18 of the 23 patients (78%). Oligoclonal bands were noted in five patients. Antinuclear antibodies (ANA) and low complement levels were frequently observed. Blinded MRI readings showed lesions consistent with MS in the majority of cases. Clinically, 7 patients had transverse myelitis (TM), while optic neuritis (ON) was present in 8 patients. Most patients had either occult symptoms of rheumatic disease or contributory family histories. None had a defined underlying connective-tissue disease.

CONCLUSION

A substantial number of aPL-positive patients have a concurrent diagnosis of MS or MSL, frequently presenting with elevated IgM aCL, optic neuritis, and transverse myelitis. The anti-phospholipid syndrome (APS) should be strongly considered as an alternative diagnosis to MS in these patients.

Heterogeneity of anti-phospholipid and anti-endothelial cell antibodies

The role of the anti-phospholipid antibodies (APLA) and anti-endothelial cell antibodies (AECA) in the pathogenesis of anti-phospholipid syndrome (APS) is unclear. Differences in the reported involvement of APLA may be due, in part, to the polyclonal nature of these antibodies and the use of serum and serum fractions for analysis. To circumvent this issue, we generated monoclonal antibodies (MAB) from three patients with APS and two healthy controls. We then compared the antigen binding patterns and the heavy chain variable region (VH) DNA sequences of the MAB derived from patients with APS to those from healthy controls. The results of this study indicate that APLA and AECA comprise a highly heterogeneous population of antibodies with respect to the antigens they recognize, as well as VH gene usage. MAB derived from patients with APS do not differ from those derived from normal individuals based on either antigen recognition or VH gene usage. These results suggest the importance of additional predisposing factors in the pathogenesis of APS.

Evaluation of patients with CNS involvement in SLE

Patients with systemic lupus erythematosus (SLE) may present with a wide array of neuropsychiatric (NP) clinical features. This may either be a primary manifestation of SLE, the result of a complication of the disease or its therapy, or a concurrent disease process. As there is no single diagnostic gold standard for NP-SLE, the assessment of individual patients is heavily dependent upon clinical evaluation in addition to information from studies of autoantibodies, brain structure and function. Despite their lack of diagnostic sensitivity and specificity, these tests frequently provide information that can be used to support or refute the clinical impression. They may also provide a basis for the prospective evaluation of the efficacy of therapeutic interventions in individual patients with NP-SLE.

Immune clearance of phosphatidylserine-expressing cells by phagocytes. The role of beta2-glycoprotein I in macrophage recognition

The function of beta2-glycoprotein I (beta2GPI), a 50-kDa serum glycoprotein, is not completely understood but has been suggested to be involved in the regulation of thrombosis (Brighton, T. A., Hogg, P. J., Dai, Y.-P., Murray, B. H., Choing, B. H., and Chesterman, C. N. (1996) Br. J. Haematol. 93, 185-194) and the clearance of phosphatidylserine (PS)-expressing cells (Chonn, A., Semple S. C., and Cullis P. R. (1995) J. Biol. Chem. 270, 25845-25849). To further understand the role of this protein, we characterized the ability of beta2GPI to interact with PS vesicles and influence their uptake by macrophages in vitro. beta2GPI bound to and precipitated vesicles containing anionic but not zwitterionic phospholipids in a gel diffusion assay. beta2GPI also inhibited the procoagulant activity of PS liposomes. In vitro phagocytosis studies showed 20-fold greater uptake of PS liposomes over phosphatidylcholine liposomes. This enhanced uptake was maintained even after PS was "shielded" with beta2GPI and further increased upon the addition of beta2GPI antibodies. Similar to liposomes, PS-expressing apoptotic thymocytes and lipid symmetric red blood cell ghosts bound beta2GPI. Macrophage uptake of these cells was also maintained or enhanced in the presence of beta2GPI and further increased upon the addition of beta2GPI antibodies. It is concluded that beta2GPI can play a critical role in hemostasis by influencing both thrombosis and the clearance of PS-expressing cells.

The concept and classification of antiphospholipid/cofactor syndromes

In 1990, three groups simultaneously reported that putative IgG antibodies to anionic phospholipids were either not directed to phospholipids or at least required beta 2-glycoprotein-I (beta 2-GP-I) for reactivity in vitro. During the same year, our group described a patient with "idiopathic' hemolytic anemia with serum and erythrocyte-bound IgM antibodies to phosphatidylcholine later found to be independent of beta 2-GP-I for antigen recognition. Lately, the field has been expanded considerably with: (1) the description of other potential antigens such as prothrombin for some lupus anticoagulants, (2) the finding of crossreactivity between some antiphospholipid antibodies (aPL) with thrombomodulin, (3) the presence of serum antibodies to beta 2-GP-I (anti-beta 2-GP-I) in patients with SLE and thromboses, (4) the findings that the clinical manifestations of APS in SLE patients associate more strongly with anti-beta 2-GP-I than with aPL, (5) our finding of a group of SLE patients with the clinical manifestations of APS, with negative serum aPL, but with positive anti-beta 2-GP-I, (6) the description of a group of patients with the clinical manifestations of APS, without serum aPL, without serological nor clinical evidence of any autoimmune disease, but with IgG anti-beta 2-GP-I, and (7) the observation that serum anti-phosphatidylethanolamine antibodies detected in some patients with APS require kininogen (alone or complexed with the kininogen-binding protein), prekallikrein and/or factor XI for in vitro reactivity. Thus, there are antibodies that may be considered true aPL; other "aPL' require a protein cofactor for their detection in vitro, at least in the case of beta 2-GP-I it would appear that their epitope is present on the protein proper not on the phospholipid, hence these are pseudo aPL, and a third group of related anti-cofactor autoantibodies that are directed to the protein in the absence of phospholipid. Clearly, the term "antiphospholipid syndrome' has become obsolete. We propose the term "Antiphospholipid/Cofactor Syndromes' to cull the various syndromes.