Repertoire cloning of a human IgG inhibitor of alpha IIB beta 3 function. The OG idiotype

A patient (OG) with Glanzmann thrombasthenia became refractory to platelet transfusion following the production of IgG antibodies (Ab1) specific for the integrin subunit beta 3. We generated recombinant VH and VL cDNA libraries using IgG-specific mRNA isolated from OG peripheral blood B-lymphocytes that had been selected for binding to antigen (alpha IIb beta 3 adsorbed to plastic dishes). These antigen-specific B-lymphocytes contain rearranged VH DNA segments that belong exclusively to the VH4 gene family. Recombinant Fab were expressed on the surface of filamentous phage coinfected with VH and VL segments cloned into the phagemid pHEN1 or the phage fd-tet-DOG1. To facilitate selection of the desired recombinant Ab1 Fab, we developed a rabbit polyclonal antibody specific for affinity-purified OG anti-beta 3 Fab (Ab2). Ab2 reacts specifically with Ab1, and this interaction is inhibited by purified alpha IIb beta 3. Following three rounds of phage selection on Ab2 adsorbed to plastic dishes and random reassociation of heavy and light chains, we isolated Ab1 Fab and tested their binding to alpha IIb beta 3. Five Id-positive Fab were selected for further characterization. These Fab use one of two VH genes (H21 or H23) complexed with one of three V lambda genes. Subsequent sequence data demonstrated that all three lambda genes are the same clone L22 which uses a germline V lambda gene segment. Fab using H23 bind to alpha IIb beta 3, while those using H21 do not. Based on sequence homology, both H21 and H23 use VH gene segments belonging to the VH4 gene family. Thus, the idiotype OG is restricted to the VH4 gene family and is the first sequenced prototype of human antibodies that bind close to or at a functional epitope(s) of alpha IIb beta 3.

Evidence of noninvolvement of swine MHC class II in the in vitro proliferative response of human lymphocytes to porcine endothelial cells

Successful pig-to-human xenotransplantation may expose swine endothelium to the human immune system. Since endothelial MHC class II expression is crucial in the genesis of an allogeneic lymphocyte response, the involvement of porcine MHC (SLA) class II molecules in the induction of human lymphocyte proliferation was studied. When cocultured with a confluent monolayer of irradiated porcine aortic endothelial cells (PAEC), human peripheral blood mononuclear cells (PBMC) incorporated tritiated thymidine. Monocyte depletion strongly reduced the magnitude of the lymphocyte proliferative response. Resting cultured PAEC were SLA class II-negative and an induction of these molecules during the xenogeneic mixed lymphocyte endothelial cell culture (XMLEC) was not observed. Moreover, the addition of an antibody directed against the SLA-DR molecule was without effect. Lymphocyte proliferation was also studied in response to SLA class II-positive stimulating cells--either human TNF-alpha-stimulated PAEC or porcine splenocytes. Induction of SLA class II molecules on PAEC had no effect on the human PBMC proliferative response. Moreover, human PBMC did not proliferate in response to porcine splenocytes. These results suggest (1) that SLA class II molecules are not involved in the induction of the human lymphocyte proliferative response and (2) that the endothelial nature of the stimulating cells plays a key role in this proliferation.

Tissue factor activity of syncytiotrophoblast plasma membranes and tumoral trophoblast cells in culture

During pregnancy, important modifications of hemostasis occur resulting in mothers in hypercoagulability and the role of placental cells such as trophoblast cells has been hypothesized. In this study, we first showed that syncytiotrophoblast plasma membranes, isolated from normal human placenta, expressed a strong tissue factor (TF) activity. We then studied TF activity of two continuous trophoblast cell lines (JEG-3 and BeWo) in comparison to human umbilical vein endothelial cells (HUVEC) and transformed human endothelial cells (ECV-304). TF assays were performed on intact detached confluent cells. Unstimulated JEG-3 and BeWo cells exhibited a very high TF activity which slightly increased after 2 to 4 h TNF-alpha stimulation. In contrast, HUVEC and ECV-304 had a lower basal TF activity which was mainly inducible by TNF-alpha, with a maximum effect after 4 to 6 h stimulation. For both cell types, TF activity was decreased to basal value after 16-hour TNF-alpha stimulation. These results support that trophoblast cells are able to express TF but the involvement of this property in the hemostatic physiological changes observed during pregnancy, remains to be demonstrated.

Further characterization of the thrombasthenia-related idiotype OG. Antiidiotype defines a novel epitope(s) shared by fibrinogen B beta chain, vitronectin, and von Willebrand factor and required for binding to beta 3

A patient (OG) with Glanzmann thrombasthenia became refractory to platelet transfusion after the production of an immunoglobulin G (IgG) isoantibody (Ab1) specific for the integrin subunit beta 3. To determine the frequency at which the OG idiotype is found in the general population and in immune-mediated disease states, we developed a rabbit polyclonal antibody (Ab2) specific for affinity-purified OG anti-beta 3 Fab. The binding of Ab2 to Ab1 is inhibited by purified alpha IIb beta 3. Ab2 als binds to IgG specific for alpha IIb beta 3 obtained from one nonrelated Glanzmann thrombasthenia patient ES who has developed isoantibodies of similar specificity. On the other hand, Ab2 does not recognize alpha IIb beta 3-specific antibodies produced by two Glanzmann thrombasthenia patients, AF and LUC, who have developed isoantibodies with specificities distinct from that of the OG isoantibody. Moreover, Ab2 does not recognize alpha IIb beta 3-specific antibodies developed by three representative patients with (autoimmune) thrombocytopenic purpura or six representative patients with alloimmune thrombocytopenias, nor does it bind to IgG from any of 13 nonimmunized individuals. We have found that Ab2 also binds to selected protein ligands of alpha IIb beta 3 namely, fibrinogen, vitronectin, and von Willebrand factor, but not to other protein ligands or control proteins, such a fibronectin, type I collagen, and albumin. The epitope(s) recognized by Ab2 on each adhesive protein are either very similar or identical since each protein can inhibit the binding of Ab2 to any of the other proteins. The epitope on fibrinogen recognized by Ab2 resides in the B beta chain, and is likely contained within the first 42 amino acids from the NH2 terminus. Since OG IgG inhibits fibrinogen binding to alpha IIb beta 3, the specificity of the OG idiotype defines a novel binding motif for the integrin alpha IIb beta 3 that is shared by fibrinogen, vitronectin, and von Willebrand factor, but distinct from previously described RGD-containing sites on the fibrinogen, A alpha chain or the fibrinogen gamma chain COOH-terminal decapeptide site. Our findings reported here represent an excellent example of molecular mimicry in which an antigen-selected, IgG inhibitor of alpha IIb beta 3 function shares a novel recognition sequence common to three physiologic protein ligands of that receptor.

Antiphospholipid and anti-beta 2 glycoprotein I antibodies in monozygotic twin sisters

We describe an 18-year-old woman with primary antiphospholipid syndrome whose monozygotic twin sister is as yet an asymptomatic carrier of the lupus anticoagulant, anticardiolipin, and anti-beta 2 glycoprotein I (beta 2GPI) antibodies. Serum concentrations of beta 2GPI were normal in the patient and elevated in her sister. HLA and complement C4 phenotypes showed the presence of class II antigens DR7 and DRw53 and of a C4AQ0 allele. This supports the theory that a genetic predisposition may influence the appearance of these autoantibodies.

Adhesive properties of choriocarcinoma cells toward lymphocytes activated or not by interleukin-2

Choriocarcinoma cells (CC) in vitro are resistant to NK lysis but sensitive to lysis by blood or decidual effectors activated by interleukin-2 (IL-2). Because lytic activity requires a step of adhesion, the adhesive properties of the choriocarcinoma cells BeWo, JEG-3, and JAR were examined functionally toward peripheral blood lymphocytes. The adhesion of lymphocytes to choriocarcinoma cells was very low and did not increase after stimulating lymphocytes with IL-2. As demonstrated by cytofluorimetry analysis, choriocarcinoma cells and cytotrophoblast cells prepared from term placenta expressed intercellular adhesion molecule-1 (ICAM-1), whereas only CC expressed CD56. Tumor necrosis factor-alpha or interferon-gamma increased the expression of ICAM-1 on choriocarcinoma cells without modifying the adhesion of lymphocytes to choriocarcinoma cells. These results suggest that resistance of choriocarcinoma cells to lysis by cytotoxic effectors could partially be attributed to the low level of lymphocyte adhesion to these cells.

Methodological approach for the detection of IgM anticardiolipin antibodies

The effects of 10% fetal calf serum (10% FCS), 10% adult bovine serum (10% ABS) and 1% bovine serum albumin (1% BSA) buffers on the reactivity of samples with or without IgM anticardiolipin antibodies (ACA IgM) were studied on cardiolipin-coated wells (target wells) and cardiolipin-free wells (control wells) in an ELISA test. With 1% BSA, target well reactivity was very low for samples containing ACA IgM. The 10% FCS induced a moderate but significant binding of polyclonal IgM on target wells particularly in the case of IgM hypergammaglobulinemia. With 10% ABS, whatever the IgM serum level, this non-specific binding did not occur on the solid phase either in the presence or in the absence of cardiolipin. Using 10% ABS, the study of 35 SLE sera showed that non-specific binding of IgM on control-wells occurred only with ACA IgM positive samples. Thus with the use of 10% ABS, we propose that subtraction of control well from target well values must not be performed for the detection of ACA IgM. The significance of cardiolipin-free well IgM reactivity of ACA IgM positive sera is discussed.

Usefulness of antiplatelet drugs in the management of heparin-associated thrombocytopenia and thrombosis

Heparin-associated thrombocytopenia and thrombosis is a severe complication of systemic heparin therapy. Its treatment is mainly based upon discontinuation of heparin therapy. However in some patients requiring emergency cardiac or vascular surgery, reexposure to heparin may be unavoidable. We report the management of two such patients by use of antiplatelet drugs for a vascular procedure. In the two cases, a combination of iloprost, a stable prostacyclin analogue (1 to 2 ng/kg/mn) with aspirin and dipyridamole was shown to inhibit ex vivo the heparin-induced platelet aggregation. These antiplatelet agents were continued during the perioperative period. A successful vascular procedure was achieved with full heparinization without subsequent thrombocytopenia or thrombotic or hemorrhagic complications. This experience supports the hypothesis that heparin can be readministered early to patients with heparin-associated thrombocytopenia and thrombosis, provided antiplatelet therapy is given.

Specific quantification of heparin-dependent antibodies for the diagnosis of heparin-associated thrombocytopenia using an enzyme-linked immunosorbent assay

In order to specifically detect heparin-dependent antibodies in patients with suspected heparin-associated thrombocytopenia (HAT), an adapted ELISA test was developed. Serum-platelet bindable IgG (SPb-IgG) were measured in the absence and in the presence of heparin in the sera from a/ 25 normal controls, 25 patients treated by heparin without thrombocytopenia, 29 thrombocytopenic patients not receiving heparin and b/ 12 patients with confirmed HAT. In the absence of heparin, the 12 HAT sera showed normal or elevated SPb-IgG levels (range = 10.4-36 Arbitrary Units or AU) as compared to healthy controls (8-17.1 AU). After coincubation of HAT sera with heparin (0.25, 0.50, 0.75, and 1 IU/ml), SPb-IgG levels were consistently elevated (range = 22.8-150 AU), and this increase in IgG binding (equal in mean to 200%) was always inhibited with 5 IU/ml of heparin. In contrast, a mean maximum increase in SPblgG levels of only 20% was registered in all control groups whatever the tested heparin concentration. Thus, this ELISA allows the specific diagnosis of HAT by demonstrating a serum IgG binding on platelets only in the presence of therapeutic concentrations of heparin.

ELISA for the detection of anticardiolipin antibodies. High specificity based on the use of adult bovine serum as buffer and systematic subtraction of non-specific binding

We have used an ELISA procedure to compare the reactivity of samples with or without IgG anticardiolipin antibodies (ACA) on cardiolipin-coated wells (target wells) and cardiolipin-free wells (control wells), using 10% fetal calf serum (10% FCS), 10% adult bovine serum (10% ABS) or 1% bovine serum albumin (1% BSA) as buffer. With 1% BSA, ACA reactivity was very low which suggests that this buffer would be inappropriate for use in ELISA procedures for ACA. 10% FCS induced non-specific binding of normal IgG only on target wells, particularly in the case of IgG hypergammaglobulinemia. With 10% ABS, this non-specific binding occurred on the solid phase with and without cardiolipin and could be accurately evaluated by subtracting the absorbance of control wells. Results of assays on 35 systemic lupus erythematosus sera using 10% ABS as buffer showed that highly specific results-could be obtained only if non-specific binding was systematically subtracted.

Comparative study of the fibrinolytic system in human fetuses and in pregnant women

Levels of major parameters of fibrinolysis were measured in 50 normal human fetuses between 19 and 39 weeks of gestation and compared to those of 50 healthy normal pregnant women and 30 adult controls. In fetuses, euglobulin clot lysis time (ECLT) was significantly shortened, plasminogen level was low and histidine-rich glycoprotein undetectable. While t-PA and u-PA levels were slightly lower than in adult controls, a significant decrease in PAI activity was demonstrated and no PAI-2 could be detected in fetal plasma. In contrast with these findings, the fibrinolytic equilibrium of pregnant women exhibited a prolonged ECLT and a strong increase in both PAI activity and PAI-2 antigen levels, while only a moderate elevation in u-PA and t-PA levels was measured.

Thrombocytopenia in systemic lupus erythematosus: association with antiplatelet and anticardiolipin antibodies

Serum platelet bindable immunoglobulin G (SPbIgG) and anticardiolipin antibodies (ACA) have been assayed in SLE patients with (group A, n = 8) and without thrombocytopenia (group B, n = 8). Moreover, we studied the binding of serum IgG on platelet proteins using a Western blotting procedure. Increased levels of SPbIgG were found in all thrombocytopenic patients and in five cases of group B. A binding of serum IgG on platelet proteins (80 and 53 kDa) was seen in seven of eight thrombocytopenic patients and in only one case of group B. ACA were present in the serum of four patients in each group and a significant inhibition of ACA IgG by entire washed platelets was achieved in only two severe thrombocytopenic cases. These data suggest that participation of ACA to the platelet destruction can be evoked for a few SLE patients, whereas recognition of platelet protein determinants by lupus autoantibodies is necessary to the thrombocytopenia.

[Gastropericardial fistula. Review of the literature apropos of an original case]

The authors present a case of pneumopericarditis consecutive to a perforating gastric ulcer complicating a left, post-traumatic diaphragmatic hernia, evolving favorably after radical surgery. 52 cases of gastro-pericardial fistulas were reported in the literature, 42 of which related to benign pathology. The overall mortality rate for this disease was 85%, although the course was favorable in one patient out of two, whenever radical surgery had been resorted to. In order to ensure these patients the best chances for survival, treatment should combine pericardial drainage and case-adapted gastro-intestinal surgery in an intensive care setting.

Prenatal diagnosis of platelet disorders

The antenatal diagnosis of platelet disorders represents real progress in the early detection of haemorrhagic diseases occurring in the fetus. However, the diagnosis is only possible in some cases during the first trimester of gestation, and not in the first weeks as is the case for other hereditary disorders such as abnormal haemoglobins. This delay can be reduced now that the molecular abnormalities responsible for some platelet disorders have been discovered. If the region of chromosome 17 and the DNA sequence coding for the glycoproteins GP IIb-IIIa were known, this would make possible the recognition of the gene defect responsible for Glanzmann's thrombasthenia. This could also permit the diagnosis of Glanzmann's thrombasthenia at the gene level, i.e. during the first weeks of gestation. However, the use of gene markers could be limited by the fact that a monomorphic clinical expression of Glanzmann's thrombasthenia could correspond to different genetic mutations which can all result in a defect in GP IIb-IIIa synthesis and assembly. If such diagnosis could be made very early, it would only represent real progress if a specific treatment could be applied. New therapeutic approaches to immune thrombocytopenia during pregnancy appear to be possible and can be applied when there is a risk to the fetus, they are still either experimental or anecdotal and there is a real need for a well-designed clinical trial. In all fetal platelet disorders, the risk of fetal death following fetal blood sampling must not be underestimated and very careful, intensive care is necessary after such an investigation. In the absence of a specific therapy, this antenatal diagnosis must be restricted to cases in which the risk of severe haemorrhagic complications are anticipated and where there is a well-documented family history. The patients must be properly informed of all the aspects of the investigation, including the possible risks. As has been the case for other haematological disorders, progress will be made, and we can anticipate that eventually in utero bone-marrow transplantation or gene correction be performed to cure the disease before birth.

Hemostasis development in the lamb fetus and neonate

Fetal and neonatal lamb hemostasis were studied from the 60th day of pregnancy to birth. Platelet counts and blood coagulation, as assessed by tests such as recalcification time and thromboelastography, were similar in fetuses, neonates, and adult sheep. The values of coagulation factors were low, ie, vitamin K-dependent Factors II, VII, IX, and X remained unchanged (30 and 40% of adult reference values) until the last 10 days of gestation, and then increased until birth (40 to 60%). Values of fibrinogen and Factor V followed a similar pattern, although their activities became identical to adult values at birth. Also, we measured values of protein C and antithrombin III, which are synthesized by the liver. The importance of hepatic failure and fetal vitamin K deficiency were discussed. Factors VIII and XII activities increased gradually during pregnancy to reach adult values at birth. Fetal fibrinolytic activity increased. This could not be explained by the values of tissue-type plasminogen activator (it was not detectable) or by the presence of its fast-acting inhibitor, whose concentration did not decrease.