The benefits of transplacental treatment of isolated congenital complete heart block associated with maternal anti-Ro/SSA antibodies: a review.

Isolated congenital complete atrio-ventricular block (CAVB) is associated with the transplacental passage of maternal autoantibodies directed to foetal Ro/SSA ribonucleoproteins. Their interactions most likely trigger the inflammation of the atrio-ventricular node and the myocardium in susceptible foetuses. The inflamed tissues may then heal with fibrosis that may cause heart block, endocardial fibroelastosis, and dilated cardiomyopathy. CAVB, the most common cardiac complication, typically develops between 18 and 24 gestational weeks. Untreated, the condition carries a significant mortality risk as the foetus needs to overcome the sudden drop in ventricular rate, the loss of normal atrial systolic contribution to ventricular filling, and perhaps concomitant myocardial inflammation and fibrosis. The rationale to treat a foetus at the stage of CAVB is primarily to mitigate myocardial inflammation and to augment foetal cardiac output. Maternal dexamethasone administration has been shown to improve incomplete foetal AV block, myocardial dysfunction, and cavity effusions. Beta-sympathomimetics may be useful to increase the foetal heart rate and myocardial contractility. Published data from our institution suggest an improved survival >90% if maternal high-dose dexamethasone was initiated at the time of CAVB detection and maintained during the pregnancy and if a beta-adrenergic drug was added at foetal heart rates below 55 beats/min. Despite the improvement in outcome, there is an ongoing debate about treatment-related risks. In this review, we will appraise the natural history of untreated CAVB, discuss currently available management options, and examine the results and risks of in-utero treatment of antibody-mediated CAVB.

Vega is a rapidly rotating star.

Vega, the second brightest star in the northern hemisphere, serves as a primary spectral type standard. Although its spectrum is dominated by broad hydrogen lines, the narrower lines of the heavy elements suggested slow to moderate rotation, giving confidence that the ground-based calibration of its visible spectrum could be safely extrapolated into the ultraviolet and near-infrared (through atmosphere models), where it also serves as the primary photometric calibrator. But there have been problems: the star is too bright compared to its peers and it has unusually shaped absorption line profiles, leading some to suggest that it is a distorted, rapidly rotating star seen pole-on. Here we report optical interferometric observations that show that Vega has the asymmetric brightness distribution of the bright, slightly offset polar axis of a star rotating at 93 per cent of its breakup speed. In addition to explaining the unusual brightness and line shape peculiarities, this result leads to the prediction of an excess of near-infrared emission compared to the visible, in agreement with observations. The large temperature differences predicted across its surface call into question composition determinations, adding uncertainty to Vega's age and opening the possibility that its debris disk could be substantially older than previously thought.

[Accidental fall and word finding problems in heart valve disease]. / Sturz und Wortfindungsstörungen bei valvulärer Herzkrankheit.

Abscesses of the spleen are rare and, if untreated, lead to death. The usual mode of development is by hematogenous spread of infection. Treatment options are splenectomy, percutaneous drainage and in selected cases an antibiotic therapy. We report a case of a splenic abscess due to Streptococcus bovis treated with antibiotics only.

Regional left ventricular function during transient coronary occlusion: relation with coronary collateral flow.

OBJECTIVE: To test the hypothesis that regional left ventricular (LV) function during balloon angioplasty is related to the amount of collateral flow to the ischaemic region. DESIGN: Prospective study. SETTING: Tertiary referral centre. METHODS: In 50 patients with coronary artery disease and without myocardial infarction, regional systolic and diastolic LV function was determined using tissue Doppler ultrasound (TD) before and at the end of a 60 second occlusion of a stenotic lesion undergoing percutaneous transluminal coronary angioplasty (PTCA) through a pressure guidewire. The study population was subdivided into a group with collaterals insufficient (n = 33) and one with collaterals sufficient (n = 17) to prevent ECG ST shifts suggestive of myocardial ischaemia during PTCA. Pulsed TD was performed from an apical window in the myocardial region supplied by the vessel being treated by PTCA. Pressure derived collateral flow index (CFI) was determined by simultaneous measurement of mean aortic (P(ao)) and distal intracoronary occlusive pressures (P(occl)), where CFI = (P(occl) - 8)/(P(ao) - 8). RESULTS: At 60 seconds of occlusion, several parameters of systolic and diastolic TD derived LV long axis function were significantly different between the groups. Also, there was a significant correlation between regional systolic excursion velocity, early diastolic excursion velocity, regional isovolumetric relaxation time, and CFI. CONCLUSION: During brief coronary artery occlusions, regional systolic and diastolic LV function is directly related to the amount of collateral flow to this territory.

Transcriptional induction of MKP-1 in response to stress is associated with histone H3 phosphorylation-acetylation.

Mitogen-activated protein (MAP) kinase phosphatase 1 (MKP-1) has been shown to play a critical role in mediating the feedback control of MAP kinase cascades in a variety of cellular processes, including proliferation and stress responsiveness. Although MKP-1 expression is induced by a broad array of extracellular stimuli, the mechanisms mediating its induction remain poorly understood. Here we show that MKP-1 mRNA was potently induced by arsenite and ultraviolet light and modestly increased by heat shock and hydrogen peroxide. Interestingly, arsenite also dramatically induces phosphorylation-acetylation of histone H3 at a global level which precedes the induction of MKP-1 mRNA. The transcriptional induction of MKP-1, histone H3 modification, and elevation in MKP-1 mRNA in response to arsenite are all partially prevented by the p38 MAP kinase inhibitor SB203580, suggesting that the p38 pathway is involved in these processes. Finally, analysis of the DNA brought down by chromatin immunoprecipitation (ChIP) reveals that arsenite induces phosphorylation-acetylation of histone H3 associated with the MKP-1 gene and enhances binding of RNA polymerase II to MKP-1 chromatin. ChIP assays following exposure to other stress agents reveal various degrees of histone H3 modification at the MKP-1 chromatin. The differential contribution of p38 and ERK MAP kinases in mediating MKP-1 induction by different stress agents further illustrates the complexity and versatility of stress-induced MKP-1 expression. Our results strongly suggest that chromatin remodeling after stress contributes to the transcriptional induction of MKP-1.

Increased central body fat deposition precedes a significant rise in resting blood pressure in male offspring of essential hypertensive parents: a 5 year follow-up study.

OBJECTIVES: As long as offspring of essential hypertensive parents (OHyp) are lean, their blood pressure usually remains within normal limits. The mechanism(s) transforming this 'genetically dysregulated normotension' into hypertension are unclear. We hypothesized that OHyp are not only genetically prone to develop hypertension, but may also have a particular propensity to accumulate central body fat. DESIGN: A 5-year follow-up cohort study. SETTING: University Hospital in Switzerland. PARTICIPANTS: Seventeen young (25 +/- 1 years, mean +/- SD), lean healthy normotensive male OHyp and 17 age- and sex-matched offspring of normotensive parents (ONorm) paired for baseline blood pressure with the OHyp. MAIN OUTCOME MEASURES: Resting and exercise blood pressure, body weight, body mass index (BMI) and waist-to-hip ratio were assessed at baseline and after 5 years. RESULTS: At baseline, body weight, BMI, waist-to-hip ratio and blood pressure did not differ significantly between OHyp and ONorm. At follow-up, body weight was increased in both groups (from 73.9 +/- 6.0 to 77.7 +/- 8.1 kg in OHyp, P = 0.008, and from 71.5 +/- 6.9 to 73.5 +/- 6.6 kg in ONorm, P = 0.03). BMI followed a similar pattern. In contrast, waist-to-hip ratio increased in OHyp (from 0.84 +/- 0.03 to 0.87 +/- 0.03, P = 0.012), but not in ONorm (from 0.84 +/- 0.03 to 0.84 +/- 0.04, P = 0.79) and was therefore higher in OHyp at follow-up (P = 0.011, OHyp versus ONorm). Peak systolic blood pressure during dynamic exercise also rose at 5 years in the OHyp (from 182 +/- 10 to 214 +/- 17 mmHg, P = 0.0001) while resting systolic blood pressure only tended to do so (from 121 +/- 7 to 128 +/- 12 mmHg, P = 0.07). In ONorm, resting and peak dynamic exercise systolic blood pressure remained unchanged (119 +/- 11 versus 121 +/- 9 mmHg, baseline versus follow-up, P = 0.40, and 186 +/- 12 versus 196 +/- 22 mmHg, P = 0.10, respectively). Thus, systolic peak exercise blood pressure was significantly (P = 0.014) elevated at follow-up in OHyp compared to ONorm, while resting systolic blood pressure only tended (P = 0.06) to do so. CONCLUSIONS: Initially lean normotensive OHyp have a disparate long-term course of central body fat as compared to ONorm. Thus, OHyp are not only genetically prone to develop hypertension, but they also have a particular propensity to accumulate central body fat, even before a distinct rise in resting blood pressure occurs. The exaggerated blood pressure response to exercise observed at follow-up in the OHyp represents another marker that confers them a greater risk of developing future hypertension.

Radial artery compliance in response to mental stress in normotensive offspring of hypertensive parents.

OBJECTIVES: Compared to normal subjects hypertensive patients have an increased radial artery isobaric distensibility, contrasting with a decrease in elasticity of large arteries and systemic compliance. To address the question whether elasticity is increased in response to long-standing elevated blood pressure or is present at an early stage of the disease, we compared normotensive offspring of hypertensive parents with control subjects. Furthermore, enhanced sympathetic response to mental stress was demonstrated in individuals predisposed to hypertension and might contribute to the elevation of blood pressure via a peripheral mechanism. Thus, an abnormal vasoconstrictive response of the radial artery to psychological stress was sought in these subjects. DESIGN: The geometry and the elastic porperties of the radial artery were assessed in normotensive offspring of hypertensive and normotensiven parents at baseline and during mental stress. METHODS: A high-precision echo-tracking ultrasound device was combined with photoplethysmography for continuous measurement of radial artery diameter and isobaric distensibility in 18 normotensive offspring of parents with essential hypertension and 18 control subjects under resting conditions and during a 3-minute mental stress test. RESULTS: Baseline arterial distensibility and compliance were comparable in offspring of hypertensive and normotensive parents. During mental stress, blood pressure and heart rate increased similarly in both groups. Adrenergic activation did not alter the elastic properties of the radial artery in the individuals with a genetic predisposition to essential hypertension. CONCLUSIONS: There was no alteration in elastic properties of the radial artery in normotensiven individuals at genetic risk to develop arterial hypertension. Furthermore, mental stress did not abnormally increase the vascular tone of this medium-sized muscular artery in these subjects as compared to controls. This indicates that functional and/or structural vascular alterations do not precede a distinct rise in blood pressure or abnormal blood pressure reactivity in subjects prone to develop essential hypertension.

Promotion of collateral growth by granulocyte-macrophage colony-stimulating factor in patients with coronary artery disease: a randomized, double-blind, placebo-controlled study.

BACKGROUND: Experimentally, activated macrophages have been documented to induce vascular proliferation. METHODS AND RESULTS: In 21 patients (age 74+/-9 years) with extensive coronary artery disease not eligible for coronary artery bypass surgery, the effect of granulocyte-macrophage colony-stimulating factor (GM-CSF, Molgramostim) on quantitatively assessed collateral flow was tested in a randomized, double-blind, placebo-controlled fashion. The study protocol consisted of an invasive collateral flow index (CFI) measurement immediately before intracoronary injection of 40 microg of GM-CSF (n=10) or placebo (n=11) and after a 2-week period with subcutaneous GM-CSF (10 microg/kg) or placebo, respectively. CFI was determined by simultaneous measurement of mean aortic pressure (P(ao), mm Hg), distal coronary occlusive pressure (P(occl), mm Hg; using intracoronary sensor guidewires), and central venous pressure (CVP, mm Hg): CFI=(P(occl)-CVP)/(P(ao)-CVP). CFI, expressing collateral flow during coronary occlusion relative to normal antegrade flow during vessel patency, changed from 0.21+/-0.14 to 0.31+/-0.23 in the GM-CSF group (P<0.05) and from 0.30+/-0.16 to 0.23+/-0.11 in the placebo group (P=NS). The treatment-induced difference in CFI was +0.11+/-0.12 in the GM-CSF group and -0.07+/-0.12 in the placebo group (P=0.01). ECG signs of myocardial ischemia during coronary balloon occlusion occurred in 9 of 10 patients before and 5 of 10 patients after GM-CSF treatment (P=0.04), whereas they were observed in 5 of 11 patients before and 8 of 11 patients after placebo (P=NS). CONCLUSIONS: This first clinical study investigating the potential of GM-CSF to improve collateral flow in patients with coronary artery disease documents its efficacy in a short-term administration protocol.

Discordance between the binding affinity of mitogen-activated protein kinase subfamily members for MAP kinase phosphatase-2 and their ability to activate the phosphatase catalytically.

MKP-2 is a member of the mitogen-activated protein (MAP) kinase phosphatase family which has been suggested to play an important role in the feedback control of MAP kinase-mediated gene expression. Although MKP-2 preferentially inactivates extracellular signal-regulated kinase (ERK) and c-Jun NH(2)-terminal kinase (JNK) MAP kinase subfamilies, the mechanisms underlying its own regulation remain unclear. In this report, we have examined the MKP-2 interaction with and catalytic activation by distinct MAP kinase subfamilies. We found that the catalytic activity of MKP-2 was enhanced dramatically by ERK and JNK but was affected only minimally by p38. By contrast, p38 and ERK bound MKP-2 with comparably strong affinities, whereas JNK and MKP-2 interacted very weakly. Through site-directed mutagenesis, we defined the ERK/p38-binding site as a cluster of arginine residues in the NH(2)-terminal domain of MKP-2. Mutation of the basic motif abrogated its interaction with both ERK and p38 and severely compromised the catalytic activation of MKP-2 by these kinases. Unexpectedly, such mutations had little effect on JNK-triggered catalytic activation. Both in vitro and in vivo, wild type MKP-2 effectively inactivated ERK2 whereas MKP-2 mutants incapable of binding to ERK/p38 did not. Finally, in addition to its role as a docking site for ERK and p38, the MKP-2 basic motif plays a role in regulating its nuclear localization. Our studies provided a mechanistic explanation for the substrate preference of MKP-2 and suggest that catalytic activation of MKP-2 upon binding to its substrates is crucial for its function.

Diastolic dysfunction precedes myocardial hypertrophy in the development of hypertension.

BACKGROUND: Left ventricular (LV) hypertrophy and impaired diastolic function may occur early in systemic hypertension, but longitudinal studies are missing. METHODS: We performed an echocardiographic follow-up study in young initially normotensive male offspring of hypertensive (OHyp) (n = 25) and normotensive (ONorm) (n = 17) parents. Blood pressure (BP), LV mass, and mitral inflow were determined at baseline and after 5 years. Pulmonary vein flow pattern assessment and septal myocardial Doppler imaging were additionally performed at follow-up. RESULTS: At follow-up, BP was not significantly different between the two groups (128 +/- 11/84 +/- 10 v 123 +/- 11/81 +/- 5 mm Hg, OHyp v ONorm) but five OHyp had developed mild hypertension. LV mass index remained unchanged and was not different between the two groups at follow-up (92 +/- 17 v 92 +/- 14 g/m2). Diastolic echocardiographic properties were similar at baseline, but, at follow-up, the following differences were found: mitral E deceleration time (209 +/- 32 v 185 +/- 36 msec, P < .05) and pulmonary vein reverse A wave duration (121 +/- 15 v 107 +/- 12 msec, P < .05) were prolonged in the OHyp as compared to the ONorm. Compared to the normotensive subjects, the five OHyp who developed hypertension had more pronounced alterations of LV diastolic function, that is, significantly higher mitral A (54 +/- 7 v 44 +/- 9 cm/sec, hypertensives v normotensives, P < .05), lower E/A ratio (1.31 +/- 0.14 v 1.82 +/- 0.48, P < .05), increased systolic-to-diastolic pulmonary vein flow ratio (1.11 +/- 0.3 v 0.81 +/- 0.16, P < .005), longer myocardial isovolumic relaxation time (57 +/- 7 v 46 +/- 12 msec, P < .05) as well as smaller myocardial E (10 +/- 1 v 13 +/- 2 cm/sec, P < .05) and E/A ratio (1.29 +/- 0.25 v 1.78 +/- 0.43, P < .05), despite similar LV mass (91 +/- 16 v 93 +/- 18 g/m2). CONCLUSIONS: Over a 5-year follow-up, initially lean, normotensive, young men with a moderate genetic risk for hypertension, developed Doppler echocardiographic alterations of LV diastolic function compared to matched offspring of normotensive parents. These alterations were more pronounced in the OHyp who developed mild hypertension and occurred without a distinct rise in LV mass.

Catalytic activation of mitogen-activated protein (MAP) kinase phosphatase-1 by binding to p38 MAP kinase: critical role of the p38 C-terminal domain in its negative regulation.

Mitogen-activated protein (MAP) kinase phosphatase-1 (MKP-1) is the archetypal member of the dual-specificity protein phosphatase family, the expression of which can be rapidly induced by a variety of growth factors and cellular stress. Since MKP-1 protein localizes in the nucleus, it has been suggested to play an important role in the feedback control of MAP kinase-regulated gene transcription. Recently it has been demonstrated that the interaction of several cytosolic MAP kinase phosphatases with MAP kinases can trigger the catalytic activation of the phosphatases. It is unclear whether such a regulatory mechanism can apply to nuclear MAP kinase phosphatases and serve as an additional apparatus for the feedback control of MAP kinase-mediated gene expression. Here we have shown that MKP-1 associates directly with p38 MAP kinase both in vivo and in vitro, and that this interaction enhances the catalytic activity of MKP-1. The point mutation Asp-316-->Asn in the C-terminus of p38, analogous to the ERK2 (extracellular-signal-regulated kinase 2) sevenmaker mutation, dramatically decreases its binding to MKP-1 and substantially compromises its stimulatory effect on the catalytic activity of this phosphatase. Consistent with its defective interaction with MKP-1, this p38 mutant also displays greater resistance to dephosphorylation by the phosphatase. Our studies provide the first example of catalytic activation of a nuclear MAP kinase phosphatase through direct binding to a MAP kinase, suggesting that such a regulatory mechanism may play an important role in the feedback control of MAP kinase signalling in the nuclear compartment.

Age-related decline in Ras/ERK mitogen-activated protein kinase cascade is linked to a reduced association between Shc and EGF receptor.

Numerous studies have demonstrated that the proliferative capacity of cells declines with age. Using rat primary hepatocytes as a model system, we recently demonstrated that this age-related decline in the proliferative response to mitogenic stimulation is associated with decreased activities of both extracellular signal-regulated kinase (ERK) and p70 S6 kinase (p70(S6k)). To unravel the molecular basis for age-related defects in the ERK pathway, we have now characterized the upstream signaling events that occur after epidermal growth factor (EGF) stimulation in young and aged hepatocytes. As previously noted for ERK, the activities of both MEK (the kinase immediately upstream of ERK) and Ras following EGF stimulation were significantly lower in aged hepatocytes. An examination of the EGF receptor (EGFR) revealed a similar amount of EGFR in the two age groups. Likewise, EGFR and Shc, an adaptor protein that plays a crucial role in linking EGFR to Ras activation, underwent tyrosine phosphorylation to a similar degree in both young and aged hepatocytes. However, in aged cells Shc was unable to form stable complexes with EGFR after EGF stimulation. Our results suggest that a decrease in the association between Shc and EGFR in aged cells underlies the age-related declines in the ERK signaling cascade and in proliferative capacity.

Transforming growth factor-beta 1 suppresses serum deprivation-induced death of A549 cells through differential effects on c-Jun and JNK activities.

Transforming growth factor (TGF)-beta1, a pleiotropic cytokine involved in regulating growth and differentiation, can exert both pro-apoptotic and anti-apoptotic effects depending on the cell type or circumstances. We observed that TGF-beta1 blocked apoptosis resulting from serum withdrawal in A549 human lung carcinoma cells. This was associated with suppression of JNK activation that occurs concomitant with the onset of apoptosis in the absence of TGF-beta1, suggesting that JNK plays an active role in the death process and that TGF-beta1 exerts its protective influence by altering JNK activity. Overexpression of a dominant negative mutant form of SEK1, an upstream activator of JNK, likewise suppressed JNK activation and inhibited apoptosis. Investigation of early events following TGF-beta1 treatment revealed an early induction and phosphorylation of c-Jun that was absent in cells subjected to serum withdrawal alone. That TGF-beta1-induced expression of c-Jun is important for survival was supported by the finding that overexpression of non-phosphosphorylatable dominant negative mutant c-Jun, c-Jun(S73A), attenuated the protective influence of TGF-beta1. Our findings suggest that JNK activation is a late but essential event in serum deprivation-induced apoptosis in A549 cells. TGF-beta1 prevents apoptosis, in part, through the early induction and phosphorylation of c-Jun, which in turn results in attenuated JNK activation.

Influence of the cellular redox state on NF-kappaB-regulated gene expression.

The redox state has been shown to regulate a variety of biochemical functions including cellular proliferation. Previous studies from our laboratory and others have shown that the binding of many transcription factors to their cognate DNA sequences is sensitive to the redox environment. Therefore, it is likely that redox status serves as an additional regulatory control for the activity of transcription factors and that this may mediate the redox regulation of proliferation. To assess this possibility, the influence of altering the redox state on NF-kappaB-regulated gene expression was studied. A more-reducing environment favored higher levels of expression of gro, an endogenous gene associated with proliferation, when the redox levels were changed either naturally by altering culture density or chemically by treatment with modulators of glutathione synthesis. Furthermore, nuclear runoff studies showed that a more-reducing redox increased transcription of gro. In order to ascertain the singular effect of the redox state on the activity of NF-kappaB, expression of a secreted alkaline phosphatase (SEAP) reporter gene solely under the control of an NF-kappaB response element was measured under varying redox conditions. Changes in the redox state modulated the expression of this reporter system. Taken together, these results suggest the involvement of a redox mechanism regulating signaling events operating through the control of gene expression by transcription factors.

HuR regulates p21 mRNA stabilization by UV light.

Expression of the cyclin-dependent kinase inhibitor p21 is highly induced by many stresses, including exposure to short-wavelength UV light (UVC), which increases p21 mRNA stability. Investigation into the mechanisms underlying this stabilization process revealed that proteins present in cytoplasmic lysates of human RKO colorectal carcinoma cells formed complexes with p21 mRNA that were inducible by treatment with UVC and other stress agents. The ubiquitous Elav-type RNA-binding protein HuR was identified within the p21 mRNA-protein complexes, as antibodies recognizing HuR supershifted these complexes and revealed HuR-immunoreactive proteins complexing with p21 mRNA on Western blots. Lowering of endogenous HuR levels through expression of antisense HuR decreased p21 RNA-protein complexes, greatly reduced the UVC inducibility and half-life of p21 mRNA, and prevented UVC-mediated induction of luciferase activity in p21 3' untranslated region-containing reporter constructs. Our findings indicate that HuR plays a major role in regulating stress-induced p21 expression by enhancing p21 mRNA stability and that these effects are coupled to HuR's elevated presence in the cytoplasm.

Redesigning nucleic acids.

A research program has applied the tools of synthetic organic chemistry to systematically modify the structure of DNA and RNA oligonucleotides to learn more about the chemical principles underlying their ability to store and transmit genetic information. Oligonucleotides (as opposed to nucleosides) have long been overlooked by synthetic organic chemists as targets for structural modification. Synthetic chemistry has now yielded oligonucleotides with 12 replicatable letters, modified backbones, and new insight into why Nature chose the oligonucleotide structures that she did.

Lupus anticoagulants: strong association with the major histocompatibility complex class II and platelet antibodies.

A relationship between the presence of platelet autoantibodies and major histocompatibilty complex class II alleles was determined in 27 patients with lupus anticoagulants. Twenty-two patients had a primary antiphospholipid syndrome' and five patients had lupus erythematosus (SLE). Platelet antibodies against the platelet glycoproteins (GP) IIb/IIIa were detectable in 20 patients. Anti-GPIb/IX or -GPIV antibodies were detectable only in patients with anti-GPIIb/IIIa antibodies. An increased frequency of HLA-DQB1*06 was demonstrable in the total patient population. The association between the lupus anticoagulants and HLA-DQB1*06 was even stronger if patients also had detectable platelet antibodies. This association was also seen if patients with a history of thromboembolic disease were considered separately. However, within the patient population there was no difference between frequencies of HLA alleles detectable platelet antibodies.

Specificities of platelet autoantibodies in patients with lupus anticoagulants in primary antiphospholipid syndrome.

We have studied target platelet antigens in 22 patients with lupus anticoagulants and a primary antiphospholipid syndrome in order to determine whether any specificities of platelet autoantibodies are correlated with thromboembolism, and if these antibodies cross-react with phospholipids, which would suggest their role in the development of thromboembolic disease. Platelet counts were median 203 x 10(9)/l, range 100-298 x 10(9)/l. Platelet antibodies were found in six thrombocytopenic patients and in further nine patients. All these 15 patients had antibodies against GPIIb/ IIIa, five patients against GPIb/IX, and six patients against GPIV. Anti-GPIb/IX and -GPIV occurred only in combination with anti-GPIIb/IIIa antibodies. There was no correlation between the presence of detectable platelet antibodies or any of their glycoprotein specificity and thrombocytopenia or the history of a thromboembolic disease. Eluates from platelets contained only GPIIb/IIIa reactivities, but neither anti-GPIb/IX nor anti-GPIV. None of the eluates contained lupus anticoagulant activity. In one case, the platelet eluates contained anti-GPIIb/IIIa and anticardiolipin IgG antibodies. These results suggest that in patients with a primary antiphospholipid syndrome the presence of platelet autoantibodies neither indicate a risk for thromboembolic disorder nor have lupus anticoagulant activity.