Corrigendum to "Hydroxychloroquine Use in Lupus Patients during Pregnancy Is Associated with Longer Pregnancy Duration in Preterm Births".

[This corrects the article DOI: 10.1155/2017/2810202.].

Hydroxychloroquine Use in Lupus Patients during Pregnancy Is Associated with Longer Pregnancy Duration in Preterm Births.

OBJECTIVE: To investigate the effect of hydroxychloroquine (HCQ) in pregnant women with systemic lupus erythematosus (SLE). METHODS: In SLE pregnancies of a single Dutch center (2000-2015), lupus activity and flares before and during pregnancy and postpartum were assessed using the SLE Disease Activity Index (SLEDAI)/SLEPDAI (SLEDAI adjusted for pregnancy). The association between HCQ use and pregnancy outcomes (early spontaneous abortion, fetal death, and preterm and term live birth) was analyzed using generalized estimating equations (GEE) accounting for the occurrence of multiple pregnancies per patient. Analyses were adjusted for antiphospholipid antibody (aPL) status. RESULTS: 110 pregnancies (63 mostly Caucasian patients) were included, of which, in 30, HCQ was used; overall occurrence of flares was low (non-HCQ group: 5 mild (6.4%) and 2 severe (2.6%); HCQ group: 2 mild (6.7%) and no severe flares). The HCQ group showed a trend towards lower dosage of prednisone (OR 0.2 (95% CI 0.0-1.4); p = 0.10). Pregnancy outcomes were comparable between groups. Among preterm live births, pregnancy duration was significantly longer in HCQ users (2.4 weeks (95% CI 1.0-3.8; p ≤ 0.001)). CONCLUSION: HCQ use was associated with longer pregnancy duration in the vulnerable preterm birth population, underscoring the beneficial effect of HCQ use during pregnancy.

Morbidity and mortality in the antiphospholipid syndrome during a 10-year period: a multicentre prospective study of 1000 patients.

OBJECTIVES: To assess the prevalence of the main causes of morbi-mortality in the antiphospholipid syndrome (APS) during a 10-year-follow-up period and to compare the frequency of early manifestations with those that appeared later. METHODS: In 1999, we started an observational study of 1000 APS patients from 13 European countries. All had medical histories documented when entered into the study and were followed prospectively during the ensuing 10 years. RESULTS: 53.1% of the patients had primary APS, 36.2% had APS associated with systemic lupus erythematosus and 10.7% APS associated with other diseases. Thrombotic events appeared in 166 (16.6%) patients during the first 5-year period and in 115 (14.4%) during the second 5-year period. The most common events were strokes, transient ischaemic attacks, deep vein thromboses and pulmonary embolism. 127 (15.5%) women became pregnant (188 pregnancies) and 72.9% of pregnancies succeeded in having one or more live births. The most common obstetric complication was early pregnancy loss (16.5% of the pregnancies). Intrauterine growth restriction (26.3% of the total live births) and prematurity (48.2%) were the most frequent fetal morbidities. 93 (9.3%) patients died and the most frequent causes of death were severe thrombosis (36.5%) and infections (26.9%). Nine (0.9%) cases of catastrophic APS occurred and 5 (55.6%) of them died. The survival probability at 10 years was 90.7%. CONCLUSIONS: Patients with APS still develop significant morbidity and mortality despite current treatment. It is imperative to increase the efforts in determining optimal prognostic markers and therapeutic measures to prevent these complications.

Induction therapy with short-term high-dose intravenous cyclophosphamide followed by mycophenolate mofetil in proliferative lupus nephritis.

BACKGROUND: For decades, high-dose intravenous cyclophosphamide (ivCY) given for 24-30 months was regarded as the standard therapy for proliferative lupus nephritis, despite serious side effects. Our aim was to evaluate the effect of induction therapy with short-term high-dose ivCY followed by mycophenolate mofetil (MMF) on disease parameters, mortality and health-related quality of life (HRQoL) in patients with proliferative lupus nephritis. METHODS: Between January 2003 and November 2006, 71 patients with biopsy-proven proliferative lupus nephritis were included in the second Dutch Lupus Nephritis Study. All patients were treated with ivCY (750 mg÷m2, six monthly pulses) plus oral prednisone, followed by MMF (2000 mg÷day) plus oral prednisone for 18 months, and then azathioprine (2 mg÷kg÷day) plus oral prednisone. Study endpoints included the occurrence of renal relapse, end-stage renal disease (ESRD) and mortality. RESULTS: After a median follow-up of 3.8 years (range 0.1-4.5), four (5.6%) of the 71 patients had a renal relapse, one (1.4%) failed treatment, one (1.4%) reached ESRD, and two (2.8%) died. Systemic lupus erythematosus (SLE) Disease Activity Index, serum creatinine, proteinuria and antibodies against anti-dsDNA decreased significantly during treatment and serum levels of complement factor 3 and 4 increased significantly. Furthermore, six of eight domains of the Short Form-36 as well as the number of symptoms and total distress level according to the SLE Symptom Checklist improved significantly over time. CONCLUSIONS: This open-label study shows that induction therapy with short-term (six monthly pulses) high-dose ivCY followed by MMF is effective in preventing renal relapses, ESRD and mortality and improving HRQoL in patients with proliferative lupus nephritis.

Serious infections in systemic lupus erythematosus with a focus on pneumococcal infections.

BACKGROUND: Infections are important denominators of morbidity and mortality in patients with systemic lupus erythematosus (SLE). Pneumococcus pneumoniae has been identified as a relatively frequent cause of serious infections in SLE and vaccination against this pathogen is possible. We analysed the incidence of serious infections in a cohort of SLE patients, focussing on Streptococcus pneumoniae. METHODS: We retrospectively screened the medical records of all SLE patients who were regularly seen in the outpatient clinic of our department between January 2010 and December 2012. We registered all infections that necessitated admission to the hospital (serious infection) and compared relevant clinical and laboratory parameters and immunomodulating/immunosuppressive treatment in patients with and without serious infections. RESULTS: In the total cohort of 260 patients, there were 132 episodes of serious infection in 70 patients, with a median follow-up per patient of 11.4 years (range 0 to 50.2 years). S. pneumoniae accounted for 11/132 (8.3%) serious infection episodes and eight of 11 episodes were invasive. With a follow-up of 3970.6 years for the total cohort, this leads to an incidence of 201/100.000 patient-years. In the multivariate analysis neither clinical parameters nor use of immunosuppressive drugs correlated with occurrence of serious infections. CONCLUSIONS: Compared to the incidence of invasive pneumococcal infections in the Dutch population (15.6/100.000 patient years), the incidence in SLE patients is 13 times higher. This, in combination with the absence of a relation to use of immunosuppressive drugs, is a strong argument to recommend vaccination against S. pneumoniae in all SLE patients.

Fatigue in patients with systemic lupus erythematosus: the role of dehydroepiandrosterone sulphate.

Fatigue is a major problem in systemic lupus erythematosus (SLE), but the physiological substrate of this fatigue is largely unclear. To examine if low levels of dehydroepiandrosterone (DHEA) and its sulphate DHEAS play a role in SLE fatigue, we compared: 1) DHEAS levels and fatigue between 60 female patients with SLE with low disease activity (31 using, 29 not using prednisone) and 60 age-matched healthy women, and 2) fatigue between patients with SLE with low and normal DHEAS levels. Serum DHEAS levels were determined with an Advantage Chemiluminescense System. The Multidimensional Fatigue Inventory (MFI) was used to assess fatigue. Patients were more fatigued (p ≤ 0.001) than healthy women and more often had below-normal DHEAS levels (p < 0.001). Patients using prednisone with low and normal DHEAS levels reported a similar level of fatigue (p ≥ 0.39). Patients with low DHEAS levels not using prednisone reported less fatigue than those with normal DHEAS levels (p ≤ 0.03). Thus, our results indicate that low DHEAS levels in SLE are not - or even inversely - related to fatigue. After our previous finding that DHEA administration does not reduce fatigue, this result further indicates that low serum DHEA(S) levels alone do not offer an explanation for SLE fatigue.

Dutch guidelines for diagnosis and therapy of proliferative lupus nephritis.

Proliferative lupus nephritis is a strong predictor of morbidity and mortality in patients with systemic lupus erythematosus. Despite improvements in the management of lupus nephritis, a significant number of the patients do not respond to immunosuppressive therapy and progress to end-stage renal failure. In order to optimise the diagnostic strategy and treatment of patients with proliferative lupus nephritis, guidelines are needed. In this review, the Dutch Working Party on Systemic Lupus Erythematosus provides recommendations regarding four important areas in patients with proliferative lupus nephritis: I) indications for a first renal biopsy, II ) definitions of treatment response, III ) selection of treatment options, and IV) indications for a repeat biopsy.

Pathophysiology of thrombotic APS: where do we stand?

The antiphospholipid syndrome (APS) is diagnosed when patients with thrombotic complications or foetal losses have elevated levels of antiphospholipid antibodies in their plasmas. The term APS is confusing, because the pathogenic auto-antibodies are not directed against phospholipids but towards a plasma protein, ß(2)-glycoprotein I. For many years the reason why auto-antibodies against ß(2)-glycoprotein I were pro-thrombotic was unclear, because man and mice deficient in ß(2)-glycoprotein I do not express a clear phenotype. Animal models in which passive transfer of patient antibodies into mice resulted in an increased thrombotic response have provided novel insights in the importance of this protein in the pathology of APS.

Receptor for advanced glycation end products (RAGE) polymorphisms are associated with systemic lupus erythematosus and disease severity in lupus nephritis.

OBJECTIVE: Interaction of advanced glycation end products (AGEs) with their receptors (RAGE) plays an important role in inflammation in auto-immune diseases. Several functional polymorphisms of RAGE have been described. In this study we analysed the role of RAGE polymorphisms in disease susceptibility for systemic lupus erythematosus (SLE). In addition, we investigated whether these polymorphisms in SLE are associated with serum levels of soluble RAGE (sRAGE), renal involvement (lupus nephritis (LN)) and its outcome. METHODS: For this cross-sectional study DNA samples of 97 SLE patients, 114 LN patients and 429 healthy controls (HC) were genotyped for four RAGE polymorphisms: -429 T/C, -374 T/A, 2184 A/G and Gly82Ser. Differences in genotype frequencies and allele frequencies were tested between patients and HCs. In SLE patients, sRAGE was measured by enzyme-linked immunosorbent assay (ELISA). In addition, association of genotypes with sRAGE and disease severity in LN was analysed. RESULTS: The C allele of -429 T/C, the T allele of -374 T/A and the G allele of 2184 A/G were significantly more prevalent in SLE and LN compared with HC. In LN, the C allele of RAGE -429 T/C, the A allele of -374 T/A and the G allele of RAGE 2184 A/G polymorphism were significantly associated with more proteinuria and worse renal function during the first two years of treatment. No association of genotype with sRAGE was found. CONCLUSION: RAGE polymorphisms are associated with susceptibility to SLE and LN. In addition, some of these polymorphisms are likely to be associated with disease severity and initial response to treatment in LN.

Induction of anti-ß2 -glycoprotein I autoantibodies in mice by protein H of Streptococcus pyogenes.

BACKGROUND: The antiphospholipid syndrome (APS) is characterized by the persistent presence of anti-ß(2) -glycoprotein I (ß(2) -GPI) autoantibodies. ß(2) -GPI can exist in two conformations. In plasma it is a circular protein, whereas it adopts a fish-hook conformation after binding to phospholipids. Only the latter conformation is recognized by patient antibodies. ß(2) -GPI has been shown to interact with Streptococcus pyogenes. OBJECTIVE: To evaluate the potential of S. pyogenes-derived proteins to induce anti-ß(2) -GPI autoantibodies. METHODS AND RESULTS: Four S. pyogenes surface proteins (M1 protein, protein H, streptococcal collagen-like protein A [SclA], and streptococcal collagen-like protein B [SclB]) were found to interact with ß(2) -GPI. Only binding to protein H induces a conformational change in ß(2) -GPI, thereby exposing a cryptic epitope for APS-related autoantibodies. Mice were injected with the four proteins. Only mice injected with protein H developed antibodies against the patient antibody-related epitope in domain I of ß(2) -GPI. Patients with pharyngotonsillitis caused by S. pyogenes who developed anti-protein H antibodies also generated anti-ß(2) -GPI antibodies. CONCLUSIONS: Our study has demonstrated that a bacterial protein can induce a conformational change in ß(2) -GPI, resulting in the formation of antiß(2) -GPI autoantibodies. This constitutes a novel mechanism for the formation of anti-ß(2) -GPI autoantibodies.

Serum dehydroepiandrosterone sulphate levels and laboratory and clinical parameters indicating expression of disease are not associated with fatigue, well-being and functioning in patients with primary Sjögren's syndrome.

OBJECTIVES: The aim of this study was to compare serum dehydroepiandrosterone sulphate (DHEAS) levels and clinical and laboratory parameters reflecting expression of disease between female patients with primary Sjögren's syndrome (pSS) and age-matched healthy women and to examine in pSS patients the correlation of these variables with fatigue, well-being, and functioning. METHODS: Comparisons were made between 60 female pSS patients and 60 age-matched healthy women. We assessed questionnaire scores of general fatigue, depressed mood, mental wellbeing, and physical functioning, tear production (Schirmer I test), tender point counts, serum DHEAS level, haemoglobin concentration, erythrocyte sedimentation rate, and serum immunoglobulin G. RESULTS: As compared to healthy participants, patients had more fatigue and depressed mood, reduced well-being and functioning, more dryness and pain, lower serum DHEAS levels, and more expression of disease as reflected by laboratory assessments (p≤0.001). In pSS patients, fatigue, well-being, and functioning correlated with tender point counts, but not with the extent of dryness and also not with laboratory assessments including serum DHEAS levels. CONCLUSIONS: The high prevalence of fatigue and reduced functioning in pSS patients might suggest a mediating role of generalised autoimmune processes. In the present study, clinical observations and laboratory assessments are not correlated with persistent fatigue and reduced functioning. Our results suggest that treatment of fatigue, well-being, and functioning, should target other variables than those examined in this study, preferably psychological variables or perhaps specific immunologic parameters.

Patient-derived monoclonal antibodies directed towards beta2 glycoprotein-1 display lupus anticoagulant activity.

BACKGROUND: Patients with antiphospholipid syndrome (APS) display a heterogeneous population of antibodies with beta(2) glycoprotein-1 (ß(2)GP1) as the major antigen. OBJECTIVES: We isolated and characterized human mAbs directed against ß(2)GP1 from the immune repertoire of APS patients. METHODS: Variable heavy chain repertoires from B cells from two APS patients with anti-ß(2)GP1 antibodies were cloned into the pHEN1-VLrep vector. Constructed full-length IgG antibodies were tested for lupus anticoagulant (LAC) activity and binding to ß(2)GP1 and its domains. RESULTS: Two clones of each patient were selected on the basis of the reactivity of single chain Fv (scFv) fragments displayed on phages towards full-length ß(2)GP1 and its isolated domain I. The affinity of selected antibodies for ß(2)GP1 was lost when transforming from phages to monovalent scFvs, and was regained when antibodies were constructed as complete IgG, indicating a role for bivalency in binding to ß(2)GP1. Both selected clones from patient 2 recognized domain I of ß(2)GP1, and for both clones selected from patient 1, binding required the presence of both domain I and domain II. All mAbs displayed LAC activity in both activated partial thromboplastin time-based and dilute Russell's viper venom test-based clotting assays and in thrombin generation. CONCLUSIONS: In this study, we show successful cloning of patient-derived mAbs that require domain I of ß(2)GP1 for binding, and that display LAC activity that is dependent on their affinity for ß(2)GP1. These antibodies can help us to gain more insights into the pathogenesis of APS, and may facilitate standardization of APS diagnosis.

An international multicentre-laboratory evaluation of a new assay to detect specifically lupus anticoagulants dependent on the presence of anti-beta2-glycoprotein autoantibodies.

BACKGROUND: Antiphospholipid syndrome (APS) is diagnosed by the simultaneous presence of vascular thrombosis and/or pregnancy morbidity and detection of antiphospholipid antibodies in plasma. OBJECTIVES: We have shown that prolongation of clotting time by anti-beta2-glycoprotein I (beta2GPI) antibodies correlates better with thrombosis than a positive classic lupus anticoagulant (LAC) assay in a single center study. To confirm or falsify this finding we have conducted a multicenter study. METHODS AND RESULTS: In 325 LAC-positive samples, we found that the beta2GPI-dependent LAC correlated 2.0 times better with thrombosis than the classic LAC assay. Although significant, this was a minimal improvement compared with the 'classic' LAC. It was published that calcium influences the behavior of anti-beta2GPI antibodies in coagulation assays. To investigate whether calcium plays a role in the present study, we divided the patient population into two groups: (i) blood was collected in 0.109 m sodium citrate and (ii) blood was drawn in 0.129 m sodium citrate as anticoagulant. We found that a positive result with the beta2GPI-dependent LAC assay correlated better with thrombosis [odds ratio (OR): 3.3, 95% confidence interval (CI) 1.9-5.8] when 0.109 m sodium citrate was used compared with 0.129 m sodium citrate (OR: 0.4, 95% CI 0.1-1.1). CONCLUSION: We were able to confirm in an international multicenter study that a positive result in a beta2GPI-dependent LAC assay correlates better with thrombosis than the classic LAC assay, but that the assay needs further study as it is sensitive to external factors such as the sodium citrate concentration used as anticoagulant in the test sample.

Variability of fatigue during the day in patients with primary Sjögren's syndrome, systemic lupus erythematosus, and rheumatoid arthritis.

OBJECTIVES: Fatigue is a common complaint of patients with primary Sjögren's syndrome (pSS), systemic lupus erythematosus (SLE), and rheumatoid arthritis (RA). The aim of this study was to examine and compare in patients with these diseases the course of fatigue within the first hour after awakening and during the day, and to examine sleep disturbance as a potential determinant of fatigue. METHODS: Eight repeated measurements at 5 fatigue dimensions were assessed on 2 consecutive days in the natural environment of female patients with pSS (n=29), SLE (n=23), RA (n=19), and healthy women (n=52). Sleep disturbance of the previous night was assessed. Fatigue levels and the change of fatigue after awakening and during the day were analysed with analyses of variance (adjusted for age). RESULTS: The patients showed significantly elevated levels at all fatigue dimensions as compared to healthy participants. Fatigue levels decreased in the first hour after awakening in patients with SLE and RA, but increased or did not change in patients with pSS. Fatigue progressively increased during the remainder of the day for all patient groups. Sleep disturbance correlated with overall fatigue levels, but hardly with the change of fatigue within the first hour after awakening. CONCLUSIONS: Our study confirms the presence of increased fatigue in patients with pSS, SLE, and RA. Patients with pSS failed to show a decrease in fatigue in the first hour after awakening. Future research should examine the causes of this difference in fatigue after awakening.

The role of LRP8 (ApoER2') in the pathophysiology of the antiphospholipid syndrome.

One of the greatest enigmas in thrombosis research is the observation that one can diagnose a person with a thrombotic risk with a prolongation of the clotting time. Our textbooks have taught us that prolongation of clotting correlates with a tendency to bleed. To confuse our textbook knowledge further, the same patients often have a prolonged bleeding time, a diagnostic test to detect a dysfunction in primary haemostasis. In this paper we critically review the literature that tries to explain the contradiction that exists between in-vitro diagnostic tests and the observed clinical manifestations and discuss our current opinion on how antiphospholipid antibodies can disturb the haemostatic balance.

Towards evidence-based treatment of thrombotic antiphospholipid syndrome.

Thrombosis in the presence of persistently positive tests for antiphospholipid antibodies is termed thrombotic antiphospholipid syndrome (APS). At present, 'standard' secondary thromboprophylaxis in thrombotic APS is treatment with moderate intensity oral anticoagulants for life after a first venous thrombosis and with high intensity oral anticoagulation after non-embolic ischaemic stroke. These recommendations differ from those applied in the general population, where a restricted period of anticoagulation is common practice after venous thrombosis and antiplatelet drugs are the first choice after ischaemic stroke. From an extensive literature review we conclude that the available data are insufficient to apply a different strategy for secondary thromboprophylaxis in patients with thrombotic APS than the one that holds for the general population.

Effects of dehydroepiandrosterone on fatigue and well-being in women with quiescent systemic lupus erythematosus: a randomised controlled trial.

OBJECTIVE: Dehydroepiandrosterone (DHEA) has been reported to improve fatigue and reduced well-being. Both are major problems in patients with systemic lupus erythematosus (SLE), even with quiescent disease. Low serum DHEA levels are common in SLE. The present work investigates the effects of DHEA administration on fatigue, well-being and functioning in women with inactive SLE. METHODS: In a double-blind, randomised, placebo-controlled study, 60 female patients with inactive SLE received 200 mg oral DHEA or placebo. Primary outcome measures were general fatigue, depressive mood, mental well-being and physical functioning. Assessments were made before treatment, after 3, 6 and 12 months on medication, and 6 months after cessation of treatment. RESULTS: Patients from the DHEA and placebo group improved on general fatigue (p<0.001) and mental well-being (p=0.04). There was no differential effect of DHEA. The belief that DHEA had been used was a stronger predictor for improvement of general fatigue than the actual use of DHEA (p=0.04). CONCLUSIONS: The trial does not indicate an effect of daily 200 mg oral DHEA on fatigue and well-being, and therefore DHEA treatment is not recommended in unselected female patients with quiescent SLE. Clinical Trials Registration Number NCT00391924.

Morbidity and mortality in the antiphospholipid syndrome during a 5-year period: a multicentre prospective study of 1000 patients.

OBJECTIVES: To identify the main causes of morbidity and mortality in patients with antiphospholipid syndrome (APS) during a 5-year period and to determine clinical and immunological parameters with prognostic significance. METHODS: The clinical and immunological features of a cohort of 1000 patients with APS from 13 European countries who had been followed up from 1999 to 2004 were analysed. RESULTS: 200 (20%) patients developed APS-related manifestations during the 5-year study period. Recurrent thrombotic events appeared in 166 (16.6%) patients and the most common were strokes (2.4% of the total cohort), transient ischaemic attacks (2.3%), deep vein thromboses (2.1%) and pulmonary embolism (2.1%). When the thrombotic events occurred, 90 patients were receiving oral anticoagulants and 49 were using aspirin. 31/420 (7.4%) patients receiving oral anticoagulants presented with haemorrhage. 3/121 (2.5%) women with only obstetric APS manifestations at the start of the study developed a new thrombotic event. A total of 77 women (9.4% of the female patients) had one or more pregnancies and 63 (81.8% of pregnant patients) had one or more live births. The most common fetal complications were early pregnancy loss (17.1% of pregnancies) and premature birth (35% of live births). 53 (5.3% of the total cohort) patients died. The most common causes of death were bacterial infection (21% of deaths), myocardial infarction (19%) and stroke (13%). No clinical or immunological predictor of thrombotic events, pregnancy morbidity or mortality was detected. CONCLUSION: Patients with APS still develop significant morbidity and mortality despite current treatment (oral anticoagulants or antiaggregants, or both).

Platelets and the antiphospholipid syndrome.

The antiphospholipid syndrome is a non-inflammatory autoimmune disease characterised by the presence of antiphospholipid antibodies in the plasma of patients with venous or arterial thrombosis or recurrent complications of pregnancy. The strong relation between the presence of antibodies against anionic phospholipids and thrombo-embolic complications is well established, but how the presence of antiphospholipid antibodies results in the observed clinical manifestations remains a mystery. Experimental observations suggest that an altered regulation of platelet function can cause the thrombotic complications observed in the antiphospholipid syndrome. In this review, we will discuss the evidence that the platelet is an important player in the pathogenesis of the antiphospholipid syndrome.

Pregnancy, chimerism and lupus nephritis: a multi-centre study.

Chimerism occurs twice as often in the kidneys of women with lupus nephritis as in normal kidneys and may be involved in the pathogenesis of systemic lupus erythematosus. Pregnancy is considered the most important source of chimerism, but the exact relationship between pregnancy, the persistence of chimeric cells and the development of systemic lupus erythematosus has not been investigated. Renal biopsies and clinical data from patients in the First Dutch Lupus Nephritis Study were used. Chimeric cells were identified by in-situ hybridization of the Y chromosome. A questionnaire was used to obtain detailed reproductive data including pregnancy history and miscarriages. Chimerism was found in 12 of 26 (46%) renal biopsies. Of the 12 chimeric women, 5 reported a pregnancy; of 14 women who were not chimeric, 8 reported a pregnancy. Chimeric women who had been pregnant reported significantly more pregnancies than non-chimeric women who had been pregnant (P=0.04). The median age of the youngest child was higher in chimeric women (19 years) than in non-chimeric women (6 years). Despite the attention given to pregnancy histories with respect to chimerism, this study shows that in patients with systemic lupus erythematosus, a clear-cut relationship is not apparent. A considerable number of chimeric women did not report a pregnancy: in these women, other sources of chimerism must be considered. Our data support the theory that only certain subsets of chimeric cells persist into the maternal circulation after pregnancy.