Salivary dysbiosis and the clinical spectrum in anti-Ro positive mothers of children with neonatal lupus.

Mothers giving birth to children with manifestations of neonatal lupus (NL) represent a unique population at risk for the development of clinically evident pathologic autoimmunity since many are asymptomatic and only become aware of anti-SSA/Ro positivity (anti-Ro+) based on heart block in their fetus. Accordingly, we hypothesized that the microbiome in saliva is associated with the development of autoreactivity and in some cases the progression in health status from benign to overt clinical disease including Sjögren's syndrome (SS) and systemic lupus erythematosus (SLE). The study comprised a clinical spectrum of anti-Ro+ mothers, all of whom gave birth to a child with NL: 9 were asymptomatic or had an undifferentiated autoimmune disease (Asym/UAS) and 16 fulfilled criteria for SS and/or SLE. Microbial diversity was reduced across all levels from kingdom to species for the anti-Ro+ mothers vs healthy controls; however, there were no significant differences between Asym/UAS and SS/SLE mothers. Relative abundance of Proteobacteria and more specifically class Betaproteobacteria decreased with clinical severity (healthy controls < Asym/UAS < SS/SLE). These ordered differences were maintained through the taxonomic hierarchy to three genera (Lautropia, Comamonas, and Neisseria) and species within these genera (L. mirabilis, N. flavescens and N. oralis). Biometric analysis comparing von Willebrand Factor domains present in human Ro60 with L. mirabilis proteins support the hypothesis of molecular mimicry. These data position the microbiome in the development of anti-Ro reactivity and subsequent clinical spectrum of disease.

Keeping upbeat to prevent the heartbreak of anti-Ro/SSA pregnancy.

Linked Comment: Ultrasound Obstet Gynecol 2019; 54: 87-95.

Study of Flare Assessment in Systemic Lupus Erythematosus Based on Paper Patients.

OBJECTIVE: To determine the level of agreement of disease flare severity (distinguishing severe, moderate, and mild flare and persistent disease activity) in a large paper-patient exercise involving 988 individual cases of systemic lupus erythematosus. METHODS: A total of 988 individual lupus case histories were assessed by 3 individual physicians. Complete agreement about the degree of flare (or persistent disease activity) was obtained in 451 cases (46%), and these provided the reference standard for the second part of the study. This component used 3 flare activity instruments (the British Isles Lupus Assessment Group [BILAG] 2004, Safety of Estrogens in Lupus Erythematosus National Assessment [SELENA] flare index [SFI] and the revised SELENA flare index [rSFI]). The 451 patient case histories were distributed to 18 pairs of physicians, carefully randomized in a manner designed to ensure a fair case mix and equal distribution of flare according to severity. RESULTS: The 3-physician assessment of flare matched the level of flare using the 3 indices, with 67% for BILAG 2004, 72% for SFI, and 70% for rSFI. The corresponding weighted kappa coefficients for each instrument were 0.82, 0.59, and 0.74, respectively. We undertook a detailed analysis of the discrepant cases and several factors emerged, including a tendency to score moderate flares as severe and persistent activity as flare, especially when the SFI and rSFI instruments were used. Overscoring was also driven by scoring treatment change as flare, even if there were no new or worsening clinical features. CONCLUSION: Given the complexity of assessing lupus flare, we were encouraged by the overall results reported. However, the problem of capturing lupus flare accurately is not completely solved.

The prevalence and determinants of anti-DFS70 autoantibodies in an international inception cohort of systemic lupus erythematosus patients.

Autoantibodies to dense fine speckles 70 (DFS70) are purported to rule out the diagnosis of SLE when they occur in the absence of other SLE-related autoantibodies. This study is the first to report the prevalence of anti-DFS70 in an early, multinational inception SLE cohort and examine demographic, clinical, and autoantibody associations. Patients were enrolled in the Systemic Lupus International Collaborating Clinics (SLICC) inception cohort within 15 months of diagnosis. The association between anti-DFS70 and multiple parameters in 1137 patients was assessed using univariate and multivariate logistic regression. The frequency of anti-DFS70 was 7.1% (95% CI: 5.7-8.8%), while only 1.1% (95% CI: 0.6-1.9%) were monospecific for anti-DFS70. In multivariate analysis, patients with musculoskeletal activity (Odds Ratio (OR) 1.24 [95% CI: 1.10, 1.41]) or with anti-ß2 glycoprotein 1 (OR 2.17 [95% CI: 1.22, 3.87]) were more likely and patients with anti-dsDNA (OR 0.53 [95% CI: 0.31, 0.92]) or anti-SSB/La (OR 0.25 [95% CI: 0.08, 0.81]) were less likely to have anti-DFS70. In this study, the prevalence of anti-DFS70 was higher than the range previously published for adult SLE (7.1 versus 0-2.8%) and was associated with musculoskeletal activity and anti-ß2 glycoprotein 1 autoantibodies. However, 'monospecific' anti-DFS70 autoantibodies were rare (1.1%) and therefore may be helpful to discriminate between ANA-positive healthy individuals and SLE.

Autoimmune congenital heart block: complex and unusual situations.

Autoimmune congenital heart block (ACHB) is an immune-mediated cardiac disease included among the manifestations collectively referred to as neonatal lupus. The placental transference of maternal Ro/La autoantibodies may damage the conduction tissues during fetal development leading to blocking of signal conduction at the atrioventricular (AV) node in an otherwise structurally normal heart. Irreversible complete AV block is the main cardiac manifestation of ACHB, but some babies may develop endocardial fibroelastosis, valvular insufficiency, and/or frank cardiomyopathies with significantly reduced cardiac function requiring transplant. The severity of ACHB is illustrated by a global mortality rate of 20% and pacemaker rates of at least 64%, often within the first year of life. This review analyses the main complex and/or unusual clinical situations associated with ACHB, including unusual maternal immunological profiles, infrequent maternal autoimmune diseases, cardiac damage unrelated to AV block, fetal invasive management, late complications after birth, risk of congenital heart block (CHB) in ovodonation and in vitro fertilization techniques, the role of maternal features other than autoimmunity, the influence of the birth order or the risk of CHB in twins and triplets.

Efficacy and safety of subcutaneous tabalumab, a monoclonal antibody to B-cell activating factor, in patients with systemic lupus erythematosus: results from ILLUMINATE-2, a 52-week, phase III, multicentre, randomised, double-blind, placebo-controlled study.

OBJECTIVES: To evaluate the efficacy and safety of tabalumab, a human IgG4 monoclonal antibody that neutralises membrane and soluble B-cell activating factor (BAFF). METHODS: This randomised, placebo-controlled study enrolled 1124 patients with moderate-to-severe systemic lupus erythematosus (SLE) (Safety of Estrogens in Lupus Erythematosus National Assessment- SLE Disease Activity Index ≥6 at baseline). Patients received standard of care plus subcutaneous study drug, starting with a loading dose (240 mg) at week 0 and followed by 120 mg every 2 weeks (120 Q2W), 120 mg every 4 weeks (120 Q4W) or placebo. Primary endpoint was proportion achieving SLE Responder Index 5 (SRI-5) improvement at week 52. RESULTS: Clinical characteristics were balanced across groups. The primary endpoint was met with 120 Q2W (38.4% vs 27.7%, placebo; p=0.002), but not with the less frequent 120 Q4W regimen (34.8%, p=0.051). Although key secondary endpoints (time to severe flare, corticosteroid sparing and fatigue) were not met, patients treated with tabalumab had greater SRI-5 response rates in a serologically active subset and improvements in more stringent SRI cut-offs, SELENA-SLEDAI, Physician's Global Assessment, anti-double-stranded DNA antibodies, complement, total B cells and immunoglobulins. The incidences of deaths, serious adverse events (AEs), and treatment-emergent AEs were similar in the 120 Q2W, 120 Q4W and placebo groups, but depression and suicidal ideation, albeit rare events, were more commonly reported with tabalumab. CONCLUSION: SRI-5 was met with 120 Q2W and although key secondary endpoints were not met, numerous other secondary endpoints significantly improved in addition to pharmacodynamic evidence of BAFF pathway blockade. The safety profile for tabalumab was similar to placebo, except for depression and suicidality, which were uncommon. TRIAL REGISTRATION NUMBER: NCT01205438.

Anti-C1q antibodies in systemic lupus erythematosus.

OBJECTIVE: Anti-C1q has been associated with systemic lupus erythematosus (SLE) and lupus nephritis in previous studies. We studied anti-C1q specificity for SLE (vs rheumatic disease controls) and the association with SLE manifestations in an international multicenter study. METHODS: Information and blood samples were obtained in a cross-sectional study from patients with SLE (n = 308) and other rheumatologic diseases (n = 389) from 25 clinical sites (84% female, 68% Caucasian, 17% African descent, 8% Asian, 7% other). IgG anti-C1q against the collagen-like region was measured by ELISA. RESULTS: Prevalence of anti-C1q was 28% (86/308) in patients with SLE and 13% (49/389) in controls (OR = 2.7, 95% CI: 1.8-4, p < 0.001). Anti-C1q was associated with proteinuria (OR = 3.0, 95% CI: 1.7-5.1, p < 0.001), red cell casts (OR = 2.6, 95% CI: 1.2-5.4, p = 0.015), anti-dsDNA (OR = 3.4, 95% CI: 1.9-6.1, p < 0.001) and anti-Smith (OR = 2.8, 95% CI: 1.5-5.0, p = 0.01). Anti-C1q was independently associated with renal involvement after adjustment for demographics, ANA, anti-dsDNA and low complement (OR = 2.3, 95% CI: 1.3-4.2, p < 0.01). Simultaneously positive anti-C1q, anti-dsDNA and low complement was strongly associated with renal involvement (OR = 14.9, 95% CI: 5.8-38.4, p < 0.01). CONCLUSIONS: Anti-C1q was more common in patients with SLE and those of Asian race/ethnicity. We confirmed a significant association of anti-C1q with renal involvement, independent of demographics and other serologies. Anti-C1q in combination with anti-dsDNA and low complement was the strongest serological association with renal involvement. These data support the usefulness of anti-C1q in SLE, especially in lupus nephritis.

Discordant spectrum of cardiac manifestations of neonatal lupus in twins.

Congenital complete heart block associated with transplacental passage of maternal autoantibodies reactive with SSA/Ro and SSB/La is a rare disease with significant fetal, neonatal, and childhood morbidity and mortality. We present the case of dichorionic, diamniotic twins (female twin A and male twin B) exposed to maternal Ro and La autoantibodies with different disease expression. Twin A (female) had Mobitz type I second degree atrioventricular (AV) block (Wenckebach); twin B (male) had normal sinus rhythm. Both twins had structurally normal hearts but demonstrated echocardiographic evidence of endocardial fibroelastosis (EFE). Following maternal dexamethasone 4 mg once daily, twin A reverted to sinus rhythm in utero; twin B remained in sinus rhythm throughout pregnancy. Echocardiograms after delivery demonstrated resolution of EFE in both fetuses, and EKGs confirmed sinus rhythm. However, at five months of age, Holter monitor demonstrated first degree AV block and intermittent Wenckebach in twin A. Twin B remains in sinus rhythm. This case is one of only three in the literature that describes Mobitz type I second degree atrioventricular block presenting in fetuses exposed to maternal SSA and SSB autoantibodies and is the first case that we have seen reported in twins. Importantly, this case also adds to the growing body of literature describing EFE as a presentation of neonatal lupus with or without conduction system abnormalities, emphasizes the spectrum of cardiac conduction abnormalities in neonatal lupus syndrome, and raises interesting questions about discordant disease expression in twins.

Autoantibodies in systemic lupus erythematosus: comparison of historical and current assessment of seropositivity.

Systemic lupus erythematosus (SLE) is characterized by multiple autoantibodies and complement activation. Recent studies have suggested that anti-nuclear antibody (ANA) positivity may disappear over time in some SLE patients. Anti-double-stranded DNA (dsDNA) antibody titers and complement levels may vary with time and immunosuppressive treatment, while the behavior of anti-extractable nuclear antigen (ENA) over time is less well understood. This study sought to determine the correlation between historical autoantibody tests and current testing in patients with SLE. Three hundred and two SLE patients from the ACR Reclassification of SLE (AROSE) database with both historical and current laboratory data were selected for analysis. The historical laboratory data were compared with the current autoantibody tests done at the reference laboratory and tested for agreement using percent agreement and Kappa statistic. Serologic tests included ANA, anti-dsDNA, anti-Smith, anti-ribonucleoprotein (RNP), anti-Ro, anti-La, rheumatoid factor (RF), C3 and C4. Among those historically negative for immunologic markers, a current assessment of the markers by the reference laboratory generally yielded a low percentage of additional positives (3-13%). However, 6/11 (55%) of those historically negative for ANA were positive by the reference laboratory, and the reference laboratory test also identified 20% more patients with anti-RNP and 18% more with RF. Among those historically positive for immunologic markers, the reference laboratory results were generally positive on the same laboratory test (range 57% to 97%). However, among those with a history of low C3 or C4, the current reference laboratory results indicated low C3 or C4 a low percentage of the time (18% and 39%, respectively). ANA positivity remained positive over time, in contrast to previous studies. Anti-Ro, La, RNP, Smith and anti-dsDNA antibodies had substantial agreement over time, while complement had less agreement. This variation could partially be explained by variability of the historical assays, which were done by local laboratories over varying periods of time. Variation in the results for complement, however, is more likely to be explained by response to treatment. These findings deserve consideration in the context of diagnosis and enrolment in clinical trials.

International consensus for a definition of disease flare in lupus.

The Lupus Foundation of America (LFA) convened an international working group to obtain a consensus definition of disease flare in lupus. With help from the Paediatric Rheumatology International Trials Organization (PRINTO), two web-based Delphi surveys of physicians were conducted. Subsequently, the LFA held a second consensus conference followed by a third Delphi survey to reach a community-wide agreement for flare definition. Sixty-nine of the 120 (57.5%) polled physicians responded to the first survey. Fifty-nine of the responses were available to draft 12 preliminary statements, which were circulated in the second survey. Eighty-seven of 118 (74%) physicians completed the second survey, with an agreement of 70% for 9/12 (75%) statements. During the second conference, three alternative flare definitions were consolidated and sent back to the international community. One hundred and sixteen of 146 (79.5%) responded, with agreement by 71/116 (61%) for the following definition: "A flare is a measurable increase in disease activity in one or more organ systems involving new or worse clinical signs and symptoms and/or laboratory measurements. It must be considered clinically significant by the assessor and usually there would be at least consideration of a change or an increase in treatment." The LFA proposes this definition for lupus flare on the basis of its high face validity.

Frequency of neuro-psychiatric dysfunction in anti-SSA/SSB exposed children with and without neonatal lupus.

Neonatal lupus is a model of passively acquired autoimmunity whereby anti-SSA/Ro-SSB/La antibodies target the fetal heart and neonatal skin in a minority of cases. Since neuro-psychiatric impairment has been reported in humans and mice exposed prenatally to a variety of maternal autoantibodies including anti-Ro/La, this study was initiated to evaluate the potential neurotoxic effects of these specific autoantibodies and the overall frequency of autoimmune diseases, general health, and somatic growth of children with neonatal lupus and their unaffected siblings. In addition to the general health questionnaires maintained on family members enrolled in the Research Registry for Neonatal Lupus (RRNL), specific questionnaires related to neuro-psychiatric development were sent to all mothers whose children (both affected and unaffected) were older than 5 years of age. Controls consisted of healthy friends. Of 121 anti-Ro exposed children meeting the inclusion criteria, information was returned on 104 (33 cardiac manifestations of neonatal lupus, 20 rash, and 51 unaffected siblings) and 22 of the friend controls. The mean age of all of the children was 14.5 years (range 5-39). In total, 42 (40%) of the 104 anti-Ro exposed children were reported to have a neuro-psychiatric disorder, compared with 6 (27%) of the friend controls (p = 0.34). For 8 (24%) of the congenital heart block (CHB) children (6 boys, 2 girls) the mothers reported attention problems. Four, all boys, were on stimulants. Of the rash children, 4 (20%) (2 boys, 2 girls) had attention problems with one boy on Ritalin. Of the unaffected siblings, 9 (18%) (8 boys and 1 girl) had attention problems with 3 boys on stimulants. One (5%) of the control children (a girl) had attention problems, not requiring therapy. There was no statistical difference in attention problems between the groups (p = 0.120). Behavioral problems were present in all groups with no statistical differences noted. The prevalence of depression, anxiety, developmental delays, learning, hearing, and speech problems were not significantly different between groups. In the CHB children, one boy has nephrotic syndrome and one girl has psoriasis. In the rash children, one girl has juvenile rheumatoid arthritis. In the unaffected group there are five children with autoimmune diseases, two with inflammatory bowel diseases (one boy and one girl), one boy has a spondyloarthropathy, one girl has alopecia areata and one young woman has Antiphospholipid syndrome. In the control group one boy has Henoch Schonlein purpura. There were four cases of hypothyroidism, possibly secondary to Hashimoto's thyroiditis, three in boys with CHB and one in a girl with rash. None of the unaffected siblings or controls had hypothyroidism. Parental reporting of neuro-psychiatric abnormalities was high in anti-Ro exposed children regardless of the neonatal lupus manifestation. However, medication use was limited and although the frequency of this reporting was greater than friend controls, it did not reach significance.

Autoimmune associated congenital heart block: integration of clinical and research clues in the management of the maternal / foetal dyad at risk.

One of the strongest associations with autoantibodies directed to components of the SSA/Ro-SSB/La ribonucleoprotein complex is the development of congenital heart block (CHB) in an offspring, an alarming prospect facing 2% of primigravid mothers with these reactivities. This risk is 10-fold higher in women who have had a previously affected child with CHB. Anti-Ro/La antibodies are necessary but insufficient to cause disease. In vitro and in vivo experiments suggest that the pathogenesis involves exaggerated apoptosis, macrophage/myfibroblast crosstalk, TGFbeta expression and extensive fibrosis in the conducting system and in some cases surrounding myocardium. A disturbing observation is the rapidity of disease progression, with advanced heart block and life-threatening cardiomyopathy observed <2 weeks from normal sinus rhythm. Once 3rd degree (complete) block is identified, reversal has never been achieved, despite dexamethasone. Current strategies include the evaluation of an early echocardiographic marker of injury, such as a prolonged PR interval and the use of IVIG as a preventative measure for pregnancies of mothers with previously affected children.

Disease progression in mothers of children enrolled in the Research Registry for Neonatal Lupus.

OBJECTIVE: To evaluate autoimmune disease progression in asymptomatic and pauci-symptomatic mothers of children with neonatal lupus (NL). METHODS: Clinical information on mothers enrolled in the Research Registry for NL (RRNL) was obtained from medical records. Genotyping was performed for -308A/G tumour necrosis factor (TNF)alpha, 869T/C transforming growth factor (TGF)beta and -889C/T interleukin (IL)1alpha. RESULTS: Of the 321 mothers enrolled, 229 had at least 6 months of follow-up. Of the 51 mothers who were asymptomatic at the NL child's birth, 26 progressed: 12 developed pauci-undifferentiated autoimmune syndrome (pauci-UAS), 2 poly-UAS, 7 SS, 4 SLE and 1 SLE/SS. The median time to develop any symptom was 3.15 years. Of the 37 mothers classified as pauci-UAS at the NL child's birth, 16 progressed: 5 developed poly-UAS, 6 Sjögren syndrome (SS), 4 systemic lupus erythematosus (SLE) and 1 SLE/SS. Of the pauci-UAS mothers enrolled within 1 year, the median time to progression was 6.7 years. Four mothers developed lupus nephritis (two asymptomatic, two pauci-UAS). The probability of an asymptomatic mother developing SLE by 10 years was 18.6%, and developing probable/definite SS was 27.9%. NL manifestations did not predict disease progression in an asymptomatic mother. Mothers with anti-Sjögren syndrome A antigen (SSA/)Ro and anti-Sjögren syndrome B antigen (SSB)/La were nearly twice as likely to develop an autoimmune disease as mothers with anti-SSA/Ro only. Only TGFbetaT/T was significantly higher in SLE mothers compared to asymptomatic mothers (p = 0.03). CONCLUSIONS: Continued follow-up of asymptomatic NL mothers is warranted since nearly half progress, albeit few develop SLE. While the anti-SSB/La antibodies may be a risk factor for progression, further work is needed to determine reliable biomarkers in otherwise healthy women with anti-SSA/Ro antibodies identified solely because of an NL child.

Antibodies to amino acid 200-239 (p200) of Ro52 as serological markers for the risk of developing congenital heart block.

Maternal autoantibodies to the p200-epitope of Ro52 have been suggested to correlate with development of congenital heart block. The aim of the present study was to evaluate the clinical relevance and predictive value of p200-antibodies in high-risk pregnancies. Sera from 515 Finnish, Swedish and American women were included in the study. Sera originated from 202 mothers with an infant affected by second- or third-degree atrioventricular block (AVB), 177 mothers with rheumatic disease having infants with normal heart rate and female blood donors (n = 136). A novel serological assay for Ro52 p200-antibodies with intra- and inter-assay variability of 3% and 3.8% respectively was developed. Mothers of children affected by AVB II-III had significantly higher p200-antibody levels than mothers with rheumatic disease having children with normal heart rate (P < 0.001). In the Swedish cohort, a distinction between foetuses with normal conduction, AVB I, AVB II and III was possible. A significant difference in anti-p200 levels between AVB I and AVB II-III groups compared with foetuses with normal conduction (P < 0.05 and P < 0.01) was observed. Using p200-antibodies as a second step analysis in Ro52-positive pregnancies increased the positive predictive value for foetal cardiac involvement (AVB I, II or III) from 0.39 (0.27-0.51) to 0.53 (0.37-0.68). In conclusion, Ro52 p200-antibodies may occur in women with unaffected children, but levels are significantly higher in mothers of children with congenital heart block and are suggested as a relevant marker in evaluating the risk for foetal AV block.

Dying right to live longer: positing apoptosis as a link between maternal autoantibodies and congenital heart block.

The association of isolated congenital heart block (CHB) with maternal autoantibodies to SSA/Ro and SSB/La ribonucleoproteins is approaching the predictable, even in mothers who are completely asymptomatic. Indeed, this model of passively acquired autoimmunity offers an exceptional opportunity to examine the effector arm of immunity and define the pathogenicity of an autoantibody in mediating tissue injury. The study of CHB exemplifies not only translational research, which inherently draws upon clinical observations and explores them in the laboratory, but "integrational" research which attempts to fit critical clinical and basic observations together, even those seemingly at odds. The spectrum of conduction abnormalities includes second and third-degree block, but injury can extend to the myocardium and endocardium, in rare cases without AV nodal dysfunction. The rarity of disease continues to drive the search for factors (fetal and environmental) that might amplify the effects of the maternal autoantibodies. The identification of exaggerated apoptosis, macrophage/myfibroblast crosstalk, TGF beta expression, and extensive fibrosis in the conducting system and in some cases surrounding myocardium in fetuses dying with CHB, provide in vivo support for several parallel lines of in vitro investigation. Specifically, the consideration of exaggerated apoptosis as the initial link between maternal antibody and tissue injury led to the observation that cardiocytes are capable of phagocytosing autologous apoptotic cardiocytes and anti-Ro/La antibodies inhibit this function. Recognizing that this perturbation of physiologic efferocytosis might divert uptake to professional Fc gamma R-bearing phagocytes fits well with experiments demonstrating macrophage secretion of pro-inflammatory and fibrosing cytokines when coincubated with apoptotic cardiocytes bound by Ro/La antibodies. While CHB is rare, its study should set precedent for defining the role of autoantibodies in driving end organ disease.

Clinical manifestations and coronary artery disease risk factors at diagnosis of systemic lupus erythematosus: data from an international inception cohort.

Systemic Lupus International Collaborating Clinics (SLICC) comprises 27 centres from 11 countries. An inception cohort of 918 SLE patients has been assembled according to a standardized protocol between 2000 and 2006. Clinical features, classic coronary artery disease (CAD) risk factors, as well as other potential risk factors were collected. Of the 918 patients 89% were females, and of multi racial origin. Less than half the patients were living in a permanent relationship, 58% had post secondary education and 51% were employed. Eight percent had family history of SLE. At enrolment, with at mean age of diagnosis of 34.5 years, a significant number of patients already had CAD risk factors, such as hypertension (33%) and hypercholesterolemia (36%). Only 15% of the patients were postmenopausal, 16% were current smokers and 3.6% had diabetes at entry to the SLICC-RAS (Registry for Atherosclerosis). A number of patients in this multi-racial, multi-ethnic inception cohort of lupus patients have classic CAD risk factors within a mean of 5.4 months from diagnosis. This cohort will be increased to 1500 patients to be followed yearly for 10 years. This will provide a unique opportunity to evaluate risk factors for accelerated atherosclerosis in SLE.

Different temporal expression of immunodominant Ro60/60 kDa-SSA and La/SSB apotopes.

Opsonization of apoptotic cardiocytes by maternal anti-Ro/SSA and anti-La/SSB antibodies contributes to tissue injury in the neonatal lupus syndrome. The objective of the current study was to quantify the surface membrane expression of Ro/La components during different phases of apoptosis and map the Ro/La apotopes (epitopes expressed on apoptotic cells) bound by cognate antibodies. Multi-parameter flow cytometry was used to define early and late apoptotic populations and their respective binding by monospecific anti-Ro and anti-La IgGs. Anti-Ro60 bound specifically to early apoptotic Jurkat cells and remained accessible on the cell surface throughout early and late apoptosis. In contrast, anti-La bound exclusively to late apoptotic cells in experiments controlled for non-specific membrane leakage of IgG. Ro52 was not accessible for antibody binding on either apoptotic population. The immunodominant NH2-terminal and RNA recognition motif (RRM) epitopes of La were expressed as apotopes on late apoptotic cells, confirming recent in vivo findings. An immunodominant internal epitope of Ro60 that contains the RRM, and is recognized by a majority of sera from mothers of children with congenital heart block (CHB) and patients with primary Sjögren's syndrome, was also accessible as an apotope on early apoptotic cells. The distinct temporal expression of the immunodominant Ro60 and La apotopes indicates that these intracellular autoantigens translocate independently to the cell surface, and supports a model in which maternal antibody populations against both Ro60 and La apotopes act in an additive fashion to increase the risk of tissue damage in CHB.