Quantitative abnormalities of peripheral blood distinct T, B, and natural killer cell subsets and clinical findings in obstetric antiphospholipid syndrome

Systematic review and quantitative meta-analysis of age-dependent human T-lymphocyte homeostasis

Objective

To evaluate and quantitatively describe age-dependent homeostasis for a broad range of total T-cells and specific T-lymphocyte subpopulations in healthy human subjects.

Methods

A systematic literature review was performed to identify and collect relevant quantitative information on T-lymphocyte counts in human blood and various organs. Both individual subject and grouped (aggregated) data on T-lymphocyte observations in absolute and relative values were digitized and curated; cell phenotypes, gating strategies for flow cytometry analyses, organs from which observations were obtained, subjects' number and age were also systematically inventoried. Age-dependent homeostasis of each T-lymphocyte subpopulation was evaluated via a weighted average calculation within pre-specified age intervals, using a piece-wise equal-effect meta-analysis methodology.

Results

In total, 124 studies comprising 11722 unique observations from healthy subjects encompassing 20 different T-lymphocyte subpopulations - total CD45+ and CD3+ lymphocytes, as well as specific CD4+ and CD8+ naïve, recent thymic emigrants, activated, effector and various subpopulations of memory T-lymphocytes (total-memory, central-memory, effector-memory, resident-memory) - were systematically collected and included in the final database for a comprehensive analysis. Blood counts of most T-lymphocyte subpopulations demonstrate a decline with age, with a pronounced decrease within the first 10 years of life. Conversely, memory T-lymphocytes display a tendency to increase in older age groups, particularly after ~50 years of age. Notably, an increase in T-lymphocyte numbers is observed in neonates and infants (0 - 1 year of age) towards less differentiated T-lymphocyte subpopulations, while an increase into more differentiated subpopulations emerges later (1 - 5 years of age).

Conclusion

A comprehensive systematic review and meta-analysis of T-lymphocyte age-dependent homeostasis in healthy humans was performed, to evaluate immune T-cell profiles as a function of age and to characterize generalized estimates of T-lymphocyte counts across age groups. Our study introduces a quantitative description of the fundamental parameters characterizing the maintenance and evolution of T-cell subsets with age, based on a comprehensive integration of available organ-specific and systems-level flow cytometry datasets. Overall, it provides the most up-to-date view of physiological T-cell dynamics and its variance and may be used as a consistent reference for gaining further mechanistic understanding of the human immune status in health and disease.

Impact of antiphospholipid syndrome on placenta and uterine NK cell function: insights from a mouse model

Antiphospholipid syndrome (APS) is associated with recurrent pregnancy morbidity, yet the underlying mechanisms remain elusive. We performed multifaceted characterization of the biological and transcriptomic signatures of mouse placenta and uterine natural killer (uNK) cells in APS. Histological analysis of APS placentas unveiled placental abnormalities, including disturbed angiogenesis, occasional necrotic areas, fibrin deposition, and nucleated red blood cell enrichment. Analyses of APS placentas showed a reduced cell proliferation, lower protein content and thinning of endothelial cells. Disturbances in APS trophoblast cells were linked to a cell cycle shift in cytotrophoblast cells, and a reduced number of spiral artery-associated trophoblast giant cells (SpA-TGC). Transcriptomic profiling of placental tissue highlighted disruptions in cell cycle regulation with notable downregulation of genes involved in developmental or signaling processes. Cellular senescence, metabolic and p53-related pathways were also enriched, suggesting potential mechanisms underlying placental dysfunction in APS. Thrombotic events, though occasionally detected, appeared to have no significant impact on the overall pathological changes. The increased number of dysfunctional uNK cells was not associated with enhanced cytotoxic capabilities. Transcriptomic data corroborated these findings, showing prominent suppression of NK cell secretory capacity and cytokine signaling pathways. Our study highlights the multifactorial nature of APS-associated placental pathologies, which involve disrupted angiogenesis, cell cycle regulation, and NK cell functionality.

T cell involvement in antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a systemic autoimmune disorder characterized by arterial and venous thrombosis, and obstetric complications in the presence of antiphospholipid antibodies (aPL), including lupus anticoagulant, anticardiolipin and anti-β2-glycoprotein I antibodies. APS manifests as single, often as recurrent events, and rarely as a catastrophic condition. Most studies of APS pathogenesis to date have focused on the prothrombotic role of aPL, while innate immune responses such as monocyte, complement and neutrophil activation have been also recognized as part of the thrombo-inflammatory cascade in APS. While the presence of autoreactive T cells against β2-glycoprotein I has been long known, less data are available on their pathogenetic role in APS. In this review, we summarize current knowledge on the involvement of T cells in APS pathophysiology, alterations of T cell subsets in peripheral blood, and clinical associations. We also highlight potential therapeutic opportunities by targeting T helper-B cell interactions in these patients.

Innate and Adaptive Immune Systems in Physiological and Pathological Pregnancy

The dynamic immunological changes occurring throughout pregnancy are well-orchestrated and important for the success of the pregnancy. One of the key immune adaptations is the maternal immune tolerance towards the semi-allogeneic fetus. In this review, we provide a comprehensive overview of what is known about the innate and adaptive immunological changes in pregnancy and the role(s) of specific immune cells during physiological and pathological pregnancy. Alongside this, we provided details of remaining questions and challenges, as well as future perspectives for this growing field of research. Understanding the immunological changes that occur can inform potential strategies on treatments for the optimal health of the neonate and pregnant individual both during and after pregnancy.

B-Cells and BAFF in Primary Antiphospholipid Syndrome, Targets for Therapy?

Primary antiphospholipid syndrome (PAPS) is a systemic autoimmune disease characterized by thrombosis, pregnancy morbidity, and the presence of antiphospholipid antibodies (aPL). Anticoagulants form the mainstay of treatment in PAPS. A growing number of studies suggest a previously underappreciated role of the immune system in the pathophysiology of PAPS. Although B-cells are strongly implicated in the pathophysiology of other autoimmune diseases such as systemic lupus erythematosus (SLE), little is known about the role of B-cells in PAPS. Shifts in B-cell subsets including increases in plasmablasts and higher levels of BAFF are present in patients with PAPS. However, while treatment with rituximab and belimumab may ameliorate thrombotic and non-thrombotic manifestations of PAPS, these treatments do not reduce aPL serum levels, suggesting that B-cells contribute to the pathophysiology of APS beyond the production of autoantibodies.

Association of B Cells with Idiopathic Recurrent Pregnancy Loss: A Systematic Review and Meta-Analysis

Recurrent pregnancy loss (RPL) affects 1-2% of women and is defined as having experienced two or more failed pregnancies. In almost 50% of cases, the causes are idiopathic (IRPL), but increasing evidence has suggested an immunological cause. B cells are known to provide crucial support for a successful pregnancy outcome. However, their involvement in the mechanisms underlying IRPL is still unclear. This systematic review and meta-analysis aimed to comprehensively summarise the existing evidence regarding the levels and profiles of B cells in IRPL. An extensive computerized search in PubMed/Medline, Embase, Scopus, and Web of Science databases was performed with no imposed limits. Two reviewers independently screened all retrieved studies, extracted all the data, and assessed the methodological quality. Disagreements were resolved by a third reviewer. From a total of 1125 retrieved studies, 19 studies were included in the systematic review, and 8 studies were quantitatively analysed. We highlight a potential association between women with IRPL and increased levels of endometrial B cells. In addition, the flow cytometry technique seems to be preferred over immunohistochemistry for identifying those differences, while further studies are necessary to clarify the role of B cells as an immunological risk factor for RPL.

Preliminary Study on the Imbalance Between Th17 and Regulatory T Cells in Antiphospholipid Syndrome

Objective

Patients with antiphospholipid syndrome (APS) have immune cell abnormalities that remain poorly understood. This study compared primary APS (PAPS) and secondary APS (SAPS) patients with healthy controls with respect to peripheral blood lymphocytes, CD4+T cell subsets, and cytokine levels. The correlation between antiphospholipid antibody titres and T helper 17 (Th17) and T regulatory (Treg) cell subsets was also analyzed, together with the correlations between cytokine profiles and the clinical characteristics of APS patients.

Methods

The retrospective study population consisted of 67 APS patients (12 with PAPS, 55 with SAPS) and 40 healthy controls. Absolute numbers of peripheral blood lymphocyte subsets and CD4+ T cell subsets were detected by flow cytometry, and serum cytokine levels by flow cytometry bead array.

Results

Patients with SAPS had lower absolute values of T, B and CD4+T cells than the healthy control group, while only natural killer (NK) cell levels were decreased in patients with PAPS. Absolute numbers of T, B, NK, and CD4+T cells were significantly higher in the PAPS than SAPS group. The trends in CD4+T cell subsets were the same in PAPS and SAPS patients as in healthy controls, with increased Th1, decreased Th2, and decreased Treg levels, and thus an increased Th17/Treg ratio. Th2, Th17, and Treg cell counts were higher in the PAPS than SAPS group. Cytokine analysis showed that only IL-10 levels differed between the two APS groups. However, the levels of all of the studied cytokines were higher in APS patients than healthy controls, and correlated with the clinical characteristics of the patients. In the PAPS group, the titres of two autoantibodies correlated positively with the Th17/Treg ratio and negatively with the levels of D-dimer and Treg subsets.

Conclusions

Our study clearly showed that APS patients have immune disturbances, the most prominent of which is an increase in the Th17/Treg ratio, due to a decrease in the number of Treg cells. These abnormalities may be involved in the occurrence and progression of APS. An additional finding was a higher level of peripheral blood lymphocytes in PAPS than SAPS patients, which may be related to the immunosuppressive treatment of SAPS patients.

Possible effects of chemokine-like factor-like MARVEL transmembrane domain-containing family on antiphospholipid syndrome

Antiphospholipid syndrome (APS) is a systemic autoimmune disease defined by thrombotic or obstetrical events and persistent antiphospholipid antibodies (aPLs). Chemokine-like factor-like MARVEL transmembrane domain-containing family (CMTM) is widely expressed in the immune system and may closely related to APS. This review aimed to systematically summarize the possible effects of CMTM on APS. Publications were collected from PubMed and Web of Science databases up to August 2020. CKLF, CKLFSF, CMTM, antiphospholipid syndrome, immune cells, and immune molecules were used as search criteria. Immune cells, including neutrophil, dendritic cells (DCs), T-cells, B-cells, and inflammatory cytokines, play an important role in the development of APS. Chemokine-like factor 1 (CKLF1) has a chemotactic effect on many cells and can affect the expression of inflammatory cytokines and adhesion molecules through the nuclear factor-kB (NF-kB) pathway or mitogen-activated protein kinase (MARK) pathway. CKLF1 can participate in the maturation of DCs, T lymphocyte activation, and the activation of neutrophils through the MAPK pathway. CMTM1 may act on Annexin A2 by regulating Ca²⁺ signaling. CMTM2 and CMTM6 are up-regulated in neutrophils of APS patients. Some CMTM family members influence the activation and accumulation of platelets. CMTM3 and CMTM7 are binding partners of B-cell linker protein (BLNK), thereby linking B cell receptor (BCR) and activating BLNK-mediated signal transduction in B cells. Moreover, CMTM3 and CMTM7 can act on DCs and B-1a cell development, respectively. CMTM may have potential effects on the development of APS by acting on immune cells and immune molecules. Thus, CMTM may act as a novel prognostic factor or immunomodulatory treatment option of APS.

B cells in primary antiphospholipid syndrome: Review and remaining challenges

It is now widely accepted that antiphospholipid antibodies (aPL) have direct pathogenic effects and that B cells, notably through aPL production, play a key role in the development of antiphospholipid syndrome (APS). Recent findings strengthened the implication of B cells with the description of specific B cell phenotype abnormalities and inborn errors of immunity involving B cell signaling in APS patients. In addition, it has been shown in preclinical models that cross-reactivity between APS autoantigens and mimotopes expressed by human gut commensals can lead to B cell tolerance breakdown and are sufficient for APS development. However, B cell targeting therapies are surprisingly not as effective as expected in APS compared to other autoimmune diseases. Elucidation of the B cell tolerance breakdown mechanisms in APS patients may help to develop and guide the use of novel therapeutic agents that target B cells or specific immune pathway.

T Cell Dysregulation in Non-silicotic Silica Exposed Workers: A Step Toward Immune Tolerance Breakdown

Background: Chronic silica exposure can lead to silicosis, complicated or not by autoimmune diseases (AID). The pathophysiology of silica-induced AID remains not fully understood, especially immune mechanisms that may develop in patients without yet established silicosis. We conducted a prospective clinical study to analyze the impact of crystalline silica (CS) on T cell phenotype and regulatory T cells (Tregs) frequency, as well as on auto-antibodies development in non-silicotic workers exposed to CS.

Methods: Workers with moderate to high exposure level to CS and aged between 30 and 60 years-old were considered for inclusion. Peripheral blood mononuclear cells were analyzed by flow cytometry. Auto-antibodies were screened in serum by immunofluorescence. Blood from 42 and 45 healthy subjects (HC) was used as control for T cell phenotype and serum analyses, respectively.

Results: Among the 63 included workers exposed to CS, 55 had full data available and were analyzed. Ten were exposed to CS for <5 years, 18 for 5–10 years and 27 for more than 10 years. The frequency of Tregs (CD4⁺CD25⁺CD127⁻FoxP3⁺) was significantly lower in CS exposed workers as compared to HC. We found an increased expression of the activation marker HLA-DR on T cells (CD3⁺, CD4⁺, and CD8⁺) of CS exposed workers as compared to HC. Tregs to activated T cells ratio was also lower in exposed subjects. In the latter, HLA-DR expression level and Tregs frequency were significantly associated with CS exposure duration. Serum autoantibody detection was significantly higher in CS exposed workers as compared to HC. Especially, among workers exposed more than 10 years, antinuclear antibodies and ANCA were detected in 44 and 22% among them, as compared to 5 and 2.5% in HC, respectively.

Conclusion: This work shows that CS exposure is associated with a decrease of Tregs frequency, an increase of T cell activation status, and a tolerance breakdown against auto-antigens. These results show that alterations of the T cell compartment can be detected early over the course of CS exposure, preceding silicosis development or AID onset.

Clinical factors associated with pregnancy outcome in women with recurrent pregnancy loss

The aim of this prospective cohort study was to evaluate clinical factors associated with pregnancy outcomes in women with recurrent pregnancy loss (RPL). Women with a history of two or more pregnancy losses underwent workups for clinical factors of RPL and their pregnancies were followed-up with informed consent. Two hundred eleven (81.5%) of 259 women with RPL became pregnant. The multivariable analyses demonstrated that age (p < .01, OR 0.9, 95%CI 0.97-0.83), uterine abnormality (p < .05, OR 0.3, 95%CI 0.11-0.8), and protein C (PC) deficiency (p < .01, OR 0.14, 95%CI 0.03-0.6) were independent factors for becoming pregnancy in women with RPL. The number of previous pregnancy loss (p < .01, OR 0.57, 95%CI 0.43-0.75) and natural killer (NK) cell activity ≥33% (p < .01, OR 0.31, 95%CI 0.13-0.73) were independent factors for live birth in the subsequent pregnancy. Advanced age, the presence of uterine abnormality, and PC deficiency were risk factors for reduced pregnancy rate in women with RPL. Increased number of previous pregnancy loss and high NK cell activity were risk factors for miscarriage in the subsequent pregnancy. These results involve important information and are helpful for clinical practitioners.

Lymphocyte Disturbances in Primary Antiphospholipid Syndrome and Application to Venous Thromboembolism Follow-Up

Among patients with venous thromboembolism (VTE), the persistent detection of antiphospholipid (aPL) antibodies (Ab) represents an independent high risk factor for recurrence. However, oral anticoagulation vitamin K antagonist therapy, frequently used in these patients, is problematic in assessing and/or confirming a diagnosis of primary aPL syndrome (pAPS), suggesting use of alternative strategies. For this reason, and by analogy with other autoimmune diseases, a flow cytometer approach testing peripheral T cell subsets (CD3, CD4, and CD8), B cell subsets (B1, transitional, naive, and memory), and NK cells can be proposed. As an example and to validate the concept, pAPS patients selected from the monocentric VTE case-control EDITH's cohort were selected during their follow-up. As suspected and in contrast to non-APS VTE patients, other autoimmune diseases, and controls, pAPS VTE patients displayed specific lymphocyte disturbances. Quantitative and qualitative modifications were related to total CD4⁺ T cell reduction, a lower CD4/CD8 ratio, and disturbance in B cell homeostasis with increased proportions of B1 cells, transitional B cells (CD24⁺⁺CD38⁺⁺), and naive B cells (IgD⁺CD27^-), while memory B cells (IgD⁺CD27⁺ and IgD^-CD27⁺) were reduced. Interestingly, the absolute number of CD4⁺ T cells positively correlated with IgG anti-cardiolipin Ab levels. Altogether, disturbances of T and B cell homeostasis characterized pAPS VTE patients during their follow-up. This suggests a means of profiling that could be used in addition to existing criteria to characterize them.

Peripheral B-Cell Subset Distribution in Primary Antiphospholipid Syndrome

Background: B-cell differentiation and B-cell tolerance checkpoints may be different in antiphospholipid syndrome (APS) from systemic lupus erythematosus (SLE) and can help to understand differences between them. Our aim was to define alterations of B-cell subsets in patients with primary APS (pAPS) and to compare them with SLE patients and healthy controls (HC). Methods: Cross-sectional study including three study groups: 37 patients with pAPS, 11 SLE patients, and 21 age- and gender-matched HC. We determined the frequencies of different B-cell subsets in peripheral blood naïve and memory compartments. In addition, we measured serum B cell-activating factor (BAFF) levels and circulating pro-inflammatory cytokines, such as IL-6, by commercial ELISA and CBA, respectively. Results: Patients with pAPS showed a lower percentage of immature and naïve B cells than patients with SLE (p = 0.013 and p = 0.010, respectively) and a higher percentage of non-switched memory B cells than patients with SLE (p = 0.001). No differences either in the percentage of switched memory cells or plasma cells were found among the different groups. Serum BAFF levels were higher in SLE patients than in healthy controls and pAPS patients (p = 0.001 and p = 0.017, respectively). A significant increase in the serum BAFF levels was also observed in pAPS patients compared to HC (p = 0.047). Circulating IL-6 levels were higher in SLE and pAPS patients than HC (p = 0.036 and p = 0.048, respectively). A positive correlation was found between serum BAFF and IL-6 levels in patients with SLE but not in pAPS (p = 0.011). Conclusions: Our characterization of peripheral blood B-cell phenotypes in pAPS demonstrates different frequencies of circulating B cells at different stages of differentiation. These differences in the naïve B-cell repertoire could explain the higher number and variety of autoantibodies in SLE patients in comparison to pAPS patients, especially in those with obstetric complications.

Immunologic Abnormalities, Treatments, and Recurrent Pregnancy Loss: What Is Real and What Is Not?

Recurrent pregnancy loss, depending on the definition, affects 1% to 3% of women aiming to have a child. Little is known about the direct causes of recurrent pregnancy loss, and the condition is considered to have a multifactorial and complex pathogenesis. The aim of this review was to summarize the evaluation and the management of the condition with specific emphasis on immunologic biomarkers identified as risk factors as well as current immunologic treatment options. The review also highlights and discusses areas in need of further research.

Peripheral blood T- and B-cell immunophenotypic abnormalities in selected women with unexplained recurrent miscarriage

We aimed to investigate if women with recurrent miscarriage disclosed abnormalities in the maturation and activation status of peripheral blood lymphocyte subsets. In a case control study, 24 women with recurrent miscarriage, 37 women with children but no history of miscarriage and 39 women without previous pregnancies were evaluated. Lymphocyte subsets were evaluated using three-colour flow-cytometry. Selected women with recurrent miscarriage had significantly higher absolute counts of central memory CD4+ T-cells, CD8+DR+ T-cells and memory non-switched B-cells than the control groups. Recurrent miscarriage may be associated with abnormalities of the maturation and activation status of peripheral blood T and B lymphocytes.

Delineating the deranged immune system in the antiphospholipid syndrome

The antiphospholipid syndrome (APS) is a systemic autoimmune disease that is characterized serologically by the presence of antiphospholipid antibodies (aPL) and clinically by vascular thrombosis and obstetric complications. The protein β2 glycoprotein I (β2GPI) is identified as the most important autoantigen in this syndrome. Activation of endothelial cells, thrombocytes and placental tissue by anti-β2GPI antibodies relates to the clinical manifestations of APS. This review describes genetic and environmental factors in relation to APS and summarizes the current knowledge on abnormalities in components of both the innate and adaptive immune system in APS. The role of dendritic cells, T-cells, B-cells, monocytes, neutrophils and NK-cells as well as the complement system in APS are discussed. Several gaps in our knowledge on the pathophysiology of APS are identified and a plea is made for future extensive immune cell profiling by a systems medicine approach in order to better unravel the pathogenesis of APS, to gain more insight in the role of the immune system in APS as well as having the potential to reveal biomarkers or novel therapeutic targets.

CD8+DR+ T-Cells and C3 Complement Serum Concentration as Potential Biomarkers in Thrombotic Antiphospholipid Syndrome

Purpose. To assess complement factors and T lymphocyte activation subset abnormalities in patients with thrombotic antiphospholipid syndrome (APS) as potential biomarkers for development of clinical complications. Methods. We assessed C3, C4, factor B concentrations (nephelometry), complement haemolytic functional activity (CH100, radial immune diffusion), and the activation status of CD4+ and CD8+ T-cells (three-colour flow cytometry) in patients with thrombotic APS. Antiphospholipid (aPL) positive patients without APS-related clinical criteria, systemic lupus erythematosus (SLE) patients, and healthy individuals were evaluated as controls. A clinical followup was performed to assess the potential relationship between the immunological parameters and development of APS-related complications. Results. Lower concentrations of C3 and higher levels of CD8+DR+ cells were risk factors for development of APS-related complications during followup, including rethrombosis and neuropsychiatric symptoms. Patients with diagnosed thrombotic APS had significantly lower levels of C3, C4, and CH100 as well as higher percentages of activated CD4+DR+ and of CD8+DR+ T-cells than healthy controls but similar to that observed in autoimmune disease controls. Conclusion. Lower C3 and C4 complement levels and higher percentages of CD8+DR+ T-cells were observed in thrombotic APS patients. The potential role of these abnormalities as biomarkers of clinical outcome warrants further evaluation in a multicenter study.

The Role of PPARs in Placental Immunology: A Systematic Review of the Literature

Pregnancy is a state of immunotolerance, and pregnancy outcome is strongly linked to the correct activation and balancing of the maternal immune system. Besides abortion as possible result of improper early pregnancy development, other pregnancy associated conditions like preeclampsia (PE), intrauterine growth retardation (IUGR), preterm labour, or gestational diabetes mellitus (GDM) are linked to immunologic overactivation and dysregulation. Both the innate and the adaptive immune system, and therefore B and T lymphocytes, natural killer cells (NK), macrophages and dendritic cells (DCs) are all involved in trophoblast invasion, pregnancy maintenance, and development of pregnancy disorders. Peroxisome proliferator activated receptors (PPARs) are nuclear transcription factors with three known isotypes: PPARα, PPARβ/δ, and PPARγ. They are expressed in most human organs and their function extends from regulating metabolism, homeostasis, and carcinogenesis to immune response. In the recent years, PPARs have been identified in most reproductive tissues and in all lines of immune cells. Only in few cases, the role of PPARs in reproductive immunology has been elucidated though the role of PPARs in immune answer and immunotolerance is evident. Within this paper we would like to give an update on today's knowledge about PPARs and immune cells in reproduction and highlight interesting interferences in regard of future therapeutic targets.

To B or not to B cells-mediate a healthy start to life

Maternal immune responses during pregnancy are critical in programming the future health of a newborn. The maternal immune system is required to accommodate fetal immune tolerance as well as to provide a protective defence against infections for the immunocompromised mother and her baby during gestation and lactation. Natural immunity and antibody production by maternal B cells play a significant role in providing such immunoprotection. However, aberrations in the B cell compartment as a consequence of maternal autoimmunity can pose serious risks to both the mother and her baby. Despite their potential implication in shaping pregnancy outcomes, the role of B cells in human pregnancy has been poorly studied. This review focuses on the role of B cells and the implications of B cell depletion therapy in pregnancy. It highlights the evidence of an association between aberrant B cell compartment and obstetric conditions. It also alludes to the potential mechanisms that amplify these B cell aberrances and thereby contribute to exacerbation of some maternal autoimmune conditions and poor neonatal outcomes. Clinical and experimental evidence suggests strongly that maternal autoantibodies contribute directly to the pathologies of obstetric and neonatal conditions that have significant implications for the lifelong health of a newborn. The evidence for clinical benefit and safety of B cell depletion therapies in pregnancy is reviewed, and an argument is mounted for further clinical evaluation of B cell-targeted therapies in high-risk pregnancy, with an emphasis on improving neonatal outcomes and prevention of neonatal conditions such as congenital heart block and fetal/neonatal alloimmune thrombocytopenia.