Lupus and recurrent pregnancy loss: the role of female sex hormones and B cells

Systemic lupus erythematosus is a debilitating autoimmune disease characterized by uncontrolled activation of adaptive immunity, particularly B cells, which predominantly affects women in a 9 to 1 ratio compared to men. This stark sex disparity strongly suggests a role for female sex hormones in the disease's onset and progression. Indeed, it is widely recognized that estradiol not only enhances the survival of autoreactive B cells but also stimulates the production of autoantibodies associated with systemic lupus erythematosus, such as anti-nuclear antibodies and anti-dsDNA antibodies. Clinical manifestations of systemic lupus erythematosus typically emerge after puberty and persist throughout reproductive life. Furthermore, symptoms often exacerbate during the premenstrual period and pregnancy, as increased levels of estradiol can contribute to disease flares. Despite being fertile, women with lupus face a heightened risk of pregnancy-related complications, including pregnancy loss and stillbirth, which significantly surpass the rates observed in the healthy population. Therefore, this review aims to summarize and discuss the existing literature on the influence of female sex hormones on B-cell activation in patients with systemic lupus erythematosus, with a particular emphasis on their impact on pregnancy loss.

Probiotic Lactobacillus kefiri prevents endotoxin-induced preterm birth and stillbirth in mice

Preterm birth (PTB), defined as birth occurring before 37 weeks of pregnancy, affects 5-18% of pregnancies and is the leading cause of neonatal morbidity and mortality worldwide. Although PTB is considered a syndrome, infection-induced inflammation accounts for up to 50% of all cases. Despite the effort to reduce the incidence of PTB, it continues to rise worldwide and current approaches for preventing or treating PTB are largely unsatisfactory. Probiotics are live microorganisms which, when administered in adequate amounts, confer a health benefit on the host. It is well known that probiotics can modulate the host immune system exerting a potent anti-inflammatory activity. The main aim of this work was to evaluate the capacity of the probiotic Lactobacillus kefiri (Lk48) to prevent preterm birth in mice. C57BL/6 female mice were treated with Lk48 or vehicle a week before and during pregnancy and were challenged with LPS (10 µg), a dose known to induce PTB on gestational day 16. Percentages of PTB as well as stillbirth were evaluated. We observed that oral administration of Lk48 significantly reduced the occurrence of LPS-induced PTB and stillbirth as well as improved post-natal development. This protective effect was associated with a reduction in leucocyte infiltration and reduced inflammation-induced damage in reproductive tissue. Besides, Lk48 treatment also modulated the diversity of vaginal microbiota. Our results demonstrated that prophylactic consumption of probiotic L. kefiri prevented LPS-induced PTB and still birth in mice and opens new avenues for exploring novel and promising strategies for preventing PTB in humans.

Oral Probiotic Lactobacillus kefiri prevents Lipopolysaccharide-induced preterm birth, reduces inflammation and modulates the vaginal microbiota inpregnant mice

Prevention and treatment of preterm birth (PTB) are an unresolved global challenge in obstetric care. Human PTB is defined as delivery prior to 37 weeks of gestation. It is known that inflammation is a contributing factor where an inflammatory cascade within the gestational tissues followed by a massive influx of leukocytes takes place. The efficacy of actual interventions are largely unsatisfactory. We have shown that treatment with probiotic Lactobacillus Kefiri (Lk) completely prevented PTB (100%) in a lipopolysaccharide (LPS)-induced PTB mice model. Given this, we sought to elucidate the mechanisms behind PB-Lk protective role in PTB induction.

C57BL/6 females were oral treated every 48h during a week with Lk or vehicle before being mated with BALB/c males and during pregnancy. Females were challenged with LPS on gd 16 (~3 days before expected term). Samples from gestational tissues were harvest 18 h after LPS. Leukocytes influx was evaluated by flow cytometry. Metalloproteinase-9 activity was measured by zymography. In addition, histological examination by light microscopy was performed. The impact on vaginal microbiota was evaluated by a qualitative analysis (PCR-DGGE).

Treatment with Lk, significantly lowered leucocytes influx induced by LPS as well as MMP-9 activity. Histological studies confirmed these findings. In placenta, Lk treatment ameliorated changes in micro and macrocirculation and DGGE profiles allowed differentiation of groups in two clusters, suggesting that Lk induced changes in the vaginal community composition. Our results demonstrate that Lk administration may have the potential to serve as a prophylactic therapy for inflammation-associated conditions during pregnancy, including PTB.

ST2-expressing B1 B cells acquire an anti-inflammatory capacity during pregnancy in mice

In the context of pregnancy, it is known that IL-33 induces the production of anti-inflammatory molecules by decidual B1 cells, protecting against preterm birth (PTB) in human and mouse. We have previously showed that expression of IL-33 receptor, Il1rl1 (ST2) is significantly upregulated in splenic B cells during mid pregnancy, predominantly in B1 cell subset. Furthermore, using an LPS induced PTB mouse model, we observed increased numbers of splenic and decidual ST2-expressing B1 cells in the acute phase of PTB as compared to term pregnant females.

We aimed to investigate here the anti-inflammatory properties of ST2-expressing B1 cells during pregnancy. Total splenocytes from pregnant (P) and non-pregnant (NP) mice were isolated and cultured for 24h with/without LPS (10 μgr/ml), ST2 expression and cytokine production by ST2+ B1 cells was evaluated by flow cytometry. B1 cells from P mice stimulated with LPS showed significantly higher levels of ST2 expression. ST2+ B1 cells produced significantly higher levels of IL-10 and significantly lower levels of TNF-α and IL-17 as compared to ST2+ B1 cells from NP mice.

In a separate project in our laboratory we demonstrated that prophylactic treatment with probiotic Lactobacillus kefiri prevented LPS-induced PTB in mice. Interestingly, we observed that numbers of splenic and decidual ST2-expressing B1 cells were increased in L. kefiri treated mice that were protected against LPS-induced PTB.

Our data strongly suggest an anti-inflammatory capacity of ST2-expressing B1 cells during gestation, presumably to ensure pregnancy wellbeing and prevent inflammation induced PTB.

Differential gene expression of the B Cell Receptor (BCR) signaling pathway during pregnancy in mice

The aim of this work was to characterize BCR signaling pathway gene expression in B cells during pregnancy. B-cell receptor (BCR) signaling regulates critical cell-fate decisions in B cells like activation, proliferation, expression of costimulatory molecules and cytokine receptors. Changes on the dynamic of BCR signaling pathway during pregnancy might have an impact on the way how the immune system fight against infections or regulate autoimmunity during this critical period of time.

We performed a genome-wide transcriptome profile (GeneChip™ Mouse Gene 1.0 ST Array, Affymetrix) on pure splenic B cells isolated from pregnant and non-pregnant mice. Results were analyzed and significant gene expression regulation was confirmed by qPCR.

In silico analysis showed that genes associated with B cell receptor signaling pathway were significantly down-regulated in B cells from pregnant mice compared to non-pregnant animals (≈1.5–2 fold changes, Limma eBayes test, p<0.0001, n=4). Further qPCR analysis showed that genes of the BCR pathway involved in B cell activation, proliferation and antibodies production were down-regulated (Unpaired t test, one-tailed, *p<0.05, n=8) in B cell from pregnant mice as compared to non-pregnant females. In contrast, genes of the BCR pathway that inhibits B cells activation presented no significant differences.

We showed here that genes associated with BCR signaling leading to B cell activation and proliferation were significantly down-regulated during pregnancy. These results might help to understand why pregnant women are more susceptible to infections as well as some B cell associated autoimmune diseases experience a significant improvement in the symptoms during pregnancy.