Combined dilute alkali and milling process enhances the functionality and gut microbiota fermentability of insoluble corn fiber

In this study, we developed a process combining dilute alkali (NaOH or NaHCO3) and physical (disk milling and/or ball milling) treatments to improve the functionality and fermentability of corn fiber. The results showed that combining chemical with physical processes greatly improved the functionality and fermentability of corn fiber. Corn fiber treated with NaOH followed by disk milling (NaOH-DM-CF) had the highest water retention (19.5 g/g), water swelling (38.8 mL/g), and oil holding (15.5 g/g) capacities. Moreover, NaOH-DM-CF produced the largest amount (42.9 mM) of short-chain fatty acid (SCFA) during the 24-hr in vitro fermentation using porcine fecal inoculum. In addition, in vitro fermentation of NaOH-DM-CF led to a targeted microbial shifting to Prevotella (genus level), aligning with a higher fraction of propionic acid. The outstanding functionality and fermentability of NaOH-DM-CF were attributed to its thin and loose structure, decreased ester linkages and acetyl groups, and enriched structural carbohydrate exposure.

TCDD and CH223191 Alter T Cell Balance but Fail to Induce Anti-Inflammatory Response in Adult Lupus Mice

Aryl hydrocarbon receptor (AhR) responds to endogenous and exogenous ligands as a cytosolic receptor, transcription factor, and E3 ubiquitin ligase. Several studies support an anti-inflammatory effect of AhR activation. However, exposure to the AhR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) during early stages of development results in an autoimmune phenotype and exacerbates lupus. The effects of TCDD on lupus in adults with pre-existing autoimmunity have not been described. We present novel evidence that AhR stimulation by TCDD alters T cell responses but fails to impact lupus-like disease using an adult mouse model. Interestingly, AhR antagonist CH223191 also changed T cell balance in our model. We next developed a conceptual framework for identifying cellular and molecular factors that contribute to physiological outcomes in lupus and created models that describe cytokine dynamics that were fed into a system of differential equations to predict the kinetics of T follicular helper (Tfh) and regulatory T (Treg) cell populations. The model predicted that Tfh cells expanded to larger values following TCDD exposure compared with vehicle and CH223191. Following the initial elevation, both Tfh and Treg cell populations continuously decayed over time. A function based on the ratio of predicted Treg/Tfh cells showed that Treg cells exceed Tfh cells in all groups, with TCDD and CH223191 showing lower Treg/Tfh cell ratios than the vehicle and that the ratio is relatively constant over time. We conclude that AhR ligands did not induce an anti-inflammatory response to attenuate autoimmunity in adult lupus mice. This study challenges the dogma that TCDD supports an immunosuppressive phenotype.

CX3CR1 modulates SLE-associated glomerulonephritis and cardiovascular disease in MRL/lpr mice

OBJECTIVE

Patients with systemic lupus erythematosus (SLE) often develop multi-organ damages including heart and kidney complications. We sought to better define the underlying mechanisms with a focus on the chemokine receptor CX3CR1.

METHODS

We generated Cx3cr1-deficient MRL/lpr lupus-prone mice through backcrossing. We then employed heterozygous intercross to generate MRL/lpr littermates that were either sufficient or deficient of CX3CR1. The mice were also treated with either Lactobacillus spp. or a high-fat diet (HFD) followed by assessments of the kidney and heart, respectively.

RESULTS

Cx3cr1-/- MRL/lpr mice exhibited a distinct phenotype of exacerbated glomerulonephritis compared to Cx3cr1+/+ littermates, which was associated with a decrease of spleen tolerogenic marginal zone macrophages and an increase of double-negative T cells. Interestingly, upon correction of the gut microbiota with Lactobacillus administration, the phenotype of exacerbated glomerulonephritis was reversed, suggesting that CX3CR1 controls glomerulonephritis in MRL/lpr mice through a gut microbiota-dependent mechanism. Upon treatment with HFD, Cx3cr1-/- MRL/lpr mice developed significantly more atherosclerotic plaques that were promoted by Ly6C+ monocytes. Activated monocytes expressed ICOS-L that interacted with ICOS-expressing follicular T-helper cells, which in turn facilitated a germinal center reaction to produce more autoantibodies. Through a positive feedback mechanism, the increased circulatory autoantibodies further promoted the activation of Ly6C+ monocytes and their display of ICOS-L.

CONCLUSIONS

We uncovered novel, Cx3cr1 deficiency-mediated pathogenic mechanisms contributing to SLE-associated glomerulonephritis and cardiovascular disease.

Nlrp12 deficiency alters gut microbiota and ameliorates Faslpr-mediated systemic autoimmunity in male mice

NLRP12 has dual roles in shaping inflammation. We hypothesized that NLRP12 would modulate myeloid cells and T cell function to control systemic autoimmunity. Contrary to our hypothesis, the deficiency of Nlrp12 in autoimmune-prone B6.Faslpr/lpr mice ameliorated autoimmunity in males but not females. Nlrp12 deficiency dampened B cell terminal differentiation, germinal center reaction, and survival of autoreactive B cells leading to decreased production of autoantibodies and reduced renal deposition of IgG and complement C3. In parallel, Nlrp12 deficiency reduced the expansion of potentially pathogenic T cells, including double-negative T cells and T follicular helper cells. Furthermore, reduced pro-inflammatory innate immunity was observed, where the gene deletion decreased in-vivo expansion of splenic macrophages and mitigated ex-vivo responses of bone marrow-derived macrophages and dendritic cells to LPS stimulation. Interestingly, Nlrp12 deficiency altered the diversity and composition of fecal microbiota in both male and female B6/lpr mice. Notably, however, Nlrp12 deficiency significantly modulated small intestinal microbiota only in male mice, suggesting that the sex differences in disease phenotype might be gut microbiota-dependent. Together, these results suggest a potential pathogenic role of NLRP12 in promoting systemic autoimmunity in males. Future studies will investigate sex-based mechanisms through which NLRP12 differentially modulates autoimmune outcomes.

Hypovitaminosis A Drives the Progression of Tubulointerstitial Lupus Nephritis through Potentiating Predisease Cellular Autoreactivity

Vitamin A (VA) deficiency (VAD) is observed in both humans and mice with lupus nephritis. However, whether VAD is a driving factor for accelerated progression of lupus nephritis is unclear. In this study, we investigated the effect of VAD on the progression of lupus nephritis in a lupus-prone mouse model, MRL/lpr. We initiated VAD either during gestation or after weaning to reveal a potential time-dependent effect. We found exacerbated lupus nephritis at ∼15 wk of age with both types of VAD that provoked tubulointerstitial nephritis leading to renal failure. This was concomitant with significantly higher mortality in all VAD mice. Importantly, restoration of VA levels after weaning reversed VAD-induced mortality. These results suggest VAD-driven acceleration of tubulointerstitial lupus nephritis. Mechanistically, at the earlier time point of 7 wk of age and before the onset of clinical lupus nephritis, continued VAD (from gestation until postweaning) enhanced plasma cell activation and augmented their autoantibody production, while also increasing the expansion of T lymphocytes that could promote plasma cell autoreactivity. Moreover, continued VAD increased the renal infiltration of plasmacytoid dendritic cells. VAD initiated after weaning, in contrast, showed modest effects on autoantibodies and renal plasmacytoid dendritic cells that were not statistically significant. Remarkably, analysis of gene expression in human kidney revealed that the retinoic acid pathway was decreased in the tubulointerstitial region of lupus nephritis, supporting our findings in MRL/lpr mice. Future studies will elucidate the underlying mechanisms of how VAD modulates cellular functions to exacerbate tubulointerstitial lupus nephritis.

Lactobacillus spp. act in synergy to attenuate splenomegaly and lymphadenopathy in lupus-prone MRL/lpr mice

Commensal bacteria and the immune system have a close and strong relationship that maintains a balance to control inflammation. Alterations of the microbiota, known as dysbiosis, can direct reactivity to self-antigens not only in the intestinal mucosa but also at the systemic level. Our laboratory previously reported gut dysbiosis, particularly lower abundance of bacteria in the family Lactobacillaceae, in lupus-prone MRL/lpr mice, a model of systemic autoimmunity. Restoring the microbiota with a mix of 5 different Lactobacillus species (spp.), L. reuteri, L. oris, L. johnsonii, L. gasseri and L. rhamnosus, attenuated lupus-liked clinical signs, including splenomegaly and lymphadenopathy. However, our understanding of the mechanism was limited. In this study, we first investigated the effects of individual species. Surprisingly, none of the species individually recapitulated the benefits of the mix. Instead, Lactobacillus spp. acted synergistically to attenuate splenomegaly and renal lymphadenopathy through secreted factors and a CX3CR1-dependent mechanism. Interestingly, oral administration of MRS broth exerted the same benefits likely through increasing the relative abundance of endogenous Lactobacillus spp. Mechanistically, we found increased percentages of FOXP3-negative type 1 regulatory T cells with administration of the mix in both spleen and mesenteric lymph nodes. In addition, oral gavage of Lactobacillus spp. decreased the percentage of central memory T cells while increasing that of effector memory T cells in the lymphoid organs. Furthermore, a decreased percentage of double negative T cells was observed in the spleen with the mix. These results suggest that Lactobacillus spp. might act on T cells to attenuate splenomegaly and lymphadenopathy. Together, this study advances our understanding of how Lactobacillus spp. attenuate lupus in MRL/lpr mice. The synergistic action of these bacteria suggests that multiple probiotic bacteria in combination may dampen systemic autoimmunity and benefit lupus patients.

Analyses of Proteinuria, Renal Infiltration of Leukocytes, and Renal Deposition of Proteins in Lupus-prone MRL/lpr Mice

Systemic lupus erythematosus (SLE) is an autoimmune disorder with no known cure and is characterized by persistent inflammation in many organs, including the kidneys. Under such circumstances, the kidney loses its ability to clean waste from the blood and regulate salt and fluid concentrations, eventually leading to renal failure. Women, particularly those of childbearing age, are diagnosed nine times more often than men. Kidney disease is the leading cause of mortality in SLE patients. The present protocol describes a quick and simple method to measure excreted protein levels in collected urine, tracking lupus progression over time. In addition, an approach to isolate kidney mononuclear cells is provided based on size and density selection to investigate renal infiltration of leukocytes. Furthermore, an immunohistochemical method has been developed to characterize protein deposition in the glomeruli and leukocyte infiltration in the tubulointerstitial space. Together, these methods can help investigate the progression of chronic inflammation associated with the kidneys of lupus-prone MRL/lpr mice.

Phenotypic Drift in Lupus-Prone MRL/lpr Mice: Potential Roles of MicroRNAs and Gut Microbiota

MRL/lpr mice have been extensively used as a murine model of lupus. Disease progression in MRL/lpr mice can differ among animal facilities, suggesting a role for environmental factors. We noted a phenotypic drift of our in-house colony, which was the progeny of mice obtained from The Jackson Laboratory (JAX; stocking number 000485), that involved attenuated glomerulonephritis, increased splenomegaly, and reduced lymphadenopathy. To validate our in-house mice as a model of lupus, we compared these mice with those newly obtained from JAX, which were confirmed to be genetically identical to our in-house mice. Surprisingly, the new JAX mice exhibited a similar phenotypic drift, most notably the attenuation of glomerulonephritis. Interestingly, our in-house colony differed from JAX mice in body weight and kidney size (both sexes), as well as in splenic size, germinal center formation, and level of anti-dsDNA auto-IgG in the circulation (male only). In addition, we noted differential expression of microRNA (miR)-21 and miR-183 that might explain the splenic differences in males. Furthermore, the composition of gut microbiota was different between in-house and new JAX mice at early time points, which might explain some of the renal differences (e.g., kidney size). However, we could not identify the reason for attenuated glomerulonephritis, a shared phenotypic drift between the two colonies. It is likely that this was due to certain changes of environmental factors present in both JAX and our facilities. Taken together, these results suggest a significant phenotypic drift in MRL/lpr mice in both colonies that may require strain recovery from cryopreservation.

Vitamin A Deficiency Deteriorates Lupus Nephritis

Vitamin A deficiency (VAD) is observed in both human and mice with lupus nephritis (LN). However, whether VAD is a driving factor for LN progression is unclear. Here, we investigated the effect of VAD on the progression of LN in a lupus-prone mouse model, MRL/lpr. In these mice, while LN is not apparent before 8 weeks of age, the inflammation of lymphoid tissues suggesting initiation of lupus is evident at weaning. Thus, we initiated VAD either before or after weaning to reveal a potential time-dependent effect. At around 15 weeks of age with both types of VAD, we found exacerbated LN that was characterized by deteriorated kidney inflammation, impaired renal epithelial integrity, and dramatic squamous metaplasia of the renal pelvic urothelium. Both types of VAD provoked severe neutrophilic tubulointerstitial nephritis and accelerated renal failure. This was concomitant with significantly higher mortality in all VAD mice. Looking at an earlier time point of 7 weeks of age and before the onset of clinical LN, both types of VAD increased splenomegaly, lymphadenopathy, and circulating autoantibodies; three additional hallmarks of lupus, as well as renal infiltration of conventional and plasmacytoid dendritic cells. These results suggest VAD-driven deterioration of LN regardless of the time of VAD initiation. Our findings raise significant public health concerns that concurrent lupus and VAD may lead to more severe SLE. Future studies will elucidate the underlying mechanisms of how VAD modulates myeloid cells to accelerate the initiation of LN.

Quaternary Ammonium Compound Disinfectants Reduce Lupus-Associated Splenomegaly by Targeting Neutrophil Migration and T-Cell Fate

Hypersensitivity reactions and immune dysregulation have been reported with the use of quaternary ammonium compound disinfectants (QACs). We hypothesized that QAC exposure would exacerbate autoimmunity associated with systemic lupus erythematosus (lupus). Surprisingly, however, we found that compared to QAC-free mice, ambient exposure of lupus-prone mice to QACs led to smaller spleens with no change in circulating autoantibodies or the severity of glomerulonephritis. This suggests that QACs may have immunosuppressive effects on lupus. Using a microfluidic device, we showed that ambient exposure to QACs reduced directional migration of bone marrow-derived neutrophils toward an inflammatory chemoattractant ex vivo. Consistent with this, we found decreased infiltration of neutrophils into the spleen. While bone marrow-derived neutrophils appeared to exhibit a pro-inflammatory profile, upregulated expression of PD-L1 was observed on neutrophils that infiltrated the spleen, which in turn interacted with PD-1 on T cells and modulated their fate. Specifically, QAC exposure hindered activation of splenic T cells and increased apoptosis of effector T-cell populations. Collectively, these results suggest that ambient QAC exposure decreases lupus-associated splenomegaly likely through neutrophil-mediated toning of T-cell activation and/or apoptosis. However, our findings also indicate that even ambient exposure could alter immune cell phenotypes, functions, and their fate. Further investigations on how QACs affect immunity under steady-state conditions are warranted.

Quaternary Ammonium Compound Disinfectants Reduce Lupus-Associated Splenomegaly by Targeting Neutrophil Migration and T-Cell Fate

Hypersensitivity reactions and immune dysregulation have been reported with the use of quaternary ammonium compound disinfectants (QACs). We hypothesized that QAC exposure would exacerbate autoimmunity associated with systemic lupus erythematosus (lupus). Surprisingly, however, we found that compared to QAC-free mice, ambient exposure of lupus-prone mice to QACs led to smaller spleens with no change in circulating autoantibodies or the severity of glomerulonephritis. This suggests that QACs may have immunosuppressive effects on lupus. Using a microfluidic device, we showed that ambient exposure to QACs reduced directional migration of bone marrow-derived neutrophils toward an inflammatory chemoattractant ex vivo. Consistent with this, we found decreased infiltration of neutrophils into the spleen. While bone marrow-derived neutrophils appeared to exhibit a pro-inflammatory profile, upregulated expression of PD-L1 was observed on neutrophils that infiltrated the spleen, which in turn interacted with PD-1 on T cells and modulated their fate. Specifically, QAC exposure hindered activation of splenic T cells and increased apoptosis of effector T-cell populations. Collectively, these results suggest that ambient QAC exposure decreases lupus-associated splenomegaly likely through neutrophil-mediated toning of T-cell activation and/or apoptosis. However, our findings also indicate that even ambient exposure could alter immune cell phenotypes, functions, and their fate. Further investigations on how QACs affect immunity under steady-state conditions are warranted.

Retinoic acid exerts disease stage-dependent and tissue-specific effects on pristane-induced lupus

We previously showed that all-trans-retinoic acid (tRA) exacerbated pre-existing autoimmunity in lupus; however, its effects before disease onset are unknown. Here, using a pristane-induced model, we show that tRA exerts tissue-specific effects when given at the initiation vs. continuation phase of lupus. Pre-pristane treatment with tRA aggravated glomerulonephritis through increasing renal expression of pro-fibrotic protein laminin β1, activating bone marrow CD11b- conventional dendritic cells, increasing the splenic CD4:CD8 ratio, and upregulating the interaction of ICAM-1 and LFA-1 that led to the infiltration of inflammatory cells to the spleen. Transcriptomic analysis revealed that prior to lupus induction, tRA significantly upregulated genes associated with cell differentiation, activation, and migration. Moreover, compared to pristane alone, tRA pre-treatment potentiated, whereas tRA post-treatment significantly suppressed, the renal expression of proinflammatory TNF-α, IL-1β, CCL2, and CCL3. While it may benefit the kidney, post-pristane treatment with tRA worsened the onset and severity of pristane-induced arthritis through promoting neutrophil and mononuclear cell infiltration into the joints. Together, these findings suggest that tRA supplementation regardless of the time of administration promotes chemokine-driven migration and tissue-specific infiltration of inflammatory cells, thereby exacerbating lupus-associated kidney or joint inflammation. Interestingly, both pre- and post-treatments with tRA modulated the gut microbiota in a similar fashion, suggesting a gut microbiota-independent mechanism by which tRA affects the initiation vs. continuation phase of lupus.

TLR9 stimulation by the gut microbiota promotes tissue-specific immunosuppression in autoimmune-prone MRL/lpr mice

To investigate the ability of gut microbiota to modify immune regulation in autoimmune disease, we treated lupus-prone mice with oral vancomycin prior to disease development, and subsequently administered bacterial DNA isolated from commensal bacteria. Vancomycin given prior to disease initiation promotes exacerbation of autoimmune disease, likely due to a decrease in the frequency of B regulatory (Breg) cells, whereas vancomycin given after autoimmune disease onset has suppressive effects on disease phenotype in MRL/lpr mice. Bacterial DNA administration during the pre-disease stage promoted Breg cell production and suppressed autoimmune disease parameters in MRL/lpr mice. Further, we showed that activation of toll-like receptor 9 (TLR9) on B cells was involved in the suppressive effects of bacterial DNA seen in the MRL/lpr mouse model. We found that during the pre-disease period, joint treatment with vancomycin and oral administration of a TLR9 specific agonist, ODN 1826, promoted Breg cells in the lamina propria, increased total CD8+ T cells and effector memory CD44 expressingCD8+ T cells in the spleen, and suppressed Th17 and IFNγ producing CD4+ T cells in the mesenteric lymph nodes. Oral ODN 1826 administration also increased the Treg/Th17 ratio in the mesenteric lymph nodes. The alterations in suppressive vs. proinflammatory cell phenotypes by oral exposure to ODN 1826 suggests that the suppressive effects of bacterial DNA from the gut microbiota are modulated through TLR9 activation in a tissue-specific manner.

The Effect of Dietary Fiber Intake on Systemic Lupus Erythematosus (SLE) Disease in NZB/W Lupus Mice

Dysbiosis in the gut microbiota has been observed in a various autoimmune disease, including SLE, which could cause a leaky gut, triggering an immune response, and thus worsening autoimmune disease expression. In our current studies, we hypothesized that increasing dietary fiber would create a healthy microbiota environment in the gut, leading to decreased leakiness of the gut and to decreased disease expression in and NZB/NZW female mice. NZB/NZW mice were placed on standardized high fiber (HF 30%) or low fiber (LF 0.4%) for 12 weeks beginning at 10 weeks of age. Mice were assessed as they aged for various parameters of disease including proteinuria and anti-dsDNA antibody production. Alteration of the microbiota and short chain fatty acid levels were also assessed. At 36 weeks-of-age, the mice were euthanized and we assessed occlusion protein expression, splenocyte profiles, and kidney tissue. We found as the mice aged, their body weights, anti-dsDNA antibody levels, and proteinuria were not significantly different between the groups. Similarly, there were no differences in SCFA levels. In regard to the microbiota, Chlostridiales bacteria were consistently increased in the HF treated mice compared to the LF treated mice. In regard to disease progression, spleen weight, immune cell profiles, proteinuria, dsDNA levels, and kidney pathology, there was no difference between the HF and LF treated groups. Taken together, these results indicate that in the NZB/W female mouse, a HF diet may alter the microbiota but does not influence disease progression.

Retinoic Acid Exerts Disease Stage-Dependent Effects on Pristane-Induced Lupus

We previously showed that all-trans-retinoic acid (tRA), an active metabolite of vitamin A, exacerbated pre-existing autoimmunity in lupus; however, its effects before the development of autoimmunity are unknown. Here, using a pristane-induced model, we show that tRA exerts differential effects when given at the initiation vs. continuation phase of lupus. Unlike tRA treatment during active disease, pre-pristane treatment with tRA aggravated glomerulonephritis through increasing renal expression of pro-fibrotic protein laminin β1, activating bone marrow conventional dendritic cells (cDCs), and upregulating the interaction of ICAM-1 and LFA-1 in the spleen, indicating an active process of leukocyte activation and trafficking. Transcriptomic analysis revealed that prior to lupus induction, tRA significantly upregulated the expression of genes associated with cDC activation and migration. Post-pristane tRA treatment, on the other hand, did not significantly alter the severity of glomerulonephritis; rather, it exerted immunosuppressive functions of decreasing circulatory and renal deposition of autoantibodies as well as suppressing the renal expression of proinflammatory cytokines and chemokines. Together, these findings suggest that tRA differentially modulate lupus-associated kidney inflammation depending on the time of administration. Interestingly, both pre- and post-pristane treatments with tRA reversed pristane-induced leaky gut and modulated the gut microbiota in a similar fashion, suggesting a gut microbiota-independent mechanism by which tRA affects the initiation vs. continuation phase of lupus.

Pregnancy and lactation interfere with the response of autoimmunity to modulation of gut microbiota

BACKGROUND

Dysbiosis of gut microbiota exists in the pathogenesis of many autoimmune diseases, including systemic lupus erythematosus (lupus). Lupus patients who experienced pregnancy usually had more severe disease flares post-delivery. However, the possible role of gut microbiota in the link between pregnancy and exacerbation of lupus remains to be explored.

RESULTS

In the classical lupus mouse model MRL/lpr, we compared the structures of gut microbiota in pregnant and lactating individuals vs. age-matched naïve mice. Consistent with studies on non-lupus mice, both pregnancy and lactation significantly changed the composition and diversity of gut microbiota. Strikingly, modulation of gut microbiota using the same strategy resulted in different disease outcomes in postpartum (abbreviated as "PP," meaning that the mice had undergone pregnancy and lactation) vs. control (naïve; i.e., without pregnancy or lactation) MRL/lpr females; while vancomycin treatment attenuated lupus in naïve mice, it did not do so, or even exacerbated lupus, in PP mice. Lactobacillus animalis flourished in the gut upon vancomycin treatment, and direct administration of L. animalis via oral gavage recapitulated the differential effects of vancomycin in PP vs. control mice. An enzyme called indoleamine 2,3-dioxygenase was significantly inhibited by L. animalis; however, this inhibition was only apparent in PP mice, which explained, at least partially, the lack of beneficial response to vancomycin in these mice. The differential production of immunosuppressive IL-10 and proinflammatory IFNγ in PP vs. control mice further explained why the disease phenotypes varied between the two types of mice bearing the same gut microbiota remodeling strategy.

CONCLUSIONS

These results suggest that pregnancy and lactation interfere with the response of autoimmunity to modulation of gut microbiota. Further studies are necessary to better understand the complex relationship between pregnancy and lupus.

Induction of Regulatory B Cells by Bacterial DNA in the Gut Microbiota at Early Age is Beneficial in Lupus-prone Mice

SLE is a complex autoimmune disorder with no known cure. We previously reported that oral vancomycin treatment of female MRL/lpr mice during active disease (9 to 15 weeks of age) could significantly ameliorate disease symptoms. However, when vancomycin treatment was initiated from an earlier age (from 3 to 15 weeks), the beneficial effect was not observed. Strikingly, mice given vancomycin during the pre-disease stage (from 3 to 8 weeks) exhibited exacerbated lupus disease. As vancomycin works by removing parts of the gut microbiota, we hypothesized that the regulatory immunity induced by gut microbiota at early age is essential in hammering lupus disease development in MRL/lpr mice. To test the hypothesis, we analyzed diverse regulatory cell types from the mice receiving vancomycin from 3 to 8 weeks of age. Regulatory B (Breg) cells, in particular, were found to be reduced in both the percentage and absolute number in multiple lymphoid organs. Importantly, adoptive transfer of Breg cells at 6–7 weeks of age to long-term vancomycin-treated mice improved lupus-like symptoms. This clearly indicates that Breg cells, inducible by vancomycin-sensitive gut microbiota, plays an important role in suppressing lupus disease initiation and progression. We next sought to determine Breg inducers in the gut microbiota. The serum level of bacterial DNA was found to be significantly lower in mice treated with vancomycin. More importantly, early administration of bacterial DNA reproduced the beneficial effect seen in the Breg adoptive transfer experiment. Together, these results suggest an important protective mechanism against lupus initiation that involves bacterial DNA in the gut microbiota and the induction of Breg cells.

Pregnancy and lactation interfere with the response of autoimmunity to modulation of gut microbiota

Dysbiosis of gut microbiota exists in the pathogenesis of many autoimmune diseases, including lupus. Currently, women with lupus are recommended to avoid pregnancy, as lupus patients who experienced pregnancy usually had more severe disease flares. However, the possible role of gut microbiota in the link between pregnancy and exacerbation of lupus remains to be explored. In the present study, in the classical lupus mouse model MRL/lpr, we compared the structures of gut microbiota in pregnant and lactating individuals vs. age-matched naïve mice. Consistent with studies on non-lupus mice, both pregnancy and lactation significantly changed the composition and diversity of gut microbiota. Strikingly, modulation of gut microbiota using the same strategy resulted in different disease outcomes in experienced (which had undergone pregnancy and lactation) vs. control (naïve) MRL/lpr females: while vancomycin treatment attenuated lupus in naïve mice, it even exacerbated lupus in experienced mice. L. animalis flourished in the gut upon vancomycin treatment, and direct administration of the bacteria recapitulated the differential effects of vancomycin in experienced vs. control mice. A pregnancy-related enzyme, DHNA, was significantly inhibited by L. animalis; however, this inhibition was only apparent in experienced mice, which explained, at least partially, the lack of beneficial response to vancomycin in these mice. The differential production of IL-10 and IFNγ in experienced vs. control mice further explained why the disease phenotypes varied between the two types of mice bearing the same treatment. These results suggest that pregnancy and lactation interfere with the response of autoimmunity to modulation of gut microbiota.