A New Zealand Black-derived locus suppresses chronic graft-versus-host disease and autoantibody production through nonlymphoid bone marrow-derived cells

Contribution of Dendritic Cell Subsets to T Cell-Dependent Responses in Mice

BATF3-deficient mice that lack CD8⁺ dendritic cells (DCs) showed an exacerbation of chronic graft-versus-host disease (cGVHD), including T follicular helper (Tfh) cell and autoantibody responses, whereas mice carrying the Sle2c2 lupus-suppressive locus with a mutation in the G-CSFR showed an expansion of CD8⁺ DCs and a poor mobilization of plasmacytoid DCs (pDCs) and responded poorly to cGVHD induction. Here, we investigated the contribution of CD8⁺ DCs and pDCs to the humoral response to protein immunization, where CD8^neg DCs are thought to represent the major inducers. Both BATF3^-/- and Sle2c2 mice had reduced humoral and germinal center (GC) responses compared with C57BL/6 (B6) controls. We showed that B6-derived CD4⁺ DCs are the major early producers of IL-6, followed by CD4^-CD8^- DCs. Surprisingly, IL-6 production and CD80 expression also increased in CD8⁺ DCs after immunization, and B6-derived CD8⁺ DCs rescued Ag-specific adaptive responses in BATF3^-/- mice. In addition, inflammatory pDCs (ipDCs) produced more IL-6 than all conventional DCs combined. Interestingly, G-CSFR is highly expressed on pDCs. G-CSF expanded pDC and CD8⁺ DC numbers and IL-6 production by ipDCs and CD4⁺ DCs, and it improved the quality of Ab response, increasing the localization of Ag-specific T cells to the GC. Finally, G-CSF activated STAT3 in early G-CSFR⁺ common lymphoid progenitors of cDCs/pDCs but not in mature cells. In conclusion, we showed a multilayered role of DC subsets in priming Tfh cells in protein immunization, and we unveiled the importance of G-CSFR signaling in the development and function pDCs.

A murine Skint6 W168X allele contributes to autoimmune disease in a transgenic model

BACKGROUND

The genetic factor is a great driver of systemic lupus erythematosus. A Skint6 W168X allele was previously identified in the murine lupus susceptibility rec1d1 sublocus. The purpose of this study is to investigate the pathogenic role and mechanism of the Skint6 W168X allele in lupus autoimmune disease.

METHODS

The gene-editing CRISPR/Cas9 system was used to generate transgenic models with the Skint6 W168X allele. PCR and Sanger's sequencing techniques were applied to mRNA quantification and DNA sequence detection. Flow cytometry was adopted for immunophenotyping. Pathological evaluation of kidneys and lungs was performed using several immunopathological approaches.

RESULTS

The transgenic models with the Skint6 W168X allele were created, including B6.Skint6^X/X and B6.lpr.Skint6^X/X strains. The B6.lpr.Skint6^X/X mice showed bigger spleen and lymph nodes, more lymphocytes and effector T cell populations, more severe nephritis with more IgG and C3 deposit in glomeruli as well as worse proteinuria, and more severe lung inflammation than control B6.lpr mice. In addition, a skint6 receptor binding Skint6 peptide was identified from T and B lymphocytes. B6.Skint6^X/X mice have lower percentages of skint6 receptor⁺ T and B cells in spleen than B6 mice.

CONCLUSION

The Skint6 W168X allele in murine lupus rec1d1 sublocus was validated to be a pathogenic mutant gene and contributes to autoimmune disease through producing a truncated Skint6 peptide of binding the skint6 receptors on lymphocytes.

Granulocyte colony-stimulating factor is not pathogenic in lupus nephritis

Systemic lupus erythematosus (lupus) is an autoimmune disease characterized by autoantibodies that form immune complexes with self‐antigens, which deposit in various tissues, leading to inflammation and disease. The etiology of disease is complex and still not completely elucidated. Dysregulated inflammation is an important disease feature, and the mainstay of lupus treatment still utilizes nonspecific anti‐inflammatory drugs. Granulocyte colony‐stimulating factor (G‐CSF) is a growth, survival, and activation factor for neutrophils and a mobilizer of hematopoietic stem cells, both of which underlie inflammatory responses in lupus. To determine whether G‐CSF has a causal role in lupus, we genetically deleted G‐CSF from Lyn‐deficient mice, an experimental model of lupus nephritis. Lyn^−/−G‐CSF^−/− mice displayed many of the inflammatory features of Lyn‐deficient mice; however, they had reduced bone marrow and tissue neutrophils, consistent with G‐CSF's role in neutrophil development. Unexpectedly, in comparison to aged Lyn‐deficient mice, matched Lyn^−/−G‐CSF^−/− mice maintained neutrophil hyperactivation and exhibited exacerbated numbers of effector memory T cells, augmented autoantibody titers, and worsened lupus nephritis. In humans, serum G‐CSF levels were not elevated in patients with lupus or with active renal disease. Thus, these studies suggest that G‐CSF is not pathogenic in lupus, and therefore G‐CSF blockade is an unsuitable therapeutic avenue.

A Variant of the Histone-Binding Protein sNASP Contributes to Mouse Lupus

The Sle2c1rec1c (rec1c) sublocus is derived from the mouse lupus susceptibility 2 (Sle2) locus identified in the NZM2410 model. Our current study dissected the functional characters and the genetic basis of the rec1c locus relative to lupus when co-expressed with the Fas^lpr mutation, an established inducer of autoimmunity. The rec1c.lpr mice exhibited mild expansion of lymph nodes and had a normal T cell cellularity, but developed significantly kidney and lung inflammation, indicating that the rec1c amplifies lpr-induced autoimmune pathogenesis. A variant of somatic nuclear autoantigenic sperm protein (sNASP) was identified from the rec1c interval as a substitution of two consecutive amino acid residues in the histone-binding domain, resulting in an increased binding affinity to histone H4 and H3.1/H4 tetramer. To determine the role of the sNASP rec1c allele in mouse lupus, a novel strain was generated by introducing the rec1c mutations into the B6 genome. In this transgenic model, the sNASP allele synergized with the lpr mutation leading to moderate autoimmune phenotypes and aggravating inflammatory pathology alterations in kidney and lung that were similar to those observed in the rec1c.lpr mice. These results establish that the sNASP allele is a pathogenic genetic element in the rec1c sublocus, which not only promotes autoimmunity, but also exacerbates the inflammation reaction of end organs in mouse lupus pathogenesis. It also shows the complexity of the Sle2c locus, initially mapped as the major locus associated with B1a cell expansion. In addition to Cdkn2c, which regulates this expansion, we have now identified in the same locus a protective allele of Csf3r, a variant of Skint6 associated with T cell activation, and now a variant of sNASP that amplifies autoimmunity and tissue damage.

Protective Role of Myeloid Cells Expressing a G-CSF Receptor Polymorphism in an Induced Model of Lupus

The genetic analysis of the lupus-prone NZM2410 mouse has identified a suppressor locus, Sle2c2, which confers resistance to spontaneous lupus in combination with NZM2410 susceptibility loci, or in the chronic graft-versus-host disease (cGVHD) induced model of lupus in the B6.Sle2c2 congenic strain. The candidate gene for Sle2c2, the Csf3r gene encoding the granulocyte colony-stimulating factor receptor (G-CSF-R/CD114), was validated when cGVHD was restored in B6.Sle2c2 mice after treatment with G-CSF. The goal of the project reported herein was to investigate the myeloid cells that confer resistance to cGVHD and to ascertain if the mechanism behind their suppression involves the G-CSF pathway. We showed that despite expressing the highest levels of G-CSF-R, neutrophils play only a modest role in the autoimmune activation induced by cGVHD. We also found reduced expression levels of G-CSF-R on the surface of dendritic cells (DCs) and a differential distribution of DC subsets in response to cGVHD in B6.Sle2c2 versus B6 mice. The CD8α⁺ DC subset, known for its tolerogenic phenotype, was expanded upon induction of cGVHD in B6.Sle2c2 mice. In addition, the deficiency of CD8α⁺ DC subset enhanced the severity of cGVHD in B6.Batf3^-/- and B6.Sle2c2 mice, confirming their role in suppression of cGVHD. B6.Sle2c2DCs presented lowered activation and antigen presentation abilities and expressed lower levels of genes associated with DC activation and maturation. Exposure to exogenous G-CSF reversed the majority of these phenotypes, suggesting that tolerogenic DCs maintained through a defective G-CSF-R pathway mediated the resistance to cGVHD in B6.Sle2c2 mice.

An update on lupus animal models

PURPOSE OF REVIEW

The complexity and heterogeneity of the clinical presentation in systemic lupus of erythematosus (SLE), combined to the inherent limitations of clinical research, have made it difficult to investigate the cause of this disease directly in patients. Various mouse models have been developed to dissect the cellular and genetic mechanisms of SLE, as well as to identify therapeutic targets and to screen treatments. The purpose of this review is to summarize the major spontaneous and induced mouse models of SLE and to provide an update on the major advances they have contributed to the field.

RECENT FINDINGS

Mouse models of SLE have continued to contribute to understand the cellular, signaling and metabolic mechanisms contributing to the disease and how targeting these pathways can provide therapeutic targets. Whenever possible, we discuss the advantage of using one model over the others to test a specific hypothesis.

SUMMARY

Spontaneous and induced models of lupus models are useful tools for the study of the cause of the disease, identify therapeutic targets and screen treatments in preclinical studies. Each model shares specific subsets of attributes with the disease observed in humans, which provides investigators a tool to tailor to their specific needs.

T-bet+CD11c+ B cells are critical for antichromatin immunoglobulin G production in the development of lupus

Background

A hallmark of systemic lupus erythematosus is high titers of circulating autoantibodies. Recently, a novel CD11c⁺ B-cell subset has been identified that is critical for the development of autoimmunity. However, the role of CD11c⁺ B cells in the development of lupus is unclear. Chronic graft-versus-host disease (cGVHD) is a lupus-like syndrome with high autoantibody production. The purpose of this study was to explore the role of CD11c⁺ B cells in the pathogenesis of lupus in cGVHD mice.

Methods

cGVHD was induced by an intraperitoneal injection of 5 × 10⁷ Bm12 splenocytes into B6 mice. Flow cytometry was used to analyze mice splenocytes and human samples. Magnetic beads were used to isolate mice B cells. Gene expression was determined by real-time quantitative polymerase chain reaction (RT-qPCR). Enzyme-linked immunosorbent assay (ELISA) was used to detect antibodies in serum and supernatants.

Results

The percentage and absolute number of CD11c⁺ B cells was increased in cGVHD-induced lupus, with elevated levels of antichromatin immunoglobulin (Ig)G and IgG2a in sera. CD11c⁺ plasma cells from cGVHD mice produced large amounts of antichromatin IgG2a upon stimulation. Depletion of CD11c⁺ B cells reduced antichromatin IgG and IgG2a production. T-bet was upregulated in CD11c⁺ B cells. Knockout of T-bet in B cells alleviated cGVHD-induced lupus. Importantly, the percentage of T-bet⁺CD11c⁺ B cells increased in lupus patients and positively correlated with serum antichromatin levels.

Conclusion

T-bet⁺CD11c⁺ B cells promoted high antichromatin IgG production in the lupus-like disease model cGVHD. In lupus patients, the percentage of T-bet⁺CD11c⁺ B cells was elevated and positively correlated with antichromatin antibodies. The findings provide potential therapeutic insight into lupus disease treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1438-2) contains supplementary material, which is available to authorized users.

IL-10 Production Is Critical for Sustaining the Expansion of CD5+ B and NKT Cells and Restraining Autoantibody Production in Congenic Lupus-Prone Mice

The development and progression of systemic lupus erythematosus is mediated by the complex interaction of genetic and environmental factors. To decipher the genetics that contribute to pathogenesis and the production of pathogenic autoantibodies, our lab has focused on the generation of congenic lupus-prone mice derived from the New Zealand Black (NZB) strain. Previous work has shown that an NZB-derived chromosome 4 interval spanning 32 to 151 Mb led to expansion of CD5⁺ B and Natural Killer T (NKT) cells, and could suppress autoimmunity when crossed with a lupus-prone mouse strain. Subsequently, it was shown that CD5⁺ B cells but not NKT cells derived from these mice could suppress the development of pro-inflammatory T cells. In this paper, we aimed to further resolve the genetics that leads to expansion of these two innate-like populations through the creation of additional sub-congenic mice and to characterize the role of IL-10 in the suppression of autoimmunity through the generation of IL-10 knockout mice. We show that expansion of CD5⁺ B cells and NKT cells localizes to a chromosome 4 interval spanning 91 to 123 Mb, which is distinct from the region that mediates the majority of the suppressive phenotype. We also demonstrate that IL-10 is critical to restraining autoantibody production and surprisingly plays a vital role in supporting the expansion of innate-like populations.

Dysregulated cytokine production by dendritic cells modulates B cell responses in the NZM2410 mouse model of lupus

The breakdown in tolerance of autoreactive B cells in the lupus-prone NZM2410-derived B6.Sle1.Sle2.Sle3 (TC) mice results in the secretion of autoantibodies. TC dendritic cells (DCs) enhance B cell proliferation and antibody secretion in a cytokine-dependent manner. However, the specific cytokine milieu by which TC DCs activate B cells was not known. In this study, we compared TC and C57BL/6 (B6) control for the distribution of DC subsets and for their production of cytokines affecting B cell responses. We show that TC DCs enhanced B cell proliferation through the production of IL-6 and IFN-γ, while antibody secretion was only dependent on IL-6. Pre-disease TC mice showed an expanded PDCA1(+) cells prior to disease onset that was localized to the marginal zone and further expanded with age. The presence of PDCA1(+) cells in the marginal zone correlated with a Type I Interferon (IFN) signature in marginal zone B cells, and this response was higher in TC than B6 mice. In vivo administration of anti-chromatin immune complexes upregulated IL-6 and IFN-γ production by splenic DCs from TC but not B6 mice. The production of BAFF and APRIL was decreased upon TC DC stimulation both in vitro and in vivo, indicating that these B cell survival factors do not play a role in B cell modulation by TC DCs. Finally, TC B cells were defective at downregulating IL-6 expression in response to anti-inflammatory apoptotic cell exposure. Overall, these results show that the TC autoimmune genetic background induces the production of B cell-modulating inflammatory cytokines by DCs, which are regulated by the microenvironment as well as the interplay between DC.

Induced murine models of systemic lupus erythematosus

Induced mouse models of systemic lupus erythematosus (SLE) have been developed to complement the spontaneous models. This chapter describes the methods used in the pristane-induced model and the chronic graft-versus-host disease (cGVHD) model, both of which have been extensively used. We will also outline the specific mechanisms of systemic autoimmunity that can be best characterized using each of these models.

The combination of two Sle2 lupus-susceptibility loci and Cdkn2c deficiency leads to T-cell-mediated pathology in B6.Fas(lpr) mice

The NZM2410 Sle2c1 lupus susceptibility locus is responsible for the expansion of the B1a cell compartment, and for the induction of T-cell induced renal and skin pathology on a CD95-deficient (Fas(lpr)) background. We have previously shown that deficiency in the cyclin-dependent kinase inhibitor p18(INK4c) (p18) was responsible for the B1a cell expansion but was not sufficient to account for the pathology in B6.lpr mice. This study was designed to map the additional Sle2c1 loci responsible for autoimmune pathology when co-expressed with CD95 deficiency. The production, fine-mapping and phenotypic characterization of five recombinant intervals indicated that three interacting subloci were responsive for inducting autoimmune pathogenesis in B6.lpr mice. One of these subloci corresponds most likely to p18 deficiency. Another major locus mapping to a 2-Mb region at the telomeric end of Sle2c1 is necessary to both renal and skin pathology. Finally, a third locus centromeric to p18 enhances the severity of lupus nephritis. These results provide new insights into the genetic interactions leading to systemic lupus erythematosus disease presentation, and represent a major step towards the identification of novel susceptibility genes involved in T-cell-mediated organ damage.

The granulocyte colony stimulating factor pathway regulates autoantibody production in a murine induced model of systemic lupus erythematosus

Introduction

An NZB-derived genetic locus (Sle2c2) that suppresses autoantibody production in a mouse model of induced systemic lupus erythematosus contains a polymorphism in the gene encoding the G-CSF receptor. This study was designed to test the hypothesis that the Sle2c2 suppression is associated with an impaired G-CSF receptor function that can be overcome by exogenous G-CSF.

Methods

Leukocytes from B6.Sle2c2 and B6 congenic mice, which carry a different allele of the G-CSF receptor, were compared for their responses to G-CSF. Autoantibody production was induced with the chronic graft-versus-host-disease (cGVHD) model by adoptive transfer of B6.bm12 splenocytes. Different treatment regimens varying the amount and frequency of G-CSF (Neulasta^®) or carrier control were tested on cGVHD outcomes. Autoantibody production, immune cell activation, and reactive oxygen species (ROS) production were compared between the two strains with the various treatments. In addition, the effect of G-CSF treatment was examined on the production autoantibodies in the B6.Sle1.Sle2.Sle3 (B6.TC) spontaneous model of lupus.

Results

B6.Sle2c2 and B6 leukocytes responded differently to G-CSF. G-CSF binding by B6.Sle2c2 leukocytes was reduced as compared to B6, which was associated with a reduced expansion in response to in vivo G-CSF treatment. G-CSF in vivo treatment also failed to mobilize bone-marrow B6.Sle2c2 neutrophils as it did for B6 neutrophils. In contrast, the expression of G-CSF responsive genes indicated a higher G-CSF receptor signaling in B6.Sle2c2 cells. G-CSF treatment restored the ability of B6.Sle2c2 mice to produce autoantibodies in a dose-dependent manner upon cGVHD induction, which correlated with restored CD4⁺ T cells activation, as well as dendritic cell and granulocyte expansion. Steady-state ROS production was higher in B6.Sle2c2 than in B6 mice. cGVHD induction resulted in a larger increase in ROS production in B6 than in B6.Sle2c2 mice, and this difference was eliminated with G-CSF treatment. Finally, a low dose G-CSF treatment accelerated the production of anti-dsDNA IgG in young B6.TC mice.

Conclusion

The different in vivo and in vitro responses of B6.Sle2c2 leukocytes are consistent with the mutation in the G-CSFR having functional consequences. The elimination of Sle2c2 suppression of autoantibody production by exogenous G-CSF indicates that Sle2c2 corresponds to a loss of function of G-CSF receptor. This result was corroborated by the increased anti-dsDNA IgG production in G-CSF-treated B6.TC mice, which also carry the Sle2c2 locus. Overall, these results suggest that the G-CSF pathway regulates the production of autoantibodies in murine models of lupus.

Autoimmunity in 2011

The mechanisms leading to the onset and perpetuation of systemic and tissue-specific autoimmune diseases are complex, and numerous hypotheses have been proposed or confirmed over the past 12 months. It is particularly of note that the number of articles published during 2011 in the major immunology and autoimmunity journals increased by 3 % compared to the previous year. The present article is dedicated to a brief review of the reported data and, albeit not comprehensive of all articles, is aimed at identifying common and future themes. First, clinical researchers were particularly dedicated to defining refractory forms of diseases and to discuss the use and switch of therapeutic monoclonal antibodies in everyday practice. Second, following the plethora of genome-wide association studies reported in most multifactorial diseases, it became clear that genomics cannot fully explain the individual susceptibility and additional environmental or epigenetic factors are necessary. Both these components were widely investigated, both in organ-specific (i.e., type 1 diabetes) and systemic (i.e., systemic lupus erythematosus) diseases. Third, a large number of 2011 works published in the autoimmunity area are dedicated to dissect pathogenetic mechanisms of tolerance breakdown in general or in specific conditions. While our understanding of T regulatory and Th17 cells has significantly increased in 2011, it is of note that most of the proposed lines of evidence identify potential targets for future treatments and should not be overlooked.

Murine lupus susceptibility locus Sle1c2 mediates CD4+ T cell activation and maps to estrogen-related receptor γ

Sle1c is a sublocus of the NZM2410-derived Sle1 major lupus susceptibility locus. We have shown previously that Sle1c contributes to lupus pathogenesis by conferring increased CD4(+) T cell activation and increased susceptibility to chronic graft-versus-host disease (cGVHD), which mapped to the centromeric portion of the locus. In this study, we have refined the centromeric sublocus to a 675-kb interval, termed Sle1c2. Mice from recombinant congenic strains expressing Sle1c2 exhibited increased CD4(+) T cell intrinsic activation and cGVHD susceptibility, similar to mice with the parental Sle1c. In addition, B6.Sle1c2 mice displayed a robust expansion of IFN-γ-expressing T cells. NZB complementation studies showed that Sle1c2 expression exacerbated B cell activation, autoantibody production, and renal pathology, verifying that Sle1c2 contributes to lupus pathogenesis. The Sle1c2 interval contains two genes, only one of which, Esrrg, is expressed in T cells. B6.Sle1c2 CD4(+) T cells expressed less Esrrg than B6 CD4(+) T cells, and Esrrg expression was correlated negatively with CD4(+) T cell activation. Esrrg encodes an orphan nuclear receptor that regulates oxidative metabolism and mitochondrial functions. In accordance with reduced Esrrg expression, B6.Sle1c2 CD4(+) T cells present reduced mitochondrial mass and altered mitochondrial functions as well as altered metabolic pathway utilization when compared with B6 CD4(+) T cells. Taken together, we propose Esrrg as a novel lupus susceptibility gene regulating CD4(+) T cell function through their mitochondrial metabolism.

Cyclin-dependent kinase inhibitor Cdkn2c regulates B cell homeostasis and function in the NZM2410-derived murine lupus susceptibility locus Sle2c1

Sle2c1 is an NZM2410- and NZB-derived lupus susceptibility locus that induces an expansion of the B1a cell compartment. B1a cells have a repertoire enriched for autoreactivity, and an expansion of this B cell subset occurs in several mouse models of lupus. A combination of genetic mapping and candidate gene analysis presents Cdkn2c, a gene encoding for cyclin-dependent kinase inhibitor p18(INK4c) (p18), as the top candidate gene for inducing the Slec2c1-associated expansion of B1a cells. A novel single nucleotide polymorphism in the NZB allele of the Cdkn2c promoter is associated with a significantly reduced Cdkn2c expression in the splenic B cells and peritoneal cavity B1a cells from Sle2c1-carrying mice, which leads to a defective G1 cell cycle arrest in splenic B cells and increased proliferation of peritoneal cavity B1a cells. As the cell cycle is differentially regulated in B1a and B2 cells, these results suggest that Cdkn2c plays a critical role in B1a cell self-renewal and that its impaired expression leads to an accumulation of these cells with high autoreactive potential.