Genetic susceptibility to systemic lupus erythematosus protects against cerebral malaria in mice.
ABSTRACT: Plasmodium falciparum has exerted tremendous selective pressure on genes that improve survival in severe malarial infections. Systemic lupus erythematosus (SLE) is an autoimmune disease that is six to eight times more prevalent in women of African descent than in women of European descent. Here we provide evidence that a genetic susceptibility to SLE protects against cerebral malaria. Mice that are prone to SLE because of a deficiency in Fc?RIIB or overexpression of Toll-like receptor 7 are protected from death caused by cerebral malaria. Protection appears to be by immune mechanisms that allow SLE-prone mice better to control their overall inflammatory responses to parasite infections. These findings suggest that the high prevalence of SLE in women of African descent living outside of Africa may result from the inheritance of genes that are beneficial in the immune control of cerebral malaria but that, in the absence of malaria, contribute to autoimmune disease.
Project description:Severe malaria, including cerebral malaria (CM) and placental malaria (PM), have been recognized to have many of the features of uncontrolled inflammation. We recently showed that in mice genetic susceptibility to the lethal inflammatory autoimmune disease, systemic lupus erythematosus (SLE), conferred resistance to CM. Protection appeared to be mediated by immune mechanisms that allowed SLE-prone mice, prior to the onset of overt SLE symptoms, to better control their inflammatory response to Plasmodium infection. Here we extend these findings to ask does SLE susceptibility have 1) a cost to reproductive fitness and/or 2) an effect on PM in mice? The rates of conception for WT and SLE susceptible (SLE(s)) mice were similar as were the number and viability of fetuses in pregnant WT and SLE(s) mice indicating that SLE susceptibility does not have a reproductive cost. We found that Plasmodium chabaudi AS (Pc) infection disrupted early stages of pregnancy before the placenta was completely formed resulting in massive decidual necrosis 8 days after conception. Pc-infected pregnant SLE(s) mice had significantly more fetuses (?1.8 fold) but SLE did not significantly affect fetal viability in infected animals. This was despite the fact that Pc-infected pregnant SLE(s) mice had more severe symptoms of malaria as compared to Pc-infected pregnant WT mice. Thus, although SLE susceptibility was not protective in PM in mice it also did not have a negative impact on reproductive fitness.
Project description:BACKGROUND:Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the production of various autoantibodies. This disease causes disabling neuropsychiatric symptoms even in the absence of apparent inflammation in the central nervous system (CNS), but the mechanisms involved remain unknown. Innate immune-mediated inflammation has attracted attention as a pathogenic mechanism in neuropsychiatric diseases. METHODS:We investigated the CNS of lupus-prone mice focusing on innate immunity. Three strains of lupus-prone mice, Fc?RIIB-/-Yaa, an F1 hybrid of NZB and NZW (NZB/NZW) mice, and MRL/Faslpr (MRL/lpr) mice were used to analyze CNS immunopathology. RESULTS:Flow cytometry analysis demonstrated the numbers of brain CD45+ cells were increased compared with controls in lupus-prone mice. Upregulation of MHC class I and PDCA1 was observed in microglia and CD11b+ myeloid cells of lupus-prone mice, indicating they were activated in response to interferons (IFN). Microglial gene expression analysis of Fc?RIIB-/-Yaa mice revealed the upregulation of IFN-responsive genes and inflammation-related genes including Axl, Clec7a, and Itgax, which were previously reported in neurodegenerative conditions and primed conditions. Upregulated chemokine gene expressions including Ccl5 and Cxcl10 were concurrent with increased numbers of T cells and monocytes, especially Ly6Clo monocytes in the CNS. Upregulation of Axl, Clec7a, Itgax, Ccl5, and Cxcl10 was also observed in NZB/NZW mice, indicating common lupus pathology. The primed status of microglia in Fc?RIIB-/-Yaa mice was also demonstrated by morphological changes such as enlarged cell bodies with hypertrophic processes, and hyperreactivity to lipopolysaccharide. Immunohistochemistry of Fc?RIIB-/-Yaa mice indicated reactive responses of astrocytes and vascular endothelium. Behavioral studies of Fc?RIIB-/-Yaa mice revealed depressive-like behavior and heat hyperalgesia in the forced swim test and the tail-flick test, respectively. CONCLUSIONS:Our data indicated that microglia in lupus exhibit a unique primed phenotype characterized by the upregulated expressions of neurodegeneration-related genes and IFN-responsive genes. Interaction with peripheral cells and brain resident cells was presumed to orchestrate neuroinflammation. Targeting innate immune cells, such as microglia and monocytes, may be a promising therapeutic approach for neuropsychiatric SLE.
Project description:IgG immune complexes (ICs) are generated during immune responses to infection and self-antigen and have been implicated in the pathogenesis of autoimmune diseases such as systemic lupus erythematosus (SLE). Their role, and that of the fragment crystallizable (Fc) receptors that bind them, in driving local inflammation is not fully understood. Low affinity-activating Fc? receptors (Fc?Rs) that bind immune complexes are controlled by a single inhibitory receptor, Fc?RIIb (CD32b). We investigated whether Fc?R cross-linking by IC might induce VEGF-A and lymph node lymphangiogenesis. Murine macrophages and dendritic cells (DCs) stimulated with ICs produced VEGF-A, and this was inhibited by coligation of Fc?RIIb. Similarly, IC-induced VEGF-A production by B cells was inhibited by Fc?RIIb. In vivo, IC generation resulted in VEGF-A-dependent intranodal lymphangiogenesis and increased DC number. We sought to determine the relevance of these findings to autoimmunity because elevated serum VEGF-A has been observed in patients with SLE; we found that lymphangiogenesis and VEGF-A were increased in the lymph nodes of mice with collagen-induced arthritis and SLE. In humans, a SLE-associated polymorphism (rs1050501) results in a dysfunctional Fc?RIIB(T232) receptor. Monocyte-derived macrophages from subjects with the Fc?RIIB(T/T232) genotype showed increased Fc?R-mediated VEGF-A production, demonstrating a similar process is likely to occur in humans. Thus, ICs contribute to inflammation through VEGF-A-driven lymph node lymphangiogenesis, which is controlled by Fc?RIIb. These findings have implications for the pathogenesis, and perhaps future treatment, of autoimmune diseases.
Project description:Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease more prevalent in people of African and Asian origin than Caucasian origin. FcgammaRIIb is an inhibitory Fc receptor with a critical role in immune regulation. Mouse data suggest that FcgammaRIIb deficiency increases susceptibility to autoimmune disease but protects against infection. We show that a SNP in human FCGR2B that abrogates receptor function is strongly associated with susceptibility to SLE in both Caucasians and Southeast Asians. The minor allele of this SNP is more common in Southeast Asians and Africans, populations from areas where malaria is endemic, than in Caucasians. We show that homozygosity for the minor allele is associated with substantial protection against severe malaria in an East African population (odds ratio = 0.56; P = 7.1 x 10(-5)). This protective effect against malaria may contribute to the higher frequency of this SNP and hence, SLE in Africans and Southeast Asians.
Project description:Background: Genetic and epigenetic variability contributes to the susceptibility and pathogenesis of autoimmune diseases. T cells play an important role in several autoimmune conditions, including lupus, which is more common and more severe in people of African descent. To investigate inherent epigenetic differences in T cells between ethnicities, we characterized genome-wide DNA methylation patterns in naïve CD4+ T cells in healthy African-Americans and European-Americans, and then confirmed our findings in lupus patients. Results: Impressive ethnicity-specific clustering of DNA methylation profiling in naïve CD4+ T cells was revealed. Hypomethylated loci in healthy African-Americans were significantly enriched in pro-apoptotic and pro-inflammatory genes. We also found hypomethylated genes in African-Americans to be disproportionately related to autoimmune diseases including lupus. We then confirmed that these genes, such as IL32, CD226, CDKN1A, and PTPRN2 were simi‑ larly hypomethylated in lupus patients of African-American compared to European-American descent. Using patch DNA methylation and luciferase reporter constructs, we showed that methylation of the IL32 promoter region reduces gene expression in vitro. Importantly, bisulfite DNA sequencing demonstrated that cis-acting genetic variants within and directly disrupting CpG sites account for some ethnicity-specific variability in DNA methylation. Overall design: A total of 66 healthy female individuals (21 African-Americans and 45 European-Americans) were recruited for our studies. There was no significant difference in age between the African-American (mean age = 39.3 years) and European-American (mean age = 42.5 years) groups (P value = 0.34). All study participants signed an informed consent prior to enrollment into the study. The institutional review boards at the University of Michigan and the Henry Ford Health System approved this study. To validate the relevance of detected ethnicity-specific DNA methylation differences in an autoimmune disease, a group of age-matched 21 African-American and 42 European-American female lupus patients were studied. All patients met the American College of Rheumatology classification criteria for SLE. This series includes only the healthy control samples.
Project description:BACKGROUND:Systemic lupus erythematosus (SLE or lupus) is a chronic autoimmune disease that is associated with increased morbidity, mortality, healthcare costs and decreased quality of life. African Americans in the USA have three to four times greater prevalence of SLE, risk of developing SLE at an earlier age, and SLE-related disease activity, damage, and mortality compared with Caucasians, with the highest rates experienced by African American women. There is strong evidence that patient-level factors are associated with outcomes, which justifies targeting them with intervention. While evidence-based self-management interventions that incorporate both social support and health education have reduced pain, improved function, and delayed disability among patients with SLE, African Americans and women are still disproportionately impacted by SLE. Peer mentoring interventions are effective in other chronic conditions that disproportionately affect minorities, such as diabetes mellitus, HIV, and kidney disease, but there is currently no empirically tested peer mentoring intervention developed for patients with SLE. Preliminary data from our group suggest that peer mentoring improves self-management, reduces disease activity, and improves health-related quality of life (HRQOL) in African American women with SLE. METHODS:This study will test an innovative, manualized peer mentorship program designed to provide modeling and reinforcement by peers (mentors) to other African American women with SLE (mentees) to encourage them to engage in activities that promote disease self-management. Through a randomized, "mentored" or "support group" controlled design, we will assess the efficacy and mechanism(s) of this intervention in self-management, disease activity, and HRQOL. DISCUSSION:This is the first study to test peer mentorship as an alternative strategy to improve outcomes in African American women with SLE. This could result in a model for other programs that aim to improve disease self-management, disease activity, and HRQOL in African American women suffering from chronic illness. The peer mentoring approach is uniquely fitted to African Americans, and this intervention has the potential to lead to health improvements for African American women with SLE that have not been attainable with other interventions. This would significantly reduce disparities and have considerable public health impact. TRIAL REGISTRATION:ClinicalTrials.gov, NCT03734055 . Registered on 27 November 2018.
Project description:Osteoporotic fracture is a major cause of morbidity in patients with systemic lupus erythematosus (SLE). Mice lacking Fc gamma receptor IIb (Fc?RIIB) spontaneously develop lupus-like disease or SLE at 6-month-old. The aim of this study was to investigate whether Fc?RIIB deletion induces osteopenia. ?CT analysis indicated that deleting Fc?RIIB did not affect cancellous bone microarchitecture in 3-month-old mice in which SLE had not yet developed. However, 6- and 10-month-old Fc?RIIB-/- males that developed an SLE-like phenotype were osteopenic and Fc?RIIB deletion resulted in decreased cancellous bone volume. Histomorphometry confirmed a significant decrease in cancellous bone volume in 6- and 10-month-old Fc?RIIB-/- males. The osteoclast number was increased without any change in osteoblast number. In vitro assays indicated that deleting Fc?RIIB increased osteoclast differentiation while alkaline phosphatase activity and mineralization were unaltered. These changes were associated with increases in steady-state mRNA levels for the osteoclast marker genes Trap and Ctsk. Moreover, Fc?RIIB-/- mice had higher level of serum TNF?, a proinflammatory cytokine. A soluble TNF? receptor, etanercept, prevented cancellous bone loss in Fc?RIIB-/- mice. Our results indicate that Fc?RIIB indirectly regulates cancellous bone homeostasis following SLE development. Fc?RIIB deletion induces inflammatory bone loss due to increased TNF?-mediated bone resorption without any change in bone formation in mice with SLE-like syndrome.
Project description:Polygenic autoimmune diseases, such as systemic lupus erythematosus (SLE), are a significant cause of morbidity and mortality worldwide. In recent years, functionally important genetic polymorphisms conferring susceptibility to SLE have been identified, but the evolutionary pressures driving their retention in the gene pool remain elusive. A defunctioning, SLE-associated polymorphism of the inhibitory receptor FcgammaRIIb is found at an increased frequency in African and Asian populations, broadly corresponding to areas where malaria is endemic. Here, we show that FcgammaRIIb-deficient mice have increased clearance of malarial parasites (Plasmodium chabaudi chabaudi) and develop less severe disease. In vitro, the human lupus associated FcgammaRIIb polymorphism enhances phagocytosis of Plasmodium falciparum-infected erythrocytes. These results demonstrate that FcgammaRIIb is important in controlling the immune response to malarial parasites and suggests that the higher frequency of human FcgammaRIIb polymorphisms predisposing to SLE in Asians and Africans may be maintained because these variants reduce susceptibility to malaria.
Project description:OBJECTIVES:Systemic lupus erythematosus (SLE) is a sexually dimorphic autoimmune disease which is more common in women, but affected men often experience a more severe disease. The genetic basis of sexual dimorphism in SLE is not clearly defined. A study was undertaken to examine sex-specific genetic effects among SLE susceptibility loci. METHODS:A total of 18 autosomal genetic susceptibility loci for SLE were genotyped in a large set of patients with SLE and controls of European descent, consisting of 5932 female and 1495 male samples. Sex-specific genetic association analyses were performed. The sex-gene interaction was further validated using parametric and non-parametric methods. Aggregate differences in sex-specific genetic risk were examined by calculating a cumulative genetic risk score for SLE in each individual and comparing the average genetic risk between male and female patients. RESULTS:A significantly higher cumulative genetic risk for SLE was observed in men than in women. (P=4.52x10-8) A significant sex-gene interaction was seen primarily in the human leucocyte antigen (HLA) region but also in IRF5, whereby men with SLE possess a significantly higher frequency of risk alleles than women. The genetic effect observed in KIAA1542 is specific to women with SLE and does not seem to have a role in men. CONCLUSIONS:The data indicate that men require a higher cumulative genetic load than women to develop SLE. These observations suggest that sex bias in autoimmunity could be influenced by autosomal genetic susceptibility loci.
Project description:Autoimmune disease is 4 times more common in women than men. This bias is largely unexplained. Female skin is "autoimmunity prone," showing upregulation of many proinflammatory genes, even in healthy women. We previously identified VGLL3 as a putative transcription cofactor enriched in female skin. Here, we demonstrate that skin-directed overexpression of murine VGLL3 causes a severe lupus-like rash and systemic autoimmune disease that involves B cell expansion, autoantibody production, immune complex deposition, and end-organ damage. Excess epidermal VGLL3 drives a proinflammatory gene expression program that overlaps with both female skin and cutaneous lupus. This includes increased B cell-activating factor (BAFF), the only current biologic target in systemic lupus erythematosus (SLE); IFN-?, a key inflammatory mediator in cutaneous lupus; and CXCL13, a biomarker of early-onset SLE and renal involvement. Our results demonstrate that skin-targeted overexpression of the female-biased factor VGLL3 is sufficient to drive cutaneous and systemic autoimmune disease that is strikingly similar to SLE. This work strongly implicates VGLL3 as a pivotal orchestrator of sex-biased autoimmunity.