The study, led by Zhilan Li of Xiangya Hospital at Central South University in collaboration with Jena R. Wirth, C. Alex. Colvert, Rachael J. Werner, and Melissa A. Cunningham of the Medical University of South Carolina, set out to address a persistent gap in lupus research. Most work on estrogen signaling in autoimmunity has focused on lymphocytes, the adaptive immune cells that produce antibodies. Far less is known about how estrogen receptor variants behave in innate immune cells, the first responders of the immune system, or in structural cells such as those lining the kidney’s filtering units, which also participate in inflammatory signaling during lupus nephritis. Understanding these cells matters because innate immune activation, driven in part by immune complexes containing nucleic acids sensed through Toll-like receptor 7, is central to the pathology of systemic lupus erythematosus.

To dissect the contributions of the two receptor variants, the team used a transfection strategy in which cultured cells were given plasmids encoding either ERα66, ERα46, both variants in equal proportion, or an empty control vector. The full-length ERα66 contains all of the functional domains of the receptor, including the two activation function regions that recruit co-regulators to hormone-responsive genes. ERα46, by contrast, lacks the amino-terminal AF-1 domain entirely, which means it cannot engage the same set of transcriptional co-activators and may instead act as a modulator or even a dominant inhibitor of ERα66-driven transcription. Because both proteins are encoded by the same gene and differ only through alternative splicing, any divergent effects between them can be attributed to the presence or absence of specific protein domains rather than to different genes altogether.

The first cellular model was HMC3, a human microglial cell line derived from a male donor. Microglia are the resident immune cells of the central nervous system, and they are believed to play a critical role in neuropsychiatric or central nervous system lupus, one of the most devastating manifestations of the disease. When the researchers overexpressed ERα46 in these cells, they observed a clear promotion of cell proliferation, measured by EdU incorporation assays that detect cells in the act of DNA synthesis, alongside CCK-8 assays that track metabolic viability. Notably, both receptor variants ultimately decreased the levels of inflammatory cytokines, but the mechanism was sobering rather than protective: the apparent anti-inflammatory effect stemmed from reduced cell viability, meaning fewer surviving cells were available to churn out inflammatory mediators. This distinction between a genuine immunomodulatory effect and one that simply reflects cell loss is a technical point with major interpretive consequences for the field.

The picture shifted substantially when the team moved to a second myeloid model, the murine macrophage line RAW 264.7, also male-derived. Here, overexpressing ERα46 promoted cell viability but did not spur proliferation, a subtle but important dissociation between survival and division. More strikingly, when the macrophages were stimulated with a Toll-like receptor 7 agonist, both ERα66 and ERα46 promoted the expression of inflammatory cytokines. TLR7 is a sensor of single-stranded RNA, and its overactivity is tightly linked to lupus pathogenesis, since self-RNA contained in immune complexes can chronically activate this pathway in susceptible individuals. The finding that both receptor variants amplified TLR7-driven inflammation in macrophages directly contradicts the anti-inflammatory picture seen in microglia and underscores that estrogen receptor biology cannot be generalized across the innate immune compartment.

Stimulation experiments extended beyond TLR7. The researchers challenged the transfected cells with interferon-alpha, interferon-gamma, and lipopolysaccharide, three inflammatory triggers that represent distinct arms of innate immune activation: type I interferon signaling, which is a hallmark of lupus; type II interferon signaling; and bacterial endotoxin sensing through TLR4. Cytokine output was quantified at both the protein level, by enzyme-linked immunosorbent assay, and the messenger RNA level, by quantitative reverse transcription polymerase chain reaction, providing complementary confirmation of the transcriptional and secretory responses. The convergent message across these assays was that the two receptor variants are not interchangeable, and that their influence on inflammatory gene expression is highly dependent on which stimulus is applied and which cell is listening.

The most provocative results emerged from human renal mesangial cells, primary cells obtained from both male and female donors. Mesangial cells occupy a unique position in lupus nephritis. Although they are structural components of the glomerulus, the kidney’s blood-filtering unit, they display innate immune-like activities during injury, secreting cytokines and chemokines that recruit and amplify inflammatory attack on the kidney tissue. In mesangial cells from male donors, both ERα variants inhibited proliferation but had only a minimal effect on the inflammatory phenotype. In mesangial cells from female donors, however, ERα66 and ERα46 modulated the expression of multiple inflammatory cytokines, hinting at genuinely sex-specific functions of the receptor variants in the kidney. The authors are careful to note that these observations require validation with additional donors, since primary human cells carry inherent inter-individual variability, but the pattern is consistent with the broader hypothesis that estrogen signaling contributes to the female predominance of lupus.

Taken together, the findings dismantle the simple narrative in which estrogen is uniformly bad, or uniformly good, for people with lupus. Instead, the two major splice variants of estrogen receptor alpha act as context-dependent regulators whose effects on proliferation, survival, and cytokine production flip sign depending on the cellular setting. In microglia, the shorter variant encourages division; in macrophages, both variants fan the flames of TLR7-driven inflammation; in male mesangial cells, both variants restrain growth while leaving inflammation largely untouched; and in female mesangial cells, both variants reshape the cytokine landscape. For clinicians and drug developers, this heterogeneity is both a warning and an opportunity. Therapies that broadly block estrogen receptor signaling could produce very different outcomes in the brain, the blood, and the kidney, while strategies that selectively target ERα46, or exploit its missing AF-1 domain, might one day allow tissue-specific tuning of the immune response.

The study was supported by the National Institutes of Health through the National Institute of Arthritis and Musculoskeletal and Skin Diseases, with additional support from the China Scholarship Council, and the authors acknowledge Professor Geoffrey Greene of the University of Chicago for providing the human ERα plasmids. While the work remains at the in vitro stage, and the authors themselves caution that the sex-associated differences in mesangial cells await confirmation across larger donor panels, the research provides a mechanistic framework for a question that has shadowed lupus medicine for generations: why a disease of dysregulated immunity strikes women so disproportionately. The answer, it now appears, is written not just in the hormone itself but in the alternative splice forms of its receptor, and in the distinct ways that microglia, macrophages, and mesangial cells interpret the same molecular message.

Subject of Research: Differential effects of estrogen receptor alpha splice variants ERα66 and ERα46 on proliferation and inflammatory responses in in vitro models of systemic lupus erythematosus inflammation.

Article Title: Estrogen receptor alpha variants differentially influence proliferation and inflammatory responses in in vitro models of lupus inflammation

Article References: Li, Z., Wirth, J. R., Colvert, C. A., Werner, R. J., & Cunningham, M. A. (2026). Estrogen receptor alpha variants differentially influence proliferation and inflammatory responses in in vitro models of lupus inflammation. Biology of Sex Differences. https://doi.org/10.1186/s13293-026-00990-x

Image Credits: AI Generated

DOI: 10.1186/s13293-026-00990-x

Keywords: estrogen receptor alpha, ERα46, lupus, systemic lupus erythematosus, autoimmune disease, microglia, macrophages, mesangial cells, TLR7, inflammatory cytokines, sex differences, splice variants

Systemic lupus erythematosus is a complex autoimmune disease in which the immune system turns against the body’s own tissues, attacking the skin, joints, kidneys, blood cells, and other organs with chronic inflammation. Genetics plays a substantial role in determining who develops lupus, and many of the genetic regions associated with disease risk have been catalogued for years through large-scale association studies. A major challenge, however, has been moving from statistical association to biological mechanism. Knowing that a stretch of DNA correlates with disease risk says little about what the inherited variant actually does inside immune cells, or why it increases susceptibility not just to lupus but frequently to several autoimmune conditions at once. The new study addresses that gap directly by dissecting what one of the most prevalent lupus-risk haplotypes does to the function of IRF7, a gene whose protein product orchestrates the production of type I interferons, the chemical alarm signals that mobilize antiviral defense throughout the body.

IRF7 helps cells respond to viral infection by activating the production of type I interferons, most notably interferon-alpha, or IFN-α. These signaling molecules are essential components of innate immunity, spreading rapidly from infected cells to their neighbors and instructing them to enter a defensive state that makes viral replication far more difficult. But type I interferon signaling has long been strongly implicated in lupus as well. Many patients with lupus carry a chronically elevated interferon activity in their blood, a phenomenon so consistent that researchers refer to it as the ‘interferon signature,’ and therapies designed to block this pathway have already been approved for treating the disease. The Cincinnati Children’s team reasoned that the connection between these two observations, effective antiviral defense on one side and pathological interferon activity on the other, might run through the genetic variation within IRF7 itself.

That reasoning proved correct. The researchers found that the lupus risk haplotype increases IRF7-dependent induction of IFN-α. In practical terms, individuals carrying this common genetic configuration mount a stronger interferon response under the conditions studied, meaning their antiviral alarm system can ring louder and faster when a viral threat is detected. That heightened responsiveness can be a genuine asset in fighting infection. Yet the very same biology can also promote excessive or inappropriate immune activation, tipping the balance of the immune system toward the self-directed inflammation that defines lupus. The study thereby exposes what the authors describe as an important biological tradeoff, in which a single inherited configuration of the immune system confers both an advantage and a vulnerability depending on context.

The evolutionary implications are striking. A more vigorous antiviral immune response may have been enormously beneficial throughout human history, particularly during eras when infectious diseases represented one of the greatest threats to survival. Populations in which individuals responded more forcefully to viral invasion may have withstood epidemics that devastated others. But an immune system that is especially sensitive to viral signals also carries a greater inherent tendency to cross the line from protective immunity into autoimmunity. The new findings therefore suggest that at least some lupus risk variants should not be thought of as ‘defective’ versions of immune genes at all. Instead, they represent versions of the immune system that simply perform differently, offering an advantage in one environment while increasing disease susceptibility in another. This reframing helps explain why such variants remained common: natural selection may have favored them precisely because of the very biology that now contributes to autoimmune disease.

Sam Virolainen, PhD, first author of the study and a graduate of the Immunology Graduate Program at Cincinnati Children’s, said the findings help explain why a genetic variant linked to lupus remained so common and how, biologically, it affects the immune system more broadly. Reflecting on the training that shaped the work, Virolainen noted an appreciation gained during doctoral research in the Kottyan and Weirauch laboratories that many genetic risk factors can contribute to multiple diseases, especially when the immune system is involved. That multiscale perspective, spanning molecular regulation, cellular signaling, and population genetics, is evident throughout the study’s design and interpretation, and it underscores how a variant’s effect can ripple across very different levels of biological organization.

The work also feeds into a larger and still-unresolved question: how inherited genetic risk interacts with viral infection in the development of autoimmunity. For years, researchers have recognized a strong relationship between Epstein-Barr virus, or EBV, and lupus. Nearly everyone is exposed to EBV at some point in their lives, yet only a small fraction of those exposed ever develop lupus. Genetics may help explain why the consequences of the same viral exposure differ so dramatically from one person to the next. The research team’s previous work examined how viral proteins, including those produced by EBV, interact with the human genome at regions associated with autoimmune disease. The new IRF7 study approaches the gene-virus relationship from the opposite direction. Rather than asking how a virus interacts with genetically susceptible cells, the team asked how inherited genetic variation changes the antiviral response itself, and the answer places both processes on converging molecular roads.

‘Together, these studies support a model in which genetic susceptibility and viral exposure are not independent risk factors. They can converge on the same regulatory pathways,’ said Kottyan. In this model, a person’s inherited genome shapes how strongly their immune system reacts to infection, while viral infection in turn activates molecular pathways that are already tuned by that genetic makeup. In some individuals, the interaction of the two may explain how an ordinary antiviral immune response develops into chronic autoimmune inflammation. The lupus-risk IRF7 haplotype amplifies the interferon arm of this convergence, but the principle likely extends to other immune genes and other autoimmune conditions, offering a framework in which genetics and environment are treated as intertwined rather than separate contributors to disease.

The study does not immediately change how lupus is diagnosed or treated, and carrying this genetic haplotype does not mean that someone will develop the disease. Lupus arises from the combined effects of many genetic variants together with environmental exposures and other biological factors, and no single inherited element is decisive on its own. However, the research demonstrates how scientists can move beyond simply identifying genetic risk factors to understanding, at a mechanistic level, how those variants alter immune function. Studies of this kind help build a foundation for future research into what drives disease and why its course differs from person to person. ‘I am hopeful that our work will increase our understanding of not just lupus biology but other diseases with similar genetic and immunologic complexities,’ said Virolainen. Many disease-associated variants have already been identified, but their biological effects remain unclear. By clarifying the molecular pathways involved, the Cincinnati Children’s team and their collaborators, who spanned institutions across 13 U.S. states and territories and six countries, may ultimately help guide therapies that target disease more precisely while preserving the normal antiviral function that those same variants evolved to protect.

Subject of Research: Genetic and immunological mechanisms linking a common IRF7 haplotype to enhanced antiviral defense and increased lupus risk

Article Title: When Antiviral Defense and Autoimmunity Collide: New Insights into Lupus Genetics

Article References: When Antiviral Defense and Autoimmunity Collide: New Insights into Lupus Genetics. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: lupus, systemic lupus erythematosus, IRF7, interferon-alpha, autoimmunity, antiviral immunity, genetic haplotype, Epstein-Barr virus, transcription factor, immune genetics, Cincinnati Children's, interferon signature