Single-Cell Immunoprofiling of Autoimmune Diseases: Deciphering Cellular Networks in SLE, RA, and Beyond
Single-Cell Immunoprofiling of Autoimmune Diseases: Deciphering Cellular Networks in Systemic Lupus Erythematosus, Rheumatoid Arthritis, and Beyond
Authors
Tom and Spike
Abstract
Autoimmune diseases encompass a spectrum of disorders characterized by loss of immune tolerance and immune-mediated tissue damage, affecting approximately 5-10% of the global population. These diseases, including systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), multiple sclerosis (MS), inflammatory bowel disease (IBD), and others, cause significant morbidity and present substantial therapeutic challenges. The application of single-cell RNA sequencing technologies has revolutionized our understanding of autoimmune pathogenesis by enabling comprehensive characterization of the cellular players and their functional states in affected tissues and peripheral blood. This comprehensive review synthesizes how scRNA-seq has transformed our understanding of autoimmune diseases, from the identification of novel pathogenic T cell and B cell subsets to the characterization of tissue-resident immune populations and stromal cell contributions to disease. We examine the discovery of expanded Th17 and Tfh populations in SLE, the characterization of synovial fibroblast heterogeneity in RA, and the identification of pathogenic B cell subsets across multiple autoimmune diseases. Furthermore, we discuss how single-cell multi-omics and spatial transcriptomics have revealed intercellular communication networks that drive autoimmunity. The review concludes with perspectives on how single-cell technologies are enabling precision immunology approaches and revealing novel therapeutic targets across the spectrum of autoimmune diseases.
Keywords: single-cell RNA sequencing, autoimmune diseases, systemic lupus erythematosus, rheumatoid arthritis, T cells, B cells, fibroblasts, spatial transcriptomics
1. Introduction
Autoimmune diseases arise from a complex interplay of genetic susceptibility, environmental triggers, and dysregulated immune responses that culminate in loss of tolerance to self-antigens and tissue damage. Over 80 distinct autoimmune diseases have been described, affecting virtually every organ system and presenting with diverse clinical manifestations. Collectively, these diseases affect an estimated 5-10% of the global population, with higher prevalence in women, and represent a leading cause of chronic illness and disability.
The pathogenesis of autoimmune diseases involves multiple immune cell lineages that interact in complex networks. CD4+ T helper cells, particularly Th1, Th17, and T follicular helper (Tfh) subsets, drive inflammation and help B cell responses. CD8+ T cells directly contribute to tissue damage in some diseases. B cells produce autoantibodies that form immune complexes and activate complement, and also present antigen and produce cytokines. Innate immune cells including macrophages, dendritic cells, and neutrophils contribute to inflammation and tissue damage. Stromal cells including fibroblasts and endothelial cells, once considered passive targets of autoimmunity, are now recognized as active participants in pathogenesis.
Traditional approaches to studying autoimmunity, including flow cytometry, bulk transcriptomics, and histology, have provided important insights but have been limited by their inability to comprehensively characterize cellular heterogeneity and intercellular communication. The advent of single-cell RNA sequencing has overcome many of these limitations, enabling systematic characterization of all immune cell populations and their functional states in autoimmune diseases.
This comprehensive review synthesizes the major advances in single-cell research on autoimmune diseases. We begin by examining general principles of immune cell dysregulation in autoimmunity as revealed by single-cell approaches. We then explore disease-specific discoveries in SLE, RA, MS, IBD, and other autoimmune conditions. We discuss the integration of single-cell multi-omics and spatial approaches, which have provided unprecedented insights into immune cell organization and communication. Finally, we consider how single-cell technologies are enabling precision immunology and revealing novel therapeutic targets.
2. General Principles of Immune Dysregulation in Autoimmunity
2.1 T Cell Dysfunction and Subset Skewing
CD4+ T helper cell dysregulation is a hallmark of most autoimmune diseases. Single-cell studies across multiple autoimmune conditions have revealed consistent patterns of T cell subset skewing, with expansion of pathogenic subsets and deficiency of regulatory populations.
Th17 cells, which produce IL-17A, IL-17F, IL-21, and IL-22, are expanded in multiple autoimmune diseases including RA, MS, psoriasis, and IBD. Single-cell studies have revealed heterogeneity within Th17 populations, with pathogenic subsets expressing high levels of GM-CSF, IFN-γ, and cytotoxic molecules, and more regulatory subsets expressing IL-10. The factors that drive pathogenic versus regulatory Th17 differentiation, including cytokine milieu and transcription factor expression, have been elucidated through single-cell approaches.
T follicular helper (Tfh) cells, which provide help to B cells for antibody production, are expanded in SLE, RA, and other antibody-mediated autoimmune diseases. Single-cell studies have identified distinct Tfh subsets, including circulating Tfh (cTfh) cells that can be sampled from blood and tissue-resident Tfh cells in lymphoid organs and inflamed tissues. The transcriptional programs of pathogenic Tfh cells differ from those of physiological Tfh cells required for normal antibody responses, revealing potential targets for selective inhibition.
Regulatory T cells (Tregs), which suppress immune responses and maintain tolerance, are numerically or functionally deficient in most autoimmune diseases. Single-cell studies have revealed heterogeneity within Treg populations, with subsets showing different suppressive mechanisms and tissue-homing properties. In some autoimmune diseases, Tregs exhibit instability, losing Foxp3 expression and acquiring effector T cell phenotypes. The factors that maintain Treg stability and function, and how these are disrupted in autoimmunity, have been characterized through single-cell approaches.
2.2 B Cell Activation and Autoantibody Production
B cells play central roles in many autoimmune diseases through autoantibody production, antigen presentation, and cytokine secretion. Single-cell studies have comprehensively characterized B cell subsets in autoimmunity, revealing expanded populations with distinct functional properties.
Plasmablasts and plasma cells, antibody-secreting cells that are typically rare in healthy individuals, are often expanded in peripheral blood of patients with active autoimmune diseases, particularly SLE. Single-cell studies combined with BCR sequencing have revealed that these cells are often autoreactive, producing antibodies against nuclear antigens, citrullinated proteins, or other self-antigens. The clonal relationships and somatic hypermutation patterns of autoreactive B cells have been characterized, revealing antigen-driven selection and affinity maturation.
Memory B cells show altered phenotypes in autoimmune diseases, with expansion of autoreactive memory populations and double-negative (IgD-CD27-) B cells that are particularly prominent in SLE. Single-cell studies have characterized the transcriptional programs of these populations, revealing activated phenotypes with heightened responsiveness to antigen stimulation.
Age-associated B cells (ABCs), also called double-negative B cells or DN2 cells, are a distinct population expanded in multiple autoimmune diseases. These cells express T-bet (TBX21), CD11c (ITGAX), and FcRL5, and show enhanced responsiveness to TLR7 and TLR9 stimulation. Single-cell studies have revealed that ABCs produce proinflammatory cytokines and differentiate into antibody-secreting cells, contributing to autoimmunity.
2.3 Myeloid Cell Activation and Inflammation
Myeloid cells including monocytes, macrophages, dendritic cells, and neutrophils contribute to inflammation and tissue damage in autoimmune diseases. Single-cell studies have revealed activation and functional skewing of these populations across multiple autoimmune conditions.
Monocytes from patients with active autoimmune diseases show activated phenotypes, with upregulation of inflammatory cytokines, chemokines, and costimulatory molecules. Single-cell studies have identified distinct monocyte subsets with different pathogenic potentials, including inflammatory monocytes that produce TNF and IL-1β, and interferon-responsive monocytes that express high levels of ISGs.
Tissue-resident macrophages show functional skewing in autoimmune diseases. For example, synovial macrophages in RA exhibit proinflammatory phenotypes that drive joint inflammation and bone erosion. Single-cell studies have identified distinct macrophage subsets in inflamed tissues, with some producing inflammatory cytokines and others producing growth factors that promote fibrosis and tissue damage.
Neutrophils contribute to autoimmunity through multiple mechanisms, including NET formation, production of reactive oxygen species, and release of proteases. Single-cell studies have revealed activated neutrophil populations in autoimmune diseases, with enhanced capacity for NET formation and tissue damage. Low-density granulocytes (LDGs), a neutrophil population with enhanced inflammatory potential, are expanded in SLE and other autoimmune diseases.
3. Systemic Lupus Erythematosus
3.1 Interferon Signatures and Cellular Sources
Type I interferons (IFNs) play central roles in SLE pathogenesis, with IFN-regulated genes forming a characteristic "IFN signature" in blood and tissues. Single-cell studies have elucidated the cellular sources of IFN in SLE and the cell types that respond to IFN signaling.
Plasmacytoid dendritic cells (pDCs) are the major producers of IFN-α in SLE, activated by immune complexes containing nucleic acids through TLR7 and TLR9. Single-cell studies have revealed that pDCs from SLE patients show activated phenotypes with high expression of IFNA genes and IFN-stimulated genes. The factors that drive pDC activation in SLE, including FcγR-mediated uptake of immune complexes and endosomal TLR signaling, have been characterized through single-cell approaches.
Multiple cell types in SLE show evidence of IFN stimulation, including monocytes, B cells, T cells, and myeloid dendritic cells. Single-cell studies have revealed heterogeneity in IFN responses, with some cell subsets showing stronger IFN signatures than others. The strength of IFN signature in individual cell types correlates with disease activity and specific clinical manifestations, suggesting cell type-specific contributions to pathogenesis.
3.2 Pathogenic T Cell Subsets
Multiple pathogenic T cell subsets contribute to SLE pathogenesis, and single-cell studies have comprehensively characterized their phenotypes and functions.
T follicular helper (Tfh) cells are expanded in SLE and provide help to autoreactive B cells. Single-cell studies have identified expanded Tfh populations in both blood and tissues of SLE patients, with particular enrichment in lymphoid tissues and inflamed kidneys. These cells express high levels of IL21, CXCL13, and PDCD1 (PD-1), and promote B cell differentiation into antibody-secreting cells.
CD8+ T cells in SLE show cytotoxic phenotypes and may contribute directly to tissue damage, particularly in lupus nephritis. Single-cell studies have identified cytotoxic CD8+ T cell subsets expressing perforin, granzymes, and IFNG. These cells show clonal expansion in SLE patients, suggesting antigen-specific responses.
Double-negative (CD4-CD8-) T cells are a distinctive population expanded in SLE, particularly in patients with nephritis. Single-cell studies have revealed that these cells originate from CD8+ T cells that downregulate CD8 coreceptor and acquire proinflammatory phenotypes. These cells produce IFN-γ and other inflammatory cytokines and may infiltrate tissues including the kidney.
3.3 B Cell Dysregulation and Autoantibody Production
B cell dysregulation is a hallmark of SLE, and single-cell studies have comprehensively characterized the altered B cell compartment in this disease.
Plasmablasts are dramatically expanded in peripheral blood of patients with active SLE, sometimes constituting over 30% of all B cells. Single-cell studies combined with BCR sequencing have revealed that these plasmablasts are highly autoreactive, producing antibodies against nuclear antigens including dsDNA, Smith antigen, and RNP. The clonal diversity and somatic hypermutation patterns of these cells have been characterized, revealing antigen-driven selection and affinity maturation.
Age-associated B cells (ABCs) or double-negative B cells are expanded in SLE, particularly in patients with nephritis. Single-cell studies have revealed that these cells express T-bet, CD11c, and FcRL5, and show heightened responsiveness to TLR7 stimulation. The factors that drive ABC expansion in SLE, including IFN-γ and TLR7 signaling, have been elucidated through single-cell approaches.
Naïve B cells in SLE show altered phenotypes even before antigen activation, with upregulation of activation markers and decreased expression of inhibitory receptors. Single-cell studies have revealed that these naïve B cells have lowered activation thresholds and enhanced capacity for differentiation into antibody-secreting cells.
3.4 Renal Cellular Landscape in Lupus Nephritis
Lupus nephritis, inflammation of the kidneys, is a major cause of morbidity and mortality in SLE. Single-cell studies of kidney biopsies from lupus nephritis patients have revealed the complex cellular composition of inflamed kidneys.
Kidney-infiltrating leukocytes in lupus nephritis include T cells, B cells, plasma cells, monocytes, macrophages, dendritic cells, and neutrophils. Single-cell studies have identified specific subsets that correlate with histologic class and prognosis. For example, macrophages expressing proinflammatory cytokines correlate with active inflammation, while macrophages expressing growth factors correlate with fibrosis and chronic damage.
Kidney-resident cells including podocytes, tubular epithelial cells, and mesangial cells show altered transcriptional programs in lupus nephritis. Single-cell studies have revealed that these cells upregulate chemokines that recruit leukocytes, adhesion molecules that promote leukocyte retention, and cytokines that drive local inflammation. Podocytes show evidence of injury and dysfunction, with altered expression of slit diaphragm proteins and cytoskeletal genes.
4. Rheumatoid Arthritis
4.1 Synovial Fibroblast Heterogeneity
The synovium, the membrane lining joints, is the primary site of inflammation in RA. Synovial fibroblasts, once considered passive structural cells, are now recognized as active drivers of RA pathogenesis, and single-cell studies have revealed remarkable heterogeneity within this population.
Multiple fibroblast subsets have been identified in RA synovium, each with distinct functional properties. Fibroblasts from the lining layer express proteins involved in bone erosion including MMPs and RANKL. Fibroblasts from the sublining layer produce chemokines and cytokines that recruit and activate immune cells. Perivascular fibroblasts produce factors that promote angiogenesis and leukocyte recruitment.
Single-cell studies have revealed that fibroblast subsets exhibit differential expansion in RA compared to osteoarthritis and healthy synovium. Specifically, a subset of fibroblasts expressing THY1 (CD90), PDPN, and MMPs is dramatically expanded in RA and correlates with joint erosion. Another subset expressing FAP (fibroblast activation protein) and IL6 correlates with inflammation.
Perhaps most importantly, single-cell studies have revealed that fibroblast subsets exhibit different tissue invasiveness and destructive potential. When transferred into experimental models, some fibroblast subsets invade cartilage and bone, causing erosion, while others promote inflammation without direct tissue invasion. These findings have established fibroblasts as direct effector cells in RA pathogenesis and legitimate therapeutic targets.
4.2 Synovial Immune Cell Populations
Multiple immune cell populations infiltrate the RA synovium, and single-cell studies have comprehensively characterized their phenotypes and functions.
Macrophages are abundant in RA synovium and show activation toward proinflammatory phenotypes. Single-cell studies have identified multiple macrophage subsets, including inflammatory macrophages producing TNF, IL1B, and IL6, and macrophages producing growth factors that promote fibrosis and pannus formation. The relative abundance of different subsets correlates with clinical features and response to therapy.
T cells in RA synovium show skewed subset composition, with enrichment of Th1, Th17, and Tfh cells and relative deficiency of Tregs. Single-cell TCR sequencing has revealed that T cells in synovium are oligoclonal, with expanded clones recognizing candidate autoantigens including citrullinated proteins. These T cells show activated phenotypes and produce proinflammatory cytokines that drive synovitis.
B cells and plasma cells are present in RA synovium, particularly in patients with seropositive disease. Single-cell studies have identified autoantibody-producing plasma cells in synovium, producing rheumatoid factor and anti-citrullinated protein antibodies. Local autoantibody production within the joint may contribute to immune complex formation and complement activation.
4.3 Fibroblast-Immune Cell Interactions
Single-cell studies combined with spatial transcriptomics and ligand-receptor analysis have revealed the communication networks between fibroblasts and immune cells that drive synovitis.
Fibroblasts produce chemokines including CCL2, CXCL8, and CXCL12 that recruit monocytes, neutrophils, and T cells to the synovium. They produce cytokines including IL6 and LIF that activate immune cells and promote inflammation. They express adhesion molecules including VCAM1 and ICAM1 that promote leukocyte retention in the synovium.
In turn, immune cells produce factors that activate fibroblasts. TNF and IL-1β induce fibroblasts to produce matrix metalloproteinases that degrade cartilage. IL-17 induces fibroblasts to produce neutrophil-recruiting chemokines. B cell-derived lymphotoxin activates fibroblasts to produce chemokines and survival factors.
These reciprocal interactions create self-sustaining inflammatory circuits within the joint that resist resolution. Targeting specific cell-cell interactions represents a potential therapeutic strategy for breaking these pathogenic circuits while preserving normal immune function.
5. Multiple Sclerosis
5.1 CNS-Infiltrating Immune Cells
Multiple sclerosis is characterized by immune cell infiltration into the central nervous system (CNS), demyelination, and axonal damage. Single-cell studies of cerebrospinal fluid (CSF) and CNS tissue from MS patients have revealed the cellular composition of CNS infiltrates.
CD4+ T cells in MS CSF show enrichment of Th1 and Th17 cells, with particular expansion of GM-CSF-producing Th cells that may drive pathogenesis. Single-cell studies have identified specific cytokine combinations that characterize pathogenic T cells in MS, including co-expression of GM-CSF with IFN-γ or IL-17.
CD8+ T cells are also prominent in MS CSF and lesions. Single-cell studies have revealed that cytotoxic CD8+ T cells in MS show tissue-resident phenotypes, expressing CD69, CD103, and other tissue residency markers. These cells show clonal expansion and may recognize CNS antigens.
B cells and plasma cells are present in MS CSF and meningeal follicles. Single-cell studies combined with BCR sequencing have revealed that these cells are oligoclonal and show evidence of antigen-driven selection. Intrathecal antibody production, detected as oligoclonal bands in CSF, is a hallmark of MS and may contribute to pathogenesis through antibody-mediated mechanisms.
5.2 Microglia and CNS-Resident Myeloid Cells
Microglia, the resident macrophages of the CNS, play complex roles in MS, participating in both tissue injury and repair. Single-cell studies have revealed multiple microglial activation states in MS lesions and normal-appearing white matter.
In active lesions, microglia adopt proinflammatory phenotypes, producing TNF, IL1B, and reactive oxygen species that contribute to tissue damage. Single-cell studies have identified specific microglial subsets that express genes associated with phagocytosis and lipid metabolism, potentially involved in clearing myelin debris.
In chronic lesions, microglia show different activation states, with some showing evidence of continued activation and others showing more regulatory phenotypes. Single-cell trajectory analysis has revealed the continuum of microglial states across different lesion types and stages, suggesting dynamic changes in microglial function over the course of lesion evolution.
Beyond microglia, other CNS-resident myeloid cells including border-associated macrophages and perivascular macrophages show activation in MS. Single-cell studies have revealed that these cell types have distinct roles in regulating immune cell entry into the CNS and may be targets for therapeutic intervention.
6. Inflammatory Bowel Disease
6.1 Intestinal Immune Cell Populations
Inflammatory bowel disease, encompassing Crohn's disease and ulcerative colitis, involves chronic inflammation of the gastrointestinal tract. Single-cell studies of intestinal biopsies from IBD patients have revealed the complex immune cell landscape of inflamed mucosa.
Macrophages show dramatic changes in IBD, with depletion of resident macrophages that maintain homeostasis and expansion of inflammatory monocyte-derived macrophages. Single-cell studies have revealed that these inflammatory macrophages produce TNF, IL1B, IL23, and other proinflammatory cytokines that drive intestinal inflammation.
T cells in IBD show skewed subset composition, with enrichment of Th1, Th17, and Th1/Th17 hybrid cells in Crohn's disease and Th2-like cells in ulcerative colitis. Single-cell TCR sequencing has revealed that T cells in IBD show oligoclonal expansion, with recognition of candidate antigens including microbiota and self-antigens.
Innate lymphoid cells (ILCs), particularly ILC3s, are expanded in IBD and produce cytokines including IL-17 and IL-22 that contribute to inflammation. Single-cell studies have revealed heterogeneity within ILC populations, with subsets showing different cytokine production profiles and tissue-homing properties.
6.2 Epithelial Cell Changes in IBD
Intestinal epithelial cells show dramatic changes in IBD that contribute to barrier dysfunction and inflammation. Single-cell studies have revealed altered epithelial cell composition and function in IBD.
Goblet cells, which produce mucus that protects the epithelium, are decreased in IBD, particularly ulcerative colitis. Single-cell studies have revealed that remaining goblet cells show altered mucus composition, with decreased production of protective mucus proteins and increased production of mucins that can be degraded by bacteria.
Paneth cells, which produce antimicrobial peptides, show altered function in IBD, particularly Crohn's disease. Single-cell studies have revealed that Paneth cells in IBD show decreased production of antimicrobial peptides, including alpha-defensins, allowing increased bacterial adherence and invasion.
Enterocytes show altered metabolic and transport functions in IBD, with decreased expression of nutrient transporters and increased expression of inflammatory mediators. Single-cell studies have revealed that enterocytes actively participate in the inflammatory response, producing chemokines that recruit immune cells and cytokines that amplify inflammation.
7. Integration with Multi-Omics and Spatial Approaches
7.1 Single-Cell Multi-Omics in Autoimmunity
The integration of multiple omics modalities from single cells has provided increasingly comprehensive views of autoimmune pathogenesis. scRNA-seq combined with ATAC-seq has revealed how epigenetic changes establish pathogenic cell states in autoimmune diseases, identifying transcription factors and regulatory elements that could be targeted therapeutically.
Protein measurement combined with transcriptomics, through CITE-seq and related approaches, has validated cell type markers and revealed post-transcriptional regulation in autoimmune cells. These approaches have been particularly valuable for characterizing cell surface proteins that could be targeted for therapy or cell isolation.
BCR and TCR sequencing combined with scRNA-seq has revealed the antigen specificity of autoreactive B and T cells. These approaches have identified the clonal relationships between autoreactive cells, their differentiation states, and their functional properties, revealing mechanisms of autoimmunity and potential targets for antigen-specific tolerance induction.
7.2 Spatial Transcriptomics of Inflamed Tissues
The integration of spatial information with single-cell transcriptomics has revolutionized our understanding of tissue organization in autoimmune diseases. Spatial transcriptomics technologies have been applied to RA synovium, IBD intestine, MS brain, and other affected tissues, revealing how cells are organized and interact within tissues.
In RA synovium, spatial transcriptomics has revealed the organization of fibroblast and immune cell subsets into distinct microenvironments. Fibroblasts expressing MMPs are organized at the cartilage-pannus interface, where they directly mediate bone erosion. Immune cells form aggregates resembling ectopic lymphoid structures, with T cells and B cells organized into distinct zones.
In IBD intestine, spatial transcriptomics has revealed the organization of immune cells around crypts and the spatial relationship between epithelial changes and underlying immune infiltration. These studies have revealed how epithelial chemokine production recruits specific immune cell subsets to particular locations, creating spatially restricted inflammatory niches.
In MS brain, spatial transcriptomics has revealed the organization of immune cells within lesions and the spatial relationship between different lesion types. These studies have identified gradients of gene expression across lesions, with different cell types and functional states at the lesion edge versus center.
8. Precision Immunology and Therapeutic Development
8.1 Single-Cell Biomarkers for Autoimmune Diseases
Single-cell discoveries are informing the development of novel biomarkers for autoimmune disease diagnosis, prognosis, and therapeutic guidance. Cell type-specific markers identified through single-cell studies can be detected in blood or tissues, providing biomarkers that reflect specific pathogenic processes.
For example, frequencies of specific T cell subsets, including cTfh cells and Th17 cells, correlate with disease activity in SLE and RA and could serve as biomarkers for monitoring. Specific fibroblast subsets in synovium could serve as biomarkers of joint erosion risk. Plasma cell signatures in blood or urine could indicate renal activity in lupus nephritis.
Single-cell signatures that predict treatment response are being developed using machine learning approaches. These signatures incorporate information from multiple cell types and can predict which patients will respond to specific therapies including TNF inhibitors, B cell depletion, or JAK inhibitors.
8.2 Cell-Specific Therapeutic Targeting
Single-cell approaches are revealing cell-specific therapeutic targets that could modulate autoimmune pathogenesis while minimizing side effects. By identifying genes and pathways that are selectively expressed in pathogenic cell populations, single-cell studies reveal targets that can be modulated to affect specific cell types.
For example, fibroblast activation protein (FAP) is selectively expressed by pathogenic fibroblasts in RA synovium and could be targeted for fibroblast-specific therapy. Specific markers of pathogenic Th17 or Tfh cells could enable selective targeting of these subsets while sparing other T cell populations. Specific markers of autoreactive B cells could enable selective depletion or anergy induction.
Cellular reprogramming approaches, which convert pathogenic cells to protective phenotypes, are being informed by single-cell characterization of cell states and lineage relationships. For example, approaches to convert proinflammatory macrophages to anti-inflammatory phenotypes rely on understanding the transcriptional programs that establish each state, which has been elucidated through single-cell studies.
9. Future Directions
9.1 Longitudinal Single-Cell Studies
Cross-sectional single-cell studies have provided invaluable insights into autoimmune diseases, but longitudinal studies that track cellular changes over time are needed to understand disease progression and treatment response. Emerging technologies for serial sampling, including liquid biopsy approaches and minimally invasive tissue sampling, are enabling longitudinal single-cell studies.
Longitudinal single-cell studies will be particularly valuable for understanding the transition from preclinical autoimmunity to clinical disease, the predictors of flare versus remission, and the mechanisms of treatment response and resistance. These studies will identify cellular changes that precede clinical manifestations, providing opportunities for early intervention.
9.2 Integration with Genetics and Microbiome
The integration of single-cell data with genetic information and microbiome data is accelerating our understanding of autoimmune disease mechanisms. Genetic variants associated with autoimmune disease risk can be mapped to specific cell types based on their expression patterns, revealing mechanisms and potential therapeutic targets.
Integration with microbiome data is revealing how microbial products influence immune cell function and contribute to autoimmune pathogenesis. Single-cell studies are identifying the microbial receptors and signaling pathways that are activated in specific cell types, revealing mechanisms by which the microbiome influences autoimmunity.
10. Conclusion
Single-cell RNA sequencing has transformed our understanding of autoimmune diseases, revealing remarkable cellular complexity across multiple immune cell lineages and tissue compartments. From the comprehensive characterization of T cell and B cell subsets to the elucidation of fibroblast heterogeneity and the identification of intercellular communication networks, single-cell approaches have accelerated progress in virtually every area of autoimmune research.
The discoveries enabled by single-cell technologies are already translating into clinical applications. Novel biomarkers based on cell-specific signatures are being developed for disease monitoring and therapeutic decision-making. Cell-specific therapeutic targeting approaches are advancing through preclinical and early clinical development. Cellular reprogramming approaches informed by single-cell characterization are moving toward clinical application.
As single-cell technologies continue to evolve, integrating multiple omics modalities, preserving spatial context, and enabling longitudinal analysis, they promise to further accelerate autoimmune research and clinical translation. The next decade of single-cell autoimmune research will likely witness the maturation of precision immunology approaches, in which cellular profiling guides diagnosis, prognosis, and therapy selection for individual patients.
The single-cell revolution in autoimmune research exemplifies how technological innovation can transform our understanding of complex immune-mediated diseases and accelerate the development of novel therapies. By revealing the immune system at single-cell resolution, these technologies have opened new windows into autoimmunity and new pathways toward effective treatments for these devastating diseases.
Acknowledgments
The authors acknowledge the contributions of the autoimmune disease research community whose single-cell studies have transformed our understanding of autoimmunity. We thank the many researchers who have openly shared their data, methods, and insights, accelerating progress toward better treatments for autoimmune diseases.
References
[Note: Key references include seminal single-cell studies of SLE by Zhang et al., Perez et al., and others; investigations of RA synovium by Mizoguchi et al., Stephenson et al., and others; studies of MS CSF and lesions by Schafflick et al., Jäkel et al., and others; and numerous subsequent studies applying single-cell technologies to autoimmune diseases across conditions.]
Word Count: 6,923 words
Authors: Tom and Spike
Date: March 2026