Investigating cellular dynamics and molecular pathways through single-cell RNA sequencing in an imiquimod-induced lupus-like model

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease characterized by dysregulated innate and adaptive immunity. Although topical imiquimod (IMQ) induction is a widely used TLR7-driven lupus-like model, its immune landscape at single-cell resolution remains incompletely defined. We established an IMQ-induced lupus-like mouse model and evaluated systemic autoimmunity and renal involvement by serologic, histopathologic, and immunofluorescence analyses. Splenic immune cells from IMQ-induced and WT mice were subjected to single-cell RNA sequencing (scRNA-seq), followed by integrated clustering, subset-specific re-clustering, differential expression, functional enrichment, RNA velocity/PAGA trajectory inference, cell–cell communication analysis, and regulon activity profiling. Topical IMQ induction elicited lupus-like features, including splenomegaly, increased autoantibody levels, glomerular hypercellularity, and enhanced glomerular IgG/C3 deposition. Integrated scRNA-seq analysis of 33,091 splenic immune cells resolved eight major immune compartments and revealed marked compositional remodeling after IMQ induction, characterized by expansion of neutrophils, macrophages, and plasma cells and relative reduction of lymphocyte compartments. Re-clustering analysis showed that B cells underwent activation reprogramming, plasma cell-skewed differentiation, and dynamic progression from marginal zone to follicular and plasma-cell trajectories. T-cell analysis revealed redistribution from naïve/central memory states toward effector, proliferative, Tfh, and tissue-resident–associated states. Within the myeloid compartment, dendritic cells were selectively remodeled toward interferon- and inflammation-associated subsets, whereas neutrophils displayed enrichment of distinct inflammatory states and continuous trajectory progression. Cell–cell communication analysis demonstrated a denser and more extensive immune interaction network in IMQ-induced mice, dominated by monocytes, macrophages, and dendritic cells through inflammatory signaling axes including IL6, TNF, and CCL. Regulon activity analysis further identified profound transcriptional reprogramming centered on myeloid compartments, particularly neutrophils. Our study provides a single-cell atlas of the splenic immune landscape in the IMQ-induced lupus-like model and shows that IMQ drives coordinated remodeling across lymphoid and myeloid compartments, accompanied by intensified intercellular communication and transcriptional regulatory reprogramming. These findings highlight the central role of the TLR7/interferon-driven myeloid axis in lupus-like immune pathology and provide a high-resolution framework for mechanistic studies of SLE-related immune dysregulation. We provide a single-cell atlas of the splenic immune landscape in the IMQ-induced lupus-like model. IMQ induces coordinated remodeling of B cells, T cells, dendritic cells, and neutrophils, accompanied by intensified myeloid-centered intercellular communication and transcriptional regulatory reprogramming. These findings highlight the central role of the TLR7/interferon-driven myeloid axis in lupus-like immune pathology.