Objective: The decreased stability of atherosclerotic plaques increases the risk of ischemic stroke. However, the specific characteristics of dysregulated immune cells and effective diagnostic biomarkers associated with stability in atherosclerotic plaques are poorly characterized. This research aims to investigate the role of immune cells and explore diagnostic biomarkers in the formation of unstable plaques for the sake of gaining new insights into the underlying molecular mechanisms and providing new perspectives for disease detection and therapy.Method: Using the CIBERSORT method, 22 types of immune cells between stable and unstable carotid atherosclerotic plaques from RNA-sequencing and microarray data in the public GEO database were quantitated. Differentially expressed genes (DEGs) were further calculated and were analyzed for enrichment of GO Biological Process and KEGG pathways. Important cell types and hub genes were screened using machine learning methods including least absolute shrinkage and selection operator (LASSO) regression and random forest. Single-cell RNA sequencing and clinical samples were further used to validate critical cell types and hub genes. Finally, the DGIdb database of gene–drug interaction data was utilized to find possible therapeutic medicines and show how pharmaceuticals, genes, and immune cells interacted.Results: A significant difference in immune cell infiltration was observed between unstable and stable plaques. The proportions of M0, M1, and M2 macrophages were significantly higher and that of CD8⁺ T cells and NK cells were significantly lower in unstable plaques than that in stable plaques. With respect to DEGs, antigen presentation genes (CD74, B2M, and HLA-DRA), inflammation-related genes (MMP9, CTSL, and IFI30), and fatty acid-binding proteins (CD36 and APOE) were elevated in unstable plaques, while the expression of smooth muscle contraction genes (TAGLN, ACAT2, MYH10, and MYH11) was decreased in unstable plaques. M1 macrophages had the highest instability score and contributed to atherosclerotic plaque instability. CD68, PAM, and IGFBP6 genes were identified as the effective diagnostic markers of unstable plaques, which were validated by validation datasets and clinical samples. In addition, insulin, nivolumab, indomethacin, and α-mangostin were predicted to be potential therapeutic agents for unstable plaques.Conclusion: M1 macrophages is an important cause of unstable plaque formation, and CD68, PAM, and IGFBP6 could be used as diagnostic markers to identify unstable plaques effectively.

Th17 CD4⁺ cells promote inflammation and autoimmunity. In this study, we report that Th17 cell frequency is reduced in ob/ob mice (that are genetically deficient in the adipokine leptin) and that the administration of leptin to ob/ob mice restored Th17 cell numbers to values comparable to those found in wild-type animals. Leptin promoted Th17 responses in normal human CD4⁺ T cells and in mice, both in vitro and in vivo, by inducing RORγt transcription. Leptin also increased Th17 responses in (NZB × NZW)F₁ lupus-prone mice, whereas its neutralization in those autoimmune-prone mice inhibited Th17 responses. Because Th17 cells play an important role in the development and maintenance of inflammation and autoimmunity, these findings envision the possibility to modulate abnormal Th17 responses via leptin manipulation, and they reiterate the link between metabolism/nutrition and susceptibility to autoimmunity.

Excessive self-reactive and inadequate affinity-matured antigen-specific antibody responses have been reported to coexist in lupus, with elusive cellular and molecular mechanisms. Here, we report that the antigen-specific germinal center (GC) response―a process critical for antibody affinity maturation―is compromised in murine lupus models. Importantly, this defect can be triggered by excessive autoimmunity-relevant CD11c ⁺ Tbet ⁺ age-associated B cells (ABCs). In B cell-intrinsic Ship-deficient (ShipΔB) lupus mice, excessive CD11c ⁺ Tbet ⁺ ABCs induce deregulated follicular T-helper (T _FH ) cell differentiation through their potent antigen-presenting function and consequently compromise affinity-based GC selection. Excessive CD11c ⁺ Tbet ⁺ ABCs and deregulated T _FH cell are also present in other lupus models and patients. Further, over-activated Toll-like receptor signaling in Ship-deficient B cells is critical for CD11c ⁺ Tbet ⁺ ABC differentiation, and blocking CD11c ⁺ Tbet ⁺ ABC differentiation in ShipΔB mice by ablating MyD88 normalizes T _FH cell differentiation and rescues antigen-specific GC responses, as well as prevents autoantibody production. Our study suggests that excessive CD11c ⁺ Tbet ⁺ ABCs not only contribute significantly to autoantibody production but also compromise antigen-specific GC B-cell responses and antibody-affinity maturation, providing a cellular link between the coexisting autoantibodies and inadequate affinity-matured antigen-specific antibodies in lupus models and a potential target for treating lupus.