Shigefumi Matsuzawa, Aya Ushio, Kunihiro Otsuka, Ruka Nagao, Takaaki Tsunematsu, Masafumi Moriyama and Naozumi Ishimaru : Neonatal Thymic Dynamics Influence Autoimmune Pathology by Shaping the Suppressive Potential of Regulatory T Cells, The American Journal of Pathology, 196, 4, 920-933, 2026.
(Summary)
Neonatal thymectomy (TX) has been known to induce experimental autoimmune disease models in mice for over half a century. The thymic microenvironment, including thymic epithelial cells (TECs), plays a crucial role in establishing self-tolerance in T cells. However, the extent to which the dynamic changes in the neonatal thymic environment contribute to the onset of autoimmunity remains incompletely understood. In this study, the detailed alterations in the neonatal thymus and peripheral lymphoid organs were analyzed using a mouse model of primary Sjögren disease. Mice treated with TX at 3 days after birth (day 3-TX) exhibited significantly more severe autoimmune pathology than those treated with TX at 7 days after birth. Around day 3, T-cell differentiation and the expansion of TECs, particularly medullary TECs, were markedly accelerated in the neonatal thymus. Furthermore, in day 3-TX mice, the expansion of peripherally induced regulatory T (Treg) cells was impaired, along with the loss of thymic-derived Treg cell output that typically undergoes robust expansion around day 3 after birth. The suppressive activity of Treg cells from day 3-TX mice was significantly impaired compared with that of control Treg cells. These findings suggest that the neonatal thymic environment plays a critical role in regulating peripheral immune tolerance and may influence the pathogenesis of autoimmune diseases.
Mari Nishida, Kunihiro Otsuka, Ruka Nagao, Shigefumi Matsuzawa, Aya Ushio, Takaaki Tsunematsu, Keiko Aota and Naozumi Ishimaru : Tissue-Specific Expansion of Age-Associated B Cells via IFN-γ and IL-21 Within Salivary Glands in Sjögren Disease., Journal of Immunology Research, 2026, 1, 2026.
(Summary)
Sjögren disease (SjD) is an autoimmune disorder that predominantly affects the exocrine glands, and advancing age is recognized as an important risk factor for its development. However, the mechanisms linking age and disease progression remain poorly understood. Age-associated B cells (ABCs), a subset of B cells that increase with age, have been implicated in autoimmune responses, but their role in SjD pathogenesis has not been fully clarified. In this study, we examined labial salivary glands (LSGs) from 44 SjD patients and 11 non-SjD sicca controls. T-bet+ CD20+ ABCs were detected infiltrating the glands in SjD patients, especially in individuals in their 40s-60s, but were rare in non-SjD sicca controls. To investigate the underlying mechanisms, we used a SjD mouse model at various ages. ABCs (CD11b+ CD95+ CD19+) began locally accumulating in the SGs from the mature-adult stage, earlier than in age-matched controls, while remaining low in cervical lymph nodes (cLNs). To explore the drivers of ABC expansion, we examined the factors involved in ABC differentiation, focusing on interleukin-21 (IL-21) and interferon-gamma (IFN-γ). This combination of IL-21 and IFN-γ upregulated T-bet expression on B cells in SjD model mice. In situ hybridization (ISH) and flow cytometric analysis revealed that CD4+ T cells, especially follicular helper T (Tfh)-like cells were a major source of IL-21 in the SGs of mature-adult-SjD mice. Additionally, ABCs themselves showed elevated expression of IFN-γ compared to other immune cells, indicating an autocrine mechanism promoting their expansion. Our findings suggest that ABCs accumulate in the SGs of SjD patients and model mice through IL-21 signaling from CD4+ T cells and autocrine IFN-γ activity. This localized expansion may contribute to autoimmune tissue damage. These results provide new insights into how aging-associated immune changes may drive the development and progression of SjD, offering potential targets for therapeutic intervention.
Ruka Nagao, Kunihiro Otsuka, Shigefumi Matsuzawa, Aya Ushio, Takaaki Tsunematsu and Naozumi Ishimaru : Differential chemokine profiles between lacrimal and salivary glands in a murine model of primary Sjögren disease, Cytokine, 195, 157023, 2025.
(Summary)
Primary Sjögren disease (pSjD) is an autoimmune disorder that primarily targets the lacrimal glands (LGs) and salivary glands (SGs). However, the differences in immune pathogenesis between LGs and SGs remain poorly understood. In this study, we investigated LG-specific immune responses in comparison to SGs using a murine model of pSjD. Histopathological analyses of LGs and SGs were conducted in control and pSjD model mice. The mRNA expression levels of 18 chemokines associated with T-cell migration were evaluated by quantitative PCR. Gene expression of selected chemokines was further examined in LG tissues by in situ hybridization. The phenotype and function of T-cells were assessed using flow cytometry and in vitro migration assays. Lymphocytic infiltration was observed earlier in LGs than in SGs in pSjD model mice. Among the chemokines analyzed, C-X-C motif chemokine ligand 4 (CXCL4) was specifically upregulated in LGs. Cxcl4 expression was localized to macrophages within LG tissues. Moreover, CXCR3 expression on CD4+ T-cells in lymphoid tissues was significantly higher in pSjD model mice compared to controls. T-bet was more highly expressed in CXCR3+CD4+ T cells than in CXCR3-CD4+ T cells in pSjD model mice. Finally, CXCL4 enhanced the migration of CD4+ T cells derived from pSjD model mice more effectively than those from control mice. These findings suggest that CXCL4-producing macrophages may promote the recruitment of CXCR3+ Th1 cells into the LGs in pSjD, thereby contributing to LG-specific autoimmune inflammation. This mechanism may represent a potential therapeutic target for managing dry eye in pSjD.
Kunihiro Otsuka, Aya Ushio, Ruka Nagao, Shigefumi Matsuzawa, Rieko Arakaki, Kazuki Fukuta, Yasuhiro Mouri, Takaaki Tsunematsu and Naozumi Ishimaru : Regulatory Role of FGL-1 in Interorgan Communication by Controlling T Cell Homeostasis During the Onset of Sjögren Disease., Arthritis & Rheumatology, 77, 11, 1573-1584, 2025.
(Summary)
Autoimmunity occurs due to the tactics between pathogenic and regulatory factors in systemic organs. Although interorgan communication has been demonstrated in various diseases, the effects of the crosstalk between the immune system and other organs on autoimmune disease is unknown.We analyzed the influence of interorgan communication on the cellular or molecular mechanism of autoimmunity using a mouse model of primary Sjögren disease (pSjD) and patients with pSjD by integrative genomic, bioinformatic, pathologic, and immunologic analyses.Fibrinogen-like protein-1 (FGL-1) was identified as a potent factor for interorgan communication between the liver and immune system in pSjD model mice. The production of FGL-1 of the liver is induced by interleukin-6 (IL-6) from CD4+ T cells in these mice. The onset of autoimmune lesions in an Fgl1-deficient pSjD model mice was earlier than that in the wild type pSjD model mice. FGL-1 produced in the liver regulates naïve and memory T cell homeostasis. Further, FGL-1 was significantly up-regulated in patients with pSjD compared to the controls. Moreover, its concentration was closely related to the serum IL-6 levels in patients with pSjD.FGL-1 plays a key role in the onset of autoimmunity by suppressing T cell activation in pSjD. Our results will facilitate the development of novel diagnostic or therapeutic strategies targeting the interorgan communication for autoimmune diseases.
Hiroaki Tawara, Takaaki Tsunematsu, Ruka Nagao, Shigefumi Matsuzawa, Kunihiro Otsuka, Aya Ushio and Naozumi Ishimaru : The noncanonical function of borealin, a component of chromosome passenger complex, promotes glycolysis via stabilization of survivin in squamous cell carcinoma cells., Biochemical and Biophysical Research Communications, 706, 149741, 2024.
(Summary)
The chromosome passenger complex (CPC) is a kinase complex formed by Aurora B, borealin, survivin and inner centromere protein (INCENP). The CPC is active during mitosis and contributes to proper chromosome segregation via the phosphorylation of various substrates. Overexpression of each CPC component has been reported in most cancers. However, its significance remains unclear, as only survivin is known to confer chemoresistance. This study showed that the overexpression of borealin, a CPC component, stabilized survivin protein depending on its interaction with survivin. Unexpectedly, the accumulation of survivin by borealin overexpression did not affect the well-characterized functions of survivin, such as chemoresistance and cell proliferation. Interestingly, the overexpression of borealin promoted lactate production but not the overexpression of the deletion mutant that lacks the ability to bind to survivin. Consistent with these findings, the expression levels of glycolysis-related genes were enhanced in borealin-overexpressing cancer cells. Meanwhile, the overexpression of survivin alone did not promote lactate production. Overall, the accumulation of the borealin-survivin complex promoted glycolysis in squamous cell carcinoma cells. This mechanism may contribute to cancer progression via excessive lactate production.
Mami Sato-Fukuba, Rieko Arakaki, Aya Ushio, Kunihiro Otsuka, Ruka Nagao, Shigefumi Matsuzawa, Hiroaki Tawara, Takaaki Tsunematsu and Naozumi Ishimaru : CD4 T-cell-dependent differentiation of CD23 follicular B cells contributes to the pulmonary pathology in a primary Sjögren's syndrome mouse model., Frontiers in Immunology, 14, 1217492, 2023.
(Summary)
Primary Sjögren's syndrome (pSS) is a systemic autoimmune disease that affects the function of exocrine glands, such as the lacrimal and the salivary glands. Extraglandular lesions and malignant lymphoma also occur during the progressive stage of pSS. We have, herein, focused on the pulmonary lesions of pSS and have aimed clarifying their pathophysiological mechanism by comparing the glandular with the extraglandular lesions observed in a mouse model of pSS. The histopathological analysis of lung tissues obtained from NFS/ mice that have undergone neonatal thymectomy was performed. Moreover, and experiments were conducted along with immunological analyses in order to characterize the unique phenotypes of the pulmonary lesions identified in these pSS model mice. Inflammatory lesions with a bronchus-associated lymphoid tissue-like structure were identified in the lungs of pSS model mice. In addition, relative to salivary gland lesions, pulmonary lesions showed increased CD23 follicular B (FB) cells. and pulmonary B cells were more readily driven to CD23 FB cell phenotype than salivary gland B cells in pSS model mice. Furthermore, the CD23 FB cell differentiation was found to be enhanced in a CD4 T-cell-dependent manner under a Th2-type condition in the lungs of herein examined pSS model mice. A Th2-type response in the pSS lung may promote the progression of autoimmune lesions through an enhanced abnormal differentiation of B cells.