Drug-induced interstitial pneumonia after intravesical Bacillus Calmette-Guerin administration for bladder cancer with scleroderma.

Introduction: Intravesical Bacillus Calmette-Guerin administration is the standard therapy for high-risk nonmuscle invasive bladder cancer and is usually well tolerated. However, some patients experience severe, potentially fatal, complications including interstitial pneumonitis. Case presentation: A 72-year-old female with scleroderma was diagnosed with bladder carcinoma in situ. She developed severe interstitial pneumonitis with the first administration of intravesical Bacillus Calmette-Guerin after the cessation of immunosuppressive agents. Six days after the first administration, she experienced dyspnea at rest, and computed tomography revealed scattered frosted shadows in the upper lung. The following day, she required intubation. We suspected drug-induced interstitial pneumonia and started steroid pulse therapy for 3 days, resulting in a complete response. No exacerbation of scleroderma symptoms or recurrence of cancer was observed 9 months after Bacillus Calmette-Guerin therapy. Conclusion: For patients receiving intravesical Bacillus Calmette-Guerin therapy, close observation of the respiratory condition is necessary for early therapeutic intervention.

Persistence of SARS-CoV-2 neutralizing antibodies and anti-Omicron IgG induced by BNT162b2 mRNA vaccine in patients with autoimmune inflammatory rheumatic disease: an explanatory study in Japan.

Background: Autoimmune inflammatory rheumatic disease (AIRD) patients are at high risk of the coronavirus disease 2019 (COVID-19), but the medium-term effects of immunosuppressants on vaccine efficacy are unknown. We investigated the duration of humoral responses against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) wild-type and Omicron variant in AIRD patients administered with two doses of the BNT162b2 (Pfizer-BioNTech) vaccine. Methods: Serum-neutralizing antibody (NAb) and anti-receptor-binding domain (RBD)/spike antibody levels were measured. Short- and medium-term effects of immunosuppressants were analyzed pre-vaccination (Term 1) and 14-42 days (Term 2) and 100-200 days (Term 3) after the second vaccination. Findings: From Feb 1, 2021, to Feb 28, 2022, 439 AIRD patients and 146 healthy controls were investigated. The seropositivity rate and log10-NAb titers were significantly lower in AIRD patients than in controls at Terms 2 and 3. In rheumatoid arthritis patients, tumor necrosis factor-α inhibitors (TNFis) at Term 3, and older age, glucocorticoids, and abatacept at Terms 2 and 3 were risk factors for reduced responses. Anti-Omicron RBD/spike IgG levels strongly correlated with NAb titers. Interpretation: Glucocorticoids, TNFis, and abatacept treatments negatively affect the longevity of humoral responses to SARS-CoV-2, including Omicron, after two vaccine doses. These findings may inform the timing of additional vaccination for AIRD patients. Funding: Cloud Funding of Peace Winds Japan; Center of Innovation Program from the Ministry of Education, Culture, Sports, Science and Technology of Japan; Japan Society for the Promotion of Science KAKENHI; Japan Agency for Medical Research and Development; Kansai Economic Federation; Mitsubishi Zaidan; and Research Grant from Japan Agency for Medical Research and Development-Core Research for Evolutional Science and Technology.

SLE stratification based on BAFF and IFN-I bioactivity for biologics and implications of BAFF produced by glomeruli in lupus nephritis.

OBJECTIVE: B-cell activating factor (BAFF) is implicated in SLE pathogenesis. Blocking BAFF signalling has contributed to reducing glucocorticoid dosage and preventing organ damage. However, clinical characteristics of patients who may benefit from this therapy are not yet fully elucidated. Therefore, we identified patients with high BAFF-bioactivity to investigate their clinical characteristics and BAFF-producing cells. METHODS: We established the reporter cell for BAFF and investigated the clinical characteristics of SLE patients with high BAFF-bioactivity. We identified BAFF-expressing kidney cells using publicly available scRNA-seq data and immunohistological analysis. SLE patients were stratified based on the bioactivity of BAFF and type-I IFN (IFN-I) to identify associated characteristic clinical manifestations. RESULTS: SLE patients, especially patients with LN, had significantly higher serum BAFF-bioactivity than healthy controls (HC) and non-LN patients. Additionally, single-cell-RNA-seq data and immunohistological analysis of kidney samples from LN patients revealed that BAFF is expressed in glomerular macrophages and mesangial cells. Notably, BAFF bioactivity was elevated in the urine of LN patients compared with that of non-LN patients, while no IFN-I bioactivity was detected in the urine. Furthermore, SLE stratification based on bioactivities of serum BAFF and IFN-I revealed the clinical characteristics of patients: high BAFF represented patients with LN and high IFN-I represented patients with blood and skin manifestations. CONCLUSIONS: Monitoring urinary BAFF-bioactivity may be valuable in diagnosing LN. Furthermore, stratification based on serum BAFF and IFN-I bioactivities may allow the identification of appropriate patients for biologics targeting BAFF and IFN-I.

Proximal heat stress up-regulates angiopoietin-1 in fingers and reduces the severity of Raynaud's phenomenon in systemic sclerosis: a single-centre pilot study.

OBJECTIVES: Raynaud's phenomenon (RP) is a peripheral vascular disorder that frequently occurs in systemic sclerosis (SSc). Although therapeutic heating seems reasonable given that RP is elicited by cold stimuli, the effects of heating are still unclear. We examined the effects of heating applied on various body parts in SSc patients with RP of fingers. METHODS: Fourteen SSc patients heated their neck, elbows, and wrists with disposable heating pads for 1 week each. The visual analogue scale (VAS) for RP during each heating period was compared with that of each 1-week pre-treatment interval. On the day after the expiration of each heating period, their finger temperature, the finger blood flow, and angiogenesis-related factors (vascular endothelial growth factor, endostatin, angiopoietin-1, and angiopoietin-2) obtained from the cubital vein and fingertip were measured. RESULTS: The mean VAS was significantly reduced during the heating of the neck and elbows. Fingertip blood samples showed significantly increased angiopoietin-1 after each of the heating periods and increased endostatin after wrist heating. After the termination of heating, changes in finger temperature or blood flow could not be detected. CONCLUSIONS: Heating the neck or elbows can alleviate RP in SSc. The heat up-regulates angiopoietin-1 in the fingers.

Recovery from prolonged thrombocytopenia in patients with TAFRO syndrome: case series and literature review.

TAFRO syndrome is a newly proposed disease that is characterised by thrombocytopenia, anasarca, fever, reticulin fibrosis (or renal dysfunction), and organomegaly. Generally, high doses of corticosteroids are recommended for the initial treatment of TAFRO syndrome; however, some patients experience prolonged refractory thrombocytopenia after initiating such therapies. If corticosteroid treatment alone is ineffective, additional immunosuppressive therapies such as cyclosporine A are recommended. Since long-term use of immunosuppressive therapies with TAFRO syndrome sometimes causes serious infection, it is important to recognise the time to recovery from thrombocytopenia. In this study, we investigated how long it took to recover from thrombocytopenia, to aid clinicians in decision-making regarding the need to strengthen treatment for prolonged thrombocytopenia. Here, we describe three of our patients with TAFRO syndrome exhibiting prolonged thrombocytopenia. We also investigated the median period to recovery from this complication (defined as the time to increase the platelet count above 50,000/µL) after the initiation of high-dose corticosteroid treatment in our 3 cases and 38 peer-reviewed cases. We found that it took our patients 61 days to recover from thrombocytopenia; in comparison, our investigation of the 38 peer-reviewed case reports revealed a median recovery time of 47.5 days among previously reported patients. We showed the time to recovery from thrombocytopenia in patients with TAFRO syndrome for the first time. Our findings ought to be useful for decision-making among clinicians regarding the administration of other immunosuppressive treatments in addition to corticosteroid.

Tet2 and Tet3 in B cells are required to repress CD86 and prevent autoimmunity.

A contribution of epigenetic modifications to B cell tolerance has been proposed but not directly tested. Here we report that deficiency of ten-eleven translocation (Tet) DNA demethylase family members Tet2 and Tet3 in B cells led to hyperactivation of B and T cells, autoantibody production and lupus-like disease in mice. Mechanistically, in the absence of Tet2 and Tet3, downregulation of CD86, which normally occurs following chronic exposure of self-reactive B cells to self-antigen, did not take place. The importance of dysregulated CD86 expression in Tet2- and Tet3-deficient B cells was further demonstrated by the restriction, albeit not complete, on aberrant T and B cell activation following anti-CD86 blockade. Tet2- and Tet3-deficient B cells had decreased accumulation of histone deacetylase 1 (HDAC1) and HDAC2 at the Cd86 locus. Thus, our findings suggest that Tet2- and Tet3-mediated chromatin modification participates in repression of CD86 on chronically stimulated self-reactive B cells, which contributes, at least in part, to preventing autoimmunity.

Anti-receptor activator of nuclear factor κB ligand antibody treatment increases osteoclastogenesis-promoting IL-8 in patients with rheumatoid arthritis.

The receptor activator of nuclear factor κB ligand (RANKL) is an important factor for osteoclastogenesis and contributes to the pathology of rheumatoid arthritis (RA); thus, the anti-RANKL antibody (Ab) has been expected to protect joint destruction in RA patients. IL-8 also has osteoclastogenic activity; however, the role of IL-8 in the bone pathology of RA as well as the relation between IL-8 and RANKL remain unclear. In the present study, clinical observation revealed serum IL-8 levels of 611 pg ml-1 in RA patients with anti-RANKL Ab and 266 pg ml-1 in the same patients without anti-RANKL Ab. In vitro assay showed that anti-RANKL Ab induced production of IL-8 from pre-osteoclast-like cells (OCLs), and IL-8 promoted the formation of OCLs from peripheral monocytes even without RANKL activity. We further showed that treatment with FK506 (tacrolimus) possibly inhibits the increase in IL-8 levels in RA patients with anti-RANKL Ab, and in vitro assay confirmed that FK506 suppressed IL-8 production in pre-OCLs. These results suggest that inhibition of RANKL induces the change in osteoclastogenesis-promoting factor from RANKL to IL-8, and FK506 may be a valuable combination drug to support the use of anti-RANKL Ab in treatment of RA.

The benefits and prospects of interleukin-6 inhibitor on systemic sclerosis.

Systemic sclerosis (SSc) is a connective tissue disease, the pathogenesis of which is thought to involve interleukin-6 (IL-6), an inflammatory cytokine. This is based on findings of its concentration in patient serum, the results of an IL-6 suppression experiment in an animal model, and the results of a pilot study using IL-6 receptor antibody. However, it appears that a number of factors are involved in the pathology of SSc depending on the state of disease progression. In addition, the degree of involvement of IL-6 differs depending on the difference of organs within particular severe symptoms. Based on the findings from measurements of patient serum, the influence of IL-6 on the pathogenesis of SSc is greater in patients at a relatively early phase of the disease and in patients with lung lesions. Interleukin-13 (IL-13) is one of pro-fibrotic factors, and it is afraid that SSc patients with higher IL-13 have already lost the influence of IL-6. Therefore, although a clinical trial using the anti-IL-6 receptor antibody tocilizumab is underway, it is important to recognize the state of SSc patients prior to selecting treatment.

Semaphorin 4D inhibits neutrophil activation and is involved in the pathogenesis of neutrophil-mediated autoimmune vasculitis.

OBJECTIVES: Inappropriate activation of neutrophils plays a pathological role in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). The aim of this study was to investigate the functions of semaphorin 4D (SEMA4D) in regulation of neutrophil activation, and its involvement in AAV pathogenesis. METHODS: Serum levels of soluble SEMA4D were evaluated by ELISA. Blood cell-surface expression of membrane SEMA4D was evaluated by flow cytometry. To determine the functional interactions between neutrophil membrane SEMA4D and endothelial plexin B2, wild-type and SEMA4D-/- mice neutrophils were cultured with an endothelial cell line (MS1) stained with SYTOX green, and subjected to neutrophil extracellular trap (NET) formation assays. The efficacy of treating human neutrophils with recombinant plexin B2 was assessed by measuring the kinetic oxidative burst and NET formation assays. RESULTS: Serum levels of soluble SEMA4D were elevated in patients with AAV and correlated with disease activity scores. Cell-surface expression of SEMA4D was downregulated in neutrophils from patients with AAV, a consequence of proteolytic cleavage of membrane SEMA4D. Soluble SEMA4D exerted pro-inflammatory effects on endothelial cells. Membranous SEMA4D on neutrophils bound to plexin B2 on endothelial cells, and this interaction decreased NET formation. Recombinant plexin B2 suppressed neutrophil Rac1 activation through SEMA4D's intracellular domain, and inhibited pathogen-induced or ANCA-induced oxidative burst and NET formation. CONCLUSIONS: Neutrophil surface SEMA4D functions as a negative regulator of neutrophil activation. Proteolytic cleavage of SEMA4D as observed in patients with AAV may amplify neutrophil-mediated inflammatory responses. SEMA4D is a promising biomarker and potential therapeutic target for AAV.

Semaphorin 4D Contributes to Rheumatoid Arthritis by Inducing Inflammatory Cytokine Production: Pathogenic and Therapeutic Implications.

OBJECTIVE: Semaphorin 4D (Sema4D)/CD100 has pleiotropic roles in immune activation, angiogenesis, bone metabolism, and neural development. We undertook this study to investigate the role of Sema4D in rheumatoid arthritis (RA). METHODS: Soluble Sema4D (sSema4D) levels in serum and synovial fluid were analyzed by enzyme-linked immunosorbent assay. Cell surface expression and transcripts of Sema4D were analyzed in peripheral blood cells from RA patients, and immunohistochemical staining of Sema4D was performed in RA synovium. Generation of sSema4D was evaluated in an ADAMTS-4-treated monocytic cell line (THP-1 cells). The efficacy of anti-Sema4D antibody was evaluated in mice with collagen-induced arthritis (CIA). RESULTS: Levels of sSema4D were elevated in both serum and synovial fluid from RA patients, and disease activity markers were correlated with serum sSema4D levels. Sema4D-expressing cells also accumulated in RA synovium. Cell surface levels of Sema4D on CD3+ and CD14+ cells from RA patients were reduced, although levels of Sema4D transcripts were unchanged. In addition, ADAMTS-4 cleaved cell surface Sema4D to generate sSema4D in THP-1 cells. Soluble Sema4D induced tumor necrosis factor α (TNFα) and interleukin-6 (IL-6) production from CD14+ monocytes. IL-6 and TNFα induced ADAMTS-4 expression in synovial cells. Treatment with an anti-Sema4D antibody suppressed arthritis and reduced proinflammatory cytokine production in CIA. CONCLUSION: A positive feedback loop involving sSema4D/IL-6 and TNFα/ADAMTS-4 may contribute to the pathogenesis of RA. The inhibition of arthritis by anti-Sema4D antibody suggests that Sema4D represents a potential therapeutic target for RA.

Blockade of interleukin-6 receptor alleviates disease in mouse model of scleroderma.

Activation of fibroblasts by interleukin-6 (IL-6) is implicated in the pathogenesis of scleroderma, suggesting that the inhibition of fibroblast activation may be a promising scleroderma treatment. In this study, we used an IL-6 blocking antibody (Ab) and Il-6 knockout (Il-6KO) mice to examine the role of IL-6 in the bleomycin (BLM)-induced mouse model of scleroderma. BLM was administered to C57BL/6 and Il-6KO mice to induce dermal sclerosis. BLM-treated and control phosphate-buffered saline-treated mice were treated with anti-mouse IL-6 receptor monoclonal Ab (MR16-1). Disease severity was evaluated by measuring dermal thickness and skin hardness, by counting the numbers of α-smooth muscle actin-positive cells and mast cells, and by examining the cutaneous draining lymph nodes. C57BL/6 mice with BLM induced scleroderma had elevated serum IL-6 levels and more severe dermal sclerosis than Il-6KO mice. Weekly administration of MR16-1, but not control Ab, prevented and improved dermal sclerosis, and also attenuated swelling of the draining lymph nodes. MR16-1 suppressed α-smooth muscle actin induction in IL-6-stimulated Il-6KO fibroblasts. Our results indicate that IL-6 contributes to BLM induced dermal sclerosis and that IL-6 receptor-specific monoclonal Ab may improve the symptoms of scleroderma by suppressing fibroblast activation.

Tocilizumab, a humanized anti-interleukin-6 receptor antibody, ameliorated clinical symptoms and MRI findings of a patient with ankylosing spondylitis.

Ankylosing spondylitis (AS) is a chronic inflammatory osteoarticular disease. Although the etiology remains unknown, proinflammatory cytokines, such as tumor necrosis factor α and interleukin-6, have been implicated in the development of AS. Here, we report that a patient with AS, whose disease had been refractory to conventional treatment regimens and who needed to receive continuous corticosteroid, responded well to tocilizumab. While further clinical evaluation is required, tocilizumab may be an optional treatment for AS.

Minimal influence of tocilizumab on IFN-gamma synthesis by tuberculosis antigens.

Interferon gamma (IFN-gamma) production is a critical step of antituberculosis (anti-TB) immune response. The purpose of this study was to determine the influences of biologics, including the interleukin (IL)-6 receptor-inhibitor tocilizumab (TCZ), and tumor necrosis factor (TNF) antagonists infliximab (INF) and etanercept (ETA), on Mycobacterium tuberculosis (MTB) antigen-induced IFN-gamma production. MTB antigen (ESAT-6 and CFP-10)-induced IFN-gamma-releasing assay was performed with or without addition of biologics (TCZ, ETA, and INF) using whole blood from patients with active TB. ETA and INF inhibited IFN-gamma production in a dose-dependent manner. In whole blood from TB patients, ESAT-6 stimulated significant production of IFN-gamma (1.30 +/- 1.95 IU/ml), and TCZ did not inhibit IFN-gamma production (1.56 +/- 1.88 IU/ml). IFN-gamma production by ESAT-6 was inhibited by ETA and INF (0.98 +/- 1.74, 0.75 +/- 1.66 IU/ml, respectively). CFP-10 stimulated significant production of IFN-gamma (1.46 +/- 1.60 IU/ml), and TCZ did not inhibit IFN-gamma production (1.51 +/- 1.77 IU/ml). IFN-gamma production by CFP-10 was inhibited by ETA and INF (0.91 +/- 0.99, 0.72 +/- 0.88 IU/ml, respectively). TCD did not inhibit MTB antigen-induced IFN-gamma production. As IFN-gamma production is important in antimycobacterial host defenses, the minimal influence of TCZ on IFN-gamma-releasing assay suggests a low risk of latent TB infection reactivation during tocilizumab therapy.

Imatinib mesylate inhibited rat adjuvant arthritis and PDGF-dependent growth of synovial fibroblast via interference with the Akt signaling pathway.

Overgrowth of the synovium plays an important role in the pathogenesis of rheumatoid arthritis (RA). Platelet-derived growth factor (PDGF) is one of the most potent mitogenic factors of synovial cells, and imatinib mesylate (imatinib) is a specific inhibitor of the PDGF receptor tyrosine kinase. The aim of this study was to elucidate the anti-rheumatic activity of imatinib. The in vivo effects of imatinib were assessed by evaluating the sequential manifestation of adjuvant-induced arthritis in rats using paw volume and clinical scores. Imatinib was found to inhibit rat adjuvant-induced arthritis, but the inhibitory effects were incomplete. To confirm the mechanism of anti-rheumatic-activity of imatinib, we assessed the in vitro effects of imatinib on the proliferation of RA synovial fibroblast-like cells (RASFs) using a MTT assay. Intracellular signaling of PDGF was evaluated by Western blot analysis. Platelet-derived growth factor was found to induce a significant proliferation of RASFs, while imatinib inhibited PDGF-induced proliferation of RASF. Imatinib also inhibited PDGF-induced phosphorylation of the PDGF receptor and Akt, whereas constitutive activated extracellular signal-regulated kinase was not inhibited by imatinib. In contrast, imatinib did not inhibit transforming growth factor beta- and basic fibroblast growth factor-induced proliferation of RASF. Oral administration of imatinib ameliorated adjuvant-induced arthritis in rats, and it inhibited PDGF-induced RASF proliferation through disruption of the PDGF-R to Akt kinase signaling pathway. Because imatinib cannot inhibit the non-PDGF-dependent proliferation of RASFs, the anti-rheumatic effect of imatinib may be incomplete. The development of inhibitors of RASF proliferation may lead to the successful treatment of RA.

Proteomics-based identification of alpha-enolase as a tumor antigen in non-small lung cancer.

Autoantibodies against tumor antigens represent one type of biomarker that may be assayed in serum for detection of cancer and monitoring of disease progression. In the present study, we used a proteomics-based approach to identify novel tumor antigens in non-small cell lung cancer (NSCLC). By combining two-dimensional electrophoresis, western blotting, mass spectrometry and enzyme-linked immunosorbent assay technology, we detected autoantibodies against alpha-enolase in a subset of NSCLC patients' sera. When 'Mean OD(healthy control sera) + 3 SD(healthy control sera)' was used as the cut-off point, the prevalence of this autoantibody was 27.7% in patients with NSCLC (26 of 94), 1.7% in healthy control subjects (1 of 60), and not detectable in sera from 15 patients with small cell lung cancer, 18 patients with gastrointestinal cancer and nine patients with Mycobacterium avium complex infection of lung. Immunohistochemical staining showed that expression of alpha-enolase was increased in cancer tissues of NSCLC patients, and flow cytometric analysis confirmed the expression of alpha-enolase at the surface of cancer cells. The combined detection of autoantibodies against alpha-enolase, carcinoembryonic antigen and cytokeratin 19 fragment (CYFRA21-1) enhanced sensitivity for the diagnosis of NSCLC. Therefore, autoantibodies against alpha-enolase may constitute a promising biomarker for NSCLC.

Flavonoids and related compounds as anti-allergic substances.

The prevalence of allergic diseases has increased all over the world during the last two decades. Dietary change is considered to be one of the environmental factors that cause this increase and worsen allergic symptoms. If this is the case, an appropriate intake of foods or beverages with anti-allergic activities is expected to prevent the onset of allergic diseases and ameliorate allergic symptoms. Flavonoids, ubiquitously present in vegetables, fruits or teas possess anti-allergic activities. Flavonoids inhibit histamine release, synthesis of IL-4 and IL-13 and CD40 ligand expression by basophils. Analyses of structure-activity relationships of 45 flavones, flavonols and their related compounds showed that luteolin, ayanin, apigenin and fisetin were the strongest inhibitors of IL-4 production with an IC(50) value of 2-5 microM and determined a fundamental structure for the inhibitory activity. The inhibitory activity of flavonoids on IL-4 and CD40 ligand expression was possibly mediated through their inhibitory action on activation of nuclear factors of activated T cells and AP-1. Administration of flavonoids into atopic dermatitis-prone mice showed a preventative and ameliorative effect. Recent epidemiological studies reported that a low incidence of asthma was significantly observed in a population with a high intake of flavonoids. Thus, this evidence will be helpful for the development of low molecular compounds for allergic diseases and it is expected that a dietary menu including an appropriate intake of flavonoids may provide a form of complementary and alternative medicine and a preventative strategy for allergic diseases. Clinical studies to verify these points are now in progress.

Luteolin, a flavonoid, inhibits CD40 ligand expression by activated human basophils.

BACKGROUND: We have previously shown that flavonoids such as luteolin, apigenin and fisetin inhibit interleukin 4 and interleukin 13 production. In this study, we investigated whether luteolin can suppress CD40 ligand expression by basophils. METHODS: A human basophilic cell line, KU812, was stimulated with A23187 and phorbol myristate acetate (PMA) with or without various concentrations of luteolin or other flavonoids for 12 h, and CD40 ligand expression was analyzed by FACS. The effect of luteolin on CD40 ligand mRNA expression was studied by semiquantitative reverse transcription PCR analysis. In addition, CD40 ligand expression was also measured in purified basophils that had been stimulated for 12 h with A23187 plus PMA with or without various concentrations of luteolin. RESULTS: CD40 ligand expression by KU812 cells was enhanced noticeably in response to A23187 and even more strikingly augmented by A23187 plus PMA. The expression was significantly suppressed by 10 or 30 microM of luteolin, whereas myricetin failed to inhibit. Reverse transcription PCR analyses demonstrated that luteolin inhibited CD40 ligand mRNA expression by stimulated KU812 cells. Of the six flavonoids examined, luteolin, apigenin, fisetin and quercetin at 30 microM showed a significant inhibitory effect on CD40 ligand expression. The incubation of purified basophils with A23187 plus PMA significantly enhanced CD40 ligand expression, and the presence of luteolin again had an inhibitory effect. CONCLUSIONS: Luteolin inhibits CD40 ligand expression by activated basophils.

Propionibacterium acnes-induced hepatic granuloma formation is impaired in mice lacking tetraspanin CD9.

The granuloma is a host defence response to persistent pathogenic irritants. In the process of granuloma formation, the activation, migration, and fusion of macrophages occur locally, but the mechanisms involved remain elusive. Tetraspanins regulate cell migration and fusion by organizing functional molecular complexes in membrane microdomains. Here we investigated the role of tetraspanin CD9 in hepatic granuloma formation. Immunostaining of the liver of untreated wild-type mice showed that CD9 was expressed by vascular endothelial cells and perivenular hepatocytes. When intrahepatic granulomas were induced by intravenous injection of Propionibacterium acnes, hepatocyte CD9 was extensively upregulated, while inflammatory cells constituting granulomas were mostly negative for CD9. Compared with wild-type littermates, CD9-knockout mice showed dissemination of Propionibacterium acnes and reduced number and size of granulomas after the injection. Moreover, production of granuloma-inducing cytokines, TNF-alpha and IFN-gamma, was delayed and chemotactic activity for macrophages was suppressed in the liver of mutant mice. These results suggest that CD9 is one of the proteins that promotes granuloma formation in the liver.