New insights into chronic rhinosinusitis associated with IgG4-related disease

IgG4-related disease (IgG4-RD) is a chronic inflammatory disorder characterized by elevated IgG4 serum levels, abundant IgG4-positive plasmacyte infiltration, and fibrosis of various organs, including the head and neck. We aimed to provide an overall review of IgG4-RD in the sinonasal region and propose a novel entity and criteria of chronic rhinosinusitis (CRS) associated with IgG4-RD as "IgG4-CRS," a distinct manifestation of IgG4-RD in the sinonasal region. Sinonasal involvement has been increasingly recognized; however, this region is not included in the classic IgG4-RD-affected organs. The clinical features of IgG4-CRS, including its prevalence and relationship with allergies and olfactory disturbances, have also been explored. Serum IgG4 levels and IgG4-positive plasma cell infiltrations, crucial diagnostic factors, have been discussed in association with IgG4-CRS pathogenesis. Fibrosis, a hallmark of IgG4-RD, is observed in sinonasal tissues; however, typical fibrosis, such as storiform fibrosis, is not usually found. Mimics or complications in eosinophilic CRS (ECRS) and antineutrophil cytoplasmic antibody-associated vasculitis (AAV) are highlighted. Treatment often involves typically effective glucocorticoids. Organ-specific diagnostic criteria for the sinonasal region have not currently been established. Hence, this review aims to foster awareness and understanding of IgG4-CRS among ENT physicians and to provide a basis for future research and diagnostic refinement.

Extraction of characteristic serum microRNAs and prediction of target genes in IgG4-related dacryoadenitis and sialadenitis

OBJECTIVES

To identify the specific microRNAs (miRNAs) in IgG4-related dacryoadenitis and sialadenitis (IgG4-DS) and predict the targeted genes.

METHODS

miRNAs in the serum of nine patients with IgG4-DS, three patients with primary Sjögren's syndrome, and three healthy controls were analysed using the human miRNA chip, and miRNAs that exhibited significant fluctuation in expression in IgG4-DS patients were extracted. The respective target genes were predicted using an existing database, and expression of the target genes was evaluated in actual submandibular gland tissues affected by IgG4-DS.

RESULTS

Serum miR-125a-3p and miR-125b-1-3p levels were elevated in IgG4-DS. Six candidate target genes (glypican 4, forkhead box C1, protein tyrosine phosphatase non-receptor type 3, hydroxycarboxylic acid receptor 1, major facilitator superfamily domain containing 11, and tumour-associated calcium signal transducer 2) were downregulated in the affected submandibular gland tissue.

CONCLUSION

Overexpression of miR-125a-3p and miR-125b-1-3p is a hallmark of IgG4-DS. These miRNAs appear to be involved in the pathogenesis of IgG4-DS.

Bob1 maintains T follicular helper cells for long-term humoral immunity

Humoral immunity is vital for host protection, yet aberrant antibody responses can trigger harmful inflammation and immune-related disorders. T follicular helper (Tfh) cells, central to humoral immunity, have garnered significant attention for unraveling immune mechanisms. This study shows the role of B-cell Oct-binding protein 1 (Bob1), a transcriptional coactivator, in Tfh cell regulation. Our investigation, utilizing conditional Bob1-deficient mice, suggests that Bob1 plays a critical role in modulating inducible T-cell costimulator expression and cellular respiration in Tfh cells. This regulation maintains the long-term functionality of Tfh cells, enabling their reactivation from central memory T cells to produce antibodies during recall responses. In a bronchial asthma model induced by house dust mite (HDM) inhalation, Bob1 is observed to enhance HDM-specific antibodies, including IgE, highlighting its pivotal function in Tfh cell regulation. Further exploration of Bob1-dependent mechanisms in Tfh cells holds promise for governing protective immunity and addressing immune-related disorders.

Circulating T follicular helper 2 cells, T follicular regulatory cells and regulatory B cells are effective biomarkers for predicting the response to house dust mite sublingual immunotherapy in patients with allergic respiratory diseases

The relationships between T follicular helper (Tfh) cells and antigen-specific immunoglobulins (sIgs) in patients with allergic respiratory diseases who are receiving antigen immunotherapy (AIT) have not been fully clarified. Therefore, we started to perform house dust mite sublingual immunotherapy (HDM-SLIT) for 20 patients with atopic asthma comorbid with allergic rhinitis (AA+AR) who were already receiving ordinary treatments including inhaled corticosteroid (ICS). We examined percentages of circulating T follicular helper (cTfh) and regulatory (cTfr) cells and percentages of circulating regulatory T (cTreg) and B (cBreg) cells by FACS and we examined levels of Der-p/f sIgs by ELISA. Based on the symptom score (asthma control questionnaire: ACQ) and medication score ((global initiative for asthma: GINA) treatment step score) in patients with AA, the patients were divided into responders and non-responders. The percentage of cTfh2 cells significantly decreased and the percentage of cTfh1 cells significantly increased within the first year. Der-p/f sIgEs decreased after a transient elevation at 3 months in both groups. Notably, the percentage of cTfh2 cells and the ratio of cTfh2/cBreg cells and Der-p/f sIgEs greatly decreased in responders from 6 months to 12 months. The percentages of cTfr and cTreg cells showed significant negative correlations with the percentage of cTfh2 cells. The percentage of IL-4+ cTfh cells were significantly decreased and the percentage of IFN-γ+ cTfh cells were increased before treatment to 24 months in 6 patients examined (4 responders and 2 non-responders). We performed multi plelogistic regression analysis based on these results, the ratios of cTfh2/cTfr cells and cTfh2/cBreg cells at the start of therapy were statistically effective biomarkers for predicting the response to HDM-SLIT in patients with AA+AR.

IgG4-related disease administered dupilumab: case series and review of the literature

Dupilumab (DUP) is a monoclonal antibody that acts on the interleukin (IL)-4 receptor alpha, which inhibits IL-4 and IL-13 signalling and is approved for type 2 inflammatory diseases such as asthma, chronic rhinosinusitis with nasal polyposis and atopic dermatitis; however, the efficacy of DUP to IgG4-related disease (IgG4-RD) is under discussion due to the controversial outcomes based on the several case reports. Here, we reviewed the efficacy of DUP in four consecutive patients with IgG4-RD in our institute and the previous literature.All patients administered DUP fulfilled the 2019 ACR/EULAR classification criteria for IgG4-RD complicated with severe asthma and chronic rhinosinusitis with nasal polyposis. Two cases were administered DUP without systemic glucocorticoids (GCs), and in 6 months, the volume of swollen submandibular glands (SMGs) was reduced by approximately 70%. Two cases receiving GCs successfully reduced their daily dose of GCs (10 and 50% reduction, respectively) with dupilumab in 6 months. In all four cases, serum IgG4 concentration and IgG4-RD responder index decreased in 6 months.DUP reduced the volume of the swollen SMGs, serum IgG4 levels, responder index and the daily dose of GCs in patients with IgG4-RD with severe asthma or eosinophilic rhinosinusitis in 6 months.The efficacy of DUP to IgG4-RD is under discussion due to the limited case reports with controversial outcomes. Here, we demonstrated that two patients with IgG4-RD treated by DUP without systemic GCs, showed volume reduction of swollen SMGs and two cases showed GC-sparing effects by DUP. DUP can ameliorate the disease activity and be a steroid-sparing agent in patients with IgG4-RD.

Functional Interplay between IL-9 and Peptide YY Contributes to Chronic Skin Inflammation

Complex interactions between keratinocytes and various cell types, such as inflammatory cells and stromal cells, contribute to the pathogenesis of chronic inflammatory skin lesions. In proinflammatory cytokine‒mediated disease settings, IL-9 plays a pathological role in inflammatory dermatitis. However, IL-9‒related mechanisms remain incompletely understood. In this study, we established tamoxifen-induced keratinocyte-specific IL-9RA-deficient mice (K14^CRE/ERTIl9ra^Δ/Δ mice) to examine the role of IL-9 in multicellular interactions under chronic skin inflammatory conditions. Studies using an imiquimod-induced psoriasis-like model showed that K14^CRE/ERTIl9ra^Δ/Δ mice exhibited a significantly reduced severity of dermatitis and mast cell infiltration compared with control K14^WTIl9ra^fl/fl mice. Transcriptome analyses of psoriasis-like lesions showed that the level of peptide Y-Y (Pyy), a member of the neuropeptide Y family, was markedly downregulated in K14^CRE/ERTIl9ra^Δ/Δ epidermis. Pyy blockade suppressed epidermal thickening and mast cell numbers in imiquimod-treated wild-type mice. Together with in vitro studies indicating that Pyy induced IL-9 production and chemotactic activity in bone marrow‒derived mast cells, these findings suggest that Pyy-mediated interplay between keratinocytes and mast cells contributes to psoriasiform inflammation. Further investigation focusing on the IL-9‒Pyy axis may provide valuable information for the development of new treatment modalities for inflammatory dermatitis.

CD4+CD8+ T follicular helper cells regulate humoral immunity in chronic inflammatory lesions

T follicular helper (Tfh) cells drive humoral immunity by facilitating B cell responses at the initial and recall phases. Recent studies have indicated the possible involvement of Tfh cells in the process of chronic inflammation. However, the functional role of Tfh cells in persistent immune settings remains unclear. Here, we report that CD4⁺CD8⁺ (double-positive, DP; CD3⁺CD4⁺CD8⁺CXCR5^hiPD-1^hi) Tfh cells, a subset of germinal-center-type Tfh cells, were abundantly present in the fibroinflammatory lesions of patients with immunoglobulin G4-related disease (IgG4-RD). Transcriptome analyses showed that these DP-Tfh cells in the lesions of IgG4-RD preferentially expressed signature genes characteristic of cytotoxic CD8⁺ T cells, such as Eomes, CRTAM, GPR56, and granzymes, in addition to CD70. Scatter diagram analyses to examine the relationships between tissue-resident lymphocytes and various clinical parameters revealed that the levels of DP-Tfh cells were inversely correlated to the levels of serum IgG4 and local IgG4-expressing (IgG4⁺) memory B cells (CD19⁺CD27⁺IgD^-) in patients with IgG4-RD. Cell culture experiments using autologous tonsillar lymphocytes further suggested that DP-Tfh cells possess a poor B-cell helper function and instead regulate memory B cells. Since CD4⁺ (single positive, SP; CD3⁺CD4⁺CD8^-CXCR5^hiPD-1^hi) Tfh cells differentiated into DP-Tfh cells under stimulation with IL-2 and IL-7 as assessed by in vitro experiments, these data imply that SP-Tfh cells are a possible origin of DP-Tfh cells under persistent inflammation. These findings highlight the potential feedback loop mechanism of Tfh cells in immune tolerance under chronic inflammatory conditions. Further studies on DP-Tfh cells may facilitate control of unresolved humoral responses in IgG4-RD pathological inflammation.

Tubarial gland involvement in IgG4-related diseases

BACKGROUND

Tubarial glands (TGs) are a collection of unidentified salivary glands overlying the torus tubarius in the nasopharyngeal wall. Immunoglobulin G4-related disease (IgG4-RD) is a chronic fibroinflammatory state that often has multiple organ involvement. Involvement of the head and neck, especially the salivary glands, is common in IgG4-RD.

AIMS/OBJECTIVES

This study aimed to elucidate the clinical significance of TGs in IgG4-RD.

MATERIALS AND METHODS

We investigated the local findings of TGs in ten patients with IgG4-RD.

RESULTS

Nasopharyngeal endoscopic examination revealed oedematous swelling of the nasopharyngeal wall surrounding the TGs, which improved after steroid treatment. Moreover, sonotubometry showed a stenotic pattern in three out of seven patients with IgG4-RD.

CONCLUSIONS AND SIGNIFICANCE

TGs may be involved in IgG4-RD. The swollen TGs may be responsible for obstructive Eustachian tube dysfunction. Further studies are required to clarify the clinical significance and physiological roles of TGs in IgG4-RD.

The differential diagnosis of IgG4-related disease based on machine learning

INTRODUCTION

To eliminate the disparity and maldistribution of physicians and medical specialty services, the development of diagnostic support for rare diseases using artificial intelligence is being promoted. Immunoglobulin G4 (IgG4)-related disease (IgG4-RD) is a rare disorder often requiring special knowledge and experience to diagnose. In this study, we investigated the possibility of differential diagnosis of IgG4-RD based on basic patient characteristics and blood test findings using machine learning.

METHODS

Six hundred and two patients with IgG4-RD and 204 patients with non-IgG4-RD that needed to be differentiated who visited the participating institutions were included in the study. Ten percent of the subjects were randomly excluded as a validation sample. Among the remaining cases, 80% were used as training samples, and the remaining 20% were used as test samples. Finally, validation was performed on the validation sample. The analysis was performed using a decision tree and a random forest model. Furthermore, a comparison was made between conditions with and without the serum IgG4 concentration. Accuracy was evaluated using the area under the receiver-operating characteristic (AUROC) curve.

RESULTS

In diagnosing IgG4-RD, the AUROC curve values of the decision tree and the random forest method were 0.906 and 0.974, respectively, when serum IgG4 levels were included in the analysis. Excluding serum IgG4 levels, the AUROC curve value of the analysis by the random forest method was 0.925.

CONCLUSION

Based on machine learning in a multicenter collaboration, with or without serum IgG4 data, basic patient characteristics and blood test findings alone were sufficient to differentiate IgG4-RD from non-IgG4-RD.

Abnormal [18F]fluorodeoxyglucose accumulation to tori tubarius in IgG4-related disease

OBJECTIVES

Tubarial glands (TGs) are recently refocused gland tissues localized near the tori tubarius in the nasopharynx and their clinical relevance is not clear yet. IgG4-related disease (IgG4-RD) is a progressive fibrosing condition and salivary glands are well-affected lesions. The aim of the present study is to examine [¹⁸F]fluorodeoxyglucose ([¹⁸F]FDG) accumulation to the tori tubarius in IgG4-related disease (IgG4-RD).

METHODS

48 patients with IgG4-RD who underwent positron emission tomography (PET) scanning with [¹⁸F]FDG were included and semi-quantitative analysis of [¹⁸F]FDG accumulation to tori tubarius was performed along with the clinical features and histopathological analysis.

RESULTS

Of the 48 patients, abnormal [¹⁸F]FDG accumulation (metabolic tumour volume ≥ 1) to tori tubarius was observed in 15 (31.3%), all of whom had lesions in other head and neck glands. IgG4-RD patients with abnormal [¹⁸F]FDG accumulation to tori tubarius showed swollen nasopharyngeal walls around tori tubarius and forceps biopsy of the lesion revealed acinar cells and IgG4-positive plasma cells histologically. Abnormal [¹⁸F]FDG accumulation (maximum standard uptake value, metabolic tumour volume and total lesion glycolysis) to tori tubarius correlated with higher IgG4 and lower IgA serum concentrations.

CONCLUSIONS

Abnormal [¹⁸F]FDG accumulation to tori tubarius can be observed in patients with IgG4-RD and the abnormal [¹⁸F]FDG accumulation to tori tubarius can be a clue of TG involvement in IgG4-RD.

Cigarette Smoke Underlies the Pathogenesis of Palmoplantar Pustulosis via an IL-17A-Induced Production of IL-36γ in Tonsillar Epithelial Cells

Palmoplantar pustulosis (PPP) is characterized by sterile pustules on the palms and soles. A strong association between PPP and tobacco smoking has been reported, and it has been speculated that the IL-17A pathway may play an important role in PPP. Recent studies have suggested that IL-36 plays a pivotal role in the pathogenesis of psoriasis and its subtypes. The relationships among IL-36, smoking, and PPP have not been examined. Here, we investigated the relationships among the smoking index, severity of the clinical condition of PPP, and in vitro dynamics of IL-36 in human tonsillar epithelial cells under the condition of exposure to a cigarette smoke extract. The results demonstrated that the Palmoplantar Pustulosis Area and Severity Index was strongly and positively correlated with the smoking index in female patients. Immunohistochemical examinations showed that IL-36γ was highly expressed in tonsillar epithelial cells from patients with PPP but not in those from patients with recurrent tonsillitis without PPP. The in vitro study revealed that IL-17A synergistically induced a release of IL-36γ under cigarette smoke extract exposure. These results suggest that local production of IL-36γ by epithelial cells induced by cigarette smoke exposure plays an important role in the pathogenesis of PPP.

Cytotoxic Tph-like cells are involved in persistent tissue damage in IgG4-related disease

OBJECTIVES

The aim of this study was to determine pathological features of T peripheral helper (Tph)-like (PD-1⁺CXCR5^-CD4⁺ T) cells in IgG4-related disease (IgG4-RD).

METHODS

Tph-like cells in the blood and submandibular glands (SMGs) from IgG4-RD patients were analyzed by flow cytometry. Correlations between level of a Tph-like cell subset and clinical parameters of IgG4-RD were investigated. The cytotoxic capacity of Tph-like cells was also examined. Expression profiles of a molecule related to a Tph-like cell subset in IgG4-RD SMGs were assessed by immunohistochemistry.

RESULTS

Tph-like cells from IgG4-RD patients highly expressed a fractalkine receptor, CX3CR1. Percentages of circulating CX3CR1⁺ Tph-like cells were significantly correlated with clinical parameters including IgG4-RD Responder Index, number of involved organs, and serum level of soluble IL-2 receptor. CX3CR1⁺ Tph-like cells abundantly possessed cytotoxic T lymphocyte-related molecules such as granzyme A, perforin, and G protein-coupled receptor 56. Functional assays revealed their cytotoxic potential against vascular endothelial cells and ductal epithelial cells. Immunohistochemistry showed that fractalkine was markedly expressed in vascular endothelial cells and ductal epithelial cells in IgG4-RD SMGs.

CONCLUSION

CX3CR1⁺ Tph-like cells are thought to contribute to persistent tissue injury in IgG4-RD and are a potential clinical marker and/or therapeutic target for inhibiting progression of IgG4-RD.

Activated circulating T follicular helper cells and skewing of T follicular helper 2 cells are down-regulated by treatment including an inhaled corticosteroid in patients with allergic asthma

BACKGROUND

CXCR5⁺ T follicular helper (T_FH) cells primarily promote B cells to produce an antigen-specific antibody through germinal centers (GCs). T_FH cells exist in circulation, and circulating(c) T_FH2 cells, a subset of cT_FH cells, are able to help naïve B cells produce IgE in healthy individuals. Conversely, IL-10-producing regulatory B (Breg) cells inhibit an accelerated immune response.

METHODS

We investigated the roles of cT_FH cells and cBreg cells based on a T_H2 response in patients with atopic asthma (AA). Thirty-two patients with AA and 35 healthy volunteers (HV) were enrolled. We examined cT_FH cells including their subsets, their expression of ICOS and PD-1, and cBreg cells by flow cytometry and their associations with clinical biomarkers. Plasma levels of CXCL13, which is a counterpart of CXCR5, were also measured using ELISA.

RESULTS

In patients with AA, cT_FH2 cells were increased and cT_FH1 cells were decreased compared with those in HV. The expression levels of ICOS on cT_FH and their subset cells were elevated and Breg cells were greatly decreased. The plasma levels of CXCL13 in patients with AA were significantly elevated and correlated well with the cT_FH2/cBreg ratio. These cells were examined in 10 patients AA before and after inhaled corticosteroid (ICS) treatment. Interestingly, the percentages and numbers of T_FH2 and ICOS⁺ cT_FH cells declined after ICS treatment together with improvements in symptoms and clinical biomarkers.

CONCLUSIONS

The percentages and numbers of cT_FH2 and ICOS⁺ cT_FH cells might be useful as biomarkers of T_H2 typed airway inflammation in patients with AA.

Aberrant populations of circulating T follicular helper cells and regulatory B cells underlying idiopathic pulmonary fibrosis

Background

T follicular helper (Tfh) cells have been identified as a new category of helper T cells, which express CXCR5 on their surface and induce the production of antigen-specific antibodies. Many investigations have found morbid proliferation and/or activation of Tfh cells in systemic autoimmune and allergic diseases. It is also known that Tfh cells are regulated by regulatory B (Breg) cells in the deteriorating such diseases. Recently, CXCL13, a ligand of CXCR5, has been reported to increase in the peripheral blood and lungs of patients with idiopathic pulmonary fibrosis (IPF). This study aimed to investigate the involvement of Tfh cells and Breg cells in IPF.

Methods

Peripheral blood samples were obtained from 18 patients with IPF. We isolated heparinized peripheral blood mononuclear cells and investigated the proportions of Breg cells, Tfh cells, PD-1⁺ICOS⁺ Tfh cells (activated form of Tfh cells), and the Tfh-cell subsets by flow cytometry. These cell profiles were compared with those of 21 healthy controls. Furthermore, we investigated the correlations between profiles of lymphocytes and lung physiology.

Results

The median proportions of Tfh cells per total CD4⁺ T cells and of PD-1⁺ICOS⁺ proportion of Tfh cells per total Tfh cells was significantly more in the IPF patients (20.4 and 5.2%, respectively) compared with healthy controls (15.4 and 2.1%, respectively; p = 0.042 and p = 0.004, respectively). The proportion of Tfh2 cells per total Tfh cells was significantly higher and the proportion of Tfh17 was smaller in the IPF patients than healthy controls. The percentage of Breg cells to total B cells was significantly decreased in the IPF patients (median, 8.5%) compared with that in the controls (median, 19.7%; p < 0.001). The proportion of Breg cells was positively correlated with the annual relative change in diffusing capacity of the lungs for carbon monoxide in the IPF patients (r = 0.583, p = 0.018).

Conclusion

Proliferation and activation of Tfh cells and a decrease in Breg cells were observed in the peripheral blood of patients with IPF. The profile of the Tfh-cell subset also changed. Specific humoral immunity aberration would likely underlie complicated pathophysiology of IPF.

New insights into IgG4-related disease: emerging new CD4+ T-cell subsets

PURPOSE OF REVIEW

New insights into IgG4-related disease (IgG4-RD) have recently been obtained. A better understanding of the mechanisms underlying this disease is important for identification of therapeutic targets, which will lead to the development of specific strategies for treatment.

RECENT FINDINGS

Infiltration of activated T follicular helper (Tfh) cells is observed in affected tissues of IgG4-RD. Such Tfh cells have a greater capacity than tonsillar Tfh cells to help B cells produce IgG4. Circulating PD-1CXCR5 peripheral T helper (Tph)-like cells are also increased in patients with IgG4-RD. Because Tph-like cells express high levels of chemokine receptors and granzyme A, they have the capacity to infiltrate affected tissues and exert a cytotoxic function. Tph-like cells can also produce CXCL13, and CXCR5 Tfh cells and B cells are therefore preferentially recruited to form ectopic lymphoid structures in the sites. Tph cells may have a role to ignite inflammation and maintain persistent fibroinflammation in collaboration with Tfh cells in lesions of IgG4-RD.

SUMMARY

Recent advances in understanding the pathogenesis of IgG4-RD are remarkable. In this review, we summarize and discuss the possible pathologic role of CD4 T-cell subsets in IgG4-RD.

Interleukin 5-producing ST2+ memory Th2 cells in IgG4-related dacryoadenitis and sialadenitis

Objectives: Immunoglobulin (Ig) G4-related disease (IgG4-RD) is often complicated by allergic disorders. This study was conducted to investigate the mechanism of type 2 helper T-inflammation (Th2-inflammation) in IgG4-related dacryoadenitis and sialadenitis (IgG4-DS). Methods: We separated and analyzed the proportion of growth stimulation expressed gene 2 (ST2)⁺ memory Th2 cells among the peripheral blood mononuclear cells by flow cytometry in cases with IgG4-DS and healthy individuals. Finally, we identified the role of ST2⁺ memory Th2 cells in the involved tissues. Results: The proportion of circulating ST2⁺ memory Th2 cells was much higher in the patients with IgG4-DS than in the healthy controls. Abundant infiltration of ST2⁺ memory Th2 cells was detected in the involved salivary glands and lymph nodes, and these cells produced interleukin-5. Conclusion: We demonstrated that there is an increase of interleukin-5 producing ST2⁺ memory Th2 cells in the involved tissues in IgG4-DS. This subset of cells is considered to be an important player in inducing the inflammatory Th2 environment characteristic of IgG4-DS.

Circulating PD-1+CXCR5-CD4+ T cells underlying the immunological mechanisms of IgG4-related disease

Objective

The aim was to study the pathological role of lymphocytes with a peripheral T helper-cell-like phenotype (PD-1⁺CXCR5⁻CD4⁺) in IgG4-related disease (IgG4-RD).

Methods

PD-1⁺CXCR5⁻CD4⁺ T cells in the blood of patients with IgG4-RD (n = 53), patients with SS (n = 16) and healthy volunteers (n = 34) as controls were analysed by flow cytometry. Correlations between results obtained by flow cytometry and clinical parameters relevant to IgG4-RD were also analysed.

Results

The percentage and absolute number of PD-1⁺CXCR5⁻ cells within total CD4⁺ T cells in IgG4-RD patients were significantly increased compared with those in healthy volunteers. Further analysis showed that there were marked positive correlations of the percentage of PD-1⁺CXCR5⁻CD4⁺ T cells with the serum level of IgG4 and the number of organs involved. Interestingly, granzyme A (GZMA)⁺ cells were enriched in PD-1⁺CXCR5⁻CD4⁺ T cells, and the percentage and absolute number of GZMA⁺PD-1⁺CXCR5⁻CD4⁺ T cells were significantly elevated in IgG4-RD patients. Although no obvious change was observed in the percentage of total CD4⁺ T cells, the percentage and absolute number of PD-1⁺CXCR5⁻CD4⁺ T cells decreased in accordance with a reduction of serum IgG4 level after treatment with glucocorticoids.

Conclusion

In IgG4-RD, circulating CD4⁺ T-cell populations were composed of PD-1⁺CXCR5⁻ cells, and the ratios of these cells were correlated with clinical manifestations of IgG4-RD. Further analysis of GZMA⁺PD-1⁺CXCR5⁻CD4⁺ T cells might lead to a deeper understanding of the pathogenesis of ectopic lymphoid follicles and the persistent inflammation in IgG4-RD.

Stage classification of IgG4-related dacryoadenitis and sialadenitis by the serum cytokine environment

OBJECTIVES

Patients with immunoglobulin-G4 related disease (IgG4-RD) diagnosed according to the comprehensive diagnostic criteria (CDC) show varied therapeutic responses and prognoses. We assumed that there are clinical stages in IgG4-RD and have verified it using serum cytokine levels in the groups classified by lesion distribution.

METHODS

Definite IgG4-related dacryoadenitis and sialadenitis (IgG4-DS) cases were divided according to the CDC for IgG4-RD into 11 cases with focal type and 30 cases with systemic type. The levels of serum interleukin (IL)-4, IL-5, IL-6, IL-10, IL-13, IL-15, IL-21, interferon (IFN)-α, IFN-γ, tumor necrosis factor (TNF)-α, transforming growth factor (TGF)-β1, and monocyte chemotactic protein (MCP)-1 were measured in healthy controls, allergic patients, probable IgG4-RD cases, and focal and systemic type cases. The cytokine environment was analyzed in each group. The 52 definite IgG4-RD cases were next classified into four groups with cluster analysis in terms of therapeutic responses and prognosis. The relationships between each cytokine level and therapeutic responses were also analyzed.

RESULTS

Both serum IL-5 and IFN-α concentrations were very low in healthy controls, but they increased in the allergic cases, probable cases, and focal and systemic type cases. The level of serum IL-5 was significantly higher in definite cases than in healthy controls. The serum IL-5 level was also significantly increased in the groups with a poor prognosis than in the good prognosis group.

CONCLUSION

These results suggest that there are clinical stages in IgG4-RD, and serum IL-5 play roles in the pathogenesis of IgG4-RD.

Loss of sorting nexin 5 stabilizes internalized growth factor receptors to promote thyroid cancer progression

Thyroid carcinoma is the most common endocrine malignancy and its prevalence has recently been increasing worldwide. We previously reported that the level of sorting nexin 5 (Snx5), an endosomal translocator, is preferentially decreased during the progression of well-differentiated thyroid carcinoma into poorly differentiated carcinoma. To address the functional role of Snx5 in the development and progression of thyroid carcinoma, we established Snx5-deficient (Snx5^-/- ) mice. In comparison to wild-type (Snx5^+/+ ) mice, Snx5^-/- mice showed enlarged thyroid glands that consisted of thyrocytes with large irregular-shaped vacuoles. Snx5^-/- thyrocytes exhibited a higher growth potential and higher sensitivity to thyroid-stimulating hormone (TSH). A high content of early endosomes enriched with TSH receptors was found in Snx5^-/- thyrocytes, suggesting that loss of Snx5 caused retention of the TSH receptor (TSHR) in response to TSH. Similar data were found for internalized EGF in primary thyrocytes. The increased TSH sensitivities in Snx5^-/- thyrocytes were also confirmed by results showing that Snx5^-/- mice steadily developed thyroid tumors with high metastatic potential under high TSH. Furthermore, a thyroid cancer model using carcinogen and an anti-thyroidal agent revealed that Snx5^-/- mice developed metastasizing thyroid tumors with activation of MAP kinase and AKT pathways, which are postulated to be major pathways of malignant progression of human thyroid carcinoma. Our results suggest that thyrocytes require Snx5 to lessen tumorigenic signaling driven by TSH, which is a major risk factor for thyroid carcinoma. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Cutting Edge: A Critical Role of Lesional T Follicular Helper Cells in the Pathogenesis of IgG4-Related Disease

IgG4-related disease (IgG4-RD) is a newly recognized systemic chronic fibroinflammatory disease. However, the pathogenesis of IgG4-RD remains unknown. To determine the pathophysiologic features of IgG4-RD, we examined T follicular helper (Tfh) cells in lesions and blood from patients with IgG4-RD. Patients with IgG4-related dacryoadenitis and sialadenitis (IgG4-DS) showed increased infiltration of Tfh cells highly expressing programmed death 1 and ICOS in submandibular glands. Tfh cells from IgG4-DS submandibular glands had higher expression of B cell lymphoma 6 and a greater capacity to help B cells produce IgG4 than did tonsillar Tfh cells. We also found that the percentage of programmed death 1^hi circulating Tfh cells in IgG4-DS patients was higher than that in healthy volunteers and was well correlated with clinical parameters. Our findings indicate that anomalous Tfh cells in tissue lesions of IgG4-RD have features distinct from those in lymphoid counterparts or blood and potentially regulate local IgG4 production in IgG4-RD.

High frequency of Bob1lo T follicular helper cells in florid reactive follicular hyperplasia

Florid reactive follicular hyperplasia (FRFH), which is characterized by large germinal centers (GCs) within normal lymphoid follicles, is often observed in benign lesions of lymph nodes and other tissues. Because of the histologic similarity of FRFH to tumorous lesions such as follicular lymphoma, careful pathological examination is required to evaluate such lesions; however, little is known about the mechanism underlying the development of FRFH. In this study, we investigated T follicular helper (Tfh) cells in hyperplastic tonsils of patients with obstructive sleep apnea syndrome (OSA), which frequently exhibits typical FRFH. When we analyzed tonsils of OSA and recurrent tonsillitis (RT) as a control, tonsils of OSA were found to harbor Tfh cells with a nearly 3-fold higher ratio in total CD4⁺ T cells than that in tonsils of RT. Further analysis showed that, in comparison to Tfh cells of RT tonsils, Tfh cells of OSA tonsils were relatively tolerant to CD3-mediated activation-induced cell death (AICD) and also expressed lower levels of a Bob1 transcription coactivator and IL-4, which fosters the development of GC-B cells. Given that Bob1 controls the proliferative activity in response to CD3 stimulation and has been suggested to have a role in the production of IL-4 in Tfh cells, the unique structure of FRFH is possibly associated with the function of Bob1^lo Tfh cells.

Lipid mediators foster the differentiation of T follicular helper cells

Lipid mediators such as leukotrienes and lipoxines broadly regulate innate and acquired immunity, and their dysfunction causes various immune-mediated disorders. We previously reported a salient feature of arachidonate 5-lipoxyganase (Alox5), which is responsible for the production of such lipid mediators, in the regulation of high affinity antibodies in vivo. The aim of this study was to determine the functional significance of Alox5-related lipid mediators during the processes of acquired humoral responses. The results of in vitro experiments using lymphocytes in tonsils and blood specimens showed that lipoxin A4 (LXA4) and leukotriene B4 (LTB4) have the capacity to differentiate naïve CD4⁺ T cells into T follicular helper (Tfh) cells, which activate naïve B cells to form germinal centers. Such a function of LXA4 was further supported by results of in vitro studies using BML-111 and BOC-2, which are an agonist and an antagonist, respectively, of FPR2 of an LXA4-specific cell-surface receptor. The results suggest that such lipid mediators have a potential role in the development of lymphoid follicles through the regulation of Tfh cell differentiation.

Clarithromycin prevents human respiratory syncytial virus-induced airway epithelial responses by modulating activation of interferon regulatory factor-3

Macrolide antibiotics exert immunomodulatory activity by reducing pro-inflammatory cytokine production by airway epithelial cells, fibroblasts, vascular endothelial cells, and immune cells. However, the underlying mechanism of action remains unclear. Here, we examined the effect of clarithromycin (CAM) on pro-inflammatory cytokine production, including interferons (IFNs), by primary human nasal epithelial cells and lung epithelial cell lines (A549 and BEAS-2B cells) after stimulation by Toll-like receptor (TLR) and RIG-I-like receptor (RLR) agonists and after infection by human respiratory syncytial virus (RSV). CAM treatment led to a significant reduction in poly I:C- and RSV-mediated IL-8, CCL5, IFN-β and -λ production. Furthermore, IFN-β promoter activity (activated by poly I:C and RSV infection) was significantly reduced after treatment with CAM. CAM also inhibited IRF-3 dimerization and subsequent translocation to the nucleus. We conclude that CAM acts a crucial modulator of the innate immune response, particularly IFN production, by modulating IRF-3 dimerization and subsequent translocation to the nucleus of airway epithelial cells. This newly identified immunomodulatory action of CAM will facilitate the discovery of new macrolides with an anti-inflammatory role.

Clinicopathological analysis of salivary gland tissue from patients with IgG4-related disease

Conclusion The diagnosis of immunoglobulin G4-related disease (IgG4-RD) should be based on the morphology of tissue biopsy, and this study recommends a submandibular gland (SMG) biopsy for accurate diagnosis and to exclude malignant disease. Objective To clarify which type of biopsy specimen (SMG or labial salivary gland [LSG]) should be taken from patients with IgG4-RD. Methods This study included 33 patients with IgG4-RD (21 women; 12 men) who were subjected to both SMG and LSG biopsies at Sapporo Medical University between 2011-2015. Tissues obtained from the SMG and LSG specimens were evaluated. Results All SMG specimens satisfied the diagnostic criteria for IgG4-RD, whereas 19 (57.6%) LSG specimens satisfied the diagnostic criteria for IgG4-RD. Histological evaluation showed fibrosis in all the SMG specimens and in eight LSG specimens (24.2%). Obliterative phlebitis was seen in nine SMG specimens (27.3%), but it was absent in all the LSG specimens.

Novel Mechanisms of Compromised Lymphatic Endothelial Cell Homeostasis in Obesity: The Role of Leptin in Lymphatic Endothelial Cell Tube Formation and Proliferation

Leptin is a hormone produced by adipose tissue that regulates various physiological processes. Recent studies have shown that the level of circulating leptin is elevated in obese patients and have suggested a relationship between obesity and postoperative lymphedema. However, the mechanisms by which postoperative lymphedema develops in obese patients and the mechanisms by which leptin regulates lymphatic endothelial cell homeostasis such as tube formation and cell proliferation remain unknown. Here we report that leptin regulates tube formation and cell proliferation in human dermal lymphatic endothelial cells (HDLECs) by activation of the signal transducer and activator of transcription 3 pathway, which is downstream signaling of the leptin receptor. Additionally, we found that upregulation of suppressor of cytokine signaling 3 underlies the mechanisms by which a high dose of leptin inhibits cell proliferation and tube formation. Leptin also enhanced expression of the proinflammatory cytokine IL-6 in HDLECs. Interestingly, IL-6 rescues the compromised cell proliferation and tube formation caused by treatment with a high dose of leptin in an autocrine or paracrine manner. Taken together, our findings reveal a novel mechanism by which compromised HDLECs maintain their homeostasis during inflammation mediated by leptin and IL-6. Thus, regulating the level of leptin or IL-6 may be a viable strategy to reduce the incidence of postoperative lymphedema.

Bob1 limits cellular frequency of T-follicular helper cells

T follicular helper (Tfh) cells are involved in specific humoral immunity at initial and recall phases. The fact that the transcription repressors B‐cell lymphoma‐6 and Blimp‐1 determine lineages of Tfh cells and other types of effector CD4⁺ T cells, respectively, suggests that there are unique mechanisms to establish Tfh‐cell identity. In this study, we found that Tfh cells preferentially express the transcriptional coactivator Bob1. Bob1 of Tfh cells was dispensable for the expression of B‐cell lymphoma‐6 and the functional property of the cells for B cell help. However, upon initial immunization of foreign antigens, the percentages of Tfh cells in Bob1^−/− mice were much higher than those in wild‐type (WT) mice. In addition, expansion of Tfh cells within Bob1^−/−CD4⁺ T cells transferred into WT mice revealed that the high frequency of Tfh cells was caused by a T‐cell‐intrinsic mechanism. These findings were further supported by the results of in vitro studies demonstrating that Bob1^−/− Tfh cells had greater proliferative activity in response to stimuli by CD3/CD28 monoclonal antibody and were also refractory to CD3‐induced cell death in comparison to WT Tfh cells. These results suggest that Tfh cells harbor a Bob1‐related mechanism to restrict numerical frequency against stimulation of TCRs.

Role of Crosstalk between Epithelial and Immune Cells, the Epimmunome, in Allergic Rhinitis Pathogenesis

Recently, the prevalence of allergic rhinitis has been dramatically increasing worldwide. As conventional therapies for allergic rhinitis, such as antihistamines, leukotriene receptor antagonists, nasal sprays and allergen immunotherapy, have limitations, the development of new drugs is required. Recent studies have revealed that epithelial cell-derived cytokines, including thymic stromal lymphopoietin, interleukin (IL)-25 and IL-33, are able to control immune cells, such as dendritic cells and T cells, thereby acting as 'master switches' in allergic disease. In addition, new roles have been identified for follicular helper T cells and regulatory B cells in allergic disease, and they are considered to be promising targets for new therapies. Thus, crosstalk between epithelial and immune cells, the epimmunome, underlies the pathogenesis of allergic rhinitis. Greater understanding of the epimmunome may lead to breakthroughs in the development of new treatments for allergic rhinitis and will help us cure many patients suffering from its severe symptoms in the future.

Studies of Tonsils in Basic and Clinical Perspectives: From the Past to the Future

The tonsils are located at the entrance of the pharynx as a cardinal constituent of Waldeyer's ring, taking part not only in local immune responses, but also in systemic immunity. Functional deficits of tonsils primarily underlie the pathogenesis of various characteristic disorders, including tonsillar focal infections such as palmoplantar pustulosis and IgA nephropathy, in addition to the highly prevalent sleep disorder called obstructive sleep apnea syndrome. Although the mechanisms underlying these disorders remain unknown, the tonsils have long been postulated as a unique and enigmatic immune organ. Lymphoid cells and tissues from surgically resected tonsils are often employed to analyze the human immune response from a retrospective view. This approach has provided much new fundamental evidence for understanding innate and acquired immune responses, thereby facilitating further studies in the fields of mucosal immunity and specific humoral immunity originating in the germinal center. Future studies of the tonsils in basic and clinical research are expected to reveal the mechanisms of tonsil-related disorders as well as the nature of human immunity. In this review, which is primarily based on our original research over the past 3 decades, we summarize our findings and discuss the future prospects of studies focusing on the tonsils.

Expression and Localization of Human Defensins in Palatine Tonsils

Defensins are small antimicrobial peptides and effector components of innate immune responses. Recent studies have shed light on their beneficial functions for the prevention of infection and potential for development of new drugs. Here, we showed the expression profiles of human defensins in palatine tonsils with 3 different diseases: tonsillar hypertrophy, recurrent tonsillitis and focal infection of the tonsil. RT-PCR analysis and immunofluorescence revealed that the expression of human α-defensin 4 and β-defensin 3 (β3) in palatine tonsils with tonsillar hypertrophy was lower than that in recurrent tonsillitis and focal infection of the tonsil, suggesting that chronic inflammation induces defensin expression. Interestingly, β2 and β3 mRNAs were specifically expressed by palatine tonsil tissues but not in human peripheral blood mononuclear cells and mucosa of the small intestine. Additionally, we observed that exposure to a Toll-like receptor 4 ligand, lipopolysaccharide, which is used as a bacterial infection model, increases the production of β2 in culture supernatants from tonsillar epithelial cells in a dose-dependent manner. Taken together, these results indicate that β2 produced by tonsillar epithelial cells plays an important role in the innate immune response for bacterial infections.

Inflammation-induced desmoglein-2 ectodomain shedding compromises the mucosal barrier

Proinflammatory cytokines promote desmoglein-2 (Dsg2) ectodomain shedding in intestinal epithelial cells. Epithelial exposure to Dsg2 ectodomains compromises intercellular adhesion while also promoting proliferation. These findings identify mechanisms by which mucosal inflammation–induced cleavage of Dsg2 influences intestinal epithelial homeostasis.

Desmosomal cadherins mediate intercellular adhesion and control epithelial homeostasis. Recent studies show that proteinases play an important role in the pathobiology of cancer by targeting epithelial intercellular junction proteins such as cadherins. Here we describe the proinflammatory cytokine-induced activation of matrix metalloproteinase 9 and a disintegrin and metalloproteinase domain–containing protein 10, which promote the shedding of desmosomal cadherin desmoglein-2 (Dsg2) ectodomains in intestinal epithelial cells. Epithelial exposure to Dsg2 ectodomains compromises intercellular adhesion by promoting the relocalization of endogenous Dsg2 and E-cadherin from the plasma membrane while also promoting proliferation by activation of human epidermal growth factor receptor 2/3 signaling. Cadherin ectodomains were detected in the inflamed intestinal mucosa of mice with colitis and patients with ulcerative colitis. Taken together, our findings reveal a novel response pathway in which inflammation-induced modification of columnar epithelial cell cadherins decreases intercellular adhesion while enhancing cellular proliferation, which may serve as a compensatory mechanism to promote repair.

Alteration of human blood type 2 follicular helper T cells and regulatory B cells underlies comorbid association of allergic rhinitis with bronchial asthma (HYP2P.338)

Allergic rhinitis (AR) is the most common allergic inflammatory disorder of the airway and its increasing worldwide prevalence has made it a global health problem. AR frequently precedes bronchial asthma (in 10 to 40% of cases), and the presence of AR is considered to be a risk factor for new onset of asthma. However, little is known about the mechanism by which AR advances to a state of AR with bronchial asthma (AR+Asthma). To determine the pathophysiologic features of AR and AR+Asthma, we examined subsets of follicular helper T (Tfh) cells and regulatory B (Breg) cells in peripheral blood from AR and AR+Asthma patients. The results demonstrated polarization of Tfh2 cells within Tfh cell subsets in both AR and AR+Asthma cases. Interestingly, Breg cells were decreased in AR cases and, more extensively, in AR+Asthma cases. Addtionally, we found significant correlations of fractional exhaled nitric oxide and blood eosinophil levels with the index %Tfh2 cells per %Breg cells. Our findings indicate that depletion of Breg cells under the condition of Tfh2 cell skewing is a putative exaggerating factor of AR to bronchial asthma.

Alteration of circulating type 2 follicular helper T cells and regulatory B cells underlies the comorbid association of allergic rhinitis with bronchial asthma

Allergic rhinitis (AR), the most common allergic disorder of the airway, is often accompanied by bronchial asthma. However, little is known about the mechanism by which AR advances to AR comorbid with bronchial asthma (AR+Asthma). To determine the pathophysiologic features of AR and AR+Asthma, we examined subsets of follicular helper T (Tfh) cells and regulatory B (Breg) cells in peripheral blood from AR and AR+Asthma patients. The results showed polarization of Tfh2 cells within Tfh cell subsets in both AR and AR+Asthma cases. Interestingly, the %Breg cells in total B cells were decreased in AR cases and, more extensively, in AR+Asthma cases. Moreover, we found significant correlations of fractional exhaled nitric oxide and blood eosinophil levels with the index %Tfh2 cells per %Breg cells. Our findings indicate that relative decrease in Breg cells under the condition of Tfh2 cell skewing is a putative exaggerating factor of AR to bronchial asthma.

ΔNp63 controls a TLR3-mediated mechanism that abundantly provides thymic stromal lymphopoietin in atopic dermatitis

In the skin lesions of atopic dermatitis (AD), keratinocytes release large quantities of thymic stromal lymphopoietin (TSLP), causing unfavorable inflammation along with skin damage. Nevertheless, how TSLP influences keratinocytes themselves is still unknown. In this study, we showed that ΔNp63, a p53-homologue, predominantly expressed in keratinocytes regulated the receptor complex of TSLP, which determines susceptibility to self-derived TSLP. Expression of TSLP receptors in skin tissues and keratinocytes was assessed by immunohistochemistry and quantitative RT-PCR, and in vitro studies were also performed to examine the functional relevance of ΔNp63 in the expression of TSLP receptors and the constituting autocrine and/or paracrine pathway of TSLP under the condition of stimuli to innate receptors sensing cell damage. The results showed that normal keratinocytes in the upper epidermis preferentially expressed TSLP receptors and conversely lacked ΔNp63, which has an inhibitory effect on the expression of TSLP receptors. Interestingly, the epidermis of AD lesions was found to abundantly contain keratinocytes with low or undetectable levels of ΔNp63 (ΔNp63(lo/-)). Moreover, in the absence of ΔNp63, keratinocytes readily presented TSLP and other cytokines by stimuli through Toll-like receptor 3 (TLR3). Together with the evidence that extrinsic TSLP itself augments TSLP production by keratinocytes without ΔNp63, the results indicate that ΔNp63(lo/-) keratinocytes generate TSLP through a putative autocrine and/or paracrine pathway upon TLR3 stimulation within AD lesions, since moieties of damaged cells and pathogens stimulate TLR3.

IFNγ-induced suppression of β-catenin signaling: evidence for roles of Akt and 14.3.3ζ

Nuclear Akt1 phosphorylates 14.3.3ζ at serine 58 to inhibit β-catenin transactivation. The results outline a dual function of Akt1, which suppresses intestinal epithelial cell proliferation during intestinal inflammation.

The proinflammatory cytokine interferon γ (IFNγ ) influences intestinal epithelial cell (IEC) homeostasis in a biphasic manner by acutely stimulating proliferation that is followed by sustained inhibition of proliferation despite continued mucosal injury. β-Catenin activation has been classically associated with increased IEC proliferation. However, we observed that IFNγ inhibits IEC proliferation despite sustained activation of Akt/β-catenin signaling. Here we show that inhibition of Akt/β-catenin–mediated cell proliferation by IFNγ is associated with the formation of a protein complex containing phosphorylated β-catenin 552 (pβ-cat552) and 14.3.3ζ. Akt1 served as a bimodal switch that promotes or inhibits β-catenin transactivation in response to IFNγ stimulation. IFNγ initially promotes β-catenin transactivation through Akt-dependent C-terminal phosphorylation of β-catenin to promote its association with 14.3.3ζ. Augmented β-catenin transactivation leads to increased Akt1 protein levels, and active Akt1 accumulates in the nucleus, where it phosphorylates 14.3.3ζ to translocate 14.3.3ζ/β-catenin from the nucleus, thereby inhibiting β-catenin transactivation and IEC proliferation. These results outline a dual function of Akt1 that suppresses IEC proliferation during intestinal inflammation.

Cleavage of transmembrane junction proteins and their role in regulating epithelial homeostasis

Epithelial tissues form a selective barrier that separates the external environment from the internal tissue milieu. Single epithelial cells are densely packed and associate via distinct intercellular junctions. Intercellular junction proteins not only control barrier properties of the epithelium but also play an important role in regulating epithelial homeostasis that encompasses cell proliferation, migration, differentiation and regulated shedding. Recent studies have revealed that several proteases target epithelial junction proteins during physiological maturation as well as in pathologic states such as inflammation and cancer. This review discusses mechanisms and biological consequences of transmembrane junction protein cleavage. The influence of junction protein cleavage products on pathogenesis of inflammation and cancer is discussed.

POU2AF1 arranges systemic distribution of follicular helper T cells (IRC10P.466)

Follicular helper T (Tfh) cells are a distinctive subset of CD4+ T helper cells, which play a critical role to establish specific humoral immunity by helping the germinal center formation of B cells. Currently, it is known that Tfh cells are maintained by BCL-6, MAF, and BATF; however, a mechanism managing Tfh cells is not fully clarified yet. To further dissect a regulator of Tfh cells, we employed transcriptome analysis of human tonsillar Tfh cells and thymic naïve T cells as a control. Results demonstrated that, in addition to BCL-6, MAF, and BATF, Tfh cells highly expressed POU2AF1 (BOB.1 or OBF1) at transcript and protein levels. POU2AF1 is a transcriptional coactivator associated with either OCT1 or OCT2 through recognition of POU domains and assists B cells to produce specific antibodies. Analysis using Pou2af1-deficient mice showed that the expression levels of Pou2af1 did not seem to correlate the levels of Cxcr5,Icos,Tigit and Bcl-6 in Tfh cells. Mix cell culture experiments further revealed no functional differences in between Pou2af1-negative Tfh cells and control Tfh cells. But it was of our interest that, after stimulation with foreign antigens, the frequencies of Tfh cells in immune tissues and peripheral blood of Pou2af1-deficient mice were altered in comparison to those of wild-type mice. Taken together, these suggest that POU2AF1/Pou2af1 might have a role to regulate spreading manner of Tfh cells over the body from local sites of immune response.

Galectin-3 regulates desmoglein-2 and intestinal epithelial intercellular adhesion

The desmosomal cadherins, desmogleins, and desmocollins mediate strong intercellular adhesion. Human intestinal epithelial cells express the desmoglein-2 isoform. A proteomic screen for Dsg2-associated proteins in intestinal epithelial cells identified a lectin referred to as galectin-3 (Gal3). Gal3 bound to N-linked β-galactosides in Dsg2 extracellular domain and co-sedimented with caveolin-1 in lipid rafts. Down-regulation of Gal3 protein or incubation with lactose, a galactose-containing disaccharide that competitively inhibits galectin binding to Dsg2, decreased intercellular adhesion in intestinal epithelial cells. In the absence of functional Gal3, Dsg2 protein was internalized from the plasma membrane and degraded in the proteasome. These results report a novel role of Gal3 in stabilizing a desmosomal cadherin and intercellular adhesion in intestinal epithelial cells.