Epidermal loss of Bcl6 exacerbates MC903-induced atopic dermatitis-like skin inflammation.

Atopic dermatitis (AD) is a chronic inflammatory skin disease where Th2-type immune responses are dominant. In the lesional skin of AD, keratinocytes show differentiation defects and secrete proinflammatory cytokines and chemokines, amplifying Th2-type responses in AD. We previously reported that inducible loss of B-cell lymphoma 6 (Bcl6), a transcription repressor and a master transcriptional regulator of follicular helper T cells and germinal center B cells, in the whole body results in upregulation of Th2-related cytokines in mouse skin. However, the role of Bcl6 in keratinocytes remains to be clarified. Here, we observed that BCL6 positively regulates the expression of keratinocyte differentiation markers and plasma membrane localization of adherence junctional proteins in keratinocyte cell culture. Although keratinocyte-specific loss of Bcl6 alone did not induce AD-like skin inflammation, it aggravates MC903-induced AD-like skin inflammation in mice. In addition, Bcl6 expression is decreased in the epidermis of lesional skin from MC903-induced AD-like skin inflammation in mice. These results strongly suggest that Bcl6 downregulation in keratinocytes contributes to the development and aggravation of AD-like skin inflammation in mice.

Bcl6 is a subset-defining transcription factor of lymphoid tissue inducer-like ILC3.

Innate lymphoid cells (ILCs) are tissue-resident effector cells with roles in tissue homeostasis, protective immunity, and inflammatory disease. Group 3 ILCs (ILC3s) are classically defined by the master transcription factor RORγt. However, ILC3 can be further subdivided into subsets that share type 3 effector modules that exhibit significant ontological, transcriptional, phenotypic, and functional heterogeneity. Notably lymphoid tissue inducer (LTi)-like ILC3s mediate effector functions not typically associated with other RORγt-expressing lymphocytes, suggesting that additional transcription factors contribute to dictate ILC3 subset phenotypes. Here, we identify Bcl6 as a subset-defining transcription factor of LTi-like ILC3s in mice and humans. Deletion of Bcl6 results in dysregulation of the LTi-like ILC3 transcriptional program and markedly enhances expression of interleukin-17A (IL-17A) and IL-17F in LTi-like ILC3s in a manner in part dependent upon the commensal microbiota-and associated with worsened inflammation in a model of colitis. Together, these findings redefine our understanding of ILC3 subset biology.

High SLC20A1 Expression Indicates Poor Prognosis in Prostate Cancer.

BACKGROUND/AIM: High expression of solute carrier family 20 member 1 (SLC20A1) indicates poor clinical outcomes for patients with breast cancer subtypes treated with endocrine therapy and radiotherapy. However, the association between SLC20A1 expression and clinical outcomes in prostate cancer remains to be determined. MATERIALS AND METHODS: Open-source datasets (The Cancer Genome Atlas prostate, Stand Up to Cancer-Prostate Cancer Foundation Dream Team, and The Cancer Genome Atlas PanCancer Atlas) were downloaded and analyzed. SLC20A1 expression was analyzed in prostate cancer and normal prostate tissue. Survival analysis using Kaplan-Meier curves and Cox regression analysis were performed to examine patient prognosis, as well as the effects of endocrine therapy and radiotherapy on high SLC20A1 expression in patients with prostate cancer. RESULTS: SLC20A1 was higher in prostate cancer than in normal prostate tissues. High SLC20A1 expression predicted poor disease-free and progression-free survival. Following endocrine therapy, no significant difference in prognosis was observed between patients with high SLC20A1 and those with low SLC20A1 expression. However, following radiotherapy, high SLC20A1 expression tended to be associated with a poor clinical outcome. CONCLUSION: SLC20A1 may serve as a prognostic biomarker for prostate cancer, and the recommended treatment for patients with high SLC20A1 expression is endocrine therapy.

Foxp3 and Bcl6 deficiency synergistically induces spontaneous development of atopic dermatitis-like skin disease.

Atopic dermatitis (AD) is a common chronic skin disease caused by immune dysfunction, specifically the hyperactivation of Th2 immunity. AD is a complex disease with multiple factors contributing to its development; however, the interaction between these factors is not fully understood. In this study, we demonstrated that the conditional deletion of both the forkhead box p3 (Foxp3) and B-cell lymphoma 6 (Bcl6) genes induced the spontaneous development of AD-like skin inflammation with hyperactivation of type 2 immunity, skin barrier dysfunction, and pruritus, which were not induced by the single deletion of each gene. Furthermore, the development of AD-like skin inflammation was largely dependent on IL-4/13 signaling but not on immunoglobulin E (IgE). Interestingly, we found that the loss of Bcl6 alone increased the expression of thymic stromal lymphopoietin (TSLP) and interleukin (IL)-33 in the skin, suggesting that Bcl6 controls Th2 responses by suppressing TSLP and IL-33 expression in epithelial cells. Our results suggest that Foxp3 and Bcl6 cooperatively suppress the pathogenesis of AD. Furthermore, these results revealed an unexpected role of Bcl6 in suppressing Th2 responses in the skin.

High expression of PKCλ and ALDH1A3 indicates a poor prognosis, and PKCλ is required for the asymmetric cell division of ALDH1A3-positive cancer stem cells in PDAC.

Pancreatic ductal adenocarcinoma (PDAC) is the cancer with the poorest prognosis. One of the major properties reflecting its poor prognosis is high-grade heterogeneity, which leads to insensitivity to anticancer treatments. Cancer stem cells (CSCs) acquire phenotypic heterogeneity, generating abnormally differentiated cells by asymmetric cell division. However, the detailed mechanism leading to phenotypic heterogeneity is largely unknown. Here, we showed that PDAC patients with co-upregulation of PKCλ and ALDH1A3 had the poorest clinical outcome. PKCλ knockdown by DsiRNA in the ALDH1high population of PDAC MIA-PaCa-2 cells attenuated the asymmetric distribution of the ALDH1A3 protein. To monitor asymmetric cell division of ALDH1A3-positive PDAC CSCs, we established stable Panc-1 PDAC clones expressing ALDH1A3-turboGFP (Panc-1-ALDH1A3-turboGFP cells). In addition to MIA-PaCa-2-ALDH1high cells, turboGFPhigh cells sorted from Panc-1-ALDH1A3-turboGFP cells showed asymmetric cell propagation of ALDH1A3 protein. PKCλ DsiRNA in Panc-1-ALDH1A3-turboGFP cells also attenuated the asymmetric distribution of ALDH1A3 protein. These results suggest that PKCλ regulates the asymmetric cell division of ALDH1A3-positive PDAC CSCs. Furthermore, Panc-1-ALDH1A3-turboGFP cells can be useful for the visualization and monitoring of CSC properties such as asymmetric cell division of ALDH1A3-positive PDAC CSCs in time-lapse imaging.

Spatiotemporal resolution of germinal center Tfh cell differentiation and divergence from central memory CD4+ T cell fate.

Follicular helper T (Tfh) cells are essential for germinal center (GC) B cell responses. However, it is not clear which PD-1+CXCR5+Bcl6+CD4+ T cells will differentiate into PD-1hiCXCR5hiBcl6hi GC-Tfh cells and how GC-Tfh cell differentiation is regulated. Here, we report that the sustained Tigit expression in PD-1+CXCR5+CD4+ T cells marks the precursor Tfh (pre-Tfh) to GC-Tfh transition, whereas Tigit-PD-1+CXCR5+CD4+ T cells upregulate IL-7Rα to become CXCR5+CD4+ T memory cells with or without CCR7. We demonstrate that pre-Tfh cells undergo substantial further differentiation at the transcriptome and chromatin accessibility levels to become GC-Tfh cells. The transcription factor c-Maf appears critical in governing the pre-Tfh to GC-Tfh transition, and we identify Plekho1 as a stage-specific downstream factor regulating the GC-Tfh competitive fitness. In summary, our work identifies an important marker and regulatory mechanism of PD-1+CXCR5+CD4+ T cells during their developmental choice between memory T cell fate and GC-Tfh cell differentiation.

Dysfunction of Foxp3+ Regulatory T Cells Induces Dysbiosis of Gut Microbiota via Aberrant Binding of Immunoglobulins to Microbes in the Intestinal Lumen.

Foxp3+ regulatory T (Treg) cells prevent excessive immune responses against dietary antigens and commensal bacteria in the intestine. Moreover, Treg cells contribute to the establishment of a symbiotic relationship between the host and gut microbes, partly through immunoglobulin A. However, the mechanism by which Treg cell dysfunction disturbs the balanced intestinal microbiota remains unclear. In this study, we used Foxp3 conditional knockout mice to conditionally ablate the Foxp3 gene in adult mice and examine the relationship between Treg cells and intestinal bacterial communities. Deletion of Foxp3 reduced the relative abundance of Clostridia, suggesting that Treg cells have a role in maintaining Treg-inducing microbes. Additionally, the knockout increased the levels of fecal immunoglobulins and immunoglobulin-coated bacteria. This increase was due to immunoglobulin leakage into the gut lumen as a result of loss of mucosal integrity, which is dependent on the gut microbiota. Our findings suggest that Treg cell dysfunction leads to gut dysbiosis via aberrant antibody binding to the intestinal microbes.

High Expression of CD58 and ALDH1A3 Predicts a Poor Prognosis in Basal-like Breast Cancer.

BACKGROUND/AIM: CD58 is an immune adhesion molecule on the cellular surface. It was previously found that a high expression of CD58 predicted a poor prognosis of patients with lower-grade gliomas. Therefore, the aim of this paper was to investigate the association between CD58 and breast cancer. MATERIALS AND METHODS: CD58 gene expression data downloaded from cBioPortal was compared between the different subtypes of breast cancer. Clinical prognosis was examined using Kaplan-Meier analysis and multivariable Cox regression analysis. The association between CD58 expression and immune cell infiltration was estimated using the TIMER 2.0 web platform. Finally, the tumour sphere formation of aldehyde dehydrogenase 1 (ALDH1)high basal-like breast cancer stem cells in which CD58 was knocked down using siRNA was measured. RESULTS: CD58 mRNA was mainly enriched in claudin-low and basal-like subtypes. The high expression of CD58 predicted a good prognosis in patients with luminal A and luminal B breast cancer. This prediction may be due to the association of immune cell infiltration with CD58. Notably, patients with luminal A breast cancer with a high expression of CD58 in association with ALDH1A3 exhibited a good prognosis; however, this did not apply to patients with basal-like breast cancer. The in vitro experiments revealed that knockdown of CD58 inhibited the tumour sphere formation ability of ALDH1high basal-like cancer cells. CONCLUSION: CD58 may function as a potential prognostic biomarker and therapeutic target in ALDH-positive basal-like cancer stem cells.

High Expression of p62 and ALDH1A3 Is Associated With Poor Prognosis in Luminal B Breast Cancer.

BACKGROUND/AIM: p62 (also known as sequestosome 1) is involved in cancer progression, and high expression of p62 indicates poor clinical outcome in several cancer types. However, the association between p62 gene expression and cancer stem cells (CSCs) in breast cancer subtypes remains unclear. MATERIALS AND METHODS: In the present study, genomic datasets of primary breast cancer (The Cancer Genome Atlas, n=593; and Molecular Taxonomy of Breast Cancer International Consortium, n=2,509) were downloaded. p62 Expression was then examined in normal and breast cancer tissues derived from the same patients. Kaplan-Meier and multivariate Cox regression analyses were employed to evaluate disease-specific survival. Next, the effect on cell viability and in vitro tumor-sphere formation of p62 knockdown using targeted small interfering RNA was assessed by using cells with high activity of aldehyde dehydrogenase 1 (ALDH1high). RESULTS: Patients with normal-like, luminal A or luminal B breast cancer with p62high had poor prognosis. Furthermore, patients with p62high ALDH1A3high luminal B type also exhibited poor prognoses. Knockdown of p62 suppressed viability and tumor-sphere formation by ALDH1high cells of the luminal B-type cell lines BT-474 and MDA-MB-361. These results suggest that p62 is essential for cancerous progression of ALDH1-positive luminal B breast CSCs, and contributes to poor prognosis of luminal B breast cancer. CONCLUSION: p62 is potentially a prognostic marker and therapeutic target for ALDH1-positive luminal B breast CSCs.

Gasdermin D-mediated release of IL-33 from senescent hepatic stellate cells promotes obesity-associated hepatocellular carcinoma.

Long-term senescent cells exhibit a secretome termed the senescence-associated secretory phenotype (SASP). Although the mechanisms of SASP factor induction have been intensively studied, the release mechanism and how SASP factors influence tumorigenesis in the biological context remain unclear. In this study, using a mouse model of obesity-induced hepatocellular carcinoma (HCC), we identified the release mechanism of SASP factors, which include interleukin-1ß (IL-1ß)- and IL-1ß-dependent IL-33, from senescent hepatic stellate cells (HSCs) via gasdermin D (GSDMD) amino-terminal-mediated pore. We found that IL-33 was highly induced in senescent HSCs in an IL-1ß-dependent manner in the tumor microenvironment. The release of both IL-33 and IL-1ß was triggered by lipoteichoic acid (LTA), a cell wall component of gut microbiota that was transferred and accumulated in the liver tissue of high-fat diet-fed mice, and the release of these factors was mediated through cell membrane pores formed by the GSDMD amino terminus, which was cleaved by LTA-induced caspase-11. We demonstrated that IL-33 release from HSCs promoted HCC development via the activation of ST2-positive Treg cells in the liver tumor microenvironment. The accumulation of GSDMD amino terminus was also detected in HSCs from human NASH-associated HCC patients, suggesting that similar mechanism could be involved in a certain type of human HCC. These results uncover a release mechanism for SASP factors from sensitized senescent HSCs in the tumor microenvironment, thereby facilitating obesity-associated HCC progression. Furthermore, our findings highlight the therapeutic potential of inhibitors of GSDMD-mediated pore formation for HCC treatment.

GLO 1 and PKCλ Regulate ALDH1-positive Breast Cancer Stem Cell Survival.

BACKGROUND/AIM: We examined the inhibitory effects of both glyoxalase 1 (GLO 1) and protein kinase C (PKC)λ in aldehyde dehydrogenase 1 (ALDH1)-positive breast cancer stem cells (CSCs). MATERIALS AND METHODS: Breast cancer genomics datasets (TCGA, n=593; METABRIC, n=1904) were downloaded and statistically analyzed. The effects of GLO 1 and PKCλ on trypan blue staining and tumor-sphere formation by ALDH1high cells derived from triple negative breast cancer (TNBC) and basal-like breast cancer were examined. RESULTS: GLO 1high, PKCλhigh, and ALDH1A3high tumors were enriched in stage I/II/III/IV samples, associated with the HER2 and TNBC subtypes according to receptor status, and associated with the HER2-enriched and basal-like subtypes according to PAM50. Inhibition of either GLO 1 (TLSC702) or PKCλ (ANF) suppressed tumor-sphere formation and enhanced death in ALDH1high cells. TLSC702 also effectively inhibited tumor-sphere formation and induced death in PKCλ knockout ALDH1high cells. CONCLUSION: GLO 1 and PKCλ are important for the survival of ALDH1-positive breast CSCs, and may represent potential therapeutic targets for the treatment of ALDH1-positive breast CSCs.

High SLC20A1 Expression Is Associated With Poor Prognoses in Claudin-low and Basal-like Breast Cancers.

BACKGROUND/AIM: SLC20A1 has been identified as a prognostic marker in ER+ breast cancer. However, the role of SLC20A1 expression in breast cancer subtypes other than the ER+ types remains unclear. MATERIALS AND METHODS: Genomics datasets were downloaded and analyzed, and the effect of SLC20A1 knockdown using targeted siRNA on cell viability and tumor-sphere formation was assessed. RESULTS: SLC20A1high patients with ER+, claudin-low or basal-like breast cancers showed poor prognoses. SLC20A1high patients treated with radiotherapy had poor clinical outcomes. SLC20A1 knockdown suppressed the viability of MDA-MB 231 (claudin-low), MDA-MB 468 (basal-like) and MCF-7 (ER+) cells, and tumor-sphere formation by ALDH1high cells. These results suggest that SLC20A1 is involved in cancer progression and contributes to clinical outcomes in patients with ER+, claudin-low and basal-like breast cancers. CONCLUSION: SLC20A1 is a potential prognostic marker and therapeutic target in ER+, claudin-low and basal-like breast cancers.

High PKCλ expression is required for ALDH1-positive cancer stem cell function and indicates a poor clinical outcome in late-stage breast cancer patients.

Despite development of markers for identification of cancer stem cells, the mechanism underlying the survival and division of cancer stem cells in breast cancer remains unclear. Here we report that PKCλ expression was enriched in basal-like breast cancer, among breast cancer subtypes, and was correlated with ALDH1A3 expression (p = 0.016, χ2-test). Late stage breast cancer patients expressing PKCλhigh and ALDH1A3high had poorer disease-specific survival than those expressing PKCλlow and ALDH1A3low (p = 0.018, log rank test for Kaplan-Meier survival curves: hazard ratio 2.58, 95% CI 1.24-5.37, p = 0.011, multivariate Cox regression analysis). Functional inhibition of PKCλ through siRNA-mediated knockdown or CRISPR-Cas9-mediated knockout in ALDH1high MDA-MB 157 and MDA-MB 468 basal-like breast cancer cells led to increases in the numbers of trypan blue-positive and active-caspase 3-positive cells, as well as suppression of tumor-sphere formation and cell migration. Furthermore, the amount of CASP3 and PARP mRNA and the level of cleaved caspase-3 protein were enhanced in PKCλ-deficient ALDH1high cells. An Apoptosis inhibitor (z-VAD-FMK) suppressed the enhancement of cell death as well as the levels of cleaved caspase-3 protein in PKCλ deficient ALDH1high cells. It also altered the asymmetric/symmetric distribution ratio of ALDH1A3 protein. In addition, PKCλ knockdown led to increases in cellular ROS levels in ALDH1high cells. These results suggest that PKCλ is essential for cancer cell survival and migration, tumorigenesis, the asymmetric distribution of ALDH1A3 protein among cancer cells, and the maintenance of low ROS levels in ALDH1-positive breast cancer stem cells. This makes it a key contributor to the poorer prognosis seen in late-stage breast cancer patients.

Microbiota-derived butyrate limits the autoimmune response by promoting the differentiation of follicular regulatory T cells.

BACKGROUND: Rheumatoid arthritis (RA) is a chronic debilitating autoimmune disorder with a high prevalence, especially in industrialized countries. Dysbiosis of the intestinal microbiota has been observed in RA patients. For instance, new-onset untreated RA (NORA) is associated with the underrepresentation of the Clostridium cluster XIVa, including Lachnospiraceae, which are major butyrate producers, although the pathological relevance has remained obscure. Follicular regulatory T (TFR) cells play critical regulatory roles in the pathogenesis of autoimmune diseases, including RA. Reduced number of circulating TFR cells has been associated with the elevation of autoantibodies and disease severity in RA. However, the contribution of commensal microbe-derived butyrate in controlling TFR cell differentiation remains unknown. METHODS: We examined the contribution of microbe-derived butyrate in controlling autoimmune arthritis using collagen-induced arthritis (CIA) and SKG arthritis models. We phenotyped autoimmune responses in the gut-associated lymphoid tissues (GALT) in the colon and joint-draining lymph nodes in the CIA model. We developed an in vitro CXCR5+Bcl-6+Foxp3+ TFR (iTFR) cell culture system and examined whether butyrate promotes the differentiation of iTFR cells. FINDINGS: Microbe-derived butyrate suppressed the development of autoimmune arthritis. The immunization of type II collagen (CII) caused hypertrophy of the GALT in the colon by amplifying the GC reaction prior to the onset of the CIA. Butyrate mitigated these pathological events by promoting TFR cell differentiation. Butyrate directly induced the differentiation of functional TFR cells in vitro by enhancing histone acetylation in TFR cell marker genes. This effect was attributed to histone deacetylase (HDAC) inhibition by butyrate, leading to histone hyperacetylation in the promoter region of the TFR-cell marker genes. The adoptive transfer of the butyrate-treated iTFR cells reduced CII-specific autoantibody production and thus ameliorated the symptoms of arthritis. INTERPRETATION: Accordingly, microbiota-derived butyrate serves as an environmental cue to enhance TFR cells, which suppress autoantibody production in the systemic lymphoid tissue, eventually ameliorating RA. Our findings provide mechanistic insights into the link between the gut environment and RA risk. FUNDING: This work was supported by AMED-Crest (16gm1010004h0101, 17gm1010004h0102, 18gm1010004h0103, and 19gm1010004s0104 to KH), the Japan Society for the Promotion of Science (JP17KT0055, JP16H01369, and JP18H04680 to KH; JP17K15734 to DT), Keio University Special Grant-in-Aid for Innovative Collaborative Research Projects (KH), Keio Gijuku Fukuzawa Memorial Fund for the Advancement of Education and Research (DT), the SECOM Science and Technology Foundation (KH), the Cell Science Research Foundation (KH), the Mochida Memorial Foundation for Medical and Pharmaceutical Research (DT), the Suzuken Memorial Foundation (KH and DT), the Takeda Science Foundation (KH and DT), The Science Research Promotion Fund, and The Promotion and Mutual Aid Corporation for Private Schools of Japan (KH).

Spontaneous antibody production caused by regulatory T cell deficiency occurs through a germinal center-independent pathway.

Foxp3+ regulatory T cells (Tregs) are essential for the prevention of autoantibody and allergen-specific IgE production. Treg deficiency causes an elevation of the serum levels of these pathogenic antibodies, accompanied by spontaneous germinal center (GC) formation. However, it remains to be determined whether excessive and pathogenic antibody production induced by Treg deficiency requires a GC response. Here, we demonstrate that spontaneous antibody production observed in Foxp3 conditional-knockout mice did not need GC formation. Foxp3 and Bcl6 conditional-double knockout mice exhibited spontaneous elevations of IgG1, IgG2c, and IgE levels even though they showed impaired production of IgG1 and IgE specific for the immunized antigen. Furthermore, the IgG1 and IgE antibodies specific for auto- and food-antigens were produced independently of GCs. These data suggested that a GC response was unnecessary for pathogenic antibody production caused by Treg deficiency.

High Expression of c-Met, PKCλ and ALDH1A3 Predicts a Poor Prognosis in Late-stage Breast Cancer.

BACKGROUND/AIM: Co-expression of c-Met and ALDH1A3 indicates a poor prognosis in stage III-IV breast cancers and contributes to cell proliferation and tumor formation by ALDH1-positive breast CSCs. PKCλ is overexpressed and contributes to a poor prognosis in several cancers. MATERIALS AND METHODS: A breast cancer genomics data set (METABRIC, n=2509) was downloaded and analyzed, as was the effect c-Met and PKCλ inhibitors on ALDH1high cell viability and tumor-sphere formation. RESULTS: c-Met expression correlates with expression of PKCλ in breast cancer. Stage III-IV breast cancer patients with c-Methigh PKCλhigh ALDH1A3high have a poorer prognosis than patients with c-Metlow PKCλlow ALDH1A3low Foretinib and auranofin suppressed cell viability and tumor-sphere formation by ALDH1high cells. These results suggest that c-Met and PKCλ are cooperatively involved in cancer progression and contribute to poor prognoses in breast cancer. CONCLUSION: c-Met and PKCλ are potentially useful prognostic markers and therapeutic targets in late-stage breast cancer.

Dysregulation of humoral immunity in Foxp3 conditional-knockout mice.

Foxp3+ regulatory T cells (Tregs) are crucial for maintaining tolerance to self-antigens and preventing autoimmune diseases. Loss of Foxp3 expression leads to autoimmunity and disrupts humoral immune responses, including hyperproduction of immunoglobulin E (IgE). Elucidation of how Tregs control antibody production can lead to the development of new therapies for autoimmune and allergic diseases. However, premature death of Foxp3-deficient mice makes it difficult to analyze the roles of Tregs in humoral immunity of adult mice. In this study, we developed Foxp3 conditional-knockout mice (Foxp3floxR26CreERT2) in which the Foxp3 gene was inducibly deleted by tamoxifen administration. After oral administration of tamoxifen, titers of immunoglobulins, particularly IgG2c and IgE, were increased in Foxp3floxR26CreERT2 mice compared with that in controls. Under these conditions, CD4+ T cells from Foxp3floxR26CreERT2 mice had increased expression of several activation markers, including inducible costimulator and CD40 ligand, as well as the cytokines interleukin 4 and interferon gamma. In addition, the proportions of T follicular helper (Tfh) cells and germinal center (GC) B cells were increased in Foxp3floxR26CreERT2 mice compared with those in controls. These results indicated that Tregs controlled excessive or pathogenic antibody production by suppressing Tfh cell differentiation and GC formation. Furthermore, these data suggested that Foxp3floxR26CreERT2 mice could be a useful tool for screening therapeutic agents.

A novel mouse model for tracking the fate of CXCR5-expressing T cells.

The germinal center (GC) reaction, a critical process in the humoral immune response, requires follicular helper T (Tfh) cells. Tfh cells express the master transcription factor Bcl6 and chemokine receptor CXCR5, which enable them to migrate from the T cell zone to B cell follicles and interact with GC B cells. However, CXCR5 is downregulated when Tfh cells become memory cells. Therefore, it is difficult to track Tfh cells continuously in vivo. In this study, we generated a mouse strain, Cxcr5CreERT2R26Tomato, in which the fluorescent protein tdTomato is inducibly expressed in CXCR5+ cells by tamoxifen administration. After the oral administration of tamoxifen, most Tfh cells in Peyer's patches (PP) from Cxcr5CreERT2R26Tomato mice were tdTomato+. To track antigen-specific Tfh cells in vivo, OVA-specific OT-II T cells derived from Cxcr5CreERT2R26Tomato mice were transferred to wild-type mice, and the recipient mice were immunized with OVA followed by tamoxifen administration. CXCR5+ T cells became tdTomato+ and were mainly located in B cell follicles and GC areas 8 days after immunization. Four weeks after immunization, tdTomato+ OT-II T cells migrated from B cell follicles to the T-B border area and T cell zone after CXCR5 downregulation and CCR7 upregulation. These results indicate that Cxcr5CreERT2R26Tomato mice are a useful tool for studying the cell fate of differentiated Tfh cells in vivo and therefore have implications for the development of therapeutic strategies for infectious and autoimmune diseases.

Quantitative analysis by surface plasmon resonance of CD28 interaction with cytoplasmic adaptor molecules Grb2, Gads and p85 PI3K.

CD28 surface receptors provide co-stimulatory signals that are required for full T cell activation. The CD28 cytoplasmic region has one YMNM and two PXXP motifs as a functional motif. Upon CD28 ligation, Grb2, Gads, and the p85 subunit of PI3 kinase are recruited to the CD28 cytoplasmic region. Here, the interactions between these adaptor proteins and CD28 cytoplasmic domains were analyzed using a Biacore surface plasmon resonance biosensor. For all three adaptor proteins, entire molecules bound more tightly to CD28 than did their isolated SH2 domains. For each adaptor, different outcomes of mutation of CD28's PXXP motifs on binding affinity indicated that only the SH3 domain of Grb2 bound directly. Regarding binding of SH2s to CD28, the SH2 domains of p85 bound more strongly than those of both Grb2 and Gads. Since intact p85 had a 50-fold higher binding affinity than its fragments, and yet the p85-CD28 interaction does not involve SH3-PXXP binding, binding of both N-terminal and C-terminal SH2s to YMNM may create an "avidity" effect. In contrast, when Grb2 and Gads interact with CD28, binding of their SH3 domains may be important. These results suggest that all these interactions are multivalent, through both SH2 and SH3 domains.

The 3' enhancer CNS2 is a critical regulator of interleukin-4-mediated humoral immunity in follicular helper T cells.

A main role for interleukin-4 (IL-4) is in humoral immunity, and follicular helper CD4(+) T (Tfh) cells may be an intrinsic IL-4 source. Here we demonstrate that conserved noncoding sequence 2 (CNS2) is an essential enhancer element for IL-4 expression in Tfh cells but not in Th2 cells. Mice with a CNS2 deletion had a reduction in IgG1 and IgE production and in IL-4 expression in Tfh cells. Tracking of CNS2 activity via a GFP reporter mouse demonstrated that CNS2-active cells expressed several markers of Tfh cells: CXCR5, PD-1, and ICOS; the transcriptional master regulator Bcl6; and the cytokines IL-21 and IL-4. These CNS2-active cells were mainly localized in B cell follicles and germinal centers. The GFP(+) Tfh cells were derived from GFP(-) naive T cells after in vivo systemic immunization. These results indicate that CNS2 is an essential enhancer element required for IL-4 expression in Tfh cells controlling humoral immunity.