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Intestinal microfold cells (M cells) are a dynamic lineage of epithelial cells that initiate mucosal immunity in the intestine. They are responsible for the uptake and transcytosis of microorganisms, pathogens, and other antigens in the gastrointestinal tract. A mature M cell expresses a receptor Gp2 which binds to pathogens and aids in the uptake. Due to the rarity of these cells in the intestine, their development and differentiation remain yet to be fully understood. We recently demonstrated that polycomb repressive complex 2 (PRC2) is an epigenetic regulator of M cell development, and 12 novel transcription factors including Atoh8 were revealed to be regulated by the PRC2. Here, we show that Atoh8 acts as a regulator of M cell differentiation, the absence of Atoh8 led to a significant increase in the number of Gp2+ mature M cells and other M cell-associated markers such as Spi-B and Sox8. In vitro organoid analysis of RankL treated organoid showed an increase of mature marker GP2 expression and other M cell-associated markers. Atoh8 null mice showed an increase in transcytosis capacity of luminal antigens. An increase in M cell population has been previously reported to be detrimental to mucosal immunity because some pathogens like orally acquired prions have been able to exploit the transcytosis capacity of M cells to infect the host, mice with an increased population of M cells are also susceptible to Salmonella infections. Our study here demonstrates that PRC2 regulated Atoh8 is one of the factors that regulate the population density of intestinal M cell in the Peyer’s patch.

Introduction Hip arthroplasty is the standard treatment of a painful hip destruction. The use of modern metal-on-metal (MOM) bearing surfaces gained popularity in total hip arthroplasties during the last decade. Recently, worrisome failures due to adverse reaction to metal debris (ARMD), including pseudotumor response, have been widely reported. However, the pathogenesis of this reaction remains poorly understood. The aim of the present study was to investigate the ARMD response by flow cytometry approach. Methods Sixteen patients with a failed Articular Surface Replacement (ASR) hip prosthesis were included in the study. Samples of pseudotumor tissues collected during revision surgery were degraded by enzyme digestion and cells were typed by flow cytometry. Whole blood chromium and cobalt concentrations were analyzed with mass spectrometry before revision surgery. Results Flow cytometry analysis showed that the peri-implant pseudotumor tissue expressed two principal phenotypes, namely macrophage-dominated and T-lymphocyte-dominated response; the average portions being 54% (macrophages) and 25% (T-lymphocytes) in macrophage-dominated inflammation and 20% (macrophages) and 54% (T-lymphocytes) in T-lymphocyte-dominated response. The percentages of B-lymphocytes and granulocytes were lower in both phenotypes. Interestingly, the levels of blood chromium and cobalt were significantly higher in patients with macrophage-dominated response. Conclusions The results suggest that the adverse tissue reactions induced by MOM wear particles contain heterogeneous pathogeneses and that the metal levels are an important factor in the determination of the inflammatory phenotype. The present results support the hypothesis that higher metal levels cause cytotoxicity and tissue injury and macrophages are recruited to clear the necrotic debris. On the other hand, the adverse response developed in association with lower metal levels is T-lymphocyte-dominated and is likely to reflect hypersensitivity reaction. Public Library of Science open access

The mechanisms leading to latency and reactivation of human tuberculosis are still unclear, mainly due to the lack of standardized animal models for latent mycobacterial infection. In this longitudinal study of the progression of a mycobacterial disease in adult zebrafish, we show that an experimental intraperitoneal infection with a low dose (~35 bacteria) of Mycobacterium marinum, results in the development of a latent disease in most individuals. The infection is characterized by limited mortality (25%), stable bacterial loads 4 weeks following infection and constant numbers of highly organized granulomas in few target organs. The majority of bacteria are dormant during a latent mycobacterial infection in zebrafish, and can be activated by resuscitation promoting factor ex vivo. In 5–10% of tuberculosis cases in humans, the disease is reactivated usually as a consequence of immune suppression. In our model, we are able to show that reactivation can be efficiently induced in infected zebrafish by γ-irradiation that transiently depletes granulo/monocyte and lymphocyte pools, as determined by flow cytometry. This immunosuppression causes reactivation of the dormant mycobacterial population and a rapid outgrowth of bacteria, leading to 88% mortality in four weeks. In this study, the adult zebrafish presents itself as a unique non-mammalian vertebrate model for studying the development of latency, regulation of mycobacterial dormancy, as well as reactivation of latent or subclinical tuberculosis. The possibilities for screening for host and pathogen factors affecting the disease progression, and identifying novel therapeutic agents and vaccine targets make this established model especially attractive. Public Library of Science open access

Sytokiinit ovat liukoisia välittäjäaineita, jotka säätelevät immuunijärjestelmän solujen erilaistumista, kasvua ja toimintaa. Sytokiinin sitoutuminen solukalvolla ilmentyvään reseptoriinsa saa aikaan solun sisäisten signalointireittien aktivaation, ja tämä johtaa lopulta muutoksiin solun biologiassa. Tutkimuksen kohteena on sytokiini interleukiini (IL) ­4:n aktivoiman geenivasteen säätelymekanismit. IL-4 on keskeinen vasta-ainevälitteisen immuniteetin säätelijä, ja sen tiedetään käynnistävän allergisia reaktiota välittävän IgE:n tuotannon B-soluissa. IL-4:n sitoutuminen reseptoriinsa johtaa STAT6-transkriptiotekijän aktivaatioon JAK-tyrosiinikinaasien välityksellä. Aktivoitu STAT6 siirtyy tumaan, jossa se sitoutuu IL-4-responsiivisten geenien (mm. Ige, CD23, MHC II) säätelyalueelle käynnistäen näiden transkription. Tutkimuksen tavoitteena oli selvittää STAT6:n säätelymekanismeja, sekä tutkia STAT6:n toimintaa Ige-geenin promoottoriaktivaatiossa. STAT6:n tyrosiinifosforylaation tiedetään olevan välttämätön IL-4-responsiivisten geenien transkriptiossa. Tutkimuksessa osoitettiin ensimmäistä kertaa IL-4:n aikaansaavan B-soluissa myös STAT6:n seriinifosforylaation lisääntymisen. Seriini/treoniinikinaasiaktivisuuden osoitettiin lisäksi olevan välttämätön IL-4/STAT6-välitteisessä geenivasteessa. Kyetäkseen tehokkaasti aktivoimaan Ige-geenin transkription, ja siten IgE-vasta-ainetuotannon B-soluissa, IL-4 tarvitsee apua CD40-pinta-antigeenin kautta aktivoituvilta signalointimolekyyleiltä. CD40:n aktivoiman p38 MAP -seriini/treoniinikinaasin havaittiin voimistavan IL-4:n geenivasteita lisäämällä suoraan STAT6:n transaktivaatiopotentiaalia. Jatkotutkimuksena pyrittiin identifioimaan uusia STAT6:n kanssa interaktoivia proteiineja. Kofaktori p100:n on aikaisemmin osoitettu säätelevän Epstein-Barrviruksen tuma-antigeeni 2:n (EBNA2) välittämiä geenivasteita. p100:n osoitettiin assosioituvan suoraan STAT6:n transkriptiota aktivoivan osan kanssa lisäten IL-4:n indusoimaa Ige-promoottoriaktivaatiota. STAT6:n sitoutumiskohdan Ige-promoottorilla (Ige -STAT6RE) havaittiin olevan solutyyppispesifisesti säädelty. Ige -STAT6RE:n osoitettiin sisältävän sitoutumissekvenssin hematopoieettisissa soluissa ilmentyvälle PU.1-transkriptiotekijälle. PU.1-proteiinin ilmentäminen transfektion avulla sai aikaan Ige -STAT6RE-välitteisen transkription aktivoitumisen myös ei-hematopoieettisissa soluissa. IL-4:llä tiedetään olevan keskeinen osuus atooppisten tautien patogeneesissä, ja IL-4/STAT6-signalointireitti on siten yksi mahdollisista allergia- ja astmalääkkeiden kohteista. Tutkimus on tuottanut uutta tietoa STAT6:n toiminnasta luoden täten edellytyksiä tulevaisuuden lääkekehitystyölle. Cytokines are a group of small, secreted glycoproteins that have a crucial role in the regulation of cellular events including proliferation and differentiation. Hydrophilic cytokines cannot penetrate through the cell membrane; instead they bind transmembrane receptor molecules that consequently trigger intracellular signaling pathways. Pleiotropic cytokine IL-4 serves as a critical mediator of humoral immune responses executed by B and Th2 type lymphocytes. The engagement of IL-4 receptor on the cell surface leads to the activation of JAK1 and JAK3 tyrosine kinases followed by tyrosine phosphorylation and dimerization of transcription factor STAT6. The activated STAT6 translocates to the nucleus where it binds to specific DNA elements and activates the transcription of IL-4 responsive genes such as IL-4Ra, CD23, MHC class II molecules, and germline Ige. The immediate signaling events that lead to the activation and DNA binding of STAT6 are well established, but relatively little is known about the molecular mechanisms of STAT6-mediated transcription and the regulation of STAT6 activity. The aim of this study was to evaluate the role of serine/threonine kinase activity in STAT6-mediated signaling and the cofactor requirements of STAT6 in Ige promoter activation. It was observed that IL-4 stimulation induced the phosphorylation of STAT6 on both serine and tyrosine residues in B cells, and STAT6-mediated gene activation was dependent on serine/threonine inhibitor H7-sensitive kinase activity. The serine phosphorylation of STAT6 was insensitive to H7 treatment, instead H7 downregulated the IL-4-induced phosphorylation of RNA polymerase II. CD40 antigen engagement provides an important costimulatory signal for IL-4 treatment by activating many intracellular signaling molecules, including p38 MAP kinase. p38 MAP kinase activity was found to enhance the STAT6 transactivation domain (TAD)-driven transcription without an effect on the immediate activation or phosphorylation events of STAT6. The transcriptional coactivat or p100 was identified as a novel STAT6TAD interacting protein. p100 expression did not affect the immediate activation events of STAT6, but it enhanced IL-4-induced germline Ige gene transcription in B cells. The results from interaction studies suggested that p100 functions as a bridging factor between STAT6 and the basal transcription machinery. The STAT6 response element in Ige promoter was observed to be activated in a cell-type specific manner. A minimal low affinity core binding sequence for hematopoietic transcription factor PU.1 was identified within the Ige-STAT6 DNA-binding site. PU.1 restored the IL-4-inducibility of Ige-STAT6 response element in non-hematopoietic cells. The co-operation between PU.1 and STAT6 in the transactivation of the Ige gene represents a molecular mechanism for the fine-tuning of the cell-type restricted expression of IL-4-induced gene responses.