IL-25 promotes the function of CD4+CD25+ T regulatory cells and prolongs skin-graft survival in murine models

Depletion of donor dendritic cells ameliorates immunogenicity of both skin and hind limb transplants

Acute cellular rejection remains a significant obstacle affecting successful outcomes of organ transplantation including vascularized composite tissue allografts (VCA). Donor antigen presenting cells (APCs), particularly dendritic cells (DCs), orchestrate early alloimmune responses by activating recipient effector T cells. Employing a targeted approach, we investigated the impact of donor-derived conventional DCs (cDCs) and APCs on the immunogenicity of skin and skin-containing VCA grafts, using mouse models of skin and hind limb transplantation. By post-transplantation day 6, skin grafts demonstrated severe rejections, characterized by predominance of recipient CD4 T cells. In contrast, hind limb grafts showed moderate rejection, primarily infiltrated by CD8 T cells. Notably, the skin component exhibited heightened immunogenicity when compared to the entire VCA, evidenced by increased frequencies of pan (CD11b-CD11c+), mature (CD11b-CD11c+MHCII+) and active (CD11b-CD11c+CD40+) DCs and cDC2 subset (CD11b+CD11c+ MHCII+) in the lymphoid tissues and the blood of skin transplant recipients. While donor depletion of cDC and APC reduced frequencies, maturation and activation of DCs in all analyzed tissues of skin transplant recipients, reduction in DC activities was only observed in the spleen of hind limb recipients. Donor cDC and APC depletion did not impact all lymphocyte compartments but significantly affected CD8 T cells and activated CD4 T in lymph nodes of skin recipients. Moreover, both donor APC and cDC depletion attenuated the Th17 immune response, evident by significantly reduced Th17 (CD4+IL-17+) cells in the spleen of skin recipients and reduced levels of IL-17E and lymphotoxin-α in the serum samples of both skin and hind limb recipients. In conclusion, our findings underscore the highly immunogenic nature of skin component in VCA. The depletion of donor APCs and cDCs mitigates the immunogenicity of skin grafts while exerting minimal impact on VCA.

Epithelial cell-derived cytokine TSLP activates regulatory T cells by enhancing fatty acid uptake

Epithelial cells control a variety of immune cells by secreting cytokines to maintain tissue homeostasis on mucosal surfaces. Regulatory T (Treg) cells are essential for immune homeostasis and for preventing tissue inflammation; however, the precise molecular mechanisms by which epithelial cell-derived cytokines function on Treg cells in the epithelial tissues are not well understood. Here, we show that peripheral Treg cells preferentially respond to thymic stromal lymphoprotein (TSLP). Although TSLP does not affect thymic Treg differentiation, TSLP receptor-deficient induced Treg cells derived from naïve CD4⁺ T cells are less activated in an adoptive transfer model of colitis. Mechanistically, TSLP activates induced Treg cells partially through mTORC1 activation and fatty acid uptake. Thus, TSLP modulates the activation status of induced Treg through the enhanced uptake of fatty acids to maintain homeostasis in the large intestine.

The Protective Effect of the Soluble Egg Antigen of Schistosoma japonicum in A Mouse Skin Transplantation Model

Background

Organ transplantation is currently an effective method for treating organ failure. Long-term use of immunosuppressive drugs has huge side effects, which severely restricts the long-term survival of patients. Schistosoma can affect the host’s immune system by synthesizing, secreting, or excreting a variety of immunomodulatory molecules, but its role in transplantation was not well defined. In order to explore whether Schistosoma-related products can suppress rejection and induce long-term survival of the transplant, we used soluble egg antigen (SEA) of Schistosoma japonicum in mouse skin transplantation models.

Materials and methods

Each mouse was intraperitoneally injected with 100 μg of SEA three times a week for four consecutive weeks before allogenic skin transplant. Skin transplants were performed on day 0 to observe graft survival. Pathological examination of skin grafts was conducted 7 days post transplantation. The skin grafts were subjected to mRNA sequencing. Bioinformatics analysis was conducted and the expression of hub genes was verified by qPCR. Flow cytometry analysis was performed to evaluate the immune status and validate the results from bioinformatic analysis.

Results

The mean survival time (MST) of mouse skin grafts in the SEA-treated group was 11.67 ± 0.69 days, while that of the control group was 8.00 ± 0.36 days. Pathological analysis showed that Sj SEA treatment led to reduced inflammatory infiltration within skin grafts 7 days after allogenic skin transplantation. Bioinformatics analysis identified 86 DEGs between the Sj SEA treatment group and the control group, including 39 upregulated genes and 47 downregulated genes. Further analysis revealed that Sj SEA mediated regulation on cellular response to interferon-γ, activation of IL-17 signaling and chemokine signaling pathways, as well as cytokine–cytokine receptor interaction. Flow cytometry analysis showed that SEA treatment led to higher percentages of CD4⁺IL-4⁺ T cells and CD4⁺Foxp3⁺ T cells and decreased CD4⁺IFN-γ⁺ T cells in skin transplantation.

Conclusion

Sj SEA treatment suppressed rejection and prolonged skin graft survival by regulating immune responses. Sj SEA treatment might be a potential new therapeutic strategy to facilitate anti-rejection therapy and even to induce tolerance.

Treg regulation of the epithelial stem cell lineage

Tissue repair and maintenance in adult organisms is dependent on the interactions between stem cells (SCs) and constituent cells of their microenvironment, or niche. Accumulating evidence suggests that immune cells, specifically Foxp3⁺ CD4⁺ Regulatory T cells (Tregs), play an important role as a regulator of the SC niche. Undisputedly, Tregs are the major immunosuppressive lineage of the CD4⁺ T cell compartment, and reside within numerous secondary lymphoid organs, where they exert their functions. These cells are also specialised in facilitating protective functions specific to their tissue of residence. In this review, we discuss the emerging concepts supporting the SC-regulatory functions of tissue-resident Tregs, during both the steady-state and SC-mediated regeneration. We highlight the skin, intestines, and lung as model organs which are subject to recurrent microinjury,exposure to microbiota, and constantly replenished by resident stem cell populations. An in-depth understanding of the biology of the Treg-SC axis will inform ongoing immunotherapeutic endeavours to target specific subpopulations of tissue-resident Tregs.

Immunity and Vaccine Development Against Helicobacter pylori

Helicobacter pylori is a highly-adapted gastrointestinal pathogen of humans and the immunology of this chronic infection is extremely complex. Despite the availability of antibiotic therapy, the global incidence of H. pylori infection remains high, particularly in low to middle-income nations. Failure of therapy and the spread of antibiotic resistance among the bacteria are significant problems and provide impetus for the development of new therapies and vaccines to treat or prevent gastric ulcer, and gastric carcinoma. The expansion of knowledge on gastric conventional and regulatory T cell responses, and the role of T_H17 in chronic gastritis from studies in mouse models and patients have provided valuable insights into how gastritis is initiated and maintained. The development of human challenge models for testing candidate vaccines has meant a unique opportunity to study acute infection, but the field of vaccine development has not progressed as rapidly as anticipated. One clear lesson learned from previous studies is that we need a better understanding of the immune suppressive mechanisms in vivo to be able to design vaccine strategies. There is still an urgent need to identify practical surrogate markers of protection that could be deployed in future field vaccine trials. Important developments in our understanding of the chronic inflammatory response, progress and problems arising from human studies, and an outlook for the future of clinical vaccine trials will be discussed.

Targeted Migration of Human Adipose-Derived Stem Cells to Secondary Lymphoid Organs Enhances Their Immunomodulatory Effect and Prolongs the Survival of Allografted Vascularized Composites

The targeted delivery of therapeutic agents to secondary lymphoid organs (SLOs), which are the niches for immune initiation, provides an unprecedented opportunity for immune intolerance induction. The alloimmune rejection postvascularized composite allotransplantation (VCA) is mediated by T lymphocytes. Human adipose-derived stem cells (hASCs) possess the superiority of convenient availability and potent immunoregulatory property, but their therapeutic results in the VCA are unambiguous thus far. Chemokine receptor 7 (CCR7) can specifically guide immune cells migrating into SLOs. There, the genes of CCR7-GFP or GFP alone were introduced into hASCs by lentivirus. hASCs/CCR7 maintained the multidifferentiation and immunoregulatory abilities, but it gained the migration capacity elicited by secondary lymphoid organ chemokine (SCL) (CCR7 ligand) in vitro. Noteworthily, intravenously infused hASCs/CCR7 targetedly relocated in the T-cell aggression area in SLOs. In a rat VCA model, hASCs/GFP transfusion had a rare effect on the allografted vascularized composite. However, hASCs/CCR7 infusion potently prolonged the grafts' survival time. The ameliorated pathologic exhibition and the regulated inflammatory cytokines in the peripheral blood were also observed. The altered axis of Th1/Th2 and Tregs/Th17 in SLOs may underlie the downregulated rejection response. Moreover, the proteomic examination of splenic T lymphocytes also confirmed that hASCs/CCR7 decreased the proteins related to cytokinesis, lymphocyte proliferation, differentiation, and apoptotic process. In conclusion, our present study demonstrated that targeted migration of hASCs/CCR7 to SLOs highly intensifies their in vivo immunomodulatory effect in the VCA model for the first time. We believe this SLO-targeting strategy may improve the clinical therapeutic efficacy of hASC for allogeneic and autogenic immune disease. Stem Cells 2019;37:1581-1594.

Increased β-cell proliferation before immune cell invasion prevents progression of type 1 diabetes

Type 1 diabetes (T1D) is characterized by pancreatic islet infiltration by autoreactive immune cells and a near-total loss of β-cells¹. Restoration of insulin-producing β-cells coupled with immunomodulation to suppress the autoimmune attack has emerged as a potential approach to counter T1D^2-4. Here we report that enhancing β-cell mass early in life, in two models of female NOD mice, results in immunomodulation of T-cells, reduced islet infiltration and lower β-cell apoptosis, that together protect them from developing T1D. The animals displayed altered β-cell antigens, and islet transplantation studies showed prolonged graft survival in the NOD-LIRKO model. Adoptive transfer of splenocytes from the NOD-LIRKOs prevented development of diabetes in pre-diabetic NOD mice. A significant increase in the splenic CD4⁺CD25⁺FoxP3⁺ regulatory T-cell (Treg) population was observed to underlie the protected phenotype since Treg depletion rendered NOD-LIRKO mice diabetic. The increase in Tregs coupled with activation of TGF-β/SMAD3 signaling pathway in pathogenic T-cells favored reduced ability to kill β-cells. These data support a previously unidentified observation that initiating β-cell proliferation, alone, prior to islet infiltration by immune cells alters the identity of β-cells, decreases pathologic self-reactivity of effector cells and increases Tregs to prevent progression of T1D.

Treatment of allergic rhinitis with CpG oligodeoxynucleotides alleviates the lower airway outcomes of combined allergic rhinitis and asthma syndrome via a mechanism that possibly involves in TSLP

PURPOSE

Thymic stromal lymphopoietin (TSLP) is a critical regulator of immune responses associated with Th2 cytokine-mediated inflammation. Intranasal administration of oligodeoxynucleotides with CpG motifs (CpG-ODNs) might improve lower airway outcomes of combined allergic rhinitis and asthma syndrome (CARAS), but the inherent mechanisms of CpG-ODNs are not well defined. This study investigated whether CpG-ODNs treated to upper airway could reduce lower airway TSLP expression as well as whether this reduction could contribute to the alleviation of lower allergic inflammation and airway hyper-reactivity (AHR) in CARAS mice.

MATERIALS AND METHODS

Ovalbumin (OVA)-sensitized BALB/c mice were intranasal OVA exposure three times a week for 3 weeks. CpG-ODNs or an anti-TSLP mAb was administered to a subset of these mice 1 hour after intranasal OVA challenge, followed by 5 days of OVA aerosol challenge. The resulting immunological variables, nasal symptoms, and nasal mucosa and lung tissues pathology were evaluated. TSLP production in the lung tissues and bronchoalveolar lavage fluid (BALF) were determined by RT-PCR, western blotting or enzyme-linked immunosorbent assay.

RESULTS

The CARAS mice exhibited overexpression of TSLP in the lung tissues and BALF, and also demonstrated significant increases in BALF and splenocyte Th2-associated cytokine production, serum OVA-specific IgE, nose and lung pathologies, and AHR. Intranasal administration of CpG-ODNs restored TSLP in the lower airway, and it significantly reduced the following parameters: Th2-type cytokine production levels; the percentage of eosinophils in the BALF; IL-4 and IL-5 concentrations in the supernatants of cultured splenic lymphocytes; serum OVA-specific IgE; peribronchial inflammation score in the lungs; and nose pathology and nasal symptoms. Similar results were obtained when the CARAS mice were treated with an anti-TSLP mAb to block intranasal TSLP activity.

CONCLUSIONS

Treatment with intranasal CpG-ODNs improves lower airway immunological variable outcomes in the CARAS model via a mechanism that possibly involves in suppressing pulmonary TSLP-triggered allergic inflammation.

A structurally distinct TGF-β mimic from an intestinal helminth parasite potently induces regulatory T cells

Helminth parasites defy immune exclusion through sophisticated evasion mechanisms, including activation of host immunosuppressive regulatory T (Treg) cells. The mouse parasite Heligmosomoides polygyrus can expand the host Treg population by secreting products that activate TGF-β signalling, but the identity of the active molecule is unknown. Here we identify an H. polygyrus TGF-β mimic (Hp-TGM) that replicates the biological and functional properties of TGF-β, including binding to mammalian TGF-β receptors and inducing mouse and human Foxp3⁺ Treg cells. Hp-TGM has no homology with mammalian TGF-β or other members of the TGF-β family, but is a member of the complement control protein superfamily. Thus, our data indicate that through convergent evolution, the parasite has acquired a protein with cytokine-like function that is able to exploit an endogenous pathway of immunoregulation in the host.

Heligmosomoides polygyrus can activate mammalian TGF-β signalling pathways, but how it does so is not known. Here the authors identify and isolate a H. polygyrus TFG-β mimic that can bind both mammalian TGF-β receptor subunits, activate Smad signalling and generate inducible regulatory T cells.

IL-25 attenuates rheumatoid arthritis through suppression of Th17 immune responses in an IL-13-dependent manner

IL-25, a new member of the IL-17 cytokine family, is involved in type 2 immunity initiation and has been associated with the pathogenesis of rheumatoid arthritis (RA). However, its exact role remains unclear. Here, we aimed to analyse IL-25 expression in the serum and synovial fluid of RA patients and evaluated the correlations between serum IL-25 levels, clinical and laboratory values and inflammation cytokines. Additionally, we investigated whether IL-25 can suppress Th1/Th17 responses involved in RA pathogenesis. We further determined whether IL-25 can alleviate collagen-induced arthritis (CIA) development in mice and the underlying mechanisms using in vitro and in vivo experiments. Our results showed that IL-25 was upregulated in the serum and synovial fluid of RA patients. Increased serum IL-25 levels were associated with disease severity and inflammatory response in RA patients. Furthermore, IL-25 inhibited CD4⁺ T-cell activation and differentiation into Th17 cells, without affecting Th1 cells in human RA and CIA models. Administration of IL-25 could attenuate CIA development by Th17 suppression in an IL-13-dependent manner. Our findings indicate that IL-25 plays a potent immunosuppressive role in the pathogenesis of RA and CIA by downregulating Th17 cell response, and thus, may be a potential therapeutic agent for RA.

TGF-β in tolerance, development and regulation of immunity

•

The broader superfamily of TGF-β-like proteins is reviewed, and signaling pathways summarised.

•

The role of TGF-β in the immune tolerance and control of infectious disease is discussed.

•

The superfamily member AMH is involved in embryonic sexual differentiation.

•

Helminth parasites appear to exploit the TGF-β pathway to suppress host immunity.

•

TGF-β homologues and mimics from parasites offer a new route for therapeutic tolerance induction.

The TGF-β superfamily is an ancient metazoan protein class which cuts across cell and tissue differentiation, developmental biology and immunology. Its many members are regulated at multiple levels from intricate control of gene transcription, post-translational processing and activation, and signaling through overlapping receptor structures and downstream intracellular messengers. We have been interested in TGF-β homologues firstly as key players in the induction of immunological tolerance, the topic so closely associated with Ray Owen. Secondly, our interests in how parasites may manipulate the immune system of their host has also brought us to study the TGF-β pathway in infections with longlived, essentially tolerogenic, helminth parasites. Finally, within the spectrum of mammalian TGF-β proteins is an exquisitely tightly-regulated gene, anti-Müllerian hormone (AMH), whose role in sex determination underpins the phenotype of freemartin calves that formed the focus of Ray’s seminal work on immunological tolerance.