A pathogenic role of IL- 17 at the early stage of corneal allograft rejection

A chimeric anti-vascularization immunomodulator prevents high-risk corneal transplantation rejection via ex vivo gene therapy

Corneal blindness affects more than 5 million individuals, with over 180,000 corneal transplantations (CTs) performed annually. In high-risk CTs, almost all grafts are rejected within 10 years. Here, we investigated adeno-associated virus (AAV) ex vivo gene therapy to establish immune tolerance in the corneal allograft to prevent high-risk CT rejection. Our previous work has demonstrated that HLA-G contributes to ocular immune privilege by inhibiting both immune cells and neovascularization; however, homodimerization is a rate-limiting step for optimal HLA-G function. Therefore, a chimeric protein called single-chain immunomodulator (scIM), was engineered to mimic the native activity of the secreted HLA-G dimer complex and eliminate the need for homodimerization. In a murine corneal burn model, AAV8-scIM significantly reduced corneal vascularization and fibrosis. Next, ex vivo AAV8-scIM gene delivery to corneal allografts was evaluated in a high-risk CT rejection rabbit model. All scIM-treated corneas were well tolerated and transparent after 42 days, while 83% of vehicle-treated corneas were rejected. Histologically, AAV-scIM-treated corneas were devoid of immune cell infiltration and vascularization, with minimal fibrosis at the host-graft interface. The data collectively demonstrate that scIM gene therapy prevents corneal neovascularization, reduces trauma-induced corneal fibrosis, and prevents allogeneic CT rejection in a high-risk large animal model.

Immunosenescence, immunotolerance and rejection: clinical aspects in solid organ transplantation

As a consequence of increased lifespan and rising number of elderly individuals developing end-stage organ disease, the higher demand for organs along with a growing availability for organs from older donors pose new challenges for transplantation. During aging, dynamic adaptations in the functionality and structure of the biological systems occur. Consistently, immunosenescence (IS) accounts for polydysfunctions within the lymphocyte subsets, and the onset of a basal but persistent systemic inflammation characterized by elevated levels of pro-inflammatory mediators. There is an emerging consensus about a causative link between such hallmarks and increased susceptibility to morbidities and mortality, however the role of IS in solid organ transplantation (SOT) remains loosely addressed. Dissecting the immune-architecture of immunologically-privileged sites may prompt novel insights to extend allograft survival. A deeper comprehension of IS in SOT might unveil key standpoints for the clinical management of transplanted patients.

The Update Immune-Regulatory Role of Pro- and Anti-Inflammatory Cytokines in Recurrent Pregnancy Losses

Recurrent pregnancy losses (RPL) is a common reproductive disorder with various underlying etiologies. In recent years, rapid progress has been made in exploring the immunological mechanisms for RPL. A propensity toward Th2 over Th1 and regulatory T (Treg) over Th17 immune responses may be advantageous for reproductive success. In women with RPL and animals prone to abortion, an inordinate expression of cytokines associated with implantation and early embryo development is present in the endometrium or decidua secreted from immune and non-immune cells. Hence, an adverse cytokine milieu at the maternal-fetal interface assaults immunological tolerance, leading to fetal rejection. Similar to T cells, NK cells can be categorized based on the characteristics of cytokines they secrete. Decidual NK (dNK) cells of RPL patients exhibited an increased NK1/NK2 ratio (IFN-γ/IL-4 producing NK cell ratios), leading to pro-inflammatory cytokine milieu and increased NK cell cytotoxicity. Genetic polymorphism may be the underlying etiologies for Th1 and Th17 propensity since it alters cytokine production. In addition, various hormones participate in cytokine regulations, including progesterone and estrogen, controlling cytokine balance in favor of the Th2 type. Consequently, the intricate regulation of cytokines and hormones may prevent the RPL of immune etiologies. Local or systemic administration of cytokines or their antagonists might help maintain adequate cytokine milieu, favoring Th2 over Th1 response or Treg over Th17 immune response in women with RPL. Herein, we provided an updated comprehensive review regarding the immune-regulatory role of pro- and anti-inflammatory cytokines in RPL. Understanding the roles of cytokines involved in RPL might significantly advance the early diagnosis, monitoring, and treatment of RPL.

Immunogenetic Role of IL17A Polymorphism in the Pathogenesis of Recurrent Miscarriage

Interleukin-17A (IL17A) is a proinflammatory cytokine and is assumed to play an important role in fetal rejection. In order to evaluate the potential role of IL17A polymorphism in the pathogenesis of recurrent miscarriage (RM), serum IL17A levels were estimated by ELISA. Single-nucleotide polymorphism was assessed by polymerase chain reaction-restriction fragment-length polymorphism (PCR-RFLP) using gene-specific primers and the EcoNI restriction enzyme. Serum IL17A levels were nonsignificantly (p > 0.5) low in RM patients compared with the control group. IL17A gene amplification by PCR yielded the undigested product of 815 bp, and its digestion with EcoNI enzyme produced 815, 529, 286, and 270 bp fragments for the GG genotype; 529, 286, and 270 bp fragments for the GA genotype; and 529 and 286 bp fragments for the AA genotype. The genotype frequency between the RM and control groups exhibited a significant difference (p = 0.001), whereas no significant difference was observed between allele frequencies in the two groups (p = 0.0954). These data suggest that the IL17A gene polymorphism exhibits no significant effect on IL17A gene expression. However, it significantly decreases and increases RM risk in the homozygous and recessive models, suggesting its potential pregnancy-protecting and -harming roles in the AA and GA + GG genotypes, respectively.

Cytokine-driven positive feedback loop organizes fibroblast transformation and facilitates gastric cancer progression

BACKGROUND

Gastric cancer (GC) is a malignancy that belongs to one of the most common leading causes of cancer death. Cancer-associated fibroblasts (CAFs) promote the GC cells' malignant behavior. It is still unknown how GC converts normal fibroblasts (NFs) to CAFs.

METHODS

GC cells were co-cultured with NFs. Bioinformatics was used to analyze the genes and signaling pathways that were changed in fibroblast. RT-PCR, western blot, and Elisa assays were used to detect the expression of cytokines in fibroblast and condition medium. Western blot and immunofluorescence demonstrated activation of relevant pathways in CAFs-like cells. Transwell, scrape, colony formation, and CCK-8 assays were performed to reveal the feedback effect of CAFs-like cells on GC cells.

RESULTS

GC promoted the conversion of NFs to CAFs by secreting Interleukin 17A (IL-17). It included both morphological and molecular marker changes. This process was achieved by activating the nuclear factor-κB (NF-κB) pathway. On the other hand, CAFs cells could secrete C-X-C Motif Chemokine Ligand 8 (IL-8, IL-8), which promoted the malignant phenotype of GC cells. In this way, a feedback loop of mutual influence was constructed in the GC and tumor microenvironment (TME).

CONCLUSIONS

Our research proved a novel model of GC-educated NFs. GC-IL-17-fibroblast-IL-8-GC axis might be a potential pathway of the interaction between GC and TME.

Lentivirus-mediated PD-L1 overexpression in bone marrow-derived dendritic cells induces immune tolerance in a rat keratoplasty model

PURPOSE

The side effects of immune suppressants on immune rejection have become increasingly apparent after keratoplasty. To find out new alternative immunotherapy strategies, we studied the role of programmed death-1 (PD-1) and its ligand (PD-L1) co-stimulatory pathway in inducing immune tolerance of rat keratoplasty.

METHODS

The PD-L1 protein was constitutively overexpressed via lentiviral transduction in bone marrow-derived dendritic cells (BMDCs) from rats, then infused via the tail vein into rats before undergoing keratoplasty. Western blot analysis of PD-L1 protein confirmed the effectiveness of lentivirus-mediated. The phenotype of immature BMDC was confirmed by flow cytometry analysis with CD80, CD86, CD11c and MHC-II antibodies. To investigate the mechanism of the immune tolerance induced by BMDCs transfusion, PD-L1, IFN-γ and IL-17 in serum and cell culture supernatant were assessed by ELISA and qPCR.

RESULTS

After LPS stimulation, immature dendritic cells with over-expression of PD-L1 still showed high expression of PD-L1(p < 0.001), and low expression of IL-17 and IFN-γ (p < 0.001), which reduced neovascularization (p < 0.05), and prolonged the survival after corneal implants.

CONCLUSION

Immature DC cells with overexpression of PD-L1 have low ability to activate T cells，which is a potential treatment for avoiding graft rejection by promoting natural immunosuppression. This cellular treatment is expected to reduce the use of immune suppressants and the occurrence of side effects.

At Embryo Implantation Site IL-35 Secreted by Trophoblast, Polarizing T Cells towards IL-35+ IL-10+ IL-4+ Th2-Type Cells, Could Favour Fetal Allograft Tolerance and Pregnancy Success

We investigated the role of rhIL-35, at low concentrations compatible with those produced by human trophoblast cells (less than 1 ng/mL), on human T helper (Th) cell functions and the presence of decidual IL-35-producing Th cells in human pregnancy. We found that human trophoblast cells produced IL-35 but not IL-4 or IL-10. RhIL-35, at concentrations produced by human trophoblasts, polarized T cells towards IL-35+, IL-10+, IL-4+ Th2-type cells and to Foxp3+ EBI3+ p35+ T reg cells producing IL-35 but not IL-10 and IL-4. Moreover, rhIL-35 at low concentrations did not suppress the proliferation of Th cells but stimulated IL-4 and IL-10 production by established Th clones. In particular, Th1-type clones acquired the capacity to produce IL-4. In addition, purified human trophoblast cell supernatants containing IL-35 upregulated IL-4 and IL-10 production by Th clones. Finally, IL-35+, IL-10+, IL-4+ Th2-type cells, which were found to be induced by low concentrations of IL-35 compatible with those produced by human trophoblasts, are exclusively present in the decidua of a successful pregnancy and at the embryo implantation site, suggesting their stringent dependence on trophoblast cells. Thus, the proximity of Th cells to IL-35-producing trophoblasts could be the determining factor for the differentiation of IL-35+, IL-10+, IL-4+ Th2-type cells that are crucial for human pregnancy success.

Loss of miR-673-5p expression in the cornea promotes rat corneal allograft rejection by promoting Th17 cell differentiation mediated by JAK2/STAT3

Background

Cluster of differentiation 4 positive (CD4⁺) T cells play an important role in corneal graft rejection, especially the dynamic balance between regulatory T cells and helper T cells. This study aims to explore the upstream and downstream regulatory mechanisms of Th17 cell differentiation-mediated corneal allograft rejection.

Methods

By establishing rat corneal allograft transplantation model, transcriptome analysis was carried out to screen the differentially expressed genes related to T helper 17 (Th17) cell differentiation, and then cell experiments were used to verify the effect of miR-673-5p/Janus Kinase 2 (JAK2) signal on naïve CD4⁺ T cell differentiation and the proliferation, migration, and tube formation ability of human umbilical vein endothelial cells (HUVECs). Finally, the role of miR-673-5p/JAK2 signal in corneal allograft rejection was verified by animal model in vivo.

Results

The results showed that JAK2/STAT3 signaling activation-mediated Th17 cell differentiation was significantly up-regulated during corneal allograft rejection, and miR-673-5p expression was down-regulated after corneal allograft rejection. Low expression of miR-673-5p promoted Th17 cell differentiation by up-regulating JAK2, and then promoted placental growth factor (PLGF)mediated corneal neovascularization (CNV).

Conclusions

The results of this study suggested that low expression of miR-673-5p is a promoter of corneal allograft rejection. Overexpression of miR-673-5p can improve the survival rate of corneal allografts by inhibiting the differentiation and maturation of Th17 cells mediated by JAK2/STAT3 signaling.

Cytokines, Hormones and Cellular Regulatory Mechanisms Favoring Successful Reproduction

Its semi-allogeneic nature renders the conceptus vulnerable to attack by the maternal immune system. Several protective mechanisms operate during gestation to correct the harmful effects of anti-fetal immunity and to support a healthy pregnancy outcome. Pregnancy is characterized by gross alterations in endocrine functions. Progesterone is indispensable for pregnancy and humans, and it affects immune functions both directly and via mediators. The progesterone-induced mediator - PIBF - acts in favor of Th2-type immunity, by increasing Th2 type cytokines production. Except for implantation and parturition, pregnancy is characterized by a Th2-dominant cytokine pattern. Progesterone and the orally-administered progestogen dydrogesterone upregulate the production of Th2-type cytokines and suppress the production of Th1 and Th17 cytokine production in vitro. This is particularly relevant to the fact that the Th1-type cytokines TNF-α and IFN-γ and the Th17 cytokine IL-17 have embryotoxic and anti-trophoblast activities. These cytokine-modulating effects and the PIBF-inducing capabilities of dydrogesterone may contribute to the demonstrated beneficial effects of dydrogesterone in recurrent spontaneous miscarriage and threatened miscarriage. IL-17 and IL-22 produced by T helper cells are involved in allograft rejection, and therefore could account for the rejection of paternal HLA-C-expressing trophoblast. Th17 cells (producing IL-17 and IL-22) and Th22 cells (producing IL-22) exhibit plasticity and could produce IL-22 and IL-17 in association with Th2-type cytokines or with Th1-type cytokines. IL-17 and IL-22 producing Th cells are not harmful for the conceptus, if they also produce IL-4. Another important protective mechanism is connected with the expansion and action of regulatory T cells, which play a major role in the induction of tolerance both in pregnant women and in tumour-bearing patients. Clonally-expanded Treg cells increase at the feto-maternal interface and in tumour-infiltrating regions. While in cancer patients, clonally-expanded Treg cells are present in peripheral blood, they are scarce in pregnancy blood, suggesting that fetal antigen-specific tolerance is restricted to the foeto-maternal interface. The significance of Treg cells in maintaining a normal materno-foetal interaction is underlined by the fact that miscarriage is characterized by a decreased number of total effector Treg cells, and the number of clonally-expanded effector Treg cells is markedly reduced in preeclampsia. In this review we present an overview of the above mechanisms, attempt to show how they are connected, how they operate during normal gestation and how their failure might lead to pregnancy pathologies.

The NLRP3 inflammasome regulates corneal allograft rejection through enhanced phosphorylation of STAT3

The success of corneal transplantation is limited by allograft rejection, but the pathogenic mechanisms of this disease remain poorly defined. In this study, we showed that the NOD, LRR-and pyrin domain-containing protein3 (NLRP3) inflammasome-mediated interleukin-1β (IL-1β) production exacerbated corneal allograft rejection. Extracellular ATP contributed to the NLRP3 inflammasome-mediated IL-1β release, which in turn was preferentially skewed toward Th17 differentiation via enhanced phosphorylation of STAT3. Pharmacological inhibition of IL-1β/IL-6-STAT3 signaling significantly delayed corneal allograft rejection. Thus, the identification of NLRP3 inflammasome's key role sheds new light on the pathogenesis of corneal allograft rejection and opens a potential new avenue for treating or preventing corneal allograft rejection.

Novel immunotherapeutic effects of topically administered ripasudil (K-115) on corneal allograft survival

Corneal allograft survival is mediated by the variety of immunological reactions and wound healing process. Our aim was to explore the effects of topical administration of ripasudil, a selective Rho-associated coiled-coil protein kinase inhibitor, on corneal allograft survival. Ripasudil was administered to mice thrice a day after allogeneic corneal transplantation. Corneal graft survival, opacity, neovascularization, re-epithelization, immune cell infiltration, and mRNA levels of angiogenic and pro-inflammatory factors in the grafted cornea and draining lymph nodes (dLNs) were evaluated with slit-lamp microscopy, immunohistochemistry, flow cytometry, and polymerase chain reaction. Graft survival was significantly prolonged with lower graft opacity and neovascularization scores in 0.4% and 2.0% ripasudil-treated groups, and mRNA levels of angiogenic and pro-inflammatory factors in ripasudil-treated grafted corneas were reduced. Moreover, 0.4% and 2.0% ripasudil reduced CD45⁺-infiltrated leukocyte frequency, Cd11b and Cd11c mRNA levels, and the frequencies of mature dendritic cells, IFNγ-, and IL-17- producing CD4⁺T cells in the dLNs of recipients. Re-epithelization rate of the grafted cornea was significantly higher in the 0.4% and 2.0% ripasudil groups than in the control. Topically applied ripasudil prolonged graft survival by downregulating neovascularization and inflammation factors, while promoting corneal re-epithelization, suggesting that ripasudil may be useful for suppressing immunological rejection in corneal transplantation.

Blockade of costimulatory CD27/CD70 pathway promotes corneal allograft survival

PURPOSE

To determine whether the CD27/CD70 pathway plays a significant role in corneal allograft rejection by investigating the effect of blocking the CD27/CD70 pathway by anti-CD70 antibody on corneal allograft survival.

METHODS

Orthotopic penetrating keratoplasty was performed using C57BL/6 donor grafts and BALB/c recipients. Expression of CD27 and CD70 on rejected cornea was examined by immunohistochemistry. Corneal transplant recipients received intraperitoneal injection of anti-CD70 antibody (FR70) or control rat IgG. Alloreactivity was measured by mixed lymphoid reaction (MLR) in recipients administered control rat IgG and those administered anti-CD70 antibody. Corneal expression of IFN-γ and IL-12 was also examined in both groups. Graft opacity was assessed over an 8-week period and graft survival was evaluated using Kaplan-Meier survival curves. Proportion of CD4⁺CD44⁺ memory T cells in lymph nodes was measured by flow cytometry.

RESULTS

CD4⁺CD27⁺ cells and CD11c⁺CD70⁺ cells were present in rejected cornea. Anti-CD70 antibody administration suppressed alloreactivity in corneal allograft recipients, and inhibited IFN-γ expression in recipient cornea (p < 0.05). Anti-CD70 antibody suppressed opacity score of recipient cornea and prolonged corneal allograft survival (p < 0.05). Proportion of CD4⁺CD44⁺ memory T cells in recipient lymph nodes was reduced by anti-CD70 antibody treatment.

CONCLUSION

The CD27/CD70 pathway plays a significant role in corneal allograft rejection by initiating alloreactive Th1 cells and preserving memory T cells. Anti-CD70 antibody administration prolongs corneal allograft survival indicating the potential therapeutic effect of CD27/CD70 pathway blockade on corneal allograft rejection.

Probiotic Enterococcus faecalis Symbioflor 1 ameliorates pathobiont-induced miscarriage through bacterial antagonism and Th1-Th2 modulation in pregnant mice

The bacterium-bacterium interaction between pathogenic and probiotic Enterococcus as well as the bacterium-host interaction between Enterococcus and intestinal epithelium has drawn increasing attentions, but the influence of those interactions on host pregnancy remains largely unexplored. In the present study, we evaluated the effects of probiotic E. faecalis Symbioflor 1 or/and pathogenic E. faecalis OG1RF on the miscarriage of pregnant mice. Using in vitro assays of competition and exclusion and displacement, antagonistic property of E. faecalis Symbioflor 1 against E. faecalis OG1RF was observed, and the former inhibited the translocation of the later in vivo. The rate of miscarriage induced by E. faecalis OG1RF challenge was significantly reduced by 28% with E. faecalis Symbioflor 1 intervention; and the tissue integrity of ileum, colon, uterus, and placenta and placental blood cell density in pregnant mice were drastically improved by such probiotic intervention. Compared with the controls, probiotic intervention significantly upregulated the level of IL-10 and TGF-β, downregulated levels of IFN-γ, and increased progesterone level that reversed the trend of being Th1 predominance state reported for adverse pregnancy outcome at early pregnancy stage. In conclusion, E. faecalis Symbioflor 1 decreased the translocation of E. faecalis OG1RF, prevented pathogen-induced tissue damage, and changed Th1-Th2 homeostasis toward Th2 predominance during early pregnancy resulting in decreased miscarriage. KEY POINTS: •The mechanism of how probiotic E. faecalis Symbioflor 1 improves pregnancy of mice • Influence of interactions of pathogenic and probiotic Enterococcus on host pregnancy • E. faecalis Symbioflor 1 change Th1-Th2 homeostasis toward Th2 predominance.

Corneal graft melting: a systematic review

Corneal graft melting is a severe complication of keratoplasty. This review is to summarize the incidence, the pathogenesis, the risk factors, the prognosis and the prevention of corneal graft melting after keratoplasty. We systematically searched PubMed, Web of Science and WanFang database to retrieve potentially eligible articles about relevant clinical reports and animal experiments. We read the full texts to identify eligible articles. The selection of studies and data extraction were performed independently by two reviewers. In conclusion, the pathogenesis of corneal graft melting is complicated, and many risk factors are closely related to corneal graft melting. Analysis of pathogenesis and risk factors of corneal graft melting can facilitate the development of targeted therapies to better guide clinical practice.

Tocilizumab promotes corneal allograft survival in rats by modulating Treg-Th17 balance

AIM

To examine the therapeutic effects of tocilizumab on experimental corneal transplantation and its effect on Treg/Th17 balance.

METHODS

Allograft corneal graft was performed between host Sprague Dawley and Wistar donor rats. The rats were randomly divided into four groups: normal, autograft, allograft, and allograft treated with tocilizumab. Kaplan-Meier was performed to draw the survival curve. The protein levels of interleukin-17A (IL-17A), vascular endothelial growth factor (VEGF), and forkhead box protein 3 (Foxp3) were measured by immunohistochemistry. The mRNA levels of IL-17A, VEGF, retinoid-related orphan receptor gammat (RORγt), interleukin-6 (IL-6) and Foxp3 were detected by reverse transcription real-time polymerase chain reaction (RT-PCR). The Treg and Th17 cells were investigated by flow cytometry.

RESULTS

The survival time of tocilizumab group was (24±1.27d) longer than that of allograft group (10±0.55d). Moreover, immunohistochemical examination revealed that IL-17A and VEGF protein levels in the allograft group were significantly higher than that of tocilizumab group (P<0.01), while Foxp3 levels in the allograft group was significantly lower than that of the tocilizumab treated group (P<0.001). Flow cytometry showed that the number of Th17 cells in allograft group was significantly higher than that in tocilizumab group (P<0.001). Meanwhile, the number of Tregs was significantly lower than in tocilizumab group (P<0.001). Simultaneously, Foxp3 mRNA expression level in corneal tissues of tocilizumab treated group was significantly higher than other groups (P<0.001).

CONCLUSION

These findings suggest that tocilizumab may promote corneal allograft survival, possibly by modulating Treg-Th17 balance.

Effectiveness of Perioperative Immunologic Markers Monitoring for Predicting Early Acute Cellular Rejection After Living Donor Liver Transplantation

BACKGROUND

The objective of this study was to determine whether perioperative immunologic markers monitoring could predict early acute cellular rejection (ACR) after living donor liver transplantation (LDLT).

MATERIALS AND METHODS

From September 2010 to June 2013, a total of 172 patients underwent LDLT at our transplant center. Of them, 26 patients were excluded because of infection. We retrospectively reviewed the remaining 146 patients. CD4 lymphocyte activity, T cell subsets test, and serum cytokine panel were checked on the day before transplantation and at 20 days after transplantation. These patients were divided into 3 groups: 1. normal liver function test (LFT) group; 2. increased LFT without rejection group; and 3. early ACR group. We excluded the increased LFT without rejection group in order to rule out multiple factors influencing immunologic factors.

RESULTS

CD4 lymphocyte activity (P = .004) was significantly increased while CD4+/CD25+/FOXP3+ cells (P < .001) and interleukin (IL)-17 (P = .002) levels were significantly decreased during the perioperative period. Pretransplant IL-6 (P = .014) and IL-17 (P = .029) levels in the early ACR group were significantly lower than those in the normal LFT group. The proportion of patients with increased IL-6 during perioperative period in the early ACR group was higher than that in the normal LFT group, although the difference was not statistically significant (P = .065).

CONCLUSION

Our results suggest that IL-6 and IL-17 levels are associated with early ACR in LDLT patients. However, whether monitoring perioperative immunologic markers could predict early ACR remains unclear. Further prospective studies are needed to reach a definite conclusion.

Resolvin E1 Inhibits Corneal Allograft Rejection in High-Risk Corneal Transplantation

Purpose

To investigate the effects of Resolvin E1 (RvE1) on corneal allograft rejection in a high -risk corneal allograft transplantation model.

Methods

High-risk corneal beds were created via placement of intrastromal sutures in the corneas of BALB/c mice for 2 weeks. Allogeneic corneal transplantation was performed by transplanting corneas of C57BL/6 mice onto BALB/c hosts. RvE1 or normal saline (control) was subconjunctivally injected. Allograft survival was observed by slit lamp biomicroscope, and inflammatory cell infiltration was detected by hematoxylin and eosin and immunohistochemistry. The percentage of Th1, Th17, and Treg cells in draining lymph nodes (DLNs) were evaluated by flow cytometric analysis. The levels of Th1, Th2, and Th17-associated cytokines in the grafts were measured by cytometric bead array and real-time PCR.

Results

RvE1 treatment significantly improved allograft survival compared to the control group. After RvE1 treatment, the infiltration of neutrophils and CD4+ T (Th1/Th17) cells were decreased in corneal grafts, and the percentage of Th1/Th17 cells in DLNs were reduced. In addition, RvE1 treatment significantly reduced the mRNA expression of proinflammatory cytokines in the graft including IL-1α, IL-1β, TNF-α, IL-2, IL-6, IFN-γ, IL-17A, IL-17F, IL-21, and IL-22 as well as the protein level of the proinflammatory cytokines, including IL-2, TNF, IL-6, IFN-γ, and IL-17. However, RvE1 treatment did not alter the percentage of Treg cells in DLNs and the expression of IL-4, IL-5, and IL-10.

Conclusions

RvE1 treatment improves allogeneic corneal graft survival in a high-risk corneal transplantation model via inhibiting the Th1/Th17-related inflammation.

Decidual Interleukin-22-Producing CD4+ T Cells (Th17/Th0/IL-22+ and Th17/Th2/IL-22+, Th2/IL-22+, Th0/IL-22+), Which Also Produce IL-4, Are Involved in the Success of Pregnancy

Trophoblast expressing paternal HLA-C resembles a semiallograft, and could be rejected by maternal T cells. IL-22 seems to be involved in allograft rejection and thus could be responsible for miscarriages. We examined the role of decidual IL-22-producing CD4+ T on human pregnancy. In those experiencing successful pregnancy and those experiencing unexplained recurrent abortion (URA), the levels of IL-22 produced by decidual CD4+ T cells are higher than those of peripheral blood T cells. We found a correlation of IL-22 and IL-4 produced by decidual CD4+ T cells in those experiencing successful pregnancy, not in those experiencing URA. The correlation of IL-22 and IL-4 was also found in the serum of successful pregnancy. A prevalence of CD4+ T cells producing IL-22 and IL-4 (Th17/Th2/IL-22+, Th17/Th0/IL-22+, Th17/Th2/IL-22+, and Th0/IL-22+ cells) was observed in decidua of those experiencing successful pregnancy, whereas Th17/Th1/IL-22+ cells, which do not produce IL-4, are prevalent in those experiencing URA. Th17/Th2/IL-22+ and Th17/Th0/IL-22+ cells are exclusively present at the embryo implantation site where IL-4, GATA-3, IL-17A, ROR-C, IL-22, and AHR mRNA are expressed. T-bet and IFN-γ mRNA are found away from the implantation site. There is no pathogenic role of IL-22 when IL-4 is also produced by decidual CD4+ cells. Th17/Th2/IL-22+ and Th17/Th0/IL-22+ cells seem to be crucial for embryo implantation.

Carbon monoxide and its donors - their implications for medicine

Inhalation of high concentrations of carbon monoxide (CO) is known to lead to serious systemic complications and neuronal disturbances. However, it has been found that not only is CO produced endogenously, but also that low concentrations can bestow beneficial effects which may be of interest in biology and medicine. As translocation of CO through the human organism is difficult, small molecules known as CO-releasing molecules (CORMs) deliver controlled amounts of CO to biological systems, and these are of great interest from a medical point of view. These actions may prevent vascular dysfunction, regulate blood pressure, inhibit blood platelet aggregation or have anti-inflammatory effects. This review summarizes the functions of various CO-releasing molecules in biology and medicine.

Universal Corneal Epithelial-Like Cells Derived from Human Embryonic Stem Cells for Cellularization of a Corneal Scaffold

Purpose

We generated universal corneal epithelial cells (CEC) from human embryonic stem cells (hESC) by genetically removing human leukocyte antigens (HLA) class I from the cell surface.

Methods

The serum-free, growth factor-free, and defined medium E6 was used to differentiate hESC to CEC. Decellularized murine corneas were recellularized with hESC-derived CEC. Using CRISPR/Cas9, β-2-microglobulin (B2M) was deleted in hESC to block the assembly of HLA class-I antigens on the cell surface to generate B2M^−/− CEC.

Results

E6 alone was sufficient to allow hESC differentiation to CEC. A time-course analysis of the global gene expression of the differentiating cells indicates that the differentiation closely resembles the corneal development in vivo. The hESC-CEC were highly proliferative, and could form multilayer epithelium in decellularized murine cornea, retain its transparency, and form intact tight junctions on its surface. As reported before, B2M knockout led to the absence of HLA class-I on the cell surface of hESC and subsequently derived CEC following stimulation with inflammatory factors. Moreover, B2M^−/− CEC, following transplantation into mouse eyes, caused less T-cell infiltration in the limbal region of the eye than the wild-type control.

Conclusions

CEC can be derived from hESC via a novel and simple protocol free of any proteins, hESC-CEC seeded on decellularized animal cornea form tight junctions and allow light transmittance, and B2M^−/− CEC are hypoimmunogenic both in vitro and in vivo.

Translational Relevance

B2M^−/− hESC-CEC can be an unlimited and universal therapy for corneal repair in patients of any HLA type.

The Balance of Th1/Th2 and LAP+Tregs/Th17 Cells Is Crucial for Graft Survival in Allogeneic Corneal Transplantation

Purpose

CD4+LAP+ T cells are newly discovered regulatory T cells (Tregs). The aim of this study is to investigate the balance of Th1/Th2 and LAP+Tregs/Th17 in mice after allogeneic corneal transplantation.

Methods

A total of 65 mice received orthotopic penetrating transplantation. According to the survival scores of the grafts, the mice were divided into the rejection group and the survival group 3 weeks after transplantation. Th1, Th2, Th17, and regulatory T cells in the ipsilateral drainage lymph nodes and spleens were measured with flow cytometry. The related cytokines in aqueous humor were also analyzed.

Results

The frequencies of Foxp3+Tregs, GARP+Tregs, and LAP+Tregs in the survival group were significantly higher than those in the rejection group. And the expression trend of CD4+LAP+ T cells and CD4+GARP+ T cells was consistent. The level of IFN-γ, TNF, IL-6, and IL-17A markedly increased in aqueous humor during corneal allograft rejection. The ratio of Th1/Th2 and Th17/LAP+Tregs significantly increased in the rejection group at the 3rd week after corneal transplantation.

Conclusion

LAP+Tregs might be regarded as substitute for Foxp3+Tregs. The balance of Th1/Th2 and LAP+Tregs/Th17 is crucial for corneal allograft survival.

Comparative immunological study of penetrating and anterior lamellar keratoplasty in a murine model

In lamellar keratoplasty, the diseased part of a cornea is replaced while the healthy tissue remains lamellar keratoplasty has the advantage of better graft survival compared to penetrating keratoplasty (PK). We compared the immunological responses to PK and anterior lamellar keratoplasty (ALK) in a murine model. PK or ALK was performed using C57BL/6 donor grafts and BALB/c recipients, and graft opacity was assessed to evaluate graft rejection up to 8 weeks. We evaluated the immunological responses in both groups, which were not clinically considered as graft failure on postoperative day 21. PK mice showed reduced clinical graft survival compared to ALK mice. The mRNA expression of inflammatory mediators, such as IL-1β, IFN-γ, and granzyme B, in grafted corneas of PK mice, was significantly increased compared to the levels in ALK mice at postoperative day 21. PK led to a higher delayed-type hypersensitivity response and IFN-γ secretion in an in vitro T cell assay from draining lymph nodes (LNs), as compared to ALK. Furthermore, PK showed increased angiogenesis and lymphangiogenesis in grafted corneas compared to ALK and led to greater infiltration of CD3⁺ T cells into grafted corneas and increased frequencies of mature antigen presenting cells (APC; MHC-II^highCD11c + cells) and IL-12 + dendritic cells (DCs) in the draining LNs of transplanted mice. In conclusion, PK results in increased graft rejection compared to ALK through relatively increased neovascularization and lymphangiogenesis, which can induce infiltration of pathologic T cells and mature APC migration into grafted corneas and draining LNs.

Alloimmunity and Tolerance in Corneal Transplantation

Corneal transplantation is one of the most prevalent and successful forms of solid tissue transplantation. Despite favorable outcomes, immune-mediated graft rejection remains the major cause of corneal allograft failure. Although low-risk graft recipients with uninflamed graft beds enjoy a success rate ∼90%, the rejection rates in inflamed graft beds or high-risk recipients often exceed 50%, despite maximal immune suppression. In this review, we discuss the critical facets of corneal alloimmunity, including immune and angiogenic privilege, mechanisms of allosensitization, cellular and molecular mediators of graft rejection, and allotolerance induction.

Expression, Regulation, and Effects of Interleukin-17f in the Human Ocular Surface

PURPOSE

To evaluate the basal and possibly stimulated expression of interleukin (IL)-17 in the context of the ocular surface and potential downstream effects.

METHODS

Western blot and immunofluorescent staining were used to evaluate IL-17F expression in human cornea/conjunctival tissues and cornea epithelial cell line. Cytokines and matrix metalloproteinase (MMP) transcripts were quantified by qPCR. IL-17F effects on NF-κB were investigated by the secretary alkaline phosphatase assay.

RESULTS

IL-17F was expressed in the cytoplasm of human corneal and conjunctival epithelial tissues. In the corneal cell line, exogenous IL-17F did not increase the NF-κB activity, but Pam3CSK4 increased IL-17F transcripts. IL-17F stimulated MMP-9 activity, promoted IL-6, IL-8, tumor necrosis factor-α transcripts levels, and depressed monocyte chemoattractant protein-1 expression, but did not affect transforming growth factor beta-1 transcript levels.

CONCLUSIONS

Normal corneal/conjunctival epithelial cells express IL-17F. Microbial agents may stimulate IL-17F via the NF-κB pathway. Matrix dissolution stimulated by IL-17F may have a role in the melting and necrosis of cornea in severe inflammation.

How pregnancy can affect autoimmune diseases progression?

Autoimmune disorders are characterized by tissue damage, caused by self-reactivity of different effectors mechanisms of the immune system, namely antibodies and T cells. Their occurrence may be associated with genetic and/or environmental predisposition and to some extent, have implications for fertility and obstetrics. The relationship between autoimmunity and reproduction is bidirectional. This review only addresses the impact of pregnancy on autoimmune diseases and not the influence of autoimmunity on pregnancy development. Th17/Th1-type cells are aggressive and pathogenic in many autoimmune disorders and inflammatory diseases. The immunology of pregnancy underlies the role of Th2-type cytokines to maintain the tolerance of the mother towards the fetal semi-allograft. Non-specific factors, including hormonal changes, favor a switch to Th2-type cytokine profile. In pregnancy Th2, Th17/Th2 and Treg cells accumulate in the decidua but may also be present in the mother’s circulation and can regulate autoimmune responses influencing the progression of autoimmune diseases.

Effects of an intravitreal injection of interleukin-35-expressing plasmid on pro-inflammatory and anti-inflammatory cytokines

In order to explore the potential effects of interleukin (IL)-35 on IL-10, transforming growth factor-β (TGF-β), interferon-γ (INF)-γ, IL-12 and IL-17, a pcDNA3.1‑IL-35 plasmid was injected into the vitreous cavity of BALB/c mice. Enzyme-linked immunosorbent assay, western blot analysis and quantitative PCR analysis were performed to confirm the successful expression of IL-35. Slit-lamp biomicroscopy, hematoxylin and eosin staining and immunofluorescence were employed to detect the status of eyes, and western blot analysis was performed to examine the expression of corneal graft rejection-related cytokines. There were no abnormalities in the eyes pre-mydriasis or post-mydriasis and no injuries to the cornea or retina following the injection of IL-35-expressing plasmid. An immunofluorescence assay detected the positive expression of IL-35 in corneal epithelial cells from IL-35‑injected mice and negative staining in the control group. Further study revealed that IL-35 enhanced the expression of IL-10 and TGF-β which reached their highest levels at 1 and 2 weeks after injection, respectively (p<0.01). Moreover, the expression of INF-γ and IL-12 was decreased significantly at 2 weeks after the injection of IL-35-expressing plasmid (p<0.05), and the expression of IL-17 was suppressed notably at 4 weeks after the injection (p<0.05). The intravitreal injection of IL-35-expressing plasmid in mice downregulates the expression of pro-inflammatory cytokines and upregulates the expression of anti-inflammatory cytokines. Thus, IL-35 may further be assessed as a potential target for the treatment of corneal graft rejection.

Host immune cellular reactions in corneal neovascularization

Corneal neovascularization (CNV) is a global important cause of visual impairment. The immune mechanisms leading to corneal heme- and lymphangiogenesis have been extensively studied over the past years as more attempts were made to develop better prophylactic and therapeutic measures. This article aims to discuss immune cells of particular relevance to CNV, with a focus on macrophages, Th17 cells, dendritic cells and the underlying immunology of common pathologies involving neovascularization of the cornea. Hopefully, a thorough understanding of these topics would propel the efforts to halt the detrimental effects of CNV.

High-risk corneal allografts: A therapeutic challenge

Corneal transplantation is the most common surgical procedure amongst solid organ transplants with a high survival rate of 86% at 1-year post-grafting. This high success rate has been attributed to the immune privilege of the eye. However, mechanisms originally thought to promote immune privilege, such as the lack of antigen presenting cells and vessels in the cornea, are challenged by recent studies. Nevertheless, the immunological and physiological features of the cornea promoting a relatively weak alloimmune response is likely responsible for the high survival rate in “low-risk” settings. Furthermore, although corneal graft survival in “low-risk” recipients is favourable, the prognosis in “high-risk” recipients for corneal graft is poor. In “high-risk” grafts, the process of indirect allorecognition is accelerated by the enhanced innate and adaptive immune responses due to pre-existing inflammation and neovascularization of the host bed. This leads to the irreversible rejection of the allograft and ultimately graft failure. Many therapeutic measures are being tested in pre-clinical and clinical studies to counter the immunological challenge of “high-risk” recipients. Despite the prevailing dogma, recent data suggest that tissue matching together with use of systemic immunosuppression may increase the likelihood of graft acceptance in “high-risk” recipients. However, immunosuppressive drugs are accompanied with intolerance/side effects and toxicity, and therefore, novel cell-based therapies are in development which target host immune cells and restore immune homeostasis without significant side effect of treatment. In addition, developments in regenerative medicine may be able to solve both important short comings of allotransplantation: (1) graft rejection and ultimate graft failure; and (2) the lack of suitable donor corneas. The advances in technology and research indicate that wider therapeutic choices for patients may be available to address the worldwide problem of corneal blindness in both “low-risk” and “high-risk” hosts.

Interleukin-17-producing decidual CD4+ T cells are not deleterious for human pregnancy when they also produce interleukin-4

Background

Trophoblast expressing paternal HLA-C antigens resemble a semiallograft, and could be rejected by maternal CD4+ T lymphocytes. We examined the possible role in human pregnancy of Th17 cells, known to be involved in allograft rejection and reported for this reason to be responsible for miscarriages. We also studied Th17/Th1 and Th17/Th2 cells never investigated before. We defined for the first time the role of different Th17 subpopulations at the embryo implantation site and the role of HLA-G5, produced by the trophoblast/embryo, on Th17 cell differentiation.

Methods

Cytokine production by CD4+ purified T cell and T clones from decidua of normal pregnancy, unexplained recurrent abortion, and ectopic pregnancy at both embryo implantation site and distant from that site were analyzed for protein and mRNA production. Antigen-specific T cell lines were derived in the presence and in the absence of HLA-G5.

Results

We found an associated spontaneous production of IL-17A, IL-17F and IL-4 along with expression of CD161, CCR8 and CCR4 (Th2- and Th17-type markers) in fresh decidua CD4+ T cells during successful pregnancy. There was a prevalence of Th17/Th2 cells (producing IL-17A, IL-17F, IL-22 and IL-4) in the decidua of successful pregnancy, but the exclusive presence of Th17 (producing IL-17A, IL-17F, IL-22) and Th17/Th1 (producing IL-17A, IL-17F, IL-22 and IFN-γ) cells was found in the decidua of unexplained recurrent abortion. More importantly, we observed that Th17/Th2 cells were exclusively present at the embryo implantation site during tubal ectopic pregnancy, and that IL-4, GATA-3, IL-17A, ROR-C mRNA levels increased in tubal biopsies taken from embryo implantation sites, whereas Th17, Th17/Th1 and Th1 cells are exclusively present apart from implantation sites. Moreover, soluble HLA-G5 mediates the development of Th17/Th2 cells by increasing IL-4, IL-17A and IL-17F protein and mRNA production of CD4+ T helper cells.

Conclusion

No pathogenic role of decidual Th17 cells during pregnancy was observed. Indeed, a beneficial role for these cells was observed when they also produced IL-4. HLA-G5 could be the key feature of the uterine microenvironment responsible for the development of Th17/Th2 cells, which seem to be crucial for successful embryo implantation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12948-016-0039-y) contains supplementary material, which is available to authorized users.

Differences in CD44 Surface Expression Levels and Function Discriminates IL-17 and IFN-γ Producing Helper T Cells

CD44 is a prominent activation marker which distinguishes memory and effector T cells from their naïve counterparts. It also plays a role in early T cell signaling events as it is bound to the lymphocyte-specific protein kinase and thereby enhances T cell receptor signalling. Here, we investigated whether IFN-γ and IL-17 producing T helper cells differ in their CD44 expression and their dependence of CD44 for differentiation. Stimulation of CD4+ T cells with allogeneic dendritic cells resulted in the formation of three distinguishable populations: CD44+, CD44++ and CD44+++. In vitro and in vivo generated allo-reactive IL-17 producing T helper cells were mainly CD44+++ as compared to IFN-γ+ T helper cells, which were CD44++. This effect was enhanced under polarizing conditions. T helper 17 polarization led to a shift towards the CD44+++ population, whereas T helper 1 polarization diminished this population. Furthermore, blocking CD44 decreased IL-17 secretion, while IFN-γ was barely affected. Titration experiments revealed that low T cell receptor and CD28 stimulation supported T helper 17 rather than T helper 1 development. Under these conditions CD44 could act as a co-stimulatory molecule and replace CD28. Indeed, rested CD44+++CD4+ T cells contained already more total and especially phosphorylated zeta-chain-associated protein kinase 70 as compared to CD44++ cells. Our results support the notion, that CD44 enhances T cell receptor signaling strength by delivering lymphocyte-specific protein kinase, which is required for induction of IL-17 producing T helper cells.

T helper cell mediated-tolerance towards fetal allograft in successful pregnancy

Trophoblast HLA-C antigens from paternal origins, which liken the trophoblast to a semiallograft, could be presented by the maternal APCs to the specific maternal CD4+ T helper cells, which could release various cytokines in response to these alloantigens. On the basis of the cytokines produced, these cells can be classified in Th1, Th2 and Th17 cells. Th1 and Th17 cells, known to be responsible for acute allograft rejection, could be involved in miscarriage and Th2 cells together with regulatory CD4+ T cells, known to be involved in allograft tolerance, could be responsible, at least in part, for the success of pregnancy. In this review we focus the role effector CD4+ T cells Th1, Th2 and Th17 cells on the fetal allograft tolerance.

Therapeutic Potential of IL-17-Mediated Signaling Pathway in Autoimmune Liver Diseases

Emerging evidence reveals that various cytokines and tissue microenvironments contribute to liver inflammation and autoimmunity, and IL-17 family is one of highlights acknowledged. Although the implication of IL-17 family in most common autoimmune diseases (such as psoriasis, inflammatory bowel disease, and rheumatoid arthritis) has been extensively characterized, the role of this critical family in pathophysiology of autoimmune liver diseases (AILD) still needs to be clarified. In the review, we look into the intriguing biology of IL-17 family and further dissect on the intricate role of IL-17-mediated pathway in AILD. Considering encouraging data from preclinical and clinical trials, IL-17 targeted therapy has shown promises in several certain autoimmune conditions. However, blocking IL-17-mediated pathway is just beginning, and more fully investigation and reflection are required. Taking together, targeting IL-17-mediated responses may open up new areas of potential clinical treatment for AILD.

All-trans retinoid acid promotes allogeneic corneal graft survival in mice by regulating Treg-Th17 balance in the presence of TGF-β

BACKGROUND

All-trans retinoid acid (ATRA) has been proven to skew Regulatory T cell-T helper 17 cell (Treg-Th17) balance toward Treg in vitro, favoring graft acceptance. However, its in vivo effect after solid organ transplantation is under investigation.

RESULTS

BALB/c mice were given orthotopic corneal grafts from C57BL/6 donors, and recipient mice were administered with ATRA, TGF-β, and the combination of both agents for 8 weeks after surgery. We found that a mixed treatment of ATRA and TGF-β significantly promoted graft survival. Moreover, with the presence of TGF-β, ATRA upregulated CD4(+)CD25(+)Foxp3(+)Treg cells and suppressed Th17 cells in the blood, spleen and draining lymph nodes of recipient mice, as well as enhanced the Foxp3 expression and inhibited the RORγt expression in grafts and peripheral blood mononuclear cells (PBMCs). Simultaneously, increased number of Foxp3+ cells and decreased number of IL-17+ cells in conjunctiva were found in recipients with mixed treatment, along with reduced IL-17 level in serum and aqueous humor and increased IL-10 level in aqueous humor. Tregs isolated from recipient mice treated with ATRA + TGF-β presented the strongest suppressive activity in vitro.

CONCLUSIONS

Combined application of ATRA and TGF-β may shift the Th17-Treg balance toward Tregs, hence facilitating the induction of immunological tolerance after allogenic corneal transplantation and representing a potential therapeutic approach in the treatment of posttransplant rejection.

Anti-IL-17 therapy restricts and reverses late-term corneal allorejection

Corneal allograft rejection has been described as a Th1-mediated process involving IFN-γ production. However, recent evidence also implicated IL-17 as being involved in acute corneal allograft responses. Our data support that IL-17 is involved in early acute corneal allograft acceptance. However, we decided to extend these studies to include a later phase of rejection in which there is a peak of IL-17 production that is >15-fold higher than that seen during acute rejection and occurs >45 d postengraftment at the onset of late-term rejection. We demonstrate that neutralizing IL-17A at this time significantly reduced corneal graft rejection. Surprisingly, when corneal grafts that are undergoing this later phase of rejection are treated with anti-IL-17A, there is a reversal of both opacity and neovascularization. Compared with the early phase of rejection, the cellular infiltrate is significantly less, with a greatly reduced presence of Gr-1(+) neutrophils and a relative increase in CD4(+) T cells and macrophages. We went on to identify that the cells expressing IL-17 were CD4(+) IL-17(+) T cells and, somewhat surprisingly, IL-17(+) F4/80(+) macrophages within the rejecting corneal allografts. Taken together, these findings describe a distinct late phase of corneal allograft rejection that is likely mediated by Th17 cells; therapeutic neutralization of IL-17A reverses this rejection. This further suggests that IL-17 might serve as an excellent therapeutic target to reduce this form of corneal allograft rejection.

The ratio of circulating regulatory T cells (Tregs)/Th17 cells is associated with acute allograft rejection in liver transplantation

CD4⁺CD25⁺FoxP3⁺ regulatory T cells (Tregs) and Th17 cells are known to be involved in the alloreactive responses in organ transplantation, but little is known about the relationship between Tregs and Th17 cells in the context of liver alloresponse. Here, we investigated whether the circulating Tregs/Th17 ratio is associated with acute allograft rejection in liver transplantation. In present study, thirty-eight patients who received liver transplant were enrolled. The patients were divided into two groups: acute allograft rejection group (Gr-AR) (n = 16) and stable allograft liver function group (Gr-SF) (n = 22). The frequencies of circulating Tregs and circulating Th17 cells, as well as Tregs/Th17 ratio were determined using flow cytometry. The association between Tregs/Th17 ratio and acute allograft rejection was then analyzed. Our results showed that the frequency of circulating Tregs was significantly decreased, whereas the frequency of circulating Th17 cells was significantly increased in liver allograft recipients who developed acute rejection. Tregs/Th17 ratio had a negative correlation with liver damage indices and the score of rejection activity index (RAI) after liver transplantation. In addition, the percentages of CTLA-4⁺, HLA-DR⁺, Ki67⁺, and IL-10⁺ Tregs were higher in Gr-SF group than in Gr-AR group. Our results suggested that the ratio of circulating Tregs/Th17 cells is associated with acute allograft rejection, thus the ratio may serve as an alternative marker for the diagnosis of acute rejection.

Chimeric anti-IL-17 full-length monoclonal antibody is a novel potential candidate for the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease, primarily manifesting as inflammatory arthritis. It is associated with chronic inflammation of the synovial joints, mostly in the hands and feet, as well as with systemic extra-articular inflammation. The chimeric anti-interleukin (IL)-17 full-length monoclonal antibody (CMa17Aab) targets IL-17A, which is an important cytokine in the pathogenesis of RA and other inflammatory disorders. In this study, we investigated whether CMa17Aab exerts therapeutic effects in a mouse model of type II collagen-induced arthritis (CIA). Mice with CIA were subcutaneously injected with the humanized CMa17Aab antibody. The effects of treatment were assessed by estimating the arthritis severity score, the extent of histological damage and bone destruction, the autoreactive humoral and cellular immune responses and the production of cytokines. Treatment with CMa17Aab exerted beneficial effects in the mice with CIA as regards clinical and histological parameters. Compared with the controls, treatment with CMa17Aab resulted in a significant alleviation of the severity of the symptoms of arthritis, by preventing bone damage and cartilage destruction, reducing humoral and cellular immune responses, and downregulating the expression of IL-6, IL-8, matrix metalloproteinase (MMP)-3, IL-17, IL-1β, tumor necrosis factor (TNF)-α, receptor activator for nuclear factor-κB ligand (RANKL) and interferon (IFN)-γ in inflamed tissues. In conclusion, our study demonstrates that treatment with CMa17Aab exerts beneficial effects in mice with CIA, by preventing joint inflammation, cartilage destruction and bone damage. These preliminary results suggest that CMa17Aab is an important regulator in RA, and that it may represent a novel therapeutic agent that may prove useful in the treatment of this disease.

Evaluation of corneal graft survival in mice model

AIM

To investigate the characteristics and criterion of graft rejection in mice model.

METHODS

C57BL/6 or BALB/c mice corneal grafts were grafted onto BALB/c hosts. Each group was divided into two subgroups according to the corneal opacity scores 12d after transplantation. The characteristics of opacity and neovascularization were observed. Mice of the 12(th), 50(th) day after transplantation, the grafts biopsy of mice in allogeneic group 1, which opacity score exceed 3, were prepared for histological observation and those restore transparent were endothelial stained.

RESULTS

There was no difference of corneal opacity score on the 7(th) and 12(th) day after operation; the histological results had no disparity between syngeneic group and allogeneic group. On the 12(th) day after surgery, the turbidity curve was apparent in grafts with opacity score < 2. Mononuclear cells were shown in grafts with opacity score reached 3 in allogeneic group 1. Different rejection performance was observed in tissue sections on the 50(th) day after surgery.

CONCLUSION

Grafts, opacity score exceeds 3 from the 7(th) to the 12(th) day after operation could not be judged as a rejection. We should pay more attention to the variation of grafts opacity since 12d after corneal transplantation.

Corneal transplantation and immune privilege

Corneal transplants have been successfully performed in human subjects for over 100 years and enjoy an immune privilege that is unrivaled in the field of transplantation. Immune privilege is defined as the reduced incidence and tempo in the immune rejection of corneal allografts compared to other categories of organ allografts performed under the same conditions. Skin allografts transplanted across various MHC or minor histocompatibility barriers undergo rejection in approximately 100% of the hosts. By contrast, orthotopic corneal allografts experience long-term survival in 50% to >90% of the hosts, depending on the histocompatibility barriers that confront the host. The capacity of corneal allografts to evade immune rejection is attributable to multiple anatomical, physiological and immunoregulatory conditions that conspire to prevent the induction and expression of alloimmunity.

Interleukin-17 plays a critical role in the acute rejection of intestinal transplantation

AIM: To investigate the role of interleukin (IL)-17 in small bowel allograft rejection.

METHODS: We detected the expression of helper T cell 17 (Th17) cells in biopsy specimens from 3 cases of living small bowel transplantation in our department through immunofluorescence stain. We then established a rat heterotopic small bowel transplantation model. The rats were sacrificed on the 1^st, 2^nd, 3^rd, 5^th, and 7^th d after small bowel transplantation. The degrees of transplantation rejection in rat intestine graft were examined through hematoxylin eosin (HE) stain, and the expression of Th17 cells in rat intestine graft were detected through immunofluorescence stain. In addition, the recipient rats undergoing intestinal transplantation were administrated with mouse-anti-rat IL-17 monoclonal antibody (mAb), and the survival of rats was analyzed. The recipient rats which received mouse-anti-rat IL-17 mAb treatment were sacrificed on the 1^st, 2^nd, 3^rd, 5^th, and 7^th d after small bowel transplantation. The degrees of transplantation rejection and the expression of Th17 cells in rat intestine graft were detected through HE and immunofluorescence stain. The expression of IL-17, IL-1β, tumor necroses factor receptor-α (TNF-α), IL-6, and IL-8 in the intestine graft or serum were also detected.

RESULTS: The expressions of Th17 cells ran parallel with the degree of acute rejection in human intestine grafts. The intestine graft rejection of rats was aggravated with prolonged duration after intestinal transplantation, and the expressions of Th17 cells were also correlated with the degree of acute rejection in rat intestine grafts. Administration of mouse-anti-rat IL-17 mAb prolonged the survival of rats after small bowel transplantation (P < 0.001). Furthermore, we found that the administration of mouse-anti-rat IL-17 mAb significantly decreased the intensity of CD4⁺IL-17⁺ Th17 cells in intestine grafts on the 2^nd, 3^rd, 5^th, and the 7^th d (97.22 ± 4.05 vs 12.45 ± 2.02 on the 7^th d, P < 0.0001), and suppressed the severity of acute rejection. The expression of IL-17 in the intestine graft declined after mouse-anti-rat IL-17 mAb administration on the 2^nd, 3^rd, 5^th, and the 7^th d (0.88 ± 0.03 vs 0.35 ± 0.02 on the 7^th d, P < 0.0001). We also detected the IL-17 serum level and found that the IL-17 level reduced from the 1^st d to the 7^th d (6.52 ± 0.18 ng/mL vs 2.04 ± 0.15 ng/mL on the 7^th d, P < 0.0001). No significant difference in the level of IL-17 mRNA in the intestine graft was identified between the two groups. The levels of IL-1β, TNF-α, IL-6, and IL-8 mRNA in the intestine graft after the administration of mouse-anti-rat IL-17 mAb were also tested. We found that on the 3^rd, 5^th, and 7^th d after intestinal transplantation, administration of mouse-anti-rat IL-17 mAb significantly inhibited the levels of IL-1β (12.11 ± 1.16 vs 1.27 ± 0.15 on the 7^th d, P < 0.001), TNF-α (27.37 ± 2.60 vs 1.06 ± 0.26 on the 7^th d, P < 0.001), IL-6 (21.43 ± 1.79 vs 1.90 ± 0.32 on the 7^th d, P < 0.001), and IL-8 (20.44 ± 1.44 vs 1.34 ± 0.20 on the 7^th d, P < 0.001) mRNA in the intestine graft.

CONCLUSION: IL-17 may act as a promising and potent target for inhibiting acute rejection after small bowel transplantation.

Corneal Allograft Rejection: Immunopathogenesis to Therapeutics

Corneal transplantation is among the most successful solid organ transplants. However, despite low rejection rates of grafts in the ‘low-risk’ setting, rejection can be as high as 70% when grafted into ‘high-risk’ recipient beds. Under normal homeostatic conditions, the avascular cornea provides a unique environment that facilitates immune and angiogenic privilege. An imbalance in pro-inflammatory, angiogenic and lymphangiogenic mediators leads to a breakdown in corneal immune privilege with a consequent host response against the donor graft. Recent developments in lamellar and endothelial keratoplasties have reduced the rates of graft rejection even more, while providing improved visual outcomes. The corneal layer against which an immune response is initiated, largely determines reversibility of the acute episode. While epithelial and stromal graft rejection may be treated with topical corticosteroids with higher success, acute endothelial rejection mandates a more aggressive approach to therapy due to the lack of regenerative capacity of this layer. However, current immunosuppressive regimens come with the caveat of ocular and systemic side effects, making prolonged aggressive treatment undesirable. With the advent of biologics, efficacious therapies with a superior side effect profile are on the horizon. In our review we discuss the mediators of ocular immune privilege, the roles of cellular and molecular immune players in graft rejection, with a focus on human leukocyte antigen and antigen presenting cells. Furthermore, we discuss the clinical risk factors for graft rejection and compare rates of rejection in lamellar and endothelial keratoplasties to traditional penetrating keratoplasty. Lastly, we present the current and upcoming measures of therapeutic strategies to manage and treat graft rejection, including an overview of biologics and small molecule therapy.

Effects of immunosuppressive agents on Th17 cells involved in transplantation

The lymphocyte-derived helper T (Th) cells are critical regulators of the adaptive immune response and are associated with inflammatory disease. The most recently recognized Th-cell lineage, Th17, plays an important role in host defense against extracellular pathogens by secreting the proinflammatory cytokine, interleukin 17, and recruiting reactive oxygen species (ROS)-producing monocytes to the site of infection. However, accumulating evidence has implicated Th17-cell dysregulation as an underlying cause for some immune-related pathogenic conditions, including allograft rejection. Recent studies of human transplant patients have indicated that Th17 cells exhibit resistance to current immunosuppressive therapies that would otherwise prevent allograft rejection. In this review, we will discuss the most current research findings related to Th17-cell function in various kinds of allografts.

Interleukin-17 causes Rho-kinase-mediated endothelial dysfunction and hypertension

AIMS

Elevated levels of pro-inflammatory cytokine interleukin-17A (IL-17) are associated with hypertensive autoimmune diseases; however, the connection between IL-17 and hypertension is unknown. We hypothesized that IL-17 increases blood pressure by decreasing endothelial nitric oxide production.

METHODS AND RESULTS

Acute treatment of endothelial cells with IL-17 caused a significant increase in phosphorylation of the inhibitory endothelial nitric oxide (NO) synthase residue threonine 495 (eNOS Thr495). Of the kinases known to phosphorylate eNOS Thr495, only inhibition of Rho-kinase prevented the IL-17-induced increase. IL-17 caused a threefold increase in the Rho-kinase activator RhoA, and this was prevented by an IL-17 neutralizing antibody. In isolated mouse aortas, IL-17 significantly increased eNOS Thr495 phosphorylation, induced RhoA expression, and decreased NO-dependent relaxation responses, all of which were prevented by either an IL-17 neutralizing antibody or inhibition of Rho-kinase. In mice, IL-17 treatment for 1 week significantly increased systolic blood pressure and this was associated with decreased aortic NO-dependent relaxation responses, increased eNOS Thr495 phosphorylation, and increased RhoA expression. Inhibition of Rho-kinase prevented the hypertension caused by IL-17.

CONCLUSION

These data demonstrate that IL-17 activates RhoA/Rho-kinase leading to endothelial dysfunction and hypertension. Inhibitors of IL-17 or Rho-kinase may prove useful as anti-hypertensive drugs in IL-17-associated autoimmune diseases.

Increase of peripheral Th17 lymphocytes during acute cellular rejection in liver transplant recipients

BACKGROUND

Although many human inflammatory and autoimmune diseases were previously considered to be mediated by T helper type 1 (Th1) cells, the recently described Th17 cells play dominant roles in several of these diseases. We and others speculated that allograft rejection after organ transplantation may also involve Th17 cells. Episodes of acute rejection occur in 30% of liver transplants. This study aimed to determine the frequency of circulating Th17 cells in patients who had received liver transplants for benign end-stage liver disease and to identify any association between acute rejection episodes and levels of Th17 cells in the peripheral blood.

METHODS

A prospective study compared Th17 cells from 76 consecutive benign end-stage liver disease patients who had undergone orthotopic liver transplantation from 2007 to 2011 with those from 20 age-matched healthy individuals. Peripheral blood samples were collected at different time points within one year after transplant. Blood samples and liver biopsies were also collected at the diagnosis of acute rejection. Percentages of circulating CD4+IL-17+ cells were measured by flow cytometry. The transplant patients were classified into two groups: a rejection group consisting of 17 patients who had an episode of acute rejection, and a non-rejection group comprising the remaining 59 patients with no acute rejection episodes. Percentages of circulating Th17 cells were compared between the two groups and controls.

RESULTS

The levels of circulating CD4+IL-17+ T cells in the rejection group were higher during acute rejection than those in the non-rejection group (2.56+/-0.43% versus 1.79+/-0.44%, P<0.001). The frequency of CD4+IL-17+ cells in peripheral blood was positively correlated with the rejection activity index (r=0.79, P=0.0002).

CONCLUSION

Circulating Th17 cells may be useful as a surrogate marker for predicting acute rejection in liver transplant recipients.

Gamma-irradiation reduces the allogenicity of donor corneas

PURPOSE

To evaluate the utility and allogenicity of gamma-irradiated corneal allografts.

METHODS

Corneal buttons were harvested from C57BL/6 mice and decellularized with gamma irradiation. Cell viability was assessed using TUNEL and viability/cytotoxicity assays. Orthotopic penetrating keratoplasty was performed using irradiated or nonirradiated (freshly excised) C57BL/6 donor grafts and BALB/c or C57BL/6 recipients. Graft opacity was assessed over an 8-week period and graft survival was evaluated using Kaplan-Meier survival curves. Mixed-lymphocyte reactions and delayed-type hypersensitivity assays were performed to evaluate T-cell alloreactivity. Real-time PCR was used to investigate the corneal expression of potentially pathogenic T-helper 1, 2, and 17 cell-associated cytokines.

RESULTS

Corneal cells were devitalized by gamma irradiation as evidenced by widespread cellular apoptosis and plasma membrane disruption. Nonirradiated allograft and isograft rates of survival were superior to irradiated allograft and isograft rates of survival (P < 0.001). Mixed lymphocyte reactions demonstrated that T-cells from irradiated allograft recipients did not exhibit a secondary alloimmune response (P < 0.001). Delayed-type hypersensitivity assays demonstrated that irradiated allografts did not elicit an alloreactive delayed-type hypersensitivity response in graft recipients (P ≤ 0.01). The corneal expression of T-helper 1, 2, and 17 cell-associated cytokines was significantly lower in failed irradiated allografts than rejected nonirradiated allografts (P ≤ 0.001).

CONCLUSIONS

Gamma-irradiated corneas failed to remain optically clear following murine penetrating keratoplasty; however, gamma irradiation reduced the allogenicity of these corneas, potentially supporting their use in procedures such as anterior lamellar keratoplasty or keratoprosthesis implantation.

The imbalance between Treg and Th17 cells caused by FTY720 treatment in skin allograft rejection

OBJECTIVES

FTY720 modulates CD4+T cells by the augmentation of regulatory T cell activity, secretion of suppressive cytokines and suppression of IL-17 secretion by Th17 cells. To further understand the process of graft rejection/acceptance, we evaluated skin allograft survival and associated events after FTY720 treatment.

METHODS

F1 mice (C57BL/6xBALB/c) and C57BL/6 mice were used as donors for and recipients of skin transplantation, respectively. The recipients were transplanted and either not treated or treated with FTY720 by gavage for 21 days to evaluate the allograft survival. In another set of experiments, the immunological evaluation was performed five days post-transplantation. The spleens, axillary lymph nodes and skin allografts of the recipient mice were harvested for phenotyping (flow cytometry), gene expression (real-time PCR) and cytokine (Bio-Plex) analysis.

RESULTS

The FTY720 treatment significantly increased skin allograft survival, reduced the number of cells in the lymph nodes and decreased the percentage of Tregs at this site in the C57BL/6 recipients. Moreover, the treatment reduced the number of graft-infiltrating cells and the percentage of CD4+ graft-infiltrating cells. The cytokine analysis (splenocytes) showed decreased levels of IL-10, IL-6 and IL-17 in the FTY720-treated mice. We also observed a decrease in the IL-10, IL-6 and IL-23 mRNA levels, as well as an increase in the IL-27 mRNA levels, in the splenocytes of the treated group. The FTY720-treated mice exhibited increased mRNA levels of IL-10, IL-27 and IL-23 in the skin graft.

CONCLUSIONS

Our results demonstrated prolonged but not indefinite skin allograft survival by FTY720 treatment. This finding indicates that the drug did not prevent the imbalance between Tr1 and Th17 cells in the graft that led to rejection.

IL-17/IL-17 receptor system in autoimmune disease: mechanisms and therapeutic potential

IL-17 (interleukin-17), a hallmark cytokine of Th17 (T-helper 17) cells, plays critical roles in host defence against bacterial and fungal infections, as well as in the pathogenesis of autoimmune diseases. The present review focuses on current knowledge of the regulation, functional mechanisms and targeting strategies of IL-17 in the context of inflammatory autoimmune diseases. Evidence shows that IL-17 is highly up-regulated at sites of inflammatory tissues of autoimmune diseases and amplifies the inflammation through synergy with other cytokines, such as TNF (tumour necrosis factor) α. Although IL-17 was originally thought to be produced mainly by Th17 cells, a newly defined T-cell subset with a specific differentiation programme and tight regulation, several other cell types (especially innate immune cells) are also found as important sources for IL-17 production. Although IL-17 activates common downstream signalling, including NF-κB (nuclear factor κB), MAPKs (mitogen-activated protein kinases), C/EBPs (CCAAT/enhancer-binding proteins) and mRNA stability, the immediate receptor signalling has been shown to be quite unique and tightly regulated. Mouse genetic studies have demonstrated a critical role for IL-17 in the pathogenesis of variety of inflammatory autoimmune diseases, such as RA (rheumatoid arthritis) and MS (multiple sclerosis). Importantly, promising results have been shown in initial clinical trials of monoclonal antibodies against IL-17 or its receptor (IL-17R) to block IL-17-mediated function in treating autoimmune patients with psoriasis, RA and MS. Therefore targeting IL-17/IL-17R, IL-17-producing pathways or IL-17-mediated signalling pathways can be considered for future therapy in autoimmune diseases.

Interleukin-17 Accelerates Allograft Rejection by Suppressing Regulatory T Cell Expansion

Background—

Interleukin-17 (IL-17), which is predominantly produced by T helper 17 cells distinct from T helper 1 or T helper 2 cells, participates in the pathogenesis of infectious, autoimmune, and allergic disorders. However, the precise role in allograft rejection remains uncertain. In the present study, we investigated the role of IL-17 in acute allograft rejection using IL-17-deficient mice.

Methods and Results—

Donor hearts from FVB mice were heterotopically transplanted into either C57BL/6J-IL-17-deficient (IL-17 − / − ) or -wild-type mice. Allograft survival was significantly prolonged in IL-17 − / − recipient mice due to reduced local inflammation accompanied by decreased inflammatory cell recruitment and cytokine/chemokine expression. IL-17 − / − recipient mice exhibited decreased IL-6 production and reciprocally enhanced regulatory T cell expansion, suggesting a contribution of regulatory T cells to prolonged allograft survival. Indeed, allografts transplanted into anti-CD25 mAb-treated IL-17 − / − recipient mice (regulatory T cell-depleted) developed acute rejection similar to wild-type recipient mice. Surprisingly, we found that gamma delta T cells rather than CD4 + and CD8 + T cells were key IL-17 producers in the allografts. In support, equivalent allograft rejection was observed in Rag-2 −/− recipient mice engrafted with either wild-type or IL-17 − / − CD4 + and CD8 + T cells. Finally, hearts transplanted into gamma delta T cell-deficient mice resulted in decreased allograft rejection compared with wild-type controls.

Conclusions—

During heart transplantation, (1) IL-17 is crucial for acceleration of acute rejection; (2) IL-17-deficiency enhances regulatory T cell expansion; and (3) gamma delta T cells rather than CD4 + and CD8 + T cells are a potential source of IL-17. IL-17 neutralization may provide a potential target for novel therapeutic treatment for cardiac allograft rejection.