CCL-21 conditioned regulatory T cells induce allotolerance through enhanced homing to lymphoid tissue

Biophysical and biochemical aspects of immune cell-tumor microenvironment interactions

The tumor microenvironment (TME), composed of and influenced by a heterogeneous set of cancer cells and an extracellular matrix, plays a crucial role in cancer progression. The biophysical aspects of the TME (namely, its architecture and mechanics) regulate interactions and spatial distributions of cancer cells and immune cells. In this review, we discuss the factors of the TME-notably, the extracellular matrix, as well as tumor and stromal cells-that contribute to a pro-tumor, immunosuppressive response. We then discuss the ways in which cells of the innate and adaptive immune systems respond to tumors from both biochemical and biophysical perspectives, with increased focus on CD8+ and CD4+ T cells. Building upon this information, we turn to immune-based antitumor interventions-specifically, recent biophysical breakthroughs aimed at improving CAR-T cell therapy.

Umbilical cord blood and peripheral blood-derived regulatory T cells therapy: Progress in type 1 diabetes

Regulatory T cells (Tregs) are key regulators for the inflammatory response and play a role in maintaining the immune tolerance. Type 1 diabetes (T1D) is a relatively common autoimmune disease that results from the loss of immune tolerance to β-cell-associated antigens. Preclinical models have demonstrated the safety and efficacy of Tregs given in transplant rejection and autoimmune diseases such as T1D. Adoptive transfer of Tregs has been utilized in clinical trials for over a decade. However, the achievement of the adoptive transfer of Tregs therapy in clinical application remains challenging. In this review, we highlight the characterization of Tregs and compare the differences between umbilical cord blood and adult peripheral blood-derived Tregs. Additionally, we summarize conditional modifications in the expansion of Tregs in clinical trials, especially for the treatment of T1D. Finally, we discuss the existing technical challenges for Tregs in clinical trials for the treatment of T1D.

The impact of donor diabetes on corneal transplant immunity

Corneal transplantation is the most common form of solid tissue grafting, with an approximately 80% to 90% success rate. However, success rates may decline when donor tissues are derived from patients with a history of diabetes mellitus (DM). To evaluate the underlying immunopathologic processes that cause graft rejection, we used streptozotocin-induced type 1 DM (DM1) and transgenic Lepob/ob type 2 DM (DM2) diabetic murine models as donors and nondiabetic BALB/c as recipients. DM resulted in an increased frequency of corneal antigen-presenting cells (APCs) with an acquired immunostimulatory phenotype. Following transplantation, recipients that received either type of diabetic graft showed increased APC migration and T helper type 1 alloreactive cells, impaired functional regulatory T cells, and graft survival. Insulin treatment in streptozotocin-induced diabetic mice led to an increased tolerogenic profile of graft APC, lower T helper type 1 sensitization, and a higher frequency of functional regulatory T cells with high suppressive capacity, reflected in increased graft survival. We conclude that both DM1 and DM2 in donors can impact corneal APC functional phenotype, rendering the tissue more immunogenic and thereby increasing the risk of graft failure.

Rapamycin antagonizes angiogenesis and lymphangiogenesis through myeloid-derived suppressor cells in corneal transplantation

Rapamycin is an immunosuppressive drug that is widely used in the postsurgery management of transplantation. To date, the mechanism by which rapamycin reduces posttransplant neovascularization has not been fully understood. Given the original avascularity and immune privilege of the cornea, corneal transplantation is considered as an ideal model to investigate neovascularization and its effects on allograft rejection. Previously, we found that myeloid-derived suppressor cells (MDSC) prolong corneal allograft survival through suppression of angiogenesis and lymphangiogenesis. Here, we show that depletion of MDSC abolished rapamycin-mediated suppression of neovascularization and elongation of corneal allograft survival. RNA-sequencing analysis revealed that rapamycin dramatically enhanced the expression of arginase 1 (Arg1). Furthermore, an Arg1 inhibitor also completely abolished the rapamycin-mediated beneficial effects after corneal transplantation. Taken together, these findings indicate that MDSC and elevated Arg1 activity are essential for the immunosuppressive and antiangiogenic functions of rapamycin.

Increased activity of lacrimal gland mast cells are associated with corneal epitheliopathy in aged mice

The lacrimal gland undergoes significant structural and functional deterioration with aging. Marked with increased inflammation and fibrosis, the aged lacrimal gland is unable to perform its protective function. As a result, the ocular surface becomes highly susceptible to various ocular surface pathologies, including corneal epitheliopathy. We and others have previously shown that mast cells mediate tissue inflammation by recruiting other immune cells. However, despite their well-known characteristics of secreting various inflammatory mediators, whether mast cells contribute to the immune cell aggregation and activation, and acinar dystrophy of the aged lacrimal gland has not been investigated. Here, we demonstrate the role of mast cells in age-related lacrimal gland pathophysiology using mast cell-deficient (cKitw-sh) mice. Our data demonstrated a significant increase in mast cell frequencies and immune cell infiltration in the lacrimal gland of aged mice. Interestingly, mast cell deficiency resulted in a substantial reduction in inflammation and preservation of lacrimal gland structure, suggesting that mast cells mediate the aging process of the lacrimal gland.

A Novel Murine Model of Endothelial Keratoplasty

PURPOSE

The purpose of this study was to establish a murine model of endothelial keratoplasty.

METHODS

Endothelial keratoplasty (EK) was performed using C57BL/6 donor and BALB/c recipient mice. The central endothelium and Descemet membrane were removed from the recipient cornea, and a 1.5-mm posterior lamellar donor graft was made adherent to the recipient cornea with a small amount of viscoelastic. Mice were followed through slitlamp microscopy postoperatively, and OCT was used to assess the cornea and anterior chamber and measure central corneal thickness. Histology and immunohistochemistry were performed to confirm graft adherence and endothelial cell morphology.

RESULTS

Successfully attached EK grafts were visualized in all transplanted animals. Histology and immunostaining confirmed proper graft orientation and adherence, as well as the presence of donor endothelium on transplanted grafts. We observed maximal corneal edema in all animals at day 1 postoperatively which gradually subsided. EK graft survival was 97% at 8 weeks.

CONCLUSIONS

In this study, we describe a novel murine model for EK which we anticipate will enable detailed investigation into the cellular and molecular mechanisms involved in EK pathobiology.

CC chemokine receptor 7 promotes macrophage recruitment and induces M2-polarization through CC chemokine ligand 19&21 in oral squamous cell carcinoma

PURPOSE

This study aimed to investigate the impact of CC chemokine receptor 7 (CCR7) on the recruitment and polarization of tumor-associated macrophages (TAMs) in oral squamous cell carcinoma (OSCC).

METHODS

We analyzed CCR7 expression pattern, clinicopathological significance, and its association with M2 macrophage infiltration in OSCC by bioinformatic methods. Small interfering RNA (siRNA) was utilized to silence CCR7 in OSCC cells. Conditioned media (CM) was harvested from transfected OSCC cells to establish a co-culture model of THP-1 derived macrophages and OSCC cells. Transwell assay and cell adhesion assay were performed to examine the effect of CCR7 on macrophages recruitment and adhesion. Cytoskeleton was labelled by phalloidin to observe macrophage morphological changes. Moreover, phenotypic alteration of macrophages was measured using quantitative real-time PCR (qRT-PCR), flow cytometry, and immunofluorescence (IF) staining. Ultimately, recombinant human CCL19 and CCL21 were added into the medium of THP-1 derived macrophages to explore their effects on polarization in vitro.

RESULTS

In OSCC patients, the overexpression of CCR7 positively correlated with lymph node metastasis and M2 macrophage infiltration. Macrophage not only exhibited enhanced migration, invasion and adhesion abilities, but also appeared more spindle and branched in vitro when treated with CM from OSCC cells. However, these phenomena were abrogated with knockdown of CCR7. We also discovered that inhibition of CCR7 in OSCC cells suppressed TAMs polarization to an M2 phenotype. In addition, recombinant human CCL19 and CCL21 promoted macrophage M2-polarization in vitro.

CONCLUSION

CCR7 in OSCC cells promoted recruitment and M2-polarization of THP-1 derived macrophages in vitro by regulating production of CCL19 and CCL21.

Mesenchymal stem cells augment regulatory T cell function via CD80-mediated interactions and promote allograft survival

Mesenchymal stem cells (MSCs) and regulatory T cells (Tregs) both have been shown to modulate the alloimmune response and promote transplant survival. Mounting evidence suggests that MSCs augment Treg function, but the mechanisms underlying this phenomenon have not been fully deciphered. Here, we identified that MSCs express substantial levels of CD80 and evaluated its immunoregulatory function using in vivo and in vitro experiments. Our in vitro culture assays demonstrated that MSCs induce expression of FoxP3 in Tregs in a contact-dependent manner, and the blockade of CD80 abrogates this FoxP3 induction and Treg-mediated suppression of T cell proliferation. Moreover, supplementation of soluble CD80 significantly upregulated FoxP3 expression. Using a well-characterized murine model of corneal transplantation, we show that silencing CD80 in MSCs diminishes the capacity of MSCs to promote selective graft infiltration of Tregs, promote FoxP3 expression and upregulate suppressive function of Tregs. Consequently, MSCs, following CD80 knockdown, failed to promote corneal allograft survival.

Regulatory T Cells Exhibit Interleukin-33-Dependent Migratory Behavior during Skin Barrier Disruption

Regulatory T cells (Tregs) suppress immune responses and maintain immunological self-tolerance and homeostasis. We currently investigated relationships between skin barrier condition and Treg behavior using skin barrier-disrupted mice. Skin barrier disruption was induced by repeated topical application of 4% sodium dodecyl sulfate (SDS) on mice. The number of CD4⁺ forkhead box protein P3 (Foxp3)⁺ Tregs was higher in 4% SDS-treated skins than in controls. This increasing was correlated with the degree of acanthosis. The numbers of interleukin (IL)-10⁺ and transforming growth factor (TGF)-β⁺ Tregs also increased in 4% SDS-treated skins. Localization of IL-33 in keratinocytes shifted from nucleus to cytoplasm after skin barrier disruption. Notably, IL-33 promoted the migration of Tregs in chemotaxis assay. The skin infiltration of Tregs was cancelled in IL-33 neutralizing antibody-treated mice and IL-33 knockout mice. Thus, keratinocyte-derived IL-33 may induce Treg migration into barrier-disrupted skin to control the phase transition between healthy and inflammatory conditions.

Inhibition of Orthotopic Genital Cancer Induced by Subcutaneous Administration of Human Papillomavirus Peptide Vaccine with CpG Oligodeoxynucleotides as an Adjuvant in Mice

Purpose

Persistent high-risk human papillomavirus (HPV) infection is the most common cause of cervical cancer and its precursor lesions. Although prophylactic HPV vaccines have been applied in the general population for the prevention of HPV infections, no licensed therapeutic HPV vaccine is currently available to treat preexisting HPV infections or HPV-associated diseases, including cervical cancer.

Materials and Methods

The most common murine cervical cancer model used for the evaluation of the efficacy of a therapeutic HPV vaccine in preclinical studies is the ectopic model, which is established by the subcutaneous inoculation of tumor cells, such as TC-1 cells, into the flank of an animal. We have previously demonstrated the efficacy of a therapeutic HPV peptide vaccine adjuvanted with unmethylated cytosine-phosphate-guanosine oligodeoxynucleotide in the clearance of ectopic subcutaneous tumors in C57BL/6 mice after vaccination. In the current study, we established orthotopic genital tumors by injecting TC-1 cells into the vaginal submucosa close to the cervix and assessed whether the subcutaneous administration of the therapeutic vaccine could inhibit the growth of genital tumors. Additionally, we evaluated the effect of the vaccination on the tumor microenvironment.

Results

The results showed that the vaccination induced an increase in infiltrating CD4+ and CD8+ T cells, a decrease in myeloid-derived suppressor cells and cancer-associated fibroblasts, as well as the differential expression of a panel of cytokines, chemokines, and matrix metalloproteinases within the tumor microenvironment.

Conclusion

The administration of the vaccine resulted in the inhibition of established implanted orthotopic genital tumors by inducing strong antitumor immune responses and reversed tolerogenic local immunosuppression in a mouse model of orthotopic genital cancer.

Topical Adoptive Transfer of Plasmacytoid Dendritic Cells for Corneal Wound Healing

Plasmacytoid dendritic cells (pDCs) are crucial for corneal homeostasis through secretion of various anti-angiogenic molecules and growth factors. Due to its avascular nature, only a limited number of adoptively transferred cells home to the cornea, when administered systemically. In addition, local adoptive transfer of cells poses several challenges and the clinical application of commonly used techniques is limited. Herein, we detail a novel approach for local adoptive transfer of pDCs to the cornea for the treatment of corneal wounds. This approach utilizes a commonly used fibrin sealant as a means of transferring previously isolated cells locally on the cornea. The technique is simple, reproducible, and is accompanied with successful transfer and integration of a substantial number of the cells to the cornea. Application of this approach to transfer pDCs promotes corneal wound healing. Furthermore, this technique can be applied for adoptive transfer of any cell of interest to the cornea.

Spatiotemporal in vivo tracking of polyclonal human regulatory T cells (Tregs) reveals a role for innate immune cells in Treg transplant recruitment

Regulatory T cells (Tregs) are emerging as a new cell-based therapy in solid organ transplantation. Adoptive transfer of Tregs has been shown preclinically to protect from graft rejection, and the safety of Treg therapy has been demonstrated in clinical trials. Despite these successes, the in vivo distribution and persistence of adoptively transferred Tregs remained elusive, which hampers clinical translation. Here we isolated human Tregs using a GMP-compatible protocol and lentivirally transduced them with the human sodium iodide symporter to render them traceable in vivo by radionuclide imaging. Engineered human Tregs were characterized for phenotype, survival, suppressive capacity, and reporter function. To study their trafficking behavior, they were subsequently administered to humanized mice with human skin transplants. Traceable Tregs were quantified in skin grafts by non-invasive nano-single-photon emission computed tomography (nanoSPECT)/computed tomography (CT) for up to 40 days, and the results were validated ex vivo. Using this approach, we demonstrated that Treg trafficking to skin grafts was regulated by the presence of recipient Gr-1+ innate immune cells. We demonstrated the utility of radionuclide reporter gene-afforded quantitative Treg in vivo tracking, addressing a fundamental need in Treg therapy development and offering a clinically compatible methodology for future Treg therapy imaging in humans.

IL-33 drives the production of mouse regulatory T cells with enhanced in vivo suppressive activity in skin transplantation

Regulatory T cells (Tregs) are crucial mediators of immune homeostasis with the ability to modulate allogeneic response and control transplant rejection. Although Treg-based cell therapies have shown immense promise, methods to optimize current strategies are critical for successful implementation within the clinic. IL-33 is a cytokine with pleiotropic properties and effects on Treg function and development. In this study, we explored the unique properties of Treg populations activated through the IL-33/ST2 pathway, aiming to exploit their tolerogenic properties for cell therapy. We show that treatment with exogenous IL-33 results in a generalized downregulation of genes critical to T cell biology together with an upregulation of Treg-associated genes. Tregs that develop in response to IL-33 upregulate critical Treg-associated markers, yet without developing enhanced in vitro suppressive capacity. Conversely, these Tregs display potent regulatory activity in vivo, promoting long-term skin allograft survival in a stringent transplantation model. Detailed transcriptomic and immunophenotypic analyses of IL-33-expanded Tregs reveal an enhancement in graft-homing chemokine receptors, which may be partly responsible for their superior in vivo activity that is not reflected in vitro. IL-33 treatment is therefore an attractive adjunctive strategy for patients receiving Treg cell therapeutics.

Exacerbation of AMD Phenotype in Lasered CNV Murine Model by Dysbiotic Oral Pathogens

Emerging evidence underscores an association between age-related macular degeneration (AMD) and periodontal disease (PD), yet the biological basis of this linkage and the specific role of oral dysbiosis caused by PD in AMD pathophysiology remains unclear. Furthermore, a simple reproducible model that emulates characteristics of both AMD and PD has been lacking. Hence, we established a novel AMD+PD murine model to decipher the potential role of oral infection (ligature-enhanced) with the keystone periodontal pathogen Porphyromonas gingivalis, in the progression of neovasculogenesis in a laser-induced choroidal-neovascularization (Li-CNV) mouse retina. By a combination of fundus photography, optical coherence tomography, and fluorescein angiography, we documented inflammatory drusen-like lesions, reduced retinal thickness, and increased vascular leakage in AMD+PD mice retinae. H&E further confirmed a significant reduction of retinal thickness and subretinal drusen-like deposits. Immunofluorescence microscopy revealed significant induction of choroidal/retinal vasculogenesis in AMD+PD mice. qPCR identified increased expression of oxidative-stress, angiogenesis, pro-inflammatory mediators, whereas antioxidants and anti-inflammatory genes in AMD+PD mice retinae were notably decreased. Through qPCR, we detected Pg and its fimbrial 16s-RrNA gene expression in the AMD+PD mice retinae. To sum-up, this is the first in vivo study signifying a role of periodontal infection in augmentation of AMD phenotype, with the aid of a pioneering AMD+PD murine model established in our laboratory.

Ex vivo expansion of regulatory T cells from long-term Belatacept-treated kidney transplant patients restores their phenotype and suppressive function but not their FOXP3 TSDR demethylation status

We recently reported that Tregs from long-term Belatacept-treated kidney transplant patients displayed an altered phenotype and impaired suppressive function compared to Tregs from healthy controls. However, it remains unknown whether ex vivo expansion of Tregs from patients who underwent long-term immunosuppression may be feasible to be used in their treatment. In this work, Tregs from Belatacept-treated patients were polyclonally expanded in vitro in the presence of rapamycin and IL-2. After four weeks of expansion, Tregs from patients expressed high levels of FOXP3, CD25, CTLA-4, Helios and CCR7, and showed strong suppressive activity, even in the presence of pro-inflammatory cytokines. However, FOXP3 TSDR demethylation remained lower in expanded Tregs from Belatacept-treated patients compared to healthy control Tregs. These data suggest that ex vivo expansion of Tregs from patients undergoing long-term immunosuppression may require the use of epigenetic modifying agents to stabilize FOXP3 expression to be considered as treatment in kidney transplant patients.

Regulatory T cells promote corneal endothelial cell survival following transplantation via interleukin-10

The functional competence of corneal endothelial cells (CEnCs) is critical for survival of corneal allografts, but these cells are often targets of the immune response mediated by graft-attacking effector T cells. Although regulatory T cells (Tregs) have been studied for their role in regulating the host's alloimmune response towards the graft, the cytoprotective function of these cells on CEnCs has not been investigated. The aim of this study was to determine whether Tregs suppress effector T cell-mediated and inflammatory cytokine-induced CEnC death, and to elucidate the mechanism by which this cytoprotection occurs. Using 2 well-established models of corneal transplantation (low-risk and high-risk models), we show that Tregs derived from low-risk graft recipients have a superior capacity in protecting CEnCs against effector T cell-mediated and interferon-γ and tumor necrosis factor-α-induced cell death compared to Tregs derived from high-risk hosts. We further demonstrate that the cytoprotective function of Tregs derived from low-risk hosts occurs independently of direct cell-cell contact and is mediated by the immunoregulatory cytokine IL-10. Our study is the first to report that Tregs provide cytoprotection for CEnCs through secretion of IL-10, indicating potentially novel therapeutic targets for enhancing CEnC survival following corneal transplantation.

Mesenchymal Stromal Cells Modulate Corneal Alloimmunity via Secretion of Hepatocyte Growth Factor

Mesenchymal stromal cells (MSCs) are multipotent stem cells that participate in tissue repair and possess considerable immunomodulatory potential. MSCs have been shown to promote allograft survival, yet the mechanisms behind this phenomenon have not been fully defined. Here, we investigate the capacity of MSCs to suppress the allogeneic immune response by secreting the pleiotropic molecule hepatocyte growth factor (HGF). Using an in vivo mouse model of corneal transplantation, we report that MSCs promote graft survival in an HGF‐dependent manner. Moreover, our data indicate that topically administered recombinant HGF (a) suppresses antigen‐presenting cell maturation in draining lymphoid tissue, (b) limits T‐helper type‐1 cell generation, (c) decreases inflammatory cell infiltration into grafted tissue, and (d) is itself sufficient to promote transplant survival. These findings have potential translational implications for the development of HGF‐based therapeutics. stem cells translational medicine2019;8:1030–1040

Local Delivery of Regulatory T Cells Promotes Corneal Allograft Survival

BACKGROUND

Regulatory T (Treg) cell-based immunotherapies have been studied as potential cell-based modalities for promoting transplant survival. However, the efficacy of local delivery of Treg cells in corneal transplantation has not been fully elucidated. Herein, we investigated the kinetics of migration of subconjunctivally injected Treg cells and their role in promoting corneal allograft survival.

METHODS

GFPCD4CD25Foxp3 Treg cells were isolated from draining lymph nodes (DLNs) of GFP transgenic mice and were subconjunctivally injected to corneal allograft recipients. Next, Treg cells, conventional T cells (Tconv) or a combination of both was locally injected to graft recipients, and graft survival was determined by evaluating opacity scores for 10 weeks. Transplanted mice without treatment served as controls. The frequencies of major histocompatibility complex-IICD11b antigen-presenting cells, IFNγCD4 Th1 cells, and CD45 cells in the DLNs and cornea were evaluated at week 2 posttransplantation using flow cytometry. Expressions of IFNγ, IL-10 and TGF-β in the grafts were assessed using reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay.

RESULTS

GFP Treg cells were detected in the ipsilateral cornea and DLNs of recipients 6 hours after injection. Subconjunctival injection of Treg cells significantly decreased the frequencies of mature antigen-presenting cells in the graft and DLNs, suppressed Th1 frequencies in DLNs, and inhibited CD45 cell infiltration to the graft. Finally, locally delivered Treg cells significantly reduced the expression of IFN-γ, enhanced the levels of IL-10 and TGF-β in the graft, and promoted long-term allograft survival.

CONCLUSIONS

Our study elucidates the kinetics of migration of locally delivered Treg cells and shows their role in suppressing host immune response against the allograft.

Chimeric antigen receptor-engineered regulatory T lymphocytes: promise for immunotherapy of autoimmune disease

Regulatory T lymphocytes (Tregs) exist as natural ideal immunosuppressors in the immune system. Autologous or allogeneic Treg transfusion therapy has been carried out in animal models and humans as a new strategy for treating autoimmune disease. Recent studies have shown that Tregs can be engineered with chimeric antigen receptors to be antigen-specific, which are more effective than polyclonal Tregs with fewer target limitations and a lack of major histocompatibility complex restriction. This review describes the potential for applying chimeric antigen receptor-engineered regulatory T cells in autoimmune diseases.

Mast cells contribute to the induction of ocular mucosal alloimmunity

Beyond their historical role as the effector cells in allergic disorders, mast cells have been implicated in regulating both innate and adaptive immune responses. Possessing considerable functional plasticity, mast cells are abundant at mucosal surfaces, where the host and external environments interface. The purpose of this study was to evaluate the contribution of mast cells to allograft rejection at the ocular surface. Using a well-characterized murine model of corneal transplantation, we report that mast cells promote allosensitization. Our data show mast cell frequencies and activation are increased following transplantation. We demonstrate that mast cell inhibition (a) limits the infiltration of inflammatory cells and APC maturation at the graft site; (b) reduces allosensitization and the generation of Th1 cells in draining lymphoid tissues; (c) decreases graft infiltration of alloimmune-inflammatory cells; and (d) prolongs allograft survival. Our data demonstrate a novel function of mast cells in promoting allosensitization at the ocular surface.

Regulatory T cell modulation of cytokine and cellular networks in corneal graft rejection

PURPOSE OF REVIEW

Corneal allografts placed in vascularized or inflamed host beds are at increased risk of graft rejection due to the preponderance of activated immune cells in the host bed. Regulatory T cells (Tregs) are master regulators of the adaptive immune response and play a key role in the induction of immune tolerance. The aim of this review is to discuss mechanisms through which Tregs mediate tolerance in corneal transplantation and the novel therapeutic approaches that target Tregs to promote transplant survival.

RECENT FINDINGS

The inflammatory environment of high-risk allografts not only promotes activation of effector T cells and their infiltration to graft site, but also impairs Treg immunomodulatory function. Recent studies have shown that expansion of Tregs and enhancing their modulatory function significantly improve graft survival.

SUMMARY

As our understanding of the cellular and molecular pathways in corneal transplantation has deepened, novel therapeutic strategies have been developed to improve allograft survival. In this review, we discuss therapeutic approaches that focus on Tregs to promote corneal allograft survival.

Bioimaging of alloantigen-stimulated regulatory T cells in rat vascularized composite allotransplantation

Background

Tipping the balance toward regulatory T cells (Tregs) through adoptive cell therapy has shown promise to induce transplantation tolerance. Although such strategy has been explored in many mice organ transplantation studies, less knowledge was available in rat systems. Furthermore, the behaviors of the transferred cells have not been well studied in real-time fashion.

Methods

Tregs from naïve LEW rats were purified in two steps with the autoMACS system. Immunosuppression potential of these cells was examined with mixed lymphocyte reaction. Following stimulation by the alloantigen in vitro, the purified Tregs were infused into the recipients of vascularized composite allotransplantation (VCA). Secondary allogeneic skin grafting challenge was performed on the recipients with long-term survived VCA. Live optical imaging was performed to track luciferase-expressing Tregs following infusion to the VCA recipients. Expression of relevant molecules was studied by flow cytometry or quantitative RT-PCR.

Results

Rat Tregs were enriched following two-step cell sorting and showed immunosuppressive capacity. Upon infusion into the VCA recipients that have been treated with antilymphocyte serum and short-term Cyclosporin A, the antigen-stimulated Tregs significantly prolonged VCA survival and induced donor-specific tolerance. Tracking of the infused bioluminescent Tregs showed their specific homing to lymph nodes, and then to the VCAs. Following secondary skin grafting, Tregs specifically gathered at the donor-derived skin that was not rejected by the recipient. The in vivo migratory pattern coincided with the altered expression of cell surface molecules of CD62L, CD103, CD134, and CD278, following donor-antigen stimulation. Elevated expression of CCR4 and CCL22 in allograft may also participate in recruiting Tregs for maintenance of VCA survival and promoting donor-specific tolerance.

Conclusion

Sorted Tregs induced donor-specific tolerance to VCA in rats. Live cell tracking demonstrated that activated CD4⁺CD25⁺FoxP3⁺ Tregs targeted primarily to the lymph nodes and VCA. The Tregs migrated to the secondary grafted donor skin and contributed to the maintenance of donor-specific tolerance. These behaviors were associated with phenotypic changes induced by donor antigen stimulation. Increased expression of CCR4 and CCL22 in VCA skin may also be relevant.

Effect of TGF-β1 on blood CD4+CD25high regulatory T cell proliferation and Foxp3 expression during non-small cell lung cancer blood metastasis

Metastatic circulating tumor cells in non-small cell lung cancer (NSCLC) metastasis have been reported to be associated with an immune response. The present study aimed to provide a theoretical basis for the immunomodulatory processes during NSCLC blood metastasis. NSCLC blood and normal peripheral blood mononuclear cells (PBMCs) were collected. The quantity of cluster of differentiation (CD)4⁺CD25^high regulatory T (Treg) cells and the intracellular forkhead box protein 3 (Foxp3) expression in CD4⁺CD25^high Treg cells were determined by flow cytometry. Furthermore, the effect of transforming growth factor β1 (TGF-β1) on NSCLC blood CD4⁺CD25⁺ Treg cell proliferation was explored by activating blood mononuclear cells with an anti-CD3 monoclonal antibody, interleukin-2 and different doses of TGF-β1. Reverse transcription-quantitative polymerase chain reaction assays were used to detect the mRNA expression of Foxp3. Carboxyfluorescein succinimidyl ester staining was used to analyze the proliferation dynamics of lymphocyte subsets. Results indicate that the proportion of CD4⁺ T cells in the blood of patients with NSCLC was significantly higher compared with normal peripheral blood (P<0.01). Foxp3 expression in NSCLC blood Treg cells was significantly decreased compared with normal peripheral blood (P<0.01). NSCLC blood mononuclear cells treated with TGF-β1 at 1, 5 and 25 ng/ml significantly induced Foxp3 expression in CD4⁺CD25⁺ Treg cells compared with the control group (P<0.05). The proportion of CD4⁺CD25⁺ Treg and CD8⁺ T cells were elevated in generation 6, 7, 8 after 6 days of TGF-β1 treatment compared with untreated cells. The proportion of CD4⁺CD25⁺ Treg and CD8⁺ T cells were elevated in generation 8, 9 and with TGF-β1 treatment after 8 days compared with untreated cells. These results indicate that CD4⁺CD25⁺ Treg cells proliferate at a greater rate compared with CD8⁺ T cells after 4, 6 or 8 days of treatment. The proportion of CD4⁺CD25^high Treg cells in NSCLC blood was significantly higher (P<0.05) compared with normal peripheral blood. The number of Foxp3⁺ T cells was significantly lower (P<0.05) compared with normal peripheral blood. The data presented in this study suggest that NSCLC blood CD4⁺CD25^high Treg cells are functionally immature and that TGF-β1 may promote maturation.

Therapeutic approaches for induction of tolerance and immune quiescence in corneal allotransplantation

The cornea is the most commonly transplanted tissue in the body. Corneal grafts in low-risk recipients enjoy high success rates, yet over 50% of high-risk grafts (with inflamed and vascularized host beds) are rejected. As our understanding of the cellular and molecular pathways that mediate rejection has deepened, a number of novel therapeutic strategies have been unveiled. This manuscript reviews therapeutic approaches to promote corneal transplant survival through targeting (1) corneal lymphangiogenesis and hemangiogenesis, (2) antigen presenting cells, (3) effector and regulatory T cells, and (4) mesenchymal stem cells.

Monitoring Cell Proliferation by Dye Dilution: Considerations for Probe Selection

In the third edition of this series, we described protocols for labeling cell populations with tracking dyes, and addressed issues to be considered when combining two different tracking dyes with other phenotypic and viability probes for the assessment of cytotoxic effector activity and regulatory T cell functions. We summarized key characteristics of and differences between general protein and membrane labeling dyes, discussed determination of optimal staining concentrations, and provided detailed labeling protocols for both dye types. Examples of the advantages of two-color cell tracking were provided in the form of protocols for: (a) independent enumeration of viable effector and target cells in a direct cytotoxicity assay; and (b) an in vitro suppression assay for simultaneous proliferation monitoring of effector and regulatory T cells.The number of commercially available fluorescent cell tracking dyes has expanded significantly since the last edition, with new suppliers and/or new spectral properties being added at least annually. In this fourth edition, we describe evaluations to be performed by the supplier and/or user when characterizing a new cell tracking dye and by the user when selecting one for use in multicolor proliferation monitoring. These include methods for: (a) Assessment of the dye's spectral profile on the laboratory's flow cytometer(s) to optimize compatibility with other employed fluorochromes and minimize compensation problems; (b) Evaluating the effect of labeling on cell growth rate;

Virologic and Immunologic Characteristics in Mature Ducks with Acute Duck Hepatitis A Virus 1 Infection

Duck hepatitis A virus 1 (DHAV-1) infection in mature ducks has previously been proposed as a small-animal model for human hepatitis A. However, basic research on the outcome of DHAV-1 infection in mature ducks is limited. Here, we examined the course of viremia, the characteristics of antibody responses, and the profiles of plasma cytokines in mature ducks infected with DHAV-1. During the course of infection, the viremia was detectable soon after infection and persisted for 196 days, however, the ducks presented as clinically asymptomatic. Specific and timely immunoglobulin G (IgG), IgM, and IgA1 responses were elicited. At the same time, extensive inhibition of viral replication was observed with increasing IgG concentration. With respect to pattern-recognition receptors, TLR-7 was mainly involved in triggering the innate defense against the DHAV-1 infection. In addition, plasma immune analytes were measured and were determined to have bidirectional roles in virus clearance. It was concluded that DHAV-1 spreads quickly in blood. The spontaneous clearance of DHAV-1 during asymptomatic infection in mature ducks depends on the cooperation of timely antibody responses and alert innate immune responses. Moreover, the delayed clearance may be associated with a weak interferon-γ-producing CD8+ T cell response. This study allows us to reveal the mechanism of clearance and persistence of DHAV-1 infection in mature ducks. We anticipate that it will provide a basis for future studies focused on defining the nature mechanisms involved in the clearance and persistence of human hepatitis virus.

Harnessing Advances in T Regulatory Cell Biology for Cellular Therapy in Transplantation

Cellular therapy with CD4FOXP3 T regulatory (Treg) cells is a promising strategy to induce tolerance after solid-organ transplantation or prevent graft-versus-host disease after transfer of hematopoietic stem cells. Treg cells currently used in clinical trials are either polyclonal, donor- or antigen-specific. Aside from variations in isolation and expansion protocols, however, most therapeutic Treg cell-based products are much alike. Ongoing basic science work has provided considerable new insight into multiple facets of Treg cell biology, including their stability, homing, and functional specialization; integrating these basic science discoveries with clinical efforts will support the development of next-generation therapeutic Treg cells with enhanced efficacy. In this review, we summarize recent advances in knowledge of how Treg cells home to lymphoid and peripheral tissues, and control antibody production and tissue repair. We also discuss newly appreciated pathways that modulate context-specific Treg cell function and stability. Strategies to improve and tailor Treg cells for cell therapy to induce transplantation tolerance are highlighted.

Alterations of CCR5 and CCR7 expression on donor peripheral blood T cell subsets after mobilization with rhG-CSF correlate with acute graft-versus-host disease

To investigate the effects of recombinant human granulocyte colony-stimulating factor (rhG-CSF) on chemokine receptors and explore the potential mechanism of rhG-CSF inducing immune tolerance, ninety-seven donor and recipient pairs undergoing family-donor allogeneic hematopoietic stem cell transplantation were studied. The results indicated that different donors showed great disparities in expression changes after mobilization. Multivariate analysis revealed that both HLA mismatching and CCR7 downregulation on donors' CD4+ T cells after mobilization were independent risk factors for acute graft-versus-host disease (GVHD). In contrast, CCR5 downregulation on CD4+ T cells was associated with reduced incidence of acute GVHD. In conclusion, rhG-CSF mobilization could lead to differential regulation of chemokine receptors expression on T cell subsets in different donors. Downregulation of CCR5 and upregulation of CCR7 expression on donor CD4+ T cells might protect recipients from acute GVHD. This finding may provide a promising new strategy for the prevention and treatment of acute GVHD.

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.

Review: The function of regulatory T cells at the ocular surface

Regulatory T cells (Tregs) are critical modulators of immune homeostasis. Tregs maintain peripheral tolerance to self-antigens, thereby preventing autoimmune disease. Furthermore, Tregs suppress excessive immune responses deleterious to the host. Recent research has deepened our understanding of how Tregs function at the ocular surface. This manuscript describes the classification, the immunosuppressive mechanisms, and the phenotypic plasticity of Tregs. We review the contribution of Tregs to ocular surface autoimmune disease, as well as the function of Tregs in allergy and infection at the ocular surface. Finally, we review the role of Tregs in promoting allotolerance in corneal transplantation.

Effector and Regulatory T Cell Trafficking in Corneal Allograft Rejection

Corneal transplantation is among the most prevalent and successful forms of solid tissue transplantation in humans. Failure of corneal allograft is mainly due to immune-mediated destruction of the graft, a complex and highly coordinated process that involves elaborate interactions between cells of innate and adaptive immunity. The migration of immune cells to regional lymphoid tissues and to the site of graft plays a central role in the immunopathogenesis of graft rejection. Intricate interactions between adhesion molecules and their counter receptors on immune cells in conjunction with tissue-specific chemokines guide the trafficking of these cells to the draining lymph nodes and ultimately to the site of graft. In this review, we discuss the cascade of chemokines and adhesion molecules that mediate the trafficking of effector and regulatory T cells during corneal allograft rejection.

Type 1 diabetes immunotherapy using polyclonal regulatory T cells

Type 1 diabetes (T1D) is an autoimmune disease that occurs in genetically susceptible individuals. Regulatory T cells (Tregs) have been shown to be defective in the autoimmune disease setting. Thus, efforts to repair or replace Tregs in T1D may reverse autoimmunity and protect the remaining insulin-producing β cells. On the basis of this premise, a robust technique has been developed to isolate and expand Tregs from patients with T1D. The expanded Tregs retained their T cell receptor diversity and demonstrated enhanced functional activity. We report on a phase 1 trial to assess safety of Treg adoptive immunotherapy in T1D. Fourteen adult subjects with T1D, in four dosing cohorts, received ex vivo-expanded autologous CD4(+)CD127(lo/-)CD25(+) polyclonal Tregs (0.05 × 10(8) to 26 × 10(8) cells). A subset of the adoptively transferred Tregs was long-lived, with up to 25% of the peak level remaining in the circulation at 1 year after transfer. Immune studies showed transient increases in Tregs in recipients and retained a broad Treg FOXP3(+)CD4(+)CD25(hi)CD127(lo) phenotype long-term. There were no infusion reactions or cell therapy-related high-grade adverse events. C-peptide levels persisted out to 2+ years after transfer in several individuals. These results support the development of a phase 2 trial to test efficacy of the Treg therapy.

Chemoattractant Signals and Adhesion Molecules Promoting Human Regulatory T Cell Recruitment to Porcine Endothelium

BACKGROUND

Human CD4+CD25+Foxp3+ T regulatory cells (huTreg) suppress CD4+ T cell-mediated antipig xenogeneic responses in vitro and might therefore be used to induce xenograft tolerance. The present study investigated the role of the adhesion molecules, their porcine ligands, and the chemoattractant factors that may promote the recruitment of huTreg to porcine aortic endothelial cells (PAEC) and their capacity to regulate antiporcine natural killer (NK) cell responses.

METHODS

Interactions between ex vivo expanded huTreg and PAEC were studied by static chemotaxis assays and flow-based adhesion and transmigration assays. In addition, the suppressive function of huTreg on human antiporcine NK cell responses was analyzed.

RESULTS

The TNFα-activated PAEC released factors that induce huTreg chemotaxis, partially inhibited by antihuman CXCR3 blocking antibodies. Coating of PAEC with human CCL17 significantly increased the transmigration of CCR4+ huTreg under physiological shear stress. Under static conditions, transendothelial Treg migration was inhibited by blocking integrin sub-units (CD18, CD49d) on huTreg, or their respective porcine ligands intercellular adhesion molecule 2 (CD102) and vascular cell adhesion molecule 1 (CD106). Finally, huTreg partially suppressed xenogeneic human NK cell adhesion, NK cytotoxicity and degranulation (CD107 expression) against PAEC; however, this inhibition was modest, and there was no significant change in the production of IFNγ.

CONCLUSIONS

Recruitment of huTreg to porcine endothelium depends on particular chemokine receptors (CXCR3, CCR4) and integrins (CD18 and CD49d) and was increased by CCL17 coating. These results will help to develop new strategies to enhance the recruitment of host huTreg to xenogeneic grafts to regulate cell-mediated xenograft rejection including NK cell responses.

Graft Site Microenvironment Determines Dendritic Cell Trafficking Through the CCR7-CCL19/21 Axis

PURPOSE

The graft site microenvironment has a profound effect on alloimmunity and graft survival. We aimed to study the kinetics and phenotype of trafficking antigen-presenting cells (APC) to the draining lymph nodes (DLNs) in a mouse model of corneal transplantation, and to evaluate the homing mechanisms through which graft site inflammation controls APC trafficking.

METHODS

Allogeneic donor corneas were transplanted onto inflamed or quiescent graft beds. Host- (YAe+) and donor (CD45.1+ or eGFP+)-derived APCs were analyzed by flow cytometry. Protein and mRNA expression of the CC chemokine receptor (CCR)7 ligands CCL19 and CCL21 were assessed using ELISA and Real-Time qPCR, respectively. Transwell migration assay was performed to assess the effect of DLNs isolated from hosts with inflamed graft beds on mature bone marrow-derived dendritic cells (BMDCs).

RESULTS

We found that inflamed graft sites greatly promote the trafficking of both recipient- and graft-derived APCs, in particular mature CCR7+ CD11c+ dendritic cells (DC). CCL19 and CCL21 were expressed at significantly higher levels in the DLNs of recipients with inflamed graft beds. The supernatant of DLNs from recipients with inflamed graft beds induced a marked increase in mature DC migration compared with supernatant from recipients with quiescent graft beds in a transwell assay. This effect was abolished by neutralizing CCL19 or CCL21. These data suggest that graft site inflammation increases the expression of CCR7 ligands in the DLNs, which promote mature DC homing and allorejection.

CONCLUSIONS

We conclude that the graft site microenvironment plays a critical role in alloimmunity by determining DC trafficking through the CCR7-CCL19/21 axis.

VEGF-trap aflibercept significantly improves long-term graft survival in high-risk corneal transplantation

BACKGROUND

Graft failure because of immune rejection remains a significant problem in organ transplantation, and lymphatic and blood vessels are important components of the afferent and efferent arms of the host alloimmune response, respectively. We compare the effect of antihemangiogenic and antilymphangiogenic therapies on alloimmunity and graft survival in a murine model of high-risk corneal transplantation.

METHODS

Orthotopic corneal transplantation was performed in hemevascularized and lymph-vascularized high-risk host beds, and graft recipients received subconjunctival vascular endothelial growth factor (VEGF)-trap, anti-VEGF-C, sVEGFR-3, or no treatment, beginning at the time of surgery. Fourteen days after transplantation, graft hemeangiogenesis and lymphangiogenesis were evaluated by immunohistochemistry. The frequencies of Th1 cells in regional lymphoid tissue and graft-infiltrating immune cells were evaluated by flow cytometry. Long-term allograft survival was compared using Kaplan-Meier curves.

RESULTS

VEGF-trap significantly decreased graft hemangiogenesis as compared to the control group and was most effective in reducing the frequency of graft-infiltrating immune cells. Anti-VEGF-C and sVEGFR3 significantly decreased graft lymphangiogenesis and lymphoid Th1 cell frequencies as compared to control. VEGF-trap (72%), anti-VEGF-C (25%), and sVEGFR-3 (11%) all significantly improved in the 8-week graft survival compared to control (0%), although VEGF-trap was significantly more effective than both anti-VEGF-C (P < 0.05) and sVEGFR-3 (P < 0.05).

CONCLUSION

In a clinically relevant model of high-risk corneal transplantation in which blood and lymphatic vessels are present and treatment begins at the time of transplantation, VEGF-trap is significantly more effective in improving long-term graft survival as compared to anti-VEGF-C and sVEGFR-3, but all approaches improve survival when compared to untreated control.

CCR7 expressing mesenchymal stem cells potently inhibit graft-versus-host disease by spoiling the fourth supplemental Billingham's tenet

The clinical acute graft-versus-host disease (GvHD)-therapy of mesenchymal stem cells (MSCs) is not as satisfactory as expected. Secondary lymphoid organs (SLOs) are the major niches serve to initiate immune responses or induce tolerance. Our previous study showed that CCR7 guide murine MSC line C3H10T1/2 migrating to SLOs. In this study, CCR7 gene was engineered into murine MSCs by lentivirus transfection system (MSCs/CCR7). The immunomodulatory mechanism of MSCs/CCR7 was further investigated. Provoked by inflammatory cytokines, MSCs/CCR7 increased the secretion of nitric oxide and calmed down the T cell immune response in vitro. Immunofluorescent staining results showed that transfused MSCs/CCR7 can migrate to and relocate at the appropriate T cell-rich zones within SLOs in vivo. MSCs/CCR7 displayed enhanced effect in prolonging the survival and alleviating the clinical scores of the GvHD mice than normal MSCs. Owing to the critical relocation sites, MSCs/CCR7 co-infusion potently made the T cells in SLOs more naïve like, thus control T cells trafficking from SLOs to the target organs. Through spoiling the fourth supplemental Billingham’s tenet, MSCs/CCR7 potently inhibited the development of GvHD. The study here provides a novel therapeutic strategy of MSCs/CCR7 infusion at a low dosage to give potent immunomodulatory effect for clinical immune disease therapy.

Quantification of allospecific and nonspecific corneal endothelial cell damage after corneal transplantation

PURPOSE

To investigate the effect of host immunity (allospecific) and surgical manipulation (non-allospecific) on corneal endothelial cells (CECs) in corneal transplantation.

METHODS

Draining lymph nodes and grafted C57BL/6 corneas were harvested from syngeneic recipients, allograft acceptors, and allograft rejectors (BALB/c) 1, 3, and 8 weeks after transplantation. We analyzed CEC apoptosis using an ex vivo cornea-in-the-cup assay, and visualized cell-to-cell junctions using immunohistochemical staining (ZO-1). Automatic cell analysis using Confoscan software was used to measure CEC density as well as changes in CEC morphology by quantifying the coefficient of variation in cell size (polymegethism) and shape (pleomorphism).

RESULTS

The cornea-in-the-cup assay showed that allogeneic acceptor T cells and to an even greater extent rejector T cells (but not syngeneic T cells) induced CEC apoptosis. CEC density after corneal transplantation was significantly reduced in allogeneic acceptors compared with syngeneic grafts (P<0.001), and CEC density was even further reduced in the allo-rejector group compared with the allo-acceptor group. Allogeneic grafts showed a greater increase in the coefficient of variation in cell size (polymegethism) when compared with syngeneic grafts 1 week after transplantation (P=P<0.001). However, pleomorphism was not significantly different between syngeneic and allo-acceptor grafts, indicating that polymegethism (but not pleomorphism or cell density) is a sensitive indicator of the effect of alloimmunity on CECs.

CONCLUSIONS

Our data demonstrate that host alloimmunity rather than surgical manipulation alone is the major cause of CEC damage in corneal transplantation, and such morphologic changes of CECs can be detected before the clinically visible onset of allograft rejection.

Soluble vascular endothelial growth factor receptor-3 suppresses allosensitization and promotes corneal allograft survival

PURPOSE

To investigate the effect of VEGF-C and VEGF-D blockade via soluble VEGFR-3 (sVEGFR-3) on T cell allosensitization, corneal neovascularization, and transplant survival.

METHODS

Corneal intrastromal suture placement and allogeneic transplantation were performed on BALB/c mice to evaluate the effect of sVEGFR-3 on corneal neovascularization. Soluble VEGFR-3 trap was injected intraperitoneally to block VEGF-C/D (every other day starting the day of surgery). Immunohistochemical staining of corneal whole mounts was performed using anti-CD31 (PECAM-1) and anti-LYVE-1 antibodies to quantify the levels of hem- and lymphangiogenesis, respectively. Mixed lymphocyte reaction (MLR) was performed to assess indirect and direct host T cell allosensitization and the frequencies of IFN-γ-producing T cells in the draining lymph nodes were assessed using flow cytometry. Graft opacity and survival was evaluated by slit-lamp biomicroscopy.

RESULTS

Treatment with sVEGFR-3 resulted in a significant blockade of lymphangiogenesis 2 weeks post-transplantation and significantly prolonged corneal allograft survival compared to the control group at 8 weeks post-transplantation (87.5 % vs. 50 %), and this was associated with significant reduction in the frequencies of allosensitized T cells and decreased frequencies of IFN-γ-producing CD4 T cells.

CONCLUSIONS

Soluble VEGFR-3 suppresses corneal lymphangiogenesis and allograft rejection and may offer a viable therapeutic modality for corneal neovascularization and corneal transplantation.

Immunotherapy converts nonimmunogenic pancreatic tumors into immunogenic foci of immune regulation

Pancreatic ductal adenocarcinoma (PDAC) is considered a "nonimmunogenic" neoplasm. Single-agent immunotherapies have failed to demonstrate significant clinical activity in PDAC and other "nonimmunogenic" tumors, in part due to a complex tumor microenvironment (TME) that provides a formidable barrier to immune infiltration and function. We designed a neoadjuvant and adjuvant clinical trial comparing an irradiated, granulocyte-macrophage colony-stimulating factor (GM-CSF)-secreting, allogeneic PDAC vaccine (GVAX) given as a single agent or in combination with low-dose cyclophosphamide to deplete regulatory T cells (Treg) as a means to study how the TME is altered by immunotherapy. Examination of resected PDACs revealed the formation of vaccine-induced intratumoral tertiary lymphoid aggregates in 33 of 39 patients 2 weeks after vaccine treatment. Immunohistochemical analysis showed these aggregates to be regulatory structures of adaptive immunity. Microarray analysis of microdissected aggregates identified gene-expression signatures in five signaling pathways involved in regulating immune-cell activation and trafficking that were associated with improved postvaccination responses. A suppressed Treg pathway and an enhanced Th17 pathway within these aggregates were associated with improved survival, enhanced postvaccination mesothelin-specific T-cell responses, and increased intratumoral Teff:Treg ratios. This study provides the first example of immune-based therapy converting a "nonimmunogenic" neoplasm into an "immunogenic" neoplasm by inducing infiltration of T cells and development of tertiary lymphoid structures in the TME. Post-GVAX T-cell infiltration and aggregate formation resulted in the upregulation of immunosuppressive regulatory mechanisms, including the PD-1-PD-L1 pathway, suggesting that patients with vaccine-primed PDAC may be better candidates than vaccine-naïve patients for immune checkpoint and other immunomodulatory therapies.