Expression Of Major Histocompatibility Complex Class Research Articles

Glucocorticoid receptor regulates PD-L1 and MHC-I in pancreatic cancer cells to promote immune evasion and immunotherapy resistance

Despite unprecedented responses of some cancers to immune checkpoint blockade (ICB) therapies, the application of checkpoint inhibitors in pancreatic cancer has been unsuccessful. Glucocorticoids and glucocorticoid receptor (GR) signaling are long thought to suppress immunity by acting on immune cells. Here we demonstrate a previously undescribed tumor cell-intrinsic role for GR in activating PD-L1 expression and repressing the major histocompatibility complex class I (MHC-I) expression in pancreatic ductal adenocarcinoma (PDAC) cells through transcriptional regulation. In mouse models of PDAC, either tumor cell-specific depletion or pharmacologic inhibition of GR leads to PD-L1 downregulation and MHC-I upregulation in tumor cells, which in turn promotes the infiltration and activity of cytotoxic T cells, enhances anti-tumor immunity, and overcomes resistance to ICB therapy. In patients with PDAC, GR expression correlates with high PD-L1 expression, low MHC-I expression, and poor survival. Our results reveal GR signaling in cancer cells as a tumor-intrinsic mechanism of immunosuppression and suggest that therapeutic targeting of GR is a promising way to sensitize pancreatic cancer to immunotherapy.

Proteasome inhibitors restore the STAT1 pathway and enhance the expression of MHC class I on human colon cancer cells

BackgroundA new strategy, particularly a novel combination, for immunotherapy in microsatellite stable metastatic colorectal cancer (mCRC) treatment needs to be formulated. Studies on the interferon-γ (IFN-γ)/ Janus kinase (JAK)/ signal transducer and activator of transcription (STAT)1 pathway provide new directions in this regard.MethodsOur study applies three colon cancer cell lines, including microsatellite stable (MSS) cell lines, which are SW480 and SW620, and microsatellite instability-high (MSI-H) cell line, which is DLD-1. We compared the expressions of immune surface markers on colon cancer cells in response to IFN-γ. We elucidated these mechanisms, which involved the upregulation of immune surface markers. Furthermore, we examined real-world clinical samples using the PerkinElmer Opal multiplex system and NanoString analysis.ResultsWe established that the baseline expression of major histocompatibility complex (MHC) class I alleles and programmed death-ligand 1 (PD-L1) were generally low in cell line models. The immune surface markers were significantly increased after IFN-γ stimulation on SW480 but were notably unresponsive on the SW620 cell line. We discovered that STAT1 and phosphorylated STAT1 (pSTAT1) were downregulated in the SW620 cell line. We verified that the STAT1/pSTAT1 could be restored through the application of proteasome inhibitors, especially bortezomib. The expression of MHC class I as downstream signals of STAT1 was also up-regulated by proteasome inhibitors. The similar results were reproduced in DLD-1 cell line, which was also initially unresponsive to IFN-γ. In real-world samples of patients with mCRC, we found that higher STAT1 expression in tumor cells was strongly indicative of a highly immunogenic microenvironment, with significantly higher expression levels of MHC class I and PD-L1, not only on tumor cells but also on non-tumor cells. Furthermore, tumor infiltrating lymphocytes (TILs) were increased in the positive-STAT1 group. Through NanoString analysis, we confirmed that the mRNA expressions of IFN-γ, human leukocyte antigen (HLA)-A, HLA-E, and HLA-G were also significantly higher in the positive-STAT1 group than those in the negative-STAT1 group.ConclusionOur study provides a novel rationale for the addition of bortezomib, a proteasome inhibitor, into new immunotherapy combinations.

Downregulation of Cell Surface Major Histocompatibility Complex Class I Expression Is Mediated by the Left-End Transcription Unit of Fowl Adenovirus 9.

Major histocompatibility complex class I (MHC-I) molecules play a critical role in the host’s antiviral response by presenting virus-derived antigenic peptides to cytotoxic T lymphocytes (CTLs), enabling the clearance of virus-infected cells. Human adenoviruses evade CTL-mediated cell lysis, in part, by interfering directly with the MHC-I antigen presentation pathway through the expression of E3-19K, which binds both MHC-I and the transporter associated with antigen processing protein and sequestering MHC-I within the endoplasmic reticulum. Fowl adenoviruses have no homologues of E3-19K. Here, we show that representative virus isolates of the species Fowl aviadenovirus C, Fowl aviadenovirus D, and Fowl aviadenovirus E downregulate the cell surface expression of MHC-I in chicken hepatoma cells, resulting in 71%, 11%, and 14% of the baseline expression level, respectively, at 12 h post-infection. Furthermore, this work reports that FAdV-9 downregulates cell surface MHC-I through a minimum of two separate mechanisms—a lysosomal-independent mechanism that requires the presence of the fowl adenovirus early 1 (FE1) transcription unit located within the left terminal genomic region between nts 1 and 6131 and a lysosomal-dependent mechanism that does not require the presence of FE1. These results establish a new functional role for the FE1 transcription unit in immune evasion. These studies provide important new information about the immune evasion of FAdVs and will enhance our understanding of the pathogenesis of inclusion body hepatitis and advance the progress made in next-generation FAdV-based vectors.

Venetoclax or Ruxolitinib in Pre-Transplant Conditioning Lowers the Engraftment Barrier by Different Mechanisms in Allogeneic Stem Cell Transplant Recipients.

Allogeneic stem cell transplantation (alloSCT) is utilised to cure haematological malignancies through a combination of conditioning regimen intensity and immunological disease control via the graft versus tumour (GVT) effect. Currently, conventional myeloablative chemotherapeutic or chemoradiation conditioning regimens are associated with significant side effects including graft versus host disease (GVHD), infection, and organ toxicity. Conversely, more tolerable reduced intensity conditioning (RIC) regimens are associated with unacceptably higher rates of disease relapse, partly through an excess incidence of mixed chimerism. Improvement in post-alloSCT outcomes therefore depends on promotion of the GVT effect whilst simultaneously reducing conditioning-related toxicity. We have previously shown that this could be achieved through BCL-2 inhibition, and in this study, we explored the modulation of JAK1/2 as a strategy to lower the barrier to donor engraftment in the setting of RIC. We investigated the impact of short-term treatment of BCL2 (venetoclax) or JAK1/2 (ruxolitinib) inhibition on recipient natural killer and T cell immunity and the subsequent effect on donor engraftment. We identified striking differences in mechanism of action of these two drugs on immune cell subsets in the bone marrow of recipients, and in the regulation of MHC class-II and interferon-inducible gene expression, leading to different rates of GVHD. This study demonstrates that the repurposed use of ruxolitinib or venetoclax can be utilised as pre-transplant immune-modulators to promote the efficacy of alloSCT, whilst reducing its toxicity.

MHC class II in renal tubules plays an essential role in renal fibrosis.

Immunomodulation is considered a potential therapeutic approach for chronic kidney disease (CKD). Although it has been previously reported that CD4+ T cells contribute to the development of renal fibrosis, the role of MHC class II (MHCII) in the development of renal fibrosis remains largely unknown. The present study reports that the expression of MHCII molecules in renal cortical tubules is upregulated in mouse renal fibrosis models generated by unilateral ureter obstruction (UUO) and folic acid (FA). Proximal tubule epithelial cells (PTECs) are functional antigen-presenting cells that promote the proliferation of CD4+ T cells in an MHCII-dependent manner. PTECs from mice with renal fibrosis had a stronger ability to induce T cell proliferation and cytokine production than control cells. Global or renal tubule-specific ablation of H2-Ab1 significantly alleviated renal fibrosis following UUO or FA treatment. Renal expression of profibrotic genes showed a consistent reduction in H2-Ab1 gene-deficient mouse lines. Moreover, there was a marked increase in renal tissue CD4+ T cells after UUO or FA treatment and a significant decrease following renal tubule-specific ablation of H2-Ab1. Furthermore, renal tubule-specific H2-Ab1 gene knockout mice exhibited higher proportions of regulatory T cells (Tregs) and lower proportions of Th2 cells in the UUO- or FA-treated kidneys. Finally, Immunohistochemistry (IHC) studies showed increased renal expression of MHCII and the profibrotic gene α smooth muscle actin (α-SMA) in CKD patients. Together, our human and mouse data demonstrate that renal tubular MHCII plays an important role in the pathogenesis of renal fibrosis.

Engineering Chameleon Prodrug Nanovesicles to Increase Antigen Presentation and Inhibit PD-L1 Expression for Circumventing Immune Resistance of Cancer.

Immune evasion is the major obstacle for T-cell-based cancer immunotherapy. The insufficient expression of the tumor-rejection antigen causes the intrinsic immune resistance and high expression of programmed death ligand 1 (PD-L1) induced by interferon gamma (IFN-γ), which accounts for the inducible immune resistance. To deal with both the intrinsic and inducible immune resistance of cancer, a multifunctional prodrug nanovesicle is sequentially developed. It is first sorted out that doxycycline (Doxy) efficiently inhibits autophagy of the tumor cells, and increases the surface level of major histocompatibility complex class I (MHC-I). Then, chameleon-inspired prodrug nanovesicles are engineered for tumor-targeted delivery of Doxy. The prodrug nanovesicles integrating a sheddable poly(ethylene glycol) shell and CRGDK ligand are kept stable during blood circulation, while exposing the targeting ligand in the tumor, which significantly inhibits autophagy, elicits MHC-I expression, increases tumor antigen presentation, recruits more tumor-infiltrating T lymphocytes, and suppresses FN-γ-induced intratumoral PD-L1 expression. After a proof of concept for overcoming intrinsic and inducible immune evasion, the prodrug nanovesicles are applied to validate the efficacy of cancer immunotherapy in two tumor-bearing mouse models. This research thus provides a novel targeting strategy for reducing tumor immune resistance and potentiating tumor immunotherapy.

Generation of Monkey Induced Pluripotent Stem Cell-Derived Cartilage Lacking Major Histocompatibility Complex Class I Molecules on the Cell Surface.

Due to the poor capacity for articular cartilage to regenerate, its damage tends to result in progressively degenerating conditions such as osteoarthritis. To repair the damage, the transplantation of allogeneic human induced pluripotent stem cell (iPSC)-derived cartilage is being considered. However, although allogeneic cartilage transplantation is effective, immunological reactions can occur. One hypothetical solution is to delete the expression of major histocompatibility complex (MHC) class I molecules to reduce the immunological reactions. For this purpose, we deleted the β2 microglobulin (B2M) gene in a cynomolgus monkey (crab-eating monkey [Macaca fascicularis]) iPS cells (cyiPSCs) to obtain B2M−/− cyiPSCs using the CRISPR/Cas9 system. Western blot analysis confirmed B2M−/− cyiPSCs lacked B2M protein, which is necessary for MHC class I molecules to be transported to and expressed on the cell surface by forming multimers with B2M. Flow cytometry analysis revealed no B2M−/− cyiPSCs expressed MHC class I molecules on their surface. The transplantation of B2M−/− cyiPSCs in immunodeficient mice resulted in teratoma that contained cartilage, indicating that the lack of MHC class I molecules on the cell surface affects neither the pluripotency nor the chondrogenic differentiation capacity of cyiPSCs. By modifying the chondrogenic differentiation protocol for human iPSCs, we succeeded at differentiating B2M+/+ and B2M−/− cyiPSCs toward chondrocytes followed by cartilage formation in vitro, as indicated by histological analysis showing that B2M+/+ and B2M−/− cyiPSC-derived cartilage were positively stained with safranin O and expressed type II collagen. Flow cytometry analysis confirmed that MHC class I molecules were not expressed on the cell surface of B2M−/− chondrocytes isolated from B2M−/− cyiPSC-derived cartilage. An in vitro mixed lymphocyte reaction assay showed that neither B2M+/+ nor B2M−/− cyiPSC-derived cartilage cells stimulated the proliferation of allogeneic peripheral blood mononuclear cells. On the contrary, osteochondral defects in monkey knee joints that received allogeneic transplantations of cyiPSC-derived cartilage showed an accumulation of leukocytes with more natural killer cells around B2M−/− cyiPSC-derived cartilage than B2M+/+ cartilage, suggesting complex mechanisms in the immune reaction of allogeneic cartilage transplanted in osteochondral defects in vivo.Impact statementThe transplantation of allogeneic induced pluripotent stem cell (iPSC)-derived cartilage is expected to treat articular cartilage damage, although the effects of major histocompatibility complex (MHC) in immunological reactions have not been well studied. We succeeded at creating B2M−/− cynomolgus monkey (cy)iPSCs and cyiPSC-derived cartilage that lack MHC class I molecules on the cell surface. B2M−/− cyiPSC-derived cartilage cells did not stimulate the proliferation of allogeneic peripheral blood mononuclear cells in vitro. On the contrary, the transplantation of B2M−/− cyiPSC-derived cartilage into osteochondral defects in monkey knee joints resulted in survival of transplants and accumulation of leukocytes, including natural killer cells, suggesting complex mechanisms for the immune reaction.

Establishment of incontinence-associated dermatitis rat models and assessment of the therapeutic effects of zinc oxide, painless skin protective film and silicone dressing.

The aim of the present study was to construct incontinence-associated dermatitis (IAD) rat models and observe the therapeutic effects of zinc oxide, painless skin protective film and silicone dressing on IAD. A total of 54 rats were randomly divided into nine groups: i) Control group; ii) trypsin model group; iii) model + zinc oxide group; iv) model + painless skin protective film group; v) model + silicon dressing group; vi) synthetic urine combined with trypsin model group (joint model group); vii) joint model + zinc oxide group; viii) joint model + painless skin protective film group; and ix) joint model + silicone dressing group. A total of 4 days after applying the zinc oxide, protective film or silicon dressing intervention, IAD scores and pH values in skin tissues were examined. Skin tissues and blood samples were collected. Hematoxylin and eosin staining, immunohistochemical staining of major histocompatibility complex class II (MHC-II) and western blot analysis of MHC-II, NF-κB/p65, phosphorylated (p)-NF-κB/p65, STAT1 and p-STAT1 were carried out in skin tissue. Serum IFN-γ, IL-1β, IL-2 and TNF-α levels were determined using ELISA. The results demonstrated that IAD scores and pH values were both higher in the model groups than the control, which were significantly ameliorated by silicone dressing. The skin tissue structure of IAD rats both in trypsin model group and joint model group was severely damaged, the wounds were not covered by epidermis, and numerous inflammatory cell infiltrations were observed. After treatment, dermatitis was improved. Skin tissue from the trypsin and joint IAD models had higher MHC-II, NF-κB p65, p-NF-κB p65, STAT1 and p-STAT1 expression than controls, which was decreased by protective film and silicon dressing. Zinc oxide reduced NF-κB p65, p-NF-κB p65, STAT1 and p-STAT1 expression. However, no significant differences were observed in NF-κB/p-NF-κB ratio and STAT1/p-STAT1 ratio among groups. Furthermore, serum IFN-γ, IL-1β, IL-2 and TNF-α levels were significantly elevated in trypsin and joint IAD rats. The upregulation of these cytokines was significantly inhibited after all three treatments. Among the three treatment methods, silicone dressing had the best therapeutic effect. Thus, these findings revealed that zinc oxide, painless skin protective film and silicone dressing could ameliorate the severity of IAD rat models, and that silicone dressing possessed the best therapeutic effect.

Abstract 1769: Study of innate immune responses during small cell lung cancer (SCLC) development

Abstract SCLC is a highly aggressive neuroendocrine tumor with dismal prognosis. Inability to detect SCLC early renders surgical resections a rare event, limiting investigation of the early stages of tumor development. We sought to address this challenge using a genetically engineered mouse model (GEMM) to investigate how the innate immune system responds to SCLC development. The RPM (Rb1fl/fl, p53fl/fl, MycLSL/LSL) SCLC GEMM was selected to characterize the local immune microenvironment throughout the process of tumor development. Following tumor induction using an intranasally installed Cre bearing adenovirus, lung tissue was collected and analyzed using multi-parametric flow cytometry to assess changes in innate immune cell populations. Induction of SCLC resulted in late stage disease being present in animals approximately 7 weeks after virus exposure. Flow cytometric analysis of immune cell populations of the whole lung showed no significant differences in the overall levels of immune cell types, although an upwards trend in the levels of neutrophils in tumor-bearing mice was observed. The most significant finding was a decrease in the expression levels of major histocompatibility complex class II (MHCII) in both alveolar and interstitial macrophage populations. Further characterization, including separate analysis of the two interstitial macrophage subpopulations described by Chakarov et al. (Science 2019), and Schyns et al. (Nature Communications 2019), showed significant drops in levels of MHCII in all populations as measured by median fluorescent intensity (MFI) (p=0.004 in alveolar macrophages, p=0.0148 in vascular supporting CD206+ve interstitial macrophages, and p=0.0027 in CD206-ve interstitial macrophages). The striking difference between the changes seen in these populations was that alveolar and CD206+ve interstitial macrophages both showed a downward shift in MHCII expression as a whole, while CD206-ve macrophages acquired a novel population completely negative for MHCII accounting for approx. half of the CD206-ve macrophage subpopulation. The development of SCLC has been found to result in all macrophage subtypes expressing lower levels of MHCII, pointing towards a more immunosuppressive immune environment. The population of CD206-ve MHCII-ve interstitial macrophages is of particular interest, as it is contrary to the currently described interstitial macrophage phenotypes. A more in-depth characterization of all macrophage populations in the mouse lung, including their precise phenotype and localization is currently underway using CyTOF and IHC approaches. The precise timings of the observed changes are being elucidated through analysis of a disease time-course ranging from very early stage to late stage disease, in order to better understand the process of SCLC development. Citation Format: Jakub Chudziak, Melanie Galvin, Antonia Banyard, Kathryn L. Simpson, Kristopher K. Frese, Elaine Kilgour, Tracy Hussell, Caroline Dive. Study of innate immune responses during small cell lung cancer (SCLC) development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1769.

Abstract 1776: Tumor-derived endothelins regulate antitumor immune responses through macrophage endothelin B receptor

Abstract Soft tissue sarcomas (STS) comprise a heterogeneous group of solid tumors arising from mesodermal tissues. With few effective systemic therapies, advanced-stage STS is frequently fatal. Immune checkpoint blockade (ICB) is currently under investigation for the treatment of STS. However, STS harbor a highly immunosuppressive tumor microenvironment (TME) that inhibits effective antitumor T cell responses, with only a subset of patients responding to ICB. While the major focus of immunotherapy to date has been on the role of T cells, targeting innate immune cells such as tumor associated macrophages (TAMs) within the TME holds great promise. TAMs are the most abundant leukocytes in STS, and contribute to the establishment of an immunosuppressive TME through multiple mechanisms. We identified the endothelin B receptor (EDNRB) as a potential novel therapeutic target on TAMs based on an analysis of TCGA data. EDNRB is highly expressed in “immunologically quiet” tumors with high macrophage to T cell ratios and M2-like gene expression. EDNRB encodes a G-protein-coupled receptor that binds the vasoactive peptides endothelin (EDN) 1, 2, or 3. EDNRB is upregulated during macrophage differentiation, and is highly expressed by certain macrophages subsets, including TAMs. However, the role of the EDN-EDNRB axis in regulating macrophage function and antitumor immunity is unknown. Using a murine syngeneic transplant model with cell lines derived from methylcholanthrene-induced fibrosarcomas, we first genetically deleted or overexpressed the ligand Edn1 in sarcoma cells prior to transplant. Genetic deletion of Edn1 using CRISPR-Cas9 resulted in significantly increased major histocompatibility complex class II (MHCII) expression in TAMs, indicative of a more immunostimulatory phenotype. RNA-seq of sorted TAMs from Edn1 CRISPR tumors revealed enrichment for gene sets involved in antitumor immunity, including interferon gamma and NF-kB. Conversely, overexpression of Edn1 dramatically reduced TAM MHCII expression. Furthermore, knockout of Edn1 or pharmacologic blockade of EDNRB significantly enhanced responses to anti-PD1. To confirm these effects were mediated by macrophage EDNRB, we proceeded to generate a conditional deletion of Ednrb in TAMs by crossing Ednrbflox/flox and LysM-Cre mice. Consistent with our hypothesis, TAMs from sarcomas in LysM-Cre:Ednrbflox/flox mice also took on an immunostimulatory phenotype, with increased MHCII expression and reduced M2 markers. Taken together, these findings support the existence of a novel regulatory axis, whereby tumor-derived endothelins promote a suppressive TAM phenotype through macrophage EDNRB. Combining endothelin receptor antagonists with immune checkpoint blockade has the potential to enhance antitumor immune responses in STS and other solid tumors by targeting both innate and adaptive immune cells within the TME. Citation Format: Ian Wesley Folkert, Tsun Ki Jerrick To, Samir Devalaraja, Robert J. Norgard, Malay Haldar. Tumor-derived endothelins regulate antitumor immune responses through macrophage endothelin B receptor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1776.

Genetic Characterization and Clinical Impact of Loss of MHC Class I and II Expression in De Novo Diffuse Large B-Cell Lymphoma

Introduction: Immune recognition by T cells requires the presentation of processed peptides in association with major histocompatibility complex class I (MHC-I) and class II (MHC-II) molecules. Among the tumor immune escape mechanisms described to date, alterations in the expression of MHC molecules play a crucial role in the development of diffuse large B-cell lymphoma (DLBCL). Loss of MHC-I or -II expression in DLBCL can occur through multiple mechanisms, including deletion of the MHC-I and -II locus, loss of function mutations of B2M, and genetic alterations of CIITA ; however, the role of additional genetic and epigenetic mechanisms remains largely unknown. With regard to clinical significance, a number of studies have reported that low MHC-II expression on tumor cells is associated with shorter survival in DLBCL, while the prognostic effect of MHC-I expression has not been systematically evaluated in a large, homogeneously treated cohort. In addition, although the frequency of loss of MHC-II expression differs between ABC- and GCB-DLBCL cell of origin (COO) subtypes, the prognostic impact remains ill-defined. Here, we conducted a comprehensive phenotypic and genetic analysis in a population-based DLBCL cohort to investigate the genetic background and clinical relevance of loss of MHC-I and -II expression.Method: We analyzed biopsies from 347 patients newly diagnosed with de novo DLBCL and uniformly treated with R-CHOP at the BC Cancer Agency. High-resolution copy number analysis was performed using Affymetrix SNP 6.0 arrays. Mutation status was determined using deep targeted re-sequencing of the coding exons of 57 genes with a Truseq Custom Amplicon assay (Illumina) and/or Fluidigm Access Array chips, and RNAseq. Immunohistochemical staining of MHC-I and -II was performed on tissue microarrays (n=332). COO was assigned by gene expression (Lymph2Cx assay) in 323 cases (183 GCB, 104 ABC and 36 unclassifiable).Results: We found the following MHC-I and -II staining patterns:membrane-positive (n=188 (57%) and n=233 (72%), respectively), cytoplasmic only-positive / membrane-negative (n=86 (26%) and 31 (10%), respectively) and negative staining for both membrane and cytoplasmic (n=55 (17%) and n=59 (18%), respectively). Overall, membranous MHC-I and -II expression was not detected in 141/329 (43%) and 90/323 (28%) cases, respectively. While the frequency of loss of MHC-I expression was not different between COO subtypes, loss of MHC-II expression occurred more often in ABC-DLBCL (36% vs 22%, p=0.026). This is consistent with previous observations showing that MHC-II expression is reduced during plasmacytic differentiation and in ABC-DLBCL. Loss of MHC-I expression was associated with B2M mutation and deletion as well as with HLA-C deletions (all p <0.001, Fisher's exact test). Interestingly, mutations of EZH2 and GNA13 were detected more frequently in cases that had loss of MHC-I expression (p <0.001 and p=0.004, respectively). Moreover, mutations of CIITA and RFXAP (components of the MHC-II enhanceosome), and mutations of PRDM1 and TNFAIP3, ABC-DLBCL-specific mutations, were significantly enriched in MHC-II negative cases. Of note, mutations of B2M and EZH2 were significantly associated with loss of MHC-II expression, as well (p=0.001 and p=0.016, respectively). The associations between EZH2 mutation and MHC-I and -II expression were also observed when the analysis was restricted to GCB-DLBCL (both p <0.0001).With a median follow up of 6.5 years for living patients, the loss of MHC-I expression was not associated with survival in the entire DLBCL cohort, as well as within each COO subtype. Although there was also no significant survival difference according to the MHC-II expression status in the entire DLBCL cohort, loss of MHC-II expression was associated with an inferior 5y-time to progression (TTP, 59% vs 79%, p=0.007) in the GCB subtype. Interestingly, in the ABC subtype, loss of MHC-II expression was associated with a superior 5y-TTP (64% vs 40%, p=0.03).Conclusion: Our approach using next generation sequencing and high resolution SNP arrays uncovered the genetic background, as well as the clinical impact of loss of MHC-I and-II expression in a uniformly R-CHOP-treated large population-based cohort of DLBCL patients. Our results warrant further studies investigating a potential mechanism of EZH2 mutations regulating MHC-I and -II expression in DLBCL. DisclosuresSavage:Bristol-Myers Squibb: Honoraria; Seattle Genetics: Consultancy, Honoraria; Roche: Research Funding; Celgene: Consultancy; Merck: Honoraria. Sehn:Celgene: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria; Seattle Genetics: Consultancy, Honoraria; Roche/Genentech: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Amgen: Consultancy, Honoraria. Morin:Epizyme, Inc: Consultancy. Connors:Genentech: Research Funding; Bayer Healthcare: Research Funding; Lilly: Research Funding; Merck: Research Funding; Seattle Genetics: Research Funding; Amgen: Research Funding; Janssen: Research Funding; F Hoffmann-La Roche: Research Funding; NanoString Technologies: Research Funding; Bristol-Myers Squibb: Research Funding; Cephalon: Research Funding; Takeda: Research Funding; NanoString Technologies, Amgen, Bayer, BMS, Cephalon, Roche, Genentech, Janssen, Lilly, Merck, Seattle Genetics, Takeda,: Research Funding. Scott:Celgene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; BCCA: Patents & Royalties: Patent describing molecular subtyping of DLBCL licensed to NanoString Technologies. Patent describing measurement of the proliferation signature in MCL.. Steidl:Affimed Therapeutics: Consultancy; Juno Therapeutics: Consultancy.

Thymic Epithelial Cell Alterations and Defective Thymopoiesis Lead to Central and Peripheral Tolerance Perturbation in MHCII Deficiency.

Major Histocompatibility Complex (MHC) class II (MHCII) deficiency (MHCII-D), also known as Bare Lymphocyte Syndrome (BLS), is a rare combined immunodeficiency due to mutations in genes regulating expression of MHCII molecules. MHCII deficiency results in impaired cellular and humoral immune responses, leading to severe infections and autoimmunity. Abnormal cross-talk with developing T cells due to the absence of MHCII expression likely leads to defects in thymic epithelial cells (TEC). However, the contribution of TEC alterations to the pathogenesis of this primary immunodeficiency has not been well characterized to date, in particular in regard to immune dysregulation. To this aim, we have performed an in-depth cellular and molecular characterization of TEC in this disease. We observed an overall perturbation of thymic structure and function in both MHCII−/− mice and patients. Transcriptomic and proteomic profiling of murine TEC revealed several alterations. In particular, we demonstrated that impairment of lymphostromal cross-talk in the thymus of MHCII−/− mice affects mTEC maturation and promiscuous gene expression and causes defects of central tolerance. Furthermore, we observed peripheral tolerance impairment, likely due to defective Treg cell generation and/or function and B cell tolerance breakdown. Overall, our findings reveal disease-specific TEC defects resulting in perturbation of central tolerance and limiting the potential benefits of hematopoietic stem cell transplantation in MHCII deficiency.

Hepatitis C virus modulates signal peptide peptidase to alter host protein processing

Immunoevasins are viral proteins that prevent antigen presentation on major histocompatibility complex (MHC) class I, thus evading host immune recognition. Hepatitis C virus (HCV) evades immune surveillance to induce chronic infection; however, how HCV-infected hepatocytes affect immune cells and evade immune recognition remains unclear. Herein, we demonstrate that HCV core protein functions as an immunoevasin. Its expression interfered with the maturation of MHC class I molecules catalyzed by the signal peptide peptidase (SPP) and induced their degradation via HMG-CoA reductase degradation 1 homolog, thereby impairing antigen presentation to CD8+ T cells. The expression of MHC class I in the livers of HCV core transgenic mice and chronic hepatitis C patients was impaired but was restored in patients achieving sustained virological response. Finally, we show that the human cytomegalovirus US2 protein, possessing a transmembrane region structurally similar to the HCV core protein, targets SPP to impair MHC class I molecule expression. Thus, SPP represents a potential target for the impairment of MHC class I molecules by DNA and RNA viruses.

Lactobacillus johnsonii activates porcine monocyte derived dendritic cells maturation to modulate Th cellular immune response

Lactobacilli are abundant in the intestinal tract where they constantly regulate immune system via interacting with a great diversity of immune cells, such as dendritic cells (DCs). Notably, DCs are powerful antigen-presenting cells and they are capable of initiating primary immune responses. In this study, we studied the effects of Lactobacillus johnsonii (L. johnsonii) and Lactobacillus johnsonii cell-free supernatant (L. johnsonii-CFS) on the activation of porcine monocyte-derived dendritic cells (MoDCs) and their regulation of Th cellular immune responses in vitro. The MoDCs generated from porcine peripheral blood monocytes were stimulated by L. johnsonii and L. johnsonii-CFS, respectively. Pre-incubation with L. johnsonii increased expression of CD172a, CD80, major histocompatibility complex class II (MHCII) in MoDCs, and enhanced the ability of MoDCs to induce the proliferation of CD4+ T cell, while pre-incubation with L. johnsonii-CFS merely upregulated the expression of MHCII. Analysis of the cytokines showed that L. johnsonii stimulated up-regulation of Th1-type cytokines (IL-12p40, IFN-γ, TNF-α), pro-inflammatory cytokine IL-1β, chemokine CCL20, and Treg-type / anti-inflammatory cytokines IL-10 in MoDCs. Notably, a high production of IL-10 was observed in the MoDCs treated with L. johnsonii-CFS, indicating L. johnsonii-CFS exerted anti-inflammatory effects. Furthermore, L. johnsonii induced up-regulation of TLR2 and TLR6, but L. johnsonii-CFS not. Moreover, MoDCs stimulated by L. johnsonii mainly promoted T cell differentiate into Th1/Th2/Treg cells and plays an important role in improving the balance between Th1/Th2/Treg-type cells, whereas MoDCs stimulated by L. johnsonii-CFS mainly directed T cell to Th2/Treg subset polarization. In conclusion, L. johnsonii and L. johnsonii-CFS exhibited the ability of modulating innate immunity by regulating immunological functions of MoDCs in vitro, suggesting their potential ability to use as microecological preparations and medicines.

125I seed combined with DCS loaded with tumor antigen to convert irradiated liver cancer into effective in situ vaccine.

e14573 Background: With unique feature of self-immune tolerance and high radio-sensitivity, hepatocellular carcinoma (HCC) can gradually develop undesired effects. Iodine-125 (125I) seed, as a source of internal radiation therapy, may have a favorable adaptability and immunostimulation. In this study, we investigated whether 125I seeds can stimulate local tumor infiltrating lymphocytes (TILs) and whether a combination of 125I seeds and dendritic cells (DCs) loaded with tumor antigen (Ag+DCs) can enhance both local tumor control and abscopal effect in murine subcutaneous tumor models. The related mechanism of anti-tumor immune response was also explored. Methods: H22/Hepa1-6 HCC cells were examined for radiosensitivity and immunosensitivity. Cell apoptosis and expression of MHC-I (major histocompatibility complex class I) and PD-L1 (programmed death-ligand 1) were detected before and after irradiation. The tumor cells were injected subcutaneously as primary and abscopal tumor. Bone marrow-derived dendritic cells (BM-DCs) were induced from mouse bone marrow cells and incubated with tumor cell lysate. 125I seeds were implanted into the primary tumors, followed by intratumoral injection of Ag+DCs and intraperitoneal injection of αPD1 antibody (αPD1-ab). DC migration was detected by transwell chambers in vitro and CFSE (carboxyfluorescein succinimidyl ester)-labeled DCs in vivo. DC maturation was tested by flow cytometry. Analyses of tumor growth and survival rates were performed in vitro, and that of, TILs, T-cell proliferation, cytotoxicity test, immunostimulatory cytokines release, and immunological memory were performed in vivo. In situ vaccine and abscopal effect were verified in orthotopic mouse models of liver cancer and lung metastatic tumor. Results: 125I seeds alone could induce TILs and activate cytotoxic T cells (CTLs), but these effects were limited. The combination treatment of 125I seeds with Ag+DC administration inhibited primary tumor growth and significantly prolonged survival time in association with a significant increase in T-cell proliferation and interferon-γ release. In addition, triple-combination treatment with αPD1-ab amplified these responses, leading to significant regression of primary and metastatic tumors and successful stimulation of immunological memory. Conclusions: 125I seeds can safely activate anti-tumor immune response.125I seeds combined with Ag+DC administration is able to convert irradiated liver cancer into effective in situ vaccine. Furthermore, triple-combination therapy of 125I seeds, Ag+DC, and αPD1-ab can be a promising approach to activate systemic anti-tumor immunity, which is a potential novel individualized therapy for patients with solid cancers.

B cells modulate the expression of MHC-II on cardiac CCR2− macrophages

The uninjured murine heart contains a heterogeneous population of macrophages with disparate ontogenies and functions. These macrophages are often associated with blood vessels and can be subclassified based on the expression of CC chemokine receptor 2 (CCR2) and major histocompatibility complex class II (MHC-II). The biological cues that modulate these macrophage pool subpopulations have not been completely identified. It has been recently shown that a sub-population of circulating naïve B cells adheres to the myocardial microvasculature. We hypothesized that B cells might modulate the phenotype of myocardial macrophages. To test this hypothesis, we analyzed both the relative location of B cells and macrophages in myocardial histological section and the prevalence of myocardial macrophage subsets in hearts from B cell–deficient mice (μMT) and mice depleted of B cells through administration of an anti-CD20 antibody. We found that B cells pause in the microvasculature in proximity of macrophages and modulate the number of myocardial CCR2−MHC-IIhigh cells. Through in vitro studies we found that this is likely the result of a paracrine effect of B cells on the expression of MHC-II in CCR2− cells. These results reveal an unexpected relationship between B cells and resident macrophages and, highlighting a direct intramyocardial effect of circulating B cells, challenge the currently held belief that naïve recirculating B lymphocytes merely shuttle between lymphoid stations.

The Murine MHC Class II Super Enhancer IA/IE-SE Contains a Functionally Redundant CTCF-Binding Component and a Novel Element Critical for Maximal Expression.

In both humans and mice, CTCF-binding elements form a series of interacting loops across the MHC class II (MHC-II) locus, and CTCF is required for maximal MHC-II gene expression. In humans, a CTCF-bound chromatin insulator termed XL9 and a super enhancer (SE) DR/DQ-SE situated in the intergenic region between HLA-DRB1 and HLA-DQA1 play critical roles in regulating MHC-II expression. In this study, we identify a similar SE, termed IA/IE-SE, located between H2-Eb1 and H2-Aa of the mouse that contains a CTCF site (C15) and a novel region of high histone H3K27 acetylation. A genetic knockout of C15 was created and its role on MHC-II expression tested on immune cells. We found that C15 deletion did not alter MHC-II expression in B cells, macrophages, and macrophages treated with IFN-γ because of functional redundancy of the remaining MHC-II CTCF sites. Surprisingly, embryonic fibroblasts derived from C15-deleted mice failed to induce MHC-II gene expression in response to IFN-γ, suggesting that at least in this developmental lineage, C15 was required. Examination of the three-dimensional interactions with C15 and the H2-Eb1 and H2-Aa promoters identified interactions within the novel region of high histone acetylation within the IA/IE-SE (termed N1) that contains a PU.1 binding site. CRISPR/Cas9 deletion of N1 altered chromatin interactions across the locus and resulted in reduced MHC-II expression. Together, these data demonstrate the functional redundancy of the MHC-II CTCF elements and identify a functionally conserved SE that is critical for maximal expression of MHC-II genes.

INF-λ enhances expression of MHC class I molecules on thymic epithelial

Abstract Introduction: The major histocompatibility complex class I (MHC-I) molecules is a cell surface glycoprotein involved in the presentation of endogenously derived peptides, to the TCR of CD8 T cells. Moreover, several vital processes specifically depend on the interaction between TCR and the MHC-I presented by the epithelial cells (ECs). However, the regulation of the MHC-I expression has been studied almost exclusively in hematolymphoid cells and very little is known about this process in ECs. In the present work, we performed a deep analysis of MHC-I expression in primary ECs freshly harvested from the thymus, skin, gut, and lung. Methods and Results: Our flow cytometry analysis showed that the abundance of cell surface MHC-I was overall 10- to 100-fold greater in thymic ECs (TECs) than in extrathymic EC types. Our transcriptomic analysis revealed a dominant role of IFN signalling in the differential MHC-I expression found in TECs vs. extrathymic ECs. In fact, superior MHC I expression in TECs is unaffected by deletion of Ifnar1 or Ifngr1, but is lessened by deletion of Aire, Ifnlr1, Stat1 or Nlrc5, and is driven mainly by type IFN-λ produced by TECs. Moreover, Ifnlr1−/− mice showed impaired negative selection of CD8 thymocytes, and at 9 months of age, present autoimmune manifestations. Conclusion and Relevance: In conclusion, our study opens the door to a new level of understanding of MHC-I regulation in ECs and will pave the way for a more detailed exploration of the impact of IFN-λ signaling in thymic functions.

B-cell-intrinsic MHCII signaling promotes microbiota diversity

Abstract The expression of major histocompatibility complex class II (MHCII) molecules is essential for the formation of germinal centers (GC) in lymphoid follicles, which are the primary sites for the generation of T-cell-dependent (TD) high-affinity antibody responses. Gut peyer's patches (PPs) are the dominant peripheral lymphoid tissues that give rise to TD antibody (primarily immunoglobulin A (IgA)) responses generated against the gut microbiota. While it is anticipated, a requirement of B-cell-intrinsic MHCII expression for GC formation has never been formally described. Additionally, while anti-commensal TD IgA responses have been shown to regulate microbiota composition and function, to what degree B-cell-intrinsic MHCII influences this process is also undefined. Here, we use a RAG1−/− adoptive transfer model, where RAG1−/− mice are either reconstituted with naive CD4+ T cells and MHCII+ B cells or naive CD4+ T cells and MHCII−B cells to address these gaps in our knowledge. Results from these experiments demonstrate that B-cell-intrinsic MHCII signaling is a strict requirement for GC-TFH cell development. Consequently, B-cell-intrinsic MHCII signaling promotes the generation of high-affinity anti-commensal IgA responses in the gut, which lead to increased species richness within the fecal but not small intestinal microbial community. Collectively, our data suggest that B-cell-intrinsic MHCII signaling is crucial for the generation of high-affinity anti-commensal IgA responses generated against the gut microbiota, and that this response favors a more diverse bacterial community.

Platelet MHC class I mediates CD8+ T-cell suppression during sepsis

AbstractCirculating platelets interact with leukocytes to modulate host immune and thrombotic responses. In sepsis, platelet-leukocyte interactions are increased and have been associated with adverse clinical events, including increased platelet–T-cell interactions. Sepsis is associated with reduced CD8+ T-cell numbers and functional responses, but whether platelets regulate CD8+ T-cell responses during sepsis remains unknown. In our current study, we systemically evaluated platelet antigen internalization and presentation through major histocompatibility complex class I (MHC-I) and their effects on antigen-specific CD8+ T cells in sepsis in vivo and ex vivo. We discovered that both human and murine platelets internalize and proteolyze exogenous antigens, generating peptides that are loaded onto MHC-I. The expression of platelet MHC-I, but not platelet MHC-II, is significantly increased in human and murine platelets during sepsis and in human megakaryocytes stimulated with agonists generated systemically during sepsis (eg, interferon-γ and lipopolysaccharide). Upregulation of platelet MHC-I during sepsis increases antigen cross-presentation and interactions with CD8+ T cells in an antigen-specific manner. Using a platelet lineage–specific MHC-I–deficient mouse strain (B2Mf/f-Pf4Cre), we demonstrate that platelet MHC-I regulates antigen-specific CD8+ T-cell proliferation in vitro, as well as the number and functional responses of CD8+ T cells in vivo, during sepsis. Loss of platelet MHC-I reduces sepsis-associated mortality in mice in an antigen-specific setting. These data identify a new mechanism by which platelets, through MHC-I, process and cross-present antigens, engage antigen-specific CD8+ T cells, and regulate CD8+ T-cell numbers, functional responses, and outcomes during sepsis.