Single-Cell Analysis Uncovers Striking Cellular Heterogeneity of Lung-Infiltrating Regulatory T Cells during Eosinophilic versus Neutrophilic Allergic Airway Inflammation.

Allergic airway inflammation results from uncontrolled immune responses to environmental Ags. Although it is well established that allergic immune responses exhibit a high degree of diversity, driven by primary effector cell types such as eosinophils, neutrophils, or CD4 T cells with distinct effector signatures, the mechanisms responsible for such pathogenesis remain elusive. Foxp3+ regulatory T cells (Tregs) are essential immune regulators during chronic inflammation, including allergic airway inflammation. Emerging evidence suggests that Tregs infiltrating inflamed tissues exhibit distinct phenotypes dependent on the specific tissue sites and can display heterogeneity and tissue residency. Whether diverse allergic airway inflammatory responses influence infiltrating Treg heterogeneity or Treg lung residency has not been explored. We employed an unbiased single-cell RNA sequencing approach to investigate lung-infiltrating Tregs in models of eosinophilic and neutrophilic airway inflammation. We found that lung-infiltrating Tregs are highly heterogeneous, and that Tregs displaying lung-resident phenotypes are significantly different depending on the types of inflammation. Treg expression of ST2, a receptor for alarmin IL-33, was predominantly associated with eosinophilic inflammation and tissue residency. Nevertheless, Treg-specific ST2 deficiency did not affect the development of eosinophilic allergic inflammation or the generation of lung-resident Tregs. These results uncover a stark heterogeneity among Tregs infiltrating the lungs during allergic airway inflammation. The results indicate that varying types of inflammation may give rise to phenotypically distinct lung-resident Tregs, underscoring a (to our knowledge) novel mechanism by which inflammatory cues may shape the composition of infiltrating Tregs, allowing them to regulate inflammatory responses through tissue-adapted mechanisms.

Formulation of an ovarian cancer vaccine with the squalene-based AddaVax adjuvant inhibits the growth of murine epithelial ovarian carcinomas.

Purpose: Epithelial ovarian carcinoma (EOC) is the most lethal of all human gynecologic malignancies. We previously reported that vaccination of female mice with the extracellular domain of anti-Müllerian hormone receptor II (AMHR2-ED) in complete Freund's adjuvant (CFA) generates AMHR2-ED specific immunoglobulin G (IgG) that provides prevention and therapy against murine EOCs. Although CFA is the "gold standard" adjuvant in animal studies, it is not approved for human use because it often induces painful granulomas and abscesses. Thus, the objective of this study is to identify an alternative adjuvant to CFA for use in our ovarian cancer vaccine clinical trials. Materials and Methods: Because it has been used successfully without serious adverse effects in numerous human clinical trials, we selected the IgG-inducing squalene-based adjuvant, AddaVax™, for evaluation of its ability to facilitate vaccine-induced prevention and treatment of EOC in mice. To this end, we immunized female C57BL/6 mice with recombinant mouse AMHR2-ED emulsified with either AddaVax or CFA as adjuvant and compared the results. Results: We found that formulation of the AMHR2-ED vaccine with AddaVax adjuvant induced high serum titers of IgG and significant inhibition of EOC growth with significantly enhanced overall survival of mice using both prevention and therapeutic protocols. These results were compared favorably with results obtained using CFA as an adjuvant in the AMHR2-ED vaccine. Conclusion: Our data indicate that the AMHR2-ED vaccine formulated with AddaVax may be used in human clinical trials and thereby serve as a novel and effective way to control human EOC.

Molecular Signature of Antibody-Mediated Chronic Vasculopathy in Heart Allografts in a Novel Mouse Model.

Cardiac allograft vasculopathy (CAV) limits the long-term success of heart transplants. Generation of donor-specific antibodies (DSAs) is associated with increased incidence of CAV clinically, but mechanisms underlying development of this pathology remain poorly understood. Major histocompatibility complex-mismatched A/J cardiac allografts in B6.CCR5-/- recipients have been reported to undergo acute rejection with little T-cell infiltration, but intense deposition of C4d in large vessels and capillaries of the graft accompanied by high titers of DSA. This model was modified to investigate mechanisms of antibody-mediated CAV by transplanting A/J hearts to B6.CCR5-/- CD8-/- mice that were treated with low doses of anti-CD4 monoclonal antibody to decrease T-cell-mediated graft injury and promote antibody-mediated injury. Although the mild inhibition of CD4 T cells extended allograft survival, the grafts developed CAV with intense C4d deposition and macrophage infiltration by 14 days after transplantation. Development of CAV correlated with recipient DSA titers. Transcriptomic analysis of microdissected allograft arteries identified the Notch ligand Dll4 as the most elevated transcript in CAV, associated with high versus low titers of DSA. More importantly, these analyses revealed a differential expression of transcripts in the CAV lesions compared with the matched apical tissue that lacks large arteries. In conclusion, these findings report a novel model of antibody-mediated CAV with the potential to facilitate further understanding of the molecular mechanisms promoting development of CAV.

Spontaneous CD4+ T Cell Activation and Differentiation in Lupus-Prone B6.Nba2 Mice Is IFNAR-Independent.

Systemic lupus erythematosus (SLE) is an autoimmune disorder characterized by dysregulated T and B lymphocytes. Type I interferons (IFN-I) have been shown to play important pathogenic roles in both SLE patients and mouse models of lupus. Recent studies have shown that B cell intrinsic responses to IFN-I are enough to drive B cell differentiation into autoantibody-secreting memory B cells and plasma cells, although lower levels of residual auto-reactive cells remain present. We speculated that IFN-I stimulation of T cells would similarly drive specific T-cell associated lupus phenotypes including the upregulation of T follicular helper cells and Th17, thereby affecting autoantibody production and the development of glomerulonephritis. Using the B6.Nba2 mouse model of lupus, we evaluated disease parameters in T cell specific IFN-I receptor (IFNAR)-deficient mice (cKO). Surprisingly, all measured CD4+ T cell abnormalities and associated intra-splenic cytokine levels (IFNγ, IL-6, IL-10, IL-17, IL-21) were unchanged and thus independent of IFN-I. In contrast B6.Nba2 cKO mice displayed reduced levels of effector CD8+ T cells and increased levels of Foxp3+ CD8+ regulatory T cells, suggesting that IFN-I induced signaling specifically affecting CD8+ T cells. These data suggest a role for both pathogenic and immunosuppressive CD8+ T cells in Nba2-driven autoimmunity, providing a model to further evaluate the role of these cell subsets during lupus-like disease development in vivo.

eIF2A-knockout mice reveal decreased life span and metabolic syndrome.

Eukaryotic initiation factor 2A (eIF2A) is a 65 kDa protein that functions in minor initiation pathways, which affect the translation of only a subset of messenger ribonucleic acid (mRNAs), such as internal ribosome entry site (IRES)-containing mRNAs and/or mRNAs harboring upstream near cognate/non-AUG start codons. These non-canonical initiation events are important for regulation of protein synthesis during cellular development and/or the integrated stress response. Selective eIF2A knockdown in cellular systems significantly inhibits translation of such mRNAs, which rely on alternative initiation mechanisms for their translation. However, there exists a gap in our understanding of how eIF2A functions in mammalian systems in vivo (on the organismal level) and ex vivo (in cells). Here, using an eIF2A-knockout (KO) mouse model, we present evidence implicating eIF2A in the biology of aging, metabolic syndrome and central tolerance. We discovered that eIF2A-KO mice have reduced life span and that eIF2A plays an important role in maintenance of lipid homeostasis, the control of glucose tolerance, insulin resistance and also reduces the abundance of B lymphocytes and dendritic cells in the thymic medulla of mice. We also show the eIF2A KO affects male and female mice differently, suggesting that eIF2A may affect sex-specific pathways. Interestingly, our experiments involving pharmacological induction of endoplasmic reticulum (ER) stress with tunicamycin did not reveal any substantial difference between the response to ER stress in eIF2A-KO and wild-type mice. The identification of eIF2A function in the development of metabolic syndrome bears promise for the further identification of specific eIF2A targets responsible for these changes.

S100a9 Protects Male Lupus-Prone NZBWF1 Mice From Disease Development.

Systemic lupus erythematosus (SLE) is an autoimmune disorder disproportionally affecting women. A similar sex difference exists in the murine New Zealand Black/White hybrid model (NZBWF1) of SLE with all females, but only 30-40% of males, developing disease within the first year of life. Myeloid-derived suppressor cells (MDSCs) are prominent in NZBWF1 males and while depletion of these cells in males, but not females, promotes disease development, the mechanism of suppression remains unknown. S100a9, expressed by neutrophils and MDSCs, has previously been shown to exert immunosuppressive functions in cancer and inflammation. Here we investigated if S100a9 exerts immunosuppressive functions in NZBWF1 male and female mice. S100a9+/+, S100a9+/- and S100a9-/- NZBWF1 mice were followed for disease development for up to 8 months of age. Serum autoantibody levels, splenomegaly, lymphocyte activation, glomerulonephritis and proteinuria were measured longitudinally or at the time of harvest. In accordance with an immunosuppressive function of MDSCs in male mice, S100a9-deficient male NZBWF1 mice developed accelerated autoimmunity as indicated by increased numbers of differentiated effector B and T cells, elevated serum autoantibody levels, increased immune-complex deposition and renal inflammation, and accelerated development of proteinuria. In contrast, female mice showed either no response to S100a9-deficiency or even a slight reduction in disease symptoms. Furthermore, male, but not female, S100a9-/- NZBWF1 mice displayed an elevated type I interferon-induced gene signature, suggesting that S100a9 may dampen a pathogenic type I interferon signal in male mice. Taken together, S100a9 exerts an immunosuppressive function in male NZBWF1 mice effectively moderating lupus-like disease development via inhibition of type I interferon production, lymphocyte activation, autoantibody production and the development of renal disease.

Recipient myeloperoxidase-producing cells regulate antibody-mediated acute versus chronic kidney allograft rejection.

Antibody-mediated rejection (ABMR) continues to be a major problem undermining the success of kidney transplantation. Acute ABMR of kidney grafts is characterized by neutrophil and monocyte margination in the tubular capillaries and by graft transcripts indicating NK cell activation, but the myeloid cell mechanisms required for acute ABMR have remained unclear. Dysregulated donor-specific antibody (DSA) responses with high antibody titers are induced in B6.CCR5-/- mice transplanted with complete MHC-mismatched A/J kidneys and are required for rejection of the grafts. This study tested the role of recipient myeloid cell production of myeloperoxidase (MPO) in the cellular and molecular components of acute ABMR. Despite induction of equivalent DSA titers, B6.CCR5-/- recipients rejected A/J kidneys between days 18 and 25, with acute ABMR, whereas B6.CCR5-/-MPO-/- recipients rejected the grafts between days 46 and 54, with histopathological features of chronic graft injury. On day 15, myeloid cells infiltrating grafts from B6.CCR5-/- and B6.CCR5-/-MPO-/- recipients expressed marked phenotypic and functional transcript differences that correlated with the development of acute versus chronic allograft injury, respectively. Near the time of peak DSA titers, activation of NK cells to proliferate and express CD107a was decreased within allografts in B6.CCR5-/-MPO-/- recipients. Despite high titers of DSA, depletion of neutrophils reproduced the inhibition of NK cell activation and decreased macrophage infiltration but increased monocytes producing MPO. Overall, recipient myeloid cells producing MPO regulate graft-infiltrating monocyte/macrophage function and NK cell activation that are required for DSA-mediated acute kidney allograft injury, and their absence switches DSA-mediated acute pathology and graft outcomes to chronic ABMR.

Development of sacral/buttock retiform purpura as an ominous presenting sign of COVID-19 and clinical and histopathologic evolution during severe disease course.

Retiform purpura has been described as a relatively frequent cutaneous finding in patients with coronavirus disease 2019 (COVID-19). The etiology is hypothesized to be related to thrombotic vasculopathy based on lesional biopsy specimen findings, but the pathogenesis of the vasculopathy is not completely understood. Here, we present a case of a retiform purpuric patch on the sacrum/buttocks in a hospitalized patient prior to subsequent diagnosis of COVID-19 and an eventual fatal disease course. Two lesional biopsy specimens at different time points in the disease course revealed thrombotic vasculopathy, despite therapeutic anticoagulation. Detailed histopathologic evaluation using immunohistochemical markers suggest the etiology of the vasculopathy involves both persistent complement activation and platelet aggregation, which possibly promote ongoing thrombus formation. This case highlights that sacral/buttock retiform purpuric patches may be a presenting sign of infection with SARS-CoV-2 virus and may represent an ominous sign supporting a future severe disease course. In addition, biopsy specimen findings at separate time points demonstrate that cutaneous vasculopathy may persist despite adequate systemic anticoagulation, possibly due to the combination of persistent complement and platelet activation. Finally, occlusive thrombi in sacral/buttock retiform purpuric patches may contribute to future ulceration and significant cutaneous morbidity in patients who survive COVID-19.

Cutting Edge: Myosin 18A Is a Novel Checkpoint Regulator in B Cell Differentiation and Antibody-Mediated Immunity.

We investigated the function of the newly discovered myosin family protein myosin 18A (Myo18A) in Ab-mediated immunity by generating B cell-conditional Myo18A-deficient mice. Myo18A deficiency led to expansion of bone marrow progenitor B cells and mature B cells in secondary lymphoid organs. Myo18A-deficient mice displayed serum IgM hyperglobulinemia and increased splenic IgM-secreting cells, with older mice switching to IgG1 hyperglobulinemia and autoantibody development. Immunization of Myo18A-deficient mice with inactivated influenza virus led to development of more potent neutralizing Abs against the major Ag hemagglutinin, associated with persistent accumulation of Ag-specific germinal center B cells and more Ag-specific bone marrow plasma cells. In vitro stimulation with TLR7 and BCR ligands revealed a greater ability of Myo18A-deficient B cells to differentiate into Ab-secreting cells, associated with higher AID and Blimp-1 expression. Overall, our study demonstrates that Myo18A is a novel negative regulator of B cell homeostasis, differentiation, and humoral immunity.

Early T cell infiltration is modulated by programed cell death-1 protein and its ligand (PD-1/PD-L1) interactions in murine kidney transplants.

Allogeneic transplants elicit dynamic T cell responses that are modulated by positive and negative co-stimulatory receptors. Understanding mechanisms that intrinsically modulate the immune responses to transplants is vital to develop rational treatment for rejection. Here, we have investigated the impact of programed cell death-1 (PD-1) protein, a negative co-stimulatory receptor, on the rejection of MHC incompatible kidney transplants in mice. T cells were found to rapidly infiltrate the kidneys of A/J mice transplanted to C57BL/6 mice, which peaked at six days and decline by day 14. The T cells primarily encircled tubules with limited infiltration of the tubular epithelium. Lipocalin 2 (LCN2), a marker of tubular injury, also peaked in the urine at day six and then declined. Notably, flow cytometry demonstrated that most of the T cells expressed PD-1 (over 90% of CD8 and about 75% of CD4 cells) at day six. Administration of blocking antibody to PD-L1, the ligand for PD-1, before day six increased T cell infiltrates and urinary LCN2, causing terminal acute rejection. In contrast, blocking PD-1/PD-L1 interactions after day six caused only a transient increase in urinary LCN2. Depleting CD4 and CD8 T cells virtually eliminated LCN2 in the urine in support of T cells injuring tubules. Thus, our data indicate that PD-1/PD-L1 interactions are not just related to chronic antigenic stimulation of T cells but are critical for the regulation of acute T cell responses to renal transplants.

Anti-inflammatory Roles of Glucocorticoids Are Mediated by Foxp3+ Regulatory T Cells via a miR-342-Dependent Mechanism.

Glucocorticoids (GC) are the mainstay treatment option for inflammatory conditions. Despite the broad usage of GC, the mechanisms by which GC exerts its effects remain elusive. Here, utilizing murine autoimmune and allergic inflammation models, we report that Foxp3+ regulatory T (Treg) cells are irreplaceable GC target cells in vivo. Dexamethasone (Dex) administered in the absence of Treg cells completely lost its ability to control inflammation, and the lack of glucocorticoid receptor in Treg cells alone resulted in the loss of therapeutic ability of Dex. Mechanistically, Dex induced miR-342-3p specifically in Treg cells and miR-342-3p directly targeted the mTORC2 component, Rictor. Altering miRNA-342-3p or Rictor expression in Treg cells dysregulated metabolic programming in Treg cells, controlling their regulatory functions in vivo. Our results uncover a previously unknown contribution of Treg cells during glucocorticoid-mediated treatment of inflammation and the underlying mechanisms operated via the Dex-miR-342-Rictor axis.

High-fat diet-induced GAIT element-mediated translational silencing of mRNAs encoding inflammatory proteins in macrophage protects against atherosclerosis.

Previously, we identified a mechanism of inflammation control directed by ribosomal protein L13a and "GAIT" (Gamma Activated Inhibitor of Translation) elements in target mRNAs and showed that its elimination in myeloid cell-specific L13a knockout mice (L13a KO) increased atherosclerosis susceptibility and severity. Here, we investigated the mechanistic basis of this endogenous defense against atherosclerosis. We compared molecular and cellular aspects of atherosclerosis in high-fat diet (HFD)-fed L13a KO and intact (control) mice. HFD treatment of control mice induced release of L13a from 60S ribosome, formation of RNA-binding complex, and subsequent GAIT element-mediated translational silencing. Atherosclerotic plaques from HFD-treated KO mice showed increased infiltration of M1 type inflammatory macrophages. Macrophages from KO mice showed increased phagocytic activity and elevated expression of LDL receptor and pro-inflammatory mediators. NanoString analysis of the plaques from KO mice showed upregulation of a number of mRNAs encoding inflammatory proteins. Bioinformatics analysis suggests the presence of the potential GAIT elements in the 3'UTRs of several of these mRNAs. Macrophage induces L13a/GAIT-dependent translational silencing of inflammatory genes in response to HFD as an endogenous defense against atherosclerosis in ApoE-/- model.

IL-27 targets Foxp3+ Tregs to mediate antiinflammatory functions during experimental allergic airway inflammation.

Foxp3+ CD4 Tregs are central regulators of inflammation, including allergic inflammation in the lung. There is increasing evidence that inflammatory factors undermine adequate Treg functions and homeostasis, resulting in prolonged and exacerbated inflammation. Therefore, identifying the factors is of the utmost important. IL-27 is an antiinflammatory cytokine implicated in immune regulation and tolerance. However, the cellular mechanisms underlying IL-27-mediated immune regulation in vivo remain largely unknown. Utilizing a cockroach antigen-induced allergic inflammation model in mice, we sought to test the roles of Tregs during IL-27-mediated regulation of allergic inflammation. Intranasally delivered IL-27 significantly reduced the development of airway inflammation. Unexpectedly, the IL-27-induced reduction occurred only in the presence of Tregs. Il27ra-/- and Treg-specific Il27ra-/- mice developed severe airway inflammation, and IL-27 treatment had little impact on diminishing the inflammatory responses. IL-27-induced treatment was restored following transfer of WT Tregs but not of Tregs deficient in Lag3, a molecule induced by IL-27 in Tregs. Finally, Tregs from asthmatic patients exhibited blunted STAT1 phosphorylation following IL-27 stimulation. Taken together, our results uncover that Tregs are the primary target cells of IL-27 in vivo to mediate its antiinflammatory functions, suggesting that altered IL-27 responsiveness in Tregs may underlie inadequate Treg functions and perpetuation of inflammation.

Neutrophil Cathepsin G Regulates Dendritic Cell Production of IL-12 during Development of CD4 T Cell Responses to Antigens in the Skin.

Contact hypersensitivity (CHS) is a CD8 T cell-mediated response to hapten skin sensitization and challenge. Sensitization of wild-type (WT) mice induces hapten-reactive effector CD8 T cells producing IFN-γ and IL-17- and IL-4-producing CD4 T cells that cannot mediate CHS. Although CXCR2-dependent Ly6G+ (neutrophil) cell recruitment into hapten-challenged skin is required to direct effector CD8 T cell infiltration into the challenge site to elicit CHS, 2,4-dinitrofluorobenezene (DNFB) sensitization of CXCR2-/- mice and neutrophil-depleted WT mice induced both hapten-reactive CD4 and CD8 T cells producing IFN-γ and IL-17. CD4 T cell-mediated CHS responses were not generated during DNFB sensitization of neutrophil-depleted WT mice treated with anti-IL-12 mAb or neutrophil-depleted IL-12-/- mice. Neutrophil depletion during DNFB sensitization of WT mice markedly increased IL-12-producing hapten-primed dendritic cell numbers in the skin-draining lymph nodes. Sensitization of mice lacking the neutrophil serine protease cathepsin G (CG)-induced hapten-reactive CD4 and CD8 T cells producing IFN-γ and IL-17 with elevated and elongated CHS responses to DNFB challenge. Induction of CHS effector CD4 T cells producing IFN-γ in neutrophil-depleted WT mice was eliminated by s.c. injection of active, but not inactivated, CG during sensitization. Thus, hapten skin sensitization induces neutrophil release of CG that systemically inhibits hapten-presenting dendritic cell production of IL-12 and the development of hapten-reactive CD4 T cells to IFN-γ-producing CHS effector cells.

Peritransplant VLA-4 blockade inhibits endogenous memory CD8 T cell infiltration into high-risk cardiac allografts and CTLA-4Ig resistant rejection.

Recipient endogenous memory CD8 T cells expressing reactivity to donor class I MHC infiltrate MHC-mismatched cardiac allografts within 24 hours after reperfusion and express effector functions mediating graft injury. The current study tested the efficacy of Very Late Antigen-4 (VLA-4) blockade to inhibit endogenous memory CD8 T cell infiltration into cardiac allografts and attenuate early posttransplant inflammation. Peritransplant anti-VLA-4 mAb given to C57BL6 (H-2b ) recipients of AJ (H-2a ) heart allografts completely inhibited endogenous memory CD4 and CD8 T cell infiltration with significant decrease in macrophage, but not neutrophil, infiltration into allografts subjected to either minimal or prolonged cold ischemic storage (CIS) prior to transplant, reduced intra-allograft IFN-γ-induced gene expression and prolonged survival of allografts subjected to prolonged CIS in CTLA-4Ig treated recipients. Anti-VLA-4 mAb also inhibited priming of donor-specific T cells producing IFN-γ until at least day 7 posttransplant. Peritransplant anti-VLA plus anti-CD154 mAb treatment similarly prolonged survival of allografts subjected to minimal or increased CIS prior to transplant. Overall, these data indicate that peritransplant anti-VLA-4 mAb inhibits early infiltration memory CD8 T cell infiltration into allografts with a marked reduction in early graft inflammation suggesting an effective strategy to attenuate negative effects of heterologous alloimmunity in recipients of higher risk grafts.

In the absence of natural killer cell activation donor-specific antibody mediates chronic, but not acute, kidney allograft rejection.

Antibody mediated rejection (ABMR) is a major barrier to long-term kidney graft survival. Dysregulated donor-specific antibody (DSA) responses are induced in CCR5-deficient mice transplanted with complete major histocompatibility complex (MHC)-mismatched kidney allografts, and natural killer (NK) cells play a critical role in graft injury and rejection. We investigated the consequence of high DSA titers on kidney graft outcomes in the presence or absence of NK cell activation within the graft. Equivalent serum DSA titers were induced in CCR5-deficient B6 recipients of complete MHC mismatched A/J allografts and semi-allogeneic (A/J x B6) F1 kidney grafts, peaking by day 14 post-transplant. A/J allografts were rejected between days 16-28, whereas B6 isografts and semi-allogeneic grafts survived past day 65. On day 7 post-transplant, NK cell infiltration into A/J allografts was composed of distinct populations expressing high and low levels of the surface antigen NK1.1, with NK1.1low cells reflecting the highest level of activation. These NK cell populations increased with time post-transplant. In contrast, NK cell infiltration into semi-allogeneic grafts on day 7 was composed entirely of NK1.1high cells that decreased thereafter. On day 65 post-transplant the semi-allogeneic grafts had severe interstitial fibrosis, glomerulopathy, and arteriopathy, accompanied by expression of pro-fibrogenic genes. These results suggest that NK cells synergize with DSA to cause acute kidney allograft rejection, whereas high DSA titers in the absence of NK cell activation cannot provoke acute ABMR but instead induce the indolent development of interstitial fibrosis and glomerular injury that leads to late graft failure.

Targeting CD6 for the treatment of experimental autoimmune uveitis.

OBJECTIVE: CD6 is emerging as a new target for treating many pathological conditions in which T cells are integrally involved, but even the latest data from studies of CD6 gene engineered mice were still contradictory. To address this issue, we studied experimental autoimmune uveitis (EAU), a model of autoimmune uveitis, in wild-type (WT) and CD6 knockout (KO) mice. METHODS: After EAU induction in WT and CD6 KO mice, we evaluated ocular inflammation and compared retinal antigen-specific T-cell responses using scanning laser ophthalmoscopy, spectral-domain optical coherence tomography, histopathology, and T cell recall assays. Uveitogenic T cells from WT and CD6 KO mice were adoptively transferred into WT naïve mice to confirm the impact of CD6 on T cells. In addition, we immunized CD6 KO mice with recombinant CD6 protein to develop mouse anti-mouse CD6 monoclonal antibodies (mAbs) in which functional antibodies exhibiting cross-reactivity with human CD6 were screened and identified for treatment studies. RESULTS: In CD6 KO mice with EAU, we found significantly decreased retinal inflammation and reduced autoreactive T-cell responses, and confirmed the impaired uveitogenic capacity of T cells from these mice in an adoptive transfer experiment. Notably, one of these cross-reactive mAbs significantly ameliorated retinal inflammation in EAU induced by the adoptive transfer of uveitogenic T cells. CONCLUSIONS: Together, these data strongly suggest that CD6 plays a previously unknown, but pivotal role in autoimmune uveitis, and may be a promising new treatment target for this blinding disease. In addition, the newly developed mouse anti-mouse/human CD6 mAbs could be valuable tools for testing CD6-targeted therapies in other mouse models of human diseases.

Primary Immunoprevention of Epithelial Ovarian Carcinoma by Vaccination against the Extracellular Domain of Anti-Müllerian Hormone Receptor II.

Epithelial ovarian carcinoma (EOC) is the most prevalent form of ovarian cancer in the United States, representing approximately 85% of all cases and causing more deaths than any other gynecologic malignancy. We propose that optimized control of EOC requires the incorporation of a vaccine capable of inducing safe and effective preemptive immunity in cancer-free women. In addition, we hypothesize that ovarian-specific self-proteins that are "retired" from autoimmune-inducing expression levels as ovaries age but are expressed at high levels in emerging EOC may serve as vaccine targets for mediating safe and effective primary immunoprevention. Here, we show that expression of the extracellular domain of anti-Müllerian hormone receptor II (AMHR2-ED) in normal tissues is confined exclusively to the human ovary, drops to nonautoimmune inducing levels in postmenopausal ovaries, and is at high levels in approximately 90% of human EOC. We found that AMHR2-ED vaccination significantly inhibits growth of murine EOC and enhances overall survival without inducing oophoritis in aged female mice. The observed inhibition of EOC growth was mediated substantially by induction of AMHR2-ED-specific IgG antibodies that agonize receptor signaling of a Bax/caspase-3-dependent proapoptotic cascade. Our results indicate that AMHR2-ED vaccination may be particularly useful in providing safe and effective preemptive immunity against EOC in women at high genetic or familial risk who have the greatest need for a preventive vaccine and ultimately in cancer-free postmenopausal women who account for 75% of all EOC cases. Cancer Prev Res; 10(11); 612-24. ©2017 AACRSee related editorial by Shoemaker et al., p. 607.

Lung-Infiltrating Foxp3+ Regulatory T Cells Are Quantitatively and Qualitatively Different during Eosinophilic and Neutrophilic Allergic Airway Inflammation but Essential To Control the Inflammation.

Understanding functions of Foxp3+ regulatory T cells (Tregs) during allergic airway inflammation remains incomplete. In this study, we report that, during cockroach Ag-induced allergic airway inflammation, Foxp3+ Tregs are rapidly mobilized into the inflamed lung tissues. However, the level of Treg accumulation in the lung was different depending on the type of inflammation. During eosinophilic airway inflammation, ∼30% of lung-infiltrating CD4 T cells express Foxp3, indicative of Tregs. On the contrary, only ∼10% of infiltrating CD4 T cells express Foxp3 during neutrophilic airway inflammation. Despite the different accumulation, the lung inflammation and inflammatory T cell responses were aggravated following Treg depletion, regardless of the type of inflammation, suggesting regulatory roles for Tregs. Interestingly, however, the extent to which inflammatory responses are aggravated by Treg depletion was significantly greater during eosinophilic airway inflammation. Indeed, lung-infiltrating Tregs exhibit phenotypic and functional features associated with potent suppression. Our results demonstrate that Tregs are essential regulators of inflammation, regardless of the type of inflammation, although the mechanisms used by Tregs to control inflammation may be shaped by environmental cues available to them.

Treg-specific IL-27Rα deletion uncovers a key role for IL-27 in Treg function to control autoimmunity.

Dysregulated Foxp3+ Treg functions result in uncontrolled immune activation and autoimmunity. Therefore, identifying cellular factors modulating Treg functions is an area of great importance. Here, using Treg-specific Il27ra-/- mice, we report that IL-27 signaling in Foxp3+ Tregs is essential for Tregs to control autoimmune inflammation in the central nervous system (CNS). Following experimental autoimmune encephalomyelitis (EAE) induction, Treg-specific Il27ra-/- mice develop more severe EAE. Consistent with the severe disease, the numbers of IFNγ- and IL-17-producing CD4 T cells infiltrating the CNS tissues are greater in these mice. Treg accumulation in the inflamed CNS tissues is not affected by the lack of IL-27 signaling in Tregs, suggesting a functional defect of Il27ra-/- Tregs. IL-10 production by conventional CD4 T cells and their CNS accumulation are rather elevated in Treg-specific Il27ra-/- mice. Analysis with Treg fate-mapping reporter mice further demonstrates that IL-27 signaling in Tregs may control stability of Foxp3 expression. Finally, systemic administration of recombinant IL-27 in Treg-specific Il27ra-/- mice fails to ameliorate the disease even in the presence of IL-27-responsive conventional CD4 T cells. These findings uncover a previously unknown role of IL-27 in regulating Treg function to control autoimmune inflammation.