Characterization of CD8+ T cells in immune-privileged organs of ZIKV-infected Ifnar1-/- mice.

Zika virus (ZIKV) infection caused neurological complications and male infertility, leading to the accumulation of antigen-specific immune cells in immune-privileged organs (IPOs). Thus, it is important to understand the immunological responses to ZIKV in IPOs. We extensively investigated the ZIKV-specific T cell immunity in IPOs in Ifnar1-/- mice, based on an immunodominant epitope E294-302 tetramer. The distinct kinetics and functions of virus-specific CD8+ T cells infiltrated into different IPOs were characterized, with late elevation in the brain and spinal cord. Single epitope E294-302-specific T cells can account for 20-60% of the total CD8+ T cells in the brain, spinal cord, and testicle and persist for at least 90 days in the brain and spinal cord. The E294-302-specific TCRαßs within the IPOs are featured with the majority of clonotypes utilizing TRAV9N-3 paired with diverse TRBV chains, but with distinct αß paired clonotypes in 7 and 30 days post-infection. Specific chemokine receptors, Ccr2 and Ccr5, were selectively expressed in the E294-302-specific CD8+ T cells within the brain and testicle, indicating an IPO-oriented migration of virus-specific CD8+ T cells after infection. Overall, this study adds to the understanding of virus-specific CD8+ T cell responses for controlling and clearing ZIKV infection in IPOs.IMPORTANCEThe immune-privileged organs (IPOs), such as the central nervous system and testicles, presented pathogenicity and inflammation after Zika virus (ZIKV) infection with infiltrated CD8+ T cells. Our data show that CD8+ T cells keep up with virus increases and decreases in immune-privileged organs. Furthermore, our study provides the first ex vivo comparative analyses of the composition and diversity related to TCRα/ß clonotypes across anatomical sites and ZIKV infection phases. We show that the vast majority of TCRα/ß clonotypes in tissues utilize TRAV9N-3 with conservation. Specific chemokine expression, including Ccr2 and Ccr5, was found to be selectively expressed in the E294-302-specific CD8+ T cells within the brain and testicle, indicating an IPO-oriented migration of the virus-specific CD8+ T cells after the infection. Our study adds insights into the anti-viral immunological characterization and chemotaxis mechanism of virus-specific CD8+ T cells after ZIKV infection in different IPOs.

Interleukin-15 is a hair follicle immune privilege guardian.

The autoimmunity-promoting cytokine, Interleukin-15 (IL-15), is often claimed to be a key pathogenic cytokine in alopecia areata (AA). Yet, rhIL-15 promotes human hair follicle (HF) growth ex vivo. We have asked whether the expression of IL-15 and its receptor (IL-15R) isoforms is altered in human AA and how IL-15 impacts on human HF immune privilege (HF-IP) in the presence/absence of interferon-γ (IFNγ), the well-documented key AA-pathogenic cytokine, as well as on hair regrowth after experimental AA induction in vivo. Quantitative immunohistomorphometry showed the number of perifollicular IL-15+ T cells in AA skin biopsies to be significantly increased compared to healthy control skin, while IL-15, IL-15Rα, and IL-15Rγ protein expression within the hair bulb were significantly down-regulated in AA HFs. In organ-cultured human scalp HFs, rhIL-15 significantly reduced hair bulb expression of MICA, the key "danger" signal in AA pathogenesis, and increased production of the HF-IP guardian, α-MSH. Crucially, ex vivo, rhIL-15 prevented IFNγ-induced HF-IP collapse, restored a collapsed HF-IP by IL-15Rα-dependent signaling (as documented by IL-15Rα-silencing), and protected AA-preventive immunoinhibitory iNKT10 cells from IFNγ-induced apoptosis. rhIL-15 even promoted hair regrowth after experimental AA induction in human scalp skin xenotransplants on SCID/beige mice in vivo. Our data introduce IL-15 as a novel, functionally important HF-IP guardian whose signaling is constitutively defective in scalp HFs of AA patients. Our data suggest that selective stimulation of intrafollicular IL-15Rα signaling could become a novel therapeutic approach in AA management, while blocking it pharmacologically may hinder both HF-IP restoration and hair re-growth and may thus make HFs more vulnerable to AA relapse.

Pathogenesis of Alopecia Areata and Vitiligo: Commonalities and Differences.

Both alopecia areata (AA) and vitiligo are distinct, heterogenous, and complex disease entities, characterized by nonscarring scalp terminal hair loss and skin pigment loss, respectively. In AA, inflammatory cell infiltrates are in the deep reticular dermis close to the hair bulb (swarm of bees), whereas in vitiligo the inflammatory infiltrates are in the epidermis and papillary dermis. Immune privilege collapse has been extensively investigated in AA pathogenesis, including the suppression of immunomodulatory factors (e.g., transforming growth factor-ß (TGF-ß), programmed death-ligand 1 (PDL1), interleukin-10 (IL-10), α-melanocyte-stimulating hormone (α-MSH), and macrophage migration inhibitory factor (MIF)) and enhanced expression of the major histocompatibility complex (MHC) throughout hair follicles. However, immune privilege collapse in vitiligo remains less explored. Both AA and vitiligo are autoimmune diseases that share commonalities in pathogenesis, including the involvement of plasmacytoid dendritic cells (and interferon-α (IFN- α) signaling pathways) and cytotoxic CD8+ T lymphocytes (and activated IFN-γ signaling pathways). Blood chemokine C-X-C motif ligand 9 (CXCL9) and CXCL10 are elevated in both diseases. Common factors that contribute to AA and vitiligo include oxidative stress, autophagy, type 2 cytokines, and the Wnt/ß-catenin pathway (e.g., dickkopf 1 (DKK1)). Here, we summarize the commonalities and differences between AA and vitiligo, focusing on their pathogenesis.

Dandruff lesional scalp skin exhibits epidermal T cell infiltration and a weakened hair follicle immune privilege.

OBJECTIVE: Dandruff is characterised by the presence of perivascular leukocytes and mild inflammation; however, the immune microenvironment of dandruff-affected scalp skin and the potential changes to the hair follicle's (HF) physiological immune privilege (HF IP) remain unknown. Here, we characterised the HF immune microenvironment and immune privilege status in dandruff-affected scalp skin. METHODS: We assessed relevant key parameters in healthy versus dandruff-affected human scalp biopsies using quantitative immunohistomorphometry, laser capture microdissection, and RNA sequencing. RESULTS: The number of epidermal CD4+ and CD8+ T cells was increased in lesional dandruff scalp skin, while the number of MHC class II+/CD1a+ Langerhans cells was decreased in the infundibulum. The number of intrafollicular and perifollicular CD4+ T cells and CD8+ T cells, perifollicular CD68+ macrophages, and tryptase+ mast cells remained unchanged. Interestingly, MHC class Ia and ß2-microglobulin protein expression were significantly increased specifically in the suprabulbar outer root sheath (ORS) compartment of dandruff-associated HFs. RNAseq analysis of laser capture micro-dissected suprabulbar ORS compartment revealed antigen presentation pathway as the top regulated canonical pathway, along with the upregulation of HF-IP genes such as HLA-C, HLA-DP, and TAP1, which are normally down-regulated in healthy HFs. Intrafollicular protein expression of known HF IP guardians (CD200 and α-MSH) and 'danger signals' (MICA and CXCL10) remained unaltered at the IP sites of dandruff lesional HFs compared to non-lesional and healthy HFs. Instead, the expression of macrophage migration inhibiting factor (MIF), another HF IP guardian, was reduced. CONCLUSION: Together, this work shows that dandruff is associated with epidermal T-cell infiltration and a weakened HF IP in the suprabulbar ORS of HFs in dandruff lesional scalp.

OBJECTIF: Les pellicules sont caractérisées par la présence de leucocytes périvasculaires et une légère inflammation. Cependant, le microenvironnement immunitaire de la peau du cuir chevelu affectée par les pellicules et les modifications potentielles du privilège immunitaire physiologique du follicule pileux (PI FP) restent inconnus. Ici, nous avons caractérisé le microenvironnement immunitaire du follicule pileux (FP) et l'état du privilège immunitaire de la peau du cuir chevelu affectée par les pellicules. MÉTHODES: Nous avons évalué les principaux paramètres pertinents dans des biopsies de cuir chevelu humain sain par rapport à ceux touchés par les pellicules, à l'aide d'une immuno­histomorphométrie quantitative, d'une microdissection au laser et d'un séquençage de l'ARN. RÉSULTATS: Le nombre de lymphocytes T CD4+ et CD8+ épidermiques a augmenté dans la peau du cuir chevelu atteinte de pellicules lésionnelles, tandis que le nombre de cellules de Langerhans du CMH de classe II+/CD1a+ a diminué dans l'infundibulum. Le nombre de lymphocytes T CD4+ et de lymphocytes T CD8+ intrafolliculaires et périfolliculaires, de macrophages CD68+ périfolliculaires et de mastocytes tryptase+ est resté inchangé. Il est intéressant de noter que l'expression des protéines du CMH de classe Ia et de la ß2­microglobuline a augmenté de manière significative dans le compartiment suprabulbaire de la gaine radiculaire externe (GRE) en particulier des FP associés aux pellicules. L'analyse par séquençage ARN du compartiment suprabulbaire de la GRE micro­disséquée au laser a révélé que la voie de présentation de l'antigène était la voie canonique la plus régulée, ainsi que la régulation à la hausse des gènes PI­FP tels que HLA­C, HLA­DP et TAP1, qui sont normalement régulés à la baisse dans les FP sains. L'expression protéique intrafolliculaire des gardiens connus du PI FP (CD200 et α­MSH) et des « signaux de danger ¼ (MICA et CXCL10) est restée inchangée au niveau des sites du PI des FP à pellicules lésionnelles par rapport aux FP sans pellicules lésionnelles et sains. En revanche, l'expression du facteur d'inhibition de la migration des macrophages (MIF), un autre gardien du PI FP, a été réduite. CONCLUSION: L'ensemble de ces travaux montrent que les pellicules sont associées à une infiltration épidermique des lymphocytes T et à un affaiblissement du PI FP dans la GRE suprabulbaire des FP du cuir chevelu atteint de pellicules lésionnelles.

CNS infection and immune privilege.

Classically, the CNS is described as displaying immune privilege, as it shows attenuated responses to challenge by alloantigen. However, the CNS does show local inflammation in response to infection. Although pathogen access to the brain parenchyma and retina is generally restricted by physiological and immunological barriers, certain pathogens may breach these barriers. In the CNS, such pathogens may either cause devastating inflammation or benefit from immune privilege in the CNS, where they are largely protected from the peripheral immune system. Thus, some pathogens can persist as latent infections and later be reactivated. We review the consequences of immune privilege in the context of CNS infections and ask whether immune privilege may provide protection for certain pathogens and promote their latency.

Immune Privileges as a Result of Mutual Regulation of Immune and Stem Systems.

Immune privileges of cancer stem cells is a well-known and widely studied problem, as presence of such cells in tumors is associated with refractoriness, recurrence, and metastasis. Accumulating evidence also suggests presence of immune privileges in non-pathological stem cells in addition to their other defense mechanisms against damaging factors. This similarity between pathological and normal stem cells raises the question of why stem cells have such a potentially dangerous property. Regulation of vital processes of autoimmunity control and regeneration realized through interactions between immune cells, stem cells, and their microenvironment are reviewed in this work as causes of formation of the stem cell immune privilege. Deep mutual integration between regulations of stem and immune cells is noted. Considering diversity and complexity of mutual regulation of stem cells, their microenvironment, and immune system, I suggest the term "stem system".

Ocular Vascular Diseases: From Retinal Immune Privilege to Inflammation.

The eye is an immune privileged tissue that insulates the visual system from local and systemic immune provocation to preserve homeostatic functions of highly specialized retinal neural cells. If immune privilege is breached, immune stimuli will invade the eye and subsequently trigger acute inflammatory responses. Local resident microglia become active and release numerous immunological factors to protect the integrity of retinal neural cells. Although acute inflammatory responses are necessary to control and eradicate insults to the eye, chronic inflammation can cause retinal tissue damage and cell dysfunction, leading to ocular disease and vision loss. In this review, we summarized features of immune privilege in the retina and the key inflammatory responses, factors, and intracellular pathways activated when retinal immune privilege fails, as well as a highlight of the recent clinical and research advances in ocular immunity and ocular vascular diseases including retinopathy of prematurity, age-related macular degeneration, and diabetic retinopathy.

Acquisition of Immune Privilege in GBM Tumors: Role of Prostaglandins and Bile Salts.

Based on the postulate that glioblastoma (GBM) tumors generate anti-inflammatory prostaglandins and bile salts to gain immune privilege, we analyzed 712 tumors in-silico from three GBM transcriptome databases for prostaglandin and bile synthesis/signaling enzyme-transcript markers. A pan-database correlation analysis was performed to identify cell-specific signal generation and downstream effects. The tumors were stratified by their ability to generate prostaglandins, their competency in bile salt synthesis, and the presence of bile acid receptors nuclear receptor subfamily 1, group H, member 4 (NR1H4) and G protein-coupled bile acid receptor 1 (GPBAR1). The survival analysis indicates that tumors capable of prostaglandin and/or bile salt synthesis are linked to poor outcomes. Tumor prostaglandin D2 and F2 syntheses are derived from infiltrating microglia, whereas prostaglandin E2 synthesis is derived from neutrophils. GBMs drive the microglial synthesis of PGD2/F2 by releasing/activating complement system component C3a. GBM expression of sperm-associated heat-shock proteins appears to stimulate neutrophilic PGE2 synthesis. The tumors that generate bile and express high levels of bile receptor NR1H4 have a fetal liver phenotype and a RORC-Treg infiltration signature. The bile-generating tumors that express high levels of GPBAR1 are infiltrated with immunosuppressive microglia/macrophage/myeloid-derived suppressor cells. These findings provide insight into how GBMs generate immune privilege and may explain the failure of checkpoint inhibitor therapy and provide novel targets for treatment.

Central nervous system zoning: How brain barriers establish subdivisions for CNS immune privilege and immune surveillance.

The central nervous system (CNS) coordinates all our body functions. Neurons in the CNS parenchyma achieve this computational task by high speed communication via electrical and chemical signals and thus rely on a strictly regulated homeostatic environment, which does not tolerate uncontrolled entry of blood components including immune cells. The CNS thus has a unique relationship with the immune system known as CNS immune privilege. Previously ascribed to the presence of blood-brain barriers and the lack of lymphatic vessels in the CNS parenchyma prohibiting, respectively, efferent and afferent connections with the peripheral immune system, it is now appreciated that CNS immune surveillance is ensured by cellular and acellular brain barriers that limit immune cell and mediator accessibility to specific compartments at the borders of the CNS. CNS immune privilege is established by a brain barriers anatomy resembling the architecture of a medieval castle surrounded by two walls bordering a castle moat. Built for protection and defense this two-walled rampart at the outer perimeter of the CNS parenchyma allows for accommodation of different immune cell subsets and efficient monitoring of potential danger signals derived from inside or outside of the CNS parenchyma. It enables effective mounting of immune responses within the subarachnoid or perivascular spaces, while leaving the CNS parenchyma relatively undisturbed. In this study, we propose that CNS immune privilege rests on the proper function of the brain barriers, which allow for CNS immune surveillance but prohibit activation of immune responses from the CNS parenchyma unless it is directly injured.

ARHGEF15 in Sertoli cells contributes to germ cell development and testicular immune privilege†.

Sertoli cells (SCs), the only somatic cells in the seminiferous tubules, facilitate the maintenance of testicular immune privilege through the formation of the blood-testis barrier (BTB) and the expression of immunoregulatory factors. Rho guanosine exchange factor 15 (ARHGEF15) is a member of the guanosine exchange factors, which are involved in cell migration, cell polarity, and cell cycle progression via activation of Rho GTPases. This study investigated the functional role of ARHGEF15 in SCs during spermatogenesis using SC-specific Arhgef15 knockout mice. The results revealed that Arhgef15 deficiency in SCs affected the localization of SC nuclei, disrupted BTB integrity, and led to premature shedding of germ cells. In Arhgef15flox/flox/Amh-Cre+ mice, the ultrastructure of the round spermatids was impaired, accompanied by acrosome degeneration, acrosomal vesicle shedding, and atrophic nuclei. Consequently, the percentage of abnormal sperm in the Arhgef15flox/flox/Amh-Cre+ epididymis was markedly elevated. RNA-sequencing analysis revealed that most of the differentially expressed genes in SCs of Arhgef15flox/flox/Amh-Cre+ mice were associated with immunity. Further study revealed that the sera of Arhgef15flox/flox/Amh-Cre+ mice showed immunoreactivity against testicular lysate of wild-type mice, indicating the production of antibodies against testicular autoantigens in Arhgef15flox/flox/Amh-Cre+ mice. In conclusion, the specific deletion of Arhgef15 in SCs of mice leads to sperm abnormality, probably by disrupting the testicular immune homeostasis.

Disruption of the blood-brain barrier in 22q11.2 deletion syndrome.

Neuroimmune dysregulation is implicated in neuropsychiatric disorders including schizophrenia. As the blood-brain barrier is the immunological interface between the brain and the periphery, we investigated whether this vascular phenotype is intrinsically compromised in the most common genetic risk factor for schizophrenia, the 22q11.2 deletion syndrome (22qDS). Blood-brain barrier like endothelium differentiated from human 22qDS+schizophrenia-induced pluripotent stem cells exhibited impaired barrier integrity, a phenotype substantiated in a mouse model of 22qDS. The proinflammatory intercellular adhesion molecule-1 was upregulated in 22qDS+schizophrenia-induced blood-brain barrier and in 22qDS mice, indicating compromise of the blood-brain barrier immune privilege. This immune imbalance resulted in increased migration/activation of leucocytes crossing the 22qDS+schizophrenia blood-brain barrier. We also found heightened astrocyte activation in murine 22qDS, suggesting that the blood-brain barrier promotes astrocyte-mediated neuroinflammation. Finally, we substantiated these findings in post-mortem 22qDS brain tissue. Overall, the barrier-promoting and immune privilege properties of the 22qDS blood-brain barrier are compromised, and this might increase the risk for neuropsychiatric disease.

Novel Insights into the Stemness and Immune Privilege of Mesenchymal Stem Cells from Human Wharton Jelly by Single-Cell RNA Sequencing.

BACKGROUND Fundamental and clinical interest in mesenchymal stem cells (MSCs) has risen dramatically over the past 3 decades. The immunomodulatory and differentiation abilities are the main mechanisms in vitro and in vivo. However, increasing evidence casts doubt on the stemness and immunogenicity of MSCs. MATERIAL AND METHODS We conducted a high-throughput 10x RNA sequencing and Smart-seq2 scRNA-seq analysis to reveal gene expression of Wharton jelly MSCs (WJ-MSCs) at a single-cell level. Multipotent differentiation, subpopulations, marker genes, human leucocyte antigen (HLA) gene expression, and cell cluster trajectory analysis were evaluated. RESULTS The WJ-MSCs had considerable heterogeneity between cells in terms of gene expression. They highly, partially, and hardly expressed genes related to mesodermal differentiation, endodermal differentiation, and ectodermal differentiation, respectively. Some cells seem to be bipotent or unipotent stem cells. Further, Monocle and cell cluster trajectory analysis demonstrated that 1 of the 3 divided clusters performed as stem cells, accounting for 12.6% of the population. The marker genes for a stem cell cluster were CRIM1, GLS, PLOD2, NEXN, ACTR2, FN1, MBNL1, LMOD1, COL3A1, NCL, SEC62, EPRS, COL5A2, COL8A1, and VCAN. In addition, the MSCs also highly, partially, and hardly expressed HLA-I antigen genes, HLA-II genes, and the HLA-G gene, respectively, indicating that MSCs probably have immunogenicity. A Kyoto Encyclopedia of Genes and Genomes pathway analysis of the 3 clusters demonstrated that they were mainly connected with viral infectious diseases, cancer, and endocrine and metabolic disorders. The most expressed transcription factors were zf-C2H2, HMG/HMGY, and Homeobox. CONCLUSIONS We found that only a subpopulation of WJ-MSCs are real stem cells and WJ-MSCs probably do not have immune privilege.

Photoreceptor Cells Constitutively Express IL-35 and Promote Ocular Immune Privilege.

Interleukin-27 is constitutively secreted by microglia in the retina or brain, and upregulation of IL-27 during neuroinflammation suppresses encephalomyelitis and autoimmune uveitis. However, while IL-35 is structurally and functionally similar to IL-27, the intrinsic roles of IL-35 in CNS tissues are unknown. Thus, we generated IL-35/YFP-knock-in reporter mice (p35-KI) and demonstrated that photoreceptor neurons constitutively secrete IL-35, which might protect the retina from persistent low-grade inflammation that can impair photoreceptor functions. Furthermore, the p35-KI mouse, which is hemizygous at the il12a locus, develops more severe uveitis because of reduced IL-35 expression. Interestingly, onset and exacerbation of uveitis in p35-KI mice caused by extravasation of proinflammatory Th1/Th17 lymphocytes into the retina were preceded by a dramatic decrease of IL-35, attributable to massive death of photoreceptor cells. Thus, while inflammation-induced death of photoreceptors and loss of protective effects of IL-35 exacerbated uveitis, our data also suggest that constitutive production of IL-35 in the retina might have housekeeping functions that promote sterilization immunity in the neuroretina and maintain ocular immune privilege.

Age-related changes in ocular mucosal tolerance: Lessons learned from gut and respiratory tract immunity.

The ocular surface is the part of the visual system directly exposed to the environment, and it comprises the cornea, the first refractive tissue layer and its surrounding structures. The ocular surface has evolved to keep the cornea smooth and wet, a prerequisite for proper sight, and also protected. To this aim, the ocular surface is a bona fide mucosal niche with an immune system capable of fighting against dangerous pathogens. However, due to the potential harmful effects of uncontrolled inflammation, the ocular surface has several mechanisms to keep the immune response in check. Specifically, the ocular surface is maintained inflammation-free and functional by a particular form of peripheral tolerance known as mucosal tolerance, markedly different from the immune privilege of intraocular structures. Remarkably, conjunctival tolerance is akin to the oral and respiratory tolerance mechanisms found in the gut and airways, respectively. And also similarly, this form of immunoregulation in the eye is affected by ageing just as it is in the digestive and respiratory tracts. With ageing comes an increased prevalence of immune-based ocular surface disorders, which could be related to an age-related impairment of conjunctival tolerance. The purpose of this review was to summarize the present knowledge of ocular mucosal tolerance and how it is affected by the ageing process in the light of the current literature on mucosal immunoregulation of the gut and airways.

High frequency of inactivating tetraspanin C D37 mutations in diffuse large B-cell lymphoma at immune-privileged sites.

Tetraspanin CD37 is predominantly expressed on the cell surface of mature B lymphocytes and is currently being studied as novel therapeutic target for B-cell lymphoma. Recently, we demonstrated that loss of CD37 induces spontaneous B-cell lymphoma in Cd37-knockout mice and correlates with inferior survival in patients with diffuse large B-cell lymphoma (DLBCL). Here, CD37 mutation analysis was performed in a cohort of 137 primary DLBCL samples, including 44 primary immune-privileged site-associated DLBCL (IP-DLBCL) samples originating in the testis or central nervous system. CD37 mutations were exclusively identified in IP-DLBCL cases (10/44, 23%) but absent in non-IP-DLBCL cases. The aberrations included 10 missense mutations, 1 deletion, and 3 splice-site CD37 mutations. Modeling and functional analysis of CD37 missense mutations revealed loss of function by impaired CD37 protein expression at the plasma membrane of human lymphoma B cells. This study provides novel insight into the molecular pathogenesis of IP-DLBCL and indicates that anti-CD37 therapies will be more beneficial for DLBCL patients without CD37 mutations.

Immune privilege of skin stem cells: What do we know and what can we learn?

The skin forms a barrier that prevents dehydration and keeps us safe from pathogens. To ensure proper function, the skin possesses a myriad of stem cell populations that are essential for maintenance and repair upon damage. In order to protect, the skin is also an active immunological site, with abundant resident immune cells and strong recruitment of even more immune cells during wounding or infection. Such active and strong immunity makes the skin susceptible to a diverse spectrum of autoimmune diseases, such as vitiligo and alopecia areata. Conversely, despite constant immune surveillance, the skin is also a tissue where frequent malignancies occur, which suggests that immune evasion must also take place. Skin stem cells play a crucial role during both regeneration and tumorigenesis. How immune cells, and in particular T cells, interact with skin stem cells and the implications this crosstalk has in skin disease (both autoimmunity and cancer) is not fully understood. Uncovering the mechanisms governing immune-stem cells interactions in the skin is critical for the development of new therapeutic strategies to safeguard susceptible cells during autoimmunity and, conversely, to improve cancer immunotherapy. Here, I will discuss how distinct skin stem cell populations are attacked by, or conversely, cloaked from immune cells, and the implications their differences have in autoimmunity and cancer.

When Clarity Is Crucial: Regulating Ocular Surface Immunity.

The ocular surface is a unique mucosal immune compartment in which anatomical, physiological, and immunological features act in concert to foster a particularly tolerant microenvironment. These mechanisms are vital to the functional competence of the eye, a fact underscored by the devastating toll of excessive inflammation at the cornea - blindness. Recent data have elucidated the contributions of specific anatomical components, immune cells, and soluble immunoregulatory factors in promoting homeostasis at the ocular surface. We highlight research trends at this distinctive mucosal barrier and identify crucial gaps in our current knowledge.

Hypoxia-induced increase in Sug1 leads to poor post-transplantation survival of allogeneic mesenchymal stem cells.

Allogeneic mesenchymal stem cells (MSCs) from young and healthy donors are immunoprivileged and have the potential to treat numerous degenerative diseases. However, recent reviews of clinical trials report poor long-term survival of transplanted cells in the recipient that turned down the enthusiasm regarding MSC therapies. Increasing evidence now confirm that though initially immunoprivileged, MSCs eventually become immunogenic after transplantation in the ischemic or hypoxic environment of diseased tissues and are rejected by the host immune system. We performed in vitro (in rat and human cells) and in vivo (in a rat model) investigations to understand the mechanisms of the immune switch in the phenotype of MSCs. The immunoprivilege of MSCs is preserved by the absence of cell surface immune antigen, major histocompatibility complex II (MHC-II) molecule. We found that the ATPase subunit of 19S proteasome "Sug1" regulates MHC-II biosynthesis in MSCs. Exposure to hypoxia upregulates Sug1 in MSCs and its binding to class II transactivator (CIITA), a coactivator of MHC-II transcription. Sug1 binding to CIITA in hypoxic MSCs promotes the acetylation and K63 ubiquitination of CIITA leading to its activation and translocation to the nucleus, and ultimately MHC-II upregulation. In both rat and human MSCs, knocking down Sug1 inactivated MHC-II and preserved immunoprivilege even following hypoxia. In a rat model of myocardial infarction, transplantation of Sug1-knockdown MSCs in ischemic heart preserved immunoprivilege and improved the survival of transplanted cells. Therefore, the current study provides novel mechanisms of post-transplantation loss of immunoprivilege of MSCs. This study may help in facilitating better planning for future clinical trials.

Hematological patterns and histopathological assessment of Miniature Pigs in the experiments on human mesenchymal stem cell transplantation.

Background: Multipotent and immune privileged properties of mesenchymal stem cells (MSCs) were investigated for the treatment of various clinical diseases. For the years, many researches into the animal studies evaluated human stem cell therapeutic capacity related to the regenerative medicine. However, there were limited reports on immune privileged properties of human MSCs in animal studies. The present study investigated hematological and biochemical parameter and lymphocyte subset in mini-pigs following human MSCs transplantation as a means of validation of reliability that influence the animal test results. Methods: The miniature pigs were transplanted with human MSCs seeded with scaffold. After transplantation, all animals were evaluated by CBC, biochemistry and lymphocyte subset test. After 9 weeks, all pigs were sacrificed and organs were histologically analyzed. Results: CBC test showed that levels of RBC were decreased and reticulocyte, WBC and neutrophil were increased in transient state initially after transplantation, but returned to normal value. The proportion of B lymphocyte and cytotoxic T cell were also initially enhanced within the normal range temporarily. The female and male miniature pigs showed normal ranges for blood chemistry assessments. During the 9 weeks post-operative period, the animals showed a continuous increase in body weight and length. Furthermore, no abnormal findings were observed from the histological analysis of sacrificed pigs. Conclusions: Overall, miniature pigs transplanted with human MSCs seeded with scaffold were found to have physiologically similar results to normal animals. This result might be a reliable indicator of the animal experiments using miniature pigs with human MSCs.

The Good, the Bad and the Ugly of Testicular Immune Regulation: A Delicate Balance Between Immune Function and Immune Privilege.

The testis is one of several immune privilege sites. These sites are necessary to decrease inflammation and immune responses that could be damaging to the host. For example, inflammation in the brain, eye or placenta could result in loss of cognitive function, vision or rejection of the semi-allogeneic fetus, respectively. In the testis, immune privilege is "good" as it is necessary for protection of the developing auto-immunogenic germ cells. However, there is also a downside or "bad" part of immune privilege, where pathogens and cancers can take advantage of this privilege and persist in the testis as a sanctuary site. Even worse, the "ugly" of privilege is how re-emerging viruses, such as Ebola and Zika viruses, can establish persistence in the testes and be sexually transmitted even months after they have been cleared from the bloodstream. In this review, we will discuss the delicate balance within the testis that provides immune privilege to protect the germ cells while still allowing for immune function to fight off pathogens and tumors.