Mice lacking the MHC class II transactivator (CIITA) show tissue-specific impairment of MHC class II expression

Quadruple adenine base-edited allogeneic CAR T cells outperform CRISPR/Cas9 nuclease-engineered T cells

Genome-editing technologies have enabled the clinical development of allogeneic cellular therapies, yet the optimal gene-editing modality for multiplex editing of therapeutic T cell product manufacturing remains elusive. In this study, we conducted a comprehensive comparison of CRISPR/Cas9 nuclease and adenine base editor (ABE) technologies in generating allogeneic chimeric antigen receptor (CAR) T cells, utilizing extensive in vitro and in vivo analyses. Both methods achieved high editing efficiencies across four target genes, critical for mitigating graft-versus-host disease and allograft rejection: TRAC or CD3E, B2M, CIITA, and PVR. Notably, ABE demonstrated higher manufacturing yields and distinct off-target profiles compared to Cas9, with translocations observed exclusively in Cas9-edited products. Functionally, ABE-edited CAR T cells exhibited superior in vitro effector functions under continuous antigen stimulation, including enhanced proliferative capacity and increased surface CAR expression. Transcriptomic analysis revealed that ABE editing resulted in reduced activation of p53 and DNA damage response pathways at baseline, along with sustained activation of metabolic pathways during antigen stress. Consistently, Assay for Transposase-Accessible Chromatin using sequencing data indicated that Cas9-edited, but not ABE-edited, CAR T cells showed enrichment of chromatin accessibility peaks associated with double-strand break repair and DNA damage response pathways. In a preclinical leukemia model, ABE-edited CAR T cells demonstrated improved tumor control and extended overall survival compared to their Cas9-edited counterparts. Collectively, these findings position ABE as superior to Cas9 nucleases for multiplex gene editing of therapeutic T cells.

MHC Class II-Expressing Mucosal Mast Cells Promote Intestinal Mast Cell Hyperplasia in a Mouse Model of Food Allergy

BACKGROUND

IgE-mediated food allergy is accompanied by mucosal mast cell (MMC) hyperplasia in the intestinal mucosa. Intestinal MMC numbers correlate with the severity of food allergy symptoms. However, the mechanisms by which MMCs proliferate excessively are poorly understood. Here, we clarify the role of newly identified MHC class II (MHCII)-expressing MMCs in the effector phase of IgE-mediated food allergy.

METHODS

Mice reconstituted with MHCII-deficient or wild-type MMCs were used to generate a mouse mode of IgE-mediated food allergy. We assessed the extent of intestinal MMC hyperplasia and the severity of hypothermia in these mice. In addition, we performed in vitro antigen presentation assay using induced MHCII-expressing MMCs generated from bone marrow cells to evaluate the effect of CD4+ T cell activation on MMC proliferation.

RESULTS

In food-allergic mice, we identified the appearance of MHCII-expressing MMCs in the intestinal mucosa and showed that MMC hyperplasia was suppressed in mice with MHCII-deficient MMCs compared to mice with wild-type MMCs. In vitro assays demonstrated that MHCII-expressing MMCs incorporate food antigens directly and through the high-affinity IgE receptor FcεRI-mediated endocytosis and activate antigen-specific CD4+ T cells from food-allergic mice by antigen presentation. Activated CD4+ T cells secrete IL-4 and large amounts of IL-5, which enhance production of the mast cell growth factor IL-9 by IL-33-activated MMCs. Excess IL-9 causes excessive MMC proliferation, leading to the development of MMC hyperplasia.

CONCLUSION

Antigen presentation to CD4+ T cells by MHCII-expressing MMCs triggers intestinal MMC hyperplasia and exacerbates IgE-mediated food allergy.

New insights into the structure domain and function of NLR family CARD domain containing 5

NOD-like receptor family CARD domain-containing 5 (NLRC5) is a major transcriptional coactivator of MHC class I genes. NLRC5 is the largest member of the NLR family and contains three domains: an untypical caspase recruitment domain (uCARD), a central nucleotide-binding and oligomerization domain (NOD or NACHT), and a leucine-rich repeat (LRR) domain. The functional variability of NLRC5 has been attributed to its different domain interactions with specific ligands in different cell types. In this review, we address the molecular mechanisms and their implications in multiple microenvironments based on the different functional domains of NLRC5.

ZBTB48 is a priming factor regulating B-cell-specific CIITA expression

The class-II transactivator (CIITA) is the master regulator of MHC class-II gene expression and hence the adaptive immune response. Three cell type-specific promoters (pI, pIII, and pIV) are involved in the regulation of CIITA expression, which can be induced by IFN-γ in non-immune cells. While key regulatory elements have been identified within these promoters, our understanding of the transcription factors regulating CIITA expression is incomplete. Here, we demonstrate that the telomere-binding protein and transcriptional activator ZBTB48 directly binds to both critical activating elements within the B-cell-specific promoter CIITA pIII. ZBTB48 knockout impedes the CIITA/MHC-II expression program induced in non-APC cells by IFN-γ, and loss of ZBTB48 in mice silences MHC-II expression in pro-B and immature B cells. Transcriptional regulation of CIITA by ZBTB48 is enabled by ZBTB48-dependent chromatin opening at CIITA pIII upstream of activating H3K4me3 marks. We conclude that ZBTB48 primes CIITA pIII by acting as a molecular on-off-switch for B-cell-specific CIITA expression.

Effect of Moniezia Benedeni infection on ileal transcriptome profile characteristics of sheep

BACKGROUND

The intestinal mucosal immune system, renowned for its precise and sensitive regulation, can provide comprehensive and effective protection for the body, among which the ileum is a critical induction site for regulating mucosal immune homeostasis. Moniezia benedeni parasitizes the small intestine of sheep and can cause serious pathological damage or even death to the host when the infection is severe. In this study, 5 sheep infected with Moniezia benedeni were selected as the infected group, and 5 uninfected sheep were selected as the control group. The ileal transcriptome profile characteristics of Moniezia benedeni infection were analyzed based on RNA-seq sequencing technology, aiming to lay a foundation for further exploring the perception mechanism of sheep intestines to Moniezia benedeni infection and formulating effective prevention and control strategies.

RESULTS

The results showed that a total of 3,891 differentially expressed genes (DEGs) were detected in the ileum tissues of sheep between the infected and control groups with 2,429 up-regulated genes and 1,462 down-regulated genes. GO and KEGG pathway enrichment analysis of differential genes, as well as Clue GO analysis showed that differential genes were significantly enriched in immune and metabolic-related biological processes and signaling pathways. Particularly, in immune-related signaling pathways, the B cell receptor signaling pathway was significantly down-regulated, while in metabolic regulation related signaling pathways, Bile secretion, Fat digestion and absorption and Vitamin digestion and absorption were notably up-regulated. On this basis, the differential core genes related to immune metabolism were verified by qRT-PCR method. The results showed that OVAR, CD3E, CD8A, CD4 and CD28 were significantly up-regulated (P < 0.05), while CIITA, BLNK, BCL6 and CD79A were significantly down-regulated (P < 0.05), which were consistent with transcriptome sequencing data.

CONCLUSIONS

The results demonstrated that Moniezia benedeni infection significantly affected the immune and metabolic processes in sheep ileum, particularly, it significantly inhibited the activation process of host B cells, and also led to an overactive function of bile acid metabolism. This finding provides a solid foundation for further elucidating the response mechanism of Peyer's patches in sheep ileum to Moniezia tapeworm infection.

Internal regulation between constitutively expressed T cell co-inhibitory receptors BTLA and CD5 and tolerance in recent thymic emigrants

Immunologic self-tolerance involves signals from co-inhibitory receptors. Several T cell co-inhibitors, including PD-1, are expressed upon activation, whereas CD5 and BTLA are expressed constitutively. The relationship between constitutively expressed co-inhibitors and when they are needed is unknown. Deletion of Btla demonstrated BTLA regulates CD5 expression. Loss of BTLA signals, but not signalling by its ligand, HVEM, leads to increased CD5 expression. Higher CD5 expression set during thymic selection is associated with increased self-recognition, suggesting that BTLA might be needed early to establish self-tolerance. We found that BTLA and PD-1 were needed post-thymic selection in recent thymic emigrants (RTE). RTE lacking BTLA caused a CD4 T cell and MHC class II dependent multi-organ autoimmune disease. Together, our findings identify a negative regulatory pathway between two constitutively expressed co-inhibitors, calibrating their expression. Expression of constitutive and induced co-inhibitory receptors is needed early to establish tolerance in the periphery for RTE.

Elimination of GGTA1, CMAH, β4GalNT2 and CIITA genes in pigs compromises human versus pig xenogeneic immune reactions

BACKGROUND

Pig organ xenotransplantation is a potential solution for the severe organ shortage in clinic, while immunogenic genes need to be eliminated to improve the immune compatibility between humans and pigs. Current knockout strategies are mainly aimed at the genes causing hyperacute immune rejection (HAR) that occurs in the first few hours while adaptive immune reactions orchestrated by CD4 T cell thereafter also cause graft failure, in which process the MHC II molecule plays critical roles.

METHODS

Thus, we generate a 4-gene (GGTA1, CMAH, β4GalNT2, and CIITA) knockout pig by CRISPR/Cas9 and somatic cell nuclear transfer to compromise HAR and CD4 T cell reactions simultaneously.

RESULTS

We successfully obtained 4KO piglets with deficiency in all alleles of genes, and at cellular and tissue levels. Additionally, the safety of our animals after gene editing was verified by using whole-genome sequencing and karyotyping. Piglets have survived for more than one year in the barrier, and also survived for more than 3 months in the conventional environment, suggesting that the piglets without MHC II can be raised in the barrier and then gradually mated in the conventional environment.

CONCLUSIONS

4KO piglets have lower immunogenicity, are safe in genomic level, and are easier to breed than the model with both MHC I and II deletion.

A Ménage à trois: NLRC5, immunity, and metabolism

The nucleotide-binding and oligomerization domain-like receptors (NLRs) NLR family CARD domain-containing protein 5 (NLRC5) and Class II Major Histocompatibility Complex Transactivator (CIITA) are transcriptional regulators of major histocompatibility complex (MHC) class I and class II genes, respectively. MHC molecules are central players in our immune system, allowing the detection of hazardous 'non-self' antigens and, thus, the recognition and elimination of infected or transformed cells from the organism. Recently, CIITA and NLRC5 have emerged as regulators of selected genes of the butyrophilin (BTN) family that interestingly are located in the extended MHC locus. BTNs are transmembrane proteins exhibiting structural similarities to B7 family co-modulatory molecules. The family member BTN2A2, which indeed contributes to the control of T cell activation, was found to be transcriptionally regulated by CIITA. NLRC5 emerged instead as an important regulator of the BTN3A1, BTN3A2, and BTN3A3 genes. Together with BTN2A1, BTN3As regulate non-conventional Vγ9Vδ2 T cell responses triggered by selected metabolites of microbial origin or accumulating in hematologic cancer cells. Even if endogenous metabolites conform to the canonical definition of 'self', metabolically abnormal cells can represent a danger for the organism and should be recognized and controlled by immune system cells. Collectively, new data on the role of NLRC5 in the expression of BTN3As link the mechanisms regulating canonical 'non-self' presentation and those marking cells with abnormal metabolic configurations for immune recognition, an evolutionary parallel that we discuss in this perspective review.

Assessment of cancer cell-expressed HLA class I molecules and their immunopathological implications

Immunotherapy using immune checkpoint inhibitors (ICIs) has shown superior efficacy compared with conventional chemotherapy in certain cancer types, establishing immunotherapy as the fourth standard treatment alongside surgical intervention, chemotherapy, and radiotherapy. In cancer immunotherapy employing ICIs, CD8-positive cytotoxic T lymphocytes are recognized as the primary effector cells. For effective clinical outcomes, it is essential that the targeted cancer cells express HLA class I molecules to present antigenic peptides derived from the tumor. However, cancer cells utilize various mechanisms to downregulate or lose HLA class I molecules from their surface, resulting in evasion from immune surveillance. Correlations between prognosis and the integrity of HLA class I molecules expressed by cancer cells have been consistently found across different types of cancer. This paper provides an overview of the regulatory mechanisms of HLA class I molecules and their role in cancer immunotherapy, with a particular emphasis on the significance of utilizing pathological tissues to evaluate HLA class I molecules expressed in cancer cells.

Peroxisome deficiency underlies failures in hepatic immune cell development and antigen presentation in a severe Zellweger disease model

Peroxisome biogenesis disorders (PBDs) represent a group of metabolic conditions that cause severe developmental defects. Peroxisomes are essential metabolic organelles, present in virtually every eukaryotic cell and mediating key processes in immunometabolism. To date, the full spectrum of PBDs remains to be identified, and the impact PBDs have on immune function is unexplored. This study presents a characterization of the hepatic immune compartment of a neonatal PBD mouse model at single-cell resolution to establish the importance and function of peroxisomes in developmental hematopoiesis. We report that hematopoietic defects are a feature in a severe PBD murine model. Finally, we identify a role for peroxisomes in the regulation of the major histocompatibility class II expression and antigen presentation to CD4+ T cells in dendritic cells. This study adds to our understanding of the mechanisms of PBDs and expands our knowledge of the role of peroxisomes in immunometabolism.

Engineering human pluripotent stem cell lines to evade xenogeneic transplantation barriers

Successful allogeneic human pluripotent stem cell (hPSC)-derived therapies must overcome immunological rejection by the recipient. To build reagents to define these barriers, we genetically ablated β2M, TAP1, CIITA, CD74, MICA, and MICB to limit expression of HLA-I, HLA-II, and natural killer (NK) cell activating ligands in hPSCs. Transplantation of these cells that also expressed covalent single chain trimers of Qa1 and H2-Kb to inhibit NK cells and CD55, Crry, and CD59 to inhibit complement deposition led to persistent teratomas in wild-type mice. Transplantation of HLA-deficient hPSCs into mice genetically deficient in complement and depleted of NK cells also led to persistent teratomas. Thus, T cell, NK cell, and complement evasion are necessary to prevent immunological rejection of hPSCs and their progeny. These cells and versions expressing human orthologs of immune evasion factors can be used to define cell type-specific immune barriers and conduct preclinical testing in immunocompetent mouse models.

The effects of NOD-like receptors on adaptive immune responses

It has long been appreciated that cues from the innate immune system orchestrate downstream adaptive immune responses. Although previous work has focused on the roles of Toll-like receptors in this regard, relatively little is known about how Nod-like receptors instruct adaptive immunity. Here we review the functions of different members of the Nod-like receptor family in orchestrating effector and anamnestic adaptive immune responses. In particular, we address the ways in which inflammasome and non-inflammasome members of this family affect adaptive immunity under various infectious and environmental contexts. Furthermore, we identify several key mechanistic questions that studies in this field have left unaddressed. Our aim is to provide a framework through which immunologists in the adaptive immune field may view their questions through an innate-immune lens and vice-versa.

Universal cell donor lines: A review of the current research

Human embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) hold promise for transplantation medicine. Diverse human leukocyte antigen (HLA) profiles necessitate autologous cells or multiple cell lines for therapeutics, incurring time and cost. Advancements in CRISPR-Cas9 and cellular therapies have led to the conceptualization of "off-the-shelf" universal cell donor lines, free of immune rejection. Overcoming immune rejection is a challenge. This review outlines strategies to modulate the major histocompatibility complex (MHC) to generate a universal cell donor line. Upon bypassing MHC mismatch, multifaceted approaches are required to generate foreign host-tolerated cells. Universal cells harbor risks, namely immune escape and tumor formation. To mitigate, we review safety mechanisms enabling donor cell inactivation or removal. Achieving a universal cell line would reduce treatment wait time, eliminate donor search, and reduce graft-versus-host disease risk without immunosuppression. The pursuit of universally tolerated cells is under way, ready to transform transplantation and regenerative medicine.

Engineering Human Pluripotent Stem Cell Lines to Evade Xenogeneic Transplantation Barriers

Allogeneic human pluripotent stem cell (hPSC)-derived cells and tissues for therapeutic transplantation must necessarily overcome immunological rejection by the recipient. To define these barriers and to create cells capable of evading rejection for preclinical testing in immunocompetent mouse models, we genetically ablated β2m, Tap1, Ciita, Cd74, Mica, and Micb to limit expression of HLA-I, HLA-II, and natural killer cell activating ligands in hPSCs. Though these and even unedited hPSCs readily formed teratomas in cord blood-humanized immunodeficient mice, grafts were rapidly rejected by immunocompetent wild-type mice. Transplantation of these cells that also expressed covalent single chain trimers of Qa1 and H2-Kb to inhibit natural killer cells and CD55, Crry, and CD59 to inhibit complement deposition led to persistent teratomas in wild-type mice. Expression of additional inhibitory factors such as CD24, CD47, and/or PD-L1 had no discernible impact on teratoma growth or persistence. Transplantation of HLA-deficient hPSCs into mice genetically deficient in complement and depleted of natural killer cells also led to persistent teratomas. Thus, T cell, NK cell, and complement evasion are necessary to prevent immunological rejection of hPSCs and their progeny. These cells and versions expressing human orthologs of immune evasion factors can be used to refine tissue- and cell type-specific immune barriers, and to conduct preclinical testing in immunocompetent mouse models.

The role of NOD-like receptors in innate immunity

The innate immune system in vertebrates and invertebrates relies on conserved receptors and ligands, and pathways that can rapidly initiate the host response against microbial infection and other sources of stress and danger. Research into the family of NOD-like receptors (NLRs) has blossomed over the past two decades, with much being learned about the ligands and conditions that stimulate the NLRs and the outcomes of NLR activation in cells and animals. The NLRs play key roles in diverse functions, ranging from transcription of MHC molecules to initiation of inflammation. Some NLRs are activated directly by their ligands, while other ligands may have indirect effects on the NLRs. New findings in coming years will undoubtedly shed more light on molecular details involved in NLR activation, as well as the physiological and immunological outcomes of NLR ligation.

NOD-like receptors in asthma

Asthma is an extremely prevalent chronic inflammatory disease of the airway where innate and adaptive immune systems participate collectively with epithelial and other structural cells to cause airway hyperresponsiveness, mucus overproduction, airway narrowing, and remodeling. The nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) are a family of intracellular innate immune sensors that detect microbe-associated molecular patterns and damage-associated molecular patterns, well-recognized for their central roles in the maintenance of tissue homeostasis and host defense against bacteria, viruses and fungi. In recent times, NLRs have been increasingly acknowledged as much more than innate sensors and have emerged also as relevant players in diseases classically defined by their adaptive immune responses such as asthma. In this review article, we discuss the current knowledge and recent developments about NLR expression, activation and function in relation to asthma and examine the potential interventions in NLR signaling as asthma immunomodulatory therapies.

CIITA expression is regulated by histone deacetylase enzymes and has a role in α-synuclein pre-formed fibril-induced antigen presentation in murine microglial cell line

AIM

Parkinson's disease(PD) is a chronic neurodegenerative disorder related with several genetic and epigenetic factors. In the context of epigenetic factors, histone acetylation is one of the most associated mechanisms with Parkinson's disease progression. This study investigates the effects of the increased histone acetylation on antigen presentation in microglial cells which were induced by pre-formed fibrils of α-synuclein(pFF α-synuclein).

METHODS

Parkinson's disease model was created with pFF α-synuclein administration to the BV-2 microglial cells. BV-2 cells were co-treated with CUDC-907 and TMP-195 to increase histone acetylation in the presence of α-synuclein. Antigen representation was evaluated by determining expression levels of major histocompatibility complex-II(MHC-II) and class-II major histocompatibility complex(CIITA).

RESULTS

Our results showed that pFF α-synuclein significantly increased MHC-II expression, and that effect was most severe at 6 hours of administration of α-synuclein. Increasing histone acetylation via CUDC-907 and TMP-195 enhanced MHC-II levels expression, which was more severe in CUDC-907. Additionally, CIITA expression levels were significantly increased with pFF α-synuclein administration and intensified with the co-treatment of CUDC-907 and TMP-195. Furthermore, pFF α-synuclein caused a time-dependent increase in the IFN-gamma(IFN-ɣ) and interleukin-16(IL-16) levels, and that increase was potentiated with CUDC-907 and TMP-195.

CONCLUSION

Changes in MHC-II and CIITA expression indicate that histone acetylation increases the antigen presentation properties of microglial cells after pFF α-synuclein or histone deacetylase inhibitor(HDACi) administration. Our results show that microglial antigen presentation might have an essential role in the pathology of Parkinson's disease, and α-synuclein likely to play a primary role in this mechanism.

Mesenchymal stromal cells equipped by IFNα empower T cells with potent anti-tumor immunity

Cancer treatments have been revolutionized by the emergence of immune checkpoint blockade therapies. However, only a minority of patients with various tumor types have benefited from such treatments. New strategies focusing on the immune contexture of the tumor tissue microenvironment hold great promises. Here, we created IFNα-overexpressing mesenchymal stromal cells (IFNα-MSCs). Upon direct injection into tumors, we found that these cells are powerful in eliminating several types of tumors. Interestingly, the intra-tumoral injection of IFNα-MSCs could also induce specific anti-tumor effects on distant tumors. These IFNα-MSCs promoted tumor cells to produce CXCL10, which in turn potentiates the infiltration of CD8⁺ T cells in the tumor site. Furthermore, IFNα-MSCs enhanced the expression of granzyme B (GZMB) in CD8⁺ T cells and invigorated their cytotoxicity in a Stat3-dependent manner. Genetic ablation of Stat3 in CD8⁺ T cells impaired the effect of IFNα-MSCs on GZMB expression. Importantly, the combination of IFNα-MSCs and PD-L1 blockade induced an even stronger anti-tumor immunity. Therefore, IFNα-MSCs represent a novel tumor immunotherapy strategy, especially when combined with PD-L1 blockade.

High-affinity, neutralizing antibodies to SARS-CoV-2 can be made without T follicular helper cells

T follicular helper (TFH) cells are the conventional drivers of protective, germinal center (GC)–based antiviral antibody responses. However, loss of TFH cells and GCs has been observed in patients with severe COVID-19. As T cell–B cell interactions and immunoglobulin class switching still occur in these patients, noncanonical pathways of antibody production may be operative during SARS-CoV-2 infection. We found that both TFH-dependent and -independent antibodies were induced against SARS-CoV-2 infection, SARS-CoV-2 vaccination, and influenza A virus infection. Although TFH-independent antibodies to SARS-CoV-2 had evidence of reduced somatic hypermutation, they were still high affinity, durable, and reactive against diverse spike-derived epitopes and were capable of neutralizing both homologous SARS-CoV-2 and the B.1.351 (beta) variant of concern. We found by epitope mapping and B cell receptor sequencing that TFH cells focused the B cell response, and therefore, in the absence of TFH cells, a more diverse clonal repertoire was maintained. These data support an alternative pathway for the induction of B cell responses during viral infection that enables effective, neutralizing antibody production to complement traditional GC-derived antibodies that might compensate for GCs damaged by viral inflammation.

Decoding the role of macrophages in periodontitis and type 2 diabetes using single-cell RNA-sequencing

Macrophages are resident myeloid cells in the gingival tissue which control homeostasis and play a pivotal role in orchestrating the immune response in periodontitis. Cell heterogeneity and functional phenotypes of macrophage subpopulations in periodontitis remain elusive. Here, we isolated gingival tissue from periodontitis-affected and healthy sites of patients with and without type 2 diabetes mellitus (T2DM). We then used single-cell RNA-sequencing (scRNA-seq) to define the heterogeneity of tissue-resident macrophages in gingival tissue in health vs. periodontitis. scRNA-seq demonstrated an unforeseen gene expression heterogeneity among macrophages in periodontitis and showed transcriptional and signaling heterogeneity of identified subsets in an independent cohort of patients with periodontitis and T2DM. Our bioinformatic inferences indicated divergent expression profiles in macrophages driven by transcriptional regulators CIITA, RELA, RFX5, and RUNX2. Macrophages in periodontitis expressed both pro-inflammatory and anti-inflammatory markers and their polarization was not mutually exclusive. The majority of macrophages in periodontitis expressed the monocyte lineage marker CD14, indicating their bone marrow lineage. We also found high expression and activation of RELA, a subunit of the NF-κB transcription factor complex, in gingival macrophages of periodontitis patients with T2DM. Our data suggested that heterogeneity and hyperinflammatory activation of macrophages may be relevant to the pathogenesis and outcomes of periodontitis, and may be further augmented in patients with T2DM.

Selective deletion of human leukocyte antigens protects stem cell-derived islets from immune rejection

Stem cell-based replacement therapies hold the promise to restore function of damaged or degenerated tissue such as the pancreatic islets in people with type 1 diabetes. Wide application of these therapies requires overcoming the fundamental roadblock of immune rejection. To address this issue, we use genetic engineering to create human pluripotent stem cells (hPSCs) in which the majority of the polymorphic human leukocyte antigens (HLAs), the main drivers of allogeneic rejection, are deleted. We retain the common HLA class I allele HLA-A2 and less polymorphic HLA-E/F/G to allow immune surveillance and inhibition of natural killer (NK) cells. We employ a combination of in vitro assays and humanized mouse models to demonstrate that these gene manipulations significantly reduce NK cell activity and T-cell-mediated alloimmune response against hPSC-derived islet cells. In summary, our approach produces hypoimmunogenic hPSCs that can be readily matched with recipients to avoid alloimmune rejection.

Type II alveolar cell MHCII improves respiratory viral disease outcomes while exhibiting limited antigen presentation

Type II alveolar cells (AT2s) are critical for basic respiratory homeostasis and tissue repair after lung injury. Prior studies indicate that AT2s also express major histocompatibility complex class II (MHCII) molecules, but how MHCII expression by AT2s is regulated and how it contributes to host defense remain unclear. Here we show that AT2s express high levels of MHCII independent of conventional inflammatory stimuli, and that selective loss of MHCII from AT2s in mice results in modest worsening of respiratory virus disease following influenza and Sendai virus infections. We also find that AT2s exhibit MHCII presentation capacity that is substantially limited compared to professional antigen presenting cells. The combination of constitutive MHCII expression and restrained antigen presentation may position AT2s to contribute to lung adaptive immune responses in a measured fashion, without over-amplifying damaging inflammation.

Identification of survival-related genes and a novel gene-based prognostic signature involving the tumor microenvironment of uveal melanoma

Uveal melanoma (UM) is the most common primary intraocular malignant tumor in adults and almost fifty percent of patients subsequently develop systemic metastases usually involving the liver. The tumor microenvironment (TME) is crucial to the initiation and progression of tumors. In the present study, we comprehensively evaluated the TME of primary UM samples from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) database by using several bioinformatic algorithms. The prognostic value of immune score and infiltrating immune cells in the TME were evaluated. Differentially expressed genes between the low- and high-immune score groups were also identified. The majority of tumor-infiltrating lymphocytes in UM have been determined to be activated CD8 + T cells. Therefore, weighted gene co-expression network analysis (WGCNA) was performed to identify the co-expression modules and genes significantly associated with the level of infiltrating CD8 + T cells in UM. Survival-related genes involved in the TME were identified by univariate Cox regression analysis. Furthermore, an eight-gene-based prognostic signature was established in the training dataset TCGA-UM via Lasso-penalized and multivariate Cox regression analyses. The predictive value of this signature was validated in two testing datasets. Besides, a nomogram was established to serve clinical practice. Moreover, hub genes involved in the infiltrating CD8 + T cells were identified and a potential targeted therapy for preventing metastasis of UM was proposed based on the results. In summary, our results provided a robust gene-based prognostic signature for predicting prognosis of UM patients and proposed a potential targeted therapy for preventing UM metastasis.

Nod-Like Receptors in Host Defence and Disease at the Epidermal Barrier

The nucleotide-binding domain and leucine-rich-repeat-containing family (NLRs) (sometimes called the NOD-like receptors, though the family contains few bona fide receptors) are a superfamily of multidomain-containing proteins that detect cellular stress and microbial infection. They constitute a critical arm of the innate immune response, though their functions are not restricted to pathogen recognition and members engage in controlling inflammasome activation, antigen-presentation, transcriptional regulation, cell death and also embryogenesis. NLRs are found from basal metazoans to plants, to zebrafish, mice and humans though functions of individual members can vary from species to species. NLRs also display highly wide-ranging tissue expression. Here, we discuss the importance of NLRs to the immune response at the epidermal barrier and summarise the known role of individual family members in the pathogenesis of skin disease.

The MHC Class-I Transactivator NLRC5: Implications to Cancer Immunology and Potential Applications to Cancer Immunotherapy

The immune system constantly monitors the emergence of cancerous cells and eliminates them. CD8⁺ cytotoxic T lymphocytes (CTLs), which kill tumor cells and provide antitumor immunity, select their targets by recognizing tumor antigenic peptides presented by MHC class-I (MHC-I) molecules. Cancer cells circumvent immune surveillance using diverse strategies. A key mechanism of cancer immune evasion is downregulation of MHC-I and key proteins of the antigen processing and presentation machinery (APM). Even though impaired MHC-I expression in cancers is well-known, reversing the MHC-I defects remains the least advanced area of tumor immunology. The discoveries that NLRC5 is the key transcriptional activator of MHC-I and APM genes, and genetic lesions and epigenetic modifications of NLRC5 are the most common cause of MHC-I defects in cancers, have raised the hopes for restoring MHC-I expression. Here, we provide an overview of cancer immunity mediated by CD8⁺ T cells and the functions of NLRC5 in MHC-I antigen presentation pathways. We describe the impressive advances made in understanding the regulation of NLRC5 expression, the data supporting the antitumor functions of NLRC5 and a few reports that argue for a pro-tumorigenic role. Finally, we explore the possible avenues of exploiting NLRC5 for cancer immunotherapy.

The MHC class II transactivator modulates seeded alpha-synuclein pathology and dopaminergic neurodegeneration in an in vivo rat model of Parkinson's disease

BACKGROUND

Abnormal folding, aggregation and spreading of alpha-synuclein (αsyn) is a mechanistic hypothesis for the progressive neuropathology in Parkinson's disease (PD). Spread of αsyn between cells is supported by clinical, neuropathological and experimental evidence. It has been proposed that a pro-inflammatory micro-environment in response to αsyn can promote its aggregation. We have previously shown that allelic differences in the major histocompatibility complex class two transactivator (Mhc2ta) gene, located in the VRA4 locus, alter MHCII expression levels, microglial activation and antigen presentation capacity in rats upon human αsyn over-expression. In addition, Mhc2ta regulated dopaminergic neurodegeneration and the extent of motor impairment. The purpose of this study was to determine whether Mhc2ta regulates αsyn aggregation, propagation and dopaminergic pathology in an αsyn pre-formed fibril (PFF)-seeded in vivo model of PD.

METHODS

The DA and DA.VRA4 congenic rat strains share background genome but display differential microglial antigen presenting capacity due to different Mhc2ta alleles in the VRA4 locus. PFFs of human αsyn or BSA solution were injected unilaterally to the striatum of DA and DA.VRA4 rats two weeks after ipsilateral administration of recombinant adeno-associated virus (rAAV) vectors carrying human αsyn or GFP to the substantia nigra pars compacta. Behavioural assessment was performed at 2, 5 and 8 weeks while histological evaluation of αsyn pathology, inflammation and neurodegeneration as well as determination of serum cytokine profiles were performed at 8 weeks.

RESULTS

rAAV-mediated expression of human αsyn in nigral dopaminergic neurons combined with striatal PFF administration induced enhanced αsyn pathology in DA.VRA4 compared to DA rats. Mhc2ta thus significantly regulated the seeding, propagation and toxicity of αsyn in vivo. This was reflected in terms of wider extent and anatomical distribution of αsyn inclusions, ranging from striatum to the forebrain, midbrain, hindbrain and cerebellum in DA.VRA4. Compared to DA rats, DA.VRA4 also displayed enhanced motor impairment and dopaminergic neurodegeneration as well as higher levels of the proinflammatory cytokines IL-2 and TNFα in serum.

CONCLUSIONS

We conclude that the key regulator of MHCII expression, Mhc2ta, modulates neuroinflammation, αsyn-seeded Lewy-like pathology, dopaminergic neurodegeneration and motor impairment. This makes Mhc2ta and microglial antigen presentation promising therapeutic targets for reducing the progressive neuropathology and clinical manifestations in PD.

Divergent T follicular helper cell requirement for IgA and IgE production to peanut during allergic sensitization

Immunoglobulin A (IgA) is the dominant antibody isotype in the gut and has been shown to regulate microbiota. Mucosal IgA is also widely believed to prevent food allergens from penetrating the gut lining. Even though recent work has elucidated how bacteria-reactive IgA is induced, little is known about how IgA to food antigens is regulated. Although IgA is presumed to be induced in a healthy gut at steady state via dietary exposure, our data do not support this premise. We found that daily food exposure only induced low-level, cross-reactive IgA in a minority of mice. In contrast, induction of significant levels of peanut-specific IgA strictly required a mucosal adjuvant. Although induction of peanut-specific IgA required T cells and CD40L, it was T follicular helper (T_FH) cell, germinal center, and T follicular regulatory (T_FR) cell-independent. In contrast, IgG1 and IgE production to peanut required T_FH cells. These data suggest an alternative paradigm in which the cellular mechanism of IgA production to food antigens is distinct from IgE and IgG1. We developed an equivalent assay to study this process in stool samples from healthy, nonallergic humans, which revealed substantial levels of peanut-specific IgA that were stable over time. Similar to mice, patients with loss of CD40L function had impaired titers of gut peanut-specific IgA. This work challenges two widely believed but untested paradigms about antibody production to dietary antigens: (i) the steady state/tolerogenic response to food antigens includes IgA production and (ii) T_FH cells drive food-specific gut IgA.

NLRC5 promotes transcription of BTN3A1-3 genes and Vγ9Vδ2 T cell-mediated killing

BTN3A molecules—BTN3A1 in particular—emerged as important mediators of Vγ9Vδ2 T cell activation by phosphoantigens. These metabolites can originate from infections, e.g. with Mycobacterium tuberculosis, or by alterations in cellular metabolism. Despite the growing interest in the BTN3A genes and their high expression in immune cells and various cancers, little is known about their transcriptional regulation. Here we show that these genes are induced by NLRC5, a regulator of MHC class I gene transcription, through an atypical regulatory motif found in their promoters. Accordingly, a robust correlation between NLRC5 and BTN3A gene expression was found in healthy, in M. tuberculosis-infected donors' blood cells, and in primary tumors. Moreover, forcing NLRC5 expression promoted Vγ9Vδ2 T-cell-mediated killing of tumor cells in a BTN3A-dependent manner. Altogether, these findings indicate that NLRC5 regulates the expression of BTN3A genes and hence open opportunities to modulate antimicrobial and anticancer immunity.

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BTN3A promoters contain a unique regulatory motif occupied by overexpressed NLRC5

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NLRC5 and BTN3A mRNA levels correlate in healthy and diseased cells

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NLRC5 overexpression increases susceptibility to Vγ9Vδ2 T-cell-mediated elimination

Major histocompatibility complexes are up-regulated in glomerular endothelial cells via activation of c-Jun N-terminal kinase in 5/6 nephrectomy mice

BACKGROUND AND PURPOSE

This study aims to explore the mechanism underlying the up-regulation of major histocompatibility complex (MHC) proteins in glomerular endothelial cells in 5/6 nephrectomy mice.

EXPERIMENTAL APPROACH

C57/BL6 mice were randomly allocated to sham-operated (2K) and 5/6 nephrectomy (5/6Nx) groups. Mouse splenic lymphocytes, from either syngeneic or allogeneic background, were injected into 5/6Nx mice after total body irradiation. Human glomerular endothelial cells (HGECs) were cultured for experiments in vitro. Western blots, PCR, immunohistochemical and fluorescent staining were used, along with assays of tissue cytokines, lymphocyte migration and renal function.

KEY RESULTS

Four weeks after nephrectomy, expression of both mRNA and protein of MHC II, CD80, and CD86 were increased in 5/6Nx glomerular endothelial cells. After total body irradiation, 5/6Nx mice injected with lymphocytes from Balb/c mice, but not those from C57/BL6 mice, exhibited increased creatinine levels, indicating that allograft lymphocyte transfer impaired renal function. In HGECs, the protein levels of MHC and MHC Class II transactivator (CIITA) were increased by stimulation with TNF-α or IFN-γ, which promoted human lymphocytes movement. These increases were reduced by JNK inhibitors. In the 5/6Nx mice, JNK inhibition down-regulated MHC II protein in glomerular endothelial cells, suggesting that JNK signalling participates in the regulation of MHC II protein.

CONCLUSION AND IMPLICATIONS

Chronic inflammation in mice subjected to nephrectomy induces the up-regulation of MHC molecules in glomerular endothelial cells. This up-regulation is reduced by inhibition of JNK signalling.

Generation of GGTA1-/-β2M-/-CIITA-/- Pigs Using CRISPR/Cas9 Technology to Alleviate Xenogeneic Immune Reactions

BACKGROUND

Xenogeneic organ transplantation has been proposed as a potential approach to fundamentally solve organ shortage problem. Xenogeneic immune responses across species is one of the major obstacles for clinic application of xeno-organ transplantation. The generation of glycoprotein galactosyltransferase α 1, 3 (GGTA1) knockout pigs has greatly contributed to the reduction of hyperacute xenograft rejection. However, severe xenograft rejection can still be induced by xenoimmune responses to the porcine major histocompatibility complex antigens swine leukocyte antigen class I and class II.

METHODS

We simultaneously depleted GGTA1, β2-microglobulin (β2M), and major histocompatibility complex class II transactivator (CIITA) genes using clustered regularly interspaced short palindromic repeats and CRISPR-associated proteins technology in Bamma pig fibroblast cells, which were further used to generate GGTA1β2MCIITA triple knockout (GBC-3KO) pigs by nuclear transfer.

RESULTS

The genotype of GBC-3KO pigs was confirmed by polymerase chain reaction and Sanger sequencing, and the loss of expression of α-1,3-galactose, SLA-I, and SLA-II was demonstrated by flow cytometric analysis using fluorescent-conjugated lectin from bandeiraea simplicifolia, anti-β2-microglobulin, and swine leukocyte antigen class II DR antibodies. Furthermore, mixed lymphocyte reaction assay revealed that peripheral blood mononuclear cells from GBC-3KO pigs were significantly less effective than (WT) pig peripheral blood mononuclear cells in inducing human CD3CD4 and CD3CD8 T-cell activation and proliferation. In addition, GBC-3KO pig skin grafts showed a significantly prolonged survival in immunocompetent C57BL/6 mice, when compared with wild-type pig skin grafts.

CONCLUSIONS

Taken together, these results demonstrate that elimination of GGTA1, β2M, and CIITA genes in pigs can effectively alleviate xenogeneic immune responses and prolong pig organ survival in xenogenesis. We believe that this work will facilitate future research in xenotransplantation.

MHC Class I Regulation: The Origin Perspective

Viral-derived elements and non-coding RNAs that build up “junk DNA” allow for flexible and context-dependent gene expression. They are extremely dense in the MHC region, accounting for flexible expression of the MHC I, II, and III genes and adjusting the level of immune response to the environmental stimuli. This review brings forward the viral-mediated aspects of the origin and evolution of adaptive immunity and aims to link this perspective with the MHC class I regulation. The complex regulatory network behind MHC expression is largely controlled by virus-derived elements, both as binding sites for immune transcription factors and as sources of regulatory non-coding RNAs. These regulatory RNAs are imbalanced in cancer and associate with different tumor types, making them promising targets for diagnostic and therapeutic interventions.

NOD-like Receptors in the Eye: Uncovering Its Role in Diabetic Retinopathy

Diabetic retinopathy (DR) is an ocular complication of diabetes mellitus (DM). International Diabetic Federations (IDF) estimates up to 629 million people with DM by the year 2045 worldwide. Nearly 50% of DM patients will show evidence of diabetic-related eye problems. Therapeutic interventions for DR are limited and mostly involve surgical intervention at the late-stages of the disease. The lack of early-stage diagnostic tools and therapies, especially in DR, demands a better understanding of the biological processes involved in the etiology of disease progression. The recent surge in literature associated with NOD-like receptors (NLRs) has gained massive attraction due to their involvement in mediating the innate immune response and perpetuating inflammatory pathways, a central phenomenon found in the pathogenesis of ocular diseases including DR. The NLR family of receptors are expressed in different eye tissues during pathological conditions suggesting their potential roles in dry eye, ocular infection, retinal ischemia, cataract, glaucoma, age-related macular degeneration (AMD), diabetic macular edema (DME) and DR. Our group is interested in studying the critical early components involved in the immune cell infiltration and inflammatory pathways involved in the progression of DR. Recently, we reported that NLRP3 inflammasome might play a pivotal role in the pathogenesis of DR. This comprehensive review summarizes the findings of NLRs expression in the ocular tissues with special emphasis on its presence in the retinal microglia and DR pathogenesis.

MHC Class II (DRB) Promoter Polymorphism and Its Role in Parasite Control among Malaria Patients

MHC class II (MHCII) molecules are cell surface glycoproteins that play an important role to develop adaptive immune responses. MHCII-disease association is not restricted to structural variation alone but also may extend to genetic variations, which may modulate gene expression. The observed variations in class II gene expression make it possible that the association of MHCII polymorphism with diseases may relate to the level of gene expression in addition to the restriction of response to Ag. Understanding the extent of, and the mechanisms underlying, transcription factor DNA binding variation is therefore key to elucidate the molecular determinants of complex phenotypes. In this study, we investigated whether single nucleotide polymorphisms in MHCII-DRB regulatory gene may be associated with clinical outcomes of malaria in Plasmodium-infected individuals. To this end, we conducted a case-control study to compare patients who had mild malaria with those patients who had asymptomatic Plasmodium infection. It demonstrates that GTAT haplotype exerts an increased DRB transcriptional activity, resulting in higher DRB expression and subsequently perturbed Ag presentation and T cell activation, higher TLR-mediated innate immune gene expression, and Ag clearance, so low parasitemia in comparison with haplotypes other than GTAT (GTAC, GGGT). Hence, we hypothesized that DRB gene promoter polymorphism might lead to altered DRB gene expression, which could possibly affect the TLR-triggered innate immune responses in malaria patients. These genetic findings may contribute to the understanding of the pathogenesis of malaria and will facilitate the rational vaccine design for malaria.

Neuronal NLRC5 regulates MHC class I expression in Neuro-2a cells and also during hippocampal development

Major histocompatibility Complex class I (MHC I) molecules are ubiquitously expressed, being found in most nucleated cells, where they are central mediators of both the adaptive and innate immune responses. Recent studies have shown that MHC I are also expressed in the developing brain where they participate in synapse elimination and plasticity. Up-regulation of MHC I within the developing brain has been reported, however, the mechanism(s) regulating this developmental up-regulation of neuronal MHC I remains unknown. Here, we show NLR family CARD domain containing 5 (NLRC5), a newly identified member of the NLR family, is widely expressed in hippocampal neurons, and the expression pattern of NLRC5 coincides with increased MHC I mRNA in the developing hippocampus. Using a luciferase assay in Neuro-2a cells we demonstrate that NLRC5 can induce the activation of MHC I and this induction requires the W/S-X-Y motif. Further studies show that transcription factors regulatory factor X (RFX) and CREB1, which bind to X1 and X2 box, are crucial for NLRC5-mediated induction. Moreover immunoprecipitation experiments reveal that NLRC5 interacts with RFX subunits RFX5 and RFXANK. Knockout of Nlrc5 dramatically impairs basal expression of MHC I in mouse hippocampus. Taken together, our findings identify NLRC5 as a key regulator of MHC I up-regulation in the developing hippocampus and suggest an important role for NLRC5 in neurons. Cover Image for this issue: doi: 10.1111/jnc.14729.

The genetic architecture of helminth-specific immune responses in a wild population of Soay sheep (Ovis aries)

Much of our knowledge of the drivers of immune variation, and how these responses vary over time, comes from humans, domesticated livestock or laboratory organisms. While the genetic basis of variation in immune responses have been investigated in these systems, there is a poor understanding of how genetic variation influences immunity in natural, untreated populations living in complex environments. Here, we examine the genetic architecture of variation in immune traits in the Soay sheep of St Kilda, an unmanaged population of sheep infected with strongyle gastrointestinal nematodes. We assayed IgA, IgE and IgG antibodies against the prevalent nematode Teladorsagia circumcincta in the blood plasma of > 3,000 sheep collected over 26 years. Antibody levels were significantly heritable (h² = 0.21 to 0.57) and highly stable over an individual’s lifespan. IgA levels were strongly associated with a region on chromosome 24 explaining 21.1% and 24.5% of heritable variation in lambs and adults, respectively. This region was adjacent to two candidate loci, Class II Major Histocompatibility Complex Transactivator (CIITA) and C-Type Lectin Domain Containing 16A (CLEC16A). Lamb IgA levels were also associated with the immunoglobulin heavy constant loci (IGH) complex, and adult IgE levels and lamb IgA and IgG levels were associated with the major histocompatibility complex (MHC). This study provides evidence of high heritability of a complex immunological trait under natural conditions and provides the first evidence from a genome-wide study that large effect genes located outside the MHC region exist for immune traits in the wild.

Understanding how immune responses vary in natural populations can give an insight into how infection affects the ability of hosts and parasites to survive and reproduce, and how this drives evolutionary and ecological dynamics. Yet, very little is known about how immune responses vary over an individual’s lifetime and how genes contribute to this variation under natural conditions. Our study investigates the genetic architecture of variation in three antibody types, IgA, IgE and IgG in a wild population of Soay sheep on the St Kilda archipelago in North-West Scotland. Using data collected over 26 years, we show that antibody levels have a heritable basis in lambs and adults and are stable over an individual’s lifetime. We also identify several genomic regions with large effects on immune responses. Our study offers the first insights into the genetic control of immunity in a wild population, which is essential to understand how immune profiles vary in challenging natural conditions and how natural selection maintains genetic variation in complex immune traits.

The Genetic Contribution to Type 1 Diabetes

PURPOSE OF REVIEW

To provide an updated summary of discoveries made to date resulting from genome-wide association study (GWAS) and sequencing studies, and to discuss the latest loci added to the growing repertoire of genetic signals predisposing to type 1 diabetes (T1D).

RECENT FINDINGS

Genetic studies have identified over 60 loci associated with T1D susceptibility. GWAS alone does not specifically inform on underlying mechanisms, but in combination with other sequencing and omics-data, advances are being made in our understanding of T1D genetic etiology and pathogenesis. Current knowledge indicates that genetic variation operating in both pancreatic β cells and in immune cells is central in mediating T1D risk. One of the main challenges is to determine how these recently discovered GWAS-implicated variants affect the expression and function of gene products. Once we understand the mechanism of action for disease-causing variants, we will be well placed to apply targeted genomic approaches to impede the premature activation of the immune system in an effort to ultimately prevent the onset of T1D.

Stem Cell Therapies for Treating Diabetes: Progress and Remaining Challenges

Restoration of insulin independence and normoglycemia has been the overarching goal in diabetes research and therapy. While whole-organ and islet transplantation have become gold-standard procedures in achieving glucose control in diabetic patients, the profound lack of suitable donor tissues severely hampers the broad application of these therapies. Here, we describe current efforts aimed at generating a sustainable source of functional human stem cell-derived insulin-producing islet cells for cell transplantation and present state-of-the-art efforts to protect such cells via immune modulation and encapsulation strategies.

Forkhead transcription factor FOXO3a mediates interferon-γ-induced MHC II transcription in macrophages

Macrophages are professional antigen-presenting cells relying on the expression of class II major histocompatibility complex (MHC II) genes. Interferon-γ (IFN-γ) activates MHC II transcription via the assembly of an enhanceosome centred on class II trans-activator (CIITA). In the present study, we investigated the role of the forkhead transcription factor FOXO3a in IFN- γ-induced MHC II transcription in macrophages. Knockdown of FOXO3a, but not FOXO1 or FOXO4, diminished IFN-γ-induced MHC II expression in RAW cells. On the contrary, over-expression of FOXO3a, but neither FOXO1 nor FOXO4, enhanced CIITA-mediated trans-activation of the MHC II promoter. IFN-γ treatment promoted the recruitment of FOXO3a to the MHC II promoter. Co-immunoprecipitation and RE-ChIP assays showed that FOXO3a was a component of the MHC II enhanceosome forming interactions with CIITA, RFX5, RFXB and RFXAP. FOXO3a contributed to MHC II transcription by altering histone modifications surrounding the MHC II promoter. Of interest, FOXO3a was recruited to the type IV CIITA promoter and directly activated CIITA transcription by interacting with signal transducer of activation and transcription 1 in response to IFN-γ stimulation. In conclusion, our data unveil a novel role for FOXO3a in the regulation of MHC II transcription in macrophages.

Major histocompatibility complex class II molecule in non-small cell lung cancer diagnosis, prognosis and treatment

Lung cancer is one of the commonest cancers in the world. More than 70% of lung cancer patients are diagnosed with non-small cell lung cancer (NSCLC). Major histocompatibility complex class II (MHC class II), an important component in antigen presenting process, usually expresses on professional antigen presenting cells (APCs), and it can be induced by interferon-γ (IFN-γ). MHC class II can be expressed by NSCLC cells. In NSCLC patients, the expression of MHC class II can be correlated with the outcome of anti-programmed death-1 (anti-PD-1) therapy. This review summarizes MHC class II expression in NSCLC and the correlation between MHC class II and NSCLC diagnosis, prognosis and therapy.

Antigen processing and presentation

Dendritic cells are at the center of immune responses. They are defined by their ability to sense the environment, take up and process antigen, migrate to secondary lymphoid organs, where they present antigens to the adaptive immune system. In particular, they present lipids and proteins from pathogens, which they encountered in peripheral tissues, to T cells in order to induce a specific effector immune response. These complex antigens need to be broken down into peptides of a certain length in association with Major Histocompatibility Complex (MHC) molecules. Presentation of MHC/antigen complexes alongside costimulatory molecules and secretion of proinflammatory cytokines will induce an appropriate immune response. This interaction between dendritic cells and T cells takes place at defined locations within secondary lymphoid organs. In this review, we discuss the current knowledge and recent advances on the cellular and molecular mechanisms that underlie antigen processing and the subsequent presentation to T lymphocytes.

NLRC5 deficiency has a moderate impact on immunodominant CD8+ T-cell responses during rotavirus infection of adult mice

The NOD-like receptor (NLR) family plays an important role in innate immunity. Class II transactivator and NOD-like receptor caspase activation and recruitment domain CARD containing 5 (NLRC5) are unusual members of the NLR family that instead of recognizing pathogen-associated or damage-associated molecular patterns, form enhanceosomes with adaptor molecules and modulate major histocompatibility complex (MHC) class II and MHC class I expression, respectively. While NLRC5 has been shown to play a role during intracellular pathogen infection and tumor cell immune evasion, its role in regulating antigen-specific CD8⁺ T-cell responses at the intestinal mucosa has not been investigated. Here, we take advantage of the rotavirus model in adult mice to dissect the impact of NLRC5 on CD8⁺ T-cell responses to this viral infection at the gut mucosa. We show that while Nlrc5^-/- mice exhibited normal proportions of T-cell subpopulations in the intraepithelial and lamina propria compartments, these mice had decreased baseline MHC class I expression on various immune cells in the lamina propria. Upon rotavirus infection, Nlrc5 deficiency resulted in impaired H2-K^b -restricted antigen-specific CD8⁺ T-cell responses, which were recapitulated in mice deficient for Nlrc5 within the dendritic cell compartment. The impaired CD8⁺ T-cell response in Nlrc5^-/- mice was not significant enough to impact viral titers, suggesting compensation in Nlrc5^-/- mice, perhaps as a result of higher numbers of activated B cells in the mesenteric lymph nodes and normal rotavirus-specific immunoglobulin A responses. Collectively, our results demonstrate a minor role for NLRC5 in modulating H2-K^b -restricted antigen-specific CD8⁺ T-cell responses in the small intestine during rotavirus infection in adult mice.

Crucial Role of Increased Arid3a at the Pre-B and Immature B Cell Stages for B1a Cell Generation

The Lin28b⁺Let7⁻ axis in fetal/neonatal development plays a role in promoting CD5⁺ B1a cell generation as a B-1 B cell developmental outcome. Here we identify the Let7 target, Arid3a, as a crucial molecular effector of the B-1 cell developmental program. Arid3a expression is increased at pro-B cell stage and markedly increased at pre-B and immature B cell stages in the fetal/neonatal liver B-1 development relative to that in the Lin28b⁻Let7⁺ adult bone marrow (BM) B-2 cell development. Analysis of B-lineage restricted Lin28b transgenic (Tg) mice, Arid3a knockout and Arid3a Tg mice, confirmed that increased Arid3a allows B cell generation without requiring surrogate light chain (SLC) associated pre-BCR stage, and prevents MHC class II cell expression at the pre-B and newly generated immature B cell stages, distinct from pre-BCR dependent B development with MHC class II in adult BM. Moreover, Arid3a plays a crucial role in supporting B1a cell generation. The increased Arid3a leads higher Myc and Bhlhe41, and lower Siglec-G and CD72 at the pre-B and immature B cell stages than normal adult BM, to allow BCR signaling induced B1a cell generation. Arid3a-deficiency selectively blocks the development of B1a cells, while having no detectable effect on CD5⁻ B1b, MZ B, and FO B cell generation resembling B-2 development outcome. Conversely, enforced expression of Arid3a by transgene is sufficient to promote the development of B1a cells from adult BM. Under the environment change between birth to adult, altered BCR repertoire in increased B1a cells occurred generated from adult BM. However, crossed with B1a-restricted V_H/D/J IgH knock-in mice allowed to confirm that SLC-unassociated B1a cell increase and CLL/lymphoma generation can occur in aged from Arid3a increased adult BM. These results confirmed that in fetal/neonatal normal mice, increased Arid3a at the pre-B cell and immature B cell stages is crucial for generating B1a cells together with the environment for self-ligand reactive BCR selection, B1a cell maintenance, and potential for development of CLL/Lymphoma in aged mice.

Class I transactivator, NLRC5: a central player in the MHC class I pathway and cancer immune surveillance

Major histocompatibility complex (MHC) class I and class II molecules play critical roles in the activation of the adaptive immune system by presenting antigens to CD8+ and CD4+ T cells, respectively. Although it has been well known that CIITA (MHC class II transactivator), an NLR (nucleotide-binding domain, leucine-rich-repeat containing) protein, as a master regulator of MHC class II gene expression, the mechanism of MHC class I gene transactivation was unclear. Recently, another NLR protein, NLRC5 (NLR family, CARD domain-containing 5), was identified as an MHC class I transactivator (CITA). NLRC5 is a critical regulator for the transcriptional activation of MHC class I genes and other genes involved in the MHC class I antigen presentation pathway. CITA/NLRC5 plays a crucial role in human cancer immunity through the recruitment and activation of tumor killing CD8+ T cells. Here, we discuss the molecular function and mechanism of CITA/NLRC5 in the MHC class I pathway and its role in cancer.

Targeting of the class II transactivator attenuates inflammation and neurodegeneration in an alpha-synuclein model of Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is characterized by intracellular alpha-synuclein (α-syn) inclusions, progressive death of dopaminergic neurons in the substantia nigra pars compacta (SNpc), and activation of the innate and adaptive immune systems. Disruption of immune signaling between the central nervous system (CNS) and periphery, such as through targeting the chemokine receptor type 2 (CCR2) or the major histocompatibility complex II (MHCII), is neuroprotective in rodent models of PD, suggesting a key role for innate and adaptive immunity in disease progression. The purpose of this study was to investigate whether genetic knockout or RNA silencing of the class II transactivator (CIITA), a transcriptional co-activator required for MHCII induction, is effective in reducing the neuroinflammation and neurodegeneration observed in an α-syn mouse model of PD.

METHODS

In vitro, we utilized microglia cultures from WT or CIITA -/- mice treated with α-syn fibrils to investigate inflammatory iNOS expression and antigen processing via immunocytochemistry (ICC). In vivo, an adeno-associated virus (AAV) was used to overexpress α-syn in WT and CIITA -/- mice as a model for PD. Concurrently with AAV-mediated overexpression of α-syn, WT mice received CIITA-targeted shRNAs packaged in lentiviral constructs. Immunohistochemistry and flow cytometry were used to assess inflammation and peripheral cell infiltration at 4 weeks post transduction, and unbiased stereology was used 6 months post transduction to assess neurodegeneration.

RESULTS

Using ICC and DQ-ovalbumin, we show that CIITA -/- microglial cultures failed to upregulate iNOS and MHCII expression, and had decreased antigen processing in response to α-syn fibrils when compared to WT microglia. In vivo, global knock-out of CIITA as well as local knockdown using lentiviral shRNAs targeting CIITA attenuated MHCII expression, peripheral immune cell infiltration, and α-syn-induced neurodegeneration.

CONCLUSION

Our data provide evidence that CIITA is required for α-syn-induced MHCII induction and subsequent infiltration of peripheral immune cells in an α-syn mouse model of PD. Additionally, we demonstrate that CIITA in the CNS drives neuroinflammation and neurodegeneration. These data provide further support that the disruption or modulation of antigen processing and presentation via CIITA is a promising target for therapeutic development in preclinical animal models of PD.

The discrepancy function of NLRC5 isoforms in antiviral and antibacterial immune responses

NOD-like receptors (NLRs) are a family of intracellular pattern recognition receptors (PRRs) that play critical roles in innate immunity against pathogens infection. NLRC5, the largest member of NLR family, has been characterized as a regulator of innate immunity and MHC class I expression. Alternative splicing of NLRC5 is only reported in human and zebrafish. However, the function of NLRC5 isoforms in the innate immune responses remains unknown. In the present study, we report the functional characterization of zfNLRC5a and zfNLRC5d, two splicing isoforms of zebrafish NLRC5. zfNLRC5a and zfNLRC5d are generated by exon skipping, and whose alternative splicing sites exist in the region of LRRs. Fluorescence microscopy showed that zfNLRC5 isoforms were located throughout the entire cell including nuclear staining. The expression of zfNLRC5 isoform was inducible in response to bacterial and viral infections. During SVCV infection, the in vitro and in vivo studies found that zfNLRC5d overexpression increased protection against viral infection; however zfNLRC5a overexpression had no significant effect on antiviral activity. Interestingly, zfNLRC5 isoforms but not zfNLRC5 were involved in transcriptional regulation of TLRs and NF-κB signaling. Overexpression of zfNLRC5 isoforms also contributed to negative regulation of antibacterial immune response, with the decreased expression of nfkbiaa (IκBα). All together, these results firstly demonstrate the function of NLRC5 isoforms in antiviral and antibacterial immune responses both in vitro and in vivo.

Effects of triptolide on the expression of MHC II in microglia in kainic acid‑induced epilepsy

The purpose of the present study was to determine whether triptolide (T10) had any effect on major histocompatibility complex class II (MHC II) expression in kainic acid (KA)‑activated microglia, and to investigate the underlying molecular mechanism. BV‑2 microglia were pretreated with T10 prior to activation with KA. The expression level of MHC II and class II transactivator (CIITA) mRNA was determined via reverse transcription‑polymerase chain reaction. The expression of MHC II, CIITA and the phosphorylation level of c‑Jun and proto‑oncogene c‑Fos (c‑Fos) was determined by western blotting. The protein expression level of MHC II was determined by immunocytochemistry. It was observed that the mRNA and protein levels of MHC II and CIITA were increased in KA‑activated BV‑2 microglia, and that this increase was almost completely eliminated by T10. AP‑1 is a family of homodimers or heterodimers, composed of Jun family and Fos family proteins. Sequence analysis revealed an AP‑1 DNA binding site in the promoter of CIITA. The phosphorylation of c‑Jun and c‑Fos was increased in KA‑activated microglia, while T10 was able to suppress the phosphorylation of c‑Jun and c‑Fos in KA‑activated microglia. These data suggested that T10 may exert suppressive effects on MHC II expression in KA‑activated microglia, and that the mechanism may involve the regulation of AP‑1 activity.

Prior to Peripheral Tolerance, Newly Generated CD4 T Cells Maintain Dangerous Autoimmune Potential: Fas- and Perforin-Independent Autoimmunity Controlled by Programmed Death-1

Lymphopenia can result from various factors, including viral infections, clinical interventions, or as a normal property of the fetal/neonatal period. T cells in a lymphopenic environment undergo lymphopenia-induced proliferation (LIP) to fill the available “niche” as defined by peptide–MHC and homeostatic cytokine resources. We recently reported systemic autoimmunity following reconstitution of the lymphoid compartment of Rag1^−/− mice with PD-1^−/− hematopoietic stem cells or by transfer of thymocytes, but not splenocytes, suggesting that programmed death-1 (PD-1) plays a crucial role in controlling recent thymic emigrants (RTE) and preventing autoimmunity upon their LIP. However, it is unclear whether RTE residing within the periphery of a lymphoreplete host maintain enhanced autoimmune generating potential or if this property only manifests if RTE experience a lymphopenic periphery immediately after export from the thymus. Furthermore, it is unclear which of a variety of T cell effector mechanisms generate pathology when control of RTE by PD-1 is lacking. Herein, we determined that PD-1 is upregulated on CD4 T cells undergoing the natural LIP characteristic of the neonatal period. Newly generated T cells lacking PD-1 maintained an enhanced autoimmune potential even after residence in a lymphoreplete periphery, emphasizing the importance of PD-1 in the establishment of peripheral tolerance. Neither Fas nor perforin-dependent killing mechanisms were required for autoimmunity, while host MHC-II expression was critical, suggesting that LIP-driven autoimmunity in the absence of PD-1 may primarily result from a CD4 T cell-mediated systemic cytokinemia, a feature potentially shared by other autoimmune or inflammatory syndromes associated with immune reconstitution and LIP.