MHC-I Molecules Research Articles

Chaperone-mediated MHC-I peptide exchange in antigen presentation.

This work focuses on molecules that are encoded by the major histocompatibility complex (MHC) and that bind self-, foreign- or tumor-derived peptides and display these at the cell surface for recognition by receptors on T lymphocytes (T cell receptors, TCR) and natural killer (NK) cells. The past few decades have accumulated a vast knowledge base of the structures of MHC molecules and the complexes of MHC/TCR with specificity for many different peptides. In recent years, the structures of MHC-I molecules complexed with chaperones that assist in peptide loading have been revealed by X-ray crystallography and cryogenic electron microscopy. These structures have been further studied using mutagenesis, molecular dynamics and NMR approaches. This review summarizes the current structures and dynamic principles that govern peptide exchange as these relate to the process of antigen presentation.

De novo identification of CD4+ T cell epitopes

CD4+ T cells recognize peptide antigens presented on class II major histocompatibility complex (MHC-II) molecules to carry out their function. The remarkable diversity of T cell receptor sequences and lack of antigen discovery approaches for MHC-II make profiling the specificities of CD4+ T cells challenging. We have expanded our platform of signaling and antigen-presenting bifunctional receptors to encode MHC-II molecules presenting covalently linked peptides (SABR-IIs) for CD4+ T cell antigen discovery. SABR-IIs can present epitopes to CD4+ T cells and induce signaling upon their recognition, allowing a readable output. Furthermore, the SABR-II design is modular in signaling and deployment to T cells and B cells. Here, we demonstrate that SABR-IIs libraries presenting endogenous and non-contiguous epitopes can be used for antigen discovery in the context of type 1 diabetes. SABR-II libraries provide a rapid, flexible, scalable and versatile approach for de novo identification of CD4+ T cell ligands from single-cell RNA sequencing data using experimental and computational approaches.

The CD4 transmembrane GGXXG and juxtamembrane (C/F)CV+C motifs mediate pMHCII-specific signaling independently of CD4-LCK interactions.

CD4+ T cell activation is driven by five-module receptor complexes. The T cell receptor (TCR) is the receptor module that binds composite surfaces of peptide antigens embedded within MHCII molecules (pMHCII). It associates with three signaling modules (CD3γε, CD3δε, and CD3ζζ) to form TCR-CD3 complexes. CD4 is the coreceptor module. It reciprocally associates with TCR-CD3-pMHCII assemblies on the outside of a CD4+ T cells and with the Src kinase, LCK, on the inside. Previously, we reported that the CD4 transmembrane GGXXG and cytoplasmic juxtamembrane (C/F)CV+C motifs found in eutherian (placental mammal) CD4 have constituent residues that evolved under purifying selection (Lee et al., 2022). Expressing mutants of these motifs together in T cell hybridomas increased CD4-LCK association but reduced CD3ζ, ZAP70, and PLCγ1 phosphorylation levels, as well as IL-2 production, in response to agonist pMHCII. Because these mutants preferentially localized CD4-LCK pairs to non-raft membrane fractions, one explanation for our results was that they impaired proximal signaling by sequestering LCK away from TCR-CD3. An alternative hypothesis is that the mutations directly impacted signaling because the motifs normally play an LCK-independent role in signaling. The goal of this study was to discriminate between these possibilities. Using T cell hybridomas, our results indicate that: intracellular CD4-LCK interactions are not necessary for pMHCII-specific signal initiation; the GGXXG and (C/F)CV+C motifs are key determinants of CD4-mediated pMHCII-specific signal amplification; the GGXXG and (C/F)CV+C motifs exert their functions independently of direct CD4-LCK association. These data provide a mechanistic explanation for why residues within these motifs are under purifying selection in jawed vertebrates. The results are also important to consider for biomimetic engineering of synthetic receptors.

The CD4 transmembrane GGXXG and juxtamembrane (C/F)CV+C motifs mediate pMHCII-specific signaling independently of CD4-LCK interactions

CD4+ T cell activation is driven by five-module receptor complexes. The T cell receptor (TCR) is the receptor module that binds composite surfaces of peptide antigens embedded within MHCII molecules (pMHCII). It associates with three signaling modules (CD3γε, CD3δε, and CD3ζζ) to form TCR-CD3 complexes. CD4 is the coreceptor module. It reciprocally associates with TCR-CD3-pMHCII assemblies on the outside of a CD4+ T cells and with the Src kinase, LCK, on the inside. Previously, we reported that the CD4 transmembrane GGXXG and cytoplasmic juxtamembrane (C/F)CV+C motifs found in eutherian (placental mammal) CD4 have constituent residues that evolved under purifying selection (Lee et al., 2022). Expressing mutants of these motifs together in T cell hybridomas increased CD4-LCK association but reduced CD3ζ, ZAP70, and PLCγ1 phosphorylation levels, as well as IL-2 production, in response to agonist pMHCII. Because these mutants preferentially localized CD4-LCK pairs to non-raft membrane fractions, one explanation for our results was that they impaired proximal signaling by sequestering LCK away from TCR-CD3. An alternative hypothesis is that the mutations directly impacted signaling because the motifs normally play an LCK-independent role in signaling. The goal of this study was to discriminate between these possibilities. Using T cell hybridomas, our results indicate that: intracellular CD4-LCK interactions are not necessary for pMHCII-specific signal initiation; the GGXXG and (C/F)CV+C motifs are key determinants of CD4-mediated pMHCII-specific signal amplification; the GGXXG and (C/F)CV+C motifs exert their functions independently of direct CD4-LCK association. These data provide a mechanistic explanation for why residues within these motifs are under purifying selection in jawed vertebrates. The results are also important to consider for biomimetic engineering of synthetic receptors.

Molecular patterns of resistance to immune checkpoint blockade in melanoma

Immune checkpoint blockade (ICB) has improved outcome for patients with metastatic melanoma but not all benefit from treatment. Several immune- and tumor intrinsic features are associated with clinical response at baseline. However, we need to further understand the molecular changes occurring during development of ICB resistance. Here, we collect biopsies from a cohort of 44 patients with melanoma after progression on anti-CTLA4 or anti-PD1 monotherapy. Genetic alterations of antigen presentation and interferon gamma signaling pathways are observed in approximately 25% of ICB resistant cases. Anti-CTLA4 resistant lesions have a sustained immune response, including immune-regulatory features, as suggested by multiplex spatial and T cell receptor (TCR) clonality analyses. One anti-PD1 resistant lesion harbors a distinct immune cell niche, however, anti-PD1 resistant tumors are generally immune poor with non-expanded TCR clones. Such immune poor microenvironments are associated with melanoma cells having a de-differentiated phenotype lacking expression of MHC-I molecules. In addition, anti-PD1 resistant tumors have reduced fractions of PD1+ CD8+ T cells as compared to ICB naïve metastases. Collectively, these data show the complexity of ICB resistance and highlight differences between anti-CTLA4 and anti-PD1 resistance that may underlie differential clinical outcomes of therapy sequence and combination.

NeoMUST: an accurate and efficient multi-task learning model for neoantigen presentation.

Accurate identification of neoantigens is important for advancing cancer immunotherapies. This study introduces Neoantigen MUlti-taSk Tower (NeoMUST), a model employing multi-task learning to effectively capture task-specific information across related tasks. Our results show that NeoMUST rivals existing algorithms in predicting the presentation of neoantigens via MHC-I molecules, while demonstrating a significantly shorter training time for enhanced computational efficiency. The use of multi-task learning enables NeoMUST to leverage shared knowledge and task dependencies, leading to improved performance metrics and a significant reduction in the training time. NeoMUST, implemented in Python, is freely accessible at the GitHub repository. Our model will facilitate neoantigen prediction and empower the development of effective cancer immunotherapeutic approaches.

Abstract 1362: IOMX-0675, a LILRB1 and LILRB2 cross-specific antibody, effectively repolarizes immunosuppressive myeloid cells and activates T cells leading to potent tumor cell killing

Abstract Recently, myeloid checkpoints in the tumor microenvironment have gained increased attention in the context of tumor immune evasion. LILRB1 (ILT2) and LILRB2 (ILT4) are immunosuppressive receptors of the leukocyte immunoglobulin-like receptor (LILR) family that recognize both classical and non-classical MHC-I molecules (e.g., HLA-G). While tumor-infiltrating myeloid cells express both LILRB1 and LILRB2, lymphoid cells are restricted to LILRB1 expression. LILRB1 and LILRB2 are frequently co-expressed with immune-activating LILR family members LILRA1 and LILRA3 in several tumor indications and upregulated in patients non-responsive to T cell checkpoint blockade. Furthermore, the non-classical MHC-I molecule HLA-G, a major ligand of LILRB1 and LILRB2 in the tumor environment, is overexpressed and associated with poor prognosis in multiple solid cancer types. IOMX-0675, a fully human, Fc-silenced, monoclonal immunoglobulin G1 (IgG1) antibody with a highly differentiated binding profile, that binds selectively with high affinity to the inhibitory receptors LILRB1 and LILRB2, while binding only weakly to the closely related immune-activating LILR family members LILRA1 and LILRA3, was identified from iOmx’ proprietary phage display library. A high-resolution Fab-based Octet assay was established to monitor the IOMX-0675-mediated blocking of LILRB1 or LILRB2 binding to HLA-G. The LILRB1/2 cross-specific antibody promotes phagocytic and pro-inflammatory activity of various macrophage subtypes, which was monitored by flow cytometry and cytokine profiling. In co-cultures of monocyte-derived macrophages with autologous T cells, IOMX-0675 shows high potential to reprogram dose-dependently immunosuppressive macrophage, to further activate pro-inflammatory macrophage subtypes and thereby rescues the activity of the lymphoid immune compartment. Even in environments dominated by LILRA1/A3, IOMX-0675 shows a strong binding capacity to the immunosuppressive LILRB1/B2 receptors and significantly repolarizes the immune environment. In summary, we discovered IOMX-0675, a cross-specific antibody antagonizing both LILRB1 and LILRB2 with high selectivity, that exhibits potent reprogramming of the immunosuppressive myeloid compartment and restores cytotoxic T cell activity in the tumor microenvironment. Negligible binding to immune-activating LILR family members by IOMX-0675 could unleash full anti-tumor activity. The differential binding profile of IOMX-0675 provides best-in-class potential and may maximize anti-tumor efficacy for the benefit of patients with high-unmet medical need, who are resistant to T cell checkpoint blockade. Citation Format: Christina Hartl, Jonas Zantow, Ilona-Petra Maser, Marisa Stebegg-Wagner, Simone Friedrich, Jonas Schilz, Stefan Kaden, Ronny Milde, Eugenia Korotkova, Michail Maraslis, Bettina Langer, Michal Swiat, Carmen Ginzel, Carmen Ammerhauser, Lucille Albert, Leonie Majunke, Alina Huth, Kritika Sudan, Murray Yule, Christine Rothe, Hannes Loferer, Maximilian Aigner, Alexander N. Marziale, Stefan Bissinger. IOMX-0675, a LILRB1 and LILRB2 cross-specific antibody, effectively repolarizes immunosuppressive myeloid cells and activates T cells leading to potent tumor cell killing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1362.

Abstract 2666: Genetic ablation of B2M leads to resistance to PD-1/PD-L1 blockade in vivo

Abstract Immune checkpoint inhibitors (ICIs) has revolutionized the treatment landscape of various cancers by reinvigorating the exhausted T cells in patients. However, the therapeutic efficacy is largely confined due to the primary or acquired resistance to anti-PD-1 (L1) therapy in many patients. Recently, the mechanisms of resistance to ICIs has been extensively elucidated from different aspects and emerging sequencing data from clinical samples has pointed to IFN-γ signaling defects and antigen presentation loss in patients who are resistant to PD-1(L1) blockade. The loss-of-function mutations in JAK1 and JAK2 results in lack of response to IFN-γ signaling and incapacity to upregulate PD-L1 and MHC-I, which subsequently leads to noninflammatory TMEs and resistance to anti-PD-1/PD-L1. The loss-of-function of B2M is likely a common resistance mechanism that the intratumoral cytotoxic CD8+ T cells are failed to be boosted owing to antigen presentation loss. In order to obtain higher clinical benefits in various cancers, it’s appealing and urgent to develop mechanism-based strategies to overcome resistance to ICI-based immunotherapy. To this end, we developed a genetically acquired resistant tumor model with B2M mutations in syngenic MC38 tumor cells using CRISPR/Cas9 technology, which is ‘hot’ tumor to PD-1/PD-L1 blockade. The expression of B2M was detected by western blotting and flow cytometry. Mouse B2M-knockout MC38 tumors became resistant to PD-1/PD-L1 blockade in vivo. Notably, we found a remarkable increase of CD8+ T cell infiltration in B2m-KO MC38 tumors in comparison to parental MC38 tumors upon anti-PD-1 treatment, which further explains that antigen presentation loss results in inactivation of cytotoxic CD8+ T cells within the tumor microenvironments (TMEs), subsequently leading to resistance and poor survival to ICI therapy.In summary, our data consistently indicated the importance of MHC-I expression in T cell activation in the TMEs and the possibility to dig out the pathway involved in MHC-I expression independent of IFN-γ signaling by CRISPR-based screening to overcome MHC-I deficiency-induced resistance in the future. In addition, it’s possible to leverage the cytotoxic NK cells and CD4+ T cells in antitumor immunity against MHC-II+ tumors even with the loss of MHC-I molecules. For example, high dose of IL-2RB-biased IL-2 agonist preferentially binding to the dimeric IL-2R can stimulate Teff and NK cells independent of immune checkpoint expression. Likewise, cytokine modified anti-PD-1 fusion formulation like anti-PD-1-IL-2 mutein and anti-PD-1-IL-15 mutein are promising to overcome the resistance. Furthermore, it has been suggested that the resistance due to genetic mutations of MHC-I could be overcome by combining NF-B targeted therapies. Citation Format: Yanlei Zhang, Hechun Ma, Boang Han, Yi Li, Ping Yang, Zhen Li, Dongxiao Feng, Lei Ci, Ruilin Sun, Daniel X. He. Genetic ablation of B2M leads to resistance to PD-1/PD-L1 blockade in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2666.

Abstract 4986: Single-cell multimodal characterization of ovarian cancer microenvironment under neoadjuvant niraparib treatment informs an effective therapeutic strategy of suppressing HRD-dependent eTreg hyper-expansion

Abstract Homologous recombination deficiency (HRD) is a widespread hallmark in cancer, rendering tumors susceptible to PARP inhibition. Despite this well-established tumor-intrinsic vulnerability, the effects of HRD and related therapies on the tumor microenvironment (TME) remain poorly understood. In this study, utilizing single-cell RNA and T cell receptor profiling (scRNA/TCR-seq), we characterized 79 high-grade serous ovarian cancer (HGSOC) samples, both pre- and post-treatment, from 46 patients treated with neoadjuvant niraparib or chemotherapy in a phase II clinical trial (NCT04507841). This effort established the most comprehensive HGSOC TME atlas to date, encompassing over 700,000 cells. By integrating multiplex immunofluorescence imaging, flow cytometry, and bulk TCR-seq data from additional tumors and matched peripheral blood samples, we systematically assessed HRD-induced and treatment-perturbed dynamics of tumor-infiltrating and circulating immune cells. Surprisingly, among over 120 cell states across 10 cell types, effector regulatory CD4+ T cells (eTreg) exhibited the strongest enrichment in treatment-naïve HRD tumors and a marked treatment-induced reduction. Further analyses of transcriptional states and clonal kinetics revealed HRD-driven functional coordination between eTregs and exhausted CD8+ T cells (Tex), both displaying uniquely heightened tumor reactivity signatures and clonal co-expansions. The intra-population heterogeneity analysis of Tregs and Texs further demonstrated an effectiveness gradient, wherein the terminal subsets had a greater presence in HRD and were reversed by both niraparib and chemotherapy treatments. Delineating the clonal evolution of Tregs and Texs, we identified their notable crosstalk with other tumor-infiltrating T cell populations while remaining remarkably isolated from the peripheral blood repertoire, in line with their terminally differentiated status. Furthermore, we observed widespread, chronic activation of interferon signaling across TME components, downstream of HRD. This orchestrated CD4+ T cell anergy induction into Tregs, mainly through direct engagement by cancer cells that upregulated MHC-II molecules but lacked essential co-stimulatory ligands. Finally, we experimentally validated a therapeutic strategy to conjunctively and effectively break down these factors in HGSOC by combining PARP inhibition and eTreg deletion through a humanized therapeutic anti-CCR8 antibody in multiple syngeneic HGSOC mouse models. Our study unravels a key immunoregulatory role of eTregs in the HGSOC TME amplified by HRD. These findings underscore the underappreciated value of eTreg-focused therapeutics as novel immunotherapies for HGSOC and other genomically unstable cancers. Citation Format: Yikai Luo, Yu Xia, Dan Liu, Xiong Li, Huayi Li, Yi Zhao, Ding Ma, Yong Fang, Han Liang, Qinglei Gao. Single-cell multimodal characterization of ovarian cancer microenvironment under neoadjuvant niraparib treatment informs an effective therapeutic strategy of suppressing HRD-dependent eTreg hyper-expansion [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4986.

Long-chain acyl-CoA synthetase 4-mediated mitochondrial fatty acid metabolism and dendritic cell antigen presentation.

This study aims to investigate the role of Acyl-CoA synthetase 4 (ACSL4) in mediating mitochondrial fatty acid metabolism and dendritic cell (DC) antigen presentation in the immune response associated with asthma. RNA sequencing was employed to identify key genes associated with mitochondrial function and fatty acid metabolism in DCs. ELISA was employed to assess the levels of fatty acid metabolism in DCs. Mitochondrial morphology was evaluated using laser confocal microscopy, structured illumination microscopy, and transmission electron microscopy. Flow cytometry and immunofluorescence were utilized to detect changes in mitochondrial superoxide generation in DCs, followed by immunofluorescence co-localization analysis of ACSL4 and the mitochondrial marker protein COXIV. Subsequently, pathological changes and immune responses in mouse lung tissue were observed. ELISA was conducted to measure the levels of fatty acid metabolism in lung tissue DCs. qRT-PCR and western blotting were employed to respectively assess the expression levels of mitochondrial-associated genes (ATP5F1A, VDAC1, COXIV, TFAM, iNOS) and proteins (ATP5F1A, VDAC1, COXIV, TOMM20, iNOS) in lung tissue DCs. Flow cytometry was utilized to analyze changes in the expression of surface antigens presented by DCs in lung tissue, specifically the MHCII molecule and the co-stimulatory molecules CD80/86. The sequencing results reveal that ACSL4 is a crucial gene regulating mitochondrial function and fatty acid metabolism in DCs. Inhibiting ACSL4 reduces the levels of fatty acid oxidases in DCs, increases arachidonic acid levels, and decreases A-CoA synthesis. Simultaneously, ACSL4 inhibition leads to an increase in mitochondrial superoxide production (MitoSOX) in DCs, causing mitochondrial rupture, vacuolization, and sparse mitochondrial cristae. In mice, ACSL4 inhibition exacerbates pulmonary pathological changes and immune responses, reducing the fatty acid metabolism levels within lung tissue DCs and the expression of mitochondria-associated genes and proteins. This inhibition induces an increase in the expression of MHCII antigen presentation molecules and co-stimulatory molecules CD80/86 in DCs. The research findings indicate that ACSL4-mediated mitochondrial fatty acid metabolism and dendritic cell antigen presentation play a crucial regulatory role in the immune response of asthma. This discovery holds promise for enhancing our understanding of the mechanisms underlying asthma pathogenesis and potentially identifying novel targets for its prevention and treatment.

Abstract 2443 Expanding the applications of open MHC-I molecules for enhanced thermostability and peptide loading to HLA-A*11:01 and HLA-C*07:02 allotypes

Abstract 2443 Expanding the applications of open MHC-I molecules for enhanced thermostability and peptide loading to HLA-A*11:01 and HLA-C*07:02 allotypes

Tissue-plasminogen activator effects on the phenotype of splenic myeloid cells in acute inflammation

Tissue-plasminogen activator (tPA) is a serine protease well known for its fibrinolytic function. Recent studies indicate that tPA could also modulate inflammation via plasmin generation and/or by receptor mediated signalling in vitro. However, the contribution of tPA in inflammatory processes in vivo has not been fully addressed. Therefore, using tPA-deficient mice, we have analysed the effect of lipopolysaccharide (LPS) challenge on the phenotype of myeloid cells including neutrophils, macrophages and dendritic cells (DCs) in spleen. We found that LPS treatment upregulated the frequency of major histocompatibility class two (MHCII+) macrophages but also, paradoxically, induced a deep downregulation of MHCII molecule level on macrophages and on conventional dendritic cells 2 (cDC2). Expression level of the CD11b integrin, known as a tPA receptor, was upregulated by LPS on MHCII+ macrophages and cDC2, suggesting that tPA effects could be amplified during inflammation. In tPA−/− mice under inflammatory conditions, expression of costimulatory CD86 molecules on MHCII+ macrophages was decreased compared to WT mice, while in steady state the expression of MHCII molecules was higher on macrophages. Finally, we reported that tPA deficiency slightly modified the phenotype of DCs and T cells in acute inflammatory conditions. Overall, our findings indicate that in vivo, LPS injection had an unexpectedly bimodal effect on MHCII expression on macrophages and DCs that consequently might affect adaptive immunity. tPA could also participate in the regulation of the T cell response by modulating the levels of CD86 and MHCII molecules on macrophages.

Structure-aware deep model for MHC-II peptide binding affinity prediction

The prediction of major histocompatibility complex (MHC)-peptide binding affinity is an important branch in immune bioinformatics, especially helpful in accelerating the design of disease vaccines and immunity therapy. Although deep learning-based solutions have yielded promising results on MHC-II molecules in recent years, these methods ignored structure knowledge from each peptide when employing the deep neural network models. Each peptide sequence has its specific combination order, so it is worth considering adding the structural information of the peptide sequence to the deep model training. In this work, we use positional encoding to represent the structural information of peptide sequences and validly combine the positional encoding with existing models by different strategies. Experiments on three datasets show that the introduction of position-coding information can further improve the performance built upon the existing model. The idea of introducing positional encoding to this field can provide important reference significance for the optimization of the deep network structure in the future.

Abstract C019: The circadian master regulator BMAL1 blocks immune cell recognition of pancreatic ductal adenocarcinomas by reducing proteasome activity and MHC1 cell surface localization

Abstract Many tumor types, including pancreatic adenocarcinomas, have dysregulated circadian rhythms. Here we show that the master regulator of circadian control, BMAL1, is overexpressed in pancreatic ductal adenocarcinoma (PDAC) relative to normal tissue and plays a role in protecting PDAC cells from recognition by the immune system. Using CRISPR-generated knockout (KO) cell lines, we evaluated the cells ability to create liver metastasis using a splenic metastasis assay and found that loss of Bmal1 KO abrograted metastasis. We hypothesized that could be through an immune mediated mechanism and evaluated the Bmal KO cells for their expression of cell surface MHCI. Remarkably loss of Bmal1 led to a significant increase in cell surface MHCI expression. This was due to a change in localization of the MHCI molecule. Proper localization of MHC1 is known to depend upon proteasome-generated peptides, and we found that loss of Bmal1 increased proteosomal activity. We used Cut and Run to demonstrate that Bmal1 binds directly to the promoters for core components of the proteosome. Taken together these studies implicate Bmal1 in regulating anti-tumor immunity in PDAC through its regulation of protesomal activity and MHC1 surface expression. This is a novel function for a circadian rhythm gene in PDAC biology. Citation Format: Orjola Prela, Lan Wang, Ching-Hua Shih, Juliana Cazarin de Menezes, Brian Altman, Paula M. Vertino, Chris R. Harris, Darren R. Carpizo. The circadian master regulator BMAL1 blocks immune cell recognition of pancreatic ductal adenocarcinomas by reducing proteasome activity and MHC1 cell surface localization [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr C019.

Construction of an ER stress-related prognostic signature for predicting prognosis and screening the effective anti-tumor drug in osteosarcoma

BackgroundOsteosarcoma is the most common malignant primary bone tumor in infants and adolescents. The lack of understanding of the molecular mechanisms underlying osteosarcoma progression and metastasis has contributed to a plateau in the development of current therapies. Endoplasmic reticulum (ER) stress has emerged as a significant contributor to the malignant progression of tumors, but its potential regulatory mechanisms in osteosarcoma progression remain unknown.MethodsIn this study, we collected RNA sequencing and clinical data of osteosarcoma from The TCGA, GSE21257, and GSE33382 cohorts. Differentially expressed analysis and the least absolute shrinkage and selection operator regression analysis were conducted to identify prognostic genes and construct an ER stress-related prognostic signature (ERSRPS). Survival analysis and time dependent ROC analysis were performed to evaluate the predictive performance of the constructed prognostic signature. The “ESTIMATE” package and ssGSEA algorithm were utilized to evaluate the differences in immune cells infiltration between the groups. Cell-based assays, including CCK-8, colony formation, and transwell assays and co-culture system were performed to assess the effects of the target gene and small molecular drug in osteosarcoma. Animal models were employed to assess the anti-osteosarcoma effects of small molecular drug.ResultsFive genes (BLC2, MAGEA3, MAP3K5, STC2, TXNDC12) were identified to construct an ERSRPS. The ER stress-related gene Stanniocalcin 2 (STC2) was identified as a risk gene in this signature. Additionally, STC2 knockdown significantly inhibited osteosarcoma cell proliferation, migration, and invasion. Furthermore, the ER stress-related gene STC2 was found to downregulate the expression of MHC-I molecules in osteosarcoma cells, and mediate immune responses through influencing the infiltration and modulating the function of CD8+ T cells. Patients categorized by risk scores showed distinct immune status, and immunotherapy response. ISOX was subsequently identified and validated as an effective anti-osteosarcoma drug through a combination of CMap database screening and in vitro and in vivo experiments.ConclusionThe ERSRPS may guide personalized treatment decisions for osteosarcoma, and ISOX holds promise for repurposing in osteosarcoma treatment.

Crosstalk between CD8+ T cells and mesenchymal stromal cells in intestine homeostasis and immunity.

The intestine represents the most complex cellular network in the whole body. It is constantly faced with multiple types of immunostimulatory agents encompassing from food antigen, gut microbiome, metabolic waste products, and dead cell debris. Within the intestine, most T cells are found in three primary compartments: the organized gut-associated lymphoid tissue, the lamina propria, and the epithelium. The well-orchestrated epithelial-immune-microbial interaction is critically important for the precise immune response. The main role of intestinal mesenchymal stromal cells is to support a structural framework within the gut wall. However, recent evidence from stromal cell studies indicates that they also possess significant immunomodulatory functions, such as maintaining intestinal tolerance via the expression of PDL1/2 and MHC-II molecules, and promoting the development of CD103+ dendritic cells, and IgA+ plasma cells, thereby enhancing intestinal homeostasis. In this review, we will summarize the current understanding of CD8+ T cells and stromal cells alongside the intestinal tract and discuss the reciprocal interactions between T subsets and mesenchymal stromal cell populations. We will focus on how the tissue residency, migration, and function of CD8+ T cells could be potentially regulated by mesenchymal stromal cell populations and explore the molecular mediators, such as TGF-β, IL-33, and MHC-II molecules that might influence these processes. Finally, we discuss the potential pathophysiological impact of such interaction in intestine hemostasis as well as diseases of inflammation, infection, and malignancies.

How to Predict Binding Specificity and Ligands for New MHC-II Alleles with MixMHC2pred.

MHC-II molecules are key mediators of antigen presentation in vertebrate species and bind to their ligands with high specificity. The very high polymorphism of MHC-II genes within species and the fast-evolving nature of these genes across species has resulted in tens of thousands of different alleles, with hundreds of new alleles being discovered yearly through large sequencing projects in different species. Here we describe how to use MixMHC2pred to predict the binding specificity of any MHC-II allele directly from its amino acid sequence. We then show how both MHC-II ligands and CD4+ T cell epitopes can be predicted in different species with our approach. MixMHC2pred is available at http://mixmhc2pred.gfellerlab.org/ .

Modern ideas about the etiopathogenesis of rheumatoid arthritis

This review reflects modern ideas about the etiology and pathogenesis of Rheumatoid arthritis (RA). The disease is believed to be caused by various external or internal stress factors in individuals with a genetic predisposition. Under modern concepts, RA is an autoimmune disease, and the basis of its pathogenesis is the defects of the regulatory mechanisms providing the activation of the immune system against various stimuli. The onset of RA is in the peripheral lymphoid organs. Dendritic cells activate T-lymphocytes, activating B-lymphocytes through cytokines and costimulatory molecules, and cause the synthesis of autoantibodies, the accumulation of immune complexes in the joints, and the development of rheumatoid synovitis. B-lymphocytes secrete rheumatoid factor (RF), antibodies to cyclic citrulline peptide (ACCP), and proinflammatory cytokines and also activate T-lymphocytes by indicating signaling molecules. During T-lymphocyte activation, CD4+ Th-cells interact with HLA, MHC-II molecules, and costimulatory molecules located on the surface of antigen-presenting cells. This interaction activates a signaling pathway leading to the maturation of CD4+ cells, resulting in the activation of pro-inflammatory CD8+ T-lymphocytes. CD4+ Th cells also play an important role in RA regeneration through the secretion of cytokines and chemokines, the important immunomodulators of cellular immunity.

Arsenic Exposure Induces Neuro-immune Toxicity in the Cerebral Cortex and the Hippocampus via Neuroglia and NLRP3 Inflammasome Activation in C57BL/6 Mice.

This study aimed to examine the immuntoxic effects of arsenic in the nervous system. Our results showed that arsenic increased corticocerebral and hippocampal weights (p < 0.05). Morris water maze tests revealed that arsenic significantly increased the time spent in latency to platform on the fourth day in 50mg/L arsenic exposure and the fifth day in 25 and 50mg/L arsenic exposure, as well as reduced the path length in target quadrant, time spent in target quadrant, and crossing times of the platform (p < 0.05). Hematoxylin-eosin staining showed that the vacuolated degeneration and pyknosis was found in the cerebral cortex and hippocampus of arsenic-treated mice. The mRNA levels of corticocerebral and hippocampal brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) were decreased in the 50mg/L arsenic-treated group (p < 0.05). In addition, immunofluorescence staining showed that 25 and 50mg/L arsenic all increased the expression of CD11b and glial fibrillary acidic protein (GFAP) in the cerebral cortex and hippocampus (p < 0.05). Arsenic markedly raised antigen-presenting molecule MHCII and CD40 mRNA levels in the cerebral cortex and hippocampus and upregulated the cell chemokine receptor 5 (CCR5) and CCR7 mRNA levels in the cerebral cortex at the 50mg/L arsenic group, and increased the CCR7 mRNA levels in the hippocampus at the 25 and 50mg/L arsenic groups (p < 0.05). Arsenic activated the nucleotide-binding domain-like receptor protein-3 (NLRP3) inflammasome, and enhanced its upstream promoter NF-κB protein level and downstream regulators IL-18 mRNA levels. Collectively, these results provide new evidences for the neuro-immune toxicity of arsenic.

The Modulation of in Vitro Differentiation of Monocyte-derived Macrophage by Trypanosoma evansi Antigens in the Dromedary Camel

Studies on the camel immune response to Trypanosoma (T.) evansi, the causative agent of Surra, are very limited. In the present study, flow cytometry was employed to investigate the modulatory effects of different T. evansi antigens on the in vitro differentiation of camel blood monocytes into macrophages. For this, in vitro, separated camel monocytes were differentiated into monocyte-derived macrophages (MDM) in the presence or absence (control) of formalin-fixed (inactivated) T. evansi whole parasite (T. evansi group) or the purified Ro Tat 1.2 antigen (Ro Tat 1.2 group). The analysis of the antimicrobial functions of MDM (phagocytosis and reactive oxygen species (ROS) production) revealed reduced phagocytosis activity of camel MDM generated in the presence of T. evansi antigens. In addition, a lack of ROS-response was observed in camel MDM generated in the presence of T. evansi antigens after stimulation with PMA. These results indicated a compromising effect of T. evansi on the innate defense mechanisms in camels. Phenotypic analysis revealed the upregulation of major histocompatibility complex (MHC) class II molecules together with the lower abundance of the scavenger receptor for haptoglobin–hemoglobin complexes (CD163) on MDM generated in the presence of whole T. evansi parasites, indicating a polarizing effect of T. evansi on the differentiation of camel monocytes into an M1 phenotype. However, the reduced antimicrobial functions of these cells argue against their pro-inflammatory nature. Although both MDM generated in the presence of whole T. evansi antigens or their purified Ro Tat 1.2 proteins indicated similar expression levels of CD14 and MHCII molecules, the different abundance of the cell surface molecules CD172a, CD163, CD45, and CD44 indicated different phenotypes of the two MDMs. The results of the present study revealed compromising effects of T. evansi antigens on camel macrophages differentiated in vitro from blood monocytes. Whether these effects contribute to the in vivo pathogenesis of T. evansi in camels remains to be determined in future studies.