MHC-I Molecules Research Articles

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.

Immunophenotype of dendritic cell differentiation markers in breast cancer in in-vitro conditions

BACKGROUND: During maturation, dendritic cells begin to synthesize peptides that include the major histocompatibility complex MHC-II molecules, costimulatory molecules CD40+, CD80+, and CD86+, as well as CD83+ proteins. In cancer patients, dendritic cells dysfunction can lead to serious consequences in the form of deficiency of antitumor immunity, tumor progression, and decreased response to immunotherapy. All this is important to take into account to rethink the tumor immunotherapy strategy. Thus, approaches aimed at enhancing the viability of dendritic cells and preventing their dysfunction and polarization should be considered as a necessary step in order to increase the effectiveness of dendritic cell vaccines.&#x0D; AIM: To evaluate the expression characteristics of differentiation markers of dendritic cell maturation obtained from peripheral blood monocytes under culture conditions in patients with breast cancer.&#x0D; MATERIALS AND METHODS: With informed voluntary consent, 19 patients diagnosed with breast cancer were examined. Mononuclear cells were isolated on a Ficoll density gradient. For adhesion of monocytes to the bottom of 75 cm2 culture flasks, they were pre-incubated for 1.5 hours in conditions of 5% CO2 at 37 ℃. Growth and differentiation factors — GM-CSF (40 µl) and IL-٤ (٤٠ µl) — were added to the attached monocytes on the 1st, 3rd and 5th days of cultivation. Immunophenotyping of dendritic cells was carried out on days 7 and 9 of cultivation using flow cytometry.&#x0D; RESULTS: Flow cytometry data indicate that the viability of cultured dendritic cells in cancer patients is significantly reduced on day 9 compared to day 7 of cultivation. On day 9, there was a significant increase in CD80+ expression (2.40, p=0.028) and a decrease in CD83+ (1.65, p=0.036) compared to day 7.&#x0D; CONCLUSION: In general, significant signs of maturation were observed: loss of the monocyte marker CD14+, increased expression of CD80+, CD83+, CD86+ — the main markers. A decrease in CD83+ can be considered as a suppression of excessive activation of immune responses. In the future, a more in-depth study of the characteristics of maturation and activation of cultured dendritic cells is necessary to understand the mechanisms and factors influencing the decrease in the effectiveness of immunotherapy with an autologous dendritic cell vaccine.

De novo design of a protein binder against Staphylococcus enterotoxin B

Staphylococcus enterotoxin B (SEB) interacts with MHC-II molecules to overactivate immune cells and thereby to produce excessive pro-inflammatory cytokines. Disrupting the interactions between SEB and MHC-II helps eliminate the lethal threat posed by SEB. In this study, a de novo computational approach was used to design protein binders targeting SEB. The MHC-II binding domain of SEB was selected as the target, and the possible promising binding mode was broadly explored. The obtained original binder was folded into triple-helix bundles and contained 56 amino acids with molecular weight 5.9 kDa. The interface of SEB and the binder was highly hydrophobic. ProteinMPNN optimization further enlarged the hydrophobic region of the binder and improved the stability of the binder-SEB complex. In vitro study demonstrated that the optimized binder significantly inhibited the inflammatory response induced by SEB. Overall, our research demonstrated the applicability of this approach in de novo designing protein binders against SEB, and thereby providing potential therapeutics for SEB induced diseases.

Deciphering Antigen Specificity of Protective Regulatory T Cell Clones in Patients after Allogeneic Stem Cell Transplantation

Introduction: Clonal expansion of donor regulatory T cells (Tregs) in recipients of allogeneic stem cell transplantations (allo-SCT) is associated with the absence of acute graft-versus-host disease (aGVHD). Therefore, we hypothesize that antigen-specific donor Tregs prevent aGVHD. In this project, we aim to identify the cognate antigen of expanded Treg clones in patients after allo-SCT. Methods: We recruited 177 consecutive patients undergoing allo-SCT for acute myeloid leukemia without severe infection and CMV-reactivation for this study. Healthy adults matching patients' sex and age served as the control group. We sorted CD3 +CD4 +CD25 hiCD127 low Tregs from peripheral blood mononuclear cell samples collected early after transplantation (21 to 36 days, median 27 days), and we performed single-cell RNA sequencing (scRNAseq) to profile Treg transcriptome including both TCR alpha and beta chain. To determine the antigen specificity of a given TCR, we adapted a cytokine-capturing antigen-screening system (Lee and Meyerson, Sci Immunol, 2021). We built the system by 1) expressing designated TCRαβ chains in Jurkat cells, and 2) expressing cell-surface interleukin-2 capture mAb, corresponding MHC-II molecules, and CD74-fused epitope libraries in HEK293T cells serving as antigen-presenting cells (APCs). By co-culturing both modified cell lines, we can perform high-throughput screening of pooled candidates. To obtain epitope-encoding minigenes, we either used RNA fragmentation to generate candidates randomly or customized oligonucleotide synthesis to encode the tiled human proteome. To scale down the diversity of the synthetic library, we utilized NetMHCIIpan (DTU Health Tech) for MHC-II binding affinity prediction. By sequencing the CD74-fused minigene after screening out APCs with the highest cytokine intensity on the cell surface, we can decode the peptide sequence recognized by the given TCR. We have validated the cytokine-capturing antigen-screening system using a CMV-specific TCR and its cognate antigen. Results: In total, we analyzed six patients with and six patients without aGVHD. ScRNAseq showed that the FOXP3 + Treg population in patients without aGVHD shared more transcriptional similarities with healthy control as compared to patients with aGVHD. Due to lymphocytopenia, Tregs are extremely low in numbers early after allo-SCT, but clustering analysis revealed highly clonal expanded populations of Tregs with various degrees of activation. Notably, one patient without aGVHD was found to have a distinct Treg-dominant CD4 population, and a markedly abundant Treg clone (&amp;gt;15% of the entire Treg repertoire) was found to be parts of both FOXP3 + and FOXP3 - clusters. We then transduced the most abundant TCR into JM-T, the TCR-deficient Jurkat cell. We used an RNA-fragmented randomized library for the first screening, in which we identified one shared epitope in three independent screenings of high frequency. We then moved on to perform screenings for synthesized candidate pools predicted by NetMHCIIpan, representing human proteome and common post-allo-SCT infections. Currently, we are analyzing sequencing reads from parallel screenings and attempting direct expansion of IL-2 + sort-outs. Conclusion: By expanding our established screening system, we aim to elucidate the antigens of multiple clonal expanded TCR candidates from the same patient. Identification of specific antigens leading to clonal Treg expansion and protection from GVHD holds the potential for the development of targeted cell therapies.

LSD1 Inhibition Enhances Antigen Presentation and Co-Stimulation in AML to Promote T Cell-Mediated Anti-Leukemia Immune Responses

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) can provide a curative treatment option for acute myeloid leukemia (AML). Donor T cells play an important role in the curative potential of allo-HSCT by recognizing and eliminating residual leukemic cells, inducing the desirable graft-versus-leukemia (GVL) effect. Evading from this effect of donor T cell immune surveillance through the downregulation of human leukocyte antigen class II (HLA-II) molecules has been shown to contribute to AML relapse after allo-HSCT. Lysine-specific demethylase 1 (LSD1) is an emerging epigenetic therapeutic target in AML due to its role in regulating myeloid differentiation pathways. We hypothesized that LSD1 inhibition has the potential to enhance anti-leukemic immune responses by differentiating AML cells and inducing the acquisition of markers typical for antigen-presenting cells. We have studied these effects by treating human AML cell lines with the LSD1 inhibitor bomedemstat and investigated the expression of antigen-presenting molecules by flow cytometry and quantitative PCR (qPCR). At a concentration of 100 nM, bomedemstat upregulated the expression of CIITA by a log2 fold change of 2.23 ± 0.68 (p &amp;lt; 0.01) in OCI-AML3, 2.17 ± 0.28 (p &amp;lt; 0.01) in HL60 and 1.80 ± 0.67 (p &amp;lt; 0.05) in MOLM-13. To assess if the observed upregulation of CIITA can lead to a re-expression of HLA-DR in these HLA-DR negative cell lines, we then treated these cell lines with 100 nM of bomedemstat with additional IFN-γ stimulation. Expression of HLA-DR and the co-stimulatory molecule CD86 was determined by flow cytometry. Bomedemstat increased the expression of HLA-DR and CD86 across all three cell lines leading to the generation of 26.63 ± 3.07% (p &amp;lt; 0.0001) HLA-DR +/CD86 + cells in OCI-AML3, 4.19 ± 1.68% (p &amp;lt; 0.001) HLA-DR +/CD86 + cells in HL-60 and 14.67 ± 2.03% (p &amp;lt; 0.001) HLA-DR +/CD86 + cells in MOLM-13. We further assessed the effects of bomedemstat treatment on cytokine production by qPCR. Notably, bomedemstat treatment increased the expression of CXCL-10 by a log2 fold change of 2.59 ± 0.66 (p &amp;lt; 0.001) in MOLM-13 and 4.12 ± 0.88 (p &amp;lt; 0.001) in HL-60 at 100 nM concentration. The upregulation of CXCL-10 was also validated using bead-based ELISA assays. To investigate the molecular mechanism of the observed concomitant upregulation of MHC-II molecules and CD86, we then used murine myeloid progenitor cells transformed by overexpression of Hoxa9 and Meis1 (H9M) or MN1. In H9M-transformed cells, bomedemstat concurrently upregulated MHC-II (I-A/I-E) and CD86 even in the absence of IFN-γ stimulation, leading to an increase in MHC-II +/CD86 + cells from 2.52 ± 1.22% at baseline to 29.95 ± 14.11 (p &amp;lt; 0.05). This effect was not observed in MN1-transformed cells. H9M-transformed progenitor cells from Irf8 knockout mice (H9M- Irf8-KO) did not show any upregulation of MHC-II, pointing towards a role for Irf8 in this process. To interrogate whether the concurrent upregulation of MHC-II and CD86 can enhance CD4 + T cell activation, we used ovalbumin-expressing H9M-transformed cells that were co-cultured with OT-II T cells after bomedemstat treatment. We could show that bomedemstat-treatment enhanced the ability of H9M-OVA cells to activate T cells as demonstrated by an enhanced expression of the T cell activation markers CD25 and CD69. Furthermore, bomedemstat also increased the immune killing of OVA-peptide pulsed H9M cells at an effector-to-target (E:T) ratio of 1:1 from 1.12 ± 4.01 to 19.70 ± 6.20% (p &amp;lt; 0.01). It also enhanced the killing of OVA-expressing H9M cells from 5.80 ± 2.95% to 17.70 ± 3.16% (p &amp;lt; 0.05). No significant killing effect was observed for MN1 cells. In conclusion, we demonstrate both phenotypically and functionally that LSD1 inhibition by bomedemstat can enhance the immunogenicity of human and murine AML models. These findings point towards a potential role of LSD1 inhibition as a maintenance therapy after allo-HSCT.

The Effects of IL-23/IL-18-Polarized Neutrophils on Renal Ischemia-Reperfusion Injury and Allogeneic-Skin-Graft Rejection in Mice.

Neutrophils display heterogeneity and plasticity with different subgroups and immune-regulatory functions under various surrounding conditions. Neutrophils induced by IL-23/IL-18 (referred to N(IL-23+IL-18) neutrophils) have a unique gene-expression profile, with highly expressing IL-17, MHC-II, and costimulatory molecules. The adoptive transfer of N(IL-23+IL-18) neutrophils significantly increased the pathogenesis in a renal ischemia-reperfusion injury mouse model. N(IL-23+IL-18) neutrophils directly and efficiently induced allogeneic T cell proliferation in vitro. N(IL-23+IL-18) neutrophils enhanced the syngeneic T cell response to allogeneic antigens in mixed-lymphocyte reaction assays. The adoptive transfer of the donor or host N(IL-23+IL-18) neutrophils significantly enhanced the antidonor antibody production in an allogeneic-skin-transplanted mouse model, accompanied by increased Tfh cells in the spleens. Therefore, the neutrophil subset induced by IL-23/IL-18 promotes tissue injury and antidonor humoral response in the allogeneic transplantation mouse model.

Expression and Immune Characterization of Major Histocompatibility Complex in Paralichthys olivaceus after Antigen Stimulation.

The Major histocompatibility complex (Mhc) is an important molecule for antigen presenting and binds to T cell receptors, activating T lymphocytes and triggering specific immune responses. To investigate the role of MhcII in adaptive immunity, in this study, mhcIIα and mhcIIβ of flounder (Paralichthys olivaceus) were cloned, polyclonal antibodies (Abs) against their extracellular regions were produced, respectively, and their distribution on cells and tissues and expression patterns, which varied by antigen stimulation or pathogen infection, were investigated. The results showed that the open reading frame (ORF) of mhcIIα is 708 bp, including 235 amino acids (aa); and the ORF of mhcIIβ is 741 bp, encoding 246aa. The mhcIIα and mhcIIβ were significantly expressed in gills, spleen, and peripheral blood leukocytes (PBLs). Their antibodies could specifically recognize eukaryotic expressed MhcIIα and MhcIIβ. MhcIIα+ and MhcIIβ+ cells were 30.2 ± 2.9% of the percentage in peripheral blood leukocytes. MhcII molecules were co-localized with CD83 and IgM on leukocytes, respectively, but not on CD4+ or CD8+ T lymphocyte subpopulations. The expression of both mhcIIα and mhcIIβ were significantly upregulated in flounder after bacteria and virus challenges. The percentages of MhcII+ cells, MhcII+/CD83+, and MhcII+/IgM+ double-positive cells increased significantly after PHA and ConA stimulation, respectively; they varied significantly in PBLs after polyI:C stimulation, and no variations were found after LPS treatment. In the meantime, variations in MhcII+ cells were consistent with that of CD4+ T lymphocytes. These results suggest that MhcII, mainly expressed in B cells and dendritic cells, play an essential role in antigen presentation, and respond significantly to exogenous antigens and T cell-dependent antigens. These results may provide an important reference for the study of cellular immunity in teleosts.

Pangenomic and immunoinformatics based analysis of Nipah virus revealed CD4+ and CD8+ T-Cell epitopes as potential vaccine candidates.

Introduction: Nipah (NiV) is the zoonotic deadly bat-borne virus that causes neurological and respiratory infections which ultimately lead to death. There are 706 infected cases reported up till now especially in Asia, out of which 409 patients died. There is no vaccine and effective treatment available for NiV infections and we have to timely design such strategies as world could not bear another pandemic situation. Methods: In this study, we screened viral proteins of NiV strains based on pangenomics analysis, antigenicity, molecular weight, and sub-cellular localization. The immunoproteomics based approach was used to predict T-cell epitopes of MHC class-I and II as potential vaccine candidates. These epitopes are capable to activate CD4+, CD8+, and T-cell dependent B-lymphocytes. Results: The two surface proteins including fusion glycoprotein (F) and attachment glycoprotein (G) are antigenic with molecular weights of 60kDa and 67kDa respectively. Three epitopes of F protein (VNYNSEGIA, PNFILVRNT, and IKMIPNVSN) were ranked and selected based on the binding affinity with MHC class-I, and 3 epitopes (VILNKRYYS, ILVRNTLIS, and VKLQETAEK) with MHC-II molecules. Similarly, for G protein, 3 epitopes each for MHC-I (GKYDKVMPY, ILKPKLISY, and KNKIWCISL) and MHC-II (LRNIEKGKY, FLIDRINWI, and FLLKNKIWC) with substantial binding energies were predicted. Based on the physicochemical properties, all these epitopes are non-toxic, hydrophilic, and stable. Conclusion: Our vaccinomics and system-level investigation could help to trigger the host immune system to prevent NiV infection.

IMMU-23. FRUCTOSE METABOLISM IN MICROGLIA PROMOTES GLIOBLASTOMA GROWTH

Abstract Glioblastoma (GBM) is the most common brain malignancy in adults and has a dismal prognosis. Advances in standard-of-care treatments for GBM have not kept pace with those for other malignancies, in part due to the inefficacy of immunotherapies in treating GBM. The tumor microenvironment (TME) of GBM is heavily populated with pro-tumorigenic tumor-associated macrophages (TAMs) and lacks robust infiltration of T cells. Given that the number of TAMs in the TME correlates with poor prognosis, understanding the mechanisms by which they thrive is essential for discovering new therapies. Bulk RNASeq data from mouse tumors indicates that the fructose transporter, SLC2A5, is highly expressed on TAMs relative to peripheral myeloid cells. Furthermore, human glioblastoma single cell RNASeq (scRNASeq) data indicates that SLC2A5 is expressed specifically on microglia, the tissue resident macrophage of the brain. To assess the necessity of SLC2A5 in microglia, we orthotopically implanted CT2A or QPP4 glioblastoma cells into wild-type mice and mice lacking SLC2A5 (SLC2A5 KO mice). We observed a significant increase in median survival in SLC2A5 KO mice compared to wild-type mice. This indicates a necessity of fructose metabolism in microglia to promote tumorigenesis. Upon ex vivo analysis of the immune compartment of the TME, we observed that microglial cells from tumors in SLC2A5 KO mice have higher expression of MHC-II and PDL1 molecules on the cell surface compared to those from wild-type mice. Additionally, the CD4:CD8 T cell ratio in tumors from SLC2A5 KO mice was lower than that in tumors from wild-type mice. These data suggest that fructose metabolism in microglia facilitates an immunosuppressive phenotype that promotes GBM progression.

Prevalently carried HLA allele associates with inflammation and poor prognosis in HF patients via co-stimulatory, adhesion and MHC-II enhanceosome regulation

Abstract Background Heart failure with reduced ejection fraction (HFrEF) is associated with impaired inflammation resolution, adverse remodeling, restricted function, and poor prognosis. Furthermore, immune cells play crucial roles in pathological remodeling in cardiovascular diseases. Thus identifying subsets of patients with unique inflammatory profiles may aid in better risk stratification and precision therapies for chronic HFrEF patients with altered immune profiles. Methods and Results A pilot study using scRNA-seq of circulating immune cells (n=16) showed strong T cell activation in HFrEF patients, which was validated via flow cytometry in HFrEF patients and healthy controls (n=180 patients) with a shift into the memory/effector phenotype (p&amp;lt;0.0001). Thus, HFrEF patients may have unique MHC signatures promoting aberrant T cell activation, leading to chronic inflammation and pathology. We investigated antigen-presenting cells (APCs) that activate CD4+ T cells via MHC-II and costimulatory molecules. Indeed, we found MHC-II and costimulatory molecule signatures associated with HFrEF and T cell activation, such as HLA-DRB5 (DRB5) and ICAM-1, indicating both T cell activation potential and a pro-inflammatory status. To study whether HLA-DRB5 selectively promotes immune dysregulation, circulating monocytes from healthy DRB5 carriers and non-carriers were investigated using scRNA-seq showing enhanced antigen presentation, co-stimulatory and inflammatory molecule expression (e.g. HLA-DRA, ICAM-2, JAK2). ScRNA-seq confirmed HLA-DRB5 regulation of MHC-II, inflammatory and adhesion (e.g. ITGAM and ITGB1) properties by silencing HLA-DRB5 in THP1 cells. In silico analysis of monocyte epigenome data predicted unique transcription factors (e.g. ERG) controlling of HLA-DRB5 via regulatory elements suggesting a role in selective MHC-II molecule activation. To gain insights as to whether HLA carrier status might associate with prognosis, we performed HLA sequencing on age and gender matched HFrEF patients (n=93). During follow up of this cohort we identified HLA-DRB5*0101, which belongs to the DR2-supertype, as a predictor for death (p&amp;lt;0.05). We hypothesized whether HLA-DRB5 expression could impact T cell infiltration into the heart. Thus, we stimulated naïve T cells with pre-treated THP1-derived DCs (stress v. no stress cardiac organoid medium) and found HLA-DRB5 silencing reduced the infiltration of T cells into unstressed cardiac organoids compared to control group. Conclusions This is the first study to provide mechanistic insights for how HLA-DRB5 regulates innate and adaptive immunity in the context of heart failure, while also showing corresponding changes in T cell activation, infiltration capacity and prognosis in HFrEF patients. These data provide novel insights for risk stratification of heart failure patients and novel immunological interventions which may improve prognosis in HFrEF patients.

Segmented filamentous bacteria-induced epithelial MHCII regulates cognate CD4+ IELs and epithelial turnover.

Intestinal epithelial cells have the capacity to upregulate MHCII molecules in response to certain epithelial-adhesive microbes, such as segmented filamentous bacteria (SFB). However, the mechanism regulating MHCII expression as well as the impact of epithelial MHCII-mediated antigen presentation on T cell responses targeting those microbes remains elusive. Here, we identify the cellular network that regulates MHCII expression on the intestinal epithelium in response to SFB. Since MHCII on the intestinal epithelium is dispensable for SFB-induced Th17 response, we explored other CD4+ T cell-based responses induced by SFB. We found that SFB drive the conversion of cognate CD4+ T cells to granzyme+ CD8α+ intraepithelial lymphocytes. These cells accumulate in small intestinal intraepithelial space in response to SFB. Yet, their accumulation is abrogated by the ablation of MHCII on the intestinal epithelium. Finally, we show that this mechanism is indispensable for the SFB-driven increase in the turnover of epithelial cells in the ileum. This study identifies a previously uncharacterized immune response to SFB, which is dependent on the epithelial MHCII function.

In Silico Analyses, Experimental Verification and Application in DNA Vaccines of Ebolavirus GP-Derived pan-MHC-II-Restricted Epitopes.

(1) Background and Purpose: Ebola virus (EBOV) is the causative agent of Ebola virus disease (EVD), which causes extremely high mortality and widespread epidemics. The only glycoprotein (GP) on the surface of EBOV particles is the key to mediating viral invasion into host cells. DNA vaccines for EBOV are in development, but their effectiveness is unclear. The lack of immune characteristics resides in antigenic MHC class II reactivity. (2) Methods: We selected MHC-II molecules from four human leukocyte antigen II (HLA-II) superfamilies with 98% population coverage and eight mouse H2-I alleles. IEDB, NetMHCIIpan, SYFPEITHI, and Rankpep were used to screen MHC-II-restricted epitopes with high affinity for EBOV GP. Further immunogenicity and conservation analyses were performed using VaxiJen and BLASTp, respectively. EpiDock was used to simulate molecular docking. Cluster analysis and binding affinity analysis of EBOV GP epitopes and selected MHC-II molecules were performed using data from NetMHCIIpan. The selective GP epitopes were verified by the enzyme-linked immunospot (ELISpot) assay using splenocytes of BALB/c (H2d), C3H, and C57 mice after DNA vaccine pVAX-GPEBO immunization. Subsequently, BALB/c mice were immunized with Protein-GPEBO, plasmid pVAX-GPEBO, and pVAX-LAMP/GPEBO, which encoded EBOV GP. The dominant epitopes of BALB/c (H-2-I-AdEd genotype) mice were verified by the enzyme-linked immunospot (ELISpot) assay. It is also used to evaluate and explore the advantages of pVAX-LAMP/GPEBO and the reasons behind them. (3) Results: Thirty-one HLA-II-restricted and 68 H2-I-restricted selective epitopes were confirmed to have high affinity, immunogenicity, and conservation. Nineteen selective epitopes have cross-species reactivity with good performance in MHC-II molecular docking. The ELISpot results showed that pVAX-GPEBO could induce a cellular immune response to the synthesized selective peptides. The better immunoprotection of the DNA vaccines pVAX-LAMP/GPEBO coincides with the enhancement of the MHC class II response. (4) Conclusions: Promising MHC-II-restricted candidate epitopes of EBOV GP were identified in humans and mice, which is of great significance for the development and evaluation of Ebola vaccines.

The β-Carboline Harmine Has a Protective Immunomodulatory Role in Nonhealing Cutaneous Leishmaniasis

Cutaneous leishmaniasis affects 1 million people worldwide annually. Although conventional treatments primarily target the parasite, there is growing interest in host immune modulation. In this study, we investigated the impact of synthetic β-carboline harmine (ACB1801), previously shown to be immunoregulatory in cancer, on the pathology caused by a drug-resistant Leishmania major strain causing persistent cutaneous lesions. Exposure to ACB1801 invitro had a modest impact on parasite burden within host macrophages. Moreover, it significantly increased major histocompatibility complex II and costimulatory molecule expression on infected dendritic cells, suggesting an enhanced immune response. Invivo, ACB1801 monotherapy led to a substantial reduction in lesion development and parasite burden in infected C57BL/6 mice, comparable with efficacy of amphotericin B. Transcriptomics analysis further supported ACB1801 immunomodulatory effects, revealing an enrichment of TNF-α, IFN-γ, and major histocompatibility complex II antigen presentation signatures in the draining lymph nodes of treated mice. Flow cytometry analysis confirmed an increased frequency (1.5×) of protective CD4+IFN-γ+TNF-α+ T cells and a decreased frequency (2×) in suppressive IL-10+FoxP3- T cells at the site of infection and in draining lymph nodes. In addition, ACB1801 downregulated the aryl hydrocarbon receptor signaling, known to enhance immunosuppressive cytokines. Thus, these results suggest a potential use for ACB1801 alone or in combination therapy for cutaneous leishmaniasis.

The CD4+ T cell repertoire specific for citrullinated peptides shows evidence of immune tolerance.

Rheumatoid arthritis occurs most often in people who express HLA-DR molecules containing a five aa "shared epitope" in the β chain. These MHCII molecules preferentially bind citrullinated peptides formed by posttranslational modification of arginine. Citrullinated peptide:HLA-DR complexes may act as arthritis-initiating neo-antigens for CD4+ T cells. Here, we used fluorophore-conjugated HLA-DR tetramers containing citrullinated peptides from human cartilage intermediate layer protein, fibrinogen, vimentin, or enolase 1 to track cognate CD4+ T cells. Immunization of HLA-DR transgenic mice with citrullinated peptides from vimentin or enolase 1 failed to cause any expansion of tetramer-binding cells, whereas immunization with citrullinated peptides from cartilage intermediate layer protein or fibrinogen elicited some expansion. The expanded tetramer-binding populations, however, had lower T helper 1 and higher regulatory T cell frequencies than populations elicited by viral peptides. These results indicate that HLA-DR-bound citrullinated peptides are not neo-antigens and induce varying degrees of immune tolerance that could pose a barrier to rheumatoid arthritis.

Novel engineered B lymphocytes targeting islet-specific T cells inhibit the development of type 1 diabetes in non-obese diabetic Scid mice.

In this study, we report a novel therapeutic approach using B lymphocytes to attract islet-specific T cells in the non-obese diabetic (NOD) mouse model and prevent the development of autoimmune diabetes. Rather than using the antibody receptor of B cells, this approach utilizes their properties as antigen-presenting cells to T cells. Purified splenic B cells were treated with lipopolysaccharide, which increases regulatory B (Breg) cell function, then electroporated with mRNA encoding either chimeric MHC-I or MHC-II molecules covalently linked to antigenic peptides. Immunoregulatory functions of these engineered B cells (e-B cells) were tested by in vitro assays and in vivo co-transfer experiments with beta-cell-antigen-specific CD8+ or CD4+ T cells in NOD.Scid mice, respectively. The e-B cells expressing chimeric MHC-I-peptide inhibited antigen-specific CD8+ T-cell cytotoxicity in vitro. The e-B cells expressing chimeric MHC-II-peptide induced antigen-specific CD4+ T cells to express the regulatory markers, PD-1, ICOS, CTLA-4, Lag3, and Nrp1. Furthermore, e-B cells encoding the chimeric MHC-I and MHC-II peptide constructs protected NOD.Scid mice from autoimmune diabetes induced by transfer of antigen-specific CD8+ and CD4+ T cells. MHC-peptide chimeric e-B cells interacted with pathogenic T cells, and protected the host from autoimmune diabetes, in a mouse model. Thus, we have successfully expressed MHC-peptide constructs in B cells that selectively targeted antigen-specific cells, raising the possibility that this strategy could be used to endow different protective cell types to specifically regulate/remove pathogenic cells.

BAP31 Knockout in Macrophages Affects CD4+T Cell Activation through Upregulation of MHC Class II Molecule.

The differentiation of CD4+T cells is a crucial component of the immune response. The spleen and thymus, as immune organs, are closely associated with the differentiation and development of T cells. Previous studies have suggested that BAP31 may play a role in modulating T cell activation, but the specific impact of BAP31 on T cells through macrophages remains uncertain. In this study, we present evidence that BAP31 macrophage conditional knockout (BAP31-MCKO) mice display an enlarged spleen and thymus, accompanied by activated clustering and disrupted differentiation of CD4+T cells. In vitro co-culture studies were conducted to investigate the impact of BAP31-MCKO on the activation and differentiation of CD4+T cells. The examination of costimulatory molecule expression in BMDMs and RAW 264.7 cells, based on the endoplasmic reticulum function of BAP31, revealed an increase in the expression of antigen presenting molecules, particularly MHC-II molecule, in the absence of BAP31 in BMDMs or RAW264.7 cells. These findings suggest that BAP31 plays a role in the activation and differentiation of CD4+T cells by regulating the MHC class II molecule on macrophages. These results provide further support for the importance of BAP31 in developing interaction between macrophages and CD4+T cells.

The effect of edible bird's nests on the expression of MHC-II and costimulatory molecules of C57BL/6 mouse splenocytes

The glutinous nest that builds by the saliva secretion of swiftlet is recognizable as an edible bird's nest (EBN). It enriched a medicinal value and was regarded as supplementary food that exerts various beneficial health effects, especially immune boosters. This study's objective was to determine the impact of EBN on the expression of MHC-II and costimulatory molecules (CD86 and CD80) related to the initiation of T-cell activation. Both rEBN and pEBN samples were prepared with simulated gastrointestinal digestion for enhancing the bioaccessibility of bioactive compounds. Our result showed that digested EBN samples slightly influence the upregulation of MHC-II, CD86, and CD80 in gene expression of LPS-stimulated Raw 264.7 cells. The concern of endotoxin contamination in EBN samples, which may cause a false-positive result, was measured by quantitative PCR. We found that the inflammatory genes (IL-1β and TNF-α) were not induced by EBN treatments. Moreover, cell surface protein expression in splenocytes treated with EBN was assessed using flow cytometric analysis. Digested EBN samples demonstrated their capacity to promote the elevation of MHC-II, CD86, and CD80 cell surface protein expression. Finally, the digested-EBN-treated splenocytes only exhibited a specific response in the T-cells population. Thus, EBN is a source of the bioactive compound that has been proposed to exert a role in the stimulation of both MHC-II and costimulatory molecules for TCR/pMHC-II interaction leading to T-cell activation.

Metabolic signature and proteasome activity controls synovial migration of CDC42hiCD14+ cells in rheumatoid arthritis.

Activation of Rho-GTPases in macrophages causes inflammation and severe arthritis in mice. In this study, we explore if Rho-GTPases define the joint destination of pathogenic leukocytes, the mechanism by which they perpetuate rheumatoid arthritis (RA), and how JAK inhibition mitigates these effects. CD14+ cells of 136 RA patients were characterized by RNA sequencing and cytokine measurement to identify biological processes and transcriptional regulators specific for CDC42 hiCD14+ cells, which were summarized in a metabolic signature (MetSig). The effect of hypoxia and IFN-γ signaling on the metabolic signature of CD14+ cells was assessed experimentally. To investigate its connection with joint inflammation, the signature was translated into the single-cell characteristics of CDC42 hi synovial tissue macrophages. The sensitivity of MetSig to the RA disease activity and the treatment effect were assessed experimentally and clinically. CDC42 hiCD14+ cells carried MetSig of genes functional in the oxidative phosphorylation and proteasome-dependent cell remodeling, which correlated with the cytokine-rich migratory phenotype and antigen-presenting capacity of these cells. Integration of CDC42 hiCD14+ and synovial macrophages marked with MetSig revealed the important role of the interferon-rich environment and immunoproteasome expression in the homeostasis of these pathogenic macrophages. The CDC42 hiCD14+ cells were targeted by JAK inhibitors and responded with the downregulation of immunoproteasome and MHC-II molecules, which disintegrated the immunological synapse, reduced cytokine production, and alleviated arthritis. This study shows that the CDC42-related MetSig identifies the antigen-presenting CD14+ cells that migrate to joints to coordinate autoimmunity. The accumulation of CDC42 hiCD14+ cells discloses patients perceptive to the JAKi treatment.