Cell-mediated Antigen Presentation Research Articles

Exploring computational approaches to design mRNA Vaccine against vaccinia and Mpox viruses.

Messenger RNA (mRNA) vaccines emerged as a powerful tool in the fight against infections. Unlike traditional vaccines, this unique type of vaccine elicits robust and persistent innate and humoral immune response with a unique host cell-mediated pathogen gene expression and antigen presentation. This offers a novel approach to combat poxviridae infections. From the genome of vaccinia and Mpox viruses, three key genes (E8L, E7R, and H3L) responsible for virus attachment and virulence were selected and employed for designing the candidate mRNA vaccine against vaccinia and Mpox viral infection. Various bioinformatics tools were employed to generate (B cell, CTL, and HTL) epitopes, of which 28 antigenic and immunogenic epitopes were selected and are linked to form the mRNA vaccine construct.Additional components, including a 5' cap, 5' UTR, adjuvant, 3' UTR, and poly(A) tail, were incorporated to enhance stability and effectiveness.Safety measures such as testing for human homology and in silico immune simulations were implemented to avoid autoimmunity and to mimics the immune response of human host to the designed mRNA vaccine, respectively. The mRNA vaccine's binding affinity was evaluated by docking it with TLR-2, TLR-3, TLR-4, and TLR-9 receptors which are subsequently followed by molecular dynamics simulations for the highest binding one to predict the stability of the binding complex. With a 73% population coverage, the mRNA vaccine looks promising, boasting a molecular weight of 198 kDa and a molecular formula of C8901H13609N2431O2611S48 and it is said to be antigenic, nontoxic and nonallergic, making it safe and effective in preventing infections with Mpox and vaccinia viruses, in comparison with other insilico-designed vaccine for vaccinia and Mpox viruses. However, further validation through in vivo and in vitro techniques is underway to fully assess its potential.

B cell-mediated antigen presentation promotes adverse cardiac remodeling in chronic heart failure.

Cardiovascular disease remains the leading cause of death worldwide. A primary driver of cardiovascular mortality is ischemic heart failure, a form of cardiac dysfunction that can develop in patients who survive myocardial infarction. Acute cardiac damage triggers robust changes in the spleen with rapid migration of immune cells from the spleen to the heart. Activating this "cardio-splenic" axis contributes to progressive cardiac dysfunction. The cardio-splenic axis has, therefore, been identified as a promising therapeutic target to prevent or treat heart failure. However, our understanding of the precise mechanisms by which specific immune cells contribute to adverse cardiac remodeling within the cardio-splenic axis remains limited. Here, we show that splenic B cells contribute to the development of heart failure via MHC II-mediated antigen presentation. We found that the adoptive transfer of splenic B cells from mice with ischemic heart failure promoted adverse cardiac remodeling and splenic inflammatory changes in naïve recipient mice. Based on single-cell RNA sequencing analysis of splenic B cells from mice with ischemic heart failure, we hypothesized that B cells contributed to adverse cardiac remodeling through antigen presentation by MHC II molecules. This mechanism was confirmed using transgenic mice with B cell-specific MHC II deletion, and by analyzing circulating B cells from humans who experienced myocardial infarction. Our results broaden our understanding of B lymphocyte biology, reshape current models of immune activation in response to myocardial injury, and point towards MHC II-mediated signaling in B cells as a novel and specific therapeutic target in chronic heart failure.

Immunomodulatory effects of Diospyros peregrina fruit preparation (DFP) in non-small cell lung cancer (NSCLC) by utilizing dendritic cell-mediated antigen presentation and T helper (TH) cell differentiation.

Diospyros peregrina is a dioecious plant which is native to India. It belongs to the family of Ebenaceae and is extensively used to treat various ailments, such as leucorrhoea and other uterine-related problems. Though few studies have been on D. peregrina for their anti-tumour response, little is known. Therefore, this intrigued us to understand its immunomodulator capabilities on various types of cancer extensively. Our primary focus is on NSCLC (Non-Small Cell Lung Cancer), which is ranked as the second largest form of cancer in the world, and the treatments demand non-invasive agents to target NSCLC effectively. In an objective to generate an efficient Lung Cancer Associated Antigen (LCA) specific anti-tumour immune response, LCA was presented using dendritic cells (DCs) in the presence of D. peregrina fruit preparation (DFP). Moreover, we also investigated DFP's role in the differentiation of T-helper (TH) cells. Therefore, this study aimed at better LCA presentation mediated by DFP by activating the LCA pulsed DCs and T helper cell differentiation for better immune response. DCs were pulsed with LCA for tumour antigen presentation in vitro, with and without DFP. Differentially pulsed DCs were irradiated to co-culture with autologous and allogeneic lymphocytes. Extracellular supernatants were collected for the estimation of cytokine levels by ELISA. LDH release assay was performed to test Cytotoxic T lymphocytes (CTLs) mediated lung tumour cell cytotoxicity. Thus, DFP may be a potential vaccine to generate anti-LCA immune responses to restrict NSCLC.

Proteolipid Protein-Induced Mouse Model of Multiple Sclerosis Requires B Cell-Mediated Antigen Presentation.

The pathogenic role B cells play in multiple sclerosis is underscored by the success of B cell depletion therapies. Yet, it remains unclear how B cells contribute to disease, although it is increasingly accepted that mechanisms beyond Ab production are involved. Better understanding of pathogenic interactions between B cells and autoreactive CD4 T cells will be critical for novel therapeutics. To focus the investigation on B cell:CD4 T cell interactions invivo and invitro, we previously developed a B cell-dependent, Ab-independent experimental autoimmune encephalomyelitis (EAE) mouse model driven by a peptide encompassing the extracellular domains of myelin proteolipid protein (PLPECD). In this study, we demonstrate that B cell depletion significantly inhibited PLPECD-induced EAE disease, blunted PLPECD-elicited delayed-type hypersensitivity reactions invivo, and reduced CD4 T cell activation, proliferation, and proinflammatory cytokine production. Further, PLPECD-reactive CD4 T cells sourced from B cell-depleted donor mice failed to transfer EAE to naive recipients. Importantly, we identified B cell-mediated Ag presentation as the critical mechanism explaining B cell dependence in PLPECD-induced EAE, where bone marrow chimeric mice harboring a B cell-restricted MHC class II deficiency failed to develop EAE. B cells were ultimately observed to restimulate significantly higher Ag-specific proliferation from PLP178-191-reactive CD4 T cells compared with dendritic cells when provided PLPECD peptide in head-to-head cultures. We therefore conclude that PLPECD-induced EAE features a required pathogenic B cell-mediated Ag presentation function, providing for investigable B cell:CD4 T cell interactions in the context of autoimmune demyelinating disease.

B cell-mediated antigen presentation is required to induce functional pathogenicity of CD4 T cells in a proteolipid protein mouse model of multiple sclerosis.

Abstract Given the success of B cell depletion therapy in multiple sclerosis (MS), deeper understanding of pathogenic B cells will be key in developing novel treatments. Notably, B cell depletion therapy leaves plasma cells and immunoglobulin levels largely intact, indicating that B cells provide pathogenic functions beyond antibodies. To better understand this, we recently developed a novel B cell-dependent, antibody-independent experimental autoimmune encephalomyelitis (EAE) mouse model of MS featuring immunoreactivity to the extracellular domains of myelin proteolipid protein (PLPECD). In contrast to a B cell-independent EAE model, we demonstrate here that PLPECD induced EAE in WT but not B cell-depleted mice, and that established disease was ameliorated by B cell depletion. We tested antigen presentation by B cells through mixed bone marrow chimeras and demonstrate that mice in which MHC II deficiency is restricted to B cells alone failed to exhibit EAE compared to MHC II sufficient mice. Given that HLA class II is the largest molecular link to MS incidence and CD4 T cells are causative in EAE, we tested B cells’ influence on CD4 T cells. In the absence of B cells, we observed not only lower activation and proliferation of CD4 T cells, but also noted a lower proinflammatory functional profile amongst the activated cells. Further, adoptively transferred CD4 T cells derived from B cell-depleted donors induced significantly less EAE compared to those from B cell-sufficient donors. These results demonstrate that antigen presentation by B cells plays a critical role in the activation, proliferation, function and pathogenicity of autoreactive CD4 T cells in demyelinating disease. Supported by grants from NIAID/NIH AI156123 and US Veterans Affairs I01BX003677.

B lymphocytes contribute to indirect pathway T cell sensitization via acquisition of extracellular vesicles.

B cells have been implicated in transplant rejection via antibody-mediated mechanisms and more recently by presenting donor antigens to T cells. We have shown in patients with chronic antibody-mediated rejection that B cells control the indirect T cell alloresponses. To understand more about the role of B cells as antigen-presenting cells for CD4+ T cell with indirect allospecificity, B cells were depleted in C57BL/6 mice, using an anti-CD20 antibody, prior to receiving MHC class I-mismatched (Kd ) skin. The absence of B cells at the time of transplantation prolonged skin graft survival. To study the mechanisms behind this observation, T cells with indirect allospecificity were transferred in mice receiving a Kd skin transplant. T cell proliferation was markedly inhibited in the absence of recipient B cells, suggesting that B cells contribute to indirect pathway sensitization. Furthermore, we have shown that a possible way in which B cells present alloantigens is via acquisition of MHC-peptide complexes. Finally, we demonstrate that the addition of B cell depletion to the transfer of regulatory T cells (Tregs) with indirect alloresponse further prolonged skin graft survival. This study supports an important role for B cells in indirect T cell priming and further emphasizes the advantage of combination therapies in prolonging transplant survival.

Identification of Hub Genes and Potential Molecular Mechanisms in Patients with HBV-Associated Acute Liver Failure.

Hepatitis B virus (HBV) infection is a major cause of acute liver failure (ALF) in China, and mortality rates are high among patients who do not receive a matched liver transplant. This study aimed to determine potential mechanisms involved in HBV-ALF pathogenesis. Gene expression profiles under access numbers GSE38941 and GSE14668 were downloaded from the Gene Expression Omnibus database, including cohorts of HBV-ALF liver tissue and normal samples. Differentially expressed genes (DEGs) with false discovery rates (FDR) <0.05 and |log2(fold change)| >1 as thresholds were screened using the Limma package. Gene modules associated with stable disease were mined using weighed gene co-expression network analysis (WGCNA). A co-expression network was constructed and DEGs were analyzed using gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. A gene-based network was constructed to explore major factors associated with disease progression. We identified 2238 overlapping DEGs as crucial gene cohorts in ALF development. Based on a WGCNA algorithm, 10 modules (modules 1-10) were obtained that ranged from 75 to 1078 genes per module. Cyclin-dependent kinase 1 (CDK1), cyclin B1 (CCNB1), and cell-division cycle protein 20 (CDC20) hub genes were screened using the co-expression network. Furthermore, 17 GO terms and 6 KEGG pathways were identified, such as cell division, immune response process, and antigen processing and presentation. Two overlapping signaling pathways that are crucial factors in HBV-ALF were screened using the Comprehensive Toxicogenomics Database (CTD). Several candidate genes including HLA-E, B2M, HLA-DPA1, and SYK were associated with HBV-ALF progression. Natural killer cell-mediated cytotoxicity and antigen presentation contributed to the progression of HBV-ALF. The HLA-E, B2M, HLA-DPA1, and SYK genes play critical roles in the pathogenesis and development of HBV-ALF.

B Cell-Mediated Antigen Presentation through MHC Class II Is Dispensable for Atherosclerosis Progression.

Depletion of B cells attenuates plaque development and modulates T cell responses in mouse models of atherosclerosis, suggesting that Ag presentation by B cells may promote disease progression. Thus, we set out to determine the role of B cell-mediated MHC class II (MHC II) Ag presentation during atherosclerotic plaque development. We developed murine conditional MHC II deletion and expression systems under control of the B cell-restricted CD19 promoter in an experimental model of atherosclerosis. Mice lacking MHC II expression only on B cells exhibited systemic shifts in germinal center and marginal zone B cell populations, leading to a reduced Ab response compared with littermate control animals. However, all populations were present and normal cholesterol uptake was detected in the plasma following high-fat diet treatment. In a second model, in which conditional expression of MHC II is limited only to B cells, showed similar overall cellularity characteristics compared with mice with complete MHC II deficiency. High-fat diet feeding showed no major changes in atherosclerotic plaque size or plaque cellular content in either conditional deletion or conditional expression approaches, compared with control animals. By testing the necessity and sufficiency of MHC II on B cells in the progression of atherosclerosis, we determine that MHC II on B cells does not directly regulate lesion development in murine models.

Present and Future of Immunotherapy in the Management of Multiple Myeloma.

Multiple myeloma (MM) is the second most common hematologic malignancy with an increasing incidence and prevalence. The wide array of effective antimyeloma agents have transformed MM into a chronic condition for some patients, requiring long-term management planning. Immunomodulatory drugs and proteasome inhibitors have played a pivotal role in defining the most effective regimens for both transplantation-eligible and transplantation-ineligible subgroups. Nevertheless, recent approvals of immunotherapies in MM such as daratumumab have added another important component to combination treatments for both relapsed or refractory and newly diagnosed disease. Evolving novel therapies such as chimeric antigen receptor T cells are poised to raise the bar even further, holding a promise of effective treatment option for patients who would otherwise have limited treatment alternatives. As we continue to therapeutically exploit the essential roles of cell-mediated immune surveillance, antigen presentation, and modulation of inhibitory surface signaling, we are rapidly establishing the cornerstone role of immunotherapies in the management of all phases of MM. In this review, we will cover the spectrum of available immunotherapies approved for clinical use in MM, as well as briefly describe those in early- and late-phase development, with the focus of raising the awareness of the expanding immuno-oncology armamentarium in MM.

Dissecting FcγR Regulation through a Multivalent Binding Model.

Many immune receptors transduce activation across the plasma membrane through their clustering. With Fcγ receptors (FcγRs), this clustering is driven by binding to antibodies of differing affinities that are in turn bound to multivalent antigen. As a consequence of this activation mechanism, accounting for and rationally manipulating immunoglobulin (Ig)G effector function is complicated by, among other factors, differing affinities between FcγR species and changes in the valency of antigen binding. In this study, we show that a model of multivalent receptor-ligand binding can effectively account for the contribution of IgG-FcγR affinity and immune complex valency. This model in turn enables us to make specific predictions about the effect of immune complexes of defined composition. In total, these results enable both rational immune complex design for a desired IgG effector function and the deconvolution of effector function by immune complexes.

Developing a screening platform for genetic and small molecule targets of cancer immunotherapy.

66 Background: The success of checkpoint blockade therapy is often dependent on CD8 T cell activation against tumor antigens. However, clinical benefit is only seen in a subset of patients, suggesting that there are other possibly targetable immunosuppressive pathways that are allowing the tumor to escape immune surveillance. Methods: A CD8 T cell that recognizes the EGFP200-208 peptide epitope allowed for the use of EGFP as a model tumor antigen while monitoring expression levels at the single cell resolution. Using a lymphoma line expressing EGFP or mCherry as our antigen-positive and -negative cancer models, we employed 3 screening strategies: 1) a forward genetics approach in which we selected for tumor cells that had naturally developed resistance to killing by CD8 T cells; 2) a reverse genetics approach that involved the use of pooled CRISPR libraries to identify knockout clones with a selection advantage or disadvantage when pressured by activated T cells; and 3) small molecule libraries, including FDA-approved drugs, to identify compounds that increased antigen-specific CD8 T cell killing. Results: Despite antigen recognition and early activation in response to the resistant tumor line, T cells failed to produce effector cytokines and underwent apoptosis in a PD-L1 and CTLA-4 independent manner. Candidate genes mediating this phenotype were derived from expression differences between the original susceptible tumor line and the immunoedited resistant tumor line. The pooled CRISPR approach was validated in a curated library by identifying genes with known roles in T cell-mediated killing and antigen presentation, such as Fas, B2m, and Tap1, as well as known suppressive molecules such as BTLA and PD-L1. LDL receptor expressed on the cancer cell emerged as a possible novel suppressor of T cells. Decitabine and 4-cinnolinethiol, among other small molecules, emerged as possible enhancers of CD8 T cell activity. Conclusions: We have identified several gene candidates as potentially novel and targetable checkpoint-like molecules, as well as small molecule compounds that may be able to enhance the anti-tumor activity of CD8 T cells. Efforts are ongoing in order to validate these targets and to screen larger libraries.

Role of Nuclear Factor (Erythroid-Derived 2)-Like 2 Signaling for Effects of Fumaric Acid Esters on Dendritic Cells.

To date, the intracellular signaling pathways involved in dendritic cell (DC) function are poorly understood. The antioxidative transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2) has been shown to affect maturation, function, and subsequent DC-mediated T cell responses of murine and human DCs. In experimental autoimmune encephalomyelitis (EAE), as prototype animal model for a T helper cell-mediated autoimmune disease, antigen presentation, cytokine production, and costimulation by DCs play a major role. We explore the role of Nrf2 in DC function, and DC-mediated T cell responses during T cell-mediated autoimmunity of the central nervous system using genetic ablation and pharmacological activation in mice and men to corroborate our data in a translational setting. In murine and human DCs, monomethyl fumarate induced Nrf2 signaling inhibits DC maturation and DC-mediated T cell proliferation by reducing inflammatory cytokine production and expression of costimulatory molecules. In contrast, Nrf2-deficient DCs generate more activated T helper cells (Th1/Th17) but fewer regulatory T cells and foster T cell proliferation. Transfer of DCs with Nrf2 activation during active EAE reduces disease severity and T cell infiltration. Our data demonstrate that Nrf2 signaling modulates autoimmunity in murine and human systems via inhibiting DC maturation and function thus shedding further light on the mechanism of action of antioxidative stress pathways in antigen-presenting cells.

Piperine, a Pungent Alkaloid from Black Pepper, Inhibits B Lymphocyte Activation and Effector Functions.

Piperine has several well-documented anti-inflammatory properties; however, little is known regarding its effect on humoral immunity. In this study, we describe the immunosuppressive effect of piperine on B lymphocytes, which are integral to the humoral immune response. Mouse B cells were cultured in the absence or presence of non-cytotoxic concentrations (25, 50, and 100μM) of piperine during T-dependent or T-independent stimulation. Piperine inhibited B cell proliferation by causing G0/G1 phase cell cycle arrest in association with reduced expression of cyclin D2 and D3. The inhibitory effect of piperine was not mediated through transient receptor potential vanilloid-1 ion channel (TRPV1) because piperine also inhibited the proliferation of B cells from TRPV1-deficient mice. Expression of class II major histocompatibility complex molecules and costimulatory CD40 and CD86 on B lymphocytes was reduced in the presence of piperine, as was B cell-mediated antigen presentation to syngeneic T cells. In addition, piperine inhibited B cell synthesis of interleukin (IL)-6 and IL-10 cytokines, as well as IgM, IgG2b, and IgG3 immunoglobulins. The inhibitory effect of piperine on B lymphocyte activation and effector function warrants further investigation for possible application in the treatment of pathologies related to inappropriate humoral immune responses. Copyright © 2017 John Wiley & Sons, Ltd.

Usage of Murine T-cell Hybridoma Cells as Responder Cells Reveals Interference of Helicobacter Pylori with Human Dendritic Cell-mediated Antigen Presentation.

Direct effects of Helicobacter pylori (H. pylori) on human CD4+ T-cells hamper disentangling a possible bacterial-mediated interference with major histocompatibility complex class II (MHC-II)-dependent antigen presentation to these cells. To overcome this limitation, we employed a previously described assay, which enables assessing human antigen-processing cell function by using murine T-cell hybridoma cells restricted by human leukocyte antigen (HLA) alleles. HLA-DR1+ monocyte-derived dendritic cells were exposed to H. pylori and pulsed with the antigen 85B from Mycobacterium tuberculosis (M. tuberculosis). Interleukin-2 (IL-2) secretion by AG85Baa97-112-specific hybridoma cells was then evaluated as an integral reporter of cognate antigen presentation. This methodology enabled revealing of interference of H. pylori with the antigen-presenting capacity of human dendritic cells.

Daclizumab reverses intrathecal immune cell abnormalities in multiple sclerosis.

ObjectiveNovel treatments such as natalizumab and fingolimod achieve their therapeutic efficacy in multiple sclerosis (MS) by blocking access of subsets of immune cells into the central nervous system, thus creating nonphysiological intrathecal immunity. In contrast, daclizumab, a humanized monoclonal antibody against the alpha chain of the IL-2 receptor, has a unique mechanism of action with multiple direct effects on innate immunity. As cellular intrathecal abnormalities corresponding to MS have been well defined, we asked how daclizumab therapy affects these immunological hallmarks of the MS disease process.MethodsNineteen subpopulations of immune cells were assessed in a blinded fashion in the blood and 50-fold concentrated cerebrospinal fluid (CSF) cell pellet in 32 patients with untreated relapsing-remitting MS (RRMS), 22 daclizumab-treated RRMS patients, and 11 healthy donors (HDs) using 12-color flow cytometry.ResultsLong-term daclizumab therapy normalized all immunophenotyping abnormalities differentiating untreated RRMS patients from HDs. Specifically, strong enrichment of adaptive immune cells (CD4+ and CD8+ T cells and B cells) in the CSF was reversed. Similarly, daclizumab controlled MS-related increases in the innate lymphoid cells (ILCs) and lymphoid tissue inducer cells in the blood and CSF, and reverted the diminished proportion of intrathecal monocytes. The only marker that distinguished daclizumab-treated MS patients from HDs was the expansion of immunoregulatory CD56bright NK cells.InterpretationNormalization of immunological abnormalities associated with MS by long-term daclizumab therapy suggests that this drug's effects on ILCs, NK cells, and dendritic cell-mediated antigen presentation to CD4+ and CD8+ T cells are critical in regulating the MS disease process.

Fc-gamma receptor polymorphisms as predictive and prognostic factors in patients receiving oncolytic adenovirus treatment

BackgroundOncolytic viruses have shown potential as cancer therapeutics, but not all patients seem to benefit from therapy. Polymorphisms in Fc gamma receptors (FcgRs) lead to altered binding affinity of IgG between the receptor allotypes and therefore contribute to differences in immune defense mechanisms. Associations have been identified between FcgR polymorphisms and responsiveness to different immunotherapies. Taken together with the increasing understanding that immunological factors might determine the efficacy of oncolytic virotherapy we studied whether FcgR polymorphisms would have prognostic and/or predictive significance in the context of oncolytic adenovirus treatments.Methods235 patients with advanced solid tumors were genotyped for two FcgR polymorphisms, FcgRIIa-H131R (rs1801274) and FcgRIIIa-V158F (rs396991), using TaqMan based qPCR. The genotypes were correlated with patient survival and tumor imaging data.ResultsIn patients treated with oncolytic adenoviruses, overall survival was significantly shorter if the patient had an FcgRIIIa-VV/ FcgRIIa-HR (VVHR) genotype combination (P = 0,032). In contrast, patients with FFHR and FFRR genotypes had significantly longer overall survival (P = 0,004 and P = 0,006, respectively) if they were treated with GM-CSF-armed adenovirus in comparison to other viruses. Treatment of these patients with unarmed virus correlated with shorter survival (P < 0,0005 and P = 0,016, respectively). Treating FFHH individuals with CD40L-armed virus resulted in longer survival than treatment with other viruses (P = 0,047).ConclusionsOur data are compatible with the hypothesis that individual differences in effector cell functions, such as NK cell-mediated antibody-dependent cellular cytotoxicity (ADCC) and tumor antigen presentation by APCs caused by polymorphisms in FcgRs could play role in the effectiveness of oncolytic virotherapies. If confirmed in larger populations, FcgR polymorphisms could have potential as prognostic and predictive biomarkers for oncolytic adenovirus therapies to enable better selection of patients for clinical trials. Also, putative associations between genotypes, different viruses and survival implicate potentially important mechanistic issues.

Effect ofLactobacillus brevisKB290 on the cell-mediated cytotoxic activity of mouse splenocytes: a DNA microarray analysis

Lactic acid bacteria confer a variety of health benefits. Here, we investigate the mechanisms by which Lactobacillus brevis KB290 (KB290) enhances cell-mediated cytotoxic activity. Female BALB/c mice aged 9 weeks were fed a diet containing KB290 (3 × 10(9) colony-forming units/g) or starch for 1 d. The resulting cytotoxic activity of splenocytes against YAC-1 cells was measured using flow cytometry and analysed for gene expression using DNA microarray technology. KB290 enhanced the cell-mediated cytotoxic activity of splenocytes. DNA microarray analysis identified 327 up-regulated and 347 down-regulated genes that characterised the KB290 diet group. The up-regulated genes were significantly enriched in Gene Ontology terms related to immunity, and, especially, a positive regulation of T-cell-mediated cytotoxicity existed among these terms. Almost all the genes included in the term encoded major histocompatibility complex (MHC) class I molecules involved in the presentation of antigen to CD8(+) cytotoxic T cells. Marco and Signr1 specific to marginal zone macrophages (MZM), antigen-presenting cells, were also up-regulated. Flow cytometric analysis confirmed that the proportion of MZM was significantly increased by KB290 ingestion. Additionally, the over-represented Kyoto Encyclopedia of Genes and Genomes pathways among the up-regulated genes were those for natural killer (NK) cell-mediated cytotoxicity and antigen processing and presentation. The results for the selected genes associated with NK cells and CD8(+) cytotoxic T cells were confirmed by quantitative RT-PCR. These results suggest that enhanced cytotoxic activity could be caused by the activation of NK cells and/or of CD8(+) cytotoxic T cells stimulated via MHC class I presentation.

Effect of IVIg on human dendritic cell-mediated antigen uptake and presentation: Role of lipid accumulation

Intravenous immunoglobulin (IVIg) is a therapeutic preparation consisting of pools of normal, polyspecific IgG antibodies obtained from plasma of several thousand healthy individuals. In addition to its use in primary and secondary immune deficiency, IVIg is increasingly used in the therapy of a large number of autoimmune conditions. Despite its successful use in immunopathologies for over two decades, the precise mechanisms underlying the therapeutic benefit have not been fully elucidated. We and others have demonstrated that IVIg inhibits the antigen uptake and presentation by dendritic cells (DC). Here we report that IVIg-mediated inhibition of uptake and processing of antigens is associated with an increased accumulation of lipid as analyzed by flow cytometry and electron microscopy. As accumulation of lipids in DC is known to impart tolerogenic properties, these findings unravel novel link between antibodies and intracellular physiology of innate cells and may further uncover novel immunoregulatory mechanisms of IVIg in auto-inflammatory diseases.

Immunisation with an allogeneic peptide promotes the induction of antigen-specific MHC IIpos CD4+ rat T cells demonstrating immunostimulatory properties

BackgroundThe phenomenon of T cell stimulation by MHC class II expressing (MHC IIpos) CD4+ T cells has been intensively investigated for T cell clones but, so far, not for native T cells. The extensive use of T cell clones may explain the inconsistent outcomes of T cell-mediated antigen-presentation. Therefore, we used freshly isolated primed rat CD4+ T cells induced by immunisation with an allogeneic peptide P1, which is involved in allograft rejection. MethodsMHC IIpos and MHC IIneg CD4+ T cells were isolated from popliteal lymph nodes of P1-immunised Lewis rats and were purified by combining depletion and positive selection steps. Purified MHC IIpos CD4+ T cells and MHC IIneg CD4+ T cells (105 cells per well each) were autostimulated or restimulated with P1-loaded (33μg/ml peptide P1) and subsequently irradiated (with 20Gy) autologous DC. ResultsSeven days after immunisation, a small population of MHC IIpos CD4+ T cells was detectable (approximately 8.0% of total lymph node cells), as well as a large population of MHC IIneg CD4+ T cells (up to 45%). Antigen-specific proliferation was observed for both T cell populations but only P1-loaded MHC IIpos CD4+ T cells presented antigen presenting cell (APC) function for P1-primed T cells. Their inability to activate unprimed T cells may be due to impaired surface expression of costimulatory molecules (CD80 and CD86). ConclusionImmunisation with the allogeneic peptide antigen P1 induced antigen-specific MHC IIpos CD4+ rat T cells demonstrating perfect APC function for primed T cells in vitro.

HIV-1N-Glycan Composition Governs a Balance between Dendritic Cell-Mediated Viral Transmission and Antigen Presentation

The natural function of dendritic cells (DCs) is to capture and degrade pathogens for Ag presentation. However, HIV-1 can evade viral degradation by DCs and hijack DCs for migration to susceptible CD4(+) T lymphocytes. It is unknown what factors decide whether a virus is degraded or transmitted to T cells. The interaction of DCs with HIV-1 involves C-type lectin receptors, such as DC-specific ICAM-3-grabbing nonintegrin, which bind to the envelope glycoprotein complex (Env), which is decorated heavily with N-linked glycans. We hypothesized that the saccharide composition of the Env N-glycans is involved in avoiding viral degradation and Ag presentation, as well as preserving infectious virus for the transmission to target cells. Therefore, we studied the fate of normally glycosylated virus versus oligomannose-enriched virus in DCs. Changing the heterogeneous N-linked glycan composition of Env to uniform oligomannose N-glycans increased the affinity of HIV-1 for DC-specific ICAM-3-grabbing nonintegrin and enhanced the capture of HIV-1 by immature DCs; however, it decreased the subsequent transmission to target cells. Oligomannose-enriched HIV-1 was directed more efficiently into the endocytic pathway, resulting in enhanced viral degradation and reduced virus transfer to target cells. Furthermore, Env containing exclusively oligomannose N-glycans was presented to Env-specific CD4(+) T cells more efficiently. Taken together, our results showed that the HIV-1 N-glycan composition plays a crucial role in the balance between DC-mediated Ag degradation and presentation and DC-mediated virus transmission to target cells. This finding may have implications for the early events in HIV-1 transmission and the induction of antiviral immune responses.