Macrophages as APC and the dendritic cell myth

Human cytomegalovirus-IE2 suppresses antigen presentation of macrophage through the IL10/STAT3 signalling pathway in transgenic mouse

Human cytomegalovirus (HCMV) has evolved sophisticated strategies to evade host immune defenses, enabling its persistent survival in human populations. HCMV intermediate-early protein 2 (IE2) has been identified as a crucial factor in immune evasion mechanisms. However, the specific immunomodulatory effects of IE2 on antigen presentation remain insufficiently explored. In this study, we established a transgenic mouse model to systematically examine the impact and molecular mechanisms of IE2 on macrophages (Mφs) antigen presentation in vivo. Our findings demonstrated that IE2 modifies Mφs' function by preventing their phagocytic activity and polarization. Additionally, IE2 inhibits Mφs overactivation both in vivo and in vitro, which raises IL-10 levels and activates the downstream mediator STAT3, which in turn decreases T cell immune responses by encouraging T helper 2 (Th2) type responses. In conclusion, these findings underscore the potential of IE2 as a critical regulator of immune evasion and may contribute to the development of novel, targeted therapeutic strategies against the virus.

Endocytic highways: Navigating macropinocytosis and other endocytic routes for precision drug delivery

Drug molecules can reach intracellular targets by different mechanisms, such as passive diffusion, active transport, and endocytosis. Endocytosis is the process by which cells engulf extracellular material by forming a vesicle and transporting it into the cells. In addition to its biological functions, endocytosis plays a vital role in the internalization of the therapeutic molecules. Clathrin-mediated endocytosis, caveolar endocytosis, and macropinocytosis are the most researched routes in the field of drug delivery. In addition to conventional small therapeutic molecules, the use of nanoformulations and large molecules, such as nucleic acids, peptides, and antibodies, have broadened the field of drug delivery. Although the majority of small therapeutic molecules can enter cells via passive diffusion, large molecules, and advanced targeted delivery systems, such as nanoparticles, are internalized by the endocytic route. Therefore, it is imperative to understand the characteristics of the endocytic routes in greater detail to design therapeutic molecules or formulations for successful delivery to the intracellular targets. This review highlights the prospects and limitations of the major endocytic routes for drug delivery, with a major emphasis on macropinocytosis. Since macropinocytosis is a non-selective uptake of extracellular matrix, the selective induction of macropinocytosis, using compounds that induce macropinocytosis and modulate macropinosome trafficking pathways, could be a potential approach for the intracellular delivery of diverse therapeutic modalities. Furthermore, we have summarized the characteristics associated with the formulations or drug carriers that can affect the endocytic routes for cellular internalization. The techniques that are used to study the intracellular uptake processes of therapeutic molecules are briefly discussed. Finally, the major limitations for intracellular targeting, endo-lysosomal degradation, and different approaches that have been used in overcoming these limitations, are highlighted in this review.

Interleukin-27-polarized HIV-resistant M2 macrophages are a novel subtype of macrophages that express distinct antiviral gene profiles in individual cells: implication for the antiviral effect via different mechanisms in the individual cell-dependent manner

Introduction

Interleukin (IL)-27 is an anti-viral cytokine. IL-27-treated monocyte-derived macrophages (27-Mac) suppressed HIV replication. Macrophages are generally divided into two subtypes, M1 and M2 macrophages. M2 macrophages can be polarized into M2a, M2b, M2c, and M2d by various stimuli. IL-6 and adenosine induce M2d macrophages. Since IL-27 is a member of the IL-6 family of cytokines, 27-Mac was considered M2d macrophages. In the current study, we compared biological function and gene expression profiles between 27-Mac and M2d subtypes.

Methods

Monocytes derived from health donors were differentiated to M2 using macrophage colony-stimulating factor. Then, the resulting M2 was polarized into different subtypes using IL-27, IL-6, or BAY60-658 (an adenosine analog). HIV replication was monitored using a p24 antigen capture assay, and the production of reactive oxygen species (ROS) was determined using a Hydrogen Peroxide Assay. Phagocytosis assay was run using GFP-labeled opsonized E. coli. Cytokine production was detected by the IsoPlexis system, and the gene expression profiles were analyzed using single-cell RNA sequencing (scRNA-seq).

Results and Discussion

27-Mac and BAY60-658-polarized M2d (BAY-M2d) resisted HIV infection, but IL-6-polarized M2d (6-M2d) lacked the anti-viral effect. Although phagocytosis activity was comparable among the three macrophages, only 27-Mac, but neither 6-M2d nor BAY-M2d, enhanced the generation of ROS. The cytokine-producing profile of 27-Mac did not resemble that of the two subtypes. The scRNA-seq revealed that 27-Mac exhibited a different clustering pattern compared to other M2ds, and each 27-Mac expressed a distinct combination of anti-viral genes. Furthermore, 27-Mac did not express the biomarkers of M2a, M2b, and M2c. However, it significantly expressed CD38 (p<0.01) and secreted CXCL9 (p<0.001), which are biomarkers of M1.

Conclusions

These data suggest that 27-Mac may be classified as either an M1-like subtype or a novel subset of M2, which resists HIV infection mediated by a different mechanism in individual cells using different anti-viral gene products. Our results provide a new insight into the function of IL-27 and macrophages.

The role of M1/M2 macrophage polarization in the pathogenesis of obesity-related kidney disease and related pathologies

Obesity is a rapidly growing health problem worldwide, affecting both adults and children and increasing the risk of chronic diseases such as type 2 diabetes, hypertension and cardiovascular disease (CVD). In addition, obesity is closely linked to chronic kidney disease (CKD) by either exacerbating diabetic complications or directly causing kidney damage. Obesity-related CKD is characterized by proteinuria, lipid accumulation, fibrosis and glomerulosclerosis, which can gradually impair kidney function. Among the immune cells of the innate and adaptive immune response involved in the pathogenesis of obesity-related diseases, macrophages play a crucial role in the inflammation associated with CKD. In obese individuals, macrophages enter a pro-inflammatory state known as M1 polarization, which contributes to chronic inflammation. This polarization promotes tissue damage, inflammation and fibrosis, leading to progressive loss of kidney function. In addition, macrophage-induced oxidative stress is a key feature of CKD as it also promotes cell damage and inflammation. Macrophages also contribute to insulin resistance in type 2 diabetes by releasing inflammatory molecules that impair glucose metabolism, complicating the management of diabetes in obese patients. Hypertension and atherosclerosis, which are often associated with obesity, also contribute to the progression of CKD via immune and inflammatory pathways. Macrophages influence blood pressure regulation and contribute to vascular inflammation, particularly via the renin-angiotensin system. In atherosclerosis, macrophages accumulate in arterial plaques, leading to chronic inflammation and plaque instability, which may increase the risk of CVD in CKD patients. This review focuses on the involvement of macrophages in CKD and highlights their role as a critical link between CKD and other pathologies. Targeting macrophage polarization and the ensuing macrophage-induced inflammation could be an effective therapeutic strategy for CKD and related diseases and improve outcomes for patients with obesity-related kidney disease.

Tumor β-Catenin Expression Associated With Poor Prognosis to Anti-PD-1 Antibody Monotherapy in Non-small Cell Lung Cancer

Background/Aim

Tumor intrinsic β-catenin signaling has been reported to influence the tumor immune microenvironment and may be a resistance mechanism to immune checkpoint inhibitors in various cancers.

Patients and Methods

We studied the association between tumor β-catenin expression and survival in 50 patients with non-small cell lung cancer (NSCLC) treated with anti-programmed death-1 antibody monotherapy. Tumor β-catenin expression was evaluated by immunohistochemistry.

Results

Patients with positive tumor β-catenin expression (20% of all patients) had worse progression-free survival and overall survival compared with those with negative tumor β-catenin expression. Patients with positive tumor β-catenin expression had reduced CD8+ cell and CD11c+ cell infiltration into tumor nests than those with negative tumor β-catenin expression. RT-PCR of tumor tissue revealed that patients with positive tumor β-catenin expression showed lower gene expression of CD8A, CD4, IFN-γ, BATF3, and CCL4. Knockdown of CTNNB1 tended to increase CCL4 expression, likely mediated by ATF3, in a lung cancer cell line with positive β-catenin expression.

Conclusion

NSCLC patients with positive tumor β-catenin expression that were treated with anti-programmed death-1 antibody monotherapy had poor prognosis.

Global trends and prospects related to macrophage in chronic kidney disease: a bibliometric analysis

BACKGROUND AND AIMS

Macrophages play a variety of widely concerned roles in the process of chronic kidney disease (CKD). To further understand the research hotspots and development trends regarding the relationship between macrophages and CKD, the role of macrophages in the occurrence and progression of CKD was summarized by bibliometrics in this study.

MATERIAL AND METHODS

We collected the studies relevant the role of macrophages in CKD from the Web of Science Core Collection, which included 1332 relevant studies from Jan 1st, 2004 to Jul 6th, 2023 in WoSCC. CiteSpace, biblioshiny in R, VOSviewer and SCImago Graphica Beta were used for bibliometric analysis and visualization.

RESULTS

Monash University from Australia is the most productive institution, while China and the USA are most productive countries. Anders HJ is the most cited author. In terms of the number of co-citations, the top one was "Macrophages: versatile players in renal inflammation and fibrosis" by Patrick Ming-Kuen Tang, published in Nature Reviews Nephrology in 2019. Important keywords of this research topic include inflammation, dendritic cell, oxidative stress, NF-κB, tgf-beta, interstitial fibrosis, glomerulonephritis, diabetic nephropathy. Future research hotspots may include molecular mechanism, acute kidney injury, macrophage polarization, kidney fibrosis.

CONCLUSION

This study provides a systematic review of the role of macrophages in CKD and speculates that future research hotspots. Previous studies have focused on the immune function of macrophages and atypia, and metabolic factors (especially iron metabolism within macrophages) have attracted the attention of researchers in recent years and are the forefront of recent research.

GPC3-targeted CAR-M cells exhibit potent antitumor activity against hepatocellular carcinoma

Chimeric antigen receptor (CAR)-modified macrophages are a promising treatment for solid tumor. So far the potential effects of CAR-M cell therapy have rarely been investigated in hepatocellular carcinoma (HCC). Glypican-3 (GPC3) is a biomarker for a variety of malignancies, including liver cancer, which is not expressed in most adult tissues. Thus, it is an ideal target for the treatment of HCC. In this study, we engineered mouse macrophage cells with CAR targeting GPC3 and explored its therapeutic potential in HCC. First, we generated a chimeric adenoviral vector (Ad5f35) delivering an anti-GPC3 CAR, Ad5f35-anti-GPC3-CAR, which using the CAR construct containing the scFv targeting GPC3 and CD3ζ intracellular domain. Phagocytosis and killing effect indicated that macrophages transduced with Ad5f35-anti-GPC3-CAR (GPC3 CAR-Ms) exhibited antigen-specific phagocytosis and tumor cell clearance in vitro, and GPC3 CAR-Ms showed significant tumor-killing effects and promoted expression of pro-inflammatory (M1) cytokines and chemokines. In 3D NACs-origami spheroid model of HCC, CAR-Ms were further demonstrated to have a significant tumor killing effect. Together, our study provides a new strategy for the treatment of HCC through CAR-M cells targeting GPC3, which provides a basis for the research and treatment of hepatocellular carcinoma.

IVT-mRNA reprogramming of myeloid cells for cancer immunotherapy

In the past decade, in vitro transcribed messenger RNAs (IVT-mRNAs) have emerged as promising therapeutic molecules. The clinical success of COVID-19 mRNA vaccines developed by Pfizer-BioNTech and Moderna, have demonstrated that IVT-mRNAs can be safely and successfully used in a clinical setting, and efforts are underway to develop IVT-mRNAs for therapeutic applications. Current applications of mRNA-based therapy have been focused on (1) mRNA vaccines for infectious diseases and cancer treatment; (2) protein replacement therapy; (3) gene editing therapy; and (4) cell-reprogramming therapies. Due to the recent clinical progress of cell-based immunotherapies, the last direction-the use of IVT-mRNAs as a therapeutic approach to program immune cells for the treatment of cancer has received extensive attention from the cancer immunotherapy field. Myeloid cells are important components of our immune system, and they play critical roles in mediating disease progression and regulating immunity against diseases. In this chapter, we discussed the progress of using IVT-mRNAs as a therapeutic approach to program myeloid cells against cancer and other immune-related diseases. Towards this direction, we first reviewed the pharmacology of IVT-mRNAs and the biology of myeloid cells as well as myeloid cell-targeting therapeutics. We then presented a few cases of current IVT-mRNA-based approaches to target and reprogram myeloid cells for disease treatment and discussed the advantages and limitations of these approaches. Finally, we presented our considerations in designing mRNA-based approaches to target myeloid cells for disease treatment.

Human milk oligosaccharides differentially support gut barrier integrity and enhance Th1 and Th17 cell effector responses in vitro

Human milk oligosaccharides (HMOs) can modulate the intestinal barrier and regulate immune cells to favor the maturation of the infant intestinal tract and immune system, but the precise functions of individual HMOs are unclear. To determine the structure-dependent effects of individual HMOs (representing different structural classes) on the intestinal epithelium as well as innate and adaptive immune cells, we assessed fucosylated (2'FL and 3FL), sialylated (3'SL and 6'SL) and neutral non-fucosylated (LNT and LNT2) HMOs for their ability to support intestinal barrier integrity, to stimulate the secretion of chemokines from intestinal epithelial cells, and to modulate cytokine release from LPS-activated dendritic cells (DCs), M1 macrophages (MØs), and co-cultures with naïve CD4+ T cells. The fucosylated and neutral non-fucosylated HMOs increased barrier integrity and protected the barrier following an inflammatory insult but exerted minimal immunomodulatory activity. The sialylated HMOs enhanced the secretion of CXCL10, CCL20 and CXCL8 from intestinal epithelial cells, promoted the secretion of several cytokines (including IL-10, IL-12p70 and IL-23) from LPS-activated DCs and M1 MØs, and increased the secretion of IFN-γ and IL-17A from CD4+ T cells primed by LPS-activated DCs and MØs while reducing the secretion of IL-13. Thus, 3'SL and 6'SL supported Th1 and Th17 responses while reducing Th2 responses. Collectively, our data show that HMOs exert structure-dependent effects on the intestinal epithelium and possess immunomodulatory properties that confer benefits to infants and possibly also later in life.

Septic macrophages induce T cells immunosuppression in a cell-cell contact manner with the involvement of CR3

BACKGROUND

In addition to excessive inflammation, immunosuppression has been recognized as a contributing factor to poor prognosis of sepsis. Although it has been reported that T cells can become functionally impaired during sepsis, the underlying mechanisms responsible for this phenomenon remain unclear. This study aims to elucidate the mechanisms by which macrophages induce immunosuppression in T cells.

METHODS

In an in vivo setting, C57BL-6J mice were subjected to cecal ligation and puncture (CLP) with or without depletion of macrophages, and the functions of T cells were assessed. In vitro experiments involved direct co-culture or separate culture of T cells and septic macrophages using a transwell system, followed by analysis of T cell immunity. Additionally, a siRNA targeting CD18 on macrophages was utilized to investigate the role of complement receptor 3 (CR3).

RESULTS

Both macrophages and T cells exhibited immunosuppression during sepsis. In the in vivo experiments, the absence of macrophages partially alleviated T cell immunosuppression, as evidenced by restored vitality, increased production of TNF-α and IFN-γ, elevated CD8+ T cell levels, and decreased CD25+ T cell levels. In the in vitro experiments, direct co-culture of T cells with septic macrophages resulted in diminished T cell immunity, which was improved when T cells and macrophages were separated by a chamber wall. The expression of CR3 (CD11b/CD18) was upregulated on septic macrophages, and silencing of CD18 led to decreased TNF-α production by T cells, reduced CD4+ T cell numbers, and increased CD25+ T cell numbers.

CONCLUSION

In sepsis, macrophages induce immunosuppression in T cells through direct cell-cell contact, with the involvement of CR3.

Defining the metabolic signatures associated with human macrophage polarisation

Macrophages are essential components of the innate immune system that play both homeostatic roles in healthy organs, and host defence functions against pathogens after tissue injury. To accomplish their physiological role, macrophages display different profiles of gene expression, immune function, and metabolic phenotypes that allow these cells to participate in different steps of the inflammatory reaction, from the initiation to the resolution phase. In addition, significant differences exist in the phenotype of macrophages depending on the tissue in which they are present and on the mammalian species. From a metabolic point of view, macrophages are essentially glycolytic cells; however, their metabolic fluxes are dependent on the functional polarisation of these cells. This metabolic and cellular plasticity offers the possibility to interfere with the activity of macrophages to avoid harmful effects due to persistent activation or the release of molecules that delay tissue recovery after injury.

Progress in PRRSV Infection and Adaptive Immune Response Mechanisms

Since its discovery, Porcine reproductive and respiratory syndrome (PRRS) has had a huge impact on the farming industry. The virus that causes PRRS is Porcine Reproductive and Respiratory Syndrome Virus (PRRSV), and because of its genetic diversity and the complexity of the immune response, the eradication of PRRS has been a challenge. To provide scientific references for PRRSV control and vaccine development, this study describes the processes of PRRSV-induced infection and escape, as well as the host adaptive immune response to PRRSV. It also discusses the relationship between PRRSV and the adaptive immune response.

Interaction between iron oxide nanoparticles (IONs) and primary human immune cells: An up-to-date review of the literature

Nanotechnology has been gaining more and more momentum lately and the potential use of nanomaterials such as nanoparticles (NPs) continues to grow in a variety of activity sectors. Among the NPs, iron oxide nanoparticles (IONs) have retained an increasing interest from the scientific community and industrials due to their superparamagnetic properties allowing their use in many fields, including medicine. However, some undesired effects of IONs and potential risk for human health are becoming increasingly reported in several studies. Although many in vivo studies reported that IONs induce immunotoxicity in different animal models, it is not clear how IONs can alter the biology of primary human immune cells. In this article, we will review the works that have been done regarding the interaction between IONs and primary immune cells. This review also outlines the importance of using primary immune cells in risk assessment of NPs as a reliable strategy for encouraging non-animal studies approaches, to determine risks that might affect the human immune system following different exposure scenarios. Taken all together, the reported observations help to get a more global picture on how IONs alter the human immune system especially the fact that inflammation, known to involve several immune cell types, is frequently reported as an undesired effect of IONs.

Vasculature in the mouse colon and spatial relationships with the enteric nervous system, glia, and immune cells

The distribution, morphology, and innervation of vasculature in different mouse colonic segments and layers, as well as spatial relationships of the vasculature with the enteric plexuses, glia, and macrophages are far from being complete. The vessels in the adult mouse colon were stained by the cardiovascular perfusion of wheat germ agglutinin (WGA)-Alexa Fluor 448 and by CD31 immunoreactivity. Nerve fibers, enteric glia, and macrophages were immunostained in the WGA-perfused colon. The blood vessels entered from the mesentery to the submucosa and branched into the capillary networks in the mucosa and muscularis externa. The capillary net formed anastomosed rings at the orifices of mucosa crypts, and the capillary rings surrounded the crypts individually in the proximal colon and more than two crypts in the distal colon. Microvessels in the muscularis externa with myenteric plexus were less dense than in the mucosa and formed loops. In the circular smooth muscle layer, microvessels were distributed in the proximal, but not the distal colon. Capillaries did not enter the enteric ganglia. There were no significant differences in microvascular volume per tissue volume between the proximal and distal colon either in the mucosa or muscularis externa containing the myenteric plexus. PGP9.5-, tyrosine hydroxylase-, and calcitonin gene-related peptide (CGRP)-immunoreactive nerve fibers were distributed along the vessels in the submucosa. In the mucosa, PGP9.5-, CGRP-, and vasoactive intestinal peptide (VIP)-immunoreactive nerves terminated close to the capillary rings, while cells and processes labeled by S100B and glial fibrillary acidic protein were distributed mainly in the lamina propria and lower portion of the mucosa. Dense Iba1 immunoreactive macrophages were closely adjacent to the mucosal capillary rings. There were a few macrophages, but no glia in apposition to microvessels in the submucosa and muscularis externa. In conclusion, in the mouse colon, (1) the differences in vasculature between the proximal and distal colon were associated with the morphology, but not the microvascular amount per tissue volume in the mucosa and muscle layers; (2) the colonic mucosa contained significantly more microvessels than the muscularis externa; and (3) there were more CGRP and VIP nerve fibers found close to microvessels in the mucosa and submucosa than in the muscle layers.

All-Trans Retinoic Acid Promotes M2 Macrophage Polarization in Vitro by Activating the p38MAPK/STAT6 Signaling Pathway

BACKGROUND

M2-type macrophages are inflammation-suppressing cells that are differentiated after induction by cytokines such as IL-4 or IL-13, which play an important regulatory role in inflammation and influence the regression of inflammation-related diseases. All-trans retinoic acid (ATRA) has an important role in suppressing immune-mediated inflammatory responses but the effect and underlying mechanism of ATRA on the polarization of M2 macrophages remains unclear.

METHODS

Macrophages were isolated from peritoneal wash fluid, and IL-4 (20 ng/mL) was used to construct a m2-type macrophage polarization model. The model was incubated with different concentrations of ATRA (15 µg/ml, 30 µg/ml, 45 µg/ml) for 24 h, and pretreated macrophages with p38MAPKα inhibitor SB202190 (20 μM). MTT, Trypan blue staining, Annexin V-PE/7-AAD staining, flow cytometry, real-time PCR and western blotting were used to investigate the effect and mechanism of ATRA on the polarization of M2 macrophages.

RESULTS

Compared with the IL-4 group, the proportion of F4/80⁺CD206⁺ M2-type macrophages was significantly higher in the ATRA group (P < 0.01). mRNA and protein expression levels of Arg-1, IL-10 and TGF-β1 were as significantly higher (P < 0.01) in the ATRA group as phosphorylation levels of STAT6 and p38MAPK (P < 0.01). After pretreatment with the addition of the inhibitor SB202190, M2-type macrophages proportion and their associated factors expression were significantly (P < 0.01) reduced, as compared with those in the ATRA group, but they were comparable (P > 0.05) with the IL-4 group.

CONCLUSION

The combination of ATRA and IL-4 activated the p38MAPK/STAT6-signaling pathway to promote polarization of M2 macrophages.

Thymoquinone Effect on Monocyte-Derived Macrophages, Cell-Surface Molecule Expression, and Phagocytosis

Macrophages are one of the most important cells in the immune system. They act as links between innate and adaptive immunities. In this study, the aim was to examine thymoquinone effects on the immunological properties of different macrophages. Peripheral blood mononuclear cells were isolated from blood from healthy volunteers by negative selection of monocytes that had been cultured for seven days to differentiate into macrophages. Cells were cultured with or without the presence of thymoquinone (TQ), which was used in two different concentrations (50 μg/mL and 100 μg/mL. Cluster of differentiation 80 (CD80), cluster of differentiation 86 (CD86), and human leukocyte antigen DR isotype (HLA-DR) were measured by flow cytometry, and the secretion of interferon gamma (IFN-γ) and tumour necrosis factor alpha (TNF-α) was measured. Cells were also tested for their E. coli phagocytosis abilities. The data showed that the expression of HLA-DR was significantly higher in cells treated with 100 μL/mL TQ. In addition, IFN-γ concentration increased in the 100 μg/mL TQ-treated cells. The macrophage phagocytosis results showed a significant difference in 50 μg/mL TQ-treated cells compared to the controls. TQ may enhance the immunological properties of macrophages during the early stages of innate immunity by activating phagocytosis ability and by increasing the expression of HLA-DR and the secretion of IFN-γ, which may enhance the antigen-presentation capabilities of macrophages.

Opportunities for Nitric Oxide in Potentiating Cancer Immunotherapy

Despite nearly 30 years of development and recent highlights of nitric oxide (NO) donors and NO delivery systems in anticancer therapy, the limited understanding of exogenous NO's effects on the immune system has prevented their advancement into clinical use. In particular, the effects of exogenously delivered NO differing from that of endogenous NO has obscured how the potential and functions of NO in anticancer therapy may be estimated and exploited despite the accumulating evidence of NO's cancer therapy-potentiating effects on the immune system. After introducing their fundamentals and characteristics, this review discusses the current mechanistic understanding of NO donors and delivery systems in modulating the immunogenicity of cancer cells as well as the differentiation and functions of innate and adaptive immune cells. Lastly, the potential for the complex modulatory effects of NO with the immune system to be leveraged for therapeutic applications is discussed in the context of recent advancements in the implementation of NO delivery systems for anticancer immunotherapy applications. SIGNIFICANCE STATEMENT: Despite a 30-year history and recent highlights of nitric oxide (NO) donors and delivery systems as anticancer therapeutics, their clinical translation has been limited. Increasing evidence of the complex interactions between NO and the immune system has revealed both the potential and hurdles in their clinical translation. This review summarizes the effects of exogenous NO on cancer and immune cells in vitro and elaborates these effects in the context of recent reports exploiting NO delivery systems in vivo in cancer therapy applications.

Single cell classification of macrophage subtypes by label-free cell signatures and machine learning

Pro-inflammatory (M1) and anti-inflammatory (M2) macrophage phenotypes play a fundamental role in the immune response. The interplay and consequently the classification between these two functional subtypes is significant for many therapeutic applications. Albeit, a fast classification of macrophage phenotypes is challenging. For instance, image-based classification systems need cell staining and coloration, which is usually time- and cost-consuming, such as multiple cell surface markers, transcription factors and cytokine profiles are needed. A simple alternative would be to identify such cell types by using single-cell, label-free and high throughput light scattering pattern analyses combined with a straightforward machine learning-based classification. Here, we compared different machine learning algorithms to classify distinct macrophage phenotypes based on their optical signature obtained from an ad hoc developed wide-angle static light scattering apparatus. As the main result, we were able to identify unpolarized macrophages from M1- and M2-polarized phenotypes and distinguished them from naive monocytes with an average accuracy above 85%. Therefore, we suggest that optical single-cell signatures within a lab-on-a-chip approach along with machine learning could be used as a fast, affordable, non-invasive macrophage phenotyping tool to supersede resource-intensive cell labelling.

Elucidating the Role of Innate and Adaptive Immune Responses in the Pathogenesis of Canine Chronic Inflammatory Enteropathy-A Search for Potential Biomarkers

Simple Summary

Canine chronic inflammatory enteropathy (CIE) is a chronic disease affecting the small or large intestine and, in some cases, the stomach of dogs. This gastrointestinal disorder is common and is characterized by recurrent vomiting, diarrhea, and weight loss in affected dogs. The pathogenesis of IBD is not completely understood. Similar to human IBD, potential disease factors include genetics, environmental exposures, and dysregulation of the microbiota and the immune response. Some important components of the innate and adaptive immune response involved in CIE pathogenesis have been described. However, the immunopathogenesis of the disease has not been fully elucidated. In this review, we summarized the literature associated with the different cell types and molecules involved in the immunopathogenesis of CIE, with the aim of advancing the search for biomarkers with possible diagnostic, prognostic, or therapeutic utility.

Abstract

Canine chronic inflammatory enteropathy (CIE) is one of the most common chronic gastrointestinal diseases affecting dogs worldwide. Genetic and environmental factors, as well as intestinal microbiota and dysregulated host immune responses, participate in this multifactorial disease. Despite advances explaining the immunological and molecular mechanisms involved in CIE development, the exact pathogenesis is still unknown. This review compiles the latest reports and advances that describe the main molecular and cellular mechanisms of both the innate and adaptive immune responses involved in canine CIE pathogenesis. Future studies should focus research on the characterization of the immunopathogenesis of canine CIE in order to advance the establishment of biomarkers and molecular targets of diagnostic, prognostic, or therapeutic utility.

Inhibition of glioma development by doxorubicin-photochemical internalization generated macrophage vaccine: a survival study in rats

BACKGROUND

The process known as immunogenic cell death (ICD) is characterized by dead and dying cancer cells exposing and releasing so-called damage associated molecular patterns (DAMPs). ICD has been shown to enhance the efficacy of antigen presenting cell (APC) immunotherapy. Both anthracycline drugs such as doxorubicin (DOX), and photodynamic therapy (PDT) have been shown to be inducers of ICD. It was therefore hypothesized that combined PDT and DOX i.e. photochemical internalization of DOX (DOX-PCI) would increase ICD compared to DOX acting as a single agent.

MATERIALS AND METHODS

F98 glioma cells were treated with DOX-PCI in vitro and the ICD markers HMGB1, HSP70, and HSP90 were determined by ELISA assay. Peritoneal macrophages (Ma), obtained from Fisher rats acting as APCs, were co-incubated with dead F98 glioma cells killed via DOX or DOX-PCI treatment ex vivo. The pulsed Ma (Ma ^DOX or Ma ^DOX-PCI) were used to inoculate the animals either before (preventive) or after (curative) intra-cranially implantation of the glioma cells.

RESULTS

F98 cells, treated with DOX-PCI in vitro, induced a significantly higher level of HGMB1, HSP70, and HSP90 than DOX acting alone. Ma ^DOX-PCI inoculated animals, in both preventive and curative protocols, had a pronounced survival benefit compared to either the non-treatment or Ma^DOX control groups. In the curative protocol, a second booster inoculation significantly improved survival, with 60% of the animals alive at day 60.

CONCLUSION

Macrophages primed with DOX-PCI treated glioma cells appeared to be highly effective as APCs and, when injected into host animals, could delay and, in some cases, prevent tumor development.

Epigenetic and transcriptional regulation of innate immunity in cancer

Innate immune cells participate in the detection of tumor cells via complex signaling pathways mediated by pattern-recognition receptors, such as Toll-like receptors (TLR) and NOD-like receptors (NLR). These pathways are finely tuned via multiple mechanisms, including epigenetic regulation. It is well established that hematopoietic progenitors generate innate immune cells that can regulate cancer cell behavior, and the disruption of normal hematopoiesis in pathologic states may lead to altered immunity and the development of cancer. In this review, we discuss the epigenetic and transcriptional mechanisms that underlie the initiation and amplification of innate immune signaling in cancer. We also discuss new targeting possibilities for cancer control that exploit innate immune cells and signaling molecules, potentially heralding the next generation of immunotherapy.

Interferon regulatory factor-5-dependent CD11c+ macrophages contribute to the formation of rupture-prone atherosclerotic plaques

AIMS

Inflammation is a key factor in atherosclerosis. The transcription factor interferon regulatory factor-5 (IRF5) drives macrophages towards a pro-inflammatory state. We investigated the role of IRF5 in human atherosclerosis and plaque stability.

METHODS AND RESULTS

Bulk RNA sequencing from the Carotid Plaque Imaging Project biobank were used to mine associations between major macrophage associated genes and transcription factors and human symptomatic carotid disease. Immunohistochemistry, proximity extension assays, and Helios cytometry by time of flight (CyTOF) were used for validation. The effect of IRF5 deficiency on carotid plaque phenotype and rupture in ApoE-/- mice was studied in an inducible model of plaque rupture. Interferon regulatory factor-5 and ITGAX/CD11c were identified as the macrophage associated genes with the strongest associations with symptomatic carotid disease. Expression of IRF5 and ITGAX/CD11c correlated with the vulnerability index, pro-inflammatory plaque cytokine levels, necrotic core area, and with each other. Macrophages were the predominant CD11c-expressing immune cells in the plaque by CyTOF and immunohistochemistry. Interferon regulatory factor-5 immunopositive areas were predominantly found within CD11c+ areas with a predilection for the shoulder region, the area of the human plaque most prone to rupture. Accordingly, an inducible plaque rupture model of ApoE-/-Irf5-/- mice had significantly lower frequencies of carotid plaque ruptures, smaller necrotic cores, and less CD11c+ macrophages than their IRF5-competent counterparts.

CONCLUSION

Using complementary evidence from data from human carotid endarterectomies and a murine model of inducible rupture of carotid artery plaque in IRF5-deficient mice, we demonstrate a mechanistic link between the pro-inflammatory transcription factor IRF5, macrophage phenotype, plaque inflammation, and its vulnerability to rupture.

Targeting Bcl6 in the TREX1 D18N murine model ameliorates autoimmunity by modulating T follicular helper cells and Germinal center B cells

The Three Prime Repair EXonuclease I (TREX1) is critical for degrading post‐apoptosis DNA. Mice expressing catalytically inactive TREX1 (TREX1 D18N) develop lupus‐like autoimmunity due to chronic sensing of undegraded TREX1 DNA substrates, production of the inflammatory cytokines, and the inappropriate activation of innate and adaptive immunity. This study aimed to investigate Thelper (Th) dysregulation in the TREX1 D18N model system as a potential mechanism for lupus‐like autoimmunity. Comparison of immune cells in secondary lymphoid organs, spleen and peripheral lymph nodes (LNs) between TREX1 D18N mice and the TREX1 null mice revealed that the TREX1 D18N mice exhibit a Th1 bias. Additionally, the T‐follicular helper cells (Tfh) and the germinal celter (GC) B cells were also elevated in the TREX1 D18N mice. Targeting Bcl6, a lineage‐defining transcription factor for Tfh and GC B cells, with a commercially available Bcl6 inhibitor, FX1, attenuated Tfh, GC, and Th1 responses, and rescued TREX1 D18N mice from autoimmunity. The study presents Tfh and GC B‐cell responses as potential targets in autoimmunity and that Bcl6 inhibitors may offer therapeutic approach in TREX1‐associated or other lupus‐like diseases.

Perspectives Concerning Various Symptoms of SARS-CoV-2 Detected Individuals

After exposure to SARS-CoV-2, varying symptoms of COVID-19 ranging from asymptomatic symptoms to morbidity and mortality have been exhibited in each individual. SARS-CoV-2 requires various cellular molecules for penetration into a target host cell. Angiotensin-converting enzyme2 (ACE2) acts as the viral receptor molecule. After attachment, SARS-CoV-2 also requires the transmembrane protease serine-2 (TMPRSS-2) and furin molecules, which serve as co-receptors for penetration into the target cell and for subsequent replication. In the meantime, a major histocompatibility complex (MHC) is required for the induction of adaptive immune cells, especially cytotoxic T cells and helper T cells, to clear the virally infected cells. This perspective review article proposes different aspects to explain the varying symptoms of the individuals who have been exposed to SARS-CoV-2, which relates to the polymorphisms of these involved molecules.

Targeting macrophage-mediated tumor cell phagocytosis: An overview of phagocytosis checkpoints blockade, nanomedicine intervention, and engineered CAR-macrophage therapy

Immunotherapy has been developing at an unprecedented speed with promising therapeutic outcomes in the wide spectrum of cancers. Up until now, most immunotherapies have focused on adaptive immunity; however, investigating the potential of macrophage phagocytosis and consequent adaptive immune cross-priming has led to a growing interest in exploiting macrophages in cancer therapy. In light of the positive evidence from preclinical studies and early clinical data, targeting macrophage phagocytosis has become a promising therapeutic strategy. Here, we review therapies based on harnessing and amplifying macrophage phagocytosis, such as blocking phagocytosis checkpoints and exploiting nanoparticles as efficient approaches in elevating macrophages-mediated phagocytosis. The present study introduces CAR-macrophage as the state-of-the-art modality serving as the bridge between the innate and adaptive immune system to mount a superior anti-tumor response in the treatment of cancer. We also take a look at the recent reports of therapies based on CAR-engineered macrophages with the hope of providing a future research direction for expanding the application of CAR-macrophage therapy.

Engineered CAR-Macrophages as Adoptive Immunotherapies for Solid Tumors

Cellular immunotherapies represent a promising approach for the treatment of cancer. Engineered adoptive cell therapies redirect and augment a leukocyte’s inherent ability to mount an immune response by introducing novel anti-tumor capabilities and targeting moieties. A prominent example of this approach is the use of T cells engineered to express chimeric antigen receptors (CARs), which have demonstrated significant efficacy against some hematologic malignancies. Despite increasingly sophisticated strategies to harness immune cell function, efficacy against solid tumors has remained elusive for adoptive cell therapies. Amongst cell types used in immunotherapies, however, macrophages have recently emerged as prominent candidates for the treatment of solid tumors. In this review, we discuss the use of monocytes and macrophages as adoptive cell therapies. Macrophages are innate immune cells that are intrinsically equipped with broad therapeutic effector functions, including active trafficking to tumor sites, direct tumor phagocytosis, activation of the tumor microenvironment and professional antigen presentation. We focus on engineering strategies for manipulating macrophages, with a specific focus on CAR macrophages (CAR-M). We highlight CAR design for macrophages, the production of CAR-M for adoptive cell transfer, and clinical considerations for their use in treating solid malignancies. We then outline recent progress and results in applying CAR-M as immunotherapies. The recent development of engineered macrophage-based therapies holds promise as a key weapon in the immune cell therapy armamentarium.

Immune Tolerance in the Oral Mucosa

The oral mucosa is a site of intense immune activity, where a large variety of immune cells meet to provide a first line of defense against pathogenic organisms. Interestingly, the oral mucosa is exposed to a plethora of antigens from food and commensal bacteria that must be tolerated. The mechanisms that enable this tolerance are not yet fully defined. Many works have focused on active immune mechanisms involving dendritic and regulatory T cells. However, epithelial cells also make a major contribution to tolerance by influencing both innate and adaptive immunity. Therefore, the tolerogenic mechanisms concurring in the oral mucosa are intertwined. Here, we review them systematically, paying special attention to the role of oral epithelial cells.

Effects of synthetic silymarin-PLGA nanoparticles on M2 polarization and inflammatory cytokines in LPS-treated murine peritoneal macrophages

OBJECTIVES

Silymarin (SM) is a natural antioxidant compound with good anti-inflammatory effects, but its poor water solubility restricts its usage. Today, nanomaterial compounds (such as PLGA Poly D, L-lactic-co-glycolic acid) can provide a proper drug delivery system and help improve the accessibility of bioactive compounds to cells and tissues.

MATERIALS AND METHODS

In this study, PLGA nanoparticles (NPs) containing SM (SM-PLGA) were synthesized and characterized and their biological effects were evaluated on M2 macrophage polarization to regulate inflammation. SM-PLGA NPs were fabricated by the oil in water emulsion (O/W) method. Macrophages (MQs) were isolated from mouse peritoneum by the cold RPMI lavage protocol. Primary mouse MQ cells were treated by SM and SM-PLGA NPs and then stimulated with lipopolysaccharide (LPS). M2 polarization was evaluated by measurements of cytokine secretion levels (TNF-α, IL1-β, and IL-10), flow cytometry markers (F4/80, CD11b, CD38, and CD206), and the expression of specific proteins (M2 Ym1 and Fizz1).

RESULTS

SM-PLGA characterization showed that NPs were fabricated in the desired form. SM and SM-PLGA decreased pro-inflammatory cytokines (TNF-α and IL1-β) and increased IL10 as an anti-inflammatory cytokine. On the other hand, the M2-associated markers and proteins increased following treatment with SM and SM-PLGA. Post-hoc analysis indicated that these changes were more pronounced in the SM-PLGA group.

CONCLUSION

This study revealed that SM-PLGA could markedly promote M2 polarization, thereby providing a valuable medical approach against sepsis and septic shock.

Electrical Detection of Innate Immune Cells

Accurately classifying the innate immune players is essential to comprehensively and quantitatively evaluate the interactions between the innate and the adaptive immune systems. In addition, accurate classification enables the development of models to predict behavior and to improve prospects for therapeutic manipulation of inflammatory diseases and cancer. Rapid development in technologies that provide an accurate definition of the type of cell in action, allows the field of innate immunity to the lead in therapy developments. This article presents a novel immunophenotyping technique using electrical characterization to differentiate between the two most important cell types of the innate immune system: dendritic cells (DCs) and macrophages (MACs). The electrical characterization is based on capacitance measurements, which is a reliable marker for cell surface area and hence cell size. We differentiated THP-1 cells into DCs and MACs in vitro and conducted electrical measurements on the three cell types. The results showed average capacitance readings of 0.83 µF, 0.93 µF, and 1.01 µF for THP-1, DCs, and MACs, respectively. This corresponds to increasing cell size since capacitance is directly proportional to area. The results were verified with image processing. Image processing was used for verification because unlike conventional techniques, especially flow cytometry, it avoids cross referencing and by-passes the limitation of a lack of specificity of markers used to detect the different cell types.

Different Aspects Concerning Viral Infection and the Role of MHC Molecules in Viral Prevention

Major Histocompatibility Complex (MHC) molecules play a crucial role in inducing an adaptive immune response. T-cell epitopes require compatible MHC molecules to form MHC-peptide Complexes (pMHC) that activate the T-cell Receptors (TCR) of T-lymphocyte clones. MHCs are polymorphic molecules with wide varieties of gene alleles. There are two classes of MHC molecules, class I and II. Both classes have three classical loci HLA-A, -B, and –C are present in class I and HLA-DP, -DQ, and -DR in class II. To induce a compatible T-lymphocyte clone, the T-cell epitope requires the association of the compatible MHC molecule to form pMHC. Each MHC variant possesses a different groove that is capable of binding a different range of antigenic epitopes. Without the compatible MHC molecule, a T cell clone cannot be activated by a particular viral epitope. With the aim of preventing viral transmission, the efficiency of a viral vaccine is related to the existence of specific MHC alleles in the individual. This article proposes the roles of the MHC molecule to prevent viral infection. In addition, the association of the viral receptor molecule with the viral infection will also be discussed.

Dendritic cells maintain anti-tumor immunity by positioning CD8 skin-resident memory T cells

Tissue-resident memory (T_RM) T cells are emerging as critical components of the immune response to cancer; yet, requirements for their ongoing function and maintenance remain unclear. APCs promote T_RM cell differentiation and re-activation but have not been implicated in sustaining T_RM cell responses. Here, we identified a novel role for dendritic cells in supporting T_RM to melanoma. We showed that CD8 T_RM cells remain in close proximity to dendritic cells in the skin. Depletion of CD11c⁺ cells results in rapid disaggregation and eventual loss of melanoma-specific T_RM cells. In addition, we determined that T_RM migration and/or persistence requires chemotaxis and adhesion mediated by the CXCR6/CXCL16 axis. The interaction between CXCR6-expressing T_RM cells and CXCL16-expressing APCs was found to be critical for sustaining T_RM cell-mediated tumor protection. These findings substantially expand our knowledge of APC functions in T_RM T-cell homeostasis and longevity.

The impact of influenza pulmonary infection and inflammation on vagal bronchopulmonary sensory neurons

Influenza A virus (IAV) is rapidly detected in the airways by the immune system, with resident parenchymal cells and leukocytes orchestrating viral sensing and the induction of antiviral inflammatory responses. The airways are innervated by heterogeneous populations of vagal sensory neurons which also play an important role in pulmonary defense. How these neurons respond to IAV respiratory infection remains unclear. Here, we use a murine model to provide the first evidence that vagal sensory neurons undergo significant transcriptional changes following a respiratory IAV infection. RNA sequencing on vagal sensory ganglia showed that IAV infection induced the expression of many genes associated with an antiviral and pro-inflammatory response and this was accompanied by a significant increase in inflammatory cell recruitment into the vagal ganglia. Assessment of gene expression in single-vagal sensory neurons confirmed that IAV infection induced a neuronal inflammatory phenotype, which was most prominent in bronchopulmonary neurons, and also evident in some neurons innervating other organs. The altered transcriptome could be mimicked by intranasal treatment with cytokines and the lung homogenates of infected mice, in the absence of infectious virus. These data argue that IAV pulmonary infection and subsequent inflammation induces vagal sensory ganglia neuroinflammation and this may have important implications for IAV-induced morbidity.

Role of Macrophages and Related Cytokines in Kidney Disease

Inflammation is a key characteristic of kidney disease, but this immune response is two-faced. In the acute phase of kidney injury, there is an activation of the immune cells to fight against the insult, contributing to kidney repair and regeneration. However, in chronic kidney diseases (CKD), immune cells that infiltrate the kidney play a deleterious role, actively participating in disease progression, and contributing to nephron loss and fibrosis. Importantly, CKD is a chronic inflammatory disease. In early CKD stages, patients present sub-clinical inflammation, activation of immune circulating cells and therefore, anti-inflammatory strategies have been proposed as a common therapeutic target for renal diseases. Recent studies have highlighted the plasticity of immune cells and the complexity of their functions. Among immune cells, monocytes/macrophages play an important role in all steps of kidney injury. However, the phenotype characterization between human and mice immune cells showed different markers; therefore the extrapolation of experimental studies in mice could not reflect human renal diseases. Here we will review the current information about the characteristics of different macrophage phenotypes, mainly focused on macrophage-related cytokines, with special attention to the chemokine CCL18, and its murine functional homolog CCL8, and the macrophage marker CD163, and their role in kidney pathology.

Radiation and adjuvant drug-loaded liposomes target glioblastoma stem cells and trigger in-situ immune response

Background

The radio- and chemo-resistance of glioblastoma stem-like cells (GSCs), together with their innate tumor-initiating aptitude, make this cell population a crucial target for effective therapies. However, targeting GSCs is hardly difficult and complex, due to the presence of the blood-brain barrier (BBB) and the infiltrative nature of GSCs arousing their dispersion within the brain parenchyma.

Methods

Liposomes (LIPs), surface-decorated with an Apolipoprotein E-modified peptide (mApoE) to enable BBB crossing, were loaded with doxorubicin (DOXO), as paradigm of cytotoxic drug triggering immunogenic cell death (ICD). Patient-derived xenografts (PDXs) obtained by GSC intracranial injection were treated with mApoE-DOXO-LIPs alone or concomitantly with radiation.

Results

Our results indicated that mApoE, through the engagement of the low-density lipoprotein receptor (LDLR), promotes mApoE-DOXO-LIPs transcytosis across the BBB and confers target specificity towards GSCs. Irradiation enhanced LDLR expression on both BBB and GSCs, thus further promoting LIP diffusion and specificity. When administered in combination with radiations, mApoE-DOXO-LIPs caused a significant reduction of in vivo tumor growth due to GSC apoptosis. GSC apoptosis prompted microglia/macrophage phagocytic activity, together with the activation of the antigen-presenting machinery crucially required for anti-tumor adaptive immune response.

Conclusions

Our results advocate for radiotherapy and adjuvant administration of drug-loaded, mApoE-targeted nanovectors as an effective strategy to deliver cytotoxic molecules to GSCs at the surgical tumor margins, the forefront of glioblastoma (GBM) recurrence, circumventing BBB hurdles. DOXO encapsulation proved in situ immune response activation within GBM microenvironment.

The Mononuclear Phagocyte System of the Rat

The laboratory rat continues to be the model of choice for many studies of physiology, behavior, and complex human diseases. Cells of the mononuclear phagocyte system (MPS; monocytes, macrophages, and dendritic cells) are abundant residents in every tissue in the body and regulate postnatal development, homeostasis, and innate and acquired immunity. Recruitment and proliferation of MPS cells is an essential component of both initiation and resolution of inflammation. The large majority of current knowledge of MPS biology is derived from studies of inbred mice, but advances in technology and resources have eliminated many of the advantages of the mouse as a model. In this article, we review the tools available and the current state of knowledge of development, homeostasis, regulation, and diversity within the MPS of the rat.

Interferon-gamma-activated macrophages infected with Burkholderia cenocepacia process and present bacterial antigens to T-cells by class I and II major histocompatibility complex molecules

Burkholderia cenocepacia is an emerging opportunistic pathogen for people with cystic fibrosis and chronic granulomatous disease. Intracellular survival in macrophages within a membrane-bound vacuole (BcCV) that delays acidification and maturation into lysosomes is a hallmark of B. cenocepacia infection. Intracellular B. cenocepacia induce an inflammatory response leading to macrophage cell death by pyroptosis through the secretion of a bacterial deamidase that results in the activation of the pyrin inflammasome. However, how or whether infected macrophages can process and present B. cenocepacia antigens to activate T-cells has not been explored. Engulfed bacterial protein antigens are cleaved into small peptides in the late endosomal major histocompatibility class II complex (MHC) compartment (MIIC). Here, we demonstrate that BcCVs and MIICs have overlapping features and that interferon-gamma-activated macrophages infected with B. cenocepacia can process bacterial antigens for presentation by class II MHC molecules to CD4⁺ T-cells and by class I MHC molecules to CD8⁺ T-cells. Infected macrophages also release processed bacterial peptides into the extracellular medium, stabilizing empty class I MHC molecules of bystander cells. Together, we conclude that BcCVs acquire MIIC characteristics, supporting the notion that macrophages infected with B. cenocepacia contribute to establishing an adaptive immune response against the pathogen.

Is SARS-CoV-2 Spike glycoprotein impairing macrophage function via α7-nicotinic acetylcholine receptors?

The innate immune cells play an important role in handling early infections, and can eliminate them completely up to a certain threshold. Beyond that threshold they take up their role in “The Resolution of Inflammation”. The recognition of the SARS-CoV-2 antigen triggers an eicosanoid storm and initiates a robust inflammatory response. This establishes a positive feedback loop which develops into a sustained cytokine storm which interferes with the activation of adaptive immune cells. The mechanism of this interaction, and hence the pathogenesis of the virus with the immune system, is yet to be determined. In silico studies predict a direct SARS-CoV-2 spike glycoprotein interaction with nicotinic acetylcholine receptors, which could impair macrophage function and initiate the cascade of events in severe infections. We here, add to the hypothesis that immune dysregulation can be caused by the interaction of the SARS-CoV-2 spike glycoprotein via a cryptic epitope with the α7-nAChR in Type-1 macrophages, discuss its implications for the treatment of COVID-19 patients, and present better prospects for the design and dissemination of more effective vaccines and their importance.

The Brilliance of Borrelia: Mechanisms of Host Immune Evasion by Lyme Disease-Causing Spirochetes

Lyme disease (LD) has become the most common vector-borne illness in the northern hemisphere. The causative agent, Borrelia burgdorferi sensu lato, is capable of establishing a persistent infection within the host. This is despite the activation of both the innate and adaptive immune responses. B. burgdorferi utilizes several immune evasion tactics ranging from the regulation of surface proteins, tick saliva, antimicrobial peptide resistance, and the disabling of the germinal center. This review aims to cover the various methods by which B. burgdorferi evades detection and destruction by the host immune response, examining both the innate and adaptive responses. By understanding the methods employed by B. burgdorferi to evade the host immune response, we gain a deeper knowledge of B. burgdorferi pathogenesis and Lyme disease, and gain insight into how to create novel, effective treatments.

STING negatively regulates allogeneic T-cell responses by constraining antigen-presenting cell function

Stimulator of interferon genes (STING)-mediated innate immune activation plays a key role in tumor- and self-DNA-elicited antitumor immunity and autoimmunity. However, STING can also suppress tumor immunity and autoimmunity. STING signaling in host nonhematopoietic cells was reported to either protect against or promote graft-versus-host disease (GVHD), a major complication of allogeneic hematopoietic cell transplantation (allo-HCT). Host hematopoietic antigen-presenting cells (APCs) play key roles in donor T-cell priming during GVHD initiation. However, how STING regulates host hematopoietic APCs after allo-HCT remains unknown. We utilized murine models of allo-HCT to assess the role of STING in hematopoietic APCs. STING-deficient recipients developed more severe GVHD after major histocompatibility complex-mismatched allo-HCT. Using bone marrow chimeras, we found that STING deficiency in host hematopoietic cells was primarily responsible for exacerbating the disease. Furthermore, STING on host CD11c⁺ cells played a dominant role in suppressing allogeneic T-cell responses. Mechanistically, STING deficiency resulted in increased survival, activation, and function of APCs, including macrophages and dendritic cells. Consistently, constitutive activation of STING attenuated the survival, activation, and function of APCs isolated from STING V154M knock-in mice. STING-deficient APCs augmented donor T-cell expansion, chemokine receptor expression, and migration into intestinal tissues, resulting in accelerated/exacerbated GVHD. Using pharmacologic approaches, we demonstrated that systemic administration of a STING agonist (bis-(3'-5')-cyclic dimeric guanosine monophosphate) to recipient mice before transplantation significantly reduced GVHD mortality. In conclusion, we revealed a novel role of STING in APC activity that dictates T-cell allogeneic responses and validated STING as a potential therapeutic target for controlling GVHD after allo-HCT.

CSF1R defines the mononuclear phagocyte system lineage in human blood in health and COVID-19

Mononuclear phagocytes defend tissues, present antigens, and mediate recovery and healing. To date, we lack a marker to unify mononuclear phagocytes in humans or that informs us about their origin. Here, we reassess mononuclear phagocyte ontogeny in human blood through the lineage receptor CSF1R, in the steady state and in COVID-19. We define CSF1R as the first sensitive and reproducible pan-phagocyte lineage marker, to identify and enumerate all conventional monocytes, and the myeloid dendritic cells. In the steady state, CSF1R is sufficient for sorting and immuno-magnetic isolation. In pathology, changes in CSF1R are more sensitive than CD14 and CD16. In COVID-19, a significant drop in membrane CSF1R is useful for stratifying patients, beyond the power of cell categories published thus far, which fail to capture COVID-19 specific events. Importantly, CSF1R defines cells which are neither conventional monocytes nor DCs, which are missed in published analysis. CSF1R decrease can be linked ex vivo to high CSF1 levels. Blood assessment of CSF1R+ cells opens a developmental window to the Mononuclear Phagocyte System in transit from bone marrow to tissues, supports isolation and phenotypic characterisation, identifies novel cell types, and singles out CSF1R inhibition as therapeutic target in COVID-19 and other diseases.

Dendritic cells: The first step

Ralph M. Steinman’s work on dendritic cells began in 1973 when he described and named the cells. Reminiscent of the late Justice Ginsburg’s perspective that enduring change happens not suddenly but one step at a time, the paper (1973. J. Exp. Med.https://doi.org/10.1084/jem.137.5.1142) was notably the first step in many steps of important work that revealed the nature of dendritic cells.

Acute Lymph Node Slices Are a Functional Model System to Study Immunity Ex Vivo

The lymph node is a highly organized and dynamic structure that is critical for facilitating the intercellular interactions that constitute adaptive immunity. Most ex vivo studies of the lymph node begin by reducing it to a cell suspension, thus losing the spatial organization, or fixing it, thus losing the ability to make repeated measurements. Live murine lymph node tissue slices offer the potential to retain spatial complexity and dynamic accessibility, but their viability, level of immune activation, and retention of antigen-specific functions have not been validated. Here we systematically characterized live murine lymph node slices as a platform to study immunity. Live lymph node slices maintained the expected spatial organization and cell populations while reflecting the 3D spatial complexity of the organ. Slices collected under optimized conditions were comparable to cell suspensions in terms of both 24-h viability and inflammation. Slices responded to T cell receptor cross-linking with increased surface marker expression and cytokine secretion, in some cases more strongly than matched lymphocyte cultures. Furthermore, slices processed protein antigens, and slices from vaccinated animals responded to ex vivo challenge with antigen-specific cytokine secretion. In summary, lymph node slices provide a versatile platform to investigate immune functions in spatially organized tissue, enabling well-defined stimulation, time-course analysis, and parallel read-outs.

Multinucleated Giant Cells in Adipose Tissue Are Specialized in Adipocyte Degradation

Obesity is associated with chronic low-grade inflammation of visceral adipose tissue (AT) characterized by an increasing number of AT macrophages (ATMs) and linked to type 2 diabetes. AT inflammation is histologically indicated by the formation of so-called crown-like structures, as ATMs accumulate around dying adipocytes, and the occurrence of multinucleated giant cells (MGCs). However, to date, the function of MGCs in obesity is unknown. Therefore, the aim of this study was to characterize MGCs in AT and unravel the function of these cells. We demonstrated that MGCs occurred in obese patients and after 24 weeks of a high-fat diet in mice, accompanying signs of AT inflammation and then representing ∼3% of ATMs in mice. Mechanistically, we found evidence that adipocyte death triggered MGC formation. Most importantly, MGCs in obese AT had a higher capacity to phagocytize oversized particles, such as adipocytes, as shown by live imaging of AT, 45-µm bead uptake ex vivo, and higher lipid content in vivo. Finally, we showed that interleukin-4 treatment was sufficient to increase the number of MGCs in AT, whereas other factors may be more important for endogenous MGC formation in vivo. Most importantly, our data suggest that MGCs are specialized for clearance of dead adipocytes in obesity.

Immune landscape and therapeutic strategies: new insights into PD-L1 in tumors

PD-1/PD-L1 axis represents an important target for renormalizing and resetting anti-tumor immunity in cancer patients. Currently, anti-PD-1/PD-L1 therapy has been applied in a broad spectrum of tumors and has yielded durable remission in patients. However, how to further broaden the application, guide personalized therapeutic strategies, and improve clinical responses remains a vital task. At present, PD-L1 expression is an important parameter of clinical indications for immune checkpoint blockade in many types of cancers, a strategy based on the supposition that positive PD-L1 expression reflects local T cell response. Recent studies have revealed that PD-L1 expression is regulated by multiple layers of complicated factors, during which the host immune microenvironment exerts a pivotal role and determines the clinical efficacy of the therapy. In this review, we will summarize recent findings on PD-1/PD-L1 in cancer, focusing on how local immune landscape participates in the regulation of PD-L1 expression and modification. Importantly, we will also discuss these topics in the context of clinical treatment and analyze how these fundamental principles might inspire our efforts to develop more precise and effective immune therapeutics for cancer.

Gliclazide alters macrophages polarization state in diabetic atherosclerosis in vitro via blocking AGE-RAGE/TLR4-reactive oxygen species-activated NF-kβ nexus

Hyperglycemic milieu in diabetes mellitus stimulates macrophages for exaggerated pro-inflammatory cytokine response, particularly IL-1β, IL-6, and TNF-α. Although hyperglycemia causes macrophages to produce pro-inflammatory cytokines, AGEs (advanced glycation end products) active inflammation, produced as a result of chronic hyperglycemia, inducers cause polarization of macrophages into pro-inflammatory M1 phenotype. AGEs in diabetes accelerate atherosclerotic plaque initiation and progression via promoting macrophages polarization towards pro-inflammatory state. Gliclazide (Glz) is a well known antidiabetic drug with excellent safety profile. Its repurposing in the management of diabetes-associated late complications has tremendous merit. The present study demonstrated that Glz retards diabetic atherosclerotic progression, and cytokines storm in a concentration dependent manner over a concentration range of 1-100 μM than those of AGEs (200 μg/ml)-treated cells through a mechanism that alters macrophage M1 polarization state. Glz exerted these beneficial effects, independent of its antidiabetic effect. Glz pretreatment significantly (P < 0.05) inhibited the AGEs-induced pro-inflammatory mediators (NO^•, reactive oxygen species, i-NOS), and production of pro-inflammatory cytokines, including IL-1β, IL-6, and TNF-α. It also significantly (P < 0.05) promoted the production of anti-inflammatory cytokines (IL-10 and TGF-β) in RAW 264.7 mouse macrophages. Glz pretreatment also effectively abated the AGEs-induced RAGE (~2-fold decrease), and CD86 surface marker expressions (P < 0.001 at 100 μM) on macrophages by inhibiting the NF-kβ activation in a concentration dependent manner (1-100 μM) (P < 0.001). In conclusion, our data demonstrates that Glz alleviates the diabetic atherosclerosis progression by ameliorating the AGEs-mediated M1 pro-inflammatory phenotype via blocking AGE-RAGE/TLR4-reactive oxygen species -activated NF-kβ nexus in macrophages.

A THP-1 Cell Line-Based Exploration of Immune Responses Toward Heat-Treated BLG

Allergen recognition and processing by antigen presenting cells is essential for the sensitization step of food allergy. Macrophages and dendritic cells are both phagocytic antigen presenting cells and play important roles in innate immune responses and signaling between the innate and adaptive immune system. To obtain a model system with a homogeneous genetic background, we derived macrophages and dendritic cells from THP-1 monocytes. The difference between macrophages and dendritic cells was clearly shown by differences in their transcription response (microarray) and protein expression levels. Their resemblance to primary cells was analyzed by comparison to properties as described in literature. The uptake of β-lactoglobulin after wet-heating (60°C in solution) by THP-1 derived macrophages was earlier reported to be significantly increased. To analyse the subsequent immune response, we incubated THP-1 derived macrophages and dendritic cells with native and differently processed β-lactoglobulin and determined the transcription and cytokine expression levels of the cells. A stronger transcriptional response was found in macrophages than in dendritic cells, while severely structurally modified β-lactoglobulin induced a more limited transcriptional response, especially when compared to native and limitedly modified β-lactoglobulin. These results show that processing is relevant for the transcriptional response toward β-lactoglobulin of innate immune cells.

Tumor β-catenin expression is associated with immune evasion in non-small cell lung cancer with high tumor mutation burden

β-catenin expression by tumor cells suppressed dendritic cell recruitment to the tumor microenvironment in a melanoma model, resulting in fewer tumor-infiltrating lymphocytes. Immunohistochemistry was used in the present study to examine the association between the expression of β-catenin and tumor infiltrating lymphocytes and CD11c⁺ cells in 122 patients with non-small cell lung cancer (NSCLC), who underwent radical surgery. β-catenin was positive in 24% of NSCLC tumors compared with 59% of squamous cell carcinomas and 11% of adenocarcinomas. There was no significant association between the expression of β-catenin and the frequency of CD8⁺ cell infiltration into tumor tissues, including the stroma. Conversely, the infiltration of CD8⁺ cells into tumor nests was significantly lower in β-catenin-positive cases compared with that in negative β-catenin cases. Similarly, CD11c⁺ cell infiltration was significantly lower in the β-catenin-positive group. The β-catenin-positive group had shorter overall survival and recurrence-free survival times compared with that in the negative group. Furthermore, β-catenin-positive NSCLC had a high tumor mutation burden, but tended to have a low expression of programmed death-ligand 1. In conclusion, the expression of β-catenin in NSCLC was negatively associated with CD11c⁺ cells and cytotoxic T cell infiltration at the tumor site and had a tendency towards a poor prognosis.

Pathology of macrophage activation syndrome in humanized NSGS mice

"Humanized" immunodeficient mice generated via the transplantation of CD34+ human hematopoietic stem cells (hHSC) are an important preclinical model system. The triple transgenic NOD.Cg-Prkdc^scidIl2rg^tm1Wjl Tg(CMV-IL3,CSF2,KITLG)1Eav/MloySzJ (NSGS) mouse line is increasingly used as recipient for CD34+ hHSC engraftment. NSGS mice combine the features of the highly immunodeficient NSG mice with transgenic expression of the human myeloid stimulatory cytokines GM-CSF, IL-3, and Kit ligand. While generating humanized NSGS (huNSGS) mice from two independent cohorts, we encountered a fatal macrophage activation syndrome (MAS)-like phenotype resulting from the transplantation of CD34+ hHSC. huNSGS mice exhibiting this phenotype declined clinically starting at approximately 10 weeks following CD34+ hHSC engraftment, with all mice requiring euthanasia by 16 weeks. Gross changes comprised small, irregular liver, splenomegaly, cardiomegaly, and generalized pallor. Hematological abnormalities included severe thrombocytopenia and anemia. Pathologically, huNSGS spontaneously developed a disseminated histiocytosis with infiltrates of activated macrophages and hemophagocytosis predominantly affecting the liver, spleen, bone marrow, and pancreas. The infiltrates were chimeric with a mixture of human and mouse macrophages. Immunohistochemistry suggested activation of the inflammasome in both human and murine macrophages. Active Epstein-Barr virus infection was not a feature. Although the affected mice exhibited robust chimerism of the spleen and bone marrow, the phenotype often developed in the face of low chimerism of the peripheral blood. Given the high penetrance and early lethality associated with the MAS-like phenotype here described, we urge caution when considering the use of huNSGS mice for the development of long-term studies.