Impact of human granulocyte and monocyte isolation procedures on functional studies

Differential composition and yield of leukocytes isolated from various blood component leukoreduction filters

In Flanders, an estimated 300,000 leukoreduction filters are discarded as biological waste in the blood establishment each year. These filters are a possible source of fresh donor leukocytes for downstream purposes including research. We investigated leukocyte isolation from two types of filters either used for the preparation of platelet concentrates (PC-LRF) or erythrocyte concentrates (EC-LRF). Outcome parameters were leukocyte yield, differential count, turnaround time and effect of storage conditions. Leukocytes were harvested by reverse flow of a buffer solution. Control was the gold standard density gradient centrifugation of buffy coats. Total leukocyte number isolated from PC-LRF (1049 (± 40) x 106) was almost double that of control (632 (± 66) x 106) but the differential count was comparable. Total leukocyte number isolated from EC-LRF (78 (± 9) x 106) was significantly lower than control, but the sample was specifically enriched in granulocytes (81 ± 4%) compared to control (30 ± 1%). Isolation of leukocytes from either PC- or EC-LRF takes 20 min compared to 240 min for control density gradient centrifugation. Leukocyte viability is optimal when harvested on day 1 post donation (95 ± 0.9%) compared to day 3 (76.4 ± 2.4%). In conclusion, our study demonstrates that leukoreduction filters from specific blood component processing are easy to use and present a valuable source for viable leukocytes of all types.

UK5099 Inhibits the NLRP3 Inflammasome Independently of its Long-Established Target Mitochondrial Pyruvate Carrier

Targeting NLRP3 inflammasome has been recognized as a promising therapeutic strategy for the treatment of numerous common diseases. UK5099, a long-established inhibitor of mitochondrial pyruvate carrier (MPC), is previously found to inhibit macrophage inflammatory responses independent of MPC expression. However, the mechanisms by which UK5099 inhibit inflammatory responses remain unclear. Here, it is shown that UK5099 is a potent inhibitor of the NLRP3 inflammasome in both mouse and human primary macrophages. UK5099 selectively suppresses the activation of the NLRP3 but not the NLRC4 or AIM2 inflammasomes. Of note, UK5099 retains activities on NLRP3 in macrophages devoid of MPC expression, indicating this inhibitory effect is MPC-independent. Mechanistically, UK5099 abrogates mitochondria-NLRP3 interaction and in turn inhibits the assembly of the NLRP3 inflammasome. Further, a single dose of UK5099 persistently reduces IL-1β production in an endotoxemia mouse model. Importantly, structure modification reveals that the inhibitory activities of UK5099 on NLRP3 are unrelated to the existence of the activated double bond within the UK5099 molecule. Thus, this study uncovers a previously unknown molecular target for UK5099, which not only offers a new candidate for the treatment of NLRP3-driven diseases but also confounds its use as an MPC inhibitor in immunometabolism studies.

Transcriptomics analysis highlights potential ways in human pathogenesis in Leishmania braziliensis infected with the viral endosymbiont LRV1

The parasite Leishmania (Viannia) braziliensis is widely distributed in Brazil and is one of the main species associated with human cases of different forms of tegumentary leishmaniasis (TL) such as cutaneous leishmaniasis (CL) and mucosal leishmaniasis (ML). The mechanisms underlying the pathogenesis of TL are still not fully understood, but it is known that factors related to the host and the parasite act in a synergistic and relevant way to direct the response to the infection. In the host, macrophages have a central connection with the parasite and play a fundamental role in the defense of the organism due to their ability to destroy intracellular parasites and present antigens. In the parasite, some intrinsic factors related to the species or even the strain analyzed are fundamental for the outcome of the disease. One of them is the presence of Leishmania RNA Virus 1 (LRV1), an endosymbiont virus that parasitizes some species of Leishmania that triggers a cascade of signals leading to a more severe TL phenotype, such as ML. One of the strategies for understanding factors associated with the immune response generated after Leishmania/host interaction is through the analysis of molecular patterns after infection. Thus, the gene expression profile in human monocyte-derived macrophages obtained from healthy donors infected in vitro with L. braziliensis positive (LbLRV1+) and negative (LbLRV1-) for LRV1 was evaluated. For this, the microarray assay was used and 162 differentially expressed genes were identified in the comparison LbLRV1+ vs. LbLRV1-, 126 upregulated genes for the type I and II interferons (IFN) signaling pathway, oligoadenylate synthase OAS/RNAse L, non-genomic actions of vitamin D3 and RIG-I type receptors, and 36 down-regulated. The top 10 downregulated genes along with the top 10 upregulated genes were considered for analysis. Type I interferon (IFNI)- and OAS-related pathways results were validated by RT-qPCR and Th1/Th2/Th17 cytokines were analyzed by Cytometric Bead Array (CBA) and enzyme-linked immunosorbent assay (ELISA). The microarray results validated by RT-qPCR showed differential expression of genes related to IFNI-mediated pathways with overexpression of different genes in cells infected with LbLRV1+ compared to LbLRV1- and to the control. No significant differences were found in cytokine levels between LbLRV1+ vs. LbLRV1- and control. The data suggest the activation of gene signaling pathways associated with the presence of LRV1 has not yet been reported so far. This study demonstrates, for the first time, the activation of the OAS/RNase L signaling pathway and the non-genomic actions of vitamin D3 when comparing infections with LbLRV1+ versus LbLRV1- and the control. This finding emphasizes the role of LRV1 in directing the host's immune response after infection, underlining the importance of identifying LRV1 in patients with TL to assess disease progression.

Analysis of Neutrophil Responses to Biological Exposures

Neutrophils are an important part of the innate immune system and among the first cells to respond to infections and inflammation. Responses include chemotaxis towards stimuli, extravasation from the vasculature, and antimicrobial actions such as phagocytosis, granule release, reactive oxygen species (ROS) production, and neutrophil extracellular trap (NET) formation (NETosis). Studying how neutrophils respond to a variety of stimuli, from biomaterial interactions to microbial insults, is therefore an essential undertaking to fully comprehend the immune response. While there are some immortalized cell lines available that recapitulate many neutrophil responses, ex vivo or in vivo studies are required to fully understand the complete range of neutrophil phenotypes. Here we describe two protocols for neutrophil isolation for further ex vivo study: recovery of neutrophils from human peripheral blood, and isolation of neutrophils from the oral cavity. We also discuss an in vivo model of general inflammation with the murine air pouch that can be used to assess numerous parameters of neutrophil and immune activation, including neutrophil recruitment and biological activity. In these protocols, the cells are isolated to allow for a high degree of experimental control. The protocols are relatively straightforward and can be successfully used by labs with no prior primary cell experience. © 2023 Wiley Periodicals LLC. Basic Protocol 1: Neutrophil isolation from human blood Basic Protocol 2: Neutrophil isolation from the oral cavity Basic Protocol 3: Murine air pouch model of general inflammation.

Monocyte-neutrophil entanglement in glioblastoma

Glioblastoma (GBM) is the most belligerent and frequent brain tumor in adults. Research over the past two decades has provided increased knowledge of the genomic and molecular landscape of GBM and highlighted the presence of a high degree of inter- and intratumor heterogeneity within the neoplastic compartment. It is now appreciated that GBMs are composed of multiple distinct and impressionable neoplastic and non-neoplastic cell types that form the unique brain tumor microenvironment (TME). Non-neoplastic cells in the TME form reciprocal interactions with neoplastic cells to promote tumor growth and invasion, and together they influence the tumor response to standard-of-care therapies as well as emerging immunotherapies. One of the most prevalent non-neoplastic cell types in the GBM TME are myeloid cells, the most abundant of which are of hematopoietic origin, including monocytes/monocyte-derived macrophages. Less abundant, although still a notable presence, are neutrophils of hematopoietic origin and intrinsic brain-resident microglia. In this Review we focus on neutrophils and monocytes that infiltrate tumors from the blood circulation, their heterogeneity, and their interactions with neoplastic cells and other non-neoplastic cells in the TME. We conclude with an overview of challenges in targeting these cells and discuss avenues for therapeutic exploitation to improve the dismal outcomes of patients with GBM.

Mechanism of action of IC 100, a humanized IgG4 monoclonal antibody targeting apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC)

Inflammasomes are multiprotein complexes of the innate immune response that recognize a diverse range of intracellular sensors of infection or cell damage and recruit the adaptor protein apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) into an inflammasome signaling complex. The recruitment, polymerization and cross-linking of ASC is upstream of caspase-1 activation and interleukin-1β release. Here we provide evidence that IC 100, a humanized IgG4κ monoclonal antibody against ASC, is internalized into the cell and localizes with endosomes, while another part is recycled and redistributed out of the cell. IC 100 binds intracellular ASC and blocks interleukin-1β release in a human whole blood cell inflammasome assay. In vitro studies demonstrate that IC 100 interferes with ASC polymerization and assembly of ASC specks. In vivo bioluminescence imaging showed that IC 100 has broad tissue distribution, crosses the blood brain barrier, and readily penetrates the brain and spinal cord parenchyma. Confocal microscopy of fluorescent-labeled IC 100 revealed that IC 100 is rapidly taken up by macrophages via a mechanism utilizing the Fc region of IC 100. Coimmunoprecipitation experiments and confocal immunohistochemistry showed that IC 100 binds to ASC and to the atypical antibody receptor Tripartite motif-containing protein-21 (TRIM21). In A549 WT and TRIM21 KO cells treated with either IC 100 or IgG4κ isotype control, the levels of intracellular IC 100 were higher than in the IgG4κ-treated controls at 2 hours, 1 day and 3 days after administration, indicating that IC 100 escapes degradation by the proteasome. Lastly, electron microscopy studies demonstrate that IC 100 binds to ASC filaments and alters the architecture of ASC filaments. Thus, IC 100 readily penetrates a variety of cell types, and it binds to intracellular ASC, but it is not degraded by the TRIM21 antibody-dependent intracellular neutralization pathway.

Characterization, Quantification, and Visualization of Neutrophil Extracellular Traps

Following the discovery of neutrophil extracellular traps (NETs) in 2004 by Brinkmann and colleagues, there has been extensive research into the role of NETs in a number of inflammatory diseases, including periodontitis. This chapter describes the current methods for the isolation of peripheral blood neutrophils as well as of oral neutrophils for subsequent NET experiments, including approaches to quantify and visualize NET production, the ability of NETs to entrap and kill bacteria, and the removal of NETs by nuclease-containing plasma.

Increased Circulating Epithelial Tumor Cells (CETC/CTC) over the Course of Adjuvant Radiotherapy Is a Predictor of Less Favorable Outcome in Patients with Early-Stage Breast Cancer

BACKGROUND

Adjuvant radiotherapy (RT) is an integral component of a multidisciplinary treatment strategy for early-stage breast cancer. It significantly reduces the incidence of loco-regional recurrence but also of distant events. Distant events are due to tumor cells disseminated from the primary tumor into lymphatic fluid or blood, circulating epithelial tumor cells (CETC/CTC), which can reach distant tissues and regrow into metastases. The purpose of this study is to determine changes in the number of CETC/CTC in the course of adjuvant RT, and to evaluate whether they are correlated to local recurrence and distant metastases in breast cancer patients.

METHODS

Blood from 165 patients irradiated between 2002 and 2012 was analyzed 0-6 weeks prior to and 0-6 weeks after RT using the maintrac® method, and patients were followed over a median period of 8.97 (1.16-19.09) years.

RESULTS

Patients with an increase in CETC/CTC numbers over the course of adjuvant RT had a significantly worse disease-free survival (p = 0.004) than patients with stable or decreasing CETC/CTC numbers. CETC/CTC behavior was the most important factor in predicting subsequent relapse-free survival. In particular, patients who had received neoadjuvant chemotherapy were disproportionately more likely to develop metastases when cell counts increased over the course of RT (p = 0.003; hazard ratio 4.886).

CONCLUSIONS

Using the maintrac® method, CETC/CTC were detected in almost all breast cancer patients after surgery. The increase in CETC/CTC numbers over the course of RT represents a potential predictive biomarker to judge relative risk/benefit in patients with early breast cancer. The results of this study highlight the need for prospective clinical trials on CETC/CTC status as a predictive criterion and for individualization of treatment.

CLINICAL TRIAL REGISTRATION

The trial is registered (2 May 2019) at trials.gov under NCT03935802.

MyD88-dependent signaling drives toll-like receptor-induced trained immunity in macrophages

Immunocompromised populations are highly vulnerable to developing life-threatening infections. Strategies to protect patients with weak immune responses are urgently needed. Employing trained immunity, whereby innate leukocytes undergo reprogramming upon exposure to a microbial product and respond more robustly to subsequent infection, is a promising approach. Previously, we demonstrated that the TLR4 agonist monophosphoryl lipid A (MPLA) induces trained immunity and confers broad resistance to infection. TLR4 signals through both MyD88- and TRIF-dependent cascades, but the relative contribution of each pathway to induction of trained immunity is unknown. Here, we show that MPLA-induced resistance to Staphylococcus aureus infection is lost in MyD88-KO, but not TRIF-KO, mice. The MyD88-activating agonist CpG (TLR9 agonist), but not TRIF-activating Poly I:C (TLR3 agonist), protects against infection in a macrophage-dependent manner. MPLA- and CpG-induced augmentation of macrophage metabolism and antimicrobial functions is blunted in MyD88-, but not TRIF-KO, macrophages. Augmentation of antimicrobial functions occurs in parallel to metabolic reprogramming and is dependent, in part, on mTOR activation. Splenic macrophages from CpG-treated mice confirmed that TLR/MyD88-induced reprogramming occurs in vivo. TLR/MyD88-triggered metabolic and functional reprogramming was reproduced in human monocyte-derived macrophages. These data show that MyD88-dependent signaling is critical in TLR-mediated trained immunity.

Neutrophil degranulation and severely impaired extracellular trap formation at the basis of susceptibility to infections of hemodialysis patients

BACKGROUND

Chronic kidney disease patients are at increased risk of mortality with cardiovascular diseases and infections as the two leading causes of death for end-stage kidney disease treated with hemodialysis (HD). Mortality from bacterial infections in HD patients is estimated to be 100-1000 times higher than in the healthy population.

METHODS

We comprehensively characterized highly pure circulating neutrophils from HD and healthy donors.

RESULTS

Protein levels and transcriptome of HD patients' neutrophils indicated massive neutrophil degranulation with a dramatic reduction in reactive oxygen species (ROS) production during an oxidative burst and defective oxidative cellular signaling. Moreover, HD neutrophils exhibit severely impaired ability to generate extracellular NET formation (NETosis) in NADPH oxidase-dependent or independent pathways, reflecting their loss of capacity to kill extracellular bacteria. Ectopic hydrogen peroxidase (H2O2) or recombinant human SOD-1 (rSOD-1) partly restores and improves the extent of HD dysfunctional neutrophil NET formation.

CONCLUSIONS

Our report is one of the first singular examples of severe and chronic impairment of NET formation leading to substantial clinical susceptibility to bacteremia that most likely results from the metabolic and environmental milieu typical to HD patients and not by common human genetic deficiencies. In this manner, aberrant gene expression and differential exocytosis of distinct granule populations could reflect the chronic defect in neutrophil functionality and their diminished ability to induce NETosis. Therefore, our findings suggest that targeting NETosis in HD patients may reduce infections, minimize their severity, and decrease the mortality rate from infections in this patient population.

Leishmania infantum Infection of Primary Human Myeloid Cells

Circulating phagocytic cells often serve as cellular targets for a large number of pathogens such as Leishmania parasites. Studying primary human cells in an infectious context requires lengthy procedures for cell isolation that may affect the analysis performed. Using whole blood and a no-lyse and no-wash flow cytometric assay (NoNo assay), we monitored the Leishmania infantum infection of primary human cells. We demonstrated, using fluorescent parasites, that among monocyte cell populations, L. infantum preferentially infects classical (CD14⁺CD16⁻) and intermediate (CD14⁺CD16⁺) primary human monocytes in whole blood. Because classical monocytes are the preponderant population, they represent the larger L. infantum reservoir. Moreover, we also found that, concomitantly to monocyte infection, a subset of PMNs is infected early in whole blood. Of interest, in whole blood, PMNs are less infected compared to classical monocytes. Overall, by using this NoNo assay, we provided a novel avenue in our understanding of host–leishmania interactions.

Optimization of the Transwell® assay for the analysis of neutrophil chemotaxis using flow cytometry to refine the clinical investigation of immunodeficient patients

Chemotaxis is the directed movement of neutrophils towards an infected site. This physiological process can be reproduced using a modified Boyden chamber, such as the Transwell® support. Different techniques can be used to count neutrophils after migration to the lower chamber of the holder. The present study supports the use of an optimized Transwell® assay coupled with a flow cytometry-based method (Sysmex XN-9000) to detect chemotaxis abnormalities. A reference interval of neutrophil's chemotaxis was determined as part of this work. A first step involves the extraction of neutrophils from whole blood. The migration of neutrophils from the upper to the lower support chamber is subsequently directed by a chemoattractant gradient using N-formyl-l-Methionyl-l-Leucyl-l-Phenylalanine (fMLP). Neutrophils collected in the lower chamber are finally counted by flow cytometry. The original protocol was optimized through the comparison of different parameters. The use of Polymorphprep®, in the extraction of neutrophils, showed an improvement of the neutrophils yield of 1.65 times (57.5% of recovery) compared to the extraction using the Ficoll-Hypaque® gradient. A solution containing 5% of Bovin Serum Albumin (BSA) was used to suspend the extracted neutrophils, stabilize their viability and preserve their integrity. The mechanical agitation of the Transwell® permeable supports during migration did not show an increase in neutrophil yield. A migration time of 1 h 30 was identified as the best time for collecting the largest number of neutrophils after migration. Finally, we demonstrated that scraping the bottom of the well after migration improved neutrophil collection from the lower chamber by 1.9-fold compared to a non-scraping method. In conclusion, our results support the use of Polymorphprep® and a 5% BSA solution in the suspension, without agitation of the medium. An incubation time of 1 h 30 was identified as optimal for neutrophil migration through the chamber. Scraping the bottom after neutrophil migration improved neutrophil collection yield. Normal adult values were obtained with directed migration equal to 32.4% ±13.41% on 15 men and 18 women.

Quiescence of Human Monocytes after Affinity Purification: A Novel Method Apt for Monocyte Stimulation Assays

Several methods to isolate monocytes from whole blood have been previously published, with different advantages and disadvantages. For the purpose of cytokine release assessment upon external stimulation, the use of monocyte preparations consisting of non-activated cells is prerequisite. Affinity-isolated monocyte preparations from peripheral blood mononuclear cells (PBMCs), obtained via positive or negative selection using magnetic beads, released pro-inflammatory cytokines such as TNF-α and IL-6 even without adding external stimuli, hindering any assessment of an effect of bacterial lipoproteins on cell stimulation. Hence, the cell preparation protocol was modified by adding a quiescence step on repellent surface culture plates, dampening any monocyte pre-activation. This protocol now provides a robust method to prepare silent yet fully activatable, pure monocyte populations for further use in stimulus-elicited activation experiments.

Transplantation of decellularised human amniotic membranes seeded with mesenchymal stem cell-educated macrophages into animal models

The reconstruction of chronic skin wounds remains a public health challenge in dermatology. Precisely controlling and monitoring the wound-healing process should result in enhanced outcomes for the patient. Cell-based therapies have shown great potential in medicine due to their immunomodulatory and healing properties. Herein, we produced activated macrophages by treating circulating monocytes with mesenchymal stem cell (MSC) supernatant. We also demonstrated the critical role of activated macrophages transplantation using amniotic membranes in accelerating wound healing in an animal wound model. The activated macrophages not only exhibited immunomodulatory cytokines like transforming growth factorβ (TGFβ) and interleukin 10 (and IL10) secretion but also showed attachment and proliferation ability on the amniotic membrane scaffold. Moreover, MSCs supernatant-treated cells also displayed significant ARG1, CD206, and IL 10 genes expression. Inspired by the in vitro results, we examined the in vivo therapeutic efficacy of the activated macrophage transplantation using an acellular amniotic membrane carrier in a full-thickness cutaneous wound model. The wound healing rate was significant in the group treated with macrophages generated via mesenchymal cell therapy seeded human amniotic membrane. There was less scarring in the wound sites after placing cell-scaffold constructs in the wound sites in the animal models. Overall, macrophages stimulated with mesenchymal cells' supernatant exhibited improved healing processes in incisional wounds by decreasing the inflammatory phase, increasing angiogenesis, and reducing scar tissue development.

Isolation of polymorphonuclear neutrophils and monocytes from a single sample of human peripheral blood

Monocytes and neutrophils are widely distributed throughout the body and play essential roles in health and disease. Here, we present a detailed protocol to isolate polymorphonuclear neutrophils and monocytes from a single sample of human peripheral blood. We have optimized several aspects of the procedure, including the density gradient, timing of each cell processing step, and the buffer/media conditions to preserve cell viability for subsequent functional assays. This protocol is reproducible and can be scaled as required for downstream applications.

For complete details on the use and execution of this protocol, please refer to Cui et al. (2021).

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A protocol for isolating neutrophils and monocytes from a single human blood sample

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Optimizes key processing steps to ensure high purity, yield, and viability of cells

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Scalable for a wide range of downstream applications

Neutrophil function and bactericidal activity against Staphylococcus aureus after cardiac surgery with cardiopulmonary bypass

Staphylococcus aureus is the main bacterial pathogen encountered in mediastinitis after cardiac surgical procedures; it remains a devastating complication with a high mortality rate. As neutrophils have a primordial role in the defense against staphylococcus infection and cardiopulmonary bypass (CPB) is known to induce immunosuppression, the aim of this study was to investigate CPB impact on neutrophil functions. Patients without known immunosuppression scheduled for cardiac surgery with CPB were included. Bone marrow and blood samples were harvested before, during, and after surgery. Neutrophil phenotypic maturation and functions (migration, adhesion, neutrophil extracellular trap [NET] release, reactive oxygen species (ROS) production, phagocytosis, and bacteria killing) were investigated. Two types of Staphylococcus aureus strains (one from asymptomatic nasal carriage and another from mediastinitis infected tissues) were used to assess in vitro bacterial direct impact on neutrophils. We found that CPB induced a systemic inflammation with an increase in circulating mature neutrophils after surgery. Bone marrow sample analysis did not reveal any modification of neutrophil maturation during CPB. Neutrophil lifespan was significantly increased and functions such as NET release and ROS production were enhanced after CPB whereas bacteria killing and phagocytosis were not impacted. Results were similar with the two different isolates of Staphylococcus aureus. These data suggest that CPB induces a recruitment of mature neutrophils via a demargination process rather than impacting their maturation in the bone marrow. In addition, neutrophils are fully efficient after CPB and do not contribute to postoperative immunosuppression.

Profiling single-cell level phagocytic activity distribution with blood lactate levels

The ability to kill infecting microbes is an essential facet of our immune response to an infection. However, phagocytic ability is often overlooked as a part of immunological profile in infected patients' diagnosis, as the understanding of phagocytic capabilities in disease states is incomplete. In this work, we have evaluated for the first time the relationship between blood lactate level and the neutrophil phagocytic activity at a single-cell level. Blood samples (N = 19) were grouped on the basis of their blood lactate levels i.e., below (control) or above 2 mmol L⁻¹ (high-risk) (i.e., 2 mmol L⁻¹ is a common clinical lactate threshold used for patients' triage). Neutrophils were isolated from whole blood and then incubated with fluorescent IgG coated beads for 40 minutes, and the ability of each neutrophil to internalize beads was quantified. Single-cell phagocytic activity analysis has shown interesting findings such as: (i) a single neutrophil was able to internalize up to 7 beads, (ii) for a control group, 39.76% cells didn't internalize any beads, while for a high-risk group, 30.65% cells didn't show any phagocytic activity, (iii) similarly, 30.46% cells internalize only 1 bead in a control group, while for a high-risk group the activity is slightly higher with only 31.73% cells showing single bead internalization, and (iv) 7 bead internalization activity was much higher for samples in a high-risk group (0.6% cells) compared to a control group (0.17% cells). We used multiple statistical tests to compare these differences. For a two-tailed T-test, we used the mean phagocytic activity of the cells (i.e., the average number of beads internalized by cells) isolated from the blood samples in the two groups (1.14 vs. 1.35) and found the p-value to be 0.08. We also used principal component analysis (PCA) on this high dimensional phagocytic activity distribution data and performed dimension reduction. However, the first 3 principal components didn't show a clear distinction between groups. Next, we developed machine learning models using artificial neural networks (ANNs) to differentiate between the distribution of phagocytic activity in neutrophil populations of the two groups. Our models yielded area under curve (AUC) values below 0.7 for receiver operator characteristic curves. Although our study highlighted interesting phagocytic activity findings at a single cell level, it further highlights the need for integration of an individual patient's medical record to get more personalized insights into individual phagocytic activity in the future.

Investigating the relationship between neutrophil phagocytic activity and blood lactate levels by employing single-cell data.

High Purity Isolation of Low Density Neutrophils Casts Doubt on Their Exceptionality in Health and Disease

Low density neutrophils (LDNs) are described in a number of inflammatory conditions, cancers and infections and associated with immunopathology, and a mechanistic role in disease. The role of LDNs at homeostasis in healthy individuals has not been investigated. We have developed an isolation protocol that generates high purity LDNs from healthy donors. Healthy LDNs were identical to healthy normal density neutrophils (NDNs), aside from reduced neutrophil extracellular trap formation. CD66b, CD16, CD15, CD10, CD54, CD62L, CXCR2, CD47 and CD11b were expressed at equivalent levels in healthy LDNs and NDNs and underwent apoptosis and ROS production interchangeably. Healthy LDNs had no differential effect on CD4⁺ or CD8⁺ T cell proliferation or IFNγ production compared with NDNs. LDNs were generated from healthy NDNs in vitro by activation with TNF, LPS or fMLF, suggesting a mechanism of LDN generation in disease however, we show neutrophilia in people with Cystic Fibrosis (CF) was not due to increased LDNs. LDNs are present in the neutrophil pool at homeostasis and have limited functional differences to NDNs. We conclude that increased LDN numbers in disease reflect the specific pathology or inflammatory environment and that neutrophil density alone is inadequate to classify discrete functional populations of neutrophils.

The Potential Use of Peripheral Blood Mononuclear Cells as Biomarkers for Treatment Response and Outcome Prediction in Psychiatry: A Systematic Review

BACKGROUND

Psychiatric disorders have a major impact on the global burden of disease while therapeutic interventions remain insufficient to adequately treat a large number of patients. Regrettably, the efficacy of several psychopharmacological treatment regimens becomes apparent only after 4-6 weeks, and at this point, a significant number of patients present as non-responsive. As such, many patients go weeks/months without appropriate treatment or symptom management. Adequate biomarkers for treatment success and outcome prediction are thus urgently needed.

OBJECTIVE

With this systematic review, we provide an overview of the use of peripheral blood mononuclear cells (PBMCs) and their signaling pathways in evaluating and/or predicting the effectiveness of different treatment regimens in the course of psychiatric illnesses. We highlight PBMC characteristics that (i) reflect treatment presence, (ii) allow differentiation of responders from non-responders, and (iii) prove predictive at baseline with regard to treatment outcome for a broad range of psychiatric intervention strategies.

REVIEW METHODS

A PubMed database search was performed to extract papers investigating the relation between any type of PBMC characteristic and treatment presence and/or outcome in patients suffering from severe mental illness. Criteria for eligibility were: written in English; psychiatric diagnosis based on DSM-III-R or newer; PBMC isolation via gradient centrifugation; comparison between treated and untreated patients via PBMC features; sample size ≥ n = 5 per experimental group. Papers not researching in vivo treatment effects between patients and healthy controls, non-clinical trials, and non-hypothesis-/data-driven (e.g., -omics designs) approaches were excluded.

DATA SYNTHESIS

Twenty-nine original articles were included and qualitatively summarized. Antidepressant and antipsychotic treatments were mostly reflected by intracellular inflammatory markers while intervention with mood stabilizers was evidenced through cell maturation pathways. Lastly, cell viability parameters mirrored predominantly non-pharmacological therapeutic strategies. As for response prediction, PBMC (subtype) counts and telomerase activity seemed most promising for antidepressant treatment outcome determination; full length brain-derived neurotrophic factor (BDNF)/truncated BDNF were shown to be most apt to prognosticate antipsychotic treatment.

CONCLUSIONS

We conclude that, although inherent limitations to and heterogeneity in study designs in combination with the scarce number of original studies hamper unambiguous identification, several PBMC characteristics-mostly related to inflammatory pathways and cell viability-indeed show promise towards establishment as clinically relevant treatment biomarkers.

An Unbiased Flow Cytometry-Based Approach to Assess Subset-Specific Circulating Monocyte Activation and Cytokine Profile in Whole Blood

Monocytes are the third most frequent type of leukocytes in humans, linking innate and adaptive immunity and are critical drivers in many inflammatory diseases. Based on the differential expression of surface antigens, three monocytic subpopulations have been suggested in humans and two in rats with varying inflammatory and phenotype characteristics. Potential intervention strategies that aim to manipulate these cells require an in-depth understanding of monocyte behavior under different conditions. However, monocytes are highly sensitive to their specific activation state and expression of surface markers, which can change during cell isolation and purification. Thus, there is an urgent need for an unbiased functional analysis of activation in monocyte subtypes, which is not affected by the isolation procedure. Here, we present a flow cytometry-based protocol for evaluating subset-specific activation and cytokine expression of circulating blood monocytes both in humans and rats using small whole blood samples (50 - 100 μL). In contrast to previously described monocyte isolation and flow cytometry visualization methods, the presented approach virtually leaves monocyte subsets in a resting state or fixes them in their current state and allows for an unbiased functional endpoint analysis without prior cell isolation. This protocol is a comprehensive tool for studying differential monocyte regulation in the inflammatory and allogeneic immune response in vitro and vivo.

Screening and validation of differentially expressed microRNAs and target genes in hypertensive mice induced by cytomegalovirus infection

Introduction: Multiple studies have suggested an association between cytomegalovirus (CMV) infection and essential hypertension (EH). MicroRNAs (miRNAs) play a critical role in the development of EH by regulating the expression of specific target genes. However, little is known about the role of miRNAs in CMV-induced EH. In the present study, we compared the miRNA expression profiles of samples from normal and murine cytomegalovirus (MCMV)-infected C57BL/6 mice using high-throughput sequencing analysis. Methods: We collected the thoracic aorta, heart tissues, and peripheral blood from 20 normal mice and 20 MCMV-infected mice. We identified differentially expressed miRNAs in the peripheral blood samples and predicted their target genes using bioinformatics tools. We then experimentally validated them using quantitative reverse transcription polymerase chain reaction (qRT-PCR) and the target genes with double luciferase reporter gene assay. Results: We found 118 differentially expressed miRNAs, among which 9 miRNAs were identified as potential MCMV infection-induced hypertension regulators. We then validated the expression of two candidate miRNAs, mmu-miR-1929-3p and mcmv-miR-m01-4-5p, using qRT-PCR. Furthermore, the dual-luciferase reporter gene assay revealed that the 3′-untranslated region (UTR) of endothelin A receptor (Ednra) messenger RNA (mRNA) contained a binding site for mmu-miR-1929-3p. Collectively, our data suggest that MCMV infection can raise the blood pressure and reduce mmu-miR-1929-3p expression in C57BL/6 mice. Moreover, we found that mmu-miR-1929-3p targets the 3′-UTR of the Ednra mRNA. Conclusion: This novel regulatory axis could aid the development of new approaches for the clinical prevention and control of EH.

Impact of SARS-CoV-2 infection on the recovery of peripheral blood mononuclear cells by density gradient

SARS-CoV-2 virus infection is responsible for coronavirus disease (COVID-19), which is characterised by a hyperinflammatory response that plays a major role in determining the respiratory and immune-mediated complications of this condition. While isolating peripheral blood mononuclear cells (PBMCs) from whole blood of COVID-19 patients by density gradient centrifugation, we noticed some changes in the floating properties and in the sedimentation of the cells on density medium. Investigating this further, we found that in early phase COVID-19 patients, characterised by reduced circulating lymphocytes and monocytes, the PBMC fraction contained surprisingly high levels of neutrophils. Furthermore, the neutrophil population exhibited alterations in the cell size and in the internal complexity, consistent with the presence of low density neutrophils (LDNs) and immature forms, which may explain the shift seen in the floating abilities and that may be predictive of the severity of the disease. The percentage of this subset of neutrophils found in the PBMC band was rather spread (35.4 ± 27.2%, with a median 28.8% and IQR 11.6-56.1, Welch's t-test early phase COVID-19 versus blood donor healthy controls P < 0.0001). Results confirm the presence of an increased number of LDNs in patients with early stage COVID-19, which correlates with disease severity and may be recovered by centrifugation on a density gradient together with PBMCs.

Metformin partially reverses the inhibitory effect of co-culture with ER-/PR-/HER2+ breast cancer cells on biomarkers of monocyte antitumor activity

BACKGROUND

Immune activities of monocytes (MOs) can be altered within the microenvironment of solid malignancies, including breast cancer. Metformin (1,1-dimethylbiguanide hydrochloride, MET), has been shown to decrease tumor cell proliferation, but its effects have yet to be explored with respect to MOs (monocytes) activity during their crosstalk with breast cancer cells. Here, we investigated the effects of MET on overall phenotypic functional activities, including cellular immunometabolism and protective redox signaling based-biomarkers, intracellular free calcium ions (ifCa2+), phagocytosis and co-operative cytokines (IFN-γ and IL-10) of autologous MOs before and during their interplay with primary ER-/PR-/HER2+ breast cancer cells.

METHODS

Human primary breast cancer cells were either cultured alone or co-cultured with autologous MOs before treatment with MET.

RESULTS

MET downregulated breast cancer cell proliferation and phagocytosis, while having no significant effect on the ratio of phosphorylated Akt (p-Akt) to total Akt. Additionally, we observed that, in the absence of MET treatment, the levels of lactate dehydrogenase (LDH)-based cytotoxicity, catalase, ifCa2+, IL-10 and arginase activity were significantly reduced in co-cultures compared to levels in MOs cultured alone whereas levels of inducible nitric oxide synthase (iNOS) activity were significantly increased. In contrast, MET treatment reduced the effects measured in co-culture on the levels of LDH-based cytotoxicity, arginase activity, catalase, ifCa2+, and IFN-γ. MET also induced upregulation of both iNOS and arginase in MO cells, although the increase did not reach significant difference for iNOS activity. Moreover, MET induced a robust increase of superoxide dismutase (SOD) activity in MOs, but not in MOs co-cultured with breast cancer cells. Furthermore, MET markedly upregulated the levels of IFN-γ production and downregulated those of IL-10 in isolated MOs, while inducing a slight opposing up-regulation of IL-10 production in co-cultures.

CONCLUSIONS

Our results show that the biomarkers of phenotypic functional activities of MOs are modified after co-culturing with primary human breast cancer cells. Treatment of co-cultures with MET resulted in increased release of antitumor cytokine IFN-γ and ifCa2+, and increased cell necrosis during breast cancer cells-MOs crosstalk.

Identification of a Novel HIF-1α-αMβ2 Integrin-NET Axis in Fibrotic Interstitial Lung Disease

Neutrophilic inflammation correlates with mortality in fibrotic interstitial lung disease (ILD) particularly in the most severe form, idiopathic pulmonary fibrosis (IPF), although the underlying mechanisms remain unclear. Neutrophil function is modulated by numerous factors, including integrin activation, inflammatory cytokines and hypoxia. Hypoxia has an important role in inflammation and may also contribute to pulmonary disease. We aimed to determine how neutrophil activation occurs in ILD and the relative importance of hypoxia. Using lung biopsies and bronchoalveolar lavage (BAL) fluid from ILD patients we investigated the extent of hypoxia and neutrophil activation in ILD lungs. Then we used ex vivo neutrophils isolated from healthy volunteers and BAL from patients with ILD and non-ILD controls to further investigate aberrant neutrophil activation in hypoxia and ILD. We demonstrate for the first time using intracellular staining, HIF-1α stabilization in neutrophils and endothelial cells in ILD lung biopsies. Hypoxia enhanced both spontaneous (+1.31-fold, p < 0.05) and phorbol 12-myristate 13-acetate (PMA)-induced (+1.65-fold, p < 0.001) neutrophil extracellular trap (NET) release, neutrophil adhesion (+8.8-fold, <0.05), and trans-endothelial migration (+1.9-fold, p < 0.05). Hypoxia also increased neutrophil expression of the αM (+3.1-fold, p < 0.001) and αX (+1.6-fold, p < 0.01) integrin subunits. Interestingly, NET formation was induced by αMβ2 integrin activation and prevented by cation chelation. Finally, we observed NET-like structures in IPF lung sections and in the BAL from ILD patients, and quantification showed increased cell-free DNA content (+5.5-fold, p < 0.01) and MPO-citrullinated histone H3 complexes (+21.9-fold, p < 0.01) in BAL from ILD patients compared to non-ILD controls. In conclusion, HIF-1α upregulation may augment neutrophil recruitment and activation within the lung interstitium through activation of β2 integrins. Our results identify a novel HIF-1α- αMβ2 integrin axis in NET formation for future exploration in therapeutic approaches to fibrotic ILD.

The secretome of senescent preadipocytes influences the phenotype and function of cells of the vascular wall

Senescent cells accumulate in numerous tissues in several chronic conditions such as aging, obesity, and diabetes. These cells are in a state of irreversible cell-cycle arrest and secrete inflammatory cytokines, chemokines and other immune modulators that have paracrine effects on nearby tissues. Adipose tissue, in particular, harbors senescent cells, which have been linked with numerous chronic conditions and age-related comorbidities. Here we performed a series of in vitro experiments to determine the influence of senescent preadipocytes on key cell types found in vessel walls, including vascular smooth muscle cells (VSMCs), endothelial cells (ECs), macrophages (MQs), and adipose-derived stromal/stem cells (ASCs). Primary human preadipocytes were irradiated to trigger a senescence-like phenotype. VSMCs, ECs, MQs, and ASCs were exposed to conditioned media collected from irradiated preadipocytes or control preadipocytes. Additional experiments were performed where VSMCs, ECs, MQs, and ASCs were co-cultured with irradiated or control preadipocytes. The secretome of irradiated cells induced an inflammatory phenotype, decreased cell viability, disrupted proliferation and migration, and impaired metabolic function of these cell types in vitro. These maladaptive changes in response to senescent cell exposure provide early evidence in support of a hypothesis that senescent preadipocytes trigger phenotypic and functional changes in key cellular components of blood vessels that may contribute to vascular disease.

A protocol for rapid monocyte isolation and generation of singular human monocyte-derived dendritic cells

The monocyte-derived dendritic cells (moDCs) are a subset of dendritic cells widely used in immunological studies as a convenient and easy approach after isolation of mononuclear cells directly from peripheral blood mononuclear cells (PBMC). Both the purification and cell culture of monocytes impact on the differentiation of monocytes into moDCs. The methodology to isolate and differentiate monocytes into moDCs is still controversial. We aimed to compare three different protocols for monocyte isolation from PBMC: 1) Cold-aggregation; 2) Percoll gradient; and 3) Magnetic beads cell-enrichment. Additionally we also compared four different monocyte differentiation and culture techniques: 1) Cell culture media; 2) Serum sources; 3) required GM-CSF and IL-4 concentrations; 4) Cell culture systems. We used flow cytometry analysis of light scattering and/or expression of pan surface markers, such as CD3, CD14 and CD209 to determine isolation/differentiation degree. Purified PBMC followed by two steps of cold aggregation, yielded cell viability around 95% with poor monocyte enrichment (monocytes increase vs. lymphocytes reduction was not statistically significant, p>0.05). Conversely, monocyte isolation from PBMC with discontinuous Percoll gradient generated around 50% cell viability. Albeit, we observed a significant reduction (p≤0.05) of lymphocytes contaminants. The magnetic beads cell-enrichment yield cell viability higher than 95%, as high as a significant lymphocyte depletion (p≤0.005) when compared to all other techniques employed. The moDCs showed better differentiation based on increased CD209 expression, but lower CD14 levels, when cells were cultured in RPMI medium plus 500IU/mL of both GM-CSF and IL-4 in a semi-adherent fashion. Serum sources showed no influence on the culture performance. In conclusion, the magnetic beads cell-enrichment showed superior cell viability, indicating that this approach is a better choice to isolate monocytes, and moDCs cultured afterwards in appropriate medium, serum, cytokines and culture system might influence the monocytes differentiation into moDC.

Methods of Granulocyte Isolation from Human Blood and Labeling with Multimodal Superparamagnetic Iron Oxide Nanoparticles

This in vitro study aimed to find the best method of granulocyte isolation for subsequent labeling with multimodal nanoparticles (magnetic and fluorescent properties) to enable detection by optical and magnetic resonance imaging (MRI) techniques. The granulocytes were obtained from venous blood samples from 12 healthy volunteers. To achieve high purity and yield, four different methods of granulocyte isolation were evaluated. The isolated granulocytes were labeled with multimodal superparamagnetic iron oxide nanoparticles (M-SPIONs) coated with dextran, and the iron load was evaluated qualitatively and quantitatively by MRI, near-infrared fluorescence (NIRF) and inductively coupled plasma mass spectrometry (ICP-MS). The best method of granulocyte isolation was Percoll with Ficoll, which showed 95.92% purity and 94% viability. After labeling with M-SPIONs, the granulocytes showed 98.0% purity with a yield of 3.5 × 10⁶ cells/mL and more than 98.6% viability. The iron-loading value in the labeled granulocytes, as obtained by MRI, was 6.40 ± 0.18 pg/cell. Similar values were found with the ICP-MS and NIRF imaging techniques. Therefore, our study shows that it is possible to isolate granulocytes with high purity and yield and labeling with M-SPIONs provides a high internalized iron load and low toxicity to cells. Therefore, these M-SPION-labeled granulocytes could be a promising candidate for future use in inflammation/infection detection by optical and MRI techniques.

Monocyte isolation techniques significantly impact the phenotype of both isolated monocytes and derived macrophages in vitro

Monocyte-derived macrophages (MDMs) generated from peripheral blood monocytes are widely used to model human macrophages for in vitro studies. However, the possible impact of different isolation methods on the resulting MDM phenotype is poorly described. We aimed to investigate the effects of three commonly used monocyte isolation techniques on the resulting MDM phenotype. Plastic adhesion, negative selection, and CD14^pos selection were compared. Monocyte-derived macrophages were generated by 5-day culture with macrophage and granulocyte-macrophage colony-stimulating factors. We investigated monocyte and MDM yields, purity, viability, and cell phenotype. CD14^pos selection resulted in highest monocyte yield (19·8 × 10⁶ cells, equivalent to 70% of total) and purity (98·7%), compared with negative selection (17·7 × 10⁶ cells, 61% of total, 85·0% purity), and plastic adhesion (6·1 × 10⁶ cells, 12·9% of total, 44·2% purity). Negatively selected monocytes were highly contaminated with platelets. Expression of CD163 and CD14 were significantly lower on CD14^pos selection and plastic adhesion monocytes, compared with untouched peripheral blood mononuclear cells. After maturation, CD14^pos selection also resulted in the highest MDM purity (98·2%) compared with negative selection (94·5%) and plastic adhesion (66·1%). Furthermore, MDMs from plastic adhesion were M1-skewed (CD80^high  HLA-DR^high  CD163^low ), whereas negative selection MDMs were M2-skewed (CD80^low  HLA-DR^low  CD163^high ). Choice of monocyte isolation method not only significantly affects yield and purity, but also impacts resulting phenotype of cultured MDMs. These differences may partly be explained by the presence of contaminating cells when using plastic adherence or negative selection. Careful considerations of monocyte isolation methods are important for designing in vitro assays on MDMs.

Low Density Granulocytes in ANCA Vasculitis Are Heterogenous and Hypo-Responsive to Anti-Myeloperoxidase Antibodies

Low Density Granulocytes (LDGs), which appear in the peripheral blood mononuclear cell layer of density-separated blood, are seen in cancer, sepsis, autoimmunity, and pregnancy. Their significance in ANCA vasculitis (AAV) is little understood. As these cells bear the autoantigens associated with this condition and have been found to undergo spontaneous NETosis in other diseases, we hypothesized that they were key drivers of vascular inflammation. We found that LDGs comprise a 3-fold higher fraction of total granulocytes in active vs. remission AAV and disease controls. They are heterogeneous, split between cells displaying mature (75%), and immature (25%) phenotypes. Surprisingly, LDGs (unlike normal density granulocytes) are hyporesponsive to anti-myeloperoxidase antibody stimulation, despite expressing myeloperoxidase on their surface. They are characterized by reduced CD16, CD88, and CD10 expression, higher LOX-1 expression and immature nuclear morphology. Reduced CD16 expression is like that observed in the LDG population in umbilical cord blood and in granulocytes of humanized mice treated with G-CSF. LDGs in AAV are thus a mixed population of mature and immature neutrophils. Their poor response to anti-MPO stimulation suggests that, rather than being a primary driver of AAV pathogenesis, LDGs display characteristics consistent with generic emergency granulopoiesis responders in the context of acute inflammation.

FACS isolation and analysis of human circulating and tumor neutrophils

The role of neutrophils in tumor growth and metastasis is still controversial. Studies in clinically relevant models of cancer have shown that neutrophils can promote tumor growth and development and metastasis, or inhibit it. Thus, further analysis is required to fully elucidate the role of neutrophils in cancer. A number of different methods are available for neutrophil isolation and characterization. However, Fluorescence-activated cell sorting (FACS) is particularly effective for isolating neutrophils and assessing their phenotype as it allows for the simultaneous use of multiple cell surface markers, can be used for isolation of both blood and tumor neutrophils and features a high purity and high yields.

A simple and effective method for the isolation and culture of human monocytes from small volumes of peripheral blood

Innate immune cell defects contribute to severe autoimmunity and the pathogenesis of inflammatory disease. Monocyte-derived macrophages typically retain disease related signatures and represent an excellent in vitro model to uncover and validate mechanisms contributing to specific pathological states. Monocyte isolation procedures vary widely in terms of purity, yield, cost, degree of technical difficulty and volume of peripheral blood needed. This paper outlines a novel isolation method that yields monocytes through density gradient centrifugation (Ficoll® and hyperosmotic Percoll®). The protocol has been optimised for small volumes of blood (42 ml) and is simple, reproducible and inexpensive compared to other methods. Monocyte recovery is 70% (relative to monocyte numbers within the buffy coat) and the highly functional macrophages produced are characterised by excellent purity (98.6 ± 0.6%) and intact activation and phagocytic capacities. The method is well suited to investigations involving patient populations where a particular subset of immune cells is known to contribute to the pathogenesis of a specific disease or is aberrant as a consequence of that disease.

Whole blood assay as a model for in vitro evaluation of inflammasome activation and subsequent caspase-mediated interleukin-1 beta release

Processing of pro-interleukin (IL)-1β and IL-18 is regulated by multiprotein complexes, known as inflammasomes. Inflammasome activation results in generation of bioactive IL-1β and IL-18, which can exert potent pro-inflammatory effects. Our aim was to develop a whole blood-based assay to study the inflammasome in vitro and that also can be used as an assay in clinical studies. We show whole blood is a suitable milieu to study inflammasome activation in primary human monocytes. We demonstrated that unprocessed human blood cells can be stimulated to activate the inflammasome by the addition of adenosine 5'-triphosphate (ATP) within a narrow timeframe following lipopolysaccharide (LPS) priming. Stimulation with LPS resulted in IL-1β release; however, addition of ATP is necessary for "full-blown" inflammasome stimulation resulting in high IL-1β and IL-18 release. Intracellular cytokine staining demonstrated monocytes are the major producers of IL-1β in human whole blood cultures, and this was associated with activation of caspase-1/4/5, as detected by a fluorescently labelled caspase-1/4/5 probe. By applying caspase inhibitors, we show that both the canonical inflammasome pathway (via caspase-1) as well as the non-canonical inflammasome pathway (via caspases-4 and 5) can be studied using this whole blood-based model.

Altered profile of immune regulatory cells in the peripheral blood of lymphoma patients

BACKGROUND

Regulatory immune cells may modulate the lymphoma microenvironment and are of great interest due to the increasing prevalence of treatment with immunotherapies in lymphoma patients. The aim was to explore the composition of different immune regulatory cell subsets in the peripheral blood of newly diagnosed lymphoma patients in relation to treatment outcome.

METHODS

Forty-three newly diagnosed patients with lymphoma were included in the study; 24 with high-grade B-cell lymphoma (HGBCL) and 19 with classical Hodgkin lymphoma (cHL). Peripheral blood was prospectively collected and immune regulatory cells were identified by multi-color flow cytometry and analyzed in relation to healthy blood donors and clinical characteristics and outcome.

RESULTS

The percentage of CD3-positive T-cells was lower (p = 0.03) in the peripheral blood of lymphoma patients at diagnosis compared to healthy blood donors regardless of lymphoma subtype, although statistically, neither the percentage of monocytes (p = 0.2) nor the T-cell/monocyte ratio (p = 0.055) differed significantly. A significant decrease in the percentage of a subset of regulatory NK cells (CD7⁺/CD3^-/CD56^bright/CD16^dim/-) was identified in the peripheral blood of lymphoma patients compared to healthy blood donors (p = 0.003). Lymphoma patients also had more granulocytic myeloid-derived suppressor cells (MDSCs) (p = 0.003) compared to healthy blood donors, whereas monocytic MDSCs did not differ significantly (p = 0.07). A superior disease-free survival was observed for cHL patients who had an increase in the percentage of granulocytic MDSCs (p = 0.04).

CONCLUSIONS

An altered profile of immune cells in the peripheral blood with a decrease in T-cells and regulatory NK-cells was observed in newly diagnosed lymphoma patients. CHL patients with higher percentages of regulatory NK cells and higher percentages of granulocytic MDSCs might have a better outcome, although the number of patients was low.

CgAATase with specific expression pattern can be used as a potential surface marker for oyster granulocytes

Granulocytes are known as the main immunocompetent hemocytes that play important roles in the immune defense of oyster Crassostrea gigas. In the present study, an alcohol acyltransferase (designed as CgAATase) with specific expression pattern was identified from oyster C. gigas, and it could be employed as a potential marker for the isolation of oyster granulocytes. The open reading frame (ORF) of CgAATase was of 1431 bp, encoding a peptide of 476 amino acids with a typically conserved AATase domain. The mRNA transcripts of CgAATase were highest expressed in hemocytes, lower expressed in hepatopancreas, mantle, gonad, gill, ganglion, adductor muscle, and labial palp. The mRNA expression level of CgAATase in hemocytes was significantly up-regulated at 3-12 h and reached the highest level (27.40-fold compared to control group, p < 0.05) at 6 h after Vibrio splendidus stimulation. The total hemocytes were sorted as granulocytes, semi-granulocytes and agranulocytes by Percoll^® density gradient centrifugation. CgAATase transcripts were dominantly observed in granulocytes, which was 8.26-fold (p < 0.05) and 2.80-fold (p < 0.05) of that in agranulocytes and semi-granulocytes, respectively. The monoclonal antibody against CgAATase was produced and employed for the isolation of granulocytes with the immunomagnetic bead. CgAATase protein was mainly detected on the cytomembrane of granulocytes. About 85.7 ± 4.60% of the granulocytes were positive for CgAATase and they could be successfully separated by flow cytometry with immunomagnetic bead coated with anti-CgAATase monoclonal antibody, and 97.7 ± 1.01% of the rest hemocytes (agranulocytes and semi-granulocytes) were negative for CgAATase. The isolated primary granulocytes could maintain cell activity for more than one week in vitro culture that exhibited numerous filopodia. These results collectively suggested that CgAATase was a potential marker of oyster granulocytes, and the granulocytes could be effectively isolated from total circulating hemocytes by immunomagnetic bead coated with the anti-CgAATase monoclonal antibody.

Imaging the neutrophil: Intravital microscopy provides a dynamic view of neutrophil functions in host immunity

Neutrophils are the first cellular responders of the immune system. They employ their impressive arsenal of microbicidal molecules to provide rapid and efficient defense against pathogens. However, the role of neutrophils extends far beyond microbial destruction to include tissue repair and remodeling, provision of signals to the adaptive immune system and body homeostasis. Intravital imaging has allowed the visualization of neutrophils in their native environment in both health and disease and provided crucial insights into their mechanisms of action. In the last few years the power of intravital imaging has been considerably extended by the introduction of photoconvertible proteins and intracellular signaling reporter mice. This review will highlight recent advances in our understanding of neutrophil biology based on the use of intravital microscopy to visualize their modus operandi in vivo including migration in and out of inflamed tissues, host-pathogen interactions and cell fate.

Time course of chemotaxis and chemokinesis of neutrophils following stimulation with IL-8 or FMLP

Polymorphonuclear cells (PMNs) attend to inflammatory sites by chemotactic movement, caused by chemoattractants (CAs) like n-formyl-l-methionyl-l-leucyl-l-phenylalanine (FMLP) and interleukin-8 (IL-8). However, distinct but applicable assays for investigations of PMNs’ migration limit in vitro examination. We integrated CD15-bead-based isolation of PMNs with analysing their chemotaxis in a novel 3D-µ-Slide migration chamber. The PMNs were exposed to different concentrations of FMLP and IL-8 (1, 10 and 100 nM) and observed for 180 min in cell-physiological environment conditions. Moving PMNs’ percentage (median and interquartile range) decreased from 62% (27%) to 36% (31%) without CA, from 88% (30%) to 22% (26%) for 1 nM IL-8, from 70% (22%) to 28% (13%) for 100 nM IL-8, from 30% (23%) to 18% (46%) for 1 nM FMLP and from 76% (20%) to 28% (13%) for 100 nM FMLP. Centres of cell movement turned towards the CAs (negative values) within a single 30-min observation period: 5.37 µm (16.82 µm) without CA, −181.37 µm (132.18 µm) with 10 nM and −239.34 µm (152.19 µm) with 100 nM IL-8; −116.2 µm (69.07 µm) with 10 nM and −71.59 µm (98.58 µm) with 100 nM FMLP. FMLP and IL-8 ensure chemotaxis without increase of chemokinesis. 3D-µ-Slide chemotaxis chambers facilitate time course analyses of PMNs’ migration in stable conditions over a long time with concise distinction of chemotaxis and chemokinesis.

Monocytes in rheumatoid arthritis: Circulating precursors of macrophages and osteoclasts and, their heterogeneity and plasticity role in RA pathogenesis

Rheumatoid arthritis (RA) is a chronic systemic, autoimmune and inflammatory disease represented as synovitis, pannus formation, adjacent bone erosions, and joint destruction. The major cells involved in the perpetuation of RA pathogenesis are CD4⁺ T-cells (mainly Th1 cells and Th17 cells), fibroblasts like synoviocytes (FLS), macrophages and B cells. Other autoimmune cells such as dendritic cells, neutrophils, mast cells, and monocytes also contribute to RA pathogenesis. Monocytes are mainly bone marrow (BM) derived cells in the circulation. The chemokine receptors CCR2 and CX3CR1 expressed by monocytes interact with chemokine ligands CCL2 (MCP-1) and CX3CL1 (fractalkine) respectively produced by FLS and this interaction promotes their migration and recruitment into RA synovium. Activated monocytes on their surface exhibit upregulated antigenic expressions such as CD14, CD16, HLA-DR, toll-like receptors (TLRs), and adhesion molecules B1 and B2 integrins. RA monocytes interconnect with other cells in a positive loop manner in the propagation of the rheumatoid process. They skew towards mainly intermediate monocyte subsets (CD14⁺⁺ CD16⁺) which produce proinflammatory cytokines such as TNF-α, IL-1β, and IL-6. Moreover, the predominant intermediate monocytes in RA differentiate into M1-macrophages which play a major role in synovial inflammation. Demonstrations suggest monocytes with CD14⁺ and CD16^- expression (classical monocytes?) differentiate to osteoclasts which are the cells responsible for bone erosion in RA synovial joints. Th17 cells induce the production of RANKL by FLS which promotes osteoclastogenesis. Cytokines mainly TNF-α, IL-1β, and IL-6 amplify osteoclastogenesis. Hence, monocytes are the circulating precursors of macrophages and osteoclasts in RA. AIM OF THE REVIEW: To enlighten the identity of monocytes, the antigenic expression on monocyte surface and their cytokines role in RA. We also emphasize about the chemokine receptors expressed by monocytes subsets and chemotaxis of circulating monocytes into RA synovium. Additionally, we review monocytes as the circulating precursors of macrophages and osteoclasts in RA joints and their heterogeneity and plasticity role in RA.

Saccharomyces cerevisiae var. boulardii CNCM I-1079 and Lactobacillus acidophilus BT1386 influence innate immune response and serum levels of acute-phase proteins during weaning in Holstein calves

The aims of this study were to investigate the effect of Saccharomyces cerevisiae var. boulardii CNCM I-1079 (SCB) or Lactobacillus acidophilus BT1386 (LA) on (1) innate immune response, (2) markers of acute-phase reaction, and (3) immune gene expression of rumen and ileum tissues of Holstein calves. Forty eight calves (∼5 d old) were randomly allocated to four treatments as follows: (1) control (CTRL) fed milk replacer followed by starter feed, (2) CTRL supplemented with SCB in milk and feed, (3) CTRL supplemented with LA in milk and feed, and (4) CTRL supplemented with antibiotics (ATB; chlortetracycline and neomycin in milk, and chlortetracycline in feed). Tumor necrosis factor α (TNF-α) decreased (P < 0.05) on day 66 (post-weaning) for the ATB-treated calves. There were no treatment effects on production of interferon γ (IFN-γ) and interleukin 6 (IL-6) proteins and on expression of TLR4, TLR6, TLR9, TLR10, CLDN3, MUC1, and MUC20 genes. Calves fed SCB or LA had a greater (P < 0.05) oxidative burst at weaning (day 53) compared with CTRL. Oxidative burst was also greater (P < 0.05) after weaning (day 59 and day 87) for SCB-fed calves. Calves fed SCB and ATB had higher (P < 0.05) phagocytosis activity during weaning (day 47) compared with CTRL. The concentration of serum amyloid A2 (SAA2) increased (P < 0.05) in SCB- and LA-fed calves (day 53), whereas the concentration of C-reactive protein (CRP) increased (P < 0.05) in SCB-fed calves during weaning as compared with CTRL. Our results suggest that SCB could improve innate immune response (oxidative burst and phagocytosis) and markers of acute-phase reaction (CRP and SAA2), especially during critical periods like weaning.

Effects of Hydrocortisone on Regulating Inflammation, Hemodynamic Stability, and Preventing Shock in Severe Sepsis Patients

Background

Severe sepsis is among the most common causes of death in Emergency Departments, with more than 30% mortality. Hydrocortisone is used in severe sepsis patients who were not responsive to fluid resuscitation and vasopressor therapy. However, the effect of hydrocortisone on regulating inflammation, hemodynamic stability, and preventing shock is still unclear in Chinese patients.

Material/Methods

In this prospective observational study, we included 105 severe sepsis patients. We measured the level of serum inflammatory cytokines, hemodynamic variables, and phagocytic ability of innate immune cells during the treatment. We analyzed the relationship between these variables and the hydrocortisone treatment.

Results

We treated 43 (41.0%) patients with hydrocortisone, while the other 62 (59.0%) patients were not, based on their response to fluid resuscitation and vasopressor therapy. The hydrocortisone group had a mean simplified acute physiology score (SAPS) II score of 41.8 with standard deviation (SD) of 7.1, while the non-hydrocortisone group had a mean SAPS II score of 36.7 with SD of 7.3. The mean sequential organ failure assessment (SOFA) scores of these 2 groups were 10.6 and 9.2, respectively. We found an obvious decrease of serum pro-inflammatory cytokines, including interleukin-1β (IL-1β), interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), and IL-6, after hydrocortisone treatment. However, these changes were not observed in the non-hydrocortisone group. What’s more, amelioration of hemodynamic variables was observed after hydrocortisone treatment. No significant association between hydrocortisone treatment and innate immune cell phagocytic function was observed.

Conclusions

Based on these results, we believe that hydrocortisone treatment has potential anti-inflammatory, hemodynamic reversal, and stability effects on severe sepsis patients. These key benefits may help patients by preventing septic shock.

Peptidoglycan Suppresses Phagocytic Activities and Apoptosis of Macrophages in Colonic Mucosa Tissues of Crohn's Disease Patients and In Vitro

Background

Rac1 signaling plays a crucial role in controlling macrophage functions in CD. Peptidoglycan triggers several intracellular signaling pathways, including activation of Rac1, to regulate the function of macrophage. Suppressed Rac1 signaling in non-inflamed colonic mucosa of Crohn’s disease patients has been shown to correlate with increased innate immunity.

Material/Methods

We examined the effect of peptidoglycan on Rac1 signaling in macrophages and mucosal tissue samples collected from 10 patients with active Crohn’s disease and further investigated the effects of peptidoglycan on apoptosis and phagocytic activities of macrophages in vitro.

Results

Macrophage infiltration and Rac1 signaling was increased in inflamed mucosal tissues of Crohn’s disease patients. Immunoblotting assays revealed that peptidoglycan dose- and time-dependently increased the expression of Rac1-GTP, phosphorylated VAV1, and phosphorylated PAK1in RAW264.7 macrophages, which, however, was attenuated by 6-thioguanine. Peptidoglycan also dose-dependently inhibited phagocytic activities of human peripheral blood monocytic cells (PBMCs), which were partially abated by 6-thioguanine or NSC23766. Flow cytometry showed that peptidoglycan (3 μg/mL) decreased the proportion of apoptotic human PBMCs versus controls. The addition of 6-thioguanine or NSC3766 to peptidoglycan led to a sharper rise in the proportion of apoptotic human PBMCs than 6-thioguanine or NSC3766 alone.

Conclusions

Our findings suggest that Rac1 signaling is a common molecular target shared by peptidoglycan and immunosuppressive treatment in intestinal macrophages. Inhibiting Rac1 activation may be crucial for optimizing macrophage immunity for treatment of Crohn’s disease.

Differential Interaction of Platelet-Derived Extracellular Vesicles with Leukocyte Subsets in Human Whole Blood

Secretion and exchange of biomolecules via extracellular vesicles (EVs) are crucial mechanisms in intercellular communication, and the roles of EVs in infection, inflammation, or thrombosis have been increasingly recognized. EVs have emerged as central players in immune regulation and can enhance or suppress the immune response, depending on the state of donor and recipient cells. We investigated the interaction of blood cell-derived EVs with leukocyte subpopulations (monocytes and their subsets, granulocytes, B cells, T cells, and NK cells) directly in whole blood using a combination of flow cytometry, imaging flow cytometry, cell sorting, and high resolution confocal microscopy. Platelet-derived EVs constituted the majority of circulating EVs and were preferentially associated with granulocytes and monocytes, while they scarcely interacted with lymphocytes. Further flow cytometric differentiation of monocyte subsets provided clear indications for a preferential association of platelet-derived EVs with intermediate (CD14⁺⁺CD16⁺) monocytes in whole blood.

Interferon Gamma Induces Reversible Metabolic Reprogramming of M1 Macrophages to Sustain Cell Viability and Pro-Inflammatory Activity

Classical activation of M1 macrophages with lipopolysaccharide (LPS) is associated with a metabolic switch from oxidative phosphorylation to glycolysis. However, the generalizability of such metabolic remodeling to other modes of M1 macrophage stimulation, e.g. type II interferons (IFNs) such as IFNγ, has remained unknown as has the functional significance of aerobic glycolysis during macrophage activation. Here we demonstrate that IFNγ induces a rapid activation of aerobic glycolysis followed by a reduction in oxidative phosphorylation in M1 macrophages. Elevated glycolytic flux sustains cell viability and inflammatory activity, while limiting reliance on mitochondrial oxidative metabolism. Adenosine triphosphate (ATP) distributed by aerobic glycolysis is critical for sustaining IFN-γ triggered JAK (Janus tyrosine kinase)-STAT-1 (Signal Transducer and Activator of Transcription 1) signaling with phosphorylation of the transcription factor STAT-1 as its signature trait. Inhibition of aerobic glycolysis not only blocks the M1 phenotype and pro-inflammatory cytokine/chemokine production in murine macrophages and also human monocytes/macrophages. These findings extend on the potential functional role of immuno-metabolism from LPS- to IFNγ-linked diseases such as atherosclerosis and autoimmune disease.

Procedures for leukocytes isolation from lymphoid tissues and consequences on immune endpoints used to evaluate fish immune status: A case study on roach (Rutilus rutilus)

The effects of two protocols (density gradient versus hypotonic lysis) used for leukocyte isolation from three major lymphoid tissue of fish (head-kidney, spleen and blood) were examined on some cell functional activities (tissue leucocytes distributions, phagocytosis, basal and burst oxidative activities) classically used to estimate the fish immune status. Experiments were conducted on roach (Rutilus rutilus), a cyprinid fish model often studied in different eco-physiological contexts (aquaculture, ecotoxicology …). All of immune endpoints were assessed either immediately after cell isolation or after a 12 h of incubation in order to observe if a post-isolation incubation may influence the leukocytes activities. Compared to the density gradient, hypotonic lysis is associated with granulocytes enrichments of cell suspensions. This is particularly true for leukocyte suspensions isolated from head kidney where granulocytes are naturally abundant. However, important variabilities in leukocyte distributions were observed in head kidney and spleen cells samples obtained by the use of hypotonic lysis for two incubation conditions used (no incubation or 12 h of incubation at 4 °C). The density gradient protocol leads to a transitory increase in basal ROS production in spleen lymphocytes and macrophages The blood leukocytes isolated by this same method exhibit high basal oxidative activities after 12 h of incubation at 4 °C and for the three leukocyte types (lymphocytes, monocytes and granulocytes). The hypotonic lysis is associated with an increase in PMA-induced ROS production especially in head kidney leukocytes. The increases in cell oxidative activities are consistent with increases in granulocyte proportions observed in leukocyte suspensions obtained by hypotonic lysis. Finally, the two protocols have no effect on leukocyte mortality and phagocytic activity. Within limits of our experimental conditions, the spleen is the organ whose leukocyte oxidative activities (stimulated or not) are only slightly influenced by the methods used for leukocyte isolation. This is also the case for the anterior kidney, but for this tissue, it is necessary to incubate the isolated cells for 12 h at 4 °C before functional analyses. Each of the two methodologies used has advantages and disadvantages. The hypotonic lysis allows to isolate a greater variety of leukocytes types whereas the density gradient used ensures a better stability of cells distributions over time. However, for the same fish species and for the same tissue, the method used to isolate leukocytes influences results and must be taken into consideration during acquired data analysis for evaluation of fish immune status.

Apolipoprotein L Expression Correlates with Neutrophil Cell Death in Critically Ill Patients

Delayed neutrophil apoptosis has been demonstrated in sepsis and may contribute to organ damage. It has recently been proposed that apolipoprotein L (ApoL) may be involved in programmed cell death, but the expression and functions of ApoLs in leukocytes (especially neutrophils) during sepsis and other inflammatory conditions are currently unknown. In this prospective observational study in a 36-bed university hospital medicosurgical intensive care unit (ICU), we included 78 adult ICU patients with (n = 41) or without (n = 37) sepsis and 47 healthy volunteers. We analyzed ApoL mRNA expression using quantitative polymerase chain reaction in whole blood leukocytes and protein expression in CD15 isolated neutrophils using Western blotting. Neutrophil apoptosis was assessed using the APO-BRDU method. Apolipoprotein L mRNA was downregulated in whole blood leukocytes and neutrophils in ICU patients compared with in healthy volunteers, and this effect translated at the protein level as indicated by Western blot analysis of neutrophils. There was a negative correlation between ApoL expression in neutrophils and C-reactive protein levels and a positive correlation between the number of apoptotic neutrophils and mRNA levels of ApoL1 and ApoL2. The degree of neutrophil apoptosis in critically ill patients is therefore correlated with modified expression profiles of ApoLs.

Administration of Rhodiola kirilowii Extracts during Mouse Pregnancy and Lactation Stimulates Innate but Not Adaptive Immunity of the Offspring

The use of antibiotics during pregnancy and lactation is associated with an increased risk of developmental disorders. One of the natural medicinal plants—Rhodiola kirilowii, widely used as an immunostimulant in adults—might be a good alternative to antibiotic treatment. The aim of present study was to assess whether daily oral administration of 20 mg/kg of Rhodiola kirilowii aqueous (RKW) or 50% hydroalcoholic (RKW-A) extracts affected hematological and immunological parameters of 6-week-old mouse progeny. There was no significant change in hematological parameters of blood with the exception of hemoglobin, which was significantly higher (about 4%) in RKW group. Offspring of mothers fed Rhodiola kirilowii extracts had increased percentage of granulocytes and decreased percentage of lymphocytes. These changes correlated with decreased percentage of CD3⁺/CD4⁺ T-cells (RKW and RKW-A), decrease of CD8⁺ cells, and increase percentage of NK cells in RKW group. In addition, both types of Rhodiola kirilowii extracts stimulated granulocyte phagocytosis and increased level of respiratory burst. In conclusion, the long-term supplementation of mouse mothers during pregnancy and lactation with RKW or RKW-A extracts affects the immune system of their progeny. These results should be taken into consideration before administration of Rhodiola kirilowii to pregnant and lactating women.

Macrophage migration inhibitory factor enhances Pseudomonas aeruginosa biofilm formation, potentially contributing to cystic fibrosis pathogenesis

Macrophage migration inhibitory factor (MIF) is a key proinflammatory mediator that we have previously shown to be associated with an aggressive clinical phenotype in cystic fibrosis. It possesses unique tautomerase enzymatic activity. However, to date, no human-derived substrate has been identified that has the capacity to interact with this cytokine's unique tautomerase activity. This led us to hypothesize that MIF may have the capacity to interact with external substrates. We describe for the first time how Pseudomonas aeruginosa can utilize human recombinant MIF (rMIF) to significantly (P < 0.01) enhance its endogenous biofilm formation. Our in vivo studies demonstrate that utilizing a small-molecular-weight inhibitor targeting MIF's tautomerase activity (SCD-19) significantly reduces the inflammatory response in a murine pulmonary chronic P. aeruginosa model. In addition, we show that in in vitro experiments, pretreatment of P. aeruginosa with rMIF is associated with reduced bacterial killing by tobramycin. Our novel findings support the concept of an anti-MIF strategy that targets this enzymatic activity as a potential future antibacterial therapeutic approach.-Tynan, A., Mawhinney, L., Armstrong, M. E., O'Reilly, C., Kennedy, S., Caraher, E., Jülicher, K., O'Dwyer, D., Maher, L., Schaffer, K., Fabre, A., McKone, E. F., Leng, L., Bucala, R., Bernhagen, J., Cooke, G., Donnelly, S. C. Macrophage migration inhibitory factor enhances Pseudomonas aeruginosa biofilm formation, potentially contributing to cystic fibrosis pathogenesis.