Adult Monocytes Research Articles

Deep Immune and RNA Profiling Revealed Distinct Circulating CD163+ Monocytes in Diabetes-Related Complications.

CD163, a scavenger receptor with anti-inflammatory function expressed exclusively on monocytes/macrophages, is dysregulated in cases of diabetes complications. This study aimed to characterize circulating CD163+ monocytes in the presence (D+Comps) or absence (D-Comps) of diabetes-related complications. RNA-sequencing and mass cytometry were conducted on CD163+ monocytes in adults with long-duration diabetes and D+Comps or D-Comps. Out of 10,868 differentially expressed genes identified between D+Comps and D-Comps, 885 were up-regulated and 190 were down-regulated with a ≥ 1.5-fold change. In D+Comps, 'regulation of centrosome cycle' genes were enriched 6.7-fold compared to the reference genome. MIR27A, MIR3648-1, and MIR23A, the most up-regulated and CD200R1, the most down-regulated gene, were detected in D+Comps from the list of 75 'genes of interest'. CD163+ monocytes in D+Comps had a low proportion of recruitment markers CCR5, CD11b, CD11c, CD31, and immune regulation markers CD39 and CD86. A gene-protein network identified down-regulated TLR4 and CD11b as 'hub-nodes'. In conclusion, this study reports novel insights into CD163+ monocyte dysregulation in diabetes-related complications. Enriched centrosome cycle genes and up-regulated miRNAs linked to apoptosis, coupled with down-regulated monocyte activation, recruitment, and immune regulation, suggest functionally distinct CD163+ monocytes in cases of diabetes complications. Further investigation is needed to confirm their role in diabetes-related tissue damage.

Human Microglia-Like Cells Differentiated from Monocytes with GM-CSF and IL-34 Show Phagocytosis of α-Synuclein Aggregates and C/EBPβ-Dependent Proinflammatory Activation.

Microglia, the main resident immune cells in the central nervous system, are implicated in the pathogenesis of various neurological disorders. Much of our knowledge on microglial biology was obtained using rodent microglial cultures. To understand the role of microglia in human disease, reliable in vitro models of human microglia are necessary. Monocyte-derived microglia-like cells (MDMi) are a promising approach. This study aimed to characterize MDMi cells generated from adult human monocytes using granulocyte-macrophage colony-stimulating factor and interleukin-34. To this end, 49 independent cultures of MDMI were prepared, and various methodological and functional studies were performed. We show that with this protocol, adult human monocytes develop into microglia-like cells, a coating is unnecessary, and high cell density seeding is preferable. When compared to monocytes, MDMi upregulate the expression of many, but not all, microglial markers, indicating that, although these cells display a microglia-like phenotype, they cannot be considered bona fide human microglia. At the functional level, MDMi phagocytose α-synuclein aggregates and responds to lipopolysaccharide (LPS) by nuclear translocation of the transcription factor nuclear factor-kappaB (NFkappaB) and the upregulation of proinflammatory genes. Finally, a long-lasting silencing of the transcription factor CCAAT/enhancer protein β (C/EBPβ) was achieved by small interfering RNA, resulting in the subsequent downregulation of proinflammatory genes. This supports the hypothesis that C/EBPβ plays a key role in proinflammatory gene program activation in human microglia. Altogether, this study sheds new light on the properties of MDMi cells and supports these cells as a promising in vitro model for studying adult human microglia-like cells.

Analysis of genes related to female bone peak and osteoporosis based on bioinformatics

To explore and verify the genes related to female peak bone mass(PBM) and osteoporosis (OP) based on bioinformatics. Using GEO data, DNA microarray technology to conduct genome-wide analysis of adult female monocytes with high and low PBM. Cluster analysis, GO enrichment and KEGG analysis were used to analyze the differential genes, and the interaction network of differential genes was further analyzed. OP rat model was established and femur neck tissue staining was performed to further verify the expression of differential genes. A total of 283 genes were obtained by differential gene screening. Compared with the high PBM samples, 135 genes were up-regulated and 148 genes were down-regulated in the low PBM samples. A total of 7 pathways and 12 differential genes were enriched, and there were differences in the expression of several genes involved in mineral absorption and transport, cellular immunity and other aspects. Among them, voltage-gated Ca2+ channel 1.3(CaV1.3) encoded by CACNA1D gene was significantly enhanced in the femoral neck tissue of OP rat model. The above results suggest that the difference in the expression level of CaV1.3 gene may lead to the occurrence of OP in women with low PBM, which provides us with a potential target for the prevention and treatment of OP.

The nature of the stimulant differentially impacts the innate memory response of monocytes to Mycobacterium tuberculosis

Abstract Innate immune cells, such as monocytes, can generate a non-specific ‘memory’ response (a.k.a. trained immunity) upon stimulation with an antigen/bacterium (e.g., LPS or BCG), which confers heterologous protection against another infectious agent. However, the association between the nature of stimulants and the corresponding immune correlate of trained immunity is not fully understood. Similarly, the response of macrophages “trained” by various stimulants to subsequent infection by different clinical Mycobacterium tuberculosis(Mtb) strains remains unknown. Here, we report the trained immunity profile of the blood-derived monocytes (BDM) of BCG-vaccinated adults and monocytic THP-1 cells after stimulation with BCG, LPS, Purified Protein Derivative (PPD), heat-killed MtbHN878 or MtbCDC1551 strains. The response of monocytes trained by these agents to subsequent infection with clinical Mtb isolates HN878 and CDC1551, which differ in their virulence potential, was evaluated using standard molecular and cellular immunologic assays. The BCG- and LPS-trained macrophages produced higher proinflammatory, antimicrobial responses, and autophagy induction than unstimulated, PPD, HK-HN878, or CDC1551-stimulated cells. The HN878-infected trained THP-1 cells elicited a more robust inflammatory response than the CDC1551 infection. A significantly reduced intracellular Mtb growth was noted in the BCG and LPS-trained THP-1 cells, which was augmented by adding rapamycin, an autophagy inducer. A similar immunological response was noted in the BDM of BCG-vaccinated adults infected with these Mtb strains. Thus, the nature of the stimulant affects the macrophages’ trained immunity profile and its response to Mtb infection. Supported by grants from NIH (R01 AI161822) and the Bill and Melinda Gates Foundation (INV-009099; formerly OPP1157210).

Abstract 380: Adult But Not Neonatal Platelets Promotes Monocyte Trafficking In Neonatal Mice

Background: Platelet transfusions are sometimes given to thrombocytopenic neonates with the hope of reducing the bleeding risk, however, there is little clinical data to support this practice and platelet transfusions may increase the bleeding risk or lead to adverse complications. Our group previously reported that fetal platelets expressed lower levels of immune related mRNA compared to adult platelets. In this study we focused on the effects of adult versus neonatal platelets on monocyte immune functions that may have an impact on neonatal immune function and transfusion complications. Methods: Platelets and bone marrow isolated monocytes were co-cultured and monocyte phenotypes determined by RNA-seq and flow cytometry. An in vivo model of platelet transfusion in neonatal thrombocytopenic mice was used in which platelet deficient thrombopoietin receptor mutant mice (TPOR -/- ) were transfused with adult or P7 platelets and monocyte phenotypes and trafficking were determined. Results: Adult and neonatal platelets had differential immune molecule expression, including Selp (P-selectin). Monocytes incubated with adult or neonatal mouse platelets had similar inflammatory (Ly6C hi ), but different trafficking phenotypes, as defined by CCR2 and CCR5 surface expression. Blocking P-selectin-PSGL-1 interaction, monocytes limited the adult platelet induced monocyte trafficking phenotype, as well as adult platelet induced monocyte migration in vitro . Similar results were seen in vivo, when thrombocytopenic neonatal mice were transfused with adult or P7 platelets; adult platelets increased monocyte CCR2 and CCR5 as well as monocyte chemokine migration, while P7 platelets did not. Conclusion: These data provide comparative insights into adult and neonatal platelet transfusion regulated monocyte functions.

Transfusion of Adult, but Not Neonatal, Platelets Promotes Monocyte Trafficking in Neonatal Mice.

Thrombocytopenia is common in preterm neonates. Platelet transfusions are sometimes given to thrombocytopenic neonates with the hope of reducing the bleeding risk, however, there are little clinical data to support this practice, and platelet transfusions may increase the bleeding risk or lead to adverse complications. Our group previously reported that fetal platelets expressed lower levels of immune-related mRNA compared with adult platelets. In this study, we focused on the effects of adult versus neonatal platelets on monocyte immune functions that may have an impact on neonatal immune function and transfusion complications. Using RNA sequencing of postnatal day 7 and adult platelets, we determined age-dependent platelet gene expression. Platelets and naive bone marrow-isolated monocytes were cocultured and monocyte phenotypes determined by RNA sequencing and flow cytometry. An in vivo model of platelet transfusion in neonatal thrombocytopenic mice was used in which platelet-deficient TPOR (thrombopoietin receptor) mutant mice were transfused with adult or postnatal day 7 platelets and monocyte phenotypes and trafficking were determined. Adult and neonatal platelets had differential immune molecule expression, including Selp. Monocytes incubated with adult or neonatal mouse platelets had similar inflammatory (Ly6Chi) but different trafficking phenotypes, as defined by CCR2 and CCR5 mRNA and surface expression. Blocking P-sel (P-selectin) interactions with its PSGL-1 (P-sel glycoprotein ligand-1) receptor on monocytes limited the adult platelet-induced monocyte trafficking phenotype, as well as adult platelet-induced monocyte migration in vitro. Similar results were seen in vivo, when thrombocytopenic neonatal mice were transfused with adult or postnatal day 7 platelets; adult platelets increased monocyte CCR2 and CCR5, as well as monocyte chemokine migration, whereas postnatal day 7 platelets did not. These data provide comparative insights into adult and neonatal platelet transfusion-regulated monocyte functions. The transfusion of adult platelets to neonatal mice was associated with an acute inflammatory and trafficking monocyte phenotype that was platelet P-sel dependent and may have an impact on complications associated with neonatal platelet transfusions.

Proteome analysis of monocytes implicates altered mitochondrial biology in adults reporting adverse childhood experiences

The experience of adversity in childhood has been associated with poor health outcomes in adulthood. In search of the biological mechanisms underlying these effects, research so far focused on alterations of DNA methylation or shifts in transcriptomic profiles. The level of protein, however, has been largely neglected. We utilized mass spectrometry to investigate the proteome of CD14+ monocytes in healthy adults reporting childhood adversity and a control group before and after psychosocial stress exposure. Particular proteins involved in (i) immune processes, such as neutrophil-related proteins, (ii) protein metabolism, or (iii) proteins related to mitochondrial biology, such as those involved in energy production processes, were upregulated in participants reporting exposure to adversity in childhood. This functional triad was further corroborated by protein interaction- and co-expression analyses, was independent of stress exposure, i.e. observed at both pre- and post-stress time points, and became evident especially in females. In line with the mitochondrial allostatic load model, our findings provide evidence for the long-term effects of childhood adversity on mitochondrial biology.

Phenotypic and functional alterations of monocyte subsets with aging

BackgroundIt has been widely accepted that monocytes are one of the central mediators contributing to inflammaging. However, it remains unclear whether aged monocytes, similar to aged T cells, have characteristics of hyperactivation and increased expression of co-inhibitory molecules.MethodsPeripheral blood mononuclear cells (PBMCs) were isolated from young (21–40 years old), middle-aged (41–60 years old), and older human subjects (> 60 years old). Flow cytometry was used to monitor changes in the expression of surface molecules of monocyte subsets and cytokine-producing capacity.ResultsWe observed increased tumor necrosis factor-α: TNF-α and decreased interleukin-6 (IL-6) production in monocytes from older adults compared with young and middle-aged adults. Older adults had a greater percentage of intermediate and non-classical monocyte subsets, along with increased levels of the immune activation markers human leukocyte antigen-DR (HLA-DR), and adhesion molecules cluster of differentiation molecule 11b (CD11b) and L-selectin (CD62L). Furthermore, we observed increased C–C motif chemokine receptor 2 (CCR2) expression on classical monocytes and decreased C-X3-C motif chemokine receptor 1 (CX3CR1) expression on non-classical monocytes in older adult subjects. The expression of co-inhibitory receptors was reduced on monocyte subsets in older adults.ConclusionsCirculating monocytes in older adults exhibit increased expression of activation, adhesion, and migration markers, but decreased expression of co-inhibitory molecules.

A mouse infection model and long-term lymphatic endothelium co-culture system to evaluate drugs against adult Brugia malayi.

The development of new drugs targeting adult-stage lymphatic filarial nematodes is hindered by the lack of a robust long-term in vitro culture model. Testing potential direct-acting and anti-Wolbachia therapeutic candidates against adult lymphatic filariae in vitro requires their propagation via chronic infection of gerbils. We evaluated Brugia malayi parasite burden data from male Mongolian gerbils compared with two immune-deficient mouse strains highly susceptible to B. malayi: CB.17 Severe-Combined Immmuno-Deficient (SCID) and interleukin-4 receptor alpha, interleukin-5 double knockout (IL-4Rα-/-IL-5-/-) mice. Adult worms generated in IL-4Rα-/-IL-5-/- mice were tested with different feeder cells (human embryonic kidney cells, human adult dermal lymphatic endothelial cells and human THP-1 monocyte differentiated macrophages) and comparative cell-free conditions to optimise and validate a long-term in vitro culture system. Cultured parasites were compared against those isolated from mice using motility scoring, metabolic viability assay (MTT), ex vivo microfilariae release assay and Wolbachia content by qPCR. A selected culture system was validated as a drug screen using reference anti-Wolbachia (doxycycline, ABBV-4083 / flubentylosin) or direct-acting compounds (flubendazole, suramin). BALB/c IL-4Rα-/-IL-5-/- or CB.17 SCID mice were superior to Mongolian gerbils in generating adult worms and supporting in vivo persistence for periods of up to 52 weeks. Adult females retrieved from BALB/c IL-4Rα-/-IL-5-/- mice could be cultured for up to 21 days in the presence of a lymphatic endothelial cell co-culture system with comparable motility, metabolic activity and Wolbachia titres to those maintained in vivo. Drug studies confirmed significant Wolbachia depletions or direct macrofilaricidal activities could be discerned when female B. malayi were cultured for 14 days. We therefore demonstrate a novel methodology to generate adult B. malayi in vivo and accurately evaluate drug efficacy ex vivo which may be adopted for drug screening with the dual benefit of reducing overall animal use and improving anti-filarial drug development.

Biology of resident tissue macrophages.

Although best known for their phagocytic and immunological functions, macrophages have increasingly been recognised as key players in the development, homeostasis and regeneration of their host tissues. Early during development, macrophages infiltrate and colonise all tissues within the body, developing symbiotically with their host tissues and acquiring unique functional adaptations based on the tissue microenvironment. These embryonic resident tissue macrophages (RTMs) are ontogenically distinct from the later adult bone marrow-derived monocytes, and in some tissues are self-maintained independently of general circulation at a steady state. In this article, we briefly discuss the ontogeny, maintenance and unique tissue adaptions of RTMs focusing on microglia, Kupffer cells, Langerhans cells, intestinal macrophages, cardiac macrophages and tumour-associated macrophages, and highlight their role in development, homeostasis and dysfunction.

Dengue NS1 induces phospholipase A2 enzyme activity, prostaglandins, and inflammatory cytokines in monocytes

IntroductionDengue virus (DENV) NS1 is a non-structural secretory protein associated with severe disease and known to cause vascular leak leading to dengue haemorrhagic fever (DHF). As phospholipases A2 (PLA2) enzymes, platelet activating factor, and leukotrienes are elevated in dengue, we sought to investigate whether NS1 potentially contributes to disease pathogenesis by inducing PLA2s. MethodsTHP-1 cells and primary human monocytes of healthy adults (n = 6) were co-cultured with DENV1 NS1, LPS and media alone. The latter two were used as positive and negative controls. The cell culture supernatants and lysates were harvested at 12 and 24 h and the activity of secretory and cytoplasmic PLA2, prostaglandins (PGE2 and PGD2) were measured by ELISA and cytokines levels were measured using a magnetic Luminex assay. Expression of PLA2G4A, PLA2G2A, PLA2G5, PLA2G10, PLA2G7, GAPDH, NLRP3 and DDX58 genes were assessed using quantitative RT-PCR. ResultscPLA2 (p = 0.005), sPLA2 (p = 0.04), PGE2 metabolite (p = 0.02) and PGD2 metabolite (p = 0.04) levels were significantly higher at 12 h in monocytes co-cultured with NS1. Levels of IP-10 (p = 0.005) and IL-10 (p = 0.009) was significantly higher at 24 h, whereas IFNα level was significantly higher (p = 0.013) only at 12 h. IL-1β (p = 0.028 and p = 0.031) and TNFα (p = 0.007 and p = 0.011) showed significantly higher levels at both time points. At 12 h significant upregulation of PLA2G4A (p < 0.0001) was seen, whereas PLA2G7 (p = <0.0001), NLRP3 (p = 0.0009) and DDX58 (p = 0.0056) were significantly downregulated. This pattern changed at 24 h with PLA2G4A (p = 0.0069) showing a marked downregulation and PLA2G7, DDX58 and NLRP3 showing an upregulation, although not significant. ConclusionDengue NS1 induces the production of PLA2 enzymes, prostaglandins and inflammatory cytokines from primary human monocytes, which could play a role in vascular leak in dengue.

Group B streptococci infection model shows decreased regulatory capacity of cord blood cells

BackgroundSepsis is one of the leading causes of morbidity and mortality in the neonatal period. Compared to adults, neonates are more susceptible to infections, especially to systemic infections with Group B Streptococcus (GBS). Furthermore, neonates show defects in terminating inflammation. The immunological causes for the increased susceptibility to infection and the prolonged inflammatory response are still incompletely understood.MethodsIn the present study, we aimed to investigate the reaction of cord blood mononuclear cells (MNC) to stimulation with GBS in comparison to that of MNC from adult blood with focus on the proliferative response in an in vitro infection model with heat-inactivated GBS.ResultsWe demonstrate that after stimulation with GBS the proliferation of T cells from adult blood strongly decreased, while the proliferation of cord blood T cells remained unchanged. This effect could be traced back to a transformation of adult monocytes, but not cord blood monocytes, to a suppressive phenotype with increased expression of the co-inhibitory molecule programmed death ligand 1 (PD-L1).ConclusionsThese results point towards an increased inflammatory capacity of neonatal MNC after stimulation with GBS. Targeting the prolonged inflammatory response of neonatal immune cells may be a strategy to prevent complications of neonatal infections.ImpactNeonatal sepsis often leads to post-inflammatory complications.Causes for sustained inflammation in neonates are incompletely understood.We show that cord blood T cells exhibited increased proliferative capacity after stimulation with group B streptococci (GBS) in comparison to adult T cells.Adult monocytes but not cord blood monocytes acquired suppressive activity and expressed increased levels of PD-L1 after GBS stimulation.Increased proliferative capacity of neonatal T cells and decreased suppressive activity of neonatal monocytes during GBS infection may contribute to prolonged inflammation and development of post-inflammatory diseases in newborns.

Four weeks of spice consumption lowers plasma proinflammatory cytokines and alters the function of monocytes in adults at risk of cardiometabolic disease: secondary outcome analysis in a 3-period, randomized, crossover, controlled feeding trial

Numerous studies demonstrate acute anti-inflammatory properties of individual spices, but none have examined the effect of longer-term consumption of a spice blend incorporated in a meal. We investigated the effect of longer-term spice consumption on inflammatory cytokines and monocyte subsets [classical (CM), intermediate (IM), nonclassical (NCM)] in adults at risk of cardiometabolic disease. A 3-period, randomized, crossover, controlled feeding trial was conducted. Participants (n = 71 recruited; n = 63 completed) randomly consumed diets differing in terms of the quantity of spices: 0.547 g (low-dose spice diet; LSD), 3.285 g (medium-dose spice diet; MSD), or 6.571 g (high-dose spice diet; HSD) · d-1 · 2100 kcal-1, for 4 wk with a ≥2-wk washout between diets. At baseline and after each diet period, proinflammatory cytokines (IL-1β, IL-6, IL-8, monocyte chemoattractant protein-1, and TNF-α) in plasma and LPS-stimulated peripheral blood mononuclear cell culture supernatants, and the phenotype and function of monocyte subsets, were measured in fasted participants. Postprandial proinflammatory cytokines also were quantified at baseline by consumption of a low-spice-dose test meal, and after each diet period by consumption of a test meal containing a spice dose corresponding to daily spice consumption during the preceding 4-wk diet period. Fasting plasma IL-6 was reduced (mean ± SEM: -118.26 ± 50.63 fg/mL; P < 0.05) after MSD compared with baseline. Postprandial plasma IL-1β, IL-8, and TNF-α were lower (mean ± SEM : -9.47 ± 2.70 fg/mL, -0.20 ± 0.05 pg/mL, and -33.28 ± 12.35 fg/mL, respectively) after MSD compared with LSD (main diet effect; P < 0.05). CM adherence was reduced (mean ± SEM: -0.86 ± 0.34; P = 0.034) after HSD compared with LSD. IM migration was reduced after MSD and HSD compared with LSD (mean ± SEM: -0.39 ± 0.09 and -0.56 ± 0.14, respectively; P < 0.05). Four weeks of MSD consumption reduced fasting plasma IL-6 and postprandial plasma IL-1β, IL-8, and TNF-α as well as altering monocyte function.This trial was registered at clinicaltrials.gov as NCT03064932.

Aging does not affect calcium response to CCL2 and LPS in human monocytes

Monocytes play important roles in anti-microbial and anti-viral responses and chronic inflammatory diseases. Monocytes' functions are altered by aging. We investigated age-changes in calcium (Ca2+) response to CCL2 and LPS in human monocytes. CCL2 and LPS induced a slow increase of the cytosolic Ca2+ level, with a maximum response at ∼360 s and ∼300 s, respectively, in monocytes of young and older adults. No difference was observed in the magnitude and in the Ca2+ kinetic with both stimuli. Furthermore, store-operated Ca2+ entry and plasma membrane expression of ORAI1 showed no difference between both groups. In summary, monocytes from older adults maintained the capacity to mobilize calcium as their counterparts in young adults suggesting that the mechanisms underlying the dysfunctions in monocytes in aging might not involve alterations in Ca2+ flow through the plasma membrane.

Elevated circulating CD16+ monocytes and TLR4+ monocytes in older adults with multiple cardiometabolic disease risk factors

We endeavored to examine relationships between circulating monocyte phenotype and cardio-metabolic disease risk, in healthy, older adults. We performed a secondary data analysis on men and women, 55–75 yr, who were assigned to groups based on cardio-metabolic risk factors other than age. Subject in the low risk group (n = 16, 12 females) had fewer than three risk factors. Subjects in the elevated risk group (n = 29, 19 females) had three or more risk factors. Along with baseline screening for fitness and body composition, resting blood samples were assessed for markers of inflammation including: monocyte phenotype (inflammatory monocytes), monocyte cell-surface TLR4 expression, and serum C-reactive protein. The low risk group had a smaller (19.3% difference; p < 0.0001) waist circumference and lower body fat weight (36.3%; p < 0.0001), but higher V̇02max (45.5%; p = 0.0019). There were no mean differences (p > 0.05) between the low and elevated risk groups for BMI, serum cholesterol, fasting glucose, or leg press 1RM. The low risk group had lower CRP (114.7%, p = 0.0002), higher CD14+CD16− (classical) monocytes (6.7%; p = 0.0231) and fewer CD14+CD16+ (inflammatory) monocytes (46.2%; p = 0.0243) than the elevated risk group. The low risk group also had a lower percentage of CD14+CD16− monocytes that were positive for TLR4 (14.0%; p = 0.0328). Older men and women with fewer cardio-metabolic risk factors had lower serum and cellular markers of inflammation and higher aerobic capacity.

Human Newborn Monocytes Demonstrate Distinct BCG-Induced Primary and Trained Innate Cytokine Production and Metabolic Activation In Vitro.

BackgroundNewborns exhibit distinct immune responses and are at high risk of infection. Neonatal immunization with BCG, the live attenuated vaccine against tuberculosis (TB), is associated with broad protection against a range of unrelated pathogens, possibly reflecting vaccine-induced training of innate immune cells (“innate memory”). However, little is known regarding the impact of age on BCG-induced innate responses.ObjectiveEstablish an age-specific human monocyte in vitro training platform to characterize and compare BCG-induced primary and memory cytokine responses and immunometabolic shifts.Design/MethodsHuman neonatal and adult CD33-selected monocytes were stimulated for 24h with RPMI (control) or BCG (Danish strain) in 10% autologous serum, washed and cultured for 5 additional days, prior to re-stimulation with the TLR4 agonist LPS for another 24h. Supernatants were collected at Day 1 (D1) to measure primary innate responses and at Day 7 (D7) to assess memory innate responses by ELISA and multiplex cytokine and chemokine assays. Lactate, a signature metabolite increased during trained immunity, was measured by colorimetric assay.ResultsCytokine production by human monocytes differed significantly by age at D1 (primary, BCG 1:750 and 1:100 vol/vol, p<0.0001) and D7 (innate memory response, BCG 1:100 vol/vol, p<0.05). Compared to RPMI control, newborn monocytes demonstrated greater TNF (1:100, 1:10 vol/vol, p<0.01) and IL-12p40 (1:100 vol/vol, p<0.05) production than adult monocytes (1:100, p<0.05). At D7, while BCG-trained adult monocytes, as previously reported, demonstrated enhanced LPS-induced TNF production, BCG-trained newborn monocytes demonstrated tolerization, as evidenced by significantly diminished subsequent LPS-induced TNF (RPMI vs. BCG 1:10, p <0.01), IL-10 and CCL5 production (p<0.05). With the exception of IL-1RA production by newborn monocytes, BCG-induced monocyte production of D1 cytokines/chemokines was inversely correlated with D7 LPS-induced TNF in both age groups (p<0.0001). Compared to BCG-trained adult monocytes, newborn monocytes demonstrated markedly impaired BCG-induced production of lactate, a metabolite implicated in immune training in adults.ConclusionsBCG-induced human monocyte primary- and memory-innate cytokine responses were age-dependent and accompanied by distinct immunometabolic shifts that impact both glycolysis and training. Our results suggest that immune ontogeny may shape innate responses to live attenuated vaccines, suggesting age-specific approaches to leverage innate training for broad protection against infection.

Reduce inflammatory cytokine profile in subspecialized neonatal APCs responding to viral pathogen-associated molecular patterns has implications for vaccine design

Abstract Young infants experience a higher burden of morbidity and mortality due to respiratory viruses and incomplete understanding of distinct age-dependent immune responses limits precision vaccine design in this age group. Subspecialized DCs and monocytes have evolved to detect viral pathogen-associated molecular patterns (PAMPs) to defend against infection and drive the adaptive immune response. We hypothesized that viral PAMPs and IFN I differentially activate neonatal DC and monocyte subsets resulting in age-dependent cytokine responses. To test this hypothesis, we isolated mononuclear cells from cord blood (CBMC) and peripheral blood (PBMC) and analyzed their responses through novel multiparameter spectral flow cytometric assays to PAMPs mimicking viral RNA. We discovered that conventional (c) DC2 in early life respond to Resiquimod (R848, TLR7/8 agonist) with similar upregulation of activation markers (CD80/86, CD70, CD38) and expression of TNFa, but more IL-6 compared to their adult counterparts. Unexpectedly, R848 and polyinosinic: polycytidylic acid (PIC, TLR3 agonist) resulted in significant CD25 upregulation by adult cDC2 and monocytes, in contrast to neonatal cells, suggesting decreased sensitivity to IL-2. In addition, in response to the antiviral type I IFN, cDC2 and monocytes from adults produced higher levels of CXCL10. Together our data suggest that neonatal DCs and monocytes have distinct functional responses to viral PAMPs, R848 and PIC, exhibiting reduced proinflammatory cytokine profiles. This may limit the potential for cytokine storm, but also delay the responsiveness to viral infections and vaccines that implement viral RNA in their design.

The Warburg Effect Occurs Rapidly in Stimulated Human Adult but Not Umbilical Cord Blood Derived Macrophages.

The Warburg effect, defined as increased glycolysis and decreased oxidative phosphorylation, occurs in murine macrophages following LPS stimulation and is required for activation. There are differences between human and murine macrophage metabolic responses to stimulation, with peak metabolite concentrations occurring earlier in humans than mice. Complex changes occur in the human immune system with age, resulting in the very young and the very old being more susceptible to infections. Anti-bacterial immune responses in umbilical cord immune cells are considered deficient but there is a paucity of data on the role that metabolism plays. We hypothesized that metabolic responses in human macrophages occur early during activation. In addition, we hypothesized that umbilical cord derived macrophages have an altered immunometabolic response compared with adult macrophages. We demonstrate that adult and cord blood monocyte derived macrophages (MDM) immediately increase glycolysis in response to stimulation with LPS or Mycobacterium tuberculosis (Mtb), however only adult MDM decrease oxidative phosphorylation. At 24 hours post stimulation, glycolysis remains elevated in both adult and cord blood MDM, oxidative phosphorylation remains unchanged in the cord blood MDM and has normalized in the adult MDM stimulated with Mtb. However, LPS stimulated adult MDM have increased oxidative phosphorylation at 24 hours, illustrating differences in metabolic responses to different stimuli, time-dependent variation in responses and differences in macrophage metabolism in adults compared with umbilical cord blood. We compared the phenotype and function of macrophages derived from adult or cord blood. Cord blood MDM secreted less TNF following Mtb stimulation and more IL-6 following LPS stimulation compared with adult MDM. Our findings demonstrate that whilst cord blood MDM exhibit an immediate increase in glycolytic flux in response to stimulation, similar to adult MDM, cord blood MDM do not concomitantly decrease oxygen consumption. This indicates that adult macrophages shift to Warburg metabolism immediately after stimulation, but cord blood macrophages do not. Understanding the differences in the metabolic profiles of macrophages over a human lifetime will enable the translation of immunometabolism into effective immuno-supportive therapies that could potentially be targeted at vulnerable populations, such as the very old and the very young.

Plasmodium falciparum malaria drives epigenetic reprogramming of human monocytes toward a regulatory phenotype.

In malaria-naïve children and adults, Plasmodium falciparum-infected red blood cells (Pf-iRBCs) trigger fever and other symptoms of systemic inflammation. However, in endemic areas where individuals experience repeated Pf infections over many years, the risk of Pf-iRBC-triggered inflammatory symptoms decreases with cumulative Pf exposure. The molecular mechanisms underlying these clinical observations remain unclear. Age-stratified analyses of uninfected, asymptomatic Malian individuals before the malaria season revealed that monocytes of adults produced lower levels of inflammatory cytokines (IL-1β, IL-6 and TNF) in response to Pf-iRBC stimulation compared to monocytes of Malian children and malaria-naïve U.S. adults. Moreover, monocytes of Malian children produced lower levels of IL-1β and IL-6 following Pf-iRBC stimulation compared to 4–6-month-old infants. Accordingly, monocytes of Malian adults produced more IL-10 and expressed higher levels of the regulatory molecules CD163, CD206, Arginase-1 and TGM2. These observations were recapitulated in an in vitro system of monocyte to macrophage differentiation wherein macrophages re-exposed to Pf-iRBCs exhibited attenuated inflammatory cytokine responses and a corresponding decrease in the epigenetic marker of active gene transcription, H3K4me3, at inflammatory cytokine gene loci. Together these data indicate that Pf induces epigenetic reprogramming of monocytes/macrophages toward a regulatory phenotype that attenuates inflammatory responses during subsequent Pf exposure.Trial Registration: ClinicalTrials.gov NCT01322581.

Human CD36hi monocytes induce Foxp3+ CD25+ T cells with regulatory functions from CD4 and CD8 subsets.

The fetal and neonatal immune systems are uniquely poised to generate tolerance to self, maternal and environmental antigens encountered in the womb and shortly after birth. However, the tolerogenic nature of fetal and neonatal immunity can be detrimental in the context of pathogens, leading to overwhelming bacterial infections or chronic viral infections. A variety of mechanisms contribute to fetal and neonatal tolerance, including a propensity to generate Foxp3+ regulatory T cells (Treg cells). However, the mechanism(s) of fetal Foxp3+ T-cell differentiation, the specific antigen-presenting cells required and factors that inhibit Treg generation after the neonatal period are poorly understood. Here, we demonstrate that a subset of CD14+ monocytes expressing the scavenger molecule, CD36, can generate CD4+ and CD8+ T cells that coexpress Foxp3 and T-bet from both umbilical cord blood. These Foxp3+ T-bet+ T cells potently suppress T-cell proliferation and ameliorate xenogeneic graft-versus-host disease. CD14+ CD36+ monocytes provide known Treg-inducing signals: membrane-bound transforming growth factor-beta and retinoic acid. Unexpectedly, adult peripheral blood monocytes are also capable of inducing Foxp3+ T cells from both cord blood and adult peripheral naïve T cells. The induction of Foxp3+ T cells in umbilical cord blood by monocytes was inhibited by the lymphoid fraction of adult peripheral blood cells. These studies highlight a novel immunoregulatory role of monocytes and suggest that antigen presentation by CD36hi monocytes may contribute to the peripheral development of Foxp3+ T-bet+ T cells with regulatory functions in both neonates and adults.