Enumeration of human peripheral blood dendritic cells throughout the life

Functional Heterogeneity of Umbilical Cord Blood Monocyte-Derived Dendritic Cells

Human umbilical cord blood (UCB) represents a unique resource for hematopoietic stem cell transplantation for children and patients lacking suitable donors. UCB harbors a diverse set of leukocytes such as professional APCs, including monocytes, that could act as a novel source for cellular therapies. However, the immunological properties of UCB monocytes and monocyte-derived dendritic cells (MoDCs) are not fully characterized. In this study, we characterized the phenotype and functions of UCB-MoDCs to gauge their potential for future applications. UCB exhibited higher frequencies of platelets and lymphocytes as well as lower frequencies of neutrophils in comparison with adult whole blood. Leukocyte subset evaluation revealed significantly lower frequencies of granulocytes, NK cells, and CD14+CD16- monocytes. Surface marker evaluation revealed significantly lower rates of costimulatory molecules CD80 and CD83 while chemokine receptors CCR7 and CXCR4, as well as markers for Ag presentation, were similarly expressed. UCB-MoDCs were sensitive to TLR1-9 stimulation and presented quantitative differences in the release of proinflammatory cytokines. UCB-MoDCs presented functional CCR7-, CXCR4-, and CCR5-associated migratory behavior as well as adequate receptor- and micropinocytosis-mediated Ag uptake. When cocultured with allogeneic T lymphocytes, UCB-MoDCs induced weak CD4+ T lymphocyte proliferation, CD71 expression, and release of IFN-γ and IL-2. Taken together, UCB-MoDCs present potentially advantageous properties for future medical applications.

Stat5b/Ezh2 axis governs high PD-L1 expressing tolerogenic dendritic cell subset in autoimmune diabetes

Dendritic cells (DCs) are specialized antigen-presenting cells that play an important role in inducing and maintaining immune tolerance. The altered distribution and/or function of DCs contributes to defective tolerance in autoimmune diseases such as type 1 diabetes (T1D). In human T1D and in NOD mouse models, DCs share some defects and are often described as less tolerogenic and excessively immunogenic. In the NOD mouse model, the autoimmune response is associated with a defect in the Stat5b signaling pathway. We have reported that expressing a constitutively active form of Stat5b in DCs of transgenic NOD mice (NOD.Stat5b-CA), re-established their tolerogenic function, restored autoimmune tolerance and conferred protection from diabetes. However, the role and molecular mechanisms of Stat5b signaling in regulating splenic conventional DCs tolerogenic signature remained unclear. In this study, we reported that, compared to immunogenic splenic DCs of NOD, splenic DCs of NOD.Stat5b-CA mice exhibited a tolerogenic profile marked by elevated PD-L1 and PD-L2 expression, reduced pro-inflammatory cytokine production, increased frequency of the cDC2 subset and decreased frequency of the cDC1 subset. This tolerogenic profile was associated with increased Ezh2 and IRF4 but decreased IRF8 expression. We also found an upregulation of PD-L1 in the cDC1 subset and high PD-L1 and PD-L2 expression in cDC2 of NOD.Stat5b-CA mice. Mechanistically, we demonstrated that Ezh2 plays an important role in the maintenance of high PD-L1 expression in cDC1 and cDC2 subsets and that Ezh2 inhibition resulted in PD-L1 but not PD-L2 downregulation which was more drastic in the cDC2 subset. Additionally, Ezh2 inhibition severely reduced the cDC2 subset and increased the cDC1 subset and Stat5b-CA.DC pro-inflammatory cytokine production. Together our data suggest that the Stat5b-Ezh2 axis is critical for the maintenance of tolerogenic high PD-L1-expressing cDC2 and autoimmune tolerance in NOD.Stat5b-CA mice.

A peripheral blood mononuclear cell-based in vitro model: A tool to explore indoleamine 2, 3-dioxygenase-1 (IDO1)

BACKGROUND

Proinflammatory cytokines powerfully induce the rate-limiting enzyme indoleamine 2, 3-dioxygenase-1 (IDO-1) in dendritic cells (DCs) and monocytes, it converts tryptophan (Trp) into L-kynurenine (KYN), along the kynurenine pathway (KP). This mechanism represents a crucial innate immunity regulator that can modulate T cells. This work explores the role of IDO1 in lymphocyte proliferation within a specific pro-inflammatory milieu.

METHODS

Peripheral blood mononuclera cells (PBMCs) were isolated from buffy coats taken from healthy blood donors and exposed to a pro-inflammatory milieu triggered by a double-hit stimulus: lipopolysaccharide (LPS) plus anti-CD3/CD28. The IDO1 mRNA levels in the PBMCs were measured by RT-PCR; the IDO1 activity was analyzed using the KYN/Trp ratio, measured by HPLC-EC; and lymphocyte proliferation was measured by flow cytometry. Trp and epacadostat (EP) were used as an IDO1 substrate and inhibitor, respectively. KYN, which is known to modulate Teffs, was tested as a positive control in lymphocyte proliferation.

RESULTS

IDO1 expression and activity in PBMCs increased in an in vitro pro-inflammatory milieu. The lymphoid stimulus increased IDO1 expression and activity, which supports the interaction between the activated lymphocytes and the circulating myeloid IDO1-expressing cells. The addition of Trp decreased lymphocyte proliferation but EP, which abrogated the IDO1 function, had no impact on proliferation. Additionally, incubation with KYN seemed to decrease the lymphocyte proliferation.

CONCLUSION

IDO1 inhibition did not change T lymphocyte proliferation. We present herein an in vitro experimental model suitable to measure IDO1 expression and activity in circulating myeloid cells.

Immune signature and phagocytosis of circulating DC subsets in healthy adults during aging

Dendritic cells (DC) play a pivotal role in the onset and progression of immunosenescence-associated diseases, serving as a link between innate and adaptive immunity. Thus, there is a need to establish reference ranges for DC subset levels in healthy adults and investigate the potential impact of age on DC subset levels and phagocytic activity. Single-platform multi-color flow cytometry was performed to assess the proportions of circulating conventional type 1 DC (cDC1), conventional type 2 DC (cDC2), and plasmacytoid DC (pDC), as well as the percentages of CD80, CD86, CD83, PD-L1, and CD32 in cDC1, cDC2, and pDC. Reference ranges were established based on age and gender, and the percentage of circulating DC subsets in different age groups was compared. In addition, circulating DC were enriched using a magnetic bead sorting kit and co-cultured with polystyrene (PS) beads, categorized by age groups, followed by the evaluation of PS bead phagocytosis using light microscopy and flow cytometry. The results indicated that the percentages of circulating cDC1, cDC2, and CD32+cDC2 decreased with age (P < 0.05) and revealed age-related impairment in phagocytic percentage of cDC2 (P < 0.05). These findings provide a deeper understanding of the impact of age on the phenotype and phagocytic activity of DC subsets, shedding light on their role and function in immunosenescence.

Distinct Immunophenotypic Features in Patients Affected by 22q11.2 Deletion Syndrome with Immune Dysregulation and Infectious Phenotype

The clinical expression of 22q11.2 deletion syndrome (22q11.2 DS) is extremely variable, as patients can present with recurrent or severe infections, immune dysregulation, atopic diseases, or extra-immunological manifestations. The immunological background underlying the different disease manifestations is not completely elucidated. The aim of this study was to identify the immunophenotypic peculiarities of 22q11.2 DS patients presenting with different disease expressions. This study included 34 patients with 22q11.2 DS, divided into three groups according to the clinical phenotype: isolated extra-immunological manifestations (G1), infectious phenotype with increased/severe infections (G2), and immune dysregulation (G3). The patients underwent extended immunophenotyping of the T and B lymphocytes and analysis of the circulating dendritic cells (DCs). In patients with an infectious phenotype, a significant reduction in CD3+ and CD4+ cells and an expansion of CD8 naïve cells was evidenced. On the other hand, the immunophenotype of the patients with immune dysregulation showed a skewing toward memory T cell populations, and reduced levels of recent thymic emigrants (RTEs), while the highest levels of RTEs were detected in the patients with isolated extra-immunological manifestations. This study integrates the current literature, contributing to elucidating the variability in the immune status of patients with 22q11.2DS with different phenotypic expressions, particularly in those with infectious phenotype and immune dysregulation.

Efficacy and Safety of Vaccinations in Geriatric Patients: A Literature Review

With the progressive lengthening of the average age of the population, especially in some countries such as Italy, vaccination of the elderly is a fixed point on which most of the public health efforts are concentrating as epidemic infectious diseases, especially those of the winter, have a major impact on the progression of severe disease, hospitalization, and death. The protection of the elderly against acute infectious diseases should not only limit mortality but also have a positive impact on the fragility of these people in terms of less disability and fewer care needs. However, vaccination of the elderly population differs in efficacy and safety compared to that of other population categories since aging and the consequent loss of efficiency of the immune system lead to a reduction in the immunogenicity of vaccines without achieving a lasting antibody coverage. There are various strategies to avoid the failure of immunization by vaccines such as resorting to supplementary doses with adjuvant vaccines, increasing the dosage of the antigen used, or choosing to inoculate the serum relying on various routes of administration of the vaccine. Vaccination in the elderly is also an important factor in light of growing antibiotic resistance because it can indirectly contribute to combating antibiotic resistance, reducing theoretically the use of those agents. Furthermore, vaccination in old age reduces mortality from infectious diseases preventable with vaccines and reduces the same rate of resistance to antibiotics. Given the importance and complexity of the topic, in this review, we will deal with the main aspects of vaccination in the elderly and how it can influence mortality and healthcare costs, especially in those countries where population aging is more evident. Therefore, we conducted a systematic literature search in PubMed to identify all types of studies published up to 31 May 2023 that examined the association between vaccination and the elderly. Data extraction and quality assessment were conducted by two reviewers (PC and TC) who independently extracted the following data and assessed the quality of each study.

Contrariety of Human Bone Marrow Mesenchymal Stromal Cell Functionality in Modulating Circulatory Myeloid and Plasmacytoid Dendritic Cell Subsets

Mesenchymal Stromal Cells (MSCs) derived from bone marrow are widely tested in clinical trials as a cellular therapy for potential inflammatory disorders. The mechanism of action of MSCs in mediating immune modulation is of wide interest. In the present study, we investigated the effect of human bone-marrow-derived MSCs in modulating the circulating peripheral blood dendritic cell responses through flow cytometry and multiplex secretome technology upon their coculture ex vivo. Our results demonstrated that MSCs do not significantly modulate the responses of plasmacytoid dendritic cells. However, MSCs dose-dependently promote the maturation of myeloid dendritic cells. Mechanistic analysis showed that dendritic cell licensing cues (Lipopolysaccharide and Interferon-gamma) stimulate MSCs to secret an array of dendritic cell maturation-associated secretory factors. We also identified that MSC-mediated upregulation of myeloid dendritic cell maturation is associated with the unique predictive secretome signature. Overall, the present study demonstrated the dichotomy of MSC functionality in modulating myeloid and plasmacytoid dendritic cells. This study provides clues that clinical trials need to investigate if circulating dendritic cell subsets in MSC therapy can serve as potency biomarkers.

Dendritic cells in inborn errors of immunity

Dendritic cells (DCs) are crucial cells for initiating and maintaining immune response. They play critical role in homeostasis, inflammation, and autoimmunity. A number of molecules regulate their functions including synapse formation, migration, immunity, and induction of tolerance. A number of IEI are characterized by mutations in genes encoding several of these molecules resulting in immunodeficiency, inflammation, and autoimmunity in IEI. Currently, there are 465 Inborn errors of immunity (IEI) that have been grouped in 10 different categories. However, comprehensive studies of DCs have been reported in only few IEI. Here we have reviewed biology of DCs in IEI classified according to recently published IUIS classification. We have reviewed DCs in selected IEI in each group category and discussed in depth changes in DCs where significant data are available regarding role of DCs in clinical and immunological manifestations. These include severe immunodeficiency diseases, antibody deficiencies, combined immunodeficiency with associated and syndromic features, especially disorders of synapse formation, and disorders of immune regulation.

Nanoparticle vaccines can be designed to induce pDC support of mDCs for increased antigen display

Cancer vaccine immunotherapy facilitates the immune system's recognition of tumor-associated antigens, and the biomolecular design of these vaccines using nanoparticles is one important approach towards obtaining strong anti-tumor responses. Following activation of dendritic cells (DCs), a robust CD8+ T cell-mediated adaptive immune response is critical for tumor elimination. While the role of efficient antigen-presenting myeloid DCs (mDCs) is conventionally attributed towards vaccine efficacy, participation by highly cytokine-producing plasmacytoid DCs (pDCs) is less understood and is often overlooked. We examined vaccines based on the E2 protein nanoparticle platform that delivered encapsulated TLR9 agonist bacterial-like DNA (CpG1826 or CpG1018) or TLR7 agonist viral ssRNA to determine their efficacy over free agonists in activating both mDCs and pDCs for antigen presentation. Although mDCs were only activated by nanoparticle-encapsulated TLR9 agonists, pDCs were activated by all the individually tested constructs, and CpG1826 was shown to induce pDC cytokine production. Transfer of secreted factors from pDCs that were stimulated with a vaccine formulation comprising peptide antigen and CpG1826 enhanced mDC display of the antigen, particularly when delivered in nanoparticles. Only when treated with nanoparticle-conjugated vaccine could pDCs secrete factors to induce antigen display on naïve mDCs. These results reveal that pDCs can aid mDCs, highlighting the importance of activating both pDCs and mDCs in designing effective cancer vaccines, and demonstrate the advantage of using nanoparticle-based vaccine delivery.

DDX58 Is Associated With Susceptibility to Severe Influenza Virus Infection in Children and Adolescents

BACKGROUND

Seasonal influenza virus infection causes a range of disease severity, including lower respiratory tract infection with respiratory failure. We evaluated the association of common variants in interferon (IFN) regulatory genes with susceptibility to critical influenza infection in children.

METHODS

We performed targeted sequencing of 69 influenza-associated candidate genes in 348 children from 24 US centers admitted to the intensive care unit with influenza infection and lacking risk factors for severe influenza infection (PICFlu cohort, 59.4% male). As controls, whole genome sequencing from 675 children with asthma (CAMP cohort, 62.5% male) was compared. We assessed functional relevance using PICFlu whole blood gene expression levels for the gene and calculated IFN gene signature score.

RESULTS

Common variants in DDX58, encoding the retinoic acid-inducible gene I (RIG-I) receptor, demonstrated association above or around the Bonferroni-corrected threshold (synonymous variant rs3205166; intronic variant rs4487862). The intronic single-nucleotide polymorphism rs4487862 minor allele was associated with decreased DDX58 expression and IFN signature (P < .05 and P = .0009, respectively) which provided evidence supporting the genetic variants' impact on RIG-I and IFN immunity.

CONCLUSIONS

We provide evidence associating common gene variants in DDX58 with susceptibility to severe influenza infection in children. RIG-I may be essential for preventing life-threatening influenza-associated disease.

A gut-centric view of aging: Do intestinal epithelial cells contribute to age-associated microbiota changes, inflammaging, and immunosenescence?

Intestinal epithelial cells (IECs) serve as both a physical and an antimicrobial barrier against the microbiota, as well as a conduit for signaling between the microbiota and systemic host immunity. As individuals age, the balance between these systems undergoes a myriad of changes due to age-associated changes to the microbiota, IECs themselves, immunosenescence, and inflammaging. In this review, we discuss emerging data related to age-associated loss of intestinal barrier integrity and posit that IEC dysfunction may play a central role in propagating age-associated alterations in microbiota composition and immune homeostasis.

How Can We Improve Vaccination Response in Old People? Part I: Targeting Immunosenescence of Innate Immunity Cells

Vaccination, being able to prevent millions of cases of infectious diseases around the world every year, is the most effective medical intervention ever introduced. However, immunosenescence makes vaccines less effective in providing protection to older people. Although most studies explain that this is mainly due to the immunosenescence of T and B cells, the immunosenescence of innate immunity can also be a significant contributing factor. Alterations in function, number, subset, and distribution of blood neutrophils, monocytes, and natural killer and dendritic cells are detected in aging, thus potentially reducing the efficacy of vaccines in older individuals. In this paper, we focus on the immunosenescence of the innate blood immune cells. We discuss possible strategies to counteract the immunosenescence of innate immunity in order to improve the response to vaccination. In particular, we focus on advances in understanding the role and the development of new adjuvants, such as TLR agonists, considered a promising strategy to increase vaccination efficiency in older individuals.

Clinical, Immunological, and Genetic Findings in a Cohort of Patients with the DiGeorge Phenotype without 22q11.2 Deletion

Chromosome 22q11.2 deletion syndrome (22q11.2DS) is a primary immunodeficiency characterized by a broad and heterogeneous clinical presentation associated with various degrees of T-cell deficiency. We report the clinical, immunologic, and genetic findings of a cohort of eight patients presenting with a clinical phenotype that is highly suggestive of this syndrome but without the 22q11.2 deletion. The cardinal features of 22q11.2DS, such as congenital heart defects, hypoparathyroidism, and facial dysmorphisms, were observed in the majority of the patient cohort. The unusual features are described in detail. The immunologic assessment showed various degrees of immunodeficiency of the T-cell compartment, notably a reduction in the thymic output. Half of the patient cohort exhibited a reduction in total dendritic cells. Array comparative genomic hybridization (CGH) revealed six patients harboring copy number variations (CNVs) never reported in normal subjects. The gene content of these CNVs was carefully analyzed to understand the mechanisms leading to 22q11.2DS phenocopies. According to these results, we suggested that array-CGH should be used as a first-tier tool for patients resembling 22q11.2DS.

Dendritic cell differentiation from human induced pluripotent stem cells: challenges and progress

Dendritic cells (DCs) are the major antigen-presenting cells of the immune system responsible for initiating and coordinating immune responses. These abilities provide potential for several clinical applications, such as the development of immunogenic vaccines. However, difficulty in obtaining DCs from conventional sources, such as bone marrow (BM), peripheral blood (PBMC), and cord blood (CB), is a significantly hinders routine application. The use of human induced pluripotent stem cells (hiPSCs) is a valuable alternative for generating sufficient numbers of DCs to be used in basic and pre-clinical studies. Despite the many challenges that must be overcome to achieve an efficient protocol for obtaining the major DC types from hiPSCs, recent progress has been made. Here we review the current state of developing DCs from hiPSCs, as well as the key elements required to enable the routine use of hiPSC-derived DCs in pre-clinical and clinical assays.

Rebalancing the unbalanced aged immune system - A special focus on zinc

Nowadays, aging is understood as a dynamic and multifaceted dysregulation process that spares almost no human organ or cell. The immune system being among the most affected, it has been shown predominantly that its integrity determines the tightrope walk between the difference of escaping or suffering from age-related diseases. Next to drug-based anti-aging strategies, micronutrient intervention may represent an emerging but less radical way to slow immune aging. While a sufficient supply of a variety of micronutrients is undeniably important, adequate intake of the trace element zinc appears to tower over others in terms of reaching old age. Inconveniently, zinc deficiency prevalence among the elderly is high, which in turn contributes to increased susceptibility to infection, decreased anti-tumor immunity as well as attenuated response to vaccination. Driven by this research, this review aims to provide a comprehensive and up-to-date overview of the various rebalancing capabilities of zinc in the unbalanced immune system of the elderly. This includes an in-depth and cell type-centered discussion on the role of zinc in immunosenescence and inflammaging. We further address upcoming translational aspects e.g. how zinc deficiency promotes the flourishing of certain pathogenic taxa of the gut microbiome and how zinc supply counteracts such alterations in a manner that may contribute to longevity. In the light of the ongoing COVID-19 pandemic, we also briefly review current knowledge on the interdependency between age, zinc status, and respiratory infections. Based on two concrete examples and considering the latest findings in the field we conclude our remarks by outlining tremendous parallels between suboptimal zinc status and accelerated aging on the one hand and an optimized zinc status and successful aging on the other hand.

Infection in the Developing Brain: The Role of Unique Systemic Immune Vulnerabilities

Central nervous system (CNS) infections remain a major burden of pediatric disease associated with significant long-term morbidity due to injury to the developing brain. Children are susceptible to various etiologies of CNS infection partly because of vulnerabilities in their peripheral immune system. Young children are known to have reduced numbers and functionality of innate and adaptive immune cells, poorer production of immune mediators, impaired responses to inflammatory stimuli and depressed antibody activity in comparison to adults. This has implications not only for their response to pathogen invasion, but also for the development of appropriate vaccines and vaccination strategies. Further, pediatric immune characteristics evolve across the span of childhood into adolescence as their broader physiological and hormonal landscape develop. In addition to intrinsic vulnerabilities, children are subject to external factors that impact their susceptibility to infections, including maternal immunity and exposure, and nutrition. In this review we summarize the current evidence for immune characteristics across childhood that render children at risk for CNS infection and introduce the link with the CNS through the modulatory role that the brain has on the immune response. This manuscript lays the foundation from which we explore the specifics of infection and inflammation within the CNS and the consequences to the maturing brain in part two of this review series.

Interconnections between Inflammageing and Immunosenescence during Ageing

Acute inflammation is a physiological response to injury or infection, with a cascade of steps that ultimately lead to the recruitment of immune cells to clear invading pathogens and heal wounds. However, chronic inflammation arising from the continued presence of the initial trigger, or the dysfunction of signalling and/or effector pathways, is harmful to health. While successful ageing in older adults, including centenarians, is associated with low levels of inflammation, elevated inflammation increases the risk of poor health and death. Hence inflammation has been described as one of seven pillars of ageing. Age-associated sterile, chronic, and low-grade inflammation is commonly termed inflammageing-it is not simply a consequence of increasing chronological age, but is also a marker of biological ageing, multimorbidity, and mortality risk. While inflammageing was initially thought to be caused by "continuous antigenic load and stress", reports from the last two decades describe a much more complex phenomenon also involving cellular senescence and the ageing of the immune system. In this review, we explore some of the main sources and consequences of inflammageing in the context of immunosenescence and highlight potential interventions. In particular, we assess the contribution of cellular senescence to age-associated inflammation, identify patterns of pro- and anti-inflammatory markers characteristic of inflammageing, describe alterations in the ageing immune system that lead to elevated inflammation, and finally assess the ways that diet, exercise, and pharmacological interventions can reduce inflammageing and thus, improve later life health.

Whole Blood Dendritic Cell Cytokine Production Assay

This protocol outlines a method for the timely detection of intracellular cytokines produced by activated dendritic cells (DC) in human whole blood. The quantification of cytokines is used to measure DC immune responsiveness, providing information on the breadth, strength, and DC subtypes responding spontaneously and to specific stimulation with toll-like receptor (TLR) ligands or parasite-infected erythrocytes. DC subsets, plasmacytoid DC, CD1c⁺ DC, CD141⁺ DC, and CD16⁺ DC, are examined in their natural environment of plasma and blood cells (erythrocytes, neutrophils, platelets, and leukocytes) enabling disease, medication, nutritional, and hematological effects on DC function to be examined in vaccine studies, ageing, health, and disease.

Transcriptomic Analysis Identifies A Tolerogenic Dendritic Cell Signature

Dendritic cells (DC) are central to regulating innate and adaptive immune responses. Strategies that modify DC function provide new therapeutic opportunities in autoimmune diseases and transplantation. Current pharmacological approaches can alter DC phenotype to induce tolerogenic DC (tolDC), a maturation-resistant DC subset capable of directing a regulatory immune response that are being explored in current clinical trials. The classical phenotypic characterization of tolDC is limited to cell-surface marker expression and anti-inflammatory cytokine production, although these are not specific. TolDC may be better defined using gene signatures, but there is no consensus definition regarding genotypic markers. We address this shortcoming by analyzing available transcriptomic data to yield an independent set of differentially expressed genes that characterize human tolDC. We validate this transcriptomic signature and also explore gene differences according to the method of tolDC generation. As well as establishing a novel characterization of tolDC, we interrogated its translational utility in vivo, demonstrating this geneset was enriched in the liver, a known tolerogenic organ. Our gene signature will potentially provide greater understanding regarding transcriptional regulators of tolerance and allow researchers to standardize identification of tolDC used for cellular therapy in clinical trials.

The epidemiologic and biologic basis for classifying older age as a high-risk, immunocompromising condition for pneumococcal vaccine policy

INTRODUCTION

Immunosenescence is a normal biologic process involving deterioration of protective immune responses. Consequently, older adults experience increased risk of infectious diseases, particularly pneumonia, and its leading bacterial cause, Streptococcus pneumoniae. Pneumococcal vaccine recommendations are often limited to adults with specific medical conditions despite similar disease risks among older adults due to immunosenescence.

AREAS COVERED

This article reviews epidemiologic, biologic, and clinical evidence supporting the consideration of older age due to immunosenescence as an immunocompromising condition for the purpose of pneumococcal vaccine policy and the role vaccination can play in healthy aging.

EXPERT OPINION

Epidemiologic and biologic evidence suggest that pneumococcal disease risk increases with age and is comparable for healthy older adults and younger adults with immunocompromising conditions. Because immunocompromising conditions are already indicated for pneumococcal conjugate vaccines (PCVs), a comprehensive public health strategy would also recognize immunosenescence. Moreover, older persons should be vaccinated before reaching the highest risk ages, consistent with the approach for other immunocompromising conditions. To facilitate PCV use among older adults, vaccine technical committees (VTCs) could classify older age as an immunocompromising condition based on the process of immunosenescence. With global aging, VTCs will need to consider immunosenescence and vaccine use during healthy aging.

A low level of CD16pos monocytes in SARS-CoV-2 infected patients is a marker of severity

OBJECTIVES

Severe forms of coronavirus disease 2019 (COVID-19) are characterized by an excessive production of inflammatory cytokines. Activated monocytes secrete high levels of cytokines. Human monocytes are divided into three major populations: conventional (CD14^posCD16^neg), non-classical (CD14^dimCD16^pos), and intermediate (CD14^posCD16^pos) monocytes. The aim of this study was to analyze whether the distribution of conventional (CD16^neg) and CD16^pos monocytes is different in patients with COVID-19 and whether the variations could be predictive of the outcome of the disease.

METHODS

We performed a prospective study on 390 consecutive patients referred to the Emergency Unit, with a proven diagnosis of SARS-CoV 2 infection by RT-PCR. Using the CytoDiff™ reagent, an automated routine leukocyte differential, we quantified CD16^neg and CD16^pos monocytes.

RESULTS

In the entire population, median CD16^neg and CD16^pos monocyte levels (0.398 and 0.054×10⁹/L, respectively) were in the normal range [(0.3-0.7×10⁹/L) and (0.015-0.065×10⁹/L), respectively], but the 35 patients in the intensive care unit (ICU) had a significantly (p<0.001) lower CD16^pos monocyte count (0.018 × 10⁹/L) in comparison to the 70 patients who were discharged (0.064 × 10⁹/L) or were hospitalized in conventional units (0.058 × 10⁹/L). By ROC curve analysis, the ratio [absolute neutrophil count/CD16^pos monocyte count] was highly discriminant to identify patients requiring ICU hospitalization: with a cut-off 193.1, the sensitivity and the specificity were 74.3 and 81.8%, respectively (area under the curve=0.817).

CONCLUSIONS

Quantification of CD16^pos monocytes and the ratio [absolute neutrophil count/CD16^pos monocyte count] could constitute a marker of the severity of disease in COVID-19 patients.

Age-related differences in the immune response could contribute to determine the spectrum of severity of COVID-19

Coronavirus disease 2019 (COVID‐19), can present with a wide spectrum of severity. Elderly patients with cardiac, pulmonary and metabolic comorbidities are more likely to develop the severe manifestations of COVID‐19, which are observed in less than 5% of the pediatric patients. Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) is able to induce an immune impairment and dysregulation, finally resulting in the massive release of inflammatory mediators, strongly contributing to the pulmonary and systemic manifestations in COVID‐19. In children, the immune dysregulation following SARS‐CoV‐2 can also be responsible of a severe disease phenotype defined as multisystem inflammatory syndrome in children. As the immune system undergoes a complex process of maturation from birth to adult age, differences in the immune and inflammatory response could have a significant impact in determining the spectrum of severity of COVID‐19. Indeed, children show a higher ability to respond to viral infections and a reduced baseline pro‐inflammatory state compared with elderly patients. Age and comorbidities contribute to disease severity through immune‐mediated mechanisms, since they are associated with a chronic increase of pro‐inflammatory mediators, and cause an enhanced susceptibility to develop an immune dysregulation following SARS‐CoV‐2 infection. Also the expression of ACE2, the receptor of SARS‐CoV‐2, varies with age, and is linked to the immune and inflammatory response through a complex, and not completely elucidated, network. This paper reviews the peculiar immunopathogenic aspects of COVID‐19, with a focus on the differences between adult and pediatric patients.

Accelerator or Brake: Immune Regulators in Malaria

Malaria is a life-threatening infectious disease, affecting over 250 million individuals worldwide each year, eradicating malaria has been one of the greatest challenges to public health for a century. Growing resistance to anti-parasitic therapies and lack of effective vaccines are major contributing factors in controlling this disease. However, the incomplete understanding of parasite interactions with host anti-malaria immunity hinders vaccine development efforts to date. Recent studies have been unveiling the complexity of immune responses and regulators against Plasmodium infection. Here, we summarize our current understanding of host immune responses against Plasmodium-derived components infection and mainly focus on the various regulatory mechanisms mediated by recent identified immune regulators orchestrating anti-malaria immunity.

Nanoparticles (PLGA and Chitosan)-Entrapped ADP-Ribosylation Factor 1 of Haemonchus contortus Enhances the Immune Responses in ICR Mice

ADP-ribosylation factor 1 (HcARF1) is one of the Haemonchus contortus (H. contortus) excretory/secretory proteins involved in modulating the immune response of goat peripheral blood mononuclear cells (PBMC). Here, we evaluated the immunogenic potential of recombinant HcARF1 (rHcARF1) against H. contortus infection in Institute of Cancer Research (ICR) mice. Briefly, rHcARF1 was entrapped in poly (D, L-lactide-co-glycolide) (PLGA) and chitosan (CS) nanoparticles (NP) and injected into mice as a vaccine. Fifty-six ICR mice were assigned randomly into seven groups, with eight animals in each group, and they were vaccinated subcutaneously. At the end of the experiment (14th day), the blood and the spleen were collected from euthanized mice to detect lymphocyte proliferation, cytokine analysis, and the production of antigen-specific antibodies. Scanning electron microscope was used to determine the size, morphology, and zeta potential of nanoparticles. Flow cytometry was performed, which presented the increase percentages of CD4⁺ T cells (CD3e⁺CD4⁺), CD8⁺ T cells (CD3e⁺CD8⁺) and dendritic cells (CD11c⁺CD83⁺, CD11c⁺CD86⁺) in mice vaccinated with rHcARF1+PLGA NP. Immunoassay analysis show raised humoral (Immunoglobulin (Ig)G1, IgG2a, IgM) and cell-mediated immune response (Interleukin (IL)-4, IL-12, and IL-17, and Interferon (IFN)-γ) induced by rHcARF1+PLGA NP. Experimental groups that were treated with the antigen-loaded NP yield higher lymphocyte proliferation than the control groups. Based on these results, we could propose that the rHcARF1 encapsulated in NP could stimulate a strong immune response in mice rather than administering alone against the infection of H. contortus.

Setting the stage: The initial immune response to blood-stage parasites

Individuals growing up in malaria endemic areas gradually develop protection against clinical malaria and passive transfer experiments in humans have demonstrated that this protection is mediated in part by protective antibodies. However, neither the target antigens, specific effector mechanisms, nor the role of continual parasite exposure have been elucidated, which complicates vaccine development. Progress has been made in defining the innate signaling pathways activated by parasite components, including DNA, RNA, hemozoin, and phospholipids, which initiate the immune response and will be the focus of this review. The challenge that remains within the field is to understand the role of these early responses in the development of protective adaptive responses that clear iRBC and block merozoite invasion so that optimal vaccines and therapeutics may be produced.

Comprehensive flow cytometric reference intervals of leukocyte subsets from six study centers across Europe

A group of European FOCIS Centers of Excellence adapted panels of the Human Immunophenotyping Consortium (HIPC) for whole blood analysis. Using four core panels [T/regulatory T cell/B/natural killer (T/T_reg/B/NK) and myeloid cells] the main leukocyte populations were analyzed in a clinical–diagnostic setting in a harmonized manner across different platforms. As a first step, the consortium presents here the absolute and relative frequencies of the leukocyte subpopulations in the peripheral blood of more than 300 healthy volunteers across six different European centers.

Vitamin D status and the immune assessment in 22q11.2 deletion syndrome

22q11.2 deletion syndrome (22q11.2DS) is characterized by a heterogeneous phenotype, including alterations in phospho-calcium metabolism and immunodeficiency. We analyzed vitamin D status and the immune assessment, focusing on T cell subpopulations and dendritic cells (DCs) in a cohort of 17 pediatric 22q11.2DS patients and 17 age-matched healthy subjects. As antigen-presenting cells, DCs are the main target of vitamin D, promoting a tolerogenic T cell response. Patients were subdivided into three groups according to the parameters of phospho-calcium metabolism and serum levels of 25OHD: normal values, vitamin D deficiency and hypoparathyroidism. Different degrees of T cell deficiency, ranging from normal to partial T cell numbers, were observed in the cohort of patients. The group with vitamin D deficiency showed a significant reduction of naive T cells and a significant increase of central memory T cells compared to controls. In this group the number of circulating DCs was significantly reduced. DC decrease affected both myeloid and plasmacytoid DC subsets (mDCs and pDCs), with the most relevant reduction involving pDCs. A direct correlation between 25OHD levels and recent thymic emigrant (RTE) and DC number was identified. Despite the limited cohort analyzed, our results show that deficiency of the pDC subset in patients with 22q11.2DS may be included among the causative factors of the progressive increase of risk of autoimmune diseases in these patients. As most patients suffer from increased susceptibility to infections and heightened prevalence of autoimmune disorders, we suggest a potential role of vitamin D supplementation in preventing autoimmune or proinflammatory diseases in 22q11.2DS.

Novel insights into dendritic cells in the pathogenesis of systemic sclerosis

Systemic sclerosis (SSc) is a severe autoimmune fibrotic disease characterized by fibrosis, vasculopathy, and immune dysregulation. Dendritic cells (DCs) are the most potent antigen-presenting cells, specialized in pathogen sensing, with high capacity to shape the immune responses. The most recent technological advances have allowed the discovery of new DC subsets with potential implications in inflammatory conditions. Alterations of DC distribution in circulation and affected tissue as well as impaired DC function have been described in SSc patients, pointing towards a crucial role of these cells in SSc pathogenesis. In particular, recent studies have shown the importance of plasmacytoid DCs either by their high capacity to produce type I interferon or other inflammatory mediators implicated in SSc pathology, such as chemokine C-X-C motif ligand 4 (CXCL4). In-vivo models of SSc have been vital to clarify the implications of DCs in this disease, especially DCs depletion and specific gene knock-down studies. This review provides these new insights into the contribution of the different DCs subsets in the pathogenesis of SSc, as well as to the novel developments on DCs in in-vivo models of SSc and the potential use of DCs and their mediators as therapeutic targets.

The evaluation of cytokines to help establish diagnosis and guide treatment of autoinflammatory and autoimmune diseases

Our knowledge of the role of cytokines in pathologic conditions has increased considerably with the emergence of molecular and genetic studies, particularly in the case of autoinflammatory monogenic diseases. Many rare disorders, considered orphan until recently, are directly related to abnormal gene regulation, and the treatment with biologic agents (biologics) targeting cytokine receptors, intracellular signaling or specific cytokines improve the symptoms of an increasing number of chronic inflammatory diseases. As it is currently impossible to systematically conduct genetic studies for all patients with autoinflammatory and autoimmune diseases, the evaluation of cytokines can be seen as a simple, less time consuming, and less expensive alternative. This approach could be especially useful when the diagnosis of syndromes of diseases of unknown etiology remains problematic. The evaluation of cytokines could also help avoid the current trial-and-error approach, which has the disadvantages of exposing patients to ineffective drugs with possible unnecessary side effects and permanent organ damages. In this review, we discuss the various possibilities, as well as the limitations of evaluating the cytokine profiles of patients suffering from autoinflammatory and autoimmune diseases, with methods such as direct detection of cytokines in the plasma/serum or following ex vivo stimulation of PBMCs leading to the production of their cytokine secretome. The patients' secretome, combined with biomarkers ranging from genetic and epigenetic analyses to immunologic biomarkers, may help not only the diagnosis but also guide the choice of biologics for more efficient and rapid treatments.

Plasmacytoid dendritic cell and myeloid dendritic cell function in ageing: A comparison between elderly and young adult women

Ageing is associated with a changing immune system, leading to inflammageing (increased levels of inflammation markers in serum) and immunosenescence (reduced immune cells and reduced responses towards pathogens). This results in reduced vaccination responses and increased infections in elderly. Much is known about the adaptive immune system upon ageing, but less is known about the innate immune system. Therefore, the aim of this study was to compare innate immune function of Toll like receptor (TLR)-mediated responses between elderly and young adult women.

To this end, elderly and young adult women were compared to study the effect of ageing on the relative prevalence and reactivity to TLR-mediated responses of myeloid- and plasmacytoid dendritic cells (mDC, pDC). In addition, TLR expression and inflammatory markers in serum were investigated. Elderly women had reduced numbers of circulating pDCs. In addition, pDCs and mDCs of elderly women responded differently towards TLR stimulation, especially TLR7/8 mediated stimulation was reduced, compared to young adults. In serum, markers involved in inflammation were generally increased in elderly. In conclusion, this study confirms and extends the knowledge about immunosenescence and inflammageing on innate immunity in elderly women.

Relationship between Helicobacter pylori Infection and Plasmacytoid and Myeloid Dendritic Cells in Peripheral Blood and Gastric Mucosa of Children

PURPOSE

To investigate the frequency and activation status of peripheral plasmacytoid DCs (pDCs) and myeloid DCs (mDCs) as well as gastric mucosa DC subset distribution in Helicobacter pylori- (H. pylori-) infected and noninfected children.

MATERIALS AND METHODS

Thirty-six children were studied; twenty-one had H. pylori. The frequencies of circulating pDCs (lineage-HLA-DR+CD123+) and mDCs (lineage-HLA-DR+CD11c+) and their activation status (CD83, CD86, and HLA-DR expression) were assessed by flow cytometry. Additionally, the densities of CD11c+, CD123+, CD83+, CD86+, and LAMP3+ cells in the gastric mucosa were determined by immunohistochemistry.

RESULTS

The frequency of circulating CD83+ mDCs was higher in H. pylori-infected children than in the noninfected controls. The pDCs demonstrated upregulated HLA-DR surface expression, but no change in CD86 expression. Additionally, the densities of gastric lamina propria CD11c+ cells and epithelial pDCs were increased. There was a significant association between frequency of circulating CD83+ mDCs and gastric lamina propria mDC infiltration.

CONCLUSION

This study shows that although H. pylori-infected children had an increased population of mature mDCs bearing CD83 in the peripheral blood, they lack mature CD83+ mDCs in the gastric mucosa, which may promote tolerance to local antigens rather than immunity. In addition, this may reduce excessive inflammatory activity as reported for children compared to adults.

Negative impact of proteinuria on circulating myeloid dendritic cells

Background

A decrease in absolute numbers (abs.) of circulating dendritic cells (DCs) and recruitment into target organs has been reported, but whether the level of proteinuria associates with circulating DC abs. has not been clarified.

Methods

We conducted a cross-sectional study of 210 patients with kidney disease aged 21–96 years who were admitted to our hospital for kidney biopsy in 2007–2010. For accuracy, the level of proteinuria was thoroughly measured by 24-h urine collection from patients in their admitted condition. The abs. of total DCs (tDCs), myeloid DCs (mDCs) and plasmacytoid DCs (pDCs) was measured by three-color fluorescence-activated cell sorting (FACS). Patients were divided into four groups based upon the quartile of each DC abs. and one-way ANOVA, and multivariable-adjusted regression analyses were performed.

Results

Quantile analysis showed that the level of daily proteinuria decreased with increasing blood mDC abs., with mean proteinuria levels (g/day) of 2.45, 1.68, 1.68, 1.10 for those in mDC abs. quartiles ≤ 445, < 686, < 907, ≥ 907 cells/10² µL (p = 0.0277), respectively. Multivariate-adjusted regression analysis revealed that the mDC abs. was negatively associated with proteinuria (95% CI − 57.0 to − 8.5) and positively associated with male gender (95% CI 66.2–250.5). Independent associations were also shown between pDCs abs. and estimated glomerular filtration rate (eGFR) (95% CI 0.14–2.67) and C-reactive protein (95% CI − 49.4 to − 9.9) and between tDCs abs. and male gender (95% CI 54.5–253.6) and C-reactive protein (95% CI − 80.5 to − 13.4).

Conclusion

We first reported that circulating mDC abs. has a negative association with the level of proteinuria.

HIV Replication in Humanized IL-3/GM-CSF-Transgenic NOG Mice

The development of mouse models that mimic the kinetics of Human Immunodeficiency Virus (HIV) infection is critical for the understanding of the pathogenesis of disease and for the design of novel therapeutic strategies. Here, we describe the dynamics of HIV infection in humanized NOD/Shi-scid-IL2rγ^null (NOG) mice bearing the human genes for interleukin (IL)-3 and granulocyte-macrophage colony-stimulating factor (GM-CSF) (NOG-EXL mice). The kinetics of viral load, as well as the frequencies of T-cells, B-cells, Natural killer cells (NK), monocytes, and dendritic cells in blood and secondary lymphoid organs were evaluated throughout the time of infection. In comparison with a non-transgenic humanized mouse (NSG) strain, lymphoid and myeloid populations were more efficiently engrafted in humanized NOG-EXL mice, both in peripheral blood and lymphoid tissues. In addition, HIV actively replicated in humanized NOG-EXL mice, and infection induced a decrease in the percentage of CD4⁺ T-cells, inversion of the CD4:CD8 ratio, and changes in some cell populations, such as monocytes and dendritic cells, that recapitulated those found in human natural infection. Thus, the humanized IL-3/GM-CSF-transgenic NOG mouse model is suitable for the study of the dynamics of HIV infection and provides a tool for basic and preclinical studies.

Dendritic Cell Responses and Function in Malaria

Malaria remains a serious threat to global health. Sustained malaria control and, eventually, eradication will only be achieved with a broadly effective malaria vaccine. Yet a fundamental lack of knowledge about how antimalarial immunity is acquired has hindered vaccine development efforts to date. Understanding how malaria-causing parasites modulate the host immune system, specifically dendritic cells (DCs), key initiators of adaptive and vaccine antigen-based immune responses, is vital for effective vaccine design. This review comprehensively summarizes how exposure to Plasmodium spp. impacts human DC function in vivo and in vitro. We have highlighted the heterogeneity of the data observed in these studies, compared and critiqued the models used to generate our current understanding of DC function in malaria, and examined the mechanisms by which Plasmodium spp. mediate these effects. This review highlights potential research directions which could lead to improved efficacy of existing vaccines, and outlines novel targets for next-generation vaccine strategies to target malaria.

An integrated framework using high-dimensional mass cytometry and fluorescent flow cytometry identifies discrete B cell subsets in patients with red meat allergy

BACKGROUND

B cells play a critical role in the development and maintenance of food allergy by producing allergen-specific IgE. Despite the importance of B cells in IgE-mediated food allergy, the identity of sIgE-producing human B cells and how IgE is regulated are poorly understood.

OBJECTIVE

To identify the immunophenotypes of circulating B cells associated with the production of galactose-alpha-1,3-galactose-specific IgE production in patients with red meat allergy.

METHODS

B cells in PBMC samples obtained from 19 adults with physician-diagnosed red meat allergy and 20 non-meat allergic healthy controls were assessed by mass cytometry along with a bioinformatics analysis pipeline to identify discrete B cell phenotypes that associated with serum sIgE. Fluorescent flow cytometry was then applied to sort purify discrete B cell subsets, and B cells were functionally evaluated on an individual cell level for the production of sIgE by ELISPOT.

RESULTS

Discrete B cell phenotypes abundant in meat allergic subjects compared to non-meat allergic controls were found in peripheral blood that do not share typical characteristics of classical isotype-switched memory B cells that express high levels of CD27. These B cell subsets shared higher IgD and lower IgM expression levels coupled with CXCR4, CCR6 and CD25 expression. In vitro polyclonal stimulation of purified B cell subsets from meat allergic subjects demonstrated that these subsets were enriched for cells induced to secrete sIgE.

CONCLUSIONS AND CLINICAL RELEVANCE

Circulating B cells display increased abundance of discrete B cell subsets in meat allergic subjects. This observation, coupled with the capacity of individual B cell subsets to produce sIgE following activation, implicates these novel B cell phenotypes in promoting IgE in meat allergy.

Does the Immunocompetent Status of Cancer Patients Have an Impact on Therapeutic DC Vaccination Strategies?

Although different types of therapeutic vaccines against established cancerous lesions in various indications have been developed since the 1990s, their clinical benefit is still very limited. This observed lack of effectiveness in cancer eradication may be partially due to the often deficient immunocompetent status of cancer patients, which may facilitate tumor development by different mechanisms, including immune evasion. The most frequently used cellular vehicle in clinical trials are dendritic cells (DCs), thanks to their crucial role in initiating and directing immune responses. Viable vaccination options using DCs are available, with a positive toxicity profile. For these reasons, despite their limited therapeutic outcomes, DC vaccination is currently considered an additional immunotherapeutic option that still needs to be further explored. In this review, we propose potential actions aimed at improving DC vaccine efficacy by counteracting the detrimental mechanisms recognized to date and implicated in establishing a poor immunocompetent status in cancer patients.

Aging, inflammation and cancer

Aging is a key aspect of neoplasia at the level of cells, individuals and populations. Unrestrained expression and production of inflammatory mediators is a key feature of aging at the cellular and organism level. Inflammatory cells and mediators are a key component of the tumor microenvironment and drive tumor progression. Non-resolving smoldering inflammation increases the risk of cancer (the extrinsic pathway connecting inflammation and cancer). In the intrinsic pathway, genetic events that cause neoplasia (oncogenes and oncosupressor genes) orchestrate the construction of cancer-related inflammation. We argue that uncontrolled smoldering inflammation drives carcinogenesis in aging and acts as a common denominator linking aging and cancer.

Imbalance of the two main circulating dendritic cell subsets in patients with myasthenia gravis

Although it is well documented that circulating dendritic cells (DCs) have specialized features during many kinds of physiological and pathological conditions, there are few reports about the features of DCs in the peripheral blood of myasthenia gravis (MG) patients. We investigated the quantitative and component features of DCs and their implications in MG. Peripheral blood samples from different kinds of MG patients were collected and their clinical characteristics were recorded. Using flow cytometry, we distinguished circulating DC subsets [plasmacytoid DCs (pDCs) and myeloid DCs (mDCs)] and enumerated their densities in peripheral blood. Absolute numbers of circulating pDCs were significantly decreased in naïve MG patients compared with healthy controls, resulting in a markedly lower ratio of the pDC to mDC percentage in total circulating DCs (pDCs/mDCs), suggesting an imbalance in the proportions of the two main circulating DC subsets. The clinical status of MG patients was improved after drug treatment, together with increased pDCs/mDCs. In a longitudinal follow-up, we observed that circulating mDCs were significantly reduced after 1 month of therapy with a corticosteroid and immunosuppressant, resulting in recovery of pDCs/mDCs. Although the exact meaning of the proportion change in circulating DC subsets is unknown, pDCs/mDCs might reflect the balance between the autoimmune response and immune tolerance of a patient. Moreover, changes in pDCs/mDCs during treatment might be a promising marker to predict the efficacy of a specific drug used for MG patients.

Human Intestinal Dendritic Cells in Inflammatory Bowel Diseases

Inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis, is a serious, costly, and persistent health problem with an estimated prevalence in Western countries around 0.5% of the general population; its socioeconomic impact is comparable with that for chronic diseases such as diabetes. Conventional treatment involves escalating drug regimens with concomitant side effects followed, in some cases, by surgical interventions, which are often multiple, mainly in Crohn's disease. The goal of finding a targeted gut-specific immunotherapy for IBD patients is therefore an important unmet need. However, to achieve this goal we first must understand how dendritic cells (DC), the most potent antigen present cells of the immune system, control the immune tolerance in the gastrointestinal tract and how their properties are altered in those patients suffering from IBD. In this review, we summarize the current available information regarding human intestinal DC subsets composition, phenotype, and function in the human gastrointestinal tract describing how, in the IBD mucosa, DC display pro-inflammatory properties, which drive disease progression. A better understanding of the mechanisms inducing DC abnormal profile in IBD may provide us with novel tools to perform tissue specific immunomodulation.

The diversity of myeloid immune cells shaping wound repair and fibrosis in the lung

In healthy circumstances the immune system coordinates tissue repair responses in a tight balance that entails efficient inflammation for removal of potential threats, proper wound closure, and regeneration to regain tissue function. Pathological conditions, continuous exposure to noxious agents, and even ageing can dysregulate immune responses after injury. This dysregulation can lead to a chronic repair mechanism known as fibrosis. Alterations in wound healing can occur in many organs, but our focus lies with the lung as it requires highly regulated immune and repair responses with its continuous exposure to airborne threats. Dysregulated repair responses can lead to pulmonary fibrosis but the exact reason for its development is often not known. Here, we review the diversity of innate immune cells of myeloid origin that are involved in tissue repair and we illustrate how these cell types can contribute to the development of pulmonary fibrosis. Moreover, we briefly discuss the effect of age on innate immune responses and therefore on wound healing and we conclude with the implications of current knowledge on the avenues for future research.

Aging, inflammation, immunity and periodontal disease

The increased prevalence and severity of periodontal disease have long been associated with aging, such that this oral condition affects the majority of the adult population over 50 years of age. Although the immune system is a critical component for maintaining health, aging can be characterized by quantitative and qualitative modifications of the immune system. This process, termed 'immunosenescence', is a progressive modification of the immune system that leads to greater susceptibility to infections, neoplasia and autoimmunity, presumably reflecting the prolonged antigenic stimulation and/or stress responses that occur across the lifespan. Interestingly, the global reduction in the host capability to respond effectively to these challenges is coupled with a progressive increase in the general proinflammatory status, termed 'inflammaging'. Consistent with the definition of immunosenescence, it has been suggested that the cumulative effect of prolonged exposure of the periodontium to microbial challenge is, at least in part, a contributor to the effects of aging on these tissues. Thus, it has also been hypothesized that alterations in the function of resident immune and nonimmune cells of the periodontium contribute to the expression of inflammaging in periodontal disease. Although the majority of aging research has focused on the adaptive immune response, it is becoming increasingly clear that the innate immune compartment is also highly affected by aging. Thus, the phenomenon of immunosenescence and inflammaging, expressed as age-associated changes within the periodontium, needs to be more fully understood in this era of precision and personalized medicine and dentistry.

Radiation- and Age-Associated Changes in Peripheral Blood Dendritic Cell Populations among Aging Atomic Bomb Survivors in Japan

Previous immunological studies in atomic bomb survivors have suggested that radiation exposure leads to long-lasting changes, similar to immunological aging observed in T-cell-adaptive immunity. However, to our knowledge, late effects of radiation on dendritic cells (DCs), the key coordinators for activation and differentiation of T cells, have not yet been investigated in humans. In the current study, we hypothesized that numerical and functional decreases would be observed in relationship to radiation dose in circulating conventional DCs (cDCs) and plasmacytoid DCs (pDCs) among 229 Japanese A-bomb survivors. Overall, the evidence did not support this hypothesis, with no overall changes in DCs or functional changes observed with radiation dose. Multivariable regression analysis for radiation dose, age and gender effects revealed that total DC counts as well as subpopulation counts decreased in relationship to increasing age. Further analyses revealed that in women, absolute numbers of pDCs showed significant decreases with radiation dose. A hierarchical clustering analysis of gene expression profiles in DCs after Toll-like receptor stimulation in vitro identified two clusters of participants that differed in age-associated expression levels of genes involved in antigen presentation and cytokine/chemokine production in cDCs. These results suggest that DC counts decrease and expression levels of gene clusters change with age. More than 60 years after radiation exposure, we also observed changes in pDC counts associated with radiation, but only among women.

Postnatal Innate Immune Development: From Birth to Adulthood

It is well established that adaptive immune responses are deficient in early life, contributing to increased mortality and morbidity. The developmental trajectories of different components of innate immunity are only recently being explored. Individual molecules, cells, or pathways of innate recognition and signaling, within different compartments/anatomical sites, demonstrate variable maturation patterns. Despite some discrepancies among published data, valuable information is emerging, showing that the developmental pattern of cytokine responses during early life is age and toll-like receptor specific, and may be modified by genetic and environmental factors. Interestingly, specific environmental exposures have been linked both to innate function modifications and the occurrence of chronic inflammatory disorders, such as respiratory allergies. As these conditions are on the rise, our knowledge on innate immune development and its modulating factors needs to be expanded. Improved understanding of the sequence of events associated with disease onset and persistence will lead toward meaningful interventions. This review describes the state-of-the-art on normal postnatal innate immune ontogeny and highlights research areas that are currently explored or should be further addressed.

Pneumococcal Capsular Polysaccharide Immunity in the Elderly

Immunity to pneumococcal infections is impaired in older people, and current vaccines are poorly protective against pneumococcal disease in this population. Naturally acquired immunity to pneumococcal capsular polysaccharides develops during childhood and is robust in young adults but deteriorates with advanced age. In particular, antibody levels and function are reduced in older people. Pneumococcal vaccines are recommended for people >65 years old. However, the benefits of polysaccharide and protein-conjugated vaccines in this population are small, because of both serotype replacement and incomplete protection against vaccine serotype pneumococcal disease. In this review, we overview the immune mechanisms by which naturally acquired and vaccine-induced pneumococcal capsular polysaccharide immunity declines with age, including altered colonization dynamics, reduced opsonic activity of antibodies (particularly IgM), and impaired mucosal immunity.

Gag-Specific CD4 T Cell Proliferation, Plasmacytoid Dendritic Cells, and Ethnicity in Perinatally HIV-1-Infected Youths: The ANRS-EP38-IMMIP Study

In perinatally HIV-1-infected youths living in France, we previously reported that Gag-specific CD4 and CD8 T cell proliferation is more frequently detected in patients of black ethnicity than in those of other ethnicities. We observed that black patients had higher levels of dendritic cells (DCs) than other patients. We aimed at studying the association of DC levels with Gag-specific T cell proliferation. The ANRS-EP38-IMMIP study is an observational study of youths aged between 15 and 24 years who were perinatally infected with HIV. A single blood sample was drawn for virological and immunological assays. Data from cART-treated 53 youths with undetectable plasma HIV RNA were analyzed. Gag-specific T cell proliferation was assessed by using a CFSE-based test. Peripheral blood myeloid dendritic cells (mDCs) and plasmacytoid dendritic cells (pDCs) were phenotyped by flow cytometry. Plasma markers were quantified by ELISA or multiplex assays. Logistic regression was used for univariate and multivariate analyses. Patients with Gag-specific CD4 T cell proliferative responses had significantly higher percentages and absolute counts of mDCs and pDCs in the peripheral blood than nonresponding patients. Gag-specific CD4 and CD8 T cell proliferation was associated with lower plasma sCD14 levels. Plasma levels of IFN-α, TRAIL, and chemokines involved in T cell migration to secondary lymphoid organs were not associated with T cell proliferation. Multivariate analysis confirmed the association between Gag-specific CD4 T cell proliferation and pDC levels. In conclusion, DC levels are a robust correlate of the presence of Gag-specific T cell proliferation in successfully treated youths.

Autophagy and Immune Senescence

With extension of the average lifespan, aging has become a heavy burden in society. Immune senescence is a key risk factor for many age-related diseases such as cancer and increased infections in the elderly, and hence has elicited much attention in recent years. As our body's guardian, the immune system maintains systemic health through removal of pathogens and damage. Autophagy is an important cellular 'clearance' process by which a cell internally delivers damaged organelles and macromolecules to lysosomes for degradation. Here, we discuss the most current knowledge of how impaired autophagy can lead to cellular and immune senescence. We also provide an overview, with examples, of the clinical potential of exploiting autophagy to delay immune senescence and/or rejuvenate immunity to treat various age-related diseases.

Age and gender leucocytes variances and references values generated using the standardized ONE-Study protocol

Flow cytometry is now accepted as an ideal technology to reveal changes in immune cell composition and function. However, it is also an error-prone and variable technology, which makes it difficult to reproduce findings across laboratories. We have recently developed a strategy to standardize whole blood flow cytometry. The performance of our protocols was challenged here by profiling samples from healthy volunteers to reveal age- and gender-dependent differences and to establish a standardized reference cohort for use in clinical trials. Whole blood samples from two different cohorts were analyzed (first cohort: n = 52, second cohort: n = 46, both 20-84 years with equal gender distribution). The second cohort was run as a validation cohort by a different operator. The "ONE Study" panels were applied to analyze expression of >30 different surface markers to enumerate proportional and absolute numbers of >50 leucocyte subsets. Indeed, analysis of the first cohort revealed significant age-dependent changes in subsets e.g. increased activated and differentiated CD4(+) and CD8(+) T cell subsets, acquisition of a memory phenotype for Tregs as well as decreased MDC2 and Marginal Zone B cells. Males and females showed different dynamics in age-dependent T cell activation and differentiation, indicating faster immunosenescence in males. Importantly, although both cohorts consisted of a small sample size, our standardized approach enabled validation of age-dependent changes with the second cohort. Thus, we have proven the utility of our strategy and generated reproducible reference ranges accounting for age- and gender-dependent differences, which are crucial for a better patient monitoring and individualized therapy. © 2016 International Society for Advancement of Cytometry.