Complement activation induces excessive T cell cytotoxicity in severe COVID-19.

Severe COVID-19 is linked to both dysfunctional immune response and unrestrained immunopathology, and it remains unclear whether T cells contribute to disease pathology. Here, we combined single-cell transcriptomics and single-cell proteomics with mechanistic studies to assess pathogenic T cell functions and inducing signals. We identified highly activated CD16+ T cells with increased cytotoxic functions in severe COVID-19. CD16 expression enabled immune-complex-mediated, T cell receptor-independent degranulation and cytotoxicity not found in other diseases. CD16+ T cells from COVID-19 patients promoted microvascular endothelial cell injury and release of neutrophil and monocyte chemoattractants. CD16+ T cell clones persisted beyond acute disease maintaining their cytotoxic phenotype. Increased generation of C3a in severe COVID-19 induced activated CD16+ cytotoxic T cells. Proportions of activated CD16+ T cells and plasma levels of complement proteins upstream of C3a were associated with fatal outcome of COVID-19, supporting a pathological role of exacerbated cytotoxicity and complement activation in COVID-19.

SARS-CoV-2-reactive T cells in healthy donors and patients with COVID-19.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused the rapidly unfolding coronavirus disease 2019 (COVID-19) pandemic1,2. Clinical manifestations of COVID-19 vary, ranging from asymptomatic infection to respiratory failure. The mechanisms that determine such variable outcomes remain unresolved. Here we investigated CD4+ T cells that are reactive against the spike glycoprotein of SARS-CoV-2 in the peripheral blood of patients with COVID-19 and SARS-CoV-2-unexposed healthy donors. We detected spike-reactive CD4+ T cells not only in 83% of patients with COVID-19 but also in 35% of healthy donors. Spike-reactive CD4+ T cells in healthy donors were primarily active against C-terminal epitopes in the spike protein, which show a higher homology to spike glycoproteins of human endemic coronaviruses, compared with N-terminal epitopes. Spike-protein-reactive T cell lines generated from SARS-CoV-2-naive healthy donors responded similarly to the C-terminal region of the spike proteins of the human endemic coronaviruses 229E and OC43, as well as that of SARS-CoV-2. This results indicate that spike-protein cross-reactive T cells are present, which were probably generated during previous encounters with endemic coronaviruses. The effect of pre-existing SARS-CoV-2 cross-reactive T cells on clinical outcomes remains to be determined in larger cohorts. However, the presence of spike-protein cross-reactive T cells in a considerable fraction of the general population may affect the dynamics of the current pandemic, and has important implications for the design and analysis of upcoming trials investigating COVID-19 vaccines.

Comparable CD8+ T-cell responses to SARS-CoV-2 vaccination in single-cell transcriptomics of recently allogeneic transplanted patients and healthy individuals.

Despite extensive research on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination responses in healthy individuals, there is comparatively little known beyond antibody titers and T-cell responses in the vulnerable cohort of patients after allogeneic hematopoietic stem cell transplantation (ASCT). In this study, we assessed the serological response and performed longitudinal multimodal analyses including T-cell functionality and single-cell RNA sequencing combined with T cell receptor (TCR)/B cell receptor (BCR) profiling in the context of BNT162b2 vaccination in ASCT patients. In addition, these data were compared to publicly available data sets of healthy vaccinees. Protective antibody titers were achieved in 40% of patients. We identified a distorted B- and T-cell distribution, a reduced TCR diversity, and increased levels of exhaustion marker expression as possible causes for the poorer vaccine response rates in ASCT patients. Immunoglobulin heavy chain gene rearrangement after vaccination proved to be highly variable in ASCT patients. Changes in TCRα and TCRß gene rearrangement after vaccination differed from patterns observed in healthy vaccinees. Crucially, ASCT patients elicited comparable proportions of SARS-CoV-2 vaccine-induced (VI) CD8+ T-cells, characterized by a distinct gene expression pattern that is associated with SARS-CoV-2 specificity in healthy individuals. Our study underlines the impaired immune system and thus the lower vaccine response rates in ASCT patients. However, since protective vaccine responses and VI CD8+ T-cells can be induced in part of ASCT patients, our data advocate early posttransplant vaccination due to the high risk of infection in this vulnerable group.

Cutting Edge: Serum but Not Mucosal Antibody Responses Are Associated with Pre-Existing SARS-CoV-2 Spike Cross-Reactive CD4+ T Cells following BNT162b2 Vaccination in the Elderly.

Advanced age is a main risk factor for severe COVID-19. However, low vaccination efficacy and accelerated waning immunity have been reported in this age group. To elucidate age-related differences in immunogenicity, we analyzed human cellular, serological, and salivary SARS-CoV-2 spike glycoprotein-specific immune responses to the BNT162b2 COVID-19 vaccine in old (69-92 y) and middle-aged (24-57 y) vaccinees compared with natural infection (COVID-19 convalescents, 21-55 y of age). Serological humoral responses to vaccination excee-ded those of convalescents, but salivary anti-spike subunit 1 (S1) IgA and neutralizing capacity were less durable in vaccinees. In old vaccinees, we observed that pre-existing spike-specific CD4+ T cells are associated with efficient induction of anti-S1 IgG and neutralizing capacity in serum but not saliva. Our results suggest pre-existing SARS-CoV-2 cross-reactive CD4+ T cells as a predictor of an efficient COVID-19 vaccine-induced humoral immune response in old individuals.

Legitimacy, Shared Understanding and Exchange of Resources: Co-managing Lakes Along an Urban-Rural Gradient in Greater Bengaluru Metropolitan Region, India.

Co-management is increasingly seen as a way forward in natural resource management and collective goods provisioning, especially in the management of urban commons. Co-management entails sharing of power between actors, including elements such as exchange of information and resources as well as changes in regulations favouring the development of common goals among actors. In this paper, we try to understand if and how preconditions of legitimacy, shared understanding and exchange of resources combine to facilitate the co-management of lakes in Greater Bengaluru Metropolitan Region (GBMR), India. To understand these issues, we undertook an exploratory, qualitative analysis of the governance of three lakes located within a single watershed placed along an urban-rural gradient. We provide an exploratory assessment of co-management across the cases situated in diverse contexts, highlighting the importance of heterogeneity of socio-economic settings for co-management of lakes. Community involvement in co-management varies with heterogeneity, correspondingly increasing transaction costs. In urbanising contexts, state actors have started to recognise the political efficacy of non-state actors mobilising knowledge and financial resources for lake management. Involvement of the state custodian and third-sector organisations (NGOs) was found to be crucial in developing and facilitating shared understanding. Deliberation between mutually dependent state and non-state actors was key to overcoming scepticism in order to realign actor perspectives. We highlight that increased acceptance of community participation based on the development of a collective identity and understanding of mutual dependence observed in our urban and rural cases reduced transaction costs and thus enabled co-management.

The microRNA miR-182 is induced by IL-2 and promotes clonal expansion of activated helper T lymphocytes.

After being activated by antigen, helper T lymphocytes switch from a resting state to clonal expansion. This switch requires inactivation of the transcription factor Foxo1, a suppressor of proliferation expressed in resting helper T lymphocytes. In the early antigen-dependent phase of expansion, Foxo1 is inactivated by antigen receptor-mediated post-translational modifications. Here we show that in the late phase of expansion, Foxo1 was no longer post-translationally regulated but was inhibited post-transcriptionally by the interleukin 2 (IL-2)-induced microRNA miR-182. Specific inhibition of miR-182 in helper T lymphocytes limited their population expansion in vitro and in vivo. Our results demonstrate a central role for miR-182 in the physiological regulation of IL-2-driven helper T cell-mediated immune responses and open new therapeutic possibilities.

SARS-CoV-2 mRNA vaccinations fail to elicit humoral and cellular immune responses in patients with multiple sclerosis receiving fingolimod.

BACKGROUND: SARS-CoV-2 mRNA vaccination of healthy individuals is highly immunogenic and protective against severe COVID-19. However, there are limited data on how disease-modifying therapies (DMTs) alter SARS-CoV-2 mRNA vaccine immunogenicity in patients with autoimmune diseases. METHODS: As part of a prospective cohort study, we investigated the induction, stability and boosting of vaccine-specific antibodies, B cells and T cells in patients with multiple sclerosis (MS) on different DMTs after homologous primary, secondary and booster SARS-CoV-2 mRNA vaccinations. Of 126 patients with MS analysed, 105 received either anti-CD20-based B cell depletion (aCD20-BCD), fingolimod, interferon-ß, dimethyl fumarate, glatiramer acetate, teriflunomide or natalizumab, and 21 were untreated MS patients for comparison. RESULTS: In contrast to all other MS patients, and even after booster, most aCD20-BCD- and fingolimod-treated patients showed no to markedly reduced anti-S1 IgG, serum neutralising activity and a lack of receptor binding domain-specific and S2-specific B cells. Patients receiving fingolimod additionally lacked spike-reactive CD4+ T cell responses. The duration of fingolimod treatment, rather than peripheral blood B and T cell counts prior to vaccination, determined whether a humoral immune response was elicited. CONCLUSIONS: The lack of immunogenicity under long-term fingolimod treatment demonstrates that functional immune responses require not only immune cells themselves, but also access of these cells to the site of inoculation and their unimpeded movement. The absence of humoral and T cell responses suggests that fingolimod-treated patients with MS are at risk for severe SARS-CoV-2 infections despite booster vaccinations, which is highly relevant for clinical decision-making and adapted protective measures, particularly considering additional recently approved sphingosine-1-phosphate receptor antagonists for MS treatment.

Selective depletion of plasma cells in vivo based on the specificity of their secreted antibodies.

Antibody-mediated diseases affect more than 10% of the human population. For most, no cure is available, particularly when the pathogenic antibodies are secreted by long-lived plasma cells resistant to conventional immunosuppressive therapies. Current therapeutic approaches target not only the plasma cells that secrete pathogenic antibodies, but also those providing protective antibodies. Here, in a murine model bearing long-lived plasma cells secreting anti-OVA and -chicken gamma globulin (CGG) antibodies, we describe the first-time use of an antigen-antibody (OVA/anti-CD138 antibody) conjugate for in vivo labeling and selective ablation of plasma cells that secrete antibodies specific for the antigen OVA. The selective depletion also led to a stable reduction of the corresponding serum anti-OVA antibody levels. In contrast, CGG-specific plasma cells and circulating anti-CGG antibody levels remained unchanged. The method described here should enable the development of unique causative treatment strategies for established antibody-mediated diseases sparing humoral immunity.

An artificial ruthenium-containing ß-barrel protein for alkene-alkyne coupling reaction.

A modified Cp*Ru complex, equipped with a maleimide group, was covalently attached to a cysteine of an engineered variant of Ferric hydroxamate uptake protein component: A (FhuA). This synthetic metalloprotein catalyzed the intermolecular alkene-alkyne coupling of 3-butenol with 5-hexynenitrile. When compared with the protein-free Cp*Ru catalyst, the biohybrid catalyst produced the linear product with higher regioselectivity.

High-dimensional single cell mass cytometry analysis of the murine hematopoietic system reveals signatures induced by ageing and physiological pathogen challenges.

BACKGROUND: Immune ageing is a result of repetitive microbial challenges along with cell intrinsic or systemic changes occurring during ageing. Mice under 'specific-pathogen-free' (SPF) conditions are frequently used to assess immune ageing in long-term experiments. However, physiological pathogenic challenges are reduced in SPF mice. The question arises to what extent murine experiments performed under SPF conditions are suited to analyze immune ageing in mice and serve as models for human immune ageing. Our previous comparisons of same aged mice with different microbial exposures, unambiguously identified distinct clusters of immune cells characteristic for numerous previous pathogen encounters in particular in pet shop mice. RESULTS: We here performed single cell mass cytometry assessing splenic as secondary and bone marrow as primary lymphoid organ-derived leukocytes isolated from young versus aged SPF mice in order to delineate alterations of the murine hematopoietic system induced during ageing. We then compared immune clusters from young and aged SPF mice to pet shop mice in order to delineate alterations of the murine hematopoietic system induced by physiological pathogenic challenges and those caused by cell intrinsic or systemic changes during ageing. Notably, distinct immune signatures were similarly altered in both pet shop and aged SPF mice in comparison to young SPF mice, including increased frequencies of memory T lymphocytes, effector-cytokine producing T cells, plasma cells and mature NK cells. However, elevated frequencies of CD4+ T cells, total NK cells, granulocytes, pDCs, cDCs and decreased frequencies of naïve B cells were specifically identified only in pet shop mice. In aged SPF mice specifically the frequencies of splenic IgM+ plasma cells, CD8+ T cells and CD4+ CD25+ Treg were increased as compared to pet shop mice and young mice. CONCLUSIONS: Our study dissects firstly how ageing impacts both innate and adaptive immune cells in primary and secondary lymphoid organs. Secondly, it partly distinguishes murine intrinsic immune ageing alterations from those induced by physiological pathogen challenges highlighting the importance of designing mouse models for their use in preclinical research including vaccines and immunotherapies.

Correction to: High-dimensional single cell mass cytometry analysis of the murine hematopoietic system reveals signatures induced by ageing and physiological pathogen challenges.

An amendment to this paper has been published and can be accessed via the original article.

Betulin Sulfonamides as Carbonic Anhydrase Inhibitors and Anticancer Agents in Breast Cancer Cells.

Hypoxia-regulated protein carbonic anhydrase IX (CA IX) is up-regulated in different tumor entities and correlated with poor prognosis in breast cancer patients. Due to the radio- and chemotherapy resistance of solid hypoxic tumors, derivatives of betulinic acid (BA), a natural compound with anticancer properties, seem to be promising to benefit these cancer patients. We synthesized new betulin sulfonamides and determined their cytotoxicity in different breast cancer cell lines. Additionally, we investigated their effects on clonogenic survival, cell death, extracellular pH, HIF-1α, CA IX and CA XII protein levels and radiosensitivity. Our study revealed that cytotoxicity increased after treatment with the betulin sulfonamides compared to BA or their precursors, especially in triple-negative breast cancer (TNBC) cells. CA IX activity as well as CA IX and CA XII protein levels were reduced by the betulin sulfonamides. We observed elevated inhibitory efficiency against protumorigenic processes such as proliferation and clonogenic survival and the promotion of cell death and radiosensitivity compared to the precursor derivatives. In particular, TNBC cells showed benefit from the addition of sulfonamides onto BA and revealed that betulin sulfonamides are promising compounds to treat more aggressive breast cancers, or are at the same level against less aggressive breast cancer cells.

MicroRNA-487a-3p functions as a new tumor suppressor in prostate cancer by targeting CCND1.

Prostate cancer (PCa) is one of the major health problems of the aging male. The roles of dysregulated microRNAs in PCa remain unclear. In this study, we mined the public published data and found that miR-487a-3p was significantly downregulated in 38 pairs of clinical prostate tumor tissues compared with the normal tissues. We further verified this result by in situ hybridization on tissue chip and quantitative real-time polymerase chain reaction (qRT-PCR) in PCa/normal cells. miR-487a-3p targeting of cyclin D1 (CCND1) was identified using bioinformatics, qRT-PCR and western blot analyses. The cellular proliferation, cell cycle, migration, and invasion were assessed by cell counting kit-8, flow cytometry analysis and transwell assay. We discovered that overexpression of miR-487a-3p suppressed PCa cell growth, migration, invasion by directly targeting CCND1. Knockdown of CCND1 in PCa cells showed similar results. Meanwhile, the expression level of CCND1 was significantly upregulated in the PCa tissues and cell lines, which presented negative correlation with the expression of miR-487a-3p. More important, we demonstrated significantly reduced growth of xenograft tumors of stable miR-487a-3p-overexpressed human PCa cells in nude mice. Taken together, for the first time, our results revealed that miR-487a-3p as a tumor suppressor of PCa could target CCND1. Our finding might reveal miR-487a-3p could be potentially contributed to the pathogenesis and a clinical biomarker or the new potential therapeutic target of PCa.

High-Pressure Crystallography as a Guide in the Design of Single-Molecule Magnets.

Single-molecule magnet materials owe their function to the presence of significant magnetic anisotropy, which arises from the interplay between the ligand field and spin-orbit coupling, and this is responsible for setting up an energy barrier for magnetic relaxation. Therefore, chemical control of magnetic anisotropy is a central challenge in the quest to synthesize new molecular nanomagnets with improved properties. There have been several reports of design principles targeting such control; however, these principles rely on idealized geometries, which are rarely obtained in crystal structures. Here, we present the results of high-pressure single-crystal diffraction on the single-ion magnet, Co(SPh)4(PPh4)2, in the pressure range of 0-9.2 GPa. Upon pressurization a sequence of small geometrical distortions of the central CoS4 moeity are observed, enabling a thorough analysis of the magneto-structural correlations. The magneto-structural correlations are investigated by theoretical analyses of the pressure-dependent experimental molecular structures. We observed a significant increase in the magnitude of the zero-field splitting parameter D, from -54.6 cm-1 to -89.7 cm-1, which was clearly explained from the reduction of the energy difference between the essential dxy and dx2-y2 orbitals, and structurally assigned to the change of an angle of compression of the CoS4 moeity.

Simultaneous Presence of Non- and Highly Mutated Keyhole Limpet Hemocyanin (KLH)-Specific Plasmablasts Early after Primary KLH Immunization Suggests Cross-Reactive Memory B Cell Activation.

There are currently limited insights into the progression of human primary humoral immunity despite numerous studies in experimental models. In this study, we analyzed a primary and related secondary parenteral keyhole limpet hemocyanin (KLH) immunization in five human adults. The primary challenge elicited discordant KLH-specific serum and blood effector B cell responses (i.e., dominant serum KLH-specific IgG and IgM levels versus dominant KLH-specific IgA plasmablast frequencies). Single-cell IgH sequencing revealed early appearance of highly (>15 mutations) mutated circulating KLH-specific plasmablasts 2 wk after primary KLH immunization, with simultaneous KLH-specific plasmablasts carrying non- and low-mutated IgH sequences. The data suggest that the highly mutated cells might originate from cross-reactive memory B cells (mBCs) rather than from the naive B cell repertoire, consistent with previous reported mutation rates and the presence of KLH-reactive mBCs in naive vaccinees prior to immunization. Whereas upon secondary immunization, serum Ab response kinetics and plasmablast mutation loads suggested the exclusive reactivation of KLH-specific mBCs, we, however, detected only little clonal overlap between the peripheral KLH-specific secondary plasmablast IgH repertoire and the primary plasmablast and mBC repertoire, respectively. Our data provide novel mechanistic insights into human humoral immune responses and suggest that primary KLH immunization recruits both naive B cells and cross-reactive mBCs, whereas secondary challenge exclusively recruits from a memory repertoire, with little clonal overlap with the primary response.

HDAC1 links early life stress to schizophrenia-like phenotypes.

Schizophrenia is a devastating disease that arises on the background of genetic predisposition and environmental risk factors, such as early life stress (ELS). In this study, we show that ELS-induced schizophrenia-like phenotypes in mice correlate with a widespread increase of histone-deacetylase 1 (Hdac1) expression that is linked to altered DNA methylation. Hdac1 overexpression in neurons of the medial prefrontal cortex, but not in the dorsal or ventral hippocampus, mimics schizophrenia-like phenotypes induced by ELS. Systemic administration of an HDAC inhibitor rescues the detrimental effects of ELS when applied after the manifestation of disease phenotypes. In addition to the hippocampus and prefrontal cortex, mice subjected to ELS exhibit increased Hdac1 expression in blood. Moreover, Hdac1 levels are increased in blood samples from patients with schizophrenia who had encountered ELS, compared with patients without ELS experience. Our data suggest that HDAC1 inhibition should be considered as a therapeutic approach to treat schizophrenia.

A longitudinal approach to biological psychiatric research: The PsyCourse study.

In current diagnostic systems, schizophrenia and bipolar disorder are still conceptualized as distinct categorical entities. Recently, both clinical and genomic evidence have challenged this Kraepelinian dichotomy. There are only few longitudinal studies addressing potential overlaps between these conditions. Here, we present design and first results of the PsyCourse study (N = 891 individuals at baseline), an ongoing transdiagnostic study of the affective-to-psychotic continuum that combines longitudinal deep phenotyping and dimensional assessment of psychopathology with an extensive collection of biomaterial. To provide an initial characterization of the PsyCourse study sample, we compare two broad diagnostic groups defined by the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) classification system, that is, predominantly affective (n = 367 individuals) versus predominantly psychotic disorders (n = 524 individuals). Depressive, manic, and psychotic symptoms as well as global functioning over time were contrasted using linear mixed models. Furthermore, we explored the effects of polygenic risk scores for schizophrenia on diagnostic group membership and addressed their effects on nonparticipation in follow-up visits. While phenotypic results confirmed expected differences in current psychotic symptoms and global functioning, both manic and depressive symptoms did not vary between both groups after correction for multiple testing. Polygenic risk scores for schizophrenia significantly explained part of the variability of diagnostic group. The PsyCourse study presents a unique resource to research the complex relationships of psychopathology and biology in severe mental disorders not confined to traditional diagnostic boundaries and is open for collaborations.

CD40L expression by CD4+ but not CD8+ T cells regulates antiviral immune responses in acute LCMV infection in mice.

CD40-CD40 ligand (CD40L) signaling plays multiple indispensable roles in cellular and humoral immunity. Impaired memory T-cell responses in the absence of CD40L have been well documented, but the requirement of this interaction for efficient priming of CD8+ T cells especially under inflammatory conditions has been under debate. In contrast to previous publications, we report here that virus-specific CD8+ T-cell responses as well as viral clearance are affected not only in the memory but also in the effector phase in CD40L-/- mice infected with lymphocytic choriomeningitis virus (LCMV) Armstrong strain. Interestingly, a considerable part of the LCMV-specific effector and memory T cells consists of CD40L+ CD8+ T cells. However, deficiency of CD40L in CD8+ T cells did influence neither the quantity nor the quality of primary T-cell responses in LCMV infection. Virus-specific CD8+ T cells in conditional knockout mice, with a selective deletion of the CD40L in CD8+ T cells, were fully functional regarding cytokine production and efficient pathogen clearance. Thus, our results unambiguously demonstrate that while CD40L is critical to generate effective primary CD8+ T-cell responses also under inflammatory conditions, CD40L expression by CD8+ T cells themselves is dispensable in acute LCMV infection.

Wild immunology assessed by multidimensional mass cytometry.

A great part of our knowledge on mammalian immunology has been established in laboratory settings. The use of inbred mouse strains enabled controlled studies of immune cell and molecule functions in defined settings. These studies were usually performed in specific-pathogen free (SPF) environments providing standardized conditions. In contrast, mammalians including humans living in their natural habitat are continuously facing pathogen encounters throughout their life. The influences of environmental conditions on the signatures of the immune system and on experimental outcomes are yet not well defined. Thus, the transferability of results obtained in current experimental systems to the physiological human situation has always been a matter of debate. Studies elucidating the diversity of "wild immunology" imprintings in detail and comparing it with those of "clean" lab mice are sparse. Here, we applied multidimensional mass cytometry to dissect phenotypic and functional differences between distinct groups of laboratory and pet shop mice as a source for "wild mice". For this purpose, we developed a 31-antibody panel for murine leukocyte subsets identification and a 35-antibody panel assessing various cytokines. Established murine leukocyte populations were easily identified and diverse immune signatures indicative of numerous pathogen encounters were classified particularly in pet shop mice and to a lesser extent in quarantine and non-SPF mice as compared to SPF mice. In addition, unsupervised analysis identified distinct clusters that associated strongly with the degree of pathogenic priming, including increased frequencies of activated NK cells and antigen-experienced B- and T-cell subsets. Our study unravels the complexity of immune signatures altered under physiological pathogen challenges and highlights the importance of carefully adapting laboratory settings for immunological studies in mice, including drug and therapy testing. © 2016 International Society for Advancement of Cytometry.

Low Thymic Activity and Dendritic Cell Numbers Are Associated with the Immune Response to Primary Viral Infection in Elderly Humans.

Immunological competence declines progressively with age, resulting in increased susceptibility of the elderly to infection and impaired responses to vaccines. Underlying mechanisms remain largely obscure as they have been related to complex, individual systemic immune properties that are challenging to investigate. In this study, we explored age-related changes in human immunity during a primary virus infection experimentally induced by immunization with live-attenuated yellow fever (YF) vaccine. Applying detailed serology, advanced FACS analysis, and systems biology, we discovered that aged subjects developed fewer neutralizing Abs, mounted diminished YF-specific CD8(+) T cell responses, and showed quantitatively and qualitatively altered YF-specific CD4(+) T cell immunity. Among numerous immune signatures, low in vivo numbers of naive CD4(+) recent thymic emigrants and peripheral dendritic cells correlated well with reduced acute responsiveness and altered long-term persistence of human cellular immunity to YF vaccination. Hence, we reveal in this article that essential elements of immune responses such as recent thymic emigrants and dendritic cells strongly relate to productive immunity in the elderly, providing a conceivable explanation for diminished responsiveness to vaccination with neoantigens and infection with de novo pathogens in the aged population.