Age-induced alterations of granulopoiesis generate atypical neutrophils that aggravate stroke pathology.

Aging accounts for increased risk and dismal outcome of ischemic stroke. Here, we investigated the impact of age-related changes in the immune system on stroke. Upon experimental stroke, compared with young mice, aged mice had increased neutrophil clogging of the ischemic brain microcirculation, leading to worse no-reflow and outcomes. Aged mice showed an enhanced granulopoietic response to stroke that led to the accumulation of CD101+CD62Llo mature and CD177hiCD101loCD62Llo and CD177loCD101loCD62Lhi immature atypical neutrophils in the blood, endowed with increased oxidative stress, phagocytosis and procoagulant features. Production of CXCL3 by CD62Llo neutrophils of the aged had a key role in the development and pathogenicity of aging-associated neutrophils. Hematopoietic stem cell rejuvenation reverted aging-associated neutropoiesis and improved stroke outcome. In elderly patients with ischemic stroke, single-cell proteome profile of blood leukocytes identified CD62Llo neutrophil subsets associated with worse reperfusion and outcome. Our results unveil how stroke in aging leads to a dysregulated emergency granulopoiesis impacting neurological outcome.

IFNγ and GM-CSF control complementary differentiation programs in the monocyte-to-phagocyte transition during neuroinflammation.

During inflammation, Ly6Chi monocytes are rapidly mobilized from the bone marrow (BM) and are recruited into inflamed tissues, where they undergo monocyte-to-phagocyte transition (MTPT). The in vivo developmental trajectories of the MTPT and the contribution of individual cytokines to this process remain unclear. Here, we used a murine model of neuroinflammation to investigate how granulocyte-macrophage colony-stimulating factor (GM-CSF) and interferon-γ (IFNγ), two type 1 cytokines, controlled MTPT. Using genetic fate mapping, gene targeting and high-dimensional single-cell multiomics analyses, we found that IFNγ was essential for the gradual acquisition of a mature inflammatory phagocyte phenotype in Ly6Chi monocytes, while GM-CSF was required to license interleukin-1ß (IL-1ß) production, phagocytosis and oxidative burst. These results suggest that the proinflammatory cytokine environment guided MTPT trajectories in the inflamed central nervous system (CNS) and indicated that GM-CSF was the most prominent target for the disarming of monocyte progenies during neuroinflammation.

Dendritic cell type 3 arises from Ly6C+ monocyte-dendritic cell progenitors.

Conventional dendritic cells (cDCs) are professional antigen-presenting cells that control the adaptive immune response. Their subsets and developmental origins have been intensively investigated but are still not fully understood as their phenotypes, especially in the DC2 lineage and the recently described human DC3s, overlap with monocytes. Here, using LEGENDScreen to profile DC vs. monocyte lineages, we found sustained expression of FLT3 and CD45RB through the whole DC lineage, allowing DCs and their precursors to be distinguished from monocytes. Using fate mapping models, single-cell RNA sequencing and adoptive transfer, we identified a lineage of murine CD16/32+CD172a+ DC3, distinct from DC2, arising from Ly6C+ monocyte-DC progenitors (MDPs) through Lyz2+Ly6C+CD11c- pro-DC3s, whereas DC2s develop from common DC progenitors (CDPs) through CD7+Ly6C+CD11c+ pre-DC2s. Corresponding DC subsets, developmental stages, and lineages exist in humans. These findings reveal DC3 as a DC lineage phenotypically related to but developmentally different from monocytes and DC2s.

Distinct immunological signatures discriminate severe COVID-19 from non-SARS-CoV-2-driven critical pneumonia.

Immune profiling of COVID-19 patients has identified numerous alterations in both innate and adaptive immunity. However, whether those changes are specific to SARS-CoV-2 or driven by a general inflammatory response shared across severely ill pneumonia patients remains unknown. Here, we compared the immune profile of severe COVID-19 with non-SARS-CoV-2 pneumonia ICU patients using longitudinal, high-dimensional single-cell spectral cytometry and algorithm-guided analysis. COVID-19 and non-SARS-CoV-2 pneumonia both showed increased emergency myelopoiesis and displayed features of adaptive immune paralysis. However, pathological immune signatures suggestive of T cell exhaustion were exclusive to COVID-19. The integration of single-cell profiling with a predicted binding capacity of SARS-CoV-2 peptides to the patients' HLA profile further linked the COVID-19 immunopathology to impaired virus recognition. Toward clinical translation, circulating NKT cell frequency was identified as a predictive biomarker for patient outcome. Our comparative immune map serves to delineate treatment strategies to interfere with the immunopathologic cascade exclusive to severe COVID-19.

Twin study reveals non-heritable immune perturbations in multiple sclerosis.

Multiple sclerosis (MS) is a chronic inflammatory disorder of the central nervous system underpinned by partially understood genetic risk factors and environmental triggers and their undefined interactions1,2. Here we investigated the peripheral immune signatures of 61 monozygotic twin pairs discordant for MS to dissect the influence of genetic predisposition and environmental factors. Using complementary multimodal high-throughput and high-dimensional single-cell technologies in conjunction with data-driven computational tools, we identified an inflammatory shift in a monocyte cluster of twins with MS, coupled with the emergence of a population of IL-2 hyper-responsive transitional naive helper T cells as MS-related immune alterations. By integrating data on the immune profiles of healthy monozygotic and dizygotic twin pairs, we estimated the variance in CD25 expression by helper T cells displaying a naive phenotype to be largely driven by genetic and shared early environmental influences. Nonetheless, the expanding helper T cells of twins with MS, which were also elevated in non-twin patients with MS, emerged independent of the individual genetic makeup. These cells expressed central nervous system-homing receptors, exhibited a dysregulated CD25-IL-2 axis, and their proliferative capacity positively correlated with MS severity. Together, our matched-pair analysis of the extended twin approach allowed us to discern genetically and environmentally determined features of an MS-associated immune signature.

GM-CSF: Master regulator of the T cell-phagocyte interface during inflammation.

The role of granulocyte-macrophage colony-stimulating factor (GM-CSF) was sequentially redefined during the past decades. Originally described as a hematopoietic growth factor for myelopoiesis, GM-CSF was recognized as a central mediator of inflammation bridging the innate and adaptive arms of the immune system. Phagocytes sensing GM-CSF adapt an inflammatory phenotype and facilitate pathogen clearance. However, in the context of chronic tissue inflammation, GM-CSF secreted by tissue-invading lymphocytes has detrimental effects by licensing tissue damage and hyperinflammation. Accordingly, therapeutic intervention at the T cell-phagocyte interface represents an attractive target to ameliorate disease progression and immunopathology. Although GM-CSF is largely dispensable for steady state myelopoiesis, dysregulation, as seen in chronic inflammatory diseases, may however lead to disrupted haematopoiesis and long-term effects on bone marrow output. Here, we will survey the role of GM-CSF during inflammation, discuss the extent to which GM-CSF-secreting T cells, debate their introduction as a separate T cell lineage and explore current and future clinical implications of GM-CSF in human disease settings.

Preexisting comorbidities shape the immune response associated with severe COVID-19.

BACKGROUND: Comorbidities are risk factors for development of severe coronavirus disease 2019 (COVID-19). However, the extent to which an underlying comorbidity influences the immune response to severe acute respiratory syndrome coronavirus 2 remains unknown. OBJECTIVE: Our aim was to investigate the complex interrelations of comorbidities, the immune response, and patient outcome in COVID-19. METHODS: We used high-throughput, high-dimensional, single-cell mapping of peripheral blood leukocytes and algorithm-guided analysis. RESULTS: We discovered characteristic immune signatures associated not only with severe COVID-19 but also with the underlying medical condition. Different factors of the metabolic syndrome (obesity, hypertension, and diabetes) affected distinct immune populations, thereby additively increasing the immunodysregulatory effect when present in a single patient. Patients with disorders affecting the lung or heart, together with factors of metabolic syndrome, were clustered together, whereas immune disorder and chronic kidney disease displayed a distinct immune profile in COVID-19. In particular, severe acute respiratory syndrome coronavirus 2-infected patients with preexisting chronic kidney disease were characterized by the highest number of altered immune signatures of both lymphoid and myeloid immune branches. This overall major immune dysregulation could be the underlying mechanism for the estimated odds ratio of 16.3 for development of severe COVID-19 in this burdened cohort. CONCLUSION: The combinatorial systematic analysis of the immune signatures, comorbidities, and outcomes of patients with COVID-19 has provided the mechanistic immunologic underpinnings of comorbidity-driven patient risk and uncovered comorbidity-driven immune signatures.

Single-cell profiling of myasthenia gravis identifies a pathogenic T cell signature.

Myasthenia gravis (MG) is an autoimmune disease characterized by impaired neuromuscular signaling due to autoantibodies targeting the acetylcholine receptor. Although its auto-antigens and effector mechanisms are well defined, the cellular and molecular drivers underpinning MG remain elusive. Here, we employed high-dimensional single-cell mass and spectral cytometry of blood and thymus samples from MG patients in combination with supervised and unsupervised machine-learning tools to gain insight into the immune dysregulation underlying MG. By creating a comprehensive immune map, we identified two dysregulated subsets of inflammatory circulating memory T helper (Th) cells. These signature ThCD103 and ThGM cells populated the diseased thymus, were reduced in the blood of MG patients, and were inversely correlated with disease severity. Both signature Th subsets rebounded in the blood of MG patients after surgical thymus removal, indicative of their role as cellular markers of disease activity. Together, this in-depth analysis of the immune landscape of MG provides valuable insight into disease pathogenesis, suggests novel biomarkers and identifies new potential therapeutic targets for treatment.

Selective killing of spinal cord neural stem cells impairs locomotor recovery in a mouse model of spinal cord injury.

BACKGROUND: Spinal cord injury (SCI) is a devastating condition mainly deriving from a traumatic damage of the spinal cord (SC). Immune cells and endogenous SC-neural stem cells (SC-NSCs) play a critical role in wound healing processes, although both are ineffective to completely restore tissue functioning. The role of SC-NSCs in SCI and, in particular, whether such cells can interplay with the immune response are poorly investigated issues, although mechanisms governing such interactions might open new avenues to develop novel therapeutic approaches. METHODS: We used two transgenic mouse lines to trace as well as to kill SC-NSCs in mice receiving SCI. We used Nestin CreERT2 mice to trace SC-NSCs descendants in the spinal cord of mice subjected to SCI. While mice carrying the suicide gene thymidine kinase (TK) along with the GFP reporter, under the control of the Nestin promoter regions (NestinTK mice) were used to label and selectively kill SC-NSCs. RESULTS: We found that SC-NSCs are capable to self-activate after SCI. In addition, a significant worsening of clinical and pathological features of SCI was observed in the NestinTK mice, upon selective ablation of SC-NSCs before the injury induction. Finally, mice lacking in SC-NSCs and receiving SCI displayed reduced levels of different neurotrophic factors in the SC and significantly higher number of M1-like myeloid cells. CONCLUSION: Our data show that SC-NSCs undergo cell proliferation in response to traumatic spinal cord injury. Mice lacking SC-NSCs display overt microglia activation and exaggerate expression of pro-inflammatory cytokines. The absence of SC-NSCs impaired functional recovery as well as neuronal and oligodendrocyte cell survival. Collectively our data indicate that SC-NSCs can interact with microglia/macrophages modulating their activation/responses and that such interaction is importantly involved in mechanisms leading tissue recovery.

Assessing the role of innovative therapeutic paradigm on multiple sclerosis treatment response.

OBJECTIVE: Within the last decade, many changes have been made to the management of patients with multiple sclerosis (MS). The aim of our study was to investigate the global impact of all these changes on the disease's course. MATERIALS AND METHODS: This single-centre study was carried out on patients with multiple sclerosis (pwMS) who started treatment with first-line disease-modifying therapies. We have compared three large cohorts of patients with MS diagnosis, for three consecutive periods within July 2001, August 2001-December 2005, and January 2006-September 2011. RESULTS: A total of 1068 relapsing-remitting pwMS cases were included. Patients in the last cohort began treatment earlier (P < 0.0001), started more frequent treatment with high-dose interferon beta or glatiramer acetate (P < 0.0001), and had experienced a more frequent treatment escalation strategy (P = 0.004) than patients in other cohorts. The multivariate analysis adjusted for baseline characteristics showed that pwMS of the last cohort had a high probability of showing no evidence of disease activity (NEDA3) at 4 years (OR 3.22, 95% CIs 1.89-5.47; P < 0.0001). These results were confirmed in a propensity score analysis. CONCLUSIONS: Our study showed an improvement over the last 15 years in the treatment response; this observation can be associated to a paradigm shift in MS treatment strategies.

GM-CSF-mediated epithelial-immune cell crosstalk orchestrates pulmonary immunity to Aspergillus fumigatus.

Aspergillus fumigatus causes life-threatening mold pneumonia in immune compromised patients, particularly in those with quantitative or qualitative defects in neutrophils. While innate immune cell crosstalk licenses neutrophil antifungal activity in the lung, the role of epithelial cells in this process is unknown. Here, we find that that surfactant protein C (SPC)-expressing lung epithelial cells integrate infection-induced IL-1 and type III interferon signaling to produce granulocyte-macrophage colony-stimulating factor (GM-CSF) preferentially at local sites of fungal infection and neutrophil influx. Using in vivo models that distinguish the role of GM-CSF during acute infection from its homeostatic function in alveolar macrophage survival and surfactant catabolism, we demonstrate that epithelial-derived GM-CSF increases the accumulation and fungicidal activity of GM-CSF-responsive neutrophils, with the latter being essential for host survival. Our findings establish SPC + epithelial cells as a central player in regulating the quality and strength of neutrophil-dependent immunity against inhaled mold pathogens. HIGHLIGHTS: GM-CSF is essential for host defense against A. fumigatus in the lung IL-1 and IFN-λ promote GM-CSF production by lung epithelial cells in parallelEpithelial cell-derived GM-CSF increases neutrophil accumulation and fungal killing capacityEpithelial cells preferentially upregulate GM-CSF in local sites of inflammation.

IL-12 sensing in neurons induces neuroprotective CNS tissue adaptation and attenuates neuroinflammation in mice.

Interleukin-12 (IL-12) is a potent driver of type 1 immunity. Paradoxically, in autoimmune conditions, including of the CNS, IL-12 reduces inflammation. The underlying mechanism behind these opposing properties and the involved cellular players remain elusive. Here we map IL-12 receptor (IL-12R) expression to NK and T cells as well as neurons and oligodendrocytes. Conditionally ablating the IL-12R across these cell types in adult mice and assessing their susceptibility to experimental autoimmune encephalomyelitis revealed that the neuroprotective role of IL-12 is mediated by neuroectoderm-derived cells, specifically neurons, and not immune cells. In human brain tissue from donors with multiple sclerosis, we observe an IL-12R distribution comparable to mice, suggesting similar mechanisms in mice and humans. Combining flow cytometry, bulk and single-nucleus RNA sequencing, we reveal an IL-12-induced neuroprotective tissue adaption preventing early neurodegeneration and sustaining trophic factor release during neuroinflammation, thereby maintaining CNS integrity in mice.

CD4+ T cells produce GM-CSF and drive immune-mediated glomerular disease by licensing monocyte-derived cells to produce MMP12.

GM-CSF in glomerulonephritisDespite glomerulonephritis being an immune-mediated disease, the contributions of individual immune cell types are not clear. To address this gap in knowledge, Paust et al. characterized pathological immune cells in samples from patients with glomerulonephritis and in samples from mice with the disease. The authors found that CD4+ T cells producing granulocyte-macrophage colony-stimulating factor (GM-CSF) licensed monocytes to promote disease by producing matrix metalloproteinase 12 and disrupting the glomerular basement membrane. Targeting GM-CSF to inhibit this axis reduced disease severity in mice, implicating this cytokine as a potential therapeutic target for patients with glomerulonephritis. -CM.

Neural stem cell transplantation in central nervous system disorders: from cell replacement to neuroprotection.

PURPOSE OF REVIEW: Transplantation of neural stem/precursor cells (NPCs) has been proposed as a promising therapeutic strategy in almost all neurological disorders characterized by the failure of central nervous system (CNS) endogenous repair mechanisms in restoring the tissue damage and rescuing the lost function. Nevertheless, recent evidence consistently challenges the limited view that transplantation of these cells is solely aimed at protecting the CNS from inflammatory and neurodegenerative damage through cell replacement. RECENT FINDINGS: Recent preclinical data confirmed that transplanted NPCs may also exert a 'bystander' neuroprotective effect and identified a series of molecules - for example, immunomodulatory substances, neurotrophic growth factors, stem cell regulators as well as guidance molecules - whose in-situ secretion by NPCs is temporally and spatially orchestrated by environmental needs. A better understanding of the molecular and cellular mechanisms sustaining this 'therapeutic plasticity' is of pivotal importance for defining crucial aspects of the bench-to-beside translation of neural stem cell therapy, that is route and timing of administration as well as the best cellular source. Further insight into those latter issues is eagerly expected from the ongoing phase I/II clinical trials, while, on the other hand, new cellular sources are being developed, mainly by exploiting the new possibilities offered by cellular reprogramming. SUMMARY: Nowadays, the research on NPC transplantation in neurological disorders is advancing on two different fronts: on one hand, recent preclinical data are uncovering the molecular basis of NPC therapeutic plasticity, offering a more solid rational framework for the design of clinical studies. On the other hand, pilot trials are highlighting the safety and feasibility issues of neural stem cell transplantation that need to be addressed before efficacy could be properly evaluated.

Single-cell profiling of immune system alterations in lymphoid, barrier and solid tissues in aged mice.

Aging exerts profound and paradoxical effects on the immune system, at once impairing proliferation, cytotoxicity and phagocytosis, and inducing chronic inflammation. Previous studies have focused on individual tissues or cell types, while a comprehensive multisystem study of tissue-resident and circulating immune populations during aging is lacking. Here we reveal an atlas of age-related changes in the abundance and phenotype of immune cell populations across 12 mouse tissues. Using cytometry-based high parametric analysis of 37 mass-cytometry and 55 spectral flow-cytometry parameters, mapping samples from young and aged animals revealed conserved and tissue-type-specific patterns of both immune atrophy and expansion. We uncovered clear phenotypic changes in both lymphoid and myeloid lineages in aged mice, and in particular a contraction in natural killer cells and plasmacytoid dendritic cells. These changes correlated with a skewing towards myelopoiesis at the expense of early lymphocyte genesis in aged mice. Taken together, this atlas represents a comprehensive, systematic and thorough resource of the age-dependent alterations of the mammalian immune system in lymphoid, barrier and solid tissues.

Delayed diagnosis in pediatric headache: an outpatient Italian survey.

OBJECTIVE: The aim of this prospective study is to assess the time lapse between the onset of recurring headache and the correct diagnosis in a cohort of pediatric patients attending an Italian children's headache center for the first time. METHODS: One hundred and one patients and parents, referred to the Pediatric Headache Centre of San Raffaele Hospital in Milan, Italy, underwent a semi-structured interview to ascertain features of headache since onset (clinical and family history, presence of childhood periodic syndromes, previously undergone instrumental exams and specialists' examinations before the correct diagnosis, past and current treatment). All patients were evaluated by expert neurologists and their headache was classified according to the International Classification of Headache Disorders II (2004). RESULTS: The median time delay from the onset of the first episode of recurrent headache to definite diagnosis was 20 months (interquartile range 12 to 36 months). A correlation with younger age and a more delayed headache diagnosis was found (r Spearman = 0.25; P = .039). An association between diagnostic delay and positive family history (median 24 months [12 to 48] vs 12 [6 to 24]; P = .014) or female gender (median 18 months [12 to 42] vs. 12 [5 to 30]; P trend = .070) was also evident. Notably, 76 out of 101 patients referred to our Center received an appropriate diagnosis according to International Classification of Headache Disorders II at the time of our visit only. Of note, up to 21% of this group were previously misdiagnosed (for epilepsy 43%, sinusitis 38%, or other diseases 19%), a fact that contributed to a longer time of clinical assessment (median 39 months) before reaching a correct diagnosis. The other group of 80 patients (79%) did not receive a specific diagnosis and treatment, and were not studied until their symptom became chronic and disabling. CONCLUSION: Pediatric headache is still under-diagnosed and not adequately considered as a health problem in the medical community as well as social settings. There is a need for educational programs regarding headache involving not only general practitioners, pediatricians, and neurologists, but also the general population. These are desirable in order to raise awareness of such a condition and, accordingly, treat children accurately.

Intratumoral IL-12 delivery empowers CAR-T cell immunotherapy in a pre-clinical model of glioblastoma.

Glioblastoma multiforme (GBM) is the most common and aggressive form of primary brain cancer, for which effective therapies are urgently needed. Chimeric antigen receptor (CAR)-based immunotherapy represents a promising therapeutic approach, but it is often impeded by highly immunosuppressive tumor microenvironments (TME). Here, in an immunocompetent, orthotopic GBM mouse model, we show that CAR-T cells targeting tumor-specific epidermal growth factor receptor variant III (EGFRvIII) alone fail to control fully established tumors but, when combined with a single, locally delivered dose of IL-12, achieve durable anti-tumor responses. IL-12 not only boosts cytotoxicity of CAR-T cells, but also reshapes the TME, driving increased infiltration of proinflammatory CD4+ T cells, decreased numbers of regulatory T cells (Treg), and activation of the myeloid compartment. Importantly, the immunotherapy-enabling benefits of IL-12 are achieved with minimal systemic effects. Our findings thus show that local delivery of IL-12 may be an effective adjuvant for CAR-T cell therapy for GBM.