Advanced age and female sex protect cerebral arteries from mitochondrial depolarization and apoptosis during acute oxidative stress.

Aging increases reactive oxygen species (ROS) which can impair vascular function and contribute to brain injury. However, aging can also promote resilience to acute oxidative stress. Therefore, we tested the hypothesis that advanced age protects smooth muscle cells (SMCs) and endothelial cells (ECs) of posterior cerebral arteries (PCAs; diameter, ∼80 µm) during exposure to H2O2. PCAs from young (4-6 months) and old (20-26 months) male and female C57BL/6 mice were isolated and pressurized (~70 mm Hg) to evaluate cell death, mitochondrial membrane potential (ΔΨm), ROS production, and [Ca2+]i in response to H2O2 (200 µM, 50 min). SMC death and ΔΨm depolarization were greater in PCAs from males vs. females. Aging increased ROS in PCAs from both sexes but increased SMC resilience to death only in males. Inhibiting TRPV4 channels with HC-067047 (1 µM) or Src kinases with SU6656 (10 µM) reduced Ca2+ entry and SMC death to H2O2 most effectively in PCAs from young males. Activating TRPV4 channels with GSK1016790A (50 nM) evoked greater Ca2+ influx in SMCs and ECs of PCAs from young vs. old mice but did not induce cell death. However, when combined with H2O2, TRPV4 activation exacerbated EC death. Activating Src kinases with spermidine (100 µM) increased Ca2+ influx in PCAs from males vs. females with minimal cell death. We conclude that in males, chronic oxidative stress during aging increases the resilience of cerebral arteries, which contrasts with inherent protection in females. Findings implicate TRP channels and Src kinases as targets to limit vascular damage to acute oxidative injury.

Damage-associated cellular markers in the clinical and pathogenic profile of vaccine-induced immune thrombotic thrombocytopenia.

BACKGROUND: Adenoviral vector-based COVID-19 vaccine-induced immune thrombotic thrombocytopenia (VITT) is rare but carries significant risks of mortality and long-term morbidity. The underlying pathophysiology of severe disease is still not fully understood. The objectives were to explore the pathophysiological profile and examine for clinically informative biomarkers in patients with severe VITT. METHODS: Twenty-two hospitalized patients with VITT, 9 pre- and 21 post-ChAdOx1 vaccine controls, were recruited across England, United Kingdom. Admission blood samples were analyzed for cytokine profiles, cell death markers (lactate dehydrogenase and circulating histones), neutrophil extracellular traps, and coagulation parameters. Tissue specimens from deceased patients were analyzed. RESULTS: There were strong immune responses characterized by significant elevations in proinflammatory cytokines and T helper 1 and 2 cell activation in patients with VITT. Markers of systemic endothelial activation and coagulation activation in both circulation and organ sections were also significantly elevated. About 70% (n = 15/22) of patients met the International Society for Thrombosis and Haemostasis criteria for disseminated intravascular coagulation despite negligible changes in the prothrombin time. The increased neutrophil extracellular trap formation, in conjunction with marked lymphopenia, elevated lactate dehydrogenase, and circulating histone levels, indicates systemic immune cell injury or death. Both lymphopenia and circulating histone levels independently predicted 28-day mortality in patients with VITT. CONCLUSION: The coupling of systemic cell damage and death with strong immune-inflammatory and coagulant responses are pathophysiologically dominant and clinically relevant in severe VITT.

Differential Effects of High Fat Diets on Resilience to H2O2-Induced Cell Death in Mouse Cerebral Arteries: Role for Processed Carbohydrates.

High fat, western-style diets increase vascular oxidative stress. We hypothesized that smooth muscle cells and endothelial cells adapt during the consumption of high fat diets to become more resilient to acute oxidative stress. Male C57Bl/6J mice were fed a western-style diet high in fat and processed carbohydrates (WD), a high fat diet that induces obesity (DIO), or their respective control (CD) and standard (SD) diets for 16 weeks. Posterior cerebral arteries (PCAs) were isolated and pressurized for study. During acute exposure to H2O2 (200 µM), smooth muscle cell and endothelial cell death were reduced in PCAs from WD, but not DIO mice. WD selectively attenuated mitochondrial membrane potential depolarization and vessel wall Ca2+ influx during H2O2 exposure. Selective inhibition of transient receptor potential (TRP) V4 or TRPC3 channels reduced smooth muscle cell and endothelial cell death in concert with the vessel wall [Ca2+]i response to H2O2 for PCAs from CD mice and eliminated differences between CD and WD. Inhibiting Src kinases reduced smooth muscle cell death along with [Ca2+]i response to H2O2 only in PCAs from CD mice and eliminated differences between diets. However, Src kinase inhibition did not alter endothelial cell death. These findings indicate that consuming a WD, but not high fat alone, leads to adaptations that limit Ca2+ influx and vascular cell death during exposure to acute oxidative stress.

Re-evaluation of the risk of venous thromboembolism after COVID-19 vaccination using haematological criteria.

An elevated risk of venous thromboembolism (VTE) following a first dose of the ChAdOx1 adenovirus-vectored vaccine was found in a national epidemiological study in England using routine discharge diagnosis codes. Separately, the syndrome of vaccine-induced immune thrombotic thrombocytopenia (VITT) was identified using haematological criteria based on presence of thrombocytopenia, significantly elevated D-dimers and development of anti-PF4 antibodies. To re-evaluate risk estimates using haematological criteria, we obtained the haematology results for hospital admitted patients aged 18-64 years in 43 National Health Service trusts in England who were included in the national epidemiological study. Diagnoses were confirmed and haematological parameters obtained from local records without knowledge of vaccination status. The haematological parameters in patients admitted for a confirmed VTE following ChAdOx1 or BNT162b2 mRNA vaccination were then compared with those in a randomly selected 40% sample of unvaccinated patients with VTE. Overall, 12 (14%) of the 84 vaccinated cases had a diagnosis compatible with VITT, 11 after a first dose of ChAdOx1 and one after a first dose of BNT162b2. Thrombocytopenia (platelet count <150 × 109/L) occurred in 17 vaccinated (20%) and 4 (4%) of 108 unvaccinated patients, with all 6 cases of severe thrombocytopenia (<50 × 109/L) occurring within 42 days of a first dose of ChAdOx1. The attributable risk estimates for a cerebral venous thrombosis (CVT) or other VTE with thrombocytopenia after a first dose of ChAdOx1 vaccine were 2.82 and 9.62 per million doses respectively. However, elevated risks were also found after a first dose of ChAdOx1 for VTE without thrombocytopenia with relative incidences for CVT and other VTE of 2.67 (1.77-3.77) and 1.93 (1.57-2.35) respectively. While we identified a distinct population with features of VITT within 42 days of receiving ChAdOx1 vaccination, confirming current diagnostic criteria, we also found evidence of an increased risk of a VTE without thrombocytopenia after ChAdOx1 vaccine.

Models of care for frail older persons who present to the emergency department: A scoping review of the literature.

BACKGROUND: People aged ≥65 years comprise approximately 20 % of all emergency department (ED) presentations. Frailty amongst this cohort is common yet can go undetected. OBJECTIVE: To summarise the evidence regarding models of care for frail older people in the ED. METHODS: The Joanna Briggs Institute scoping review framework was used. Literature searches were conducted in five electronic databases published from 2009 to 2022. Original research that met the criteria: frail older people aged ≥65 years, models of care and ED were included. RESULTS: A total of thirteen articles met the criteria for inclusion in this review. These comprised four studies of frailty care models and nine studies of care models using different assessment tools to identify frail older people. Care models were comprised of various specialist team members (e.g., geriatrician/ED physician and nurse). Processes underpinning these models included tools to support clinicians in the assessment of frail older adults, particularly around functional status, comorbidities, symptom distress, quality of life, cognition/delirium, and social aspects. Outcomes of care models for frail older people included: shorter ED length of stay, lower hospital admission rates, cost savings and increased patient satisfaction rates. CONCLUSION: A variety of models, supported by a variety of assessment tools, exist to identify and guide care delivery for frail older people in the ED. Careful consideration of existing policies, guidelines and models is required before implementing new service models.

Extensive genome introgression between domestic ferret and European polecat during population recovery in Great Britain.

The European polecat (Mustela putorius) is a mammalian predator which occurs across much of Europe east to the Ural Mountains. In Great Britain, following years of persecution the range of the European polecat contracted and by the early 1900s was restricted to unmanaged forests of central Wales. The European polecat has recently undergone a population increase due to legal protection and its range now overlaps that of feral domestic ferrets (Mustela putorius furo). During this range expansion, European polecats hybridized with feral domestic ferrets producing viable offspring. Here, we carry out population-level whole-genome sequencing on 8 domestic ferrets, 19 British European polecats, and 15 European polecats from the European mainland. We used a range of population genomics methods to examine the data, including phylogenetics, phylogenetic graphs, model-based clustering, phylogenetic invariants, ABBA-BABA tests, topology weighting, and Fst. We found high degrees of genome introgression in British polecats outside their previous stronghold, even in those individuals phenotyped as "pure" polecats. These polecats ranged from presumed F1 hybrids (gamma = 0.53) to individuals that were much less introgressed (gamma = 0.2). We quantify this introgression and find introgressed genes containing Fst outliers associated with cognitive function and sight.

Endothelial cells promote smooth muscle cell resilience to H2 O2 -induced cell death in mouse cerebral arteries.

AIM: Brain injury produces reactive oxygen species (ROS). However, little is known of how acute oxidative stress affects cell survival in the cerebral vascular supply. We hypothesized that endothelial cells (ECs) are more resilient to H2 O2 and protect vascular smooth muscle cells (SMCs) during acute oxidative stress. METHODS: Mouse posterior cerebral arteries (PCAs; diameter, ~80 µm) were exposed to H2 O2 (200 µM, 50 min, 37°C). Nuclear staining identified dead and live cells of intact and endothelium-disrupted vessels. SMC [Ca2+ ]i was assessed with Fura-2 fluorescence, and superoxide production was assessed by dihydroethidium and MitoSOX fluorescence. RESULTS: In response to H2 O2 : SMC death (21%) exceeded EC death (5%) and increased following endothelial disruption (to 48%) with a corresponding increase in SMC Ca2+ entry through transient receptor potential (TRP) channels. Whereas pharmacological inhibition of TRPV4 channels prevented SMC death and reduced Ca2+ entry for intact vessels, both remained elevated following endothelial disruption. In contrast, pharmacological inhibition or genetic deletion of TRPC3 prevented SMC death and attenuated Ca2+ entry for both intact and endothelium-disrupted vessels. Inhibiting gap junctions increased EC death (to 22%) while SMC death and [Ca2+ ]i responses were attenuated by inhibiting nitric oxide synthesis or scavenging superoxide/peroxynitrite. Inhibiting NADPH oxidases also prevented SMC Ca2+ entry and death. H2 O2 increased mitochondrial ROS production while scavenging mitochondria-derived superoxide prevented SMC death but not Ca2+ entry. CONCLUSIONS: During acute exposure of cerebral arteries to acute oxidative stress, ECs are more resilient than SMCs and the endothelium may protect SMCs by reducing Ca2+ entry through TRPC3 channels.

Mind and matter: The neurological complications of thrombotic thrombocytopenic purpura.

Thrombotic thrombocytopenic purpura (TTP) is a rare and potentially fatal condition, with >90% mortality if untreated; deficiency of ADAMTS13 leads to widespread microvascular thromboses and organ injury particularly affecting organs with high shear stress, including the brain. The acute neurological complications have historically been those most feared by clinicians and synonymous with a poor prognosis. TTP, however, is no longer perceived as two extremes of acute presentation and remission, rather once diagnosed a chronic condition with the potential for a long-term symptom burden. Optimal neuroimaging timing and modality lacks consensus and as we learn more about the changes seen during the acute and chronic stages of TTP, there is scope for neuroimaging to play a greater role in guiding management and the secondary prevention of vascular disease. Reduced ADAMTS13 activity levels have been associated with increased thrombotic risk and novel therapies including caplacizumab and recombinant ADAMTS13 may offer a neuroprotective role. Given the increasing evidence of the neurocognitive and psychological disease in TTP, the importance of screening and timely intervention should not be underestimated. As more patients are surviving their initial TTP presentation, it is crucial for us to develop a greater understanding of the longer-term morbidity affecting these patients.

Myofibre injury induces capillary disruption and regeneration of disorganized microvascular networks.

Injury to skeletal muscle disrupts myofibres and their microvascular supply. While the regeneration of myofibres is well described, little is known of how the microcirculation is affected by skeletal muscle injury or its recovery during regeneration. Nevertheless, the microvasculature must also recover to restore skeletal muscle function. We aimed to define the nature of microvascular damage and time course of repair during muscle injury and regeneration induced by the myotoxin BaCl2 . To test the hypothesis that microvascular disruption occurred secondary to myofibre injury, isolated microvessels were exposed to BaCl2 or the myotoxin was injected into the gluteus maximus (GM) muscle of mice. In isolated microvessels, BaCl2 depolarized smooth muscle cells (SMCs) and endothelial cells while increasing intracellular calcium in SMCs but did not elicit death of either cell type. At 1 day post-injury (dpi) of the GM, capillary fragmentation coincided with myofibre degeneration while arteriolar and venular networks remained intact; neutrophil depletion before injury did not prevent capillary damage. Perfused capillary networks reformed by 5 dpi in association with more terminal arterioles and were dilated through 10 dpi. With no change in microvascular area or branch point number in regenerating capillary networks, fewer capillaries aligned with myofibres and were no longer organized into microvascular units. By 21 dpi, capillary orientation and microvascular unit organization were no longer different from uninjured GM. We conclude that following their disruption secondary to myofibre damage, capillaries regenerate as disorganized networks that remodel into microvascular units as regenerated myofibres mature. KEY POINTS: Skeletal muscle regenerates after injury; however, the nature of microvascular damage and repair is poorly understood. Here, the myotoxin BaCl2 , a standard experimental method of acute skeletal muscle injury, was used to investigate the response of the microcirculation to local injury of intact muscle. Intramuscular injection of BaCl2 induced capillary fragmentation with myofibre degeneration; arteriolar and venular networks remained intact. Direct exposure to BaCl2 did not kill microvascular endothelial cells or smooth muscle cells. Dilated capillary networks reformed by 5 days post-injury (dpi) in association with more terminal arterioles. Capillary orientation remained disorganized through 10 dpi. Capillaries realigned with myofibres and reorganized into microvascular units by 21 dpi, which coincides with the recovery of vasomotor control and maturation of nascent myofibres. Skeletal muscle injury disrupts its capillary supply secondary to myofibre degeneration. Reorganization of regenerating microvascular networks accompanies the recovery of blood flow regulation.

Mass spectrometric identification of immunogenic SARS-CoV-2 epitopes and cognate TCRs.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections elicit both humoral and cellular immune responses. For the prevention and treatment of COVID-19, the disease caused by SARS-CoV-2, it has become increasingly apparent that T cell responses are equally if not more important than humoral responses in mediating recovery and immune protection. One major challenge in developing T cell-based therapies for infectious and malignant diseases has been the identification of immunogenic epitopes that can elicit a meaningful T cell response. Traditionally, this has been achieved using sophisticated in silico methods to predict putative epitopes deduced from binding affinities. Our studies find that, in contrast to current convention, "immunodominant" SARS-CoV-2 peptides defined by such in silico methods often fail to elicit T cell responses recognizing naturally presented SARS-CoV-2 epitopes. We postulated that immunogenic epitopes for SARS-CoV-2 are best defined empirically by directly analyzing peptides eluted from the naturally processed peptide-major histocompatibility complex (MHC) and then validating immunogenicity by determining whether such peptides can elicit T cells recognizing SARS-CoV-2 antigen-expressing cells. Using a tandem mass spectrometry approach, we identified epitopes derived from not only structural but also nonstructural genes in regions highly conserved among SARS-CoV-2 strains, including recently recognized variants. Finally, there are no reported T cell receptor-engineered T cell technology that can redirect T cell specificity to recognize and kill SARS-CoV-2 target cells. We report here several SARS-CoV-2 epitopes defined by mass spectrometric analysis of MHC-eluted peptides, provide empiric evidence for their immunogenicity, and demonstrate engineered TCR-redirected killing.

In Silico Defined SARS-CoV2 Epitopes May Not Predict Immunogenicity to COVID19.

SARS-CoV-2 infections elicit both humoral and cellular immune responses. For the prevention and treatment of COVID19, the disease caused by SARS-CoV-2, it has become increasingly apparent that T cell responses are equally, if not more important than humoral responses in mediating recovery and immune-protection. One of the major challenges in developing T cell-based therapies for infectious and malignant diseases has been the identification of immunogenic epitopes that can elicit a meaningful T cell response. Traditionally, this has been achieved using sophisticated in silico methods to predict putative epitopes deduced from binding affinities and consensus data. Our studies find that, in contrast to current dogma, 'immunodominant' SARS-CoV-2 peptides defined by such in silico methods often fail to elicit T cell responses recognizing naturally presented SARS-CoV-2 epitopes.

Immunogenic SARS-CoV2 Epitopes Defined by Mass Spectrometry.

SARS-CoV-2 infections elicit both humoral and cellular immune responses. For the prevention and treatment of COVID19, the disease caused by SARS-CoV-2, T cell responses are important in mediating recovery and immune-protection. The identification of immunogenic epitopes that can elicit a meaningful T cell response can be elusive. Traditionally, this has been achieved using sophisticated in silico methods to predict putative epitopes; however, our previous studies find that 'immunodominant' SARS-CoV-2 peptides defined by such in silico methods often fail to elicit T cell responses recognizing SARS-CoV-2. We postulated that immunogenic epitopes for SARS-CoV-2 are best defined by directly analyzing peptides eluted from the peptide-MHC complex and then validating immunogenicity empirically by determining if such peptides can elicit T cells recognizing SARS-CoV-2 antigen-expressing cells. Using a tandem mass spectrometry approach, we identified epitopes of SARS-CoV-2 derived not only from structural but also non-structural genes in regions highly conserved among SARS-CoV-2 strains including recently recognized variants. We report here, for the first time, several novel SARS-CoV-2 epitopes from membrane glycol-protein (MGP) and non-structure protein-13 (NSP13) defined by mass-spectrometric analysis of MHC-eluted peptides, provide empiric evidence for their immunogenicity to induce T cell response. SIGNIFICANCE STATEMENT: Current state of the art uses putative epitope peptides based on in silico prediction algorithms to evaluate the T cell response among COVID-19 patients. However, none of these peptides have been tested for immunogenicity, i.e. the ability to elicit a T cell response capable of recognizing endogenously presented peptide. In this study, we used MHC immune-precipitation, acid elution and tandem mass spectrometry to define the SARS-CoV-2 immunopeptidome for membrane glycol-protein and the non-structural protein. Furthermore, taking advantage of a highly robust endogenous T cell (ETC) workflow, we verify the immunogenicity of these MS-defined peptides by in vitro generation of MGP and NSP13 peptide-specific T cells and confirm T cell recognition of MGP or NSP13 endogenously expressing cell lines.

COVID-19 and immunothrombosis: emerging understanding and clinical management.

The COVID-19 pandemic has been the most significant health crisis in recent global history. Early studies from Wuhan highlighted COVID-19-associated coagulopathy and a significant association with mortality was soon recognised. As research continues across the world, more evidence is emerging of the cross-talk between the innate immune system, coagulation activation and inflammation. Immunothrombosis has been demonstrated to play a key role in the pathophysiology of severe COVID-19, with extracellular histones and neutrophil extracellular traps detected in the plasma and cardiopulmonary tissues of critically ill patients. Targeting the components of immunothrombosis is becoming an important factor in the treatment of patients with COVID-19 infection. Recent studies report outcomes of intermediate and therapeutic anticoagulation in hospitalised patients with varying severities of COVID-19 disease, including optimal dosing and associated bleeding risks. Immunomodulatory therapies, including corticosteroids and IL-6 receptor antagonists, have been demonstrated to significantly reduce mortality in COVID-19 patients. As the pandemic continues, more studies are required to understand the driving factors and upstream mechanisms for coagulopathy and immunothrombosis in COVID-19, and thus potentially develop more targeted therapies for SARS-CoV-2 infection, both in the acute phase and in those who develop longer-term symptom burden.

Halstead Category Test sensitivity to neurocognitive deficits in prenatal alcohol exposed and cognitively impaired children.

Objective: The Halstead Category Test (HCT) has been demonstrated to be sensitive to executive dysfunction in adults and children. Children with a history of significant prenatal alcohol exposure (PAE) typically show deficits in executive functions in such areas as abstract reasoning, concept formation abilities, and cognitive flexibility. However, earlier research has not taken into account the demographic variables of age, sex, and ethnicity.Methods: Three groups of psychiatrically hospitalized children ages 9-17 years were included: Children with a history of PAE (n = 295); children with cognitive impairment but no suspected history of PAE (n = 201); and children without suspected cognitive impairment (n = 317). All children completed a series of neuropsychological tests including the HCT and the Wechsler Intelligence Scale for Children-IV (WISC-IV).Results: Children with a history of PAE and cognitively impaired children with no history of PAE produced significantly more HCT errors across all ages than the cognitively unimpaired group. There were no significant effects of ethnicity or gender. Age and Working Memory Index were negatively correlated with HCT errors.Conclusion: The findings support the use of the HCT as a sensitive measure of executive functions in both PAE and non-PAE cognitively impaired children with no evidence of gender and ethnic bias. Use of the HCT is indicated in future research to measure improvement in executive functioning among children with a history of PAE facilitated by education, rehabilitation, and other forms of training and treatment.

Hypoxia acts as an environmental cue for the human tissue-resident memory T cell differentiation program.

Tissue-resident memory T cells (TRM) provide frontline defense against infectious diseases and contribute to antitumor immunity; however, aside from the necessity of TGF-ß, knowledge regarding TRM-inductive cues remains incomplete, particularly for human cells. Oxygen tension is an environmental cue that distinguishes peripheral tissues from the circulation, and here, we demonstrate that differentiation of human CD8+ T cells in the presence of hypoxia and TGF-ß1 led to the development of a TRM phenotype, characterized by a greater than 5-fold increase in CD69+CD103+ cells expressing human TRM hallmarks and enrichment for endogenous human TRM gene signatures, including increased adhesion molecule expression and decreased expression of genes involved in recirculation. Hypoxia and TGF-ß1 synergized to produce a significantly larger population of TRM phenotype cells than either condition alone, and comparison of these cells from the individual and combination conditions revealed distinct phenotypic and transcriptional profiles, indicating a programming response to milieu rather than a mere expansion. Our findings identify a likely previously unreported cue for the TRM differentiation program and can enable facile generation of human TRM phenotype cells in vitro for basic studies and translational applications such as adoptive cellular therapy.

Apoptosis in resistance arteries induced by hydrogen peroxide: greater resilience of endothelium versus smooth muscle.

Reactive oxygen species (ROS) are implicated in cardiovascular and neurologic disorders including atherosclerosis, heart attack, stroke, and traumatic brain injury. Although oxidative stress can lead to apoptosis of vascular cells, such findings are largely based upon isolated vascular smooth muscle cells (SMCs) and endothelial cells (ECs) studied in culture. Studying intact resistance arteries, we have focused on understanding how SMCs and ECs in the blood vessel wall respond to acute oxidative stress induced by hydrogen peroxide, a ubiquitous, membrane-permeant ROS. We find that apoptosis induced by H2O2 is far greater in SMCs compared to ECs. For both cell types, apoptosis is associated with a rise in intracellular calcium concentration ([Ca2+]i) during H2O2 exposure. Consistent with their greater death, the rise in [Ca2+]i for SMCs exceeds that in ECs. Finding that disruption of the endothelium increases SMC death, we address how myoendothelial coupling and paracrine signaling attenuate apoptosis. Remarkably, conditions associated with chronic oxidative stress (advanced age, Western-style diet) protect SMCs during H2O2 exposure, as does female sex. In light of intracellular Ca2+ handling, we consider how glycolytic versus oxidative pathways for ATP production and changes in mitochondrial structure and function impact cellular resilience to H2O2-induced apoptosis. Gaining new insight into protective signaling within and between SMCs and ECs of the arterial wall can be applied to promote vascular cell survival (and recovery of blood flow) in tissues subjected to acute oxidative stress as occurs during reperfusion following myocardial infarction and thrombotic stroke.

Autistic Adults' Experiences of Camouflaging and Its Perceived Impact on Mental Health.

Background: Camouflaging (also referred to as "masking") is a commonly reported strategy used by autistic adults in everyday life to help them cope in social situations. Autistic adults report that camouflaging can have a devastating effect on mental health and well-being, yet little is known about the lived experiences of camouflaging and its impact.Methods: We designed an online survey in partnership with autistic adults, to explore the experiences of camouflaging and its impact on mental health. Participants self-reported the lifetime experience of camouflaging, where they camouflaged the frequency and length of time spent camouflaging. Four open questions allowed participants to elaborate their answers to the closed questions on frequency and length of time, and subsequently any positive and negative aspects of their experience of camouflaging. Two hundred seventy-seven autistic adults who self-reported a diagnosis of an autism spectrum condition (128 female, 78 male) or self-identified as autistic (56 female, 15 male) were included in the analysis of qualitative responses to the open-ended questions.Findings: We thematically analyzed participant answers from the open questions. Three main themes emerged. First, "dangers of camouflaging" described how the amount of time spent camouflaging led to exhaustion, isolation, poor mental and physical health, loss of identity and acceptance of self, others' unreal perceptions and expectations, and delayed diagnosis. Second, "positive aspects of camouflaging" included greater access to social spaces, and protection from harm. Camouflaging was, therefore, seen as necessary to survive in a world designed for the neurotypical majority. Third, autistic adults described being diagnosed and accepted for who they are as reasons for "why I don't need to camouflage like I used to."Conclusions: Time spent camouflaging is what seems to be most damaging for the participants' mental health. The main reason reported for needing to spend so much time camouflaging is society's lack of awareness and acceptance of autism. Lay summary: Why is this study being done?: Many autistic adults report that they need to camouflage their autistic behaviors to help them "fit in" and cope in social situations with non-autistic people. This is because society is not as aware and accepting of autistic people as it needs to be. We also know that for most autistic adults camouflaging is exhausting and damaging for their mental health. This study is important, because researchers have not studied camouflaging enough to know what it is like for autistic adults to camouflage in their everyday lives and to understand the impact that camouflaging has on their mental health.What was the purpose of this study?: We wanted to ask autistic adults about their positive and negative experiences of camouflaging. This is important because it will help professionals better understand why autistic adults camouflage, and better support the mental health needs of autistic adults. This increased understanding may also help society become more aware and accepting of autism. If this happens, autistic adults will not need to camouflage as much. Not having to camouflage as much could also help prevent and reduce mental health problems in autistic adults.What did we do?: We asked autistic adults with a clinical diagnosis and those who self-identify as autistic to complete an online survey. The survey asked questions about mental health, self-injury, suicidal thoughts, and suicidal behaviors. One part of the survey asked questions about camouflaging. If research participants said they camouflaged or masked their autistic characteristics to cope with social situations, they would then be asked about when and why they camouflage, and about the positive and negative consequences of camouflaging.What did we find?: We found that autistic people confirmed that they camouflage because of a lack of awareness and acceptance of autism in society. We also found that both autistic males and females camouflage. Although some autistic adults said that "everyone" camouflages, they thought that autistic people spent much more time than non-autistic people camouflaging in their everyday lives. Spending lots of time camouflaging was what was most damaging for autistic adults' mental health. Although most autistic adults thought that camouflaging was damaging to their mental health, some thought that it helped them too.How will knowing this help autistic adults?: Our results suggest that it is important to reduce pressure to camouflage. This could help prevent high rates of mental health problems in autistic people. Our results suggest that this can be achieved if wider society becomes more aware and accepting of autistic people. Our results also suggest that reducing pressure to camouflage could benefit everyone in society.