Trends in Discharge Rates for Acute Pulmonary Embolism in U.S. Emergency Departments.

BACKGROUND: Outpatient management of select patients with low-risk acute pulmonary embolism (PE) has been proven to be safe and effective, yet recent evidence suggests that patients are still managed with hospitalization. Few studies have assessed contemporary real-world trends in discharge rates from U.S. emergency departments (EDs) for acute PE. OBJECTIVE: To evaluate whether the proportion of discharges from EDs for acute PE changed between 2012 and 2020 and which baseline characteristics are associated with ED discharge. DESIGN: Serial cross-sectional analysis. SETTING: U.S. EDs participating in the National Hospital Ambulatory Medical Care Survey. PATIENTS: Patients with ED visits for acute PE between 2012 and 2020. MEASUREMENTS: National trends in the proportion of discharges for acute PE and factors associated with ED discharge. RESULTS: Between 2012 and 2020, there were approximately 1 635 300 visits for acute PE. Overall, ED discharge rates remained constant over time, with rates of 38.2% (95% CI, 17.9% to 64.0%) between 2012 and 2014 and 33.4% (CI, 21.0% to 49.0%) between 2018 and 2020 (adjusted risk ratio, 1.01 per year [CI, 0.89 to 1.14]). No baseline characteristics, including established risk stratification scores, were predictive of an increased likelihood of ED discharge; however, patients at teaching hospitals and those with private insurance were more likely to receive oral anticoagulation at discharge. Only 35.9% (CI, 23.9% to 50.0%) of patients who were considered low-risk according to their Pulmonary Embolism Severity Index (PESI) class, 33.1% (CI, 21.6% to 47.0%) according to simplified PESI score, and 34.8% (CI, 23.3% to 48.0%) according to hemodynamic stability were discharged from the ED setting. LIMITATIONS: Cross-sectional survey design and inability to adjudicate diagnoses. CONCLUSION: In a representative nationwide sample, rates of discharge from the ED for acute PE appear to have remained constant between 2012 and 2020. Only one third of low-risk patients were discharged for outpatient management, and rates seem to have stabilized. Outpatient management of low-risk acute PE may still be largely underutilized in the United States. PRIMARY FUNDING SOURCE: None.

Sex and Racial Disparities in Peripheral Artery Disease.

Several studies have shown that women and racial and ethnic minority patients are at increased risk of developing lower extremity peripheral artery disease and suffering adverse outcomes from it, but a knowledge gap remains regarding the underlying causes of these increased risks. Both groups are more likely to be underdiagnosed, have poorly managed contributory comorbidities, and incur disparities in treatment and management postdiagnosis. Opportunities for improvement in the care of women and racial and ethnic minorities with peripheral artery disease include increased rates of screening, higher rates of clinical suspicion (particularly in the absence of typical symptoms of intermittent claudication), and more aggressive risk factor management before and after the diagnosis of peripheral artery disease.

Long-term outcomes of peripheral atherectomy for femoropopliteal endovascular interventions.

BACKGROUND: The use of atherectomy during peripheral endovascular interventions (PVI) has increased dramatically, but data regarding its safety and effectiveness are lacking.  Aims: This study sought to determine the long-term safety of atherectomy in contemporary practice.  Methods: Medicare fee-for-service beneficiaries who underwent femoropopliteal artery PVI from 2015-2018 were identified in a 100% sample of inpatient, outpatient, and carrier file data using procedural claims codes. The primary exposure was the use of atherectomy. Inverse probability of treatment weighting was used to adjust for measured differences in patient populations. Kaplan-Meier methods and multivariable Cox proportional hazards regression were used to compare outcomes.  Results: Among 168,553 patients who underwent PVI, 59,142 (35.1%) underwent atherectomy. The mean patient age was 77.0±7.6 years, 44.9% were female, 81.9% were white, and 46.7% had chronic limb-threatening ischaemia. Over a median follow-up time of 993 days (interquartile range 319-1,377 days), atherectomy use was associated with no difference in the risk of either the composite endpoint of death and amputation (adjusted hazard ratio [aHR] 0.99, 95% confidence interval [CI]: 0.97-1.01; p=0.19) or of major adverse limb events (aHR 1.02, 95% CI: 0.99-1.05; p=0.26). Patients who underwent atherectomy had a modest reduction in the risk of subsequently undergoing amputation or surgical revascularisation (aHR 0.92, 95% CI: 0.90-0.94; p<0.01) but an increase in the risk of undergoing a subsequent PVI (aHR 1.19, 95% CI: 1.16-1.21; p<0.01). CONCLUSIONS: The use of atherectomy during femoropopliteal artery PVI was not associated with an increase in the risk of long-term adverse safety outcomes among patients with peripheral artery disease.

Differences in Comorbidities Explain Black-White Disparities in Outcomes After Femoropopliteal Endovascular Intervention.

BACKGROUND: Black adults have a higher incidence of peripheral artery disease and limb amputations than White adults in the United States. Given that peripheral endovascular intervention (PVI) is now the primary revascularization strategy for peripheral artery disease, it is important to understand whether racial differences exist in PVI incidence and outcomes. METHODS: Data from fee-for-service Medicare beneficiaries ≥66 years of age from 2016 to 2018 were evaluated to determine age- and sex-standardized population-level incidences of femoropopliteal PVI among Black and White adults over the 3-year study period. Patients' first inpatient or outpatient PVIs were identified through claims codes. Age- and sex-standardized risks of the composite outcome of death and major amputation within 1 year of PVI were examined by race. RESULTS: Black adults underwent 928 PVIs per 100 000 Black beneficiaries compared with 530 PVIs per 100 000 White beneficiaries (risk ratio, 1.75 [95% CI, 1.73-1.77]; P<0.01). Black adults who underwent PVI were younger (mean age, 74.5 years versus 76.4 years; P<0.01), were more likely to be female (52.8% versus 42.7%; P<0.01), and had a higher burden of diabetes (70.6% versus 56.0%; P<0.01), chronic kidney disease (67.5% versus 56.6%; P<0.01), and heart failure (47.4% versus 41.7%; P<0.01) than White adults. When analyzed by indication for revascularization, Black adults were more likely to undergo PVI for chronic limb-threatening ischemia than White adults (13 023 per 21 352 [61.0%] versus 59 956 per 120 049 [49.9%]; P<0.01). There was a strong association between Black race and the composite outcome at 1 year (odds ratio, 1.21 [95% CI, 1.16-1.25]). This association persisted after adjustment for socioeconomic status (odds ratio, 1.08 [95% CI, 1.03-1.13]) but was eliminated after adjustment for comorbidities (odds ratio, 0.96 [95% CI, 0.92-1.01]). CONCLUSIONS: Among fee-for-service Medicare beneficiaries, Black adults had substantially higher population-level PVI incidence and were significantly more likely to experience adverse events after PVI than White adults. The association between Black race and adverse outcomes appears to be driven by a higher burden of comorbidities. This analysis emphasizes the critical need for early identification and aggressive management of peripheral artery disease risk factors and comorbidities to reduce Black-White disparities in the development and progression of peripheral artery disease and the risk of adverse events after PVI.

Risk Stratification and Management of Extracranial Carotid Artery Disease.

Stroke is the fifth leading cause of death in the United States and is a leading cause of disability. Extracranial internal carotid artery stenosis is a major cause of ischemic stroke, as it is estimated to cause 8% to 15% of ischemic strokes. It is critical to improve our strategies for stroke prevention and treatment in order to reduce the burden of this disease. Herein, we review approaches for the diagnosis and risk stratification of carotid artery disease as well as interventional strategies for the prevention and treatment of strokes caused by carotid artery disease.

The Safety of Paclitaxel-Coated Devices for Patients with Peripheral Artery Disease.

PURPOSE OF REVIEW: Peripheral artery disease (PAD) is a common, debilitating disease that impacts 8.5 million Americans and carries a poor prognosis. The most common manifestation of lower extremity PAD is claudication-a condition which significantly reduces quality of life and functional status. Paclitaxel-coated balloons and stents (PCBs and PESs) represented a breakthrough in the ability to treat medication-refractory patients relative to bare metal stents (BMSs) and percutaneous transluminal angioplasty (PTA) because they improve primary patency rates, reduce target lesion revascularization (TLR), and minimize late-lumen loss for femoropopliteal lesions. As a result, paclitaxel-coated devices (PCDs) were swiftly established as the standard of care for revascularization of femoropopliteal artery disease. A recent meta-analysis of summary-level data demonstrated a late mortality signal for patients treated with paclitaxel-coated devices relative to uncoated devices. This has had a major impact on the vascular community and for the treatment of patients with PAD. Herein, we provide a detailed review of the available data on the late mortality signal associated with paclitaxel. RECENT FINDINGS: In December of 2018, Katsanos et al. J Am Heart Assoc 7: e011245, 2018) published data from randomized-controlled trials (RCTs) that demonstrated an increase in mortality at 2 and 5 years in patients treated with PCDs involving the femoropopliteal arterial segment relative to patients treated with uncoated devices. As a result of this analysis, randomized trials were stopped and the FDA sent a letter to healthcare providers recommending restriction of use of these devices to patients at the highest risk of restenosis. As additional data emerged supporting the safety of these devices, the FDA organized an advisory committee meeting to review the available data and to determine a pathway forward. The FDA concluded that there were insufficient data to make a final decision regarding the safety of PCDs. They allowed these devices to remain on the market, but with revised safety labeling and updated their letter to healthcare providers to continue to restrict use to patients at highest risk of reintervention. The FDA also called for additional long-term data, including from RCTs and real-world data. To date, an updated patient-level meta-analysis of clinical trial data, RCTs with longer-term follow-up, and large observational studies have been conducted. While meta-analyses conducted using overlapping clinical trial data have found a persistent increase in mortality for those treated with PCDs, individual industry-sponsored RCTs and large observational studies have consistently failed to detect a corresponding mortality increase. To date, no mechanism linking paclitaxel to mortality has been observed. We are currently at an impasse for drawing definitive conclusions regarding the long-term safety of paclitaxel-coated devices. As we await enrollment in ongoing clinical trials, we must proceed with making reasonable decisions for our patients' care from the available data, as these devices have important clinical implications for our patients. A critical lesson that can be learned from this controversy is that, for future device trials, committing to long-term follow-up is crucial.

Femoral-popliteal peripheral artery disease: From symptom presentation to management and treatment controversies.

Peripheral artery disease (PAD) is a common condition with increasing prevalence domestically and worldwide. Patients with PAD have a poor prognosis, as PAD is associated with high rates of myocardial infarction, ischemic stroke, and cardiovascular disease death. The primary symptom of PAD, claudication, significantly reduces quality of life and functional status and is associated with depression. In addition to several advances in medications for PAD over the last decade, endovascular device therapy has seen a significant breakthrough in the form of paclitaxel-coated devices (PCDs), which significantly reduce rates of restenosis relative to non-PCDs, a finding which has been demonstrated in numerous randomized clinical trials. After their introduction to the market in 2012 (paclitaxel-eluting stents) and 2014 (paclitaxel-coated balloons) their use surged as they replaced non-PCDs and were designated the first-line endovascular therapy by society guidelines. This trend was abruptly reversed, however, after a meta-analysis of summary-level data was published in December of 2018 that reported an elevated mortality associated with PCDs compared with non-PCDs 2-5 years after treatment. This meta-analysis has been criticized for considerable methodological flaws. The Food and Drug Administration conducted a review and concluded that insufficient data existed to make a definitive statement regarding the safety of PCDs. They called for restriction of the use of PCDs to the highest-risk patient populations. At the same time, the FDA deemed pursuing new RCTs to better evaluate PCDs unfeasible due to the high numbers of patients and long follow-up time that would be required. In this setting, real-world data emerged as a powerful source of information for the evaluation of PCDs. Real-world data offers advantages over randomized-controlled trials including expeditious access to and analysis of data and the availability of large numbers of patients. Several retrospective observational studies demonstrate no difference in long-term all-cause mortality in patients treated with PCDs relative to those treated with non-PCDs. This paclitaxel controversy has illustrated the critical role that real-world data is assuming in long-term safety monitoring of medical devices.

Clinical Impact of Contralateral Carotid Occlusion in Patients Undergoing Carotid Artery Revascularization.

BACKGROUND: The presence of a contralateral carotid occlusion (CCO) is an established high-risk feature for patients undergoing carotid endarterectomy (CEA) and is traditionally an indication for carotid artery stenting (CAS). Recent observational data have called into question whether CCO remains a high-risk feature for CEA. OBJECTIVES: The purpose of this study was to determine the clinical impact of CCO among patients undergoing CEA and CAS in a contemporary nationwide registry. METHODS: All patients undergoing CEA or CAS from 2007 to 2019 in the NCDR CARE (National Cardiovascular Data Registry Carotid Artery Revascularization and Endarterectomy) and PVI (Peripheral Vascular Intervention) registries were included. The primary exposure was the presence of CCO. The outcome was a composite of in-hospital death, stroke, and myocardial infarction. Multivariable logistic regression and inverse-probability of treatment weighting were used to compare outcomes. RESULTS: Among 58,423 patients who underwent carotid revascularization, 4,624 (7.9%) had a CCO. Of those, 68.9% (n = 3,185) underwent CAS and 31.1% (n = 1,439) underwent CEA. The average age of patients with CCO was 69.5 ± 9.7 years, 32.6% were women, 92.8% were Caucasian, 51.7% had a prior transient ischemic attack or stroke, and 45.4% presented with symptomatic disease. Over the study period, there was a 41.7% decrease in the prevalence of CCO among patients who underwent carotid revascularization (p < 0.001), but CAS remained the primary revascularization strategy. Unadjusted composite outcome rates were lower in patients with CCO after CAS (2.1%) than CEA (3.6%). Following adjustment, CCO was associated with a 71% increase in the odds of an adverse outcome after CEA (95% confidence interval: 1.27 to 2.30; p < 0.001) compared with no increase after CAS (adjusted odds ratio: 0.94; 95% confidence interval: 0.72 to 1.22; p = 0.64). CONCLUSIONS: CCO remains an important predictor of increased risk among patients undergoing CEA, but not CAS.

Sex differences in presentation, management, and outcomes among patients hospitalized with acute pulmonary embolism.

While the presence of gender disparities in cardiovascular disease have been described, there is a paucity of data regarding the impact of sex in acute pulmonary embolism (PE). We identified all patients admitted to a tertiary care hospital with acute PE between August 1, 2012 through July 1, 2018. We stratified the presenting characteristics, management, and outcomes between women and men. Of the 2031 patients admitted with acute PE, 1081 (53.2%) were women. Women were more likely to present with dyspnea (59.8% vs 52.0%, p < 0.001) and less likely to present with hemoptysis (1.9% vs 4.0%, p = 0.01). Women were older (63.8 ± 17.4 years vs 62.3 ± 15.0 years, p = 0.04), but had lower rates of myocardial infarction, liver disease, smoking history, and prior DVT. PE severity was similar between women and men (massive: 4.9% vs 3.6%; submassive: 43.9% vs 41.8%; p = 0.19), yet women were more likely to present with normal right ventricular size on a surface echocardiogram (63.2% vs 54.8%, p = 0.01). In unadjusted analyses, women were less likely to survive to discharge (92.4% vs 94.7%, p = 0.04), but after adjustment, there was no sex-based survival difference. There were no sex differences in the PE-related diagnostic studies performed, use of advanced therapies, or short-term outcomes, before and after adjustment (p > 0.05 for all). In this large PE cohort from a tertiary care institution, women had different comorbidity profiles and PE presentations compared with men. Despite these differences, there were no sex disparities in PE management or outcomes.

Neuronal defects in a human cellular model of 22q11.2 deletion syndrome.

22q11.2 deletion syndrome (22q11DS) is a highly penetrant and common genetic cause of neuropsychiatric disease. Here we generated induced pluripotent stem cells from 15 individuals with 22q11DS and 15 control individuals and differentiated them into three-dimensional (3D) cerebral cortical organoids. Transcriptional profiling across 100 days showed high reliability of differentiation and revealed changes in neuronal excitability-related genes. Using electrophysiology and live imaging, we identified defects in spontaneous neuronal activity and calcium signaling in both organoid- and 2D-derived cortical neurons. The calcium deficit was related to resting membrane potential changes that led to abnormal inactivation of voltage-gated calcium channels. Heterozygous loss of DGCR8 recapitulated the excitability and calcium phenotypes and its overexpression rescued these defects. Moreover, the 22q11DS calcium abnormality could also be restored by application of antipsychotics. Taken together, our study illustrates how stem cell derived models can be used to uncover and rescue cellular phenotypes associated with genetic forms of neuropsychiatric disease.

Paclitaxel-Based Devices for the Treatment of PAD: Balancing Clinical Efficacy with Possible Risk.

PURPOSE OF REVIEW: Paclitaxel-based endovascular devices have become the standard of care in symptomatic, medication-refractory peripheral artery disease (PAD) and in critical limb ischemia (CLI). This review examines the data on the efficacy and safety of these devices relative to standard balloon angioplasty (PTA) and bare metal stents (BMS). RECENT FINDINGS: Randomized controlled trials (RCTs) have found that peripheral devices coated with paclitaxel result in superior patency rates and decreased target lesion revascularization (TLR) compared with non-drug-coated devices. Recently, a meta-analysis of randomized controlled trials unexpectedly reported an increase in mortality in patients treated with paclitaxel-coated devices (PCDs), resulting in the pausing of ongoing trials and a warning of safety from the FDA. Observational data that has been published since this time has not supported this safety concern. PAD is a common disease that severely impacts quality and length of life. PCDs are a promising therapy for patients with PAD, offering a more effective and durable intervention when compared with traditional PTA/BMS. A meta-analysis of RCTs identified a signal of harm with these devices which has now been replicated by the FDA. However, there is significant missing data from the trials analyzed by the meta-analysis and FDA, no plausible mechanism linking paclitaxel to death, and no correlation between paclitaxel dose and mortality. Analyses in observational data have found no safety signal. An FDA panel evaluating the validity of this late-mortality signal recently adjourned, emphasizing that the available data is incomplete. PCDs will remain on the market, and an active discussion is underway for developing an approach for improved post-market surveillance, device-labeling, and cause of death adjudication.

Association of Survival With Femoropopliteal Artery Revascularization With Drug-Coated Devices.

Importance: In a recent meta-analysis of randomized clinical trials, femoropopliteal artery revascularization with paclitaxel drug-coated devices was associated with increased long-term all-cause mortality compared with non-drug-coated devices. However, to our knowledge, these findings have not been replicated in other data sources and may be subject to confounding from missing data associated with patient withdrawal and loss to follow-up. Objective: To evaluate differences in all-cause mortality between patients who were treated with drug-coated devices vs non-drug-coated devices for femoropopliteal artery revascularization. Design, Setting, and Participants: This nationwide, multicenter retrospective cohort study included 16 560 Centers for Medicare and Medicaid Services beneficiaries who were admitted for femoropopliteal artery revascularization from January 1, 2016, to December 31, 2016. All-cause mortality was analyzed through September 30, 2017. Exposures: Drug-coated devices (drug-eluting stent [DES] or drug-coated balloon [DCB]) compared with non-drug-coated devices (bare metal stent or uncoated percutaneous transluminal angioplasty balloon). Main Outcomes and Measures: The primary outcome was all-cause mortality analyzed through the end of follow-up. Results: Among 16 560 patients treated at 1883 hospitals, the mean (SD) age was 72.9 (11) years, 7734 (46.7%) were men, 12 232 (73.9%) were white, 8222 (49.7%) currently or had previously used tobacco, 9817 (59.3%) had diabetes, and 8450 (51.0%) had critical limb ischemia (CLI). Drug-coated devices were used in 5989 participants (36.2%). The median follow-up was 389 days (interquartile range, 277-508 days). Among all patients, treatment with drug-coated devices was associated with a lower cumulative incidence of all-cause mortality compared with treatment with non-drug-coated devices through 600 days postprocedure (32.5% vs 34.3%, respectively; log-rank P = .007). Similar survival trends were observed when treatment was stratified by using a DCB alone or DES with or without DCB. After multivariable adjustment, drug-coated devices were not associated with a difference in all-cause mortality compared with non-drug-coated devices (hazard ratio [HR], 0.97; 95% CI, 0.91-1.04; P = .43). These findings were consistent among those with CLI (HR, 0.93; 95% CI, 0.85-1.01; P = .09) or without CLI (HR, 0.94; 95% CI, 0.85-1.03; P = .20), and for those treated with DCB alone (HR, 0.94; 95% CI, 0.86-1.03; P = .17) or DES with or without DCB (HR, 0.97; 95% CI, 0.89-1.06; P = .48). Conclusions and Relevance: In this large nationwide analysis of Centers for Medicare and Medicaid Services beneficiaries, there was no evidence of increased all-cause mortality following femoropopliteal artery revascularization with drug-coated devices compared with non-drug-coated devices.

SHANK3 and IGF1 restore synaptic deficits in neurons from 22q13 deletion syndrome patients.

Phelan-McDermid syndrome (PMDS) is a complex neurodevelopmental disorder characterized by global developmental delay, severely impaired speech, intellectual disability, and an increased risk of autism spectrum disorders (ASDs). PMDS is caused by heterozygous deletions of chromosome 22q13.3. Among the genes in the deleted region is SHANK3, which encodes a protein in the postsynaptic density (PSD). Rare mutations in SHANK3 have been associated with idiopathic ASDs, non-syndromic intellectual disability, and schizophrenia. Although SHANK3 is considered to be the most likely candidate gene for the neurological abnormalities in PMDS patients, the cellular and molecular phenotypes associated with this syndrome in human neurons are unknown. We generated induced pluripotent stem (iPS) cells from individuals with PMDS and autism and used them to produce functional neurons. We show that PMDS neurons have reduced SHANK3 expression and major defects in excitatory, but not inhibitory, synaptic transmission. Excitatory synaptic transmission in PMDS neurons can be corrected by restoring SHANK3 expression or by treating neurons with insulin-like growth factor 1 (IGF1). IGF1 treatment promotes formation of mature excitatory synapses that lack SHANK3 but contain PSD95 and N-methyl-D-aspartate (NMDA) receptors with fast deactivation kinetics. Our findings provide direct evidence for a disruption in the ratio of cellular excitation and inhibition in PMDS neurons, and point to a molecular pathway that can be recruited to restore it.

Lineage tracing and cell ablation identify a post-Aire-expressing thymic epithelial cell population.

Thymic epithelial cells in the medulla (mTECs) play a critical role in enforcing central tolerance through expression and presentation of tissue-specific antigens (TSAs) and deletion of autoreactive thymocytes. TSA expression requires autoimmune regulator (Aire), a transcriptional activator present in a subset of mTECs characterized by high CD80 and major histocompatibility complex II expression and a lack of potential for differentiation or proliferation. Here, using an Aire-DTR transgenic line, we show that short-term ablation specifically targets Aire(+) mTECs, which quickly undergo RANK-dependent recovery. Repeated ablation also affects Aire(-) mTECs, and using an inducible Aire-Cre fate-mapping system, we find that this results from the loss of a subset of mTECs that showed prior expression of Aire, maintains intermediate TSA expression, and preferentially migrates toward the center of the medulla. These results clearly identify a distinct stage of mTEC development and underscore the diversity of mTECs that play a key role in maintaining tolerance.

Extrathymic Aire-expressing cells are a distinct bone marrow-derived population that induce functional inactivation of CD4⁺ T cells.

The autoimmune regulator (Aire) is essential for prevention of autoimmunity; its role is best understood in the thymus, where it promotes self-tolerance through tissue-specific antigen (TSA) expression. Recently, extrathymic Aire-expressing cells (eTACs) have been described in murine secondary lymphoid organs, but the identity of such cells and their role in immune tolerance remains unclear. Here we have shown that eTACs are a discrete major histocompatibility complex class II (MHC II)(hi), CD80(lo), CD86(lo), epithelial cell adhesion molecule (EpCAM)(hi), CD45(lo) bone marrow-derived peripheral antigen-presenting cell (APC) population. We also have demonstrated that eTACs can functionally inactivate CD4⁺ T cells through a mechanism that does not require regulatory T cells (Treg) and is resistant to innate inflammatory stimuli. Together, these findings further define eTACs as a distinct tolerogenic cell population in secondary lymphoid organs.

Effector mechanisms of the autoimmune syndrome in the murine model of autoimmune polyglandular syndrome type 1.

Mutations in the Aire gene result in a clinical phenomenon known as Autoimmune Polyglandular Syndrome (APS) Type I, which classically manifests as a triad of adrenal insufficiency, hypoparathyroidism, and chronic mucocutaneous infections. In addition to this triad, a number of other autoimmune diseases have been observed in APS1 patients including Sjögren's syndrome, vitiligo, alopecia, uveitis, and others. Aire-deficient mice, the animal model for APS1, have highlighted the role of the thymus in the disease process and demonstrated a failure in central tolerance in aire-deficient mice. However, autoantibodies have been observed against multiple organs in both mice and humans, making it unclear what the specific role of B and T cells are in the pathogenesis of disease. Using the aire-deficient mouse as a preclinical model for APS1, we have investigated the relative contribution of specific lymphocyte populations, with the goal of identifying the cell populations which may be targeted for rational therapeutic design. In this study, we show that T cells are indispensable to the breakdown of self-tolerance, in contrast to B cells which play a more limited role in autoimmunity. Th1 polarized CD4(+) T cells, in particular, are major contributors to the autoimmune response. With this knowledge, we go on to use therapies targeted at T cells to investigate their ability to modulate disease in vivo. Depletion of CD4(+) T cells using a neutralizing Ab ameliorated the disease process. Thus, therapies targeted specifically at the CD4(+) T cell subset may help control autoimmune disease in patients with APS1.