Obesity alters pathology and treatment response in inflammatory disease.

Decades of work have elucidated cytokine signalling and transcriptional pathways that control T cell differentiation and have led the way to targeted biologic therapies that are effective in a range of autoimmune, allergic and inflammatory diseases. Recent evidence indicates that obesity and metabolic disease can also influence the immune system1-7, although the mechanisms and effects on immunotherapy outcomes remain largely unknown. Here, using two models of atopic dermatitis, we show that lean and obese mice mount markedly different immune responses. Obesity converted the classical type 2 T helper (TH2)-predominant disease associated with atopic dermatitis to a more severe disease with prominent TH17 inflammation. We also observed divergent responses to biologic therapies targeting TH2 cytokines, which robustly protected lean mice but exacerbated disease in obese mice. Single-cell RNA sequencing coupled with genome-wide binding analyses revealed decreased activity of nuclear receptor peroxisome proliferator-activated receptor-γ (PPARγ) in TH2 cells from obese mice relative to lean mice. Conditional ablation of PPARγ in T cells revealed that PPARγ is required to focus the in vivo TH response towards a TH2-predominant state and prevent aberrant non-TH2 inflammation. Treatment of obese mice with a small-molecule PPARγ agonist limited development of TH17 pathology and unlocked therapeutic responsiveness to targeted anti-TH2 biologic therapies. These studies reveal the effects of obesity on immunological disease and suggest a precision medicine approach to target the immune dysregulation caused by obesity.

Ceramide in apoptosis and oxidative stress in allergic inflammation and asthma.

BACKGROUND: Nothing is known about the mechanisms by which increased ceramide levels in the lung contribute to allergic responses and asthma severity. OBJECTIVE: We sought to investigate the functional role of ceramide in mouse models of allergic airway disease that recapitulate the cardinal clinical features of human allergic asthma. METHODS: Allergic airway disease was induced in mice by repeated intranasal administration of house dust mite or the fungal allergen Alternaria alternata. Processes that can be regulated by ceramide and are important for severity of allergic asthma were correlated with ceramide levels measured by mass spectrometry. RESULTS: Both allergens induced massive pulmonary apoptosis and also significantly increased reactive oxygen species in the lung. Prevention of increases in lung ceramide levels mitigated allergen-induced apoptosis, reactive oxygen species, and neutrophil infiltration. In contrast, dietary supplementation of the antioxidant α-tocopherol decreased reactive oxygen species but had no significant effects on elevation of ceramide level or apoptosis, indicating that the increases in lung ceramide levels in allergen-challenged mice are not mediated by oxidative stress. Moreover, specific ceramide species were altered in bronchoalveolar lavage fluid from patients with severe asthma compared with in bronchoalveolar lavage fluid from individuals without asthma. CONCLUSION: Our data suggest that elevation of ceramide level after allergen challenge contributes to the apoptosis, reactive oxygen species generation, and neutrophilic infiltrate that characterize the severe asthmatic phenotype. Ceramide might be the trigger of formation of Creola bodies found in the sputum of patients with severe asthma and could be a biomarker to optimize diagnosis and to monitor and improve clinical outcomes in this disease.

Fluvastatin Suppresses Mast Cell and Basophil IgE Responses: Genotype-Dependent Effects.

Mast cell (MC)- and basophil-associated inflammatory diseases are a considerable burden to society. A significant portion of patients have symptoms despite standard-of-care therapy. Statins, used to lower serum cholesterol, have immune-modulating activities. We tested the in vitro and in vivo effects of statins on IgE-mediated MC and basophil activation. Fluvastatin showed the most significant inhibitory effects of the six statins tested, suppressing IgE-induced cytokine secretion among mouse MCs and basophils. The effects of fluvastatin were reversed by mevalonic acid or geranylgeranyl pyrophosphatase, and mimicked by geranylgeranyl transferase inhibition. Fluvastatin selectively suppressed key FcεRI signaling pathways, including Akt and ERK. Although MCs and basophils from the C57BL/6J mouse strain were responsive to fluvastatin, those from 129/SvImJ mice were completely resistant. Resistance correlated with fluvastatin-induced upregulation of the statin target HMG-CoA reductase. Human MC cultures from eight donors showed a wide range of fluvastatin responsiveness. These data demonstrate that fluvastatin is a potent suppressor of IgE-mediated MC activation, acting at least partly via blockade of geranyl lipid production downstream of HMG-CoA reductase. Importantly, consideration of statin use for treating MC-associated disease needs to incorporate genetic background effects, which can yield drug resistance.

Doxorubicin effect is enhanced by sphingosine-1-phosphate signaling antagonist in breast cancer.

BACKGROUND: Doxorubicin is one of the most commonly used chemotherapeutic drugs for breast cancer; however, its use is limited by drug resistance and side effects. We hypothesized that adding FTY720, a sphingosine-1-phosphate (S1P) receptor functional antagonist, to doxorubicin would potentiate its effects by suppression of drug-induced inflammation. MATERIALS AND METHODS: The Cancer Genome Atlas, Gene Expression Omnibus data sets, and National Cancer Institute-60 panel were used for gene expressions and gene set enrichment analysis. E0771 syngeneic mammary tumor cells were used. OB/OB mice fed with western high-fat diet were used as an obesity model. RESULTS: STAT3 expression was significantly increased after doxorubicin treatment in human breast cancer that implicates that doxorubicin evokes inflammation. Expression of sphingosine kinase 1, the enzyme that produces S1P and links inflammation and cancer, tended to be higher in doxorubicin-resistant human cancer and cell lines. In a murine breast cancer model, sphingosine kinase 1, S1P receptor 1, interleukin 6, and STAT3 were overexpressed in the doxorubicin-treated group, whereas all of them were significantly suppressed with addition of FTY720. Combination therapy synergistically suppressed cancer growth both in vitro and in vivo. Furthermore, combination therapy showed higher efficacy in an obesity breast cancer model, where high body mass index demonstrated trends toward worse disease-free and overall survival, and high-serum S1P levels in human patients and volunteers. CONCLUSIONS: We found that FTY720 enhanced the efficacy of doxorubicin by suppression of drug-induced inflammation, and combination therapy showed stronger effect in obesity-related breast cancer.

Aberrant ORM (yeast)-like protein isoform 3 (ORMDL3) expression dysregulates ceramide homeostasis in cells and ceramide exacerbates allergic asthma in mice.

BACKGROUND: Asthma, a chronic inflammatory condition defined by episodic shortness of breath with expiratory wheezing and cough, is a serious health concern affecting more than 250 million persons. Genome-wide association studies have identified ORM (yeast)-like protein isoform 3 (ORMDL3) as a gene associated with susceptibility to asthma. Although its yeast ortholog is a negative regulator of de novo ceramide biosynthesis, how ORMDL3 contributes to asthma pathogenesis is not known. OBJECTIVES: We sought to decipher the molecular mechanism for the pathologic functions of ORMDL3 in asthma and the relationship to its evolutionarily conserved role in regulation of ceramide homeostasis. METHODS: We determined the relationship between expression of ORMDL3 and ceramide in epithelial and inflammatory cells and in asthma pathogenesis in mice. RESULTS: Although small increases in ORMDL3 expression decrease ceramide levels, remarkably, higher expression in lung epithelial cells and macrophages in vitro and in vivo increased ceramide production, which promoted chronic inflammation, airway hyperresponsiveness, and mucus production during house dust mite-induced allergic asthma. Moreover, nasal administration of the immunosuppressant drug FTY720/fingolimod reduced ORMDL3 expression and ceramide levels and mitigated airway inflammation and hyperreactivity and mucus hypersecretion in house dust mite-challenged mice. CONCLUSIONS: Our findings demonstrate that overexpression of ORMDL3 regulates ceramide homeostasis in cells in a complex manner and suggest that local FTY720 administration might be a useful therapeutic intervention for the control of allergic asthma.

Role of sphingosine kinase 1 and sphingosine-1-phosphate in CD40 signaling and IgE class switching.

The tumor necrosis factor (TNF) receptor family member CD40 plays an essential role in the activation of antigen-presenting cells, B cell maturation, and immunoglobulin (Ig) class switching critical for adaptive immunity. Although the bioactive sphingolipid metabolite sphingosine-1-phosphate (S1P) and the kinase that produces it, sphingosine kinase 1 (SphK1), have long been implicated in the actions of TNF mediated by engagement of TNFR1, nothing is yet known of their role in CD40-mediated events. We have now found that ligation of CD40 activates and translocates SphK1 to the plasma membrane, leading to generation of S1P. SphK1 inhibition in human tonsil B cells, as well as inhibition or deletion of SphK1 in mouse splenic B cells, significantly reduced CD40-mediated Ig class switching and plasma cell differentiation ex vivo. Optimal activation of downstream CD40 signaling pathways, including NF-κB, p38, and JNK, also required SphK1. In mice treated with a SphK1 inhibitor or in SphK1(-/-) mice, isotype switching to antigen-specific IgE was decreased in vivo by 70 and 55%, respectively. Our results indicate that SphK1 is important for CD40-mediated B cell activation and regulation of humoral responses and suggest that targeting SphK1 might be a useful therapeutic approach to control antigen-specific IgE production.

Cutting edge: mast cells critically augment myeloid-derived suppressor cell activity.

Myeloid-derived suppressor cells (MDSCs) are primarily recognized for their immunosuppressive properties in malignant disease. However, their interaction with other innate immune cells and their regulation of immune responses, such as in parasitic infection, necessitate further characterization. We used our previously published mouse model of MDSC accumulation to examine the immunoregulatory role of MDSCs in B16 melanoma metastasis and Nippostrongylus brasiliensis infection. In this study, we demonstrate that the activity of MDSCs is dependent on the immune stimuli and subset induced. Monocytic MDSCs predictably suppressed antitumor immune responses but granulocytic MDSCs surprisingly enhanced the clearance of N. brasiliensis infection. Intriguingly, both results were dependent on MDSC interaction with mast cells (MCs), as demonstrated by adoptive-transfer studies in MC-deficient (Kit(Wsh)(/)(Wsh)) mice. These findings were further supported by ex vivo cocultures of MCs and MDSCs, indicating a synergistic increase in cytokine production. Thus, MCs can enhance both immunosuppressive and immunosupportive functions of MDSCs.

Emerging concepts in alcohol, infection & immunity: A summary of the 2023 alcohol and immunology research interest group (AIRIG) meeting.

On December 8th 2023, the annual Alcohol and Immunology Research Interest Group (AIRIG) meeting was held at the University of Colorado Anschutz Medical Campus in Aurora, Colorado. The 2023 meeting focused broadly on how acute and chronic alcohol exposure leads to immune dysregulation, and how this contributes to damage in multiple tissues and organs. These include impaired lung immunity, intestinal dysfunction, autoimmunity, the gut-Central Nervous System (CNS) axis, and end-organ damage. In addition, diverse areas of alcohol research covered multiple pathways behind alcohol-induced cellular dysfunction, including inflammasome activation, changes in miRNA expression, mitochondrial metabolism, gene regulation, and transcriptomics. Finally, the work presented at this meeting highlighted novel biomarkers and therapeutic interventions for patients suffering from alcohol-induced organ damage.

Unfolded Von Willebrand Factor Binds Protein S and Reduces Anticoagulant Activity.

Protein S (PS), the critical plasma cofactor for the anticoagulants tissue factor (TF) pathway inhibitor (TFPI) and activated protein C (APC), circulates in two functionally distinct pools: free (anticoagulant) or bound to complement component 4b-binding protein (C4BP) (anti-inflammatory). Acquired free PS deficiency is detected in several viral infections, but its cause is unclear. Here, we identified a shear-dependent interaction between PS and von Willebrand Factor (VWF) by mass spectrometry. Consistently, plasma PS and VWF comigrated in both native and agarose gel electrophoresis. The PS/VWF interaction was blocked by TFPI but not APC, suggesting an interaction with the C-terminal sex hormone binding globulin (SHBG) region of PS. Microfluidic systems, mimicking arterial laminar flow or disrupted turbulent flow, demonstrated that PS stably binds VWF as VWF unfolds under turbulent flow. PS/VWF complexes also localized to platelet thrombi under laminar arterial flow. In thrombin generation-based assays, shearing plasma decreased PS activity, an effect not seen in the absence of VWF. Finally, free PS deficiency in COVID-19 patients, measured using an antibody that binds near the C4BP binding site in SHBG, correlated with changes in VWF, but not C4BP, and with thrombin generation. Our data suggest that PS binds to a shear-exposed site on VWF, thus sequestering free PS and decreasing its anticoagulant activity, which would account for the increased thrombin generation potential. As many viral infections present with free PS deficiency, elevated circulating VWF, and increased vascular shear, we propose that the PS/VWF interaction reported here is a likely contributor to virus-associated thrombotic risk.

Assessment of Opioid-Induced Immunomodulation in Experimental and Clinical Sepsis.

Opioids remain a standard supportive therapy in patients admitted to the ICU with sepsis. However, as preclinical models indicate an association between opioid exposure and immunosuppression, the use of this class of drugs warrants investigation. The objective of this study was to investigate whether opioid exposure causes immunosuppression in patients with sepsis, and to use a murine sepsis model to determine the effects of opioid exposure on secondary infection. HYPOTHESIS: We hypothesized opioid exposure would be associated with immunosuppression in patients with sepsis and secondary infection in a murine sepsis model. METHODS AND MODELS: This was a two-phase preclinical and clinical study. The clinical phase included a subgroup of patients with sepsis from an existing randomized controlled trial while the preclinical phase used a murine model of sepsis with C57BL/6 mice. In the clinical phase, a post hoc analysis was performed in subjects receiving fentanyl versus no opioid receipt. In the preclinical phase, a murine cecal slurry-induced sepsis model followed by secondary infection was used. Mice were randomized to fentanyl versus no fentanyl concomitantly. RESULTS: In clinical sepsis, a significant decrease in interleukin-23 (IL-23) level in patients with fentanyl exposure was observed and lower IL-23 was associated with mortality (p < 0.001). Other measured cytokines showed no significant differences. Concomitant fentanyl exposure during murine sepsis was associated with a significantly higher bacterial burden (p < 0.001) after secondary infection; however, immune cell counts and plasma cytokine levels were largely unaffected by fentanyl. INTERPRETATION AND CONCLUSIONS: Minimal alterations in cytokines were seen with opioid exposure during clinical sepsis. In a preclinical model, opioid exposure during sepsis was associated with ineffective bacterial clearance upon secondary infection. Further studies are warranted to evaluate the immunomodulatory role of opioids and their implications, especially in the post-sepsis period.

PAI-1 as a critical factor in the resolution of sepsis and acute kidney injury in old age.

Elevated plasma levels of plasminogen activator inhibitor type 1 (PAI-1) are documented in patients with sepsis and levels positively correlate with disease severity and mortality. Our prior work demonstrated that PAI-1 in plasma is positively associated with acute kidney injury (AKI) in septic patients and mice. The objective of this study was to determine if PAI-1 is causally related to AKI and worse sepsis outcomes using a clinically-relevant and age-appropriate murine model of sepsis. Sepsis was induced by cecal slurry (CS)-injection to wild-type (WT, C57BL/6) and PAI-1 knockout (KO) mice at young (5-9 months) and old (18-22 months) age. Survival was monitored for at least 10 days or mice were euthanized for tissue collection at 24 or 48 h post-insult. Contrary to our expectation, PAI-1 KO mice at old age were significantly more sensitive to CS-induced sepsis compared to WT mice (24% vs. 65% survival, p = 0.0037). In comparison, loss of PAI-1 at young age had negligible effects on sepsis survival (86% vs. 88% survival, p = 0.8106) highlighting the importance of age as a biological variable. Injury to the kidney was the most apparent pathological consequence and occurred earlier in aged PAI-1 KO mice. Coagulation markers were unaffected by loss of PAI-1, suggesting thrombosis-independent mechanisms for PAI-1-mediated protection. In summary, although high PAI-1 levels are clinically associated with worse sepsis outcomes, loss of PAI-1 rendered mice more susceptible to kidney injury and death in a CS-induced model of sepsis using aged mice. These results implicate PAI-1 as a critical factor in the resolution of sepsis in old age.

Post-intensive care syndrome and pulmonary fibrosis in patients surviving ARDS-pneumonia of COVID-19 and non-COVID-19 etiologies.

The purpose was to examine patient-centered outcomes and the occurrence of lung fibrotic changes on Chest computed tomography (CT) imaging following pneumonia-related acute respiratory distress syndrome (ARDS). We sought to investigate outpatient clinic chest CT imaging in survivors of COVID19-related ARDS and non-COVID-related ARDS, to determine group differences and explore relationships between lung fibrotic changes and functional outcomes. A retrospective practice analysis of electronic health records at an ICU Recovery Clinic in a tertiary academic medical center was performed in adult patients surviving ARDS due to COVID-19 and non-COVID etiologies. Ninety-four patients with mean age 53 ± 13 and 51% male were included (n = 64 COVID-19 and n = 30 non-COVID groups). There were no differences for age, sex, hospital length of stay, ICU length of stay, mechanical ventilation duration, or sequential organ failure assessment (SOFA) scores between the two groups. Fibrotic changes visualized on CT imaging occurred in a higher proportion of COVID-19 survivors (70%) compared to the non-COVID group (43%, p < 0.001). Across both groups, patients with fibrotic changes (n = 58) were older, had a lower BMI, longer hospital and ICU LOS, lower mean RASS scores, longer total duration of supplemental oxygen. While not statistically different, patients with fibrotic changes did have reduced respiratory function, worse performance on the six-minute walk test, and had high occurrences of anxiety, depression, emotional distress, and mild cognitive impairment regardless of initial presenting diagnosis. Patients surviving pneumonia-ARDS are at high risk of impairments in physical, emotional, and cognitive health related to Post-Intensive Care Syndrome. Of clinical importance, pulmonary fibrotic changes on chest CT occurred in a higher proportion in COVID-ARDS group; however, no functional differences were measured in spirometry or physical assessments at ICU follow-up. Whether COVID infection imparts a unique recovery is not evident from these data but suggest that long-term follow up is necessary for all survivors of ARDS.

IL-4 and TGF-beta 1 counterbalance one another while regulating mast cell homeostasis.

Mast cell responses can be altered by cytokines, including those secreted by Th2 and regulatory T cells (Treg). Given the important role of mast cells in Th2-mediated inflammation and recent demonstrations of Treg-mast cell interactions, we examined the ability of IL-4 and TGF-beta1 to regulate mast cell homeostasis. Using in vitro and in vivo studies of mouse and human mast cells, we demonstrate that IL-4 suppresses TGF-beta1 receptor expression and signaling, and vice versa. In vitro studies demonstrated that IL-4 and TGF-beta1 had balancing effects on mast cell survival, migration, and FcepsilonRI expression, with each cytokine cancelling the effects of the other. However, in vivo analysis of peritoneal inflammation during Nippostrongylus brasiliensis infection in mice revealed a dominant suppressive function for TGF-beta1. These data support the existence of a cytokine network involving the Th2 cytokine IL-4 and the Treg cytokine TGF-beta1 that can regulate mast cell homeostasis. Dysregulation of this balance may impact allergic disease and be amenable to targeted therapy.

Simple, accurate calculation of mechanical power in pressure controlled ventilation (PCV).

BACKGROUND: Mechanical power is a promising new metric to assess energy transfer from a mechanical ventilator to a patient, which combines the contributions of multiple parameters into a single comprehensive value. However, at present, most ventilators are not capable of calculating mechanical power automatically, so there is a need for a simple equation that can be used to estimate this parameter at the bedside. For volume-controlled ventilation (VCV), excellent equations exist for calculating power from basic ventilator parameters, but for pressure-controlled ventilation (PCV), an accurate, easy-to-use equation has been elusive. RESULTS: Here, we present a new power equation and evaluate its accuracy compared to the three published PCV power equations. When applied to a sample of 50 patients on PCV with a non-zero rise time, we found that our equation estimated power within an average of 8.4% ± 5.9% (mean ± standard deviation) of the value obtained by numerical integration of the P-V loop. The other three equations estimated power with an error of 19.4% ± 12.9% (simplified Becher equation), 10.0% ± 6.8% (comprehensive Becher equation), and 16.5% ± 14.6% (van der Meijden equation). CONCLUSIONS: Our equation calculates power more accurately than the other three published equations, and is much easier to use than the only previously published equation with similar accuracy. The proposed new mechanical power equation is accurate and simple to use, making it an attractive option to estimate power in PCV cases at the bedside.

Mechanical Power: A New Concept in Mechanical Ventilation.

Mechanical ventilation is a potentially life-saving therapy for patients with acute lung injury, but the ventilator itself may cause lung injury. Ventilator-induced lung injury (VILI) is sometimes an unfortunate consequence of mechanical ventilation. It is not clear however how best to minimize VILI through adjustment of various parameters including tidal volume, plateau pressure, driving pressure, and positive end expiratory pressure (PEEP). No single parameter provides a clear indication for onset of lung injury attributable exclusively to the ventilator. There is currently interest in quantifying how static and dynamic parameters contribute to VILI. One concept that has emerged is the consideration of the amount of energy transferred from the ventilator to the respiratory system per unit time, which can be quantified as mechanical power. This review article reports on recent literature in this emerging field and future roles for mechanical power assessments in prospective studies.

Severe Acute Respiratory Syndrome-Associated Coronavirus 2 Infection and Organ Dysfunction in the ICU: Opportunities for Translational Research.

OBJECTIVES: Since the beginning of the coronavirus disease 2019 pandemic, hundreds of thousands of patients have been treated in ICUs across the globe. The severe acute respiratory syndrome-associated coronavirus 2 virus enters cells via the angiotensin-converting enzyme 2 receptor and activates several distinct inflammatory pathways, resulting in hematologic abnormalities and dysfunction in respiratory, cardiac, gastrointestinal renal, endocrine, dermatologic, and neurologic systems. This review summarizes the current state of research in coronavirus disease 2019 pathophysiology within the context of potential organ-based disease mechanisms and opportunities for translational research. DATA SOURCES: Investigators from the Research Section of the Society of Critical Care Medicine were selected based on expertise in specific organ systems and research focus. Data were obtained from searches conducted in Medline via the PubMed portal, Directory of Open Access Journals, Excerpta Medica database, Latin American and Caribbean Health Sciences Literature, and Web of Science from an initial search from December 2019 to October 15, 2020, with a revised search to February 3, 2021. The medRxiv, Research Square, and clinical trial registries preprint servers also were searched to limit publication bias. STUDY SELECTION: Content experts selected studies that included mechanism-based relevance to the severe acute respiratory syndrome-associated coronavirus 2 virus or coronavirus disease 2019 disease. DATA EXTRACTION: Not applicable. DATA SYNTHESIS: Not applicable. CONCLUSIONS: Efforts to improve the care of critically ill coronavirus disease 2019 patients should be centered on understanding how severe acute respiratory syndrome-associated coronavirus 2 infection affects organ function. This review articulates specific targets for further research.

Recovery from COVID-19 and acute respiratory distress syndrome: the potential role of an intensive care unit recovery clinic: a case report.

BACKGROUND: In this case report, we describe the trajectory of recovery of a young, healthy patient diagnosed with coronavirus disease 2019 who developed acute respiratory distress syndrome. The purpose of this case report is to highlight the potential role of intensive care unit recovery or follow-up clinics for patients surviving acute hospitalization for coronavirus disease 2019. CASE PRESENTATION: Our patient was a 27-year-old Caucasian woman with a past medical history of asthma transferred from a community hospital to our medical intensive care unit for acute hypoxic respiratory failure due to bilateral pneumonia requiring mechanical ventilation (ratio of arterial oxygen partial pressure to fraction of inspired oxygen, 180). On day 2 of her intensive care unit admission, reverse transcription-polymerase chain reaction confirmed coronavirus disease 2019. Her clinical status gradually improved, and she was extubated on intensive care unit day 5. She had a negative test result for coronavirus disease 2019 twice with repeated reverse transcription-polymerase chain reaction before being discharged to home after 10 days in the intensive care unit. Two weeks after intensive care unit discharge, the patient returned to our outpatient intensive care unit recovery clinic. At follow-up, the patient endorsed significant fatigue and exhaustion with difficulty walking, minor issues with sleep disruption, and periods of memory loss. She scored 10/12 on the short performance physical battery, indicating good physical function. She did not have signs of anxiety, depression, or post-traumatic stress disorder through self-report questionnaires. Clinically, she was considered at low risk of developing post-intensive care syndrome, but she required follow-up services to assist in navigating the healthcare system, addressing remaining symptoms, and promoting return to her pre-coronavirus disease 2019 societal role. CONCLUSION: We present this case report to suggest that patients surviving coronavirus disease 2019 with subsequent development of acute respiratory distress syndrome will require more intense intensive care unit recovery follow-up. Patients with a higher degree of acute illness who also have pre-existing comorbidities and those of older age who survive mechanical ventilation for coronavirus disease 2019 will require substantial post-intensive care unit care to mitigate and treat post-intensive care syndrome, promote reintegration into the community, and improve quality of life.

129/SvJ mice have mutated CD23 and hyper IgE.

CD23, the low affinity IgE receptor, is hypothesized to function as a negative regulator of IgE production. Upon discovering reduced CD23 surface levels in 129/SvJ inbred mice, we sought to further investigate 129/SvJ CD23 and to examine its influence on IgE levels. Five amino acid substitutions were found in 129/SvJ CD23. Identical mutations were also observed in CD23 from New Zealand Black and 129P1/ReJ mice. 129/SvJ B cells proliferated more rapidly than those from BALB/c after stimulation with IL-4 and CD40 ligand trimer. However, in vitro IgE levels in supernatants from stimulated 129/SvJ B cells were significantly reduced. Contrary to the in vitro findings, the 129/SvJ CD23 mutations correlated with a hyper IgE phenotype in vivo and 129/SvJ were able to clear Nippostrongylus brasiliensis infection more rapidly than either BALB/c or C57BL/6. Overall, this study further suggests that CD23 is an important regulatory factor for IgE production.

Mast Cells Are Mediators of Fibrosis and Effector Cell Recruitment in Dermal Chronic Graft-vs.-Host Disease.

Allogeneic hematopoietic stem cell transplant (allo-HSCT) is often used to treat acute leukemia or defects of hematopoiesis. Its widespread use is hampered by graft-vs.-host disease (GVHD), which has high morbidity and mortality in both acute and chronic subtypes. Chronic GVHD (cGVHD) occurs most frequently in skin and often is characterized by pathogenic fibrosis. Mast cells (MCs) are known to be involved in the pathogenesis of other fibrotic diseases. In a murine model of cGVHD after allo-HSCT, C57BL/6J recipients of allogeneic LP/J donor cells develop sclerodermatous dermal cGVHD which is significantly decreased in mast cell-deficient B6.Cg-KitW-sh/HNihrJaeBsmGlliJ recipients. The presence of MCs is associated with fibrosis, chemokine production, and recruitment of GVHD effector cells to the skin. Chemokine production by MCs is blocked by drugs used to treat cGVHD. The importance of MCs in skin cGVHD is mirrored by increased MCs in the skin of patients with dermal cGVHD. We show for the first time a role for MCs in skin cGVHD that may be targetable for preventive and therapeutic intervention in this disease.