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Thesis
Peer Reviewed

Lung Surveillance Revealed by Two-Photon Live Imaging

UC San Francisco Electronic Theses and Dissertations (2012)

The lung is a complex mucosal organ with the responsibility of oxygenating blood for the entire body. The large surface area of the lung allows for efficient exchange of oxygen in a large blood volume but also causes vast numbers of immune cells to constantly circulate through the organ. The high tidal volumes of air inhaled results in the introduction of particles, pathogens, and allergens into this delicate system. Because of the intimate relationship between the immune cells and the lung, a delicate balance must be maintained in order to sustain life. The goal of this thesis was to develop techniques to study interactions between the environment and the immune system with a particular focus is on the mechanisms and sites of uptake and presentation of antigens in the unchallenged lung and in a mouse model of asthma.

Real-time imaging of cellular and subcellular dynamics in vascularized organs requires image resolution and image registration to be simultaneously optimized without perturbing normal physiology. This problem is particularly pronounced in the lung. Here we report video-rate, two-photon imaging of a physiologically intact preparation of the mouse lung that is stabilizing and nondisruptive.

Asthma pathogenesis is focused around conducting airways. The reasons for this focus have been unclear since it was impossible to track the sites and timing of uptake or subsequent antigen presentation to T cell effectors. Two-photon microscopy of the lung parenchyma revealed early uptake of model antigens in alveoli giving rise to the asthma-specific CD11b+ DC and antigen retention in the airway region. A hyper-reactive lung thus results from selective retention of allergen-presenting cells in airway-adjacent interaction zones, not variation in the abilities of individual cells to survey the lung.

This study elucidates the pathway of antigen from inhalation to presentation to antigen-specific T cells. These techniques can be used to study other lung diseases and can be applied to other peripheral organs. Further study and development of ways to inhibit the different steps along this pathway may lead to therapies that could be used to treat many immune related diseases.

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Cover page: Lung Surveillance Revealed by Two-Photon Live Imaging

Article
Peer Reviewed

The spatiotemporal cellular dynamics of lung immunity

UC San Francisco Previously Published Works (2014)

The lung is a complex structure that is interdigitated with immune cells. Understanding the 4D process of normal and defective lung function and immunity has been a centuries-old problem. Challenges intrinsic to the lung have limited adequate microscopic evaluation of its cellular dynamics in real time, until recently. Because of emerging technologies, we now recognize alveolar-to-airway transport of inhaled antigen. We understand the nature of neutrophil entry during lung injury and are learning more about cellular interactions during inflammatory states. Insights are also accumulating in lung development and the metastatic niche of the lung. Here we assess the developing technology of lung imaging, its merits for studies of pathophysiology and areas where further advances are needed.

Cover page: The spatiotemporal cellular dynamics of lung immunity

Article
Peer Reviewed

Stabilized imaging of immune surveillance in the mouse lung

UC San Francisco Previously Published Works (2011)

Real-time imaging of cellular and subcellular dynamics in vascularized organs requires image resolution and image registration to be simultaneously optimized without perturbing normal physiology. This problem is particularly pronounced in the lung, in which cells may transit at speeds >1 mm s(-1) and in which normal respiration results in large-scale tissue movements that prevent image registration. Here we report video-rate, two-photon imaging of a physiologically intact preparation of the mouse lung that is stabilizing and nondisruptive. Using our method, we obtained evidence for differential trapping of T cells and neutrophils in mouse pulmonary capillaries, and observed neutrophil mobilization and dynamic vascular leak in response to stretch and inflammatory models of lung injury in mice. The system permits physiological measurement of motility rates of >1 mm s(-1), observation of detailed cellular morphology and could be applied in the future to other organs and tissues while maintaining intact physiology.

Cover page: Stabilized imaging of immune surveillance in the mouse lung

Article
Peer Reviewed

Type 2 innate lymphoid cells control eosinophil homeostasis

UC San Francisco Previously Published Works (2013)

Eosinophils are specialized myeloid cells associated with allergy and helminth infections. Blood eosinophils demonstrate circadian cycling, as described over 80 years ago, and are abundant in the healthy gastrointestinal tract. Although a cytokine, interleukin (IL)-5, and chemokines such as eotaxins mediate eosinophil development and survival, and tissue recruitment, respectively, the processes underlying the basal regulation of these signals remain unknown. Here we show that serum IL-5 levels are maintained by long-lived type 2 innate lymphoid cells (ILC2) resident in peripheral tissues. ILC2 cells secrete IL-5 constitutively and are induced to co-express IL-13 during type 2 inflammation, resulting in localized eotaxin production and eosinophil accumulation. In the small intestine where eosinophils and eotaxin are constitutive, ILC2 cells co-express IL-5 and IL-13; this co-expression is enhanced after caloric intake. The circadian synchronizer vasoactive intestinal peptide also stimulates ILC2 cells through the VPAC2 receptor to release IL-5, linking eosinophil levels with metabolic cycling. Tissue ILC2 cells regulate basal eosinophilopoiesis and tissue eosinophil accumulation through constitutive and stimulated cytokine expression, and this dissociated regulation can be tuned by nutrient intake and central circadian rhythms.

Cover page: Type 2 innate lymphoid cells control eosinophil homeostasis

Article
Peer Reviewed

The lung is a site of platelet biogenesis and a reservoir for haematopoietic progenitors

UC San Francisco Previously Published Works (2017)

Platelets are critical for haemostasis, thrombosis, and inflammatory responses, but the events that lead to mature platelet production remain incompletely understood. The bone marrow has been proposed to be a major site of platelet production, although there is indirect evidence that the lungs might also contribute to platelet biogenesis. Here, by directly imaging the lung microcirculation in mice, we show that a large number of megakaryocytes circulate through the lungs, where they dynamically release platelets. Megakaryocytes that release platelets in the lungs originate from extrapulmonary sites such as the bone marrow; we observed large megakaryocytes migrating out of the bone marrow space. The contribution of the lungs to platelet biogenesis is substantial, accounting for approximately 50% of total platelet production or 10 million platelets per hour. Furthermore, we identified populations of mature and immature megakaryocytes along with haematopoietic progenitors in the extravascular spaces of the lungs. Under conditions of thrombocytopenia and relative stem cell deficiency in the bone marrow, these progenitors can migrate out of the lungs, repopulate the bone marrow, completely reconstitute blood platelet counts, and contribute to multiple haematopoietic lineages. These results identify the lungs as a primary site of terminal platelet production and an organ with considerable haematopoietic potential.

Cover page: The lung is a site of platelet biogenesis and a reservoir for haematopoietic progenitors

Article
Peer Reviewed

Chitin Activates Parallel Immune Modules that Direct Distinct Inflammatory Responses via Innate Lymphoid Type 2 and γδ T Cells

UC San Francisco Previously Published Works (2014)

Chitin, a polysaccharide constituent of many allergens and parasites, initiates innate type 2 lung inflammation through incompletely defined pathways. We show that inhaled chitin induced expression of three epithelial cytokines, interleukin-25 (IL-25), IL-33, and thymic stromal lymphopoietin (TSLP), which nonredundantly activated resident innate lymphoid type 2 cells (ILC2s) to express IL-5 and IL-13 necessary for accumulation of eosinophils and alternatively activated macrophages (AAMs). In the absence of all three epithelial cytokines, ILC2s normally populated the lung but failed to increase IL-5 and IL-13. Although eosinophils and AAMs were attenuated, neutrophil influx remained normal without these epithelial cytokines. Genetic ablation of ILC2s, however, enhanced IL-1β, TNFα, and IL-23 expression, increased activation of IL-17A-producing γδ T cells, and prolonged neutrophil influx. Thus, chitin elicited patterns of innate cytokines that targeted distinct populations of resident lymphoid cells, revealing divergent but interacting pathways underlying the tissue accumulation of specific types of inflammatory myeloid cells.

Cover page: Chitin Activates Parallel Immune Modules that Direct Distinct Inflammatory Responses via Innate Lymphoid Type 2 and γδ T Cells

Article
Peer Reviewed

The Lancet's COVID-19 Commission Mental Health Task Force

UC Riverside Previously Published Works (2021)

Article
Peer Reviewed

Mental Health During the First Year of the COVID-19 Pandemic: A Review and Recommendations for Moving Forward

UC Riverside Previously Published Works (2022)

COVID-19 has infected millions of people and upended the lives of most humans on the planet. Researchers from across the psychological sciences have sought to document and investigate the impact of COVID-19 in myriad ways, causing an explosion of research that is broad in scope, varied in methods, and challenging to consolidate. Because policy and practice aimed at helping people live healthier and happier lives requires insight from robust patterns of evidence, this article provides a rapid and thorough summary of high-quality studies available through early 2021 examining the mental-health consequences of living through the COVID-19 pandemic. Our review of the evidence indicates that anxiety, depression, and distress increased in the early months of the pandemic. Meanwhile, suicide rates, life satisfaction, and loneliness remained largely stable throughout the first year of the pandemic. In response to these insights, we present seven recommendations (one urgent, two short-term, and four ongoing) to support mental health during the pandemic and beyond.

Article

Mental Health During the First Year of the COVID-19 Pandemic: A Review and Recommendations for Moving Forward

UC Riverside Previously Published Works (2021)

COVID-19 has infected millions of people and upended the lives of most humans on the planet. Researchers from across the psychological sciences have sought to document and investigate the impact of COVID-19 in myriad ways, causing an explosion of research that is broad in scope, varied in methods, and challenging to consolidate. Because policy and practice aimed at helping people live healthier and happier lives requires insight from robust patterns of evidence, this paper provides a rapid and thorough summary of high-quality studies available through early 2021 examining the mental health consequences of living through the COVID-19 pandemic. Our review of the evidence indicates that anxiety, depression, and distress increased in the early months of the pandemic. Meanwhile, suicide rates, life satisfaction, and loneliness remained largely stable throughout the first year of the pandemic. In response to these insights, we present seven recommendations (one urgent, two short-term, and four ongoing) to support mental health during the pandemic and beyond.