Interferon gamma constrains type 2 lymphocyte niche boundaries during mixed inflammation.

Allergic immunity is orchestrated by group 2 innate lymphoid cells (ILC2s) and type 2 helper T (Th2) cells prominently arrayed at epithelial- and microbial-rich barriers. However, ILC2s and Th2 cells are also present in fibroblast-rich niches within the adventitial layer of larger vessels and similar boundary structures in sterile deep tissues, and it remains unclear whether they undergo dynamic repositioning during immune perturbations. Here, we used thick-section quantitative imaging to show that allergic inflammation drives invasion of lung and liver non-adventitial parenchyma by ILC2s and Th2 cells. However, during concurrent type 1 and type 2 mixed inflammation, IFNγ from broadly distributed type 1 lymphocytes directly blocked both ILC2 parenchymal trafficking and subsequent cell survival. ILC2 and Th2 cell confinement to adventitia limited mortality by the type 1 pathogen Listeria monocytogenes. Our results suggest that the topography of tissue lymphocyte subsets is tightly regulated to promote appropriately timed and balanced immunity.

Understanding Why Frequent Users of EMS Call 9-1-1: A Grounded Theory Study.

INTRODUCTION: Frequent users of emergency medical services (EMS) have disproportionately high 9-1-1 call frequency. Evidence suggests that this small group burdens the health care system, leading to misallocation of already-limited health resources. AIM: To understand frequent users' perceptions and experiences regarding EMS, as well as the driving factors underlying their frequent use. METHOD: A grounded theory approach guided our qualitative research process. Participants older than 17 years who called EMS five or more times in the past year were consecutively sampled where each participant was contacted in the order they appeared on our list of potential participants for interviews until data saturation was achieved. Transcripts were analyzed to derive common themes among frequent EMS callers. RESULTS: Frequent EMS calls often resulted from chronic medical conditions creating recurrent crisis situations, mental health issues as well as mobility issues, frequent noninjurious falls, and social isolation. Combined with these factors, perceptions of the purpose of EMS and social circumstances also contributed to the creation of complex health issues that influenced frequent EMS use. These findings can advise the development of future paramedicine programs and health promotion interventions.

BCR ligation selectively inhibits IgE class switch recombination.

Mechanisms that restrict class switch recombination (CSR) to IgE limit the subsequent production of IgE antibodies and therefore the development of allergic disease. Mice with impaired B cell receptor (BCR) signaling have significantly increased IgE responses, consistent with a role for BCR signaling in IgE regulation. While prior work focused on BCR signaling in IgE-expressing cells to explain these findings, it has been reported that BCR signaling can reduce CSR. Therefore, we investigated the possibility that IgE CSR might be particularly sensitive to inhibition by BCR signaling in unswitched B cells. We found that immunization of mice with high-affinity antigen resulted in reduced representation of IgE-expressing cells among germinal center B cells and plasma cells relative to a low-affinity antigen. Mechanistic experiments with cultured mouse B cells demonstrated that BCR ligands selectively inhibited IgE CSR in a dose-, affinity-, and avidity-dependent manner. Signaling via Syk was required for the inhibition of IgE CSR following BCR stimulation, whereas inhibition of the PI3K subunit p110δ increased IgE CSR independently of BCR ligation. The inhibition of IgE CSR by BCR ligands synergized with IL-21 or TGFß1. BCR ligation also inhibited CSR to IgE in human tonsillar B cells, and this inhibition was also synergistic with IL-21. These findings establish that IgE CSR is uniquely susceptible to inhibition by BCR signaling in mouse and human B cells, with important implications for the regulation and pathogenesis of allergic disease.

B cell receptor ligation induces IgE plasma cell elimination.

The proper regulation of IgE production safeguards against allergic disease, highlighting the importance of mechanisms that restrict IgE plasma cell (PC) survival. IgE PCs have unusually high surface B cell receptor (BCR) expression, yet the functional consequences of ligating this receptor are unknown. Here, we found that BCR ligation induced BCR signaling in IgE PCs followed by their elimination. In cell culture, exposure of IgE PCs to cognate antigen or anti-BCR antibodies induced apoptosis. IgE PC depletion correlated with the affinity, avidity, amount, and duration of antigen exposure and required the BCR signalosome components Syk, BLNK, and PLCγ2. In mice with a PC-specific impairment of BCR signaling, the abundance of IgE PCs was selectively increased. Conversely, BCR ligation by injection of cognate antigen or anti-IgE depleted IgE PCs. These findings establish a mechanism for the elimination of IgE PCs through BCR ligation. This has important implications for allergen tolerance and immunotherapy as well as anti-IgE monoclonal antibody treatments.

Intrinsic and extrinsic regulation of IgE B cell responses.

Stringent regulation of IgE antibody production is critical for constraining allergic responses. This review discusses recent advances in understanding cell-intrinsic and extrinsic mechanisms that regulate the genesis and fate of IgE B cells. B cell-intrinsic regulation of IgE is orchestrated by the IgE B Cell Receptor (BCR). Through its antigen-independent signaling and low surface expression, the IgE BCR drives IgE B cells to differentiate into short-lived plasma cells and/or undergo apoptosis, restricting IgE-expressing cells from entering long-lived compartments. The pivotal extrinsic regulators of IgE responses are T follicular helper cells (TFH). TFH produce IL-4 and IL-21, which, respectively, are the major activating and inhibitory cytokines for IgE class-switching. Other newly identified T follicular subsets also contribute to IgE regulation. Although IgE responses are normally constrained, recent studies suggest that specific conditions can induce the formation of IgE responses with enhanced affinity or longevity, effectively 'breaking the rules' of IgE regulation.

MicroRNA-directed pathway discovery elucidates an miR-221/222-mediated regulatory circuit in class switch recombination.

MicroRNAs (miRNAs, miRs) regulate cell fate decisions by post-transcriptionally tuning networks of mRNA targets. We used miRNA-directed pathway discovery to reveal a regulatory circuit that influences Ig class switch recombination (CSR). We developed a system to deplete mature, activated B cells of miRNAs, and performed a rescue screen that identified the miR-221/222 family as a positive regulator of CSR. Endogenous miR-221/222 regulated B cell CSR to IgE and IgG1 in vitro, and miR-221/222-deficient mice exhibited defective IgE production in allergic airway challenge and polyclonal B cell activation models in vivo. We combined comparative Ago2-HITS-CLIP and gene expression analyses to identify mRNAs bound and regulated by miR-221/222 in primary B cells. Interrogation of these putative direct targets uncovered functionally relevant downstream genes. Genetic depletion or pharmacological inhibition of Foxp1 and Arid1a confirmed their roles as key modulators of CSR to IgE and IgG1.

The p300 and CBP Transcriptional Coactivators Are Required for ß-Cell and α-Cell Proliferation.

p300 (EP300) and CBP (CREBBP) are transcriptional coactivators with histone acetyltransferase activity. Various ß-cell transcription factors can recruit p300/CBP, and thus the coactivators could be important for ß-cell function and health in vivo. We hypothesized that p300/CBP contribute to the development and proper function of pancreatic islets. To test this, we bred and studied mice lacking p300/CBP in their islets. Mice lacking either p300 or CBP in islets developed glucose intolerance attributable to impaired insulin secretion, together with reduced α- and ß-cell area and islet insulin content. These phenotypes were exacerbated in mice with only a single copy of p300 or CBP expressed in islets. Removing p300 in pancreatic endocrine progenitors impaired proliferation of neonatal α- and ß-cells. Mice lacking all four copies of p300/CBP in pancreatic endocrine progenitors failed to establish α- and ß-cell mass postnatally. Transcriptomic analyses revealed significant overlaps between p300/CBP-downregulated genes and genes downregulated in Hnf1α-null islets and Nkx2.2-null islets, among others. Furthermore, p300/CBP are important for the acetylation of H3K27 at loci downregulated in Hnf1α-null islets. We conclude that p300 and CBP are limiting cofactors for islet development, and hence for postnatal glucose homeostasis, with some functional redundancy.