Humoral responses in coronavirus disease 2019 (COVID-19) are often of limited durability, as seen with other human coronavirus epidemics. To address the underlying etiology, we examined post mortem thoracic lymph nodes and spleens in acute SARS-CoV-2 infection and observed the absence of germinal centers and a striking reduction in Bcl-6 + germinal center B cells but preservation of AID + B cells. Absence of germinal centers correlated with an early specific block in Bcl-6 + T FH cell differentiation together with an increase in T-bet + T H1 cells and aberrant extra-follicular TNF-α accumulation. Parallel peripheral blood studies revealed loss of transitional and follicular B cells in severe disease and accumulation of SARS-CoV-2-specific “disease-related” B cell populations. These data identify defective Bcl-6 + T FH cell generation and dysregulated humoral immune induction early in COVID-19 disease, providing a mechanistic explanation for the limited durability of antibody responses in coronavirus infections, and suggest that achieving herd immunity through natural infection may be difficult.

For many years the proponents of New Public Management (NPM) have promised to improve public services by making public sector organizations much more ‘business‐like’. There have been many investigations and empirical studies about the nature of NPM as well as its impact on organizations. However, most of these studies concentrate only on some elements of NPM and provide interesting, but often anecdotal, evidence and insights. Perhaps exactly because of the large amount of extremely revealing and telling empirical studies, there is, therefore, a lack of a systematic identification and understanding of the nature of NPM and its overall relevance. This paper contributes to a systematic identification and understanding of the concept of NPM as well as its multi‐dimensional impact on public sector organizations. First, the paper aims at (re‐) constructing a comprehensive taxonomy of NPM's main assumptions and core elements. Secondly, the paper tries to provide a more comprehensive and meta‐analytical analysis of primarily the negative consequences of NPM‐strategies for public sector organizations as well as the people working in them.

This paper addresses the paradox that despite all organizational change towards flatter and postmodern organizations, hierarchical order is quite persistent. We develop a differentiated understanding of hierarchy as either formal or informal and apply this analytical framework to several types of organization. The analysis reveals that hierarchy is much more widespread than thought; in particular, postmodern, representative democratic and network organizations are much less 'alternative' and 'hierarchy-free' than their labels and common understanding may suggest. The main argument is that the persistence of hierarchy in different types of organization can be explained by different dynamic relationships between formal and informal hierarchy.

Increased IFNα production contributes to the pathogenesis of infectious and autoimmune diseases. Plasmacytoid dendritic cells (pDCs) from females produce more IFNα upon TLR7 stimulation than pDCs from males, yet the mechanisms underlying this difference remain unclear. Here, we show that basal levels of interferon regulatory factor 5 (IRF5) in pDCs were significantly higher in females compared to males and positively correlated with the percentage of IFNα-secreting pDCs. Delivery of recombinant IRF5 protein into human primary pDCs increased TLR7-mediated IFNα secretion. In mice, genetic ablation of the estrogen receptor 1 (Esr1) gene in the hematopoietic compartment or DC lineage reduced IRF5 mRNA expression in pDCs and IFNα production. IRF5 mRNA levels furthermore correlated with Esr1 mRNA levels in human pDCs, consistent with IRF5 regulation at the transcriptional level by Esr1. Taken together, these data demonstrate a critical mechanism by which sex differences in basal pDC IRF5 expression lead to higher IFNα production upon TLR7 stimulation in females, and provide novel targets for the modulation of immune responses and inflammation.

The myosin family of motor proteins is implicated in mediating actin-based growth cone motility, but the roles of many myosins remain unclear. We previously implicated myosin 1c (M1c; formerly myosin Iβ) in the retention of lamellipodia (Wang et al., 1996). Here we address the role of myosin II (MII) in chick dorsal root ganglion neuronal growth cone motility and the contribution of M1c and MII to retrograde F-actin flow using chromophore-assisted laser inactivation (CALI). CALI of MII reduced neurite outgrowth and growth cone area by 25%, suggesting a role for MII in lamellipodial expansion. Micro-CALI of MII caused a rapid reduction in local lamellipodial protrusion in growth cones with no effects on filopodial dynamics. This is opposite to micro-CALI of M1c, which caused an increase in lamellipodial protrusion. We used fiduciary beads (Forscher et al., 1992) to observe retrograde F-actin flow during the acute loss of M1c or MII. Micro-CALI of M1c reduced retrograde bead flow by 76%, whereas micro-CALI of MII or the MIIB isoform did not. Thus, M1c and MIIB serve opposite and nonredundant roles in regulating lamellipodial dynamics, and M1c activity is specifically required for retrograde F-actin flow.

Chemokines and other chemoattractants direct leukocyte migration and are essential for the development and delivery of immune and inflammatory responses. To probe the molecular mechanisms that underlie chemoattractant-guided migration, we did an RNA-mediated interference screen that identified several members of the synaptotagmin family of calcium-sensing vesicle-fusion proteins as mediators of cell migration: SYT7 and SYTL5 were positive regulators of chemotaxis, whereas SYT2 was a negative regulator of chemotaxis. SYT7-deficient leukocytes showed less migration in vitro and in a gout model in vivo. Chemoattractant-induced calcium-dependent lysosomal fusion was impaired in SYT7-deficient neutrophils. In a chemokine gradient, SYT7-deficient lymphocytes accumulated lysosomes in their uropods and had impaired uropod release. Our data identify a molecular pathway required for chemotaxis that links chemoattractant-induced calcium flux to exocytosis and uropod release. COMPETING FINANCIAL INTERESTSThe authors declare no competing financial interests. NIH Public Access Author ManuscriptNat Immunol. Author manuscript; available in PMC 2011 June 1. Published in final edited form as:Nat Immunol. 2010 June ; 11(6): 495-502. doi:10.1038/ni.1878. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptChemoattractant-directed cell migration is critical for the generation and delivery of immune and inflammatory responses 1 . Defining the molecular mechanisms that control directed cell movement is therefore essential for understanding the function of cells of the immune response, the host response to infection and tumors, and immune-mediated auto-immune and inflammatory diseases. Chemokines and other classical chemoattractants, such as formyl-MetLeu-Phe (fMLP), C5a and leukotriene B 4 , induce directed cell migration through the activation of seven-transmembrane-spanning G protein-coupled receptors 2 . Chemoattractant receptors form a related subfamily of ~50 G protein-coupled receptors that all couple to the pertussis toxin-sensitive cAMP-inhibitory heterotrimeric guanine nucleotide-binding protein G i .Chemokine receptors and other chemoattractant receptors are found on all leukocyte lineages. Activation of chemoattractant receptors transforms a chemical signal in the form of a gradient into a biophysical program that results in leukocyte shape change and directed cell movement 3 . A leading edge called the lamellopodia and a trailing edge called the uropod characterize the polarized migrating leukocyte that develops after activation of chemoattractant receptors. These complex changes involve cycles of membrane protrusions and contractions, polymerization and depolymerization of F-actin, and adhesion and de-adhesion. These processes are coordinated through the activation of multiple signaling pathways that are only partially understood 4,5 .After chemokines and chemoattractants bind to the extracellular domains of their cognate G protein-coupled receptor, the Gα and Gβγ subunits of G i are liberate...

Neutrophils, the most abundant white blood cell, play a critical role in anti-pathogen immunity via phagocytic clearance, secretion of enzymes and immunomodulators, and the release of extracellular traps. Neutrophils non-specifically sense infection through an array of innate immune receptors and inflammatory sensors, but are also able to respond in a pathogen/antigen-specific manner when leveraged by antibodies via Fc-receptors. Among neutrophil functions, antibody-dependent neutrophil phagocytosis (ADNP) results in antibody-mediated opsonization, enabling neutrophils to sense and respond to infection in a pathogen-appropriate manner. Here, we describe a high-throughput flow cytometric approach to effectively visualize and quantify ADNP and its downstream consequences. The assay is easily adaptable, supporting both the use of purified neutrophils or white blood cells, the use of purified Ig or serum, and the broad utility of any target antigen. Thus, this ADNP assay represents a high-throughput platform for the in-depth characterization of neutrophil function.

PD-1 plays an important role in T cell exhaustion during HIV infection. PD-1 has two ligands: PD-L1, expressed on hematopoietic and nonhematopoietic cells, and PD-L2, limited to DCs and macrophages. Little is known about PD-L1 expression and regulation in human macrophages. Previous reports have found few immediate effects of macrophage exposure to HIV, suggesting that macrophages lack PRRs for this virus. Using quantitative confocal microscopy and a multiplexed cytokine bead array, we measured induction of PD-L1, PD-L2, and innate response cytokines in human MDMs in response to chemically inactivated HIV virions. Consistent with previous reports, no cytokines were induced by HIV virion exposure. Whereas PD-L1 and PD-L2 had low baseline expression, TLR ligands (LPS and CL097) up-regulated PD-L1 but not PD-L2. Unlike what we found for cytokine expression, PD-L1 and PD-L2 were up-regulated in response to exposure with inactivated HIV virions or with replication-competent HIV. Expression of PD-L1 was differentially modulated by IL-10, which induced up-regulation of PD-L1 but not of PD-L2, and IL-10 blockade enhanced only PD-L2 expression. We discuss implications for innate recognition of HIV by macrophages and potential, different roles for PD-L1 and PD-L2 in immunity and pathogenesis.