IL-4 induces CD22 expression to restrain the effector program of self-reactive virtual memory T cells

Abstract Parasitic helminths induce the production of interleukin (IL)-4 which causes the expansion of virtual memory CD8+ T cells (Tvm), a cell subset contributing to the control of viral coinfection. However, the mechanisms regulating IL-4-dependent Tvm activation and expansion during worm infection remain ill defined. We used single-cell RNA sequencing of CD8+ T cells to investigate IL-4-dependent Tvm responses upon helminth infection in mice. Gene signature analysis of CD8+ T cells identified a cell cluster marked by CD22, a canonical regulator of B cell activation, as a specific and selective surface marker of IL-4-induced Tvm cells. CD22+ Tvm were enriched for IFN-γ and granzyme A and retained a diverse TCR repertoire, while enriched in CDR3 sequences with features of self-reactivity. Deletion of CD22 expression in CD8+ T cells enhanced Tvm responses to helminth infection, indicating that this inhibitory receptor modulates Tvm responses. Thus, helminth-induced IL-4 drives the expansion and activation of self-reactive Tvm in the periphery that is counter-inhibited by CD22

The pre-vaccination regional epidemiological landscape of measles in Italy: contact patterns, effort needed for eradication, and comparison with other regions of Europe

BACKGROUND: Strong regional heterogeneity and generally sub-optimal rates of measles vaccination in Italy have, to date, hampered attainment of WHO targets for measles elimination, and have generated the need for the new Italian National Measles Elimination Plan. Crucial to success of the plan is the identification of intervention priorities based upon a clear picture of the regional epidemiology of measles derived from the use of data to estimate basic parameters. Previous estimates of measles force of infection for Italy have appeared anomalously low. It has been argued elsewhere that this results from Italian selective under-reporting by age of cases and that the true measles force of infection in Italy is probably similar to that of other European countries. A deeper examination of the evidence for this conjecture is undertaken in the present paper. METHODS: Using monthly regional case notifications data from 1949 to the start of vaccination in 1976 and notifications by age from 1971–76, summary equilibrium parameters (force of infection (FOI), basic reproductive ratio (R(0)) and critical vaccination coverage (p(c))) are calculated for each region and for each of 5 plausible contact patterns. An analysis of the spectra of incidence profiles is also carried out. Finally a transmission dynamics model is employed to explore the correspondence between projections using different estimates of force of infection and data on seroprevalence in Italy. RESULTS: FOI estimates are lower than comparable European FOIs and there is substantial regional heterogeneity in basic reproductive ratios; certain patterns of contact matrices are demonstrated to be unfeasible. Most regions show evidence of 3-year epidemic cycles or longer, and compared with England & Wales there appears to be little synchronisation between regions. Modelling results suggest that the lower FOI estimated from corrected aggregate national data matches serological data more closely than that estimated from typical European data. CONCLUSION: Results suggest forces of infection in Italy, though everywhere remaining below the typical European level, are historically higher in the South where currently vaccination coverage is lowest. There appears to be little evidence to support the suggestion that a higher true force of infection is masked by age bias in reporting

Guidelines for the use of flow cytometry and cell sorting in immunological studies (second edition)

These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells. The latest flow cytometry techniques and applications are also described, featuring examples of the data that can be generated and, importantly, how the data can be analysed. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid, all written and peer-reviewed by leading experts in the field, making this an essential research companion

Ethylene-mediated regulation of A2-type CYCLINs modulates hyponastic growth in arabidopsis

Upward leaf movement (hyponastic growth) is frequently observed in response to changing environmental conditions and can be induced by the phytohormone ethylene. Hyponasty results from differential growth (i.e. enhanced cell elongation at the proximal abaxial side of the petiole relative to the adaxial side). Here, we characterize Enhanced Hyponasty-d, an activation-tagged Arabidopsis (Arabidopsis thaliana) line with exaggerated hyponasty. This phenotype is associated with overexpression of the mitotic cyclin CYCLINA2;1 (CYCA2;1), which hints at a role for cell divisions in regulating hyponasty. Indeed, mathematical analysis suggested that the observed changes in abaxial cell elongation rates during ethylene treatment should result in a larger hyponastic amplitude than observed, unless a decrease in cell proliferation rate at the proximal abaxial side of the petiole relative to the adaxial side was implemented. Our model predicts that when this differential proliferation mechanism is disrupted by either ectopic overexpression or mutation of CYCA2;1, the hyponastic growth response becomes exaggerated. This is in accordance with experimental observations on CYCA2;1 overexpression lines and cyca2;1 knockouts. We therefore propose a bipartite mechanism controlling leaf movement: ethylene induces longitudinal cell expansion in the abaxial petiole epidermis to induce hyponasty and simultaneously affects its amplitude by controlling cell proliferation through CYCA2;1. Further corroborating the model, we found that ethylene treatment results in transcriptional down-regulation of A2-type CYCLINs and propose that this, and possibly other regulatory mechanisms affecting CYCA2;1, may contribute to this attenuation of hyponastic growth. Plants have acquired mechanisms to adjust growth and secure reproduction under unfavorable environmental conditions. Among the strategies to avoid adverse conditions is upward leaf movement, called hyponastic growth. This leaf reorientation is driven by unequal growth rates between adaxial and abaxial sides of the petiole (Cox et al., 2004; Polko et al., 2012b). Arabidopsis (Arabidopsis thaliana) exhibits hyponasty upon several environmental signals (e.g. submergence, waterlogging, proximity of neighboring vegetation, low red:far-red light ratios, reduced blue light fluence rates, low light intensities, and high temperatures; Millenaar et al., 2005, 2009; Mullen et al., 2006; Koini et al., 2009; Moreno et al., 2009; Van Zanten et al., 2009; Keuskamp et al., 2010; Keller et al., 2011; Vasseur et al., 2011; De Wit et al., 2012; Rauf et al., 2013; Dornbusch et al., 2014). Hyponasty alleviates the impact of environmental stresses (Van Zanten et al., 2010b). During submergence, it allows reestablishment of gas exchange with the atmosphere (e.g. Cox et al., 2003); at high plant densities, it positions the leaves in better lit layers of the canopy to improve light interception (e.g. De Wit et al., 2012); and at high temperatures, it improves the cooling capacity of the leaves (Crawford et al., 2012; Bridge et al., 2013). The cellular basis of hyponastic growth in Rumex palustris (Cox et al., 2004) and Arabidopsis (Polko et al., 2012b; Rauf et al., 2013) has been characterized. Ethylene causes reorientation of cortical microtubules (CMTs) in the petiole, which leads to longitudinal cell expansion in an approximately 2-mm-long epidermal cell zone at the proximal part of the abaxial side of the organ (Polko et al., 2012b). The interactions between several hormones (e.g. ethylene, abscisic acid, GAs, and auxin) in controlling hyponasty under various conditions have been studied (Mullen et al., 2006; Benschop et al., 2007; Millenaar et al., 2009; Van Zanten et al., 2009, 2010b; Peña-Castro et al., 2011). The volatile phytohormone ethylene is a key component in the complex regulatory network of hyponastic growth. Ethylene is the trigger and a positive regulator of hyponastic growth in submerged and waterlogged Arabidopsis (Millenaar et al., 2005, 2009; Van Zanten et al., 2010b; Rauf et al., 2013) and a negative regulator of high temperature-induced hyponasty (Van Zanten et al., 2009), but is not involved in low light-induced hyponastic growth in this species (Millenaar et al., 2009). Abscisic acid antagonizes ethylene-induced hyponasty (Benschop et al., 2007) and is a positive regulator of high temperature-induced hyponastic growth (Van Zanten et al., 2009). The growth-promoting GAs positively regulate hyponastic response to all three environmental signals (Peña-Castro et al., 2011), whereas auxins promote low light and high temperature-induced hyponastic growth (Millenaar et al., 2005; Koini et al., 2009; Van Zanten et al., 2009), as well as low red:far-red- and low blue light-induced hyponasty (Moreno et al., 2009; Keller et al., 2011). Finally, brassinosteroids also positively regulate ethylene-induced hyponasty (Polko et al., 2013). Despite the extensive knowledge on hormonal regulation of hyponasty, little is known about the molecular genetic mechanisms that drive this response. One notable exception is the study by Rauf et al. (2013), who showed that hyponastic growth in Arabidopsis in response to root waterlogging is controlled by the NAC (for No Apical Meristem [NAM], Arabidopsis Transcription Activation Factor) transcription factor SPEEDY HYPONASTIC GROWTH that directly affects expression of the ethylene biosynthesis gene 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID (ACC) OXIDASE5. Here, we followed a forward genetic approach to identify unique components that control hyponastic growth in Arabidopsis. From a population of activation-tagged plants (Weigel et al., 2000), we isolated Enhanced Hyponasty-D (EHY-D), which showed exaggerated hyponasty under exogenous ethylene application, low light intensities, and high temperature. We found that ectopic expression of the core cell cycle regulator CYCLINA2;1 (CYCA2;1) caused the exaggerated ethylene-induced leaf movement of EHY-D. Mathematical analyses indicated that, besides promoting cell expansion, ethylene can also attenuate the amplitude of hyponasty by affecting differential cell proliferation in the petiole of wild-type plants. We suggest that this occurs through ethylene-dependent effects on CYCA2;1 levels, activity, or sensitivity in petioles of wild-type plants. The ethylene-mediated transcriptional regulation of CYCA2;1 observed here could contribute to this. In EHY-D, however, ethylene-mediated effects on cell proliferation are overruled by ectopic CYCA2;1 overexpression, which consequently results in enhanced hyponasty, in accordance with the predictions of our model. Correspondingly, cyca2;1 knockout lines where ethylene cannot affect CYCA2;1-mediated cell proliferation also exhibited enhanced hyponasty. Our data therefore describe a mechanism by which hyponastic growth is kept within limits, through a bipartite role for ethylene: within the same organ, ethylene initiates hyponastic growth by promoting cell elongation, while simultaneously attenuating the response by regulation of A2-type CYCLIN-mediated cell proliferation

Integration of growth and patterning during vascular tissue formation in Arabidopsis

Coordination of cell division and pattern formation is central to tissue and organ development, particularly in plants where walls prevent cell migration. Auxin and cytokinin are both critical for division and patterning, but it is unknown how these hormones converge upon tissue development. We identify a genetic network that reinforces an early embryonic bias in auxin distribution to create a local, nonresponding cytokinin source within the root vascular tissue. Experimental and theoretical evidence shows that these cells act as a tissue organizer by positioning the domain of oriented cell divisions. We further demonstrate that the auxin-cytokinin interaction acts as a spatial incoherent feed-forward loop, which is essential to generate distinct hormonal response zones, thus establishing a stable pattern within a growing vascular tissue

Author Correction: A human immune dysregulation syndrome characterized by severe hyperinflammation with a homozygous nonsense Roquin-1 mutation (Nature Communications, (2019), 10, 1, (4779), 10.1038/s41467-019-12704-6)

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