Intermediate Population Research Articles

Stellar populations of a sample of far-infrared AGN and non-AGN green valley galaxies

ABSTRACT We present a study on the stellar populations and stellar ages of a subsample of far-infrared (FIR) active galactic nucleus (AGN) and non-AGN green valley galaxies at ${0.6\, \lt \, z\, \lt \, 1.0}$ using the data from the Cosmological Evolution Survey field. We used long-slit spectroscopy and derived stellar populations and stellar ages using the stellar population synthesis code ‘starlight’ and analysed the available Lick/IDS indices, such as Dn4000 and HδA. We find that both FIR AGN and non-AGN green valley galaxies are dominated by intermediate stellar populations (67 per cent and 53 per cent, respectively). The median stellar ages for AGNs and non-AGNs are ${\log t\, =\, 8.5}$ and ${\, 8.4\, \rm yr}$, respectively. We found that majority of our sources (62 per cent of AGNs and 66 per cent of non-AGNs) could have experienced bursts and continuous star formation (SF). In addition, most of our FIR AGNs (38 per cent) compared to FIR non-AGNs (27 per cent) might have experienced a burst of SF more than 0.1 Gyr ago. We also found that our FIR AGN and non-AGN green valley galaxies have similar quenching time-scales of ∼ 70 Myr. Therefore, the results obtained here are in line with our previous results where we do not find that our sample of FIR AGNs in the green valley shows signs of negative AGN feedback, as has been suggested previously in optical studies.

Effects of an intermediate mass sterile neutrino population on the early Universe

The hot and dense early Universe combined with the promise of high-precision cosmological observations provide an intriguing laboratory for Beyond Standard Model (BSM) physics. We simulate the early Universe to examine the effects of the decay of thermally populated sterile neutrino states into Standard Model products around the time of weak decoupling. These decays deposit a significant amount of entropy into the plasma as well as produce a population of high-energy out-of-equilibrium active neutrinos. As a result, we can constrain these models by their inferred value of $N_{\rm eff}$, the effective number of relativistic degrees of freedom. In this work, we explore a variety of models with $N_{\rm eff}{}$ values consistent with CMB observations, but with vastly different active neutrino spectra which will challenge the standard cosmological model, affect lepton capture rates on free nucleons, and may significantly affect Big Bang Nucleosynthesis (BBN).

A test of frequency-dependent selection in the evolution of a generalist phenotype.

A solitary population of consumers frequently evolves to the middle of a resource gradient and an intermediate mean phenotype compared to a sympatric pair of competing species that diverge to either side via character displacement. The forces governing the distribution of phenotypes in these allopatric populations, however, are little investigated. Theory predicts that the intermediate mean phenotype of the generalist should be maintained by negative frequency‐dependent selection, whereby alternate extreme phenotypes are favored because they experience reduced competition for resources when rare. However, the theory makes assumptions that are not always met, and alternative explanations for an intermediate phenotype are possible. We provide a test of this prediction in a mesocosm experiment using threespine stickleback that are ecologically and phenotypically intermediate between the more specialized stickleback species that occur in pairs. We manipulated the frequency distribution of phenotypes in two treatments and then measured effects on a focal intermediate population. We found a slight frequency‐dependent effect on survival in the predicted direction but not on individual growth rates. This result suggests that frequency‐dependent selection might be a relatively weak force across the range of phenotypes within an intermediate population and we suggest several general reasons why this might be so. We propose that allopatric populations might often be maintained at an intermediate phenotype instead by stabilizing or fluctuating directional selection.

The X-shooter Spectral Library (XSL): Data Release 3

We present the third data release (DR3) of the X-shooter Spectral Library (XSL). This moderate-to-high resolution, near-ultraviolet-to-near-infrared (350–2480 nm, R ∼ 10 000) spectral library is composed of 830 stellar spectra of 683 stars. DR3 improves upon the previous data release by providing the combined de-reddened spectra of the three X-shooter segments over the full 350–2480 nm wavelength range. It also includes additional 20 M-dwarf spectra from the ESO archive. We provide detailed comparisons between this library and Gaia EDR3, MILES, NGSL, CaT library, and (E-)IRTF. The normalised rms deviation is better than D = 0.05 or 5% for the majority of spectra in common between MILES (144 spectra of 180), NGSL (112/116), and (E-)IRTF (55/77) libraries. Comparing synthetic colours of those spectra reveals only negligible offsets and small rms scatter, such as the median offset(rms) 0.001 ± 0.040 mag in the (box1 − box2) colour of the UVB arm, −0.004 ± 0.028 mag in (box3 − box4) of the VIS arm, and −0.001 ± 0.045 mag in (box2 − box3) colour between the UVB and VIS arms, when comparing stars in common with MILES. We also find an excellent agreement between the Gaia published (BP − RP) colours and those measured from the XSL DR3 spectra, with a zero median offset and an rms scatter of 0.037 mag for 449 non-variable stars. The unmatched characteristics of this library, which combine a relatively high resolution, a large number of stars, and an extended wavelength coverage, will help us to bridge the gap between the optical and the near-IR studies of intermediate and old stellar populations, and to probe low-mass stellar systems.

A multipopulation cooperative coevolutionary whale optimization algorithm with a two-stage orthogonal learning mechanism

This paper designed a multipopulation cooperative coevolutionary framework with a two-stage orthogonal learning (OL) mechanism for the whale optimization algorithm (MCCWOA) to improve the performance of the whale optimization algorithm (WOA). In the framework, a prediction model of the neighborhood structure is established by discovering the guidance information of the following iteration process in the objective space at the first-stage OL. In the second-stage OL, an auxiliary vector pool with various features in the decision space is introduced to guide the candidates falling in the stagnant status to conduct more valuable exploration. According to the domain knowledge of the candidates, the population is divided into the elite population, the intermediate population, and the inferior population. The information of the subpopulations has interacted with the corresponding historical populations in the evolution processes to enhance the ability of cooperative coevolution among individuals. A standard set of comprehensive benchmark cases and three engineering cases are utilized to verify the advantages of the proposed algorithm. The results of the statistical analysis, diversity analysis, and convergence analysis testified that the MCCWOA outperforms the 15 state-of-the-art algorithms regarding efficiency and significance.

Programmatic screening for latent tuberculosis in migrants

WHO has set targets to eliminate tuberculosis as a public health problem globally by 2035. In settings with low tuberculosis incidence, cases have become concentrated among populations born in intermediate and high-incidence countries and susceptible populations.1 To achieve WHO targets in low-incidence countries, identification and treatment of latent tuberculosis infection (LTBI) among foreign-born individuals will be needed to reduce persistently elevated tuberculosis rates.2,3 In 2016, as part of a new national Collaborative tuberculosis strategy, England implemented the first nationwide migrant LTBI screening programme.

Active surveillance in favorable intermediate risk prostate cancer: outstanding questions and controversies.

Active surveillance has become the preferred management strategy for patients with low risk prostate cancer, but it is unclear if active surveillance can be safely extended to favorable intermediate risk (FIR) prostate cancer patients. Furthermore, defining a favorable intermediate risk prostate cancer population safe for active surveillance remains elusive due to paucity of high-level data in this population. This article serves to review relevant data, particularly the safety of active surveillance in grade group 2 patients, and what tools are available to aid in selecting a favorable subset of intermediate risk patients. Active surveillance studies with long-term data appear to report worsened survival outcomes in intermediate risk patients when compared to those undergoing definitive treatment, but there exists a subset of intermediate risk patients with nearly equivalent outcomes to low risk patients on active surveillance. Tools such as percentage and total length of Gleason pattern 4, tumor volume, prostate specific antigen density, magnetic resonance imaging, and genomic modifiers may help to select a favorable subset of intermediate risk prostate cancer appropriate for active surveillance. Active surveillance is a viable strategy in select patients with low volume group grade 2 (GG2) prostate cancer. Prospective and retrospective data in the FIR population appear to be mostly favorable in regards to survival outcomes, but there exists some heterogeneity with respect to long-term outcomes in this patient population.

DNA Methylation Can Mediate Local Adaptation and Response to Climate Change in the Clonal Plant Fragaria vesca: Evidence From a European-Scale Reciprocal Transplant Experiment.

The ongoing climate crisis represents a growing threat for plants and other organisms. However, how and if plants will be able to adapt to future environmental conditions is still debated. One of the most powerful mechanisms allowing plants to tackle the changing climate is phenotypic plasticity, which can be regulated by epigenetic mechanisms. Environmentally induced epigenetic variation mediating phenotypic plasticity might be heritable across (a)sexual generations, thus potentially enabling rapid adaptation to climate change. Here, we assessed whether epigenetic mechanisms, DNA methylation in particular, enable for local adaptation and response to increased and/or decreased temperature of natural populations of a clonal plant, Fragaria vesca (wild strawberry). We collected ramets from three populations along a temperature gradient in each of three countries covering the southern (Italy), central (Czechia), and northern (Norway) edges of the native European range of F. vesca. After clonal propagation and alteration of DNA methylation status of half of the plants via 5-azacytidine, we reciprocally transplanted clones to their home locality and to the other two climatically distinct localities within the country of their origin. At the end of the growing season, we recorded survival and aboveground biomass as fitness estimates. We found evidence for local adaptation in intermediate and cold populations in Italy and maladaptation of plants of the warmest populations in all countries. Plants treated with 5-azacytidine showed either better or worse performance in their local conditions than untreated plants. Application of 5-azacytidine also affected plant response to changed climatic conditions when transplanted to the colder or warmer locality than was their origin, and the response was, however, country-specific. We conclude that the increasing temperature will probably be the limiting factor determining F. vesca survival and distribution. DNA methylation may contribute to local adaptation and response to climatic change in natural ecosystems; however, its role may depend on the specific environmental conditions. Since adaptation mediated by epigenetic variation may occur faster than via natural selection on genetic variants, epigenetic adaptation might to some degree help plants in keeping up with the ongoing environmental crisis.

Monocyte Gene and Molecular Expression Profiles Suggest Distinct Effector and Regulatory Functions in Beninese HIV Highly Exposed Seronegative Female Commercial Sex Workers.

We have previously reported that the female genital tract (FGT) of Beninese HIV highly-exposed seronegative (HESN) commercial sex workers (CSWs), presented elevated frequencies of a myeloid HLA-DR+CD14+CD11c+ population presenting “tolerogenic” monocyte derived dendritic cells (MoDC) features. In order to assess whether a differential profile of monocytes may be involved in the generation of these genital MoDCs, we have herein characterized the blood monocyte compartment of Beninese HESNs (HIV-uninfected ≥ 10 years CSWs) and relevant controls (HIV-uninfected 2.5–5 years CSWs herein termed “early HESNs”), HIV-infected CSWs, and low-risk HIV-uninfected women from the general population. Transcriptomic analyses by RNA-Seq of total sorted blood monocytes demonstrate that in comparison to the control groups, HESNs present increased expression levels of FCGR2C, FCAR, ITGAX, ITGAM, CR2, CD68, and CD163 genes, associated with effector functions. Moreover, we found increased expression levels of genes associated with protection/control against SHIV/HIV such as CCL3, CCL4, CCL5, BHLHE40, and TNFSF13, as well as with immune regulation such as IL-10, Ahr, CD83, and the orphan nuclear receptor (NR)4A1, NR4A2, and NR4A3. Through multicolor flow cytometry analyses, we noticed that the frequencies of intermediate and non-classical monocyte populations tended to be elevated in the blood of HESNs, and exhibited increased expression levels of effector CD16, CD11c, CD11b, as well as regulatory HLA-G, IL-10, and IFN-α markers when compared to HIV-uninfected women and/or HIV-infected CSWs. This profile is compatible with that previously reported in the FGT of HESNs, and likely confers an enormous advantage in their resistance to HIV infection.

Context dependent variation in corticosterone and phenotypic divergence of Rana arvalis populations along an acidification gradient

BackgroundPhysiological processes, as immediate responses to the environment, are important mechanisms of phenotypic plasticity and can influence evolution at ecological time scales. In stressful environments, physiological stress responses of individuals are initiated and integrated via the release of hormones, such as corticosterone (CORT). In vertebrates, CORT influences energy metabolism and resource allocation to multiple fitness traits (e.g. growth and morphology) and can be an important mediator of rapid adaptation to environmental stress, such as acidification. The moor frog, Rana arvalis, shows adaptive divergence in larval life-histories and predator defense traits along an acidification gradient in Sweden. Here we take a first step to understanding the role of CORT in this adaptive divergence. We conducted a fully factorial laboratory experiment and reared tadpoles from three populations (one acidic, one neutral and one intermediate pH origin) in two pH treatments (Acid versus Neutral pH) from hatching to metamorphosis. We tested how the populations differ in tadpole CORT profiles and how CORT is associated with tadpole life-history and morphological traits.ResultsWe found clear differences among the populations in CORT profiles across different developmental stages, but only weak effects of pH treatment on CORT. Tadpoles from the acid origin population had, on average, lower CORT levels than tadpoles from the neutral origin population, and the intermediate pH origin population had intermediate CORT levels. Overall, tadpoles with higher CORT levels developed faster and had shorter and shallower tails, as well as shallower tail muscles.ConclusionsOur common garden results indicate among population divergence in CORT levels, likely reflecting acidification mediated divergent selection on tadpole physiology, concomitant to selection on larval life-histories and morphology. However, CORT levels were highly environmental context dependent. Jointly these results indicate a potential role for CORT as a mediator of multi-trait divergence along environmental stress gradients in natural populations. At the same time, the population level differences and high context dependency in CORT levels suggest that snapshot assessment of CORT in nature may not be reliable bioindicators of stress.

A Systematic Analysis of Stellar Populations in the Host Galaxies of Changing-look AGNs

Abstract “Changing-look” active galactic nuclei (CL-AGNs) are a newly discovered class of AGNs that show the appearance (or disappearance) of broad emission lines within short timescales (months to years), and are often associated with dramatic changes in their continuum emissions. They provide us with an unprecedented chance to directly investigate the host galaxy properties with minimal contamination from the luminous central engine during the turn-off state, which is difficult for normal luminous AGNs. In this work, for the first time, we systematically characterize the stellar populations and star formation histories of host galaxies for 26 turn-off CL-AGNs using the stellar population synthesis code STARLIGHT. We find that the stellar populations of CL-AGNs are similar to those of normal AGNs, except that the intermediate stellar populations contribute more fractions. We estimate their stellar velocity dispersions (σ ⋆) and black hole masses (M BH,vir), and find that CL-AGNs also follow the overall M BH–σ ⋆ relationship. We also confirm the previous claims that CL-AGNs tend to be biased toward lower Eddington ratios, and that their extreme variabilities are more likely due to the intrinsic changes of the accretion rates. In addition, CL-AGNs with recent star formations tend to have higher Eddington ratios. Compared with previous studies, our analysis suggests that there may be a correlation between CL-AGN host galaxy properties and their CL phenomena.

Evolution of right ventricular dysfunction and tricuspid regurgitation after TAVI: A prospective study

BackgroundRight ventricular (RV) dysfunction and tricuspid regurgitation (TR) may impact prognosis of patients undergoing Transcatheter Aortic Valve Implantation (TAVI). We aimed to evaluate the evolution of previous RV dysfunction and/or significant TR after TAVI procedure. MethodsAll patients undergoing TAVI between January 2018 and January 2019 were enrolled in this prospective cohort. Patients with at least one right heart (RH) abnormality at baseline including RV dysfunction (TAPSE < 17 mm, S-wave < 9.5 cm/s, Fractional area change < 35%, Strain > −20%, Tei > 0.54) and/or significant TR (Effective Regurgitant Orifice Area ≥ 40 mm2 and/or Regurgitant Volume ≥ 45 mL) underwent transthoracic echocardiography at day 1 and 6-month after TAVI. The primary endpoint was the regression of pre-TAVI RV dysfunction and/or significant TR at 6-month follow-up. ResultsThe study enrolled 144 patients including 76 women (52.8%) with a mean age of 81.1 ± 6.8 yo, a mean EuroSCORE 2 of 5.2 ± 3.9%. At least one RH abnormality was observed in 53 patients (36.8%). At 6-month, at least one RV dysfunction parameter significantly improved in 26 patients (63.4%), TAPSE increasing from 13.0 ± 2.6 to 16.0 ± 9.8 mm, p < 0.0001 and S-wave from 7.7 ± 1.2 to 10.0 ± 2.6 cm/s, p = 0.004. Among 31 patients with baseline significant TR, TR decreased in 14 (45.2%); p = 0.003. Among patients with baseline RH abnormalities, 13 (24.5%) fully recovered. Baseline significant TR was predictive of 6-month clinical outcomes (OR = 3.1, 95%CI = [1.01–9.0], p = 0.03). ConclusionIn our recent intermediate surgical risk TAVI population, RV dysfunction and/or significant TR are frequent at baseline and fully or partially recover in most patients at 6-month follow-up.

CellRank for directed single-cell fate mapping

Computational trajectory inference enables the reconstruction of cell state dynamics from single-cell RNA sequencing experiments. However, trajectory inference requires that the direction of a biological process is known, largely limiting its application to differentiating systems in normal development. Here, we present CellRank (https://cellrank.org) for single-cell fate mapping in diverse scenarios, including regeneration, reprogramming and disease, for which direction is unknown. Our approach combines the robustness of trajectory inference with directional information from RNA velocity, taking into account the gradual and stochastic nature of cellular fate decisions, as well as uncertainty in velocity vectors. On pancreas development data, CellRank automatically detects initial, intermediate and terminal populations, predicts fate potentials and visualizes continuous gene expression trends along individual lineages. Applied to lineage-traced cellular reprogramming data, predicted fate probabilities correctly recover reprogramming outcomes. CellRank also predicts a new dedifferentiation trajectory during postinjury lung regeneration, including previously unknown intermediate cell states, which we confirm experimentally.

Differential LysoTracker Uptake Defines Two Populations of Distal Epithelial Cells in Idiopathic Pulmonary Fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal degenerative lung disease of unknown etiology. Although in its final stages it implicates, in a reactive manner, all lung cell types, the initial damage involves the alveolar epithelial compartment, in particular the alveolar epithelial type 2 cells (AEC2s). AEC2s serve dual progenitor and surfactant secreting functions, both of which are deeply impacted in IPF. Thus, we hypothesize that the size of the surfactant processing compartment, as measured by LysoTracker incorporation, allows the identification of different epithelial states in the IPF lung. Flow cytometry analysis of epithelial LysoTracker incorporation delineates two populations (Lysohigh and Lysolow) of AEC2s that behave in a compensatory manner during bleomycin injury and in the donor/IPF lung. Employing flow cytometry and transcriptomic analysis of cells isolated from donor and IPF lungs, we demonstrate that the Lysohigh population expresses all classical AEC2 markers and is drastically diminished in IPF. The Lysolow population, which is increased in proportion in IPF, co-expressed AEC2 and basal cell markers, resembling the phenotype of the previously identified intermediate AEC2 population in the IPF lung. In that regard, we provide an in-depth flow-cytometry characterization of LysoTracker uptake, HTII-280, proSP-C, mature SP-B, NGFR, KRT5, and CD24 expression in human lung epithelial cells. Combining functional analysis with extracellular and intracellular marker expression and transcriptomic analysis, we advance the current understanding of epithelial cell behavior and fate in lung fibrosis.

An investigation of demographic and component Allee effects in the Madagascar hissing cockroach

AbstractPopulation density affects the behaviour and population dynamics of insects, but the nature of that effect may depend on the degree of sociality. We experimentally manipulated initial population density of a subsocial insect, the Madagascar hissing cockroach,Gromphadorhina portentosaSchaum, 1853 (Blattodea: Blaberidae), to determine its effect on vital rates and population dynamics. In accordance with the predicted Allee effect, we hypothesised that intermediate cockroach population density will increase per capita birth rates and cause a higher population growth rate relative to smaller and larger population densities. After tracking 12 experimental populations (three replicates of four initial population densities) for 15 months, we found evidence of Allee effects in this insect. Per capita birth rates showed a quadratic response, with rates highest at intermediate population densities, suggesting a component Allee effect. Contrary to expectations for a demographic Allee effect, population growth rates showed negative density dependence. The proportion of adult females in the population increased with population density, but the mechanism for this increase is not known. Our findings provide evidence for at least one form of Allee effect inG. portentosaand shows a possible connection between subsocial behaviour and population-level responses.

Exploring the association of fibrinogen and CRP with the clinical spectrum of CAD and periprocedural outcomes in patients undergoing percutaneous coronary interventions.

Background:The pathophysiology of an atherosclerotic plaque is mediated by the mechanisms involving thrombus formation and systemic inflammation. While C-reactive protein (CRP) levels are useful in predicting a cardiovascular event in intermediate risk population, the usefulness of routinely measuring fibrinogen in patients with acute coronary syndrome (ACS) is debatable. Also, data on the association of these markers with periprocedural outcomes in patients undergoing percutaneous coronary interventions (PCI) is scarce.Aims:The study aimed to determine whether the levels of fibrinogen and CRP vary across the different spectra of CAD and whether they have any correlation with cardiac Troponin I levels.Materials and Methods:A total of 284 patients with coronary artery disease undergoing percutaneous coronary intervention were included in the study. Complete blood count, serum lipid profile, serum CRP, fibrinogen, and troponin I were measured for all patients.Results:Patients with STEMI had significantly higher levels of CRP as compared to those with unstable angina (USA) and chronic stable angina (CSA). Patients presenting with ACS had significantly higher baseline fibrinogen as compared to those with CSA. A significant positive correlation between CRP and admission Troponin I (r = 0.50; P < 0.05) as well as fibrinogen and admission troponin I (r = 0.30; P < 0.05) was observed. The CRP levels were significantly higher in 15 patients with periprocedural MI as compared to those who did not develop periprocedural MI.Conclusions:The levels of the markers of inflammation and atherothrombosis vary with presentation across varied spectra of CAD with generally higher levels in acute presentation and in those who develop periprocedural MI.

Uncommon Pathological Presentations of Mature Cystic Teratoma: A Case Series

Mature cystic teratomas are benign tumours of the ovary but rarely certain unusual gross and microscopic findings might complicate their diagnosis or may have an impact on their clinical outcome. Here, we are presenting a case series of five unusual pathological presentations of mature cystic teratomas of ovary. Out of five cases, three cases were of collision tumours, in which combination of mature cystic teratoma is seen with mucinous cystadenoma in two cases, and with serous cystadenoma in one case. True collision tumours are defined as histologically distinct neoplasms in the same tissue or organ without any histologic admixture or intermediate cell population zone between two components. These tumours are located in various organs but ovarian location is rare. Mature cystic teratoma is the most common component of collision combinations in the ovary. All classes of ovarian tumours, benign, borderline and malignant may collide and therefore, clinical outcomesin collision tumours depend on individual tumour characteristics. Fourth case was of a mature cystic teratoma associated with a distinct hemangiomatous component. Mature cystic teratoma associated with prominent hemangiomatous component is a very rare finding with only few case reports in the literature and it should be differentiated from true ovarian hemangioma, lymphangioma and angiosarcoma. Fifth case was of bilateral mature cystic teratomas associated with a well-defined lipomatous lesion in right sided mature cystic teratoma mimicking lipoma. Lipomatous ovarian lesions are very rare and mature cystic teratoma with prominent adipocytic proliferation is also an exceedingly uncommon finding and it should be differentiated from true ovarian lipoma and other atypical lipomatous proliferations. Most of these tumours remain clinically and radiologically unrecognized, therefore their histological recognition is essential for adequate patient management.

Vernalization requirements of Kernza intermediate wheatgrass

AbstractIntermediate wheatgrass [Thinopyrum intermedium (Host) Barkworth and D.R. Dewey], bred for high grain yield, has become the first perennial grain in North America and is commercialized under the tradename Kernza. The expansion of this crop from the U.S. Midwest to areas with milder winters would require an understanding of its vernalization requirements for flowering and the availability of genetic diversity for this trait. The goal of this research was to determine the length of the cold period required for vernalization in Kernza intermediate wheatgrass. Two treatment factors (population and length of cold incubation period) were evaluated. Seeds from eight breeding populations from Kansas and Minnesota were evaluated in growth chambers at 5 °C and 10 h light for cold periods from 3 to 9 wk. The percentage of plants that flowered increased from 30 to 96% as the length of the cold incubation period increased from 3 to 7 wk following a sigmoid model. For most yield components, no changes were observed after 7 wk of cold incubation. There were no differences among populations for most traits and there was large within‐population phenotypic diversity. These results confirm that Kernza intermediate wheatgrass populations have moderate vernalization requirements. Further research is needed to confirm the feasibility of breeding Kernza with lower vernalization requirements.

CXCR3 regulates stem and proliferative CD8+ T cells during chronic infection by promoting interactions with DCs in splenic bridging channels.

SUMMARYProduction of effector CD8+ T cells during persistent infection requires a stable pool of stem-like cells that can give rise to effector cells via a proliferative intermediate population. In infection models marked by T cell exhaustion, this process can be transiently induced by checkpoint blockade but occurs spontaneously in mice chronically infected with the protozoan intracellular parasite Toxoplasma gondii. We observe distinct locations for parasite-specific T cell subsets, implying a link between differentiation and anatomical niches in the spleen. Loss of the chemokine receptor CXCR3 on T cells does not prevent white pulp-to-red pulp migration but reduces interactions with CXCR3 ligand-producing dendritic cells (DCs) and impairs memory-to-intermediate transition, leading to a buildup of memory T cells in the red pulp. Thus, CXCR3 increases T cell exposure to differentiation-inducing signals during red pulp migration, providing a dynamic mechanism for modulating effector differentiation in response to environmental signals.

Intermediate progenitor cells provide a transition between hematopoietic progenitors and their differentiated descendants.

ABSTRACTGenetic and genomic analysis in Drosophila suggests that hematopoietic progenitors likely transition into terminal fates via intermediate progenitors (IPs) with some characteristics of either, but perhaps maintaining IP-specific markers. In the past, IPs have not been directly visualized and investigated owing to lack of appropriate genetic tools. Here, we report a Split GAL4 construct, CHIZ-GAL4, that identifies IPs as cells physically juxtaposed between true progenitors and differentiating hemocytes. IPs are a distinct cell type with a unique cell-cycle profile and they remain multipotent for all blood cell fates. In addition, through their dynamic control of the Notch ligand Serrate, IPs specify the fate of direct neighbors. The Ras pathway controls the number of IP cells and promotes their transition into differentiating cells. This study suggests that it would be useful to characterize such intermediate populations of cells in mammalian hematopoietic systems.