Modulation of intestinal epithelial permeability by chronic small intestinal helminth infections.

Increased permeability of the intestinal epithelial layer is linked to the pathogenesis and perpetuation of a wide range of intestinal and extra-intestinal diseases. Infecting humans with controlled doses of helminths, such as human hookworm (termed hookworm therapy), is proposed as a treatment for many of the same diseases. Helminths induce immunoregulatory changes in their host which could decrease epithelial permeability, which is highlighted as a potential mechanism through which helminths treat disease. Despite this, the influence of a chronic helminth infection on epithelial permeability remains unclear. This study uses the chronically infecting intestinal helminth Heligmosomoides polygyrus to reveal alterations in the expression of intestinal tight junction proteins and epithelial permeability during the infection course. In the acute infection phase (1 week postinfection), an increase in intestinal epithelial permeability is observed. Consistent with this finding, jejunal claudin-2 is upregulated and tricellulin is downregulated. By contrast, in the chronic infection phase (6 weeks postinfection), colonic claudin-1 is upregulated and epithelial permeability decreases. Importantly, this study also investigates changes in epithelial permeability in a small human cohort experimentally challenged with the human hookworm, Necator americanus. It demonstrates a trend toward small intestinal permeability increasing in the acute infection phase (8 weeks postinfection), and colonic and whole gut permeability decreasing in the chronic infection phase (24 weeks postinfection), suggesting a conserved epithelial response between humans and mice. In summary, our findings demonstrate dynamic changes in epithelial permeability during a chronic helminth infection and provide another plausible mechanism by which chronic helminth infections could be utilized to treat disease.

A guideline for the appropriate recognition of shared resource laboratories in publication.

The issue of what level of contribution warrants authorship, determining a fair order of authors and when and whom to acknowledge in publications is often a cause of debate, and in some instances, has also been a focus of conflict at certain institutions. Shared resource laboratories (SRLs) play a fundamental role in supporting publications, and SRL staff scientists can contribute to numerous areas such as experimental design, sample preparation, data acquisition, data analysis and manuscript drafting and review. However, SRL staff scientists are often unfairly omitted from the author list. To avoid SRLs and SRL staff scientist contributions going unnoticed, the authors have formulated a set of guidelines to aid in the conceptualization and recognition of the technical and intellectual contributions of SRLs. As a better understanding of the role SRL staff scientists play in the achievement of the scientific lead's experimental aims will foster a positive feedback loop, where acknowledgements can lead to more support and funding for SRLs and more engaged SRL staff capable of supporting discoveries and technological innovations that underpin major advancements in the field of life sciences.

Histopathological changes in the greenshell mussel, Perna canaliculus, in response to chronic thermal stress.

Climate change associated temperature challenges pose a serious threat to the marine environment. Elevations in average sea surface temperatures are occurring and increasing frequency of marine heatwaves resulting in mortalities of organisms are being reported. In recent years, marine farmers have reported summer mass mortality events of the New Zealand Greenshell mussel, Perna canaliculus, during the summer months; however, the etiological agents have yet to be determined. To elucidate the role of thermal stress, adult P. canaliculus were exposed to three chronic temperature treatments: a benign control of 17 °C and stressful elevations of 21 °C and 24 °C. Eight mussels per treatment were collected each month throughout a 14-month challenge period to identify and investigate histopathological differences among P. canaliculus populations exposed to the three temperatures. Histopathology revealed several significant deleterious alterations to tissues associated with temperature and exposure time. Increasing temperature and progression of time resulted in 1) an increase in the number of focal lipofuscin-ceroid aggregations, 2) an increase in focal hemocytosis, 3) an increase in the thickness of the sub-epithelial layer of the intestinal tract and 4) a decreased energy reserve cell (glycogen) coverage in the mantle. Prolonged exposure, irrespective of temperature, impacted gametogenesis, which was effectively arrested. Furthermore, increased levels of the heat shock protein 70 kDa (HSP 70) were seen in gill and gonad from thermally challenged mussels. The occurrence of the parasite Perkinsus olseni at month 5 in the 24 °C treatment, and month 7 at 21 °C was unexpected and may have exacerbated the fore-mentioned tissue conditions. Prolonged exposure to stable thermal conditions therefore appears to impact P. canaliculus, tissues with implications for broodstock captivity. Mussels experiencing elevated, temperatures of 21 and 24 °C demonstrated more rapid pathological signs. This research provides further insight into the complex host-pathogen-environment interactions for P. canaliculus in response to prolonged elevated temperature.

Basophils promote barrier dysfunction and resolution in the atopic skin.

BACKGROUND: The type 2 cytokines IL-4 and IL-13 promote not only atopic dermatitis (AD) but also the resolution of inflammation. How type 2 cytokines participate in the resolution of AD is poorly known. OBJECTIVE: Our aim was to determine the mechanisms and cell types governing skin inflammation, barrier dysfunction, and resolution of inflammation in a model of AD. METHODS: Mice that exhibit expression of IL-4, IL-13, and MCPT8 or that could be depleted of basophils or eosinophils, be deficient in IL-4 or MHC class II molecules, or have basophils lacking macrophage colony-stimulating factor (M-CSF) were treated with calcipotriol (MC903) as an acute model of AD. Kinetics of the disease; keratinocyte differentiation; and leukocyte accumulation, phenotype, function, and cytokine production were measured by transepidermal water loss, histopathology, molecular biology, or unbiased analysis of spectral flow cytometry. RESULTS: In this model of AD, basophils were activated systemically and were the initial and main source of IL-4 in the skin. Basophils and IL-4 promoted epidermal hyperplasia and skin barrier dysfunction by acting on keratinocyte differentiation during inflammation. Basophils, IL-4, and basophil-derived M-CSF inhibited the accumulation of proinflammatory cells in the skin while promoting the expansion and function of proresolution M2-like macrophages and the expression of probarrier genes. Basophils kept their proresolution properties during AD resolution. CONCLUSION: Basophils can display both beneficial and detrimental type 2 functions simultaneously during atopic inflammation.

MR1-dependent immune surveillance of the skin contributes to pathogenesis and is a photobiological target of UV light therapy in a mouse model of atopic dermatitis.

BACKGROUND: Mucosal-associated invariant T (MAIT) cells are unconventional T cells which recognize microbial metabolites presented by the major histocompatibility complex class I-related molecule MR1. Although MAIT cells have been shown to reside in human and murine skin, their contribution to atopic dermatitis (AD), an inflammatory skin disease associated with barrier dysfunction and microbial translocation, has not yet been determined. METHODS: Genetic deletion of MR1 and topical treatment with inhibitory MR1 ligands, which result in the absence and functional inhibition of MAIT cells, respectively, were used to investigate the role of MR1-dependent immune surveillance in a MC903-driven murine model of AD. RESULTS: The absence or inhibition of MR1 arrested AD disease progression through the blockade of both eosinophil activation and recruitment of IL-4- and IL-13-producing cells. In addition, the therapeutic efficacy of phototherapy against MC903-driven AD could be increased with prior application of folate, which photodegrades into the inhibitory MR1 ligand 6-formylpterin. CONCLUSION: We identified MAIT cells as sentinels and mediators of cutaneous type 2 immunity. Their pathogenic activity can be inhibited by topical application or endogenous generation, via phototherapy, of inhibitory MR1 ligands.

Thymic stromal lymphopoietin drives the development of IL-13+ Th2 cells.

T helper 2 (Th2) cells are pivotal in the development of allergy. Allergen exposure primes IL-4+ Th2 cells in lymph node, but production of effector cytokines including IL-5 and IL-13 is thought to require additional signals from antigen and the environment. Here we report that a substantial proportion of naive CD4+ T cells in spleen and lymph node express receptors for the epithelium-derived inflammatory cytokine thymic stromal lymphopoietin (TSLP). Culture of naive CD4+ T cells in anti-(a)CD3, aCD28, and TSLP-supplemented Th2 conditions enabled the development of a unique population of IL-13-single positive (IL-13-SP) CD4+ T cells; TSLP and Th2 conditions were both required for their development. Sorting experiments revealed that IL-13-SP Th2 cells originated from IL-4-negative precursors and coexpressed transcripts for the Th2 cytokines IL-5 and IL-9. In vivo, high TSLP levels acted directly on CD4+ T cells to induce the development of IL-13-SP and IL-4+IL-13+ double-positive populations in lymph node. These cells were phenotypically similar to Th2 effector cells and were CXCR5lowPD1low and expressed low levels of Bcl6 and Il21 transcripts and high levels of Gata3, Il3, and Il5 Our findings suggest a role of TSLP in directly promoting Th2 cell effector function and support the notion of TSLP as a key driver of Th2 inflammation.

A novel blood-feeding detoxification pathway in Nippostrongylus brasiliensis L3 reveals a potential checkpoint for arresting hookworm development.

As part of on-going efforts to control hookworm infection, the "human hookworm vaccine initiative" has recognised blood feeding as a feasible therapeutic target for inducing immunity against hookworm infection. To this end, molecular approaches have been used to identify candidate targets, such as Necator americanus (Na) haemoglobinase aspartic protease-1 (APR-1), with immunogenicity profiled in canine and hamster models. We sought to accelerate the immune analysis of these identified therapeutic targets by developing an appropriate mouse model. Here we demonstrate that Nippostrongylus brasiliensis (Nb), a phylogenetically distant strongylid nematode of rodents, begins blood feeding early in its development and that immunisation with Na-APR-1 can block its growth and completion of its life cycle. Furthermore, we identify a new haem detoxification pathway in Nb required for blood feeding that can be blocked by drugs of the quinolone family, reducing both infection burden and the associated anaemia in rodents. Collectively, our findings show that haem metabolism has potential as a checkpoint for interrupting hookworm development in early stages of the hookworm life cycle and that the Nippostrongylus brasiliensis rodent model is relevant for identifying novel therapeutic targets against human hookworm.

Genetic regulation of antibody responsiveness to immunization in substrains of BALB/c mice.

Antibody-mediated immunity is highly protective against disease. The majority of current vaccines confer protection through humoral immunity, but there is high variability in responsiveness across populations. Identifying immune mechanisms that mediate low antibody responsiveness may provide potential strategies to boost vaccine efficacy. Here, we report diverse antibody responsiveness to unadjuvanted as well as adjuvanted immunization in substrains of BALB/c mice, resulting in high and low antibody response phenotypes. Furthermore, these antibody phenotypes were not affected by changes in environmental factors such as the gut microbiota composition. Antigen-specific B cells following immunization had a marked difference in capability to class switch, resulting in perturbed IgG isotype antibody production. In vitro, a B-cell intrinsic defect in the regulation of class-switch recombination was identified in mice with low IgG antibody production. Whole genome sequencing identified polymorphisms associated with the magnitude of antibody produced, and we propose candidate genes that may regulate isotype class-switching capability. This study highlights that mice sourced from different vendors can have significantly altered humoral immune response profiles, and provides a resource to interrogate genetic regulators of antibody responsiveness. Together these results further our understanding of immune heterogeneity and suggest additional research on the genetic influences of adjuvanted vaccine strategies is warranted for enhancing vaccine efficacy.

Residual OXPHOS is required to drive primary and metastatic lung tumours in an orthotopic breast cancer model.

Background: Fast adaptation of glycolytic and mitochondrial energy pathways to changes in the tumour microenvironment is a hallmark of cancer. Purely glycolytic ρ0 tumour cells do not form primary tumours unless they acquire healthy mitochondria from their micro-environment. Here we explored the effects of severely compromised respiration on the metastatic capability of 4T1 mouse breast cancer cells. Methods: 4T1 cell lines with different levels of respiratory capacity were generated; the Seahorse extracellular flux analyser was used to evaluate oxygen consumption rates, fluorescent confocal microscopy to assess the number of SYBR gold-stained mitochondrial DNA nucleoids, and the presence of the ATP5B protein in the cytoplasm and fluorescent in situ nuclear hybridization was used to establish ploidy. MinION nanopore RNA sequence analysis was used to compare mitochondrial DNA transcription between cell lines. Orthotopic injection was used to determine the ability of cells to metastasize to the lungs of female Balb/c mice. Results: OXPHOS-deficient ATP5B-KO3.1 cells did not generate primary tumours. Severely OXPHOS compromised ρ0D5 cells generated both primary tumours and lung metastases. Cells generated from lung metastasis of both OXPHOS-competent and OXPHOS-compromised cells formed primary tumours but no metastases when re-injected into mice. OXPHOS-compromised cells significantly increased their mtDNA content, but this did not result in increased OXPHOS capacity, which was not due to decreased mtDNA transcription. Gene set enrichment analysis suggests that certain cells derived from lung metastases downregulate their epithelial-to-mesenchymal related pathways. Conclusion: In summary, OXPHOS is required for tumorigenesis in this orthotopic mouse breast cancer model but even very low levels of OXPHOS are sufficient to generate both primary tumours and lung metastases.

Skin Whole-Mount Immunofluorescent Staining Protocol, 3D Visualization, and Spatial Image Analysis.

The use of polychromatic immunofluorescent staining on whole-mount skin enables cell type characterization and aids in the delineation of the physiological and immunological strategies used by the skin to combat pathogens. Using whole-mount skin for polychromatic immunofluorescent staining removes the need for histological sectioning and enables the visualization of anatomical structures and immune cell types in three dimensions. Here we present a detailed protocol for immunostaining with fluorescence-conjugated primary antibodies in whole-mount skin to reveal structural landmarks and specific immune cell types using confocal laser scanning microscopy (CLSM) (Basic Protocol 1). The optimized staining panel reveals structural features such as blood vessels (CD31 antibody) and the lymphatic network (LYVE-1 antibody), in combination with MHCII antibodies for antigen-presenting cells (APCs), CD64 for macrophages and monocytes, CD103 for dendritic epidermal T cells (DETC), and CD326 for Langerhans cells (LC). Basic Protocol 2 describes image visualization pipelines using open-source software (ImageJ/FIJI), enabling four visualization options (z-projections, orthogonal views, 3D visualization, and animation). Basic Protocol 3 describes a quantitative analysis pipeline using CellProfiler to characterize the spatial relationship between cell types using mathematical indices such as Spatial Distribution Index (SDI), Neighborhood Frequency (NF), and Normalized Median Evenness (NME). These protocols will enable researchers to stain, record, analyze, and interpret data from whole-mount skin using commercially available reagents in a CLSM-equipped laboratory and freely available analysis software. © 2023 Wiley Periodicals LLC. Basic Protocol 1: Immunofluorescent staining and imaging for whole-mount mouse skin Basic Protocol 2: File rendering and visualization using FIJI Basic Protocol 3: Spatial image analysis using CellProfiler.

How to Build an Image-Processing Pipeline for Automating Multiparameter Histocytometry Analysis.

Until relatively recently, analysis of imaging data has been primarily quantitative and limited to 3-4 markers. The advancement of various technologies overcoming this marker limitation provided the capability of analyzing multiparameter imaging data down to the single cell level, termed histocytometry. Currently, most published end-to-end histocytometric analysis of imaging data is performed using expensive commercial programs or freely available analysis packages that require significant knowledge of programming languages for execution. Here we present a protocol that performs cell segmentation, phenotyping and spatial analysis, using software with easy-to-use GUIs (graphical user interfaces). These protocols allow the user to derive spatial and phenotypical data for the analysis of multiparameter microscopic images from most imaging platforms in a low-cost manner. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Cell Segmentation and generation of histocytometric .csv file Basic Protocol 2: Phenotyping of cell populations Basic Protocol 3: Spatial relationship analyses of phenotyped populations Support Protocol 1: Nuclei Segmentation Accuracy Test Support Protocol 2: Correcting y-axis Inversion of Histocytometry Data Relative to Original Image File.

Implementing High Dimensional Reduction Analysis on Histocytometric Data.

In a previous protocol article, we demonstrated construction of a histocytometry pipeline that is capable of both segmenting highly aggregated cell populations and retaining the original intensity data range of the input microscopy images. In the protocol presented here, using the output from the aforementioned article, we demonstrate how to phenotype the data using the high dimensional reduction analysis technique optimized t-distributed stochastic neighbor embedding (opt-t-SNE) and compare it to traditional manual gating. Additionally, we present a protocol illustrating the advantage of the inclusion of cell junction/membrane markers for accurately segmenting highly aggregated cell populations in ilastik. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Phenotyping lymph node populations using manual gating Basic Protocol 2: Phenotyping lymph node populations using t-SNE dimensional reduction Support Protocol: ilastik segmentation using a pan marker.

Creation of High-Dimensional Reduction Analysis-Compatible Histocytometry Files from Images of Densely-Packed Cells and/or Variable Stain Intensity.

The power of high-dimensional reduction techniques using multiparameter images has been demonstrated across a variety of different publications. Recently, we published an end-to-end low-cost GUI-based protocol for performing histocytometric spatial analysis on images derived from the most common microscope image formats. However, this protocol is limited by the normalized marker intensity outputs and the difficulty in processing images of highly aggregated and/or exceptionally heterogenous cell populations. Here we present the basic protocols required to construct an advanced histocytometric data file using only freeware. This data file is compatible with images containing cell nuclei clusters that are difficult to segment, and results in histocytometry files retaining the original marker intensity values of the microscopic images they were derived from. This is especially useful in cells that are phenotyped based on relative marker expression levels. Histocytometry data files produced by these protocols are compatible with high-dimensional reduction analysis using marker intensity data, such as tSNEs. This methodology is showcased using stitched microscopic images of murine lymph nodes, complex organs with highly aggregated heterogenous cell populations, that are typically difficult to segment. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Image preprocessing and generation of nuclei marker probability maps Basic Protocol 2: Cell segmentation using ilastik-derived probability maps Basic Protocol 3: Generation of histocytometric .fcs files.

Intratumoural administration of an NKT cell agonist with CpG promotes NKT cell infiltration associated with an enhanced antitumour response and abscopal effect.

Intratumoural administration of unmethylated cytosine-phosphate-guanine motifs (CpG) to stimulate toll-like receptor (TLR)-9 has been shown to induce tumour regression in preclinical studies and some efficacy in the clinic. Because activated natural killer T (NKT) cells can cooperate with pattern-recognition via TLRs to improve adaptive immune responses, we assessed the impact of combining a repeated dosing regimen of intratumoural CpG with a single intratumoural dose of the NKT cell agonist α-galactosylceramide (α-GalCer). The combination was superior to CpG alone at inducing regression of established tumours in several murine tumour models, primarily mediated by CD8+ T cells. An antitumour effect on distant untreated tumours (abscopal effect) was reliant on sustained activity of NKT cells and was associated with infiltration of KLRG1+ NKT cells in tumours and draining lymph nodes at both injected and untreated distant sites. Cytometric analysis pointed to increased exposure to type I interferon (IFN) affecting many immune cell types in the tumour and lymphoid organs. Accordingly, antitumour activity was lost in animals in which dendritic cells (DCs) were incapable of signaling through the type I IFN receptor. Studies in conditional ablation models showed that conventional type 1 DCs and plasmacytoid DCs were required for the response. In tumour models where the combined treatment was less effective, the addition of tumour-antigen derived peptide, preferably conjugated to α-GalCer, significantly enhanced the antitumour response. The combination of TLR ligation, NKT cell agonism, and peptide delivery could therefore be adapted to induce responses to both known and unknown antigens.

Glycolipid-peptide conjugate vaccines elicit CD8+ T-cell responses and prevent breast cancer metastasis.

Objectives: Metastasis is the principal cause of breast cancer mortality. Vaccines targeting breast cancer antigens have yet to demonstrate clinical efficacy, and there remains an unmet need for safe and effective treatment to reduce the risk of metastasis, particularly for people with triple-negative breast cancer (TNBC). Certain glycolipids can act as vaccine adjuvants by specifically stimulating natural killer T (NKT) cells to provide a universal form of T-cell help. Methods: We designed and made a series of conjugate vaccines comprising a prodrug of the NKT cell-activating glycolipid α-galactosylceramide covalently linked to tumor-expressed peptides, and assessed these using E0771- and 4T1-based breast cancer models in vivo. We employed peptides from the model antigen ovalbumin and from clinically relevant breast cancer antigens HER2 and NY-ESO-1. Results: Glycolipid-peptide conjugate vaccines that activate NKT cells led to antigen-presenting cell activation, induced inflammatory cytokines, and, compared with peptide alone or admixed peptide and α-galactosylceramide, specifically enhanced CD8+ T-cell responses against tumor-associated peptides. Primary tumor growth was delayed by vaccination in all tumor models. Using 4T1-based cell lines expressing HER2 or NY-ESO-1, a single administration of the relevant conjugate vaccine prevented tumor colonisation of the lung following intravenous inoculation of tumor cells or spontaneous metastasis from breast, respectively. Conclusion: Glycolipid-peptide conjugate vaccines that activate NKT cells prevent lung metastasis in breast cancer models and warrant investigation as adjuvant therapies for high-risk breast cancer.

High-Dimensional Image Analysis using Histocytometry.

Histocytometry is a technique for processing multiparameter microscopy images using computational approaches to identify and quantify cellular phenotypes. It allows for spatial analyses of cellular phenotypes in relation to each other and within defined spatial regions. The benefit of this technique over manual annotation and characterization of cells is a high degree of automation/throughput, significantly decreased user bias, and increased reproducibility. Recently, an increase in freely available software amenable to or deliberately designed for histocytometry has resulted in these complex analyses being available to a broader base of users who have amassed multi-component microscopic imaging data. This article provides an overview of a histocytometry pipeline, focusing on the strategic planning and software requirements to allow readers to perform cell segmentation, phenotyping, and spatial analyses to advance their research outputs. © 2021 Wiley Periodicals LLC.

A new method to localise and quantify oxidative stress in live juvenile mussels.

Stress and survival of the juvenile New Zealand green-lipped mussel, Perna canaliculus, is a poorly understood bottleneck in the ecological and economic performance of a significant aquaculture crop. This species was therefore selected as a model organism for the development of a new method to quantify oxidative stress in whole individuals. An in vivo ROS-activated stain (CellROX™) was administered to anaesthetised, translucent juveniles that were subsequently formaldehyde fixed and then visualised using confocal microscopy. Subsequent application of image analysis to quantifying ROS-positive tissue areas was successfully used to detect stress differences in juvenile mussels exposed to varying levels of emersion. This integrated method can be used to localise and quantify ROS production in individual translucent bivalve life stages (larval and juvenile), while relative stability following fixation greatly expands potential practical field applications. This article has an associated First Person interview with the first and third authors of the paper.

The Gastrointestinal Helminth Heligmosomoides bakeri Suppresses Inflammation in a Model of Contact Hypersensitivity.

Helminths regulate host immune responses to ensure their own long-term survival. Numerous studies have demonstrated that these helminth-induced regulatory mechanisms can also limit host inflammatory responses in several disease models. We used the Heligmosomoides bakeri (Hb) infection model (also known as H. polygyrus or H. polygyrus bakeri in the literature) to test whether such immune regulation affects skin inflammatory responses induced by the model contact sensitiser dibutyl phthalate fluorescein isothiocynate (DBP-FITC). Skin lysates from DBP-FITC-sensitized, Hb-infected mice produced less neutrophil specific chemokines and had significantly reduced levels of skin thickening and cellular inflammatory responses in tissue and draining lymph nodes (LNs) compared to uninfected mice. Hb-induced suppression did not appear to be mediated by regulatory T cells, nor was it due to impaired dendritic cell (DC) activity. Mice cleared of infection remained unresponsive to DBP-FITC sensitization indicating that suppression was not via the secretion of Hb-derived short-lived regulatory molecules, although long-term effects on cells cannot be ruled out. Importantly, similar helminth-induced suppression of inflammation was also seen in the draining LN after intradermal injection of the ubiquitous allergen house dust mite (HDM). These findings demonstrate that Hb infection attenuates skin inflammatory responses by suppressing chemokine production and recruitment of innate cells. These findings further contribute to the growing body of evidence that helminth infection can modulate inflammatory and allergic responses via a number of mechanisms with potential to be exploited in therapeutic and preventative strategies in the future.

Dermal IRF4+ dendritic cells and monocytes license CD4+ T helper cells to distinct cytokine profiles.

Antigen (Ag)-presenting cells (APC) instruct CD4+ helper T (Th) cell responses, but it is unclear whether different APC subsets contribute uniquely in determining Th differentiation in pathogen-specific settings. Here, we use skin-relevant, fluorescently-labeled bacterial, helminth or fungal pathogens to track and characterize the APC populations that drive Th responses in vivo. All pathogens are taken up by a population of IRF4+ dermal migratory dendritic cells (migDC2) that similarly upregulate surface co-stimulatory molecules but express pathogen-specific cytokine and chemokine transcripts. Depletion of migDC2 reduces the amount of Ag in lymph node and the development of IFNγ, IL-4 and IL-17A responses without gain of other cytokine responses. Ag+ monocytes are an essential source of IL-12 for both innate and adaptive IFNγ production, and inhibit follicular Th cell development. Our results thus suggest that Th cell differentiation does not require specialized APC subsets, but is driven by inducible and pathogen-specific transcriptional programs in Ag+ migDC2 and monocytes.