Sensory neurons: An integrated component of innate immunity

The sensory nervous system possesses the ability to integrate exogenous threats and endogenous signals to mediate downstream effector functions. Sensory neurons have been shown to activate or suppress host defense and immunity against pathogens, depending on the tissue and disease state. Through this lens, pro- and anti-inflammatory neuroimmune effector functions can be interpreted as evolutionary adaptations by host or pathogen. Here, we discuss recent and impactful examples of neuroimmune circuitry that regulate tissue homeostasis, autoinflammation, and host defense. Apparently paradoxical or conflicting reports in the literature also highlight the complexity of neuroimmune interactions that may depend on tissue- and microbe-specific cues. These findings expand our understanding of the nuanced mechanisms and the greater context of sensory neurons in innate immunity.

Neuroimmune interactions in atopic and allergic contact dermatitis

The skin is a barrier organ populated by many types of skin-resident immune cells and sensory neurons. It has become increasingly appreciated that neuroimmune interactions are an important component of inflammatory diseases such as atopic dermatitis and allergic contact dermatitis. Neuropeptides secreted from nerve terminals play an important role in mediating cutaneous immune cell function, and soluble mediators derived from immune cells interact with neurons to induce itch. In this review article, we will explore emerging research describing neuronal effector functions on skin immune cells in mouse models of atopic and contact dermatitis. We will also discuss the contributions of both specific neuronal subsets and secreted immune factors to itch induction and the associated inflammatory processes. Finally, we will explore how treatment strategies have emerged around these findings and discuss the relationship between scratching and dermatitis.

Local IL-23 is required for proliferation and retention of skin-resident memory TH17 cells

The cytokine interleukin-23 (IL-23) is critical for development and maintenance of autoimmune inflammation in nonlymphoid tissues; however, the mechanism through which IL-23 supports tissue-specific immunity remains unclear. In mice, we found that circulating memory T cells were dispensable for anamnestic protection from Candida albicans skin infection, and tissue-resident memory (TRM) cell-mediated protection from C. albicans reinfection required IL-23. Administration of anti-IL-23 receptor antibody to mice after resolution of primary C. albicans infection resulted in loss of CD69+ CD103+ tissue-resident memory T helper 17 (TRM17) cells from skin, and clinical anti-IL-23 therapy depleted TRM17 cells from skin of patients with psoriasis. IL-23 receptor blockade impaired TRM17 cell proliferation but did not affect apoptosis susceptibility or tissue egress. IL-23 produced by CD301b+ myeloid cells was required for TRM17 maintenance in skin after C. albicans infection, and CD301b+ cells were necessary for TRM17 expansion during the development of imiquimod dermatitis. This study demonstrates that locally produced IL-23 promotes in situ proliferation of cutaneous TRM17 cells to support their longevity and function and provides mechanistic insight into the durable efficacy of IL-23 blockade in the treatment of psoriasis.

TGFβ activating integrins β6 and β8 are dysregulated in inflammatory skin disease and cutaneous melanoma

BACKGROUND

Integrins avβ6 and avβ8 are expressed by keratinocytes and transactivate latent TGFβ. In a murine model, integrin mediated activation of TGFβ has been shown to be critical in maintaining skin homeostasis, specifically playing roles in epidermal retention of Langerhans cells and resident memory cells T cells (Trm).

OBJECTIVE

We examine expression of Integrins β6 and β8 in human skin, inflammatory skin disease, benign nevi, and melanoma and hypothesize that integrin expression is dysregulated in disease.

METHODS

Using immunohistochemistry, we stained tissue from normal human skin (n = 8), psoriasis (n = 6), atopic dermatitis (n = 6), lichen planus (n = 5), benign nevi (n = 24), and melanoma (n = 25) with anti-integrin β6 and anti-integrin β8 to survey expression pattern. We also performed a retrospective chart review in the melanoma cohort to examine if integrin β6 and β8 expression was associated with increased Breslow depth and worse prognostic staging.

RESULTS

Here, we show that human keratinocytes express integrins β6 and β8, similar to murine keratinocytes. We also found that inflammatory skin conditions have increased Integrin β6, but not Integrin β8 expression. Furthermore, we identified that melanomas have greatly increased expression of integrin β8 compared to nevi. Additionally, high expression of integrin β8 was correlated with greater Breslow depth at diagnosis and with worse prognostic staging.

CONCLUSION

These findings demonstrate that like murine keratinocytes, human keratinocytes express integrin β6 and β8 under steady state conditions. Moreover, altered integrin expression may participate in the development or maintenance of cutaneous inflammation as well as tumor immune evasion.

Inflammatory thoughts can upset your guts

Peripheral neurons and immune cells interact to modulate inflammation, but whether the brain can control this process is unknown. In a recent issue of Cell, Koren et al. (2021) show that peripheral inflammation is encoded in the insular cortex and that later re-activation of these neurons triggers inflammation.

TNF-α and IL-1β Do Not Induce Langerhans Cell Migration by Inhibiting TGFβ Activation

In the skin, Langerhans cells (LCs) require autocrine latent TGFβ that is transactivated by the integrins ανβ6 and ανβ8 expressed by keratinocytes (KCs) for long-term epidermal retention. Selective expression of a ligand-independent, constitutively active form of TGFβR1 inhibits LC migration during homeostasis and in response to UVB exposure. In this study, we found that LC migration in response to inflammatory stimuli was also inhibited by ligand-independent TGFβR1 signaling. Contrary to UVB stimulation, which reduced KC expression of ανβ6, in vitro and in vivo exposure to TNF-α or IL-1β increased ανβ6 transcript and protein expression by KCs. This resulted in increased KC-mediated transactivation of latent TGFβ. Expression of ανβ8 was largely unchanged. These findings show that ligand-independent TGFβR1 signaling in LCs can overcome inflammatory migration stimuli, but reduced KC-mediated transactivation of latent TGFβ by KCs may only drive LC migration during homeostasis and in response to UV stimulation.

Dual function of Langerhans cells in skin TSLP-promoted TFH differentiation in mouse atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is among the most common chronic inflammatory skin diseases, usually occurring early in life, and often preceding other atopic diseases such as asthma. TH2 has been believed to play a crucial role in cellular and humoral response in AD, but accumulating evidence has shown that follicular helper T cell (TFH), a critical player in humoral immunity, is associated with disease severity and plays an important role in AD pathogenesis.

OBJECTIVES

This study aimed at investigating how TFHs are generated during the pathogenesis of AD, particularly what is the role of keratinocyte-derived cytokine TSLP and Langerhans cells (LCs).

METHODS

Two experimental AD mouse models were employed: (1) triggered by the overproduction of TSLP through topical application of MC903, and (2) induced by epicutaneous allergen ovalbumin (OVA) sensitization.

RESULTS

This study demonstrated that the development of TFHs and germinal center (GC) response were crucially dependent on TSLP in both the MC903 model and the OVA sensitization model. Moreover, we found that LCs promoted TFH differentiation and GC response in the MC903 model, and the depletion of Langerin+ dendritic cells (DCs) or selective depletion of LCs diminished the TFH/GC response. By contrast, in the model with OVA sensitization, LCs inhibited TFH/GC response and suppressed TH2 skin inflammation and the subsequent asthma. Transcriptomic analysis of Langerin+ and Langerin- migratory DCs revealed that Langerin+ DCs became activated in the MC903 model, whereas these cells remained inactivated in OVA sensitization model.

CONCLUSIONS

Together, these studies revealed a dual functionality of LCs in TSLP-promoted TFH and TH2 differentiation in AD pathogenesis.

Oral mucosal IL-22/STAT3 signaling licenses IL-17-mediated immunity to oral candidiasis

Oropharyngeal candidiasis (OPC) is an opportunistic infection of the oral mucosa caused by the commensal fungus Candida albicans. IL-17 and IL-22 both mediate antifungal immunity yet activate distinct downstream signaling pathways. While much is known about IL-17-dependent immunity in OPC, the activities of IL-22 are less well delineated. We show that induction of Il22 is independent of Dectin-1, CARD9 and aryl hydrocarbon receptor (AhR) and is driven by IL-23 and the C. albicans pore forming peptide candidalysin. Despite similar induction requirements and cellular sources, IL-22 and IL-17 function non-redundantly during OPC and exert opposing roles in neutrophil recruitment. The IL-22 and IL-17 receptors are required in anatomically distinct locations; loss of IL-22RA1 in the oral basal epithelial layer (BEL) but not the suprabasal epithelial layer (SEL) causes susceptibility to OPC, whereas IL-17RA is needed in the SEL. Our data reveal that IL-22 is a major activator of STAT3 in the BEL during OPC. Moreover, loss of STAT3 in the BEL but not the SEL renders mice susceptible to OPC. Transcriptional profiling of RNASeq data linked IL-22/STAT3 to oral epithelial cell proliferation and survival, but also, unexpectedly, to driving an IL-17 gene signature. We show that IL-22 acts on the BEL to replenish the IL-17RA-expressing SEL, thereby restoring the ability of the oral epithelium to respond to IL-17. Consequently, IL-22 signaling in BEL ‘licenses’ IL-17R signaling in the oral epithelium, revealing spatially distinct yet cooperative activities of IL-22 and IL-17 in oral candidiasis. This work also suggests that oral thrush in Jobs’ syndrome patients may be caused by STAT3 impairments in the oral epithelium, not just Th17 cells.

IL-23 maintains tissue resident memory Th17 cells in murine and psoriatic skin

Tissue resident memory Th17 cells (TRM17) are the key cell type driving the chronic skin inflammation of psoriasis. Although IL-23 is strongly associated with autoimmunity and chronic inflammatory disorders including psoriasis, and anti-IL-23 biologic agents have remarkable efficacy in the treatment of psoriasis, the precise role of IL-23 in supporting IL-17-mediated skin inflammation remains unclear. In mice, we found that circulating memory T cells were dispensable for anamnestic protection from C. albicans skin infection, and TRM17 mediated protection from C. albicans reinfection required IL-23. Administration of anti-IL-23R antibody to dual Il17aCre Rosa26CAG-fl/fl-tdTomato Il17fThy1.1/Thy1.1 (17Fate) fate reporter mice following resolution of primary C. albicans infection resulted in a selective reduction in the number of CD69+CD103+TRM17 cells in skin compared with isotype controls. TRM17 proliferation was reduced and survival was unaffected. CD301b+ dermal dendritic cells (dDC) were an obligate source of IL-23 that supported TRM17 maintenance in skin after C. albicans challenge. These data demonstrate that locally produced IL-23 promotes in situ TRM17 proliferation to support their long term retention in skin. In normal human skin, we identified dermal cDC2 as the principal source of IL-23, although keratinocytes and CD4+ T cells were additional sources of IL-23 in psoriasis skin. Analysis of human psoriasis skin before and after clinical anti-IL-23 therapy revealed reduced TRM17 number and proliferation index, suggesting that targeted depletion of pathogenic TRM17 is the major mechanism by which anti-IL-23 therapy induces uniquely durable disease-free intervals in psoriasis patients.

Gut Helicobacter presentation by multiple dendritic cell subsets enables context-specific regulatory T cell generation

Generation of tolerogenic peripheral regulatory T (pTreg) cells is commonly thought to involve CD103⁺ gut dendritic cells (DCs), yet their role in commensal-reactive pTreg development is unclear. Using two Helicobacter-specific T cell receptor (TCR) transgenic mouse lines, we found that both CD103⁺ and CD103^- migratory, but not resident, DCs from the colon-draining mesenteric lymph node presented Helicobacter antigens to T cells ex vivo. Loss of most CD103⁺ migratory DCs in vivo using murine genetic models did not affect the frequency of Helicobacter-specific pTreg cell generation or induce compensatory tolerogenic changes in the remaining CD103^- DCs. By contrast, activation in a Th1-promoting niche in vivo blocked Helicobacter-specific pTreg generation. Thus, these data suggest a model where DC-mediated effector T cell differentiation is 'dominant', necessitating that all DC subsets presenting antigen are permissive for pTreg cell induction to maintain gut tolerance.

Competition for Active TGFβ Cytokine Allows for Selective Retention of Antigen-Specific Tissue- Resident Memory T Cells in the Epidermal Niche

Following antigen-driven expansion in lymph node, transforming growth factor-β (TGFβ) is required for differentiation of skin-recruited CD8⁺ T cell effectors into epidermal resident memory T (Trm) cells and their epidermal persistence. We found that the source of TGFβ -supporting Trm cells was autocrine. In addition, antigen-specific Trm cells that encountered cognate antigen in the skin, and bystander Trm cells that did not, both displayed long-term persistence in the epidermis under steady-state conditions. However, when the active-TGFβ was limited or when new T cell clones were recruited into the epidermis, antigen-specific Trm cells were more efficiently retained than bystander Trm cells. Genetically enforced TGFβR signaling allowed bystander Trm cells to persist in the epidermis as efficiently as antigen-specific Trm cells in both contexts. Thus, competition between T cells for active TGFβ represents an unappreciated selective pressure that promotes the accumulation and persistence of antigen-specific Trm cells in the epidermal niche.

Single-Cell Profiling Reveals Divergent, Globally Patterned Immune Responses in Murine Skin Inflammation

Inflammatory response heterogeneity has impeded high-resolution dissection of diverse immune cell populations during activation. We characterize mouse cutaneous immune cells by single-cell RNA sequencing, after inducing inflammation using imiquimod and oxazolone dermatitis models. We identify 13 CD45⁺ subpopulations, which broadly represent most functionally characterized immune cell types. Oxazolone pervasively upregulates Jak2/Stat3 expression across T cells and antigen-presenting cells (APCs). Oxazolone also induces Il4/Il13 expression in newly infiltrating basophils, and Il4ra and Ccl24, most prominently in APCs. In contrast, imiquimod broadly upregulates Il17/Il22 and Ccl4/Ccl5. A comparative analysis of single-cell inflammatory transcriptional responses reveals that APC response to oxazolone is tightly restricted by cell identity, whereas imiquimod enforces shared programs on multiple APC populations in parallel. These global molecular patterns not only contrast immune responses on a systems level but also suggest that the mechanisms of new sources of inflammation can eventually be deduced by comparison to known signatures.

•

Oxazolone pervasively upregulates Jak2/Stat3 expression across T cells and APCs

•

Il4/Il13 induction in skin by oxazolone is dominated by infiltrating basophils

•

Imiquimod broadly increases Il17/Il22 and Ccl4/Ccl5, extending to non-T cells

•

Oxazolone induces more highly compartmentalized immune cell responses than imiquimod

Joint AAD-NPF Guidelines of care for the management and treatment of psoriasis with topical therapy and alternative medicine modalities for psoriasis severity measures

Psoriasis is a chronic, inflammatory, multisystem disease that affects up to 3.2% of the United States population. This guideline addresses important clinical questions that arise in psoriasis management and care and provides recommendations based on the available evidence. The treatment of psoriasis with topical agents and with alternative medicine will be reviewed, emphasizing treatment recommendations and the role of dermatologists in monitoring and educating patients regarding benefits as well as risks that may be associated. This guideline will also address the severity assessment methods of psoriasis in adults.

Neuronal Regulation of Cutaneous Immunity

The skin is innervated by numerous sensory afferent neurons that respond to a diverse array of stimuli ranging from gentle touch to noxious pain. Various features of the immune system-pathogen recognition, secretion of soluble mediators-are shared with the nervous system. This has led to the recognition that neurons share some functions with innate immune cells and have the capacity to recognize pathogens and participate in innate immune responses. Neuroimmune interactions are bidirectional. Soluble mediators from immune cells activate neurons and soluble mediators from neurons can activate immune cells. In this review, we will focus on the interplay between neurons and innate immunity in the skin in the context of host defense and inflammation.

An IL-17F.S65L Knock-In Mouse Reveals Similarities and Differences in IL-17F Function in Oral Candidiasis: A New Tool to Understand IL-17F

Oropharyngeal candidiasis (OPC) is an opportunistic infection of the oral mucosa caused by the commensal fungus Candida albicans IL-17R signaling is essential to prevent OPC in mice and humans, but the individual roles of its ligands, IL-17A, IL-17F, and IL-17AF, are less clear. A homozygous IL-17F deficiency in mice does not cause OPC susceptibility, whereas mice lacking IL-17A are moderately susceptible. In humans, a rare heterozygous mutation in IL-17F (IL-17F.S65L) was identified that causes chronic mucocutaneous candidiasis, suggesting the existence of essential antifungal pathways mediated by IL-17F and/or IL-17AF. To investigate the role of IL-17F and IL-17AF in more detail, we exploited this "experiment of nature" by creating a mouse line bearing the homologous mutation in IL-17F (Ser65Leu) by CRISPR/Cas9. Unlike Il17f^-/- mice that are resistant to OPC, Il17f^S65L/S65L mice showed increased oral fungal burdens similar to Il17a ^-/- mice. In contrast to humans, however, disease was only evident in homozygous, not heterozygous, mutant mice. The mutation was linked to modestly impaired CXC chemokine expression and neutrophil recruitment to the infected tongue but not to alterations in oral antimicrobial peptide expression. These findings suggest mechanisms by which the enigmatic cytokine IL-17F contributes to host defense against fungi. Moreover, because these mice do not phenocopy Il17f^-/- mice, they may provide a valuable tool to interrogate IL-17F and IL-17AF function in vivo in other settings.

Oral epithelial IL-22/STAT3 signaling licenses IL-17-mediated immunity to oral mucosal candidiasis

Oropharyngeal candidiasis (OPC; thrush) is an opportunistic infection caused by the commensal fungus Candida albicans Interleukin-17 (IL-17) and IL-22 are cytokines produced by type 17 lymphocytes. Both cytokines mediate antifungal immunity yet activate quite distinct downstream signaling pathways. While much is now understood about how IL-17 promotes immunity in OPC, the activities of IL-22 are far less well delineated. We show that, despite having similar requirements for induction from type 17 cells, IL-22 and IL-17 function nonredundantly during OPC. We find that the IL-22 and IL-17 receptors are required in anatomically distinct locations within the oral mucosa; loss of IL-22RA1 or signal transducer and activator of transcription 3 (STAT3) in the oral basal epithelial layer (BEL) causes susceptibility to OPC, whereas IL-17RA is needed in the suprabasal epithelial layer (SEL). Transcriptional profiling of the tongue linked IL-22/STAT3 not only to oral epithelial cell proliferation and survival but also, unexpectedly, to driving an IL-17-specific gene signature. We show that IL-22 mediates regenerative signals on the BEL that replenish the IL-17RA-expressing SEL, thereby restoring the ability of the oral epithelium to respond to IL-17 and thus to mediate antifungal events. Consequently, IL-22 signaling in BEL "licenses" IL-17 signaling in the oral mucosa, revealing spatially distinct yet cooperative activities of IL-22 and IL-17 in oral candidiasis.

Effector TH17 Cells Give Rise to Long-Lived TRM Cells that Are Essential for an Immediate Response against Bacterial Infection

Adaptive immunity provides life-long protection by generating central and effector memory T cells and the most recently described tissue resident memory T (T_RM) cells. However, the cellular origin of CD4 T_RM cells and their contribution to host defense remain elusive. Using IL-17A tracking-fate mouse models, we found that a significant fraction of lung CD4 T_RM cells derive from IL-17A-producing effector (T_H17) cells following immunization with heat-killed Klebsiella pneumonia (Kp). These exT_H17 T_RM cells are maintained in the lung by IL-7, produced by lymphatic endothelial cells. During a memory response, neither antibodies, γδ T cells, nor circulatory T cells are sufficient for the rapid host defense required to eliminate Kp. Conversely, using parabiosis and depletion studies, we demonstrated that exT_H17 T_RM cells play an important role in bacterial clearance. Thus, we delineate the origin and function of airway CD4 T_RM cells during bacterial infection, offering novel strategies for targeted vaccine design.

A naturally-occurring mutation in IL-17F reveals a protective role for the IL-17AF heterodimer in oropharyngeal candidiasis (OPC)

IL-17A is the original member of the IL-17 family of cytokines. Among the IL-17 family, IL-17F shares the most homology with IL-17A at the amino acid level. IL-17A and IL-17F exist as homodimers and also form a heterodimer (IL-17AF). All of these cytokine dimers signal through the same IL-17RA:IL-17RC receptor complex, but the ligands exhibit different signaling strengths (IL-17A > IL-17AF > IL-17F). We previously showed that IL-17 signaling is critical for immunity against oropharyngeal candidiasis (OPC), an opportunistic infection of the oral mucosa caused by the commensal fungus C. albicans. Mice lacking IL-17RA, IL-17RC, or the adaptor ACT1 all have higher oral fungal burdens than wild type (WT) following oral infection with C. albicans. IL-17A deficient mice are also mildly susceptible to C. albicans oral infection, but blockade of IL-17F does not cause disease susceptibility. Furthermore, double blockade of IL-17A and IL-17F during OPC reveals a cooperative antifungal activity of IL-17A and IL-17F. However, the role of the IL-17AF heterodimer still remains poorly understood. Here, we took advantage of a dominant-negative mutation (IL-17F.S65L) that was previously identified in chronic mucocutaneous candidiasis disease (CMCD) patients. This mutation blocks the signals of IL-17F and IL-17AF but not IL-17A. Using CRISPR/Cas9 technology, we created mice with the analogous IL-17F S65L mutation. These IL-17FS65L/S65L mice showed a similar degree of susceptibility as IL-17A−/− mice though less than IL-17RA−/− mice upon C. albicans oral infection. This result suggests that IL-17AF contributes to protection against OPC.

Constitutive TGFβ signaling prevents inflammation-induced Langerhans cell migration

Keratinocytes (KCs) that form the epidermis create a unique barrier niche for cells of the immune system such as Langerhans cells (LCs) and CD8+ resident memory T cells (TRM). These leukocytes provide host-defense but also initiate and maintain autoimmune skin diseases. Hence, elucidating the mechanisms by which CD8+ TRM and LC maintain epidermal residency is of great therapeutic interest. Both cell types require active TGFβ1 to maintain their steady-state epidermal retention. In the epidermis, inactive LAP-TGFβ1 is exclusively activated into active TGFβ1 by integrins ανβ6 and ανβ8 expressed by KCs. However, the relationship between TGFβ1 and LC migration in response to inflammatory stimuli remains unknown. To determine whether enforced TGFβ1 signaling can overcome inflammation-induce LC migration, we generated huLangerin-CreERT2x TGFβRI-CALxL mice (TGFβR1-CALC) that allow for tamoxifen-induced ligand-independent TGFβRI signaling. Enforced TGFβRI signaling in LC prevented migration in response to UVB, chemical haptens, C. albicans epicutaneous infection as well as dermal injection of TNFα and IL1β. LC from TGFβR1-CALC mice did not egress from the epidermis or enter the draining lymph nodes. Notably, in WT mice, we did not observe reduced KC expression of integrin ανβ6 or ανβ8 and levels of pSMAD2 in LC did not decrease in inflammatory contexts. Thus, although enforced TGFβRI signaling can overcome inflammation-induced migratory signals, but the loss of TGFβRI signaling is not required for LC migration. These data are consistent with a model in which TGFβRI signaling drives a LC-intrinsic retention program under homeostatic conditions that is overcome or inhibited by inflammatory cues.

Oral epithelial IL-22/STAT3 signaling licenses IL-17-mediated immunity to oral mucosal candidiasis

Oropharyngeal candidiasis (OPC) is an opportunistic infection of the oral mucosa caused by the commensal fungus Candida albicans. IL-17 and IL-22 both mediate antifungal immunity yet activate distinct downstream signaling pathways. While much is known about IL-17-dependent immunity in OPC, the activities of IL-22 are less well delineated. We show that induction of Il22 is independent of Dectin-1, CARD9 and aryl hydrocarbon receptor (AhR) and is driven by IL-23 and the C. albicans pore forming peptide candidalysin. Despite similar induction requirements and cellular sources, IL-22 and IL-17 function non-redundantly during OPC and exert opposing roles in neutrophil recruitment. The IL-22 and IL-17 receptors are required in anatomically distinct locations; loss of IL-22RA1 in the oral basal epithelial layer (BEL) but not the suprabasal epithelial layer (SEL) causes susceptibility to OPC, whereas IL-17RA is needed in the SEL. Our data reveal that IL-22 is a major activator of STAT3 in the BEL during OPC. Moreover, loss of STAT3 in the BEL but not the SEL renders mice susceptible to OPC. Transcriptional profiling of RNASeq data linked IL-22/STAT3 to oral epithelial cell proliferation and survival, but also, unexpectedly, to driving an IL-17 gene signature. We show that IL-22 acts on the BEL to replenish the IL-17RA-expressing SEL, thereby restoring the ability of the oral epithelium to respond to IL-17. Consequently, IL-22 signaling in BEL ‘licenses’ IL-17R signaling in the oral epithelium, revealing spatially distinct yet cooperative activities of IL-22 and IL-17 in oral candidiasis. This work also suggests that oral thrush in Jobs’ syndrome patients may be caused by STAT3 impairments in the oral epithelium, not just Th17 cells.

Joint American Academy of Dermatology-National Psoriasis Foundation guidelines of care for the management of psoriasis with systemic nonbiologic therapies

Psoriasis is a chronic inflammatory disease involving multiple organ systems and affecting approximately 2% of the world's population. In this guideline, we focus the discussion on systemic, nonbiologic medications for the treatment of this disease. We provide detailed discussion of efficacy and safety for the most commonly used medications, including methotrexate, cyclosporine, and acitretin, and provide recommendations to assist prescribers in initiating and managing patients on these treatments. Additionally, we discuss newer therapies, including tofacitinib and apremilast, and briefly touch on a number of other medications, including fumaric acid esters (used outside the United States) and therapies that are no longer widely used for the treatment of psoriasis (ie, hydroxyurea, leflunomide, mycophenolate mofetil, thioguanine, and tacrolimus).

Intimate neuro-immune interactions: breaking barriers between systems to make meaningful progress

The nervous system is often viewed as an isolated system that integrates information from the environment and host. Recently, there has been a renewed focus exploring the concept that the nervous system also communicates across biological systems. Specifically, several high profile studies have recently highlighted the importance of neuro-immune communication in the context of homeostasis, central nervous system disorders, host defense and injury. Here, we discuss the history of shared mechanisms and interconnectedness of the nervous, immune and epithelial compartments. In light of these overlapping mechanisms, it is perhaps unsurprising that neuro-immune-epithelial signaling plays a key role in regulating diverse biological phenomena. In this review, we explore recent breakthroughs in understanding neuro-immune signaling to highlight the importance of interdisciplinary approaches to biomedical research and the future development of novel therapeutics.

A protective Langerhans cell-keratinocyte axis that is dysfunctional in photosensitivity

Photosensitivity, or skin sensitivity to ultraviolet radiation (UVR), is a feature of lupus erythematosus and other autoimmune and dermatologic conditions, but the mechanistic underpinnings are poorly understood. We identify a Langerhans cell (LC)-keratinocyte axis that limits UVR-induced keratinocyte apoptosis and skin injury via keratinocyte epidermal growth factor receptor (EGFR) stimulation. We show that the absence of LCs in Langerin-diphtheria toxin subunit A (DTA) mice leads to photosensitivity and that, in vitro, mouse and human LCs can directly protect keratinocytes from UVR-induced apoptosis. LCs express EGFR ligands and a disintegrin and metalloprotease 17 (ADAM17), the metalloprotease that activates EGFR ligands. Deletion of ADAM17 from LCs leads to photosensitivity, and UVR induces LC ADAM17 activation and generation of soluble active EGFR ligands, suggesting that LCs protect by providing activated EGFR ligands to keratinocytes. Photosensitive systemic lupus erythematosus (SLE) models and human SLE skin show reduced epidermal EGFR phosphorylation and LC defects, and a topical EGFR ligand reduces photosensitivity. Together, our data establish a direct tissue-protective function for LCs, reveal a mechanistic basis for photosensitivity, and suggest EGFR stimulation as a treatment for photosensitivity in lupus erythematosus and potentially other autoimmune and dermatologic conditions.

BRAF V600E and Pten deletion in mice produces a histiocytic disorder with features of Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is characterized by the accumulation of Langerin (CD207)-expressing histiocytes. Mutational activation of mitogen-activated protein kinase pathway genes, in particular BRAF, drives most cases. To test whether activated BRAF is sufficient for the development of LCH, we engineered mice to express BRAF V600E under the control of the human Langerin promoter. These mice have shortened survivals, smaller lymphoid organs, absent Leydig cells, and fewer epidermal LCs than controls, but do not accumulate histiocytes. To test whether the absence of histiocyte proliferation could be due to oncogene-induced senescence, we engineered homozygous Pten loss in the same cells that expressed BRAF V600E. Like mice with intact Pten, these mice have shortened survivals, smaller thymi, and absent Leydig cells. However, loss of Pten also leads to the accumulation of CD207⁺ histiocytes in spleen, thymus, and some lymph nodes. While many CD207⁺ histiocytes in the thymus are CD8^-, reminiscent of LCH cells, the CD207⁺ histiocytes in the spleen and lymph nodes are CD8⁺. These mice also accumulate large numbers of CD207^- cells in the lamina propria (LP) of the small intestine. Both the lymphoid and LP phenotypes are likely due to human Langerin promoter-driven BRAF V600E expression in resident CD8⁺ dendritic cells in the former and LP dendritic cells in the latter and confirm that Pten loss is required to overcome inhibitory pathways induced by BRAF V600E expression. The complex phenotype of these mice is a consequence of the multiple murine cell types in which the human Langerin promoter is active.

Kappa Opioid Receptor Distribution and Function in Primary Afferents

Primary afferents are known to be inhibited by kappa opioid receptor (KOR) signaling. However, the specific types of somatosensory neurons that express KOR remain unclear. Here, using a newly developed KOR-cre knockin allele, viral tracing, single-cell RT-PCR, and ex vivo recordings, we show that KOR is expressed in several populations of primary afferents: a subset of peptidergic sensory neurons, as well as low-threshold mechanoreceptors that form lanceolate or circumferential endings around hair follicles. We find that KOR acts centrally to inhibit excitatory neurotransmission from KOR-cre afferents in laminae I and III, and this effect is likely due to KOR-mediated inhibition of Ca²⁺ influx, which we observed in sensory neurons from both mouse and human. In the periphery, KOR signaling inhibits neurogenic inflammation and nociceptor sensitization by inflammatory mediators. Finally, peripherally restricted KOR agonists selectively reduce pain and itch behaviors, as well as mechanical hypersensitivity associated with a surgical incision. These experiments provide a rationale for the use of peripherally restricted KOR agonists for therapeutic treatment.

Joint American Academy of Dermatology-National Psoriasis Foundation guidelines of care for the management and treatment of psoriasis with phototherapy

Psoriasis is a chronic inflammatory disease involving multiple organ systems and affecting approximately 3.2% of the world's population. In this section of the guidelines of care for psoriasis, we will focus the discussion on ultraviolet (UV) light-based therapies, which include narrowband and broadband UVB, UVA in conjunction with photosensitizing agents, targeted UVB treatments such as with an excimer laser, and several other modalities and variations of these core phototherapies, including newer applications of pulsed dye lasers, intense pulse light, and light-emitting electrodes. We will provide an in-depth, evidence-based discussion of efficacy and safety for each treatment modality and provide recommendations and guidance for the use of these therapies alone or in conjunction with other topical and/or systemic psoriasis treatments.

Cutaneous TRPV1+ Neurons Trigger Protective Innate Type 17 Anticipatory Immunity

Cutaneous TRPV1⁺ neurons directly sense noxious stimuli, inflammatory cytokines, and pathogen-associated molecules and are required for innate immunity against some skin pathogens. Important unanswered questions are whether TRPV1⁺ neuron activation in isolation is sufficient to initiate innate immune responses and what is the biological function for TRPV1⁺ neuron-initiated immune responses. We used TRPV1-Ai32 optogenetic mice and cutaneous light stimulation to activate cutaneous neurons in the absence of tissue damage or pathogen-associated products. We found that TRPV1⁺ neuron activation was sufficient to elicit a local type 17 immune response that augmented host defense to C. albicans and S. aureus. Moreover, local neuron activation elicited type 17 responses and augmented host defense at adjacent, unstimulated skin through a nerve reflex arc. These data show the sufficiency of TRPV1⁺ neuron activation for host defense and demonstrate the existence of functional anticipatory innate immunity at sites adjacent to infection that depends on antidromic neuron activation.

Keratinocyte-derived TGFβ is not required to maintain skin immune homeostasis

BACKGROUND

Transforming growth factor beta 1 (TGFβ) is known to be a regulator of autoimmunity. Loss of TGFβ leads to severe multi-organ autoimmunity in mice. In skin, role of TGFβ in suppressing autoimmunity is unclear.

OBJECTIVE

Determine whether Keratinocyte (KC)-derived TGFβ is required for skin immune homeostasis.

METHODS

We generated K14-CreER^T2TGFβ1^fl/fl (TGFβ^ΔKC) mice allowing for tamoxifen-induced deletion of TGFβ1 in KC. The phenotype of skin was analyzed and compared to mice in which epidermal activation of TGFβ is impaired.

RESULTS

KC was the major source of TGFβ in epidermis. Topical tamoxifen application led to efficient TGFβ1 deletion. The expected acanthosis was observed but no inflammatory infiltrate or altered numbers of resident immune cells were evident. Similarly, Itgb6^-/-x K14Cre Itgb8^f/f (Itgb6^-/-Itgb8^ΔKC) mice lacking both epidermal TGFβ-activating integrins showed no evidence of cutaneous inflammation.

CONCLUSIONS

KC-derived TGFβ and epidermal TGFβ activation are not required to suppress skin autoimmunity in steady state.

Keratinocyte-derived TGF-β is dispensable in skin autoimmunity in mice

Transforming growth factor beta 1 (TGF-β) required to suppress spontaneous autoimmunity as global deletion of TGF-β resulted in severe multi-organ autoimmunity in mice. Some TGF-β dificient mice showed skin phenotype. However, the effect of TGF-β on the autoimmunity in skin is not clear. In the epidermis of the skin, keratinocytes(KCs) are the major source of TGF-β. To test whether KCs are an obligate source of TGF-β, we generated K14-Cre-ERT2 TGF-βfl/fl mice. Topical application of tamoxifen could result in efficient deletion of TGF-β. We noted increase epidermal thickness but failed to observe evidence of cutaneous inflammation as measured by histology and flow cytometry. Notably, numbers of regulatory T cells were unaffected by the absence of KC-derived TGF-β. Since αvβ6- and αvβ8-integrins (Itgb6 and Itgb8) are principal source of activation of TGF-β in skin and then we generated Itgb6−/− Itgb8ΔKC. Similarly, we did not observe the development of spontaneous inflammation in Itgb6−/− Itgb8ΔKC mice which lack KC-derived TGFβ-activating integrins in the epidermis. From these data we concluded that KC-derived TGF-β and epidermal activation of TGF-β are not required to suppress spontaneous inflammation.

Isolation of Murine Skin Resident and Migratory Dendritic Cells via Enzymatic Digestion

Dendritic cells (DCs) are a highly specialized subset of professional antigen-presenting cells (APCs) that reside in peripheral and lymphoid tissues. DCs capture antigen in the periphery and migrate to the lymph node where they prime naïve T cells. In addition, DCs have been recently appreciated to have function in innate immunity within tissues. In the skin, heterogeneous populations of DCs reside within the epidermis and the dermis. Analysis of the cutaneous DC subsets is complicated by requirements of distinct enzymatic digestion protocols for isolation of APCs from distinct anatomical compartments of the skin. Here, specific approaches for isolation of DCs from the epidermis, dermis, and the skin-draining lymph nodes of mice are described. © 2018 by John Wiley & Sons, Inc.

Keratinocyte-Mediated Activation of the Cytokine TGF-β Maintains Skin Recirculating Memory CD8+ T Cells

Regulated activation of the cytokine TGF-β by integrins α_vβ₆ and α_vβ₈ expressed on keratinocytes is required for residence of epidermal-resident memory T cells, but whether skin-derived signals also affect recirculating memory cells in the skin remains unclear. Here, we show that after resolution of skin vaccinia virus (VV) infection, antigen-specific circulating memory CD8⁺ T cells migrated into skin. In mice lacking α_vβ₆ and α_vβ₈ integrins (Itgb6^-/-Itgb8^fl/fl-K14-cre), the absence of epidermal-activated TGF-β resulted in a gradual loss of E- or P-selectin-binding central and peripheral memory populations, which were rescued when skin entry was inhibited. Skin recirculating memory cells were required for optimal host defense against skin VV infection. These data demonstrate that skin migration can persist after resolution of local skin infection and that the cytokine environment within this nonlymphoid tissue shapes the differentiation state and persistence of the central and peripheral memory-T-cell pool.

Joint AAD-NPF guidelines of care for the management and treatment of psoriasis with biologics

Psoriasis is a chronic, inflammatory multisystem disease that affects up to 3.2% of the US population. This guideline addresses important clinical questions that arise in psoriasis management and care, providing recommendations based on the available evidence. The treatment of psoriasis with biologic agents will be reviewed, emphasizing treatment recommendations and the role of the dermatologist in monitoring and educating patients regarding benefits as well as associated risks.

Joint AAD-NPF guidelines of care for the management and treatment of psoriasis with awareness and attention to comorbidities

Psoriasis is a chronic, inflammatory, multisystem disease that affects up to 3.2% of the US population. This guideline addresses important clinical questions that arise in psoriasis management and care, providing recommendations on the basis of available evidence.

Cutaneous immune responses mediated by dendritic cells and mast cells

In the skin, complex cellular networks maintain barrier function and immune homeostasis. Tightly regulated multicellular cascades are required to initiate innate and adaptive immune responses. Innate immune cells, particularly DCs and mast cells, are central to these networks. Early studies evaluated the function of these cells in isolation, but recent studies clearly demonstrate that cutaneous DCs (dermal DCs and Langerhans cells) physically interact with neighboring cells and are receptive to activation signals from surrounding cells, such as mast cells. These interactions amplify immune activation. In this review, we discuss the known functions of cutaneous DC populations and mast cells and recent studies highlighting their roles within cellular networks that determine cutaneous immune responses.

Suppression of Th1 Priming by TLR2 Agonists during Cutaneous Immunization Is Mediated by Recruited CCR2+ Monocytes

Effective subunit vaccines require the incorporation of adjuvants that stimulate cells of the innate immune system to generate protective adaptive immune responses. Pattern recognition receptor agonists are a growing class of potential adjuvants that can shape the character of the immune response to subunit vaccines by directing the polarization of CD4 T cell differentiation to various functional subsets. In the current study, we applied a high-throughput in vitro screen to assess murine CD4 T cell polarization by a panel of pattern recognition receptor agonists. This identified lipopeptides with TLR2 agonist activity as exceptional Th1-polarizing adjuvants. In vivo, we demonstrated that i.v. administration of TLR2 agonists with Ag in mice replicated the findings from in vitro screening by promoting strong Th1 polarization. In contrast, TLR2 agonists inhibited priming of Th1 responses when administered cutaneously in mice. This route-specific suppression was associated with infiltrating CCR2⁺ cells in the skin-draining lymph nodes and was not uniquely dependent on any of the well characterized subsets of dendritic cells known to reside in the skin. We further demonstrated that priming of CD4 T cells to generate Th1 effectors following immunization with the Mycobacterium bovis bacillus Calmette-Guérin (BCG) strain, a lipoprotein-rich bacterium recognized by TLR2, was dependent on the immunization route, with significantly greater Th1 responses with i.v. compared with intradermal administration of BCG. A more complete understanding of route-dependent TLR2 responses may be critical for informed design of novel subunit vaccines and for improvement of BCG and other vaccines based on live-attenuated organisms.

The epithelial immune microenvironment (EIME) in atopic dermatitis and psoriasis

The skin provides both a physical barrier and an immunologic barrier to external threats. The protective machinery of the skin has evolved to provide situation-specific responses to eliminate pathogens and to provide protection against physical dangers. Dysregulation of this machinery can give rise to the initiation and propagation of inflammatory loops in the epithelial microenvironment that result in inflammatory skin diseases in susceptible people. A defective barrier and microbial dysbiosis drive an interleukin 4 (IL-4) loop that underlies atopic dermatitis, while in psoriasis, disordered keratinocyte signaling and predisposition to type 17 responses drive a pathogenic IL-17 loop. Here we discuss the pathogenesis of atopic dermatitis and psoriasis in terms of the epithelial immune microenvironment-the microbiota, keratinocytes and sensory nerves-and the resulting inflammatory loops.

Active spectroscopy measurements of the deuterium temperature, rotation, and density from the core to scrape off layer on the DIII-D tokamak (invited)

Main-ion charge exchange recombination spectroscopy (MICER) uses the neutral beam induced D _α spectrum to measure the local deuterium ion (D⁺) temperature, rotation, and density, as well as parameters related to the neutral beams, fast ions, and magnetic field. An edge MICER system consisting of 16 densely packed chords was recently installed on DIII-D, extending the MICER technique from the core to the pedestal and steep gradient region of H-mode plasmas where the D⁺ and commonly measured impurity ion properties can differ significantly. A combination of iterative collisional radiative modeling techniques and greatly accelerated spectral fitting allowed the extension of this diagnostic technique to the plasma edge where the steep gradients introduce significant diagnostic challenges. The importance of including the fast ion D _α emission in the fit to the spectrum for the edge system is investigated showing that it is typically not important except for cases which can have significant fast ion fractions near the plasma edge such as QH-mode. Example profiles from an Ohmic L-mode and a high power ITER baseline case show large differences in the toroidal rotation of the two species near the separatrix including a strong co-current D⁺ edge rotation. The measurements and analysis demonstrate the state of the art in active spectroscopy and integrated modeling for diagnosing fusion plasmas and the importance of direct main ion measurements.

Peripheral tissues reprogram CD8+ T cells for pathogenicity during graft-versus-host disease

Graft-versus-host disease (GVHD) is a life-threatening complication of allogeneic stem cell transplantation induced by the influx of donor-derived effector T cells (TE) into peripheral tissues. Current treatment strategies rely on targeting systemic T cells; however, the precise location and nature of instructions that program TE to become pathogenic and trigger injury are unknown. We therefore used weighted gene coexpression network analysis to construct an unbiased spatial map of TE differentiation during the evolution of GVHD and identified wide variation in effector programs in mice and humans according to location. Idiosyncrasy of effector programming in affected organs did not result from variation in T cell receptor repertoire or the selection of optimally activated TE. Instead, TE were reprogrammed by tissue-autonomous mechanisms in target organs for site-specific proinflammatory functions that were highly divergent from those primed in lymph nodes. In the skin, we combined the correlation-based network with a module-based differential expression analysis and showed that Langerhans cells provided in situ instructions for a Notch-dependent T cell gene cluster critical for triggering local injury. Thus, the principal determinant of TE pathogenicity in GVHD is the final destination, highlighting the need for target organ-specific approaches to block immunopathology while avoiding global immune suppression.

Langerhans Cells Prevent Autoimmunity via Expansion of Keratinocyte Antigen-Specific Regulatory T Cells

Langerhans cells (LCs) are antigen-presenting cells in the epidermis whose roles in antigen-specific immune regulation remain incompletely understood. Desmoglein 3 (Dsg3) is a keratinocyte cell-cell adhesion molecule critical for epidermal integrity and an autoantigen in the autoimmune blistering disease pemphigus. Although antibody-mediated disease mechanisms in pemphigus are extensively characterized, the T cell aspect of this autoimmune disease still remains poorly understood. Herein, we utilized a mouse model of CD4⁺ T cell-mediated autoimmunity against Dsg3 to show that acquisition of Dsg3 and subsequent presentation to T cells by LCs depended on the C-type lectin langerin. The lack of LCs led to enhanced autoimmunity with impaired Dsg3-specific regulatory T cell expansion. LCs expressed the IL-2 receptor complex and the disruption of IL-2 signaling in LCs attenuated LC-mediated regulatory T cell expansion in vitro, demonstrating that direct IL-2 signaling shapes LC function. These data establish that LCs mediate peripheral tolerance against an epidermal autoantigen and point to langerin and IL-2 signaling pathways as attractive targets for achieving tolerogenic responses particularly in autoimmune blistering diseases such as pemphigus.

•

Langerhans cells take up a keratinocyte-expressed autoantigen, desmoglein 3, via langerin.

•

Langerhans cells suppress autoimmunity by expanding regulatory T cells.

•

IL-2 receptor signaling occurs in Langerhans cells, conditioning them to mediate peripheral tolerance.

Lymphocytes are critical for combating pathogens, but they can cause autoimmune diseases when misdirected against autoantigens. While past experimental models have provided detailed mechanisms utilizing neo-antigens, immune regulation against naturally-expressed autoantigen(s) remains largely unexplored. Herein, we studied immune responses against desmoglein 3, a bona fide autoantigen in pemphigus, and demonstrated that epidermal Langerhans cells (antigen-presenting cells) take up the autoantigen from surrounding keratinocytes via a C-type lectin receptor to induce regulatory T cells, which are critical for immune suppression. IL-2 signaling in Langerhans cells was required to preferentially expand regulatory T cells, providing new insights into mechanisms that regulate autoimmunity.

Neoantigen Expression in Steady-State Langerhans Cells Induces CTL Tolerance

The skin hosts a variety of dendritic cells (DCs), which act as professional APC to control cutaneous immunity. Langerhans cells (LCs) are the only DC subset in the healthy epidermis. However, due to the complexity of the skin DC network, their relative contribution to either immune activation or immune tolerance is still not entirely understood. To specifically study the function of LCs in vivo, without altering the DC subset composition in the skin, we have generated transgenic mouse models for tamoxifen-inducible de novo expression of Ags in LCs but no other langerin⁺ DCs. Therefore, this system allows for LC-restricted Ag presentation to T cells. Presentation of nonsecreted OVA (GFPOVA) by steady-state LCs resulted in transient activation of endogenous CTL in transgenic mice. However, when these mice were challenged with OVA by gene gun immunization in the contraction phase of the primary CTL response they did not respond with a recall of CTL memory but, instead, with robust Ag-specific CTL tolerance. We found regulatory T cells (T_regs) enriched in the skin of tolerized mice, and depletion of T_regs or adoptive experiments revealed that T_regs were critically involved in CTL tolerance. By contrast, when OVA was presented by activated LCs, a recallable CTL memory response developed in transgenic mice. Thus, neoantigen presentation by epidermal LCs results in either robust CTL tolerance or CTL memory, and this decision-making depends on the activation state of the presenting LCs.

Cross-dressing and antigen transfer after DC targeting induce robust T cell response

Cutaneous dendritic cells (DC) are critical in protecting host from environmental insults as well as maintaining skin homeostasis. Using mouse models that are lack certain subset of cutaneous DC, studies have showed the distinct function of different subsets of skin DC, However, the interaction between skin DC subsets is less known. By targeting antigen to Langerhans cells (LC), we showed that endogenous CD4+ T cell response is independent of MHC II expression on LC. We also showed that LC handed over antigen to CD11b+ dDC and DN dDC. At the same time, MHC II deficient LC acquired MHC-II in the lymph node through cross-dressing. We demonstrated unexpected collaboration between cutaneous DC subsets, and provided insight on DC targeted vaccine design.

Measurement of deuterium density profiles in the H-mode steep gradient region using charge exchange recombination spectroscopy on DIII-D

Recent completion of a thirty two channel main-ion (deuterium) charge exchange recombination spectroscopy (CER) diagnostic on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] enables detailed comparisons between impurity and main-ion temperature, density, and toroidal rotation. In a H-mode DIII-D discharge, these new measurement capabilities are used to provide the deuterium density profile, demonstrate the importance of profile alignment between Thomson scattering and CER diagnostics, and aid in determining the electron temperature at the separatrix. Sixteen sightlines cover the core of the plasma and another sixteen are densely packed towards the plasma edge, providing high resolution measurements across the pedestal and steep gradient region in H-mode plasmas. Extracting useful physical quantities such as deuterium density is challenging due to multiple photoemission processes. These challenges are overcome using a detailed fitting model and by forward modeling the photoemission using the FIDASIM code, which implements a comprehensive collisional radiative model.

High resolution main-ion charge exchange spectroscopy in the DIII-D H-mode pedestal

A new high spatial resolution main-ion (deuterium) charge-exchange spectroscopy system covering the tokamak boundary region has been installed on the DIII-D tokamak. Sixteen new edge main-ion charge-exchange recombination sightlines have been combined with nineteen impurity sightlines in a tangentially viewing geometry on the DIII-D midplane with an interleaving design that achieves 8 mm inter-channel radial resolution for detailed profiles of main-ion temperature, velocity, charge-exchange emission, and neutral beam emission. At the plasma boundary, we find a strong enhancement of the main-ion toroidal velocity that exceeds the impurity velocity by a factor of two. The unique combination of experimentally measured main-ion and impurity profiles provides a powerful quasi-neutrality constraint for reconstruction of tokamak H-mode pedestals.

Improved edge charge exchange recombination spectroscopy in DIII-D

The charge exchange recombination spectroscopy diagnostic on the DIII-D tokamak has been upgraded with the addition of more high radial resolution view chords near the edge of the plasma (r/a > 0.8). The additional views are diagnosed with the same number of spectrometers by placing fiber optics side-by-side at the spectrometer entrance with a precise separation that avoids wavelength shifted crosstalk without the use of bandpass filters. The new views improve measurement of edge impurity parameters in steep gradient, H-mode plasmas with many different shapes. The number of edge view chords with 8 mm radial separation has increased from 16 to 38. New fused silica fibers have improved light throughput and clarify the observation of non-Gaussian spectra that suggest the ion distribution function can be non-Maxwellian in low collisionality plasmas.

Generation of a NK1R-CreER knockin mouse strain to study cells involved in Neurokinin 1 Receptor signaling

The Neurokinin 1 Receptor (NK1R), which binds Substance P, is expressed in discrete populations of neurons throughout the nervous system, where it has numerous roles including the modulation of pain and affective behaviors. Here, we report the generation of a NK1R-CreER knockin allele, in which CreER^T2 replaces the coding sequence of the TACR1 gene (encoding NK1R) in order to gain genetic access to these cells. We find that the NK1R-CreER allele mediates recombination in many regions of the nervous system that are important in pain and anxiety including the amygdala, hypothalamus, frontal cortex, raphe nucleus, and dorsal horn of the spinal cord. Other cell types that are labeled by this allele include amacrine cells in the retina and fibroblasts in the skin. Thus, the NK1R-CreER mouse line is a valuable new tool for conditional gene manipulation enabling the visualization and manipulation of cells that express NK1R.

CD301b+ dendritic cells suppress T follicular helper cells and antibody responses to protein antigens

Strong antibody response is considered a hallmark of a successful vaccine. While dendritic cells (DCs) are important for T follicular helper (Tfh) cell priming, how this process is regulated in vivo is unclear. We show here that the depletion of CD301b⁺ DCs specifically enhanced the development of Tfh cells, germinal center B cells and antibody responses against protein antigens. Exaggerated antibody responses in mice depleted of CD301b⁺ DCs occurred in the absence of any adjuvants, and resulting antibodies had broader specificity and higher affinity to the immunogen. CD301b⁺ DCs express high levels of PD-1 ligands, PD-L1 and PD-L2. Blocking PD-1 or PD-L1 during priming in wild-type mice partially mimicked the phenotype of CD301b⁺ DC-depleted animals, suggesting their role in Tfh suppression. Transient depletion of CD301b⁺ DC results in the generation of autoreactive IgG responses. These results revealed a novel regulatory mechanism and a key role of CD301b⁺ DCs in blocking autoantibody generation.