Skin-draining Lymph Nodes Research Articles

Monocytes give rise to Langerhans cells that preferentially migrate to lymph nodes at steady state

Current evidence suggests that ontogeny may account for the functional heterogeneity of some tissue macrophages, but not others. Here, we asked whether developmental origin drives different functions of skin Langerhans cells (LCs), an embryo-derived mononuclear phagocyte with features of both tissue macrophages and dendritic cells. Using time-course analyses, bone marrow chimeras, and fate tracing models, we found that the complete elimination of embryo-derived LCs at steady state results in their repopulation from circulating monocytes. However, monocyte-derived LCs inefficiently replenished the epidermal niche. Instead, these cells preferentially migrated to skin-draining lymph nodes. Mechanistically, we show that the enhanced migratory capability of monocyte-derived LCs is associated with higher expression of CD207/Langerin, a C-type lectin involved in the capture of skin microbes. Our data demonstrate that ontogeny plays a role in the migratory behavior of epidermal LCs.

Crosslinking of Ly6a metabolically reprograms CD8 T cells for cancer immunotherapy

T cell inhibitory mechanisms prevent autoimmune reactions, while cancer immunotherapy aims to remove these inhibitory signals. Chronic ultraviolet (UV) exposure attenuates autoimmunity through promotion of poorly understood immune-suppressive mechanisms. Here we show that mice with subcutaneous melanoma are not responsive to anti-PD1 immunotherapy following chronic UV irradiation, given prior to tumor injection, due to the suppression of T cell killing ability in skin-draining lymph nodes. Using mass cytometry and single-cell RNA-sequencing analyzes, we discover that skin-specific, UV-induced suppression of T-cells killing activity is mediated by upregulation of a Ly6ahigh T-cell subpopulation. Independently of the UV effect, Ly6ahigh T cells are induced by chronic type-1 interferon in the tumor microenvironment. Treatment with an anti-Ly6a antibody enhances the anti-tumoral cytotoxic activity of T cells and reprograms their mitochondrial metabolism via the Erk/cMyc axis. Treatment with an anti-Ly6a antibody inhibits tumor growth in mice resistant to anti-PD1 therapy. Applying our findings in humans could lead to an immunotherapy treatment for patients with resistance to existing treatments.

Fecal microbiota transplantation as a new way for OVA-induced atopic dermatitis of juvenile mice

Children all over the world suffer from atopic dermatitis (AD), a prevalent condition that impairs their health. Corticosteroids, which have long-term negative effects, are frequently used to treat AD. There has been a growing body of research on the gut microbiota’s function in AD. Nevertheless, the function and underlying mechanisms of fecal microbiota transplantation (FMT) in AD children remain to be established. Therefore, in order to assess the preventive effects of FMT treatment on AD and investigate the mechanisms, we constructed an ovalbumin (OVA)-induced juvenile mouse AD model in this investigation. This study explored the role and mechanism of FMT treatment in AD through 16S RNA sequencing, pathological histological staining, molecular biology, and Flow cytometry. Results demonstrated that the FMT treatment improved the gut microbiota’s diversity and composition, bringing it back to a level similar to that of a close donor. Following FMT treatment, OVA-specific antibodies were inhibited, immunoglobulin (Ig) E production was decreased, the quantity of mast cells and eosinophils was decreased, and specific inflammatory markers in the skin and serum were decreased. Further mechanistic studies revealed that FMT treatment induced CD103+ DCs and programmed cell death ligand 1 (PD-L1)/programmed cell death 1 (PD-1) expression in skin-draining lymph nodes and promoted Treg production to induce immune tolerance and suppress skin inflammation. Meanwhile, changes in the gut microbiota were substantially correlated with Th2 cytokines, OVA-specific antibodies, and PD-L1/PD-1. In conclusion, FMT regulates the Th1/Th2 immunological balance and the gut microbiota. It may also inhibit AD-induced allergy responses through the PD-L1/PD-1 pathway, and providing a unique idea and possibly a fresh approach to the treatment of AD.

Lymphatic vessel transit seeds cytotoxic resident memory T cells in skin draining lymph nodes.

Lymphatic transport shapes the homeostatic immune repertoire of lymph nodes (LNs). LN-resident memory T cells (TRMs) play an important role in site-specific immune memory, yet how LN TRMs form de novo after viral infection remains unclear. Here, we tracked the anatomical distribution of antiviral CD8+ T cells as they seeded skin and LN TRMs using a model of vaccinia virus-induced skin infection. LN TRMs localized to the draining LNs (dLNs) of infected skin, and their formation depended on the lymphatic egress of effector CD8+ T cells from the skin, already poised for residence. Effector CD8+ T cell transit through skin was required to populate LN TRMs in dLNs, a process reinforced by antigen encounter in skin. Furthermore, LN TRMs were protective against viral rechallenge in the absence of circulating memory T cells. These data suggest that a subset of tissue-infiltrating CD8+ T cells egress from tissues during viral clearance and establish a layer of regional protection in the dLN basin.

Oral mucosa effectively protects against peanut allergy in mice

Oral consumption of peanut products early in life reduces the incidence of peanut allergy in children. However, little is known about whether exposure via the oral mucosa alone is sufficient or whether the gastrointestinal tract must be engaged to protect against peanut allergy. We used a mouse model and examined the effects of peanut allergen administration to only the oral cavity on allergy development induced by environmental exposure. Naive BALB/c mice were administered peanut flour (PNF) sublingually, followed by epicutaneous exposure to PNF to mimic a human condition. The sublingual volume was adjusted to engage only the oral cavity and prevent it from reaching the esophagus or gastrointestinal tract. The efficacy was evaluated by examining the anaphylactic response, antibody titers, and T follicular helper cells. The mice exposed epicutaneously to PNF developed peanut allergy, as demonstrated by increased plasma levels of peanut-specific IgE and the manifestation of acute systemic anaphylaxis following intraperitoneal challenge with peanut extract. The development of peanut allergy was suppressed when mice had been given PNF sublingually before epicutaneous exposure. There were fewer T follicular helper cells in the skin-draining lymph nodes of mice that received sublingual PNF than in the mice that received PBS. Suppression of IgE production was observed with sublingual PNF at 1/10 of the intragastric PNF dose. Administration of peanut allergens only to the oral cavity effectively prevents the development of peanut allergy. The capacity of the oral mucosa to promote immunologic tolerance needs to be evaluated further to prevent food allergy.

Yinxieling decoction ameliorates psoriasis by regulating the differentiation and functions of Langerhans cells via the TGF-β1/PU.1/IL-23 signal axis.

Langerhans cells (LCs) play a critical role in skin immune responses and the development of psoriasis. Yinxieling (YXL) is a representativeChinese herbal medicine for the treatment of psoriasis in South China. It was found to improve psoriasis without obvious side effects in the clinic. Here we attempted to clarify whether and how YXL regulates the differentiation and functions of LCs in Imiquimod (IMQ)-induced psoriasis in vivo and induced LCs in vitro. The Psoriasis Area Severity Index (PASI) score was used to evaluate the efficacy of YXL for IMQ-induced psoriasis-like mice. Flow cytometry was utilized to analyze the effects of YXL, to regulate the differentiation, migration, maturation, and antigen presentation of LCs. The results show that YXL significantly alleviated skin inflammation, as reduced in PASI score and classic psoriasis characteristics in pathological sections. Although there was no effect on the proportion of total DCs in the skin-draining lymph nodes, the expression of epidermal LCs and its transcription factor PU.1 were both markedly inhibited. LCs were also prevented from migrating from epidermal to skin-draining lymph nodes and mature. In addition, the number of LCs carrying antigens in the epidermis increased, which suggested that YXL could effectively prevent LCs from presenting antigens. In vitro, YXL had a significant impact on inhibiting the differentiation of LCs. Further data showed that YXL decreased the relative expression of transforming growth factor-β (TGFβ) messenger RNA (mRNA) and interleukin-23 (IL-23) mRNAs. Thus, YXL alleviates psoriasis by regulating differentiation, migration, maturation, and antigen presentation via the TGFβ/PU.1/IL-23 signal axis.

Theacrine enhances autophagy and inhibits inflammation via regulating SIRT3/FOXO3a/Parkin pathway.

Psoriasis, a common chronic inflammatory skin condition, impacts around 2%-3% of the global population. Theacrine is recognized for its potential anti-inflammatory and antioxidant properties. However, the role of theacrine in psoriasis remains unclear. To investigate the effects of theacrine on psoriasis and explore the underlying signaling pathways. For imiquimod (IMQ)-induced Psoriasis-like mice, the psoriatic inflammation was monitored using Psoriasis Area and Severity Index (PASI). The skin damage was observed using Hematoxylin and Eosin staining. The KI67 and CD4 in skin tissues were assessed using Immunohistochemistry analysis. Western blots were performed to evaluate the expression of Keratin 1 (KRT1), KRT6, LC3, P62, Beclin1, T-bet, GATA3, RAR-related orphan receptor (ROR)-γt, Sirtuin-3 (SIRT3), Forkhead Box O3a (FOXO3a) and Parkin. Additionally, LC3B expression was analyzed using an immunofluorescent assay, while flow cytometry was performed to analyze the percentage of Th17, Th1, and Th2 positive cells in skin-draining lymph node. Theacrine improved skin condition by reducing hyperkeratosis and acanthosis, lowering PASI scores, and decreasing KI67-positive cells. Theacrine also modulated keratin expression, elevating KRT1 while reducing KRT6 levels. Theacrine enhanced autophagy indicated by an increased LC3-II/LC3-I ratio and Beclin1, while reduced P62 levels. Additionally, Theacrine reduced CD4-positive cells and suppressed Th17 and Th1 cell activation. Theacrine activated the FOXO3a/Parkin pathway by upregulating SIRT3 expression, and down-regulation of SIRT3 counteracted theacrine's effects in psoriasis-like mice. Theacrine inhibits skin damage, promotes autophagy, and mediates inflammation in IMQ-induced psoriasis mice via upregulating SIRT3 to activate FOXO3a/Parkin pathway, positioning theacrine as a candidate for psoriasis treatment.

Sphingosine 1-phosphate receptor 2 in keratinocytes plays a key role in reducing inflammation in psoriasis.

Psoriasis is an inflammatory skin condition where immune cells play a significant role. The importance of the cross-talk between keratinocytes and immune cells in the pathogenesis of psoriasis has recently been reaffirmed. Recent studies have found that several S1PR functional antagonists, other than S1PR2, are effective in improving psoriasis. This study aims to investigate the role of S1PR2 in psoriasis, that has not been investigated before. Spatial transcriptomics, RT-qPCR, and flow cytometry were used to map the immune cell landscape and its association with metabolic pathways in an imiquimod (IMQ)-induced psoriasis-like inflammation in S1pr2fl/fl K14-Cre mice that could not sense sphingosine-1-phosphate (S1P) in the epidermis through the S1PR2 receptor. Our analysis suggests that S1PR2 in keratinocytes plays a major role in psoriasis-like inflammation compared to other S1PRs. It acts as a down-regulator, inhibiting the recruitment of Th17 cells into the skin. In IMQ-induced psoriasis skin, both S1pr2-/- and S1pr2fl/fl K14-Cre mice showed higher expressions of proinflammatory cytokines such as TNF-α, IL-17A, and IL-1β together with higher expressions of MyD88/NF-κB pathway compared to the wild-type mice. Remarkably, in IMQ-treated mice, the deletion of S1pr2 in keratinocytes only resulted in a larger population of Th17 cells in skin-draining lymph nodes. Other S1PR modulators did not improve the worsening of psoriasis-like inflammation caused by S1PR2 deficiency in keratinocytes. This study reaches two main conclusions: signals from keratinocytes play a central role in creating an immune environment that promotes the development of psoriasis, and stimulating S1PR2, instead of suppressing it, represents a potential therapeutic approach for psoriasis.

IgE and anaphylaxis specific to the carbohydrate alpha-gal depend on IL-4

Alpha-gal (Galα1-3Galβ1-4GlcNAc) is a carbohydrate with the potential to elicit fatal allergic reactions to mammalian meat and drugs of mammalian origin. This type of allergy is induced by tick bites, and therapeutic options for this skin-driven food allergy are limited to the avoidance of the allergen and treatment of symptoms. Thus, a better understanding of the immune mechanisms resulting in sensitization through the skin is crucial, especially in the case of a carbohydrate allergen for which underlying immune responses are poorly understood. We aimed to establish a mouse model of alpha-gal allergy for in-depth immunologic analyses. Alpha-galactosyltransferase 1-deficient mice devoid of alpha-gal glycosylations were sensitized with the alpha-gal-carrying self-protein mouse serum albumin by repetitive intracutaneous injections in combination with the adjuvant aluminum hydroxide. The role of basophils and IL-4 in sensitization was investigated by antibody-mediated depletion. Alpha-gal-sensitized mice displayed increased levels of alpha-gal-specific IgE and IgG1 and developed systemic anaphylaxis on challenge with both alpha-gal-containing glycoproteins and glycolipids. In accordance with alpha-gal-allergic patients, we detected elevated numbers of basophils at the site of sensitization as well as increased numbers of alpha-gal-specific B cells, germinal center B cells, and B cells of IgE and IgG1 isotypes in skin-draining lymph nodes. By depleting IL-4 during sensitization, we demonstrated for the first time that sensitization and elicitation of allergy to alpha-gal and correspondingly to a carbohydrate allergen is dependent on IL-4. These findings establish IL-4 as a potential target to interfere with alpha-gal allergy elicited by tick bites.

Factor IX administration in the skin primes inhibitor formation and sensitizes hemophilia B mice to systemic factor IX administration

BackgroundFactor IX inhibitor formation is the most serious complication of replacement therapy for the bleeding disorder hemophilia B, exacerbated by severe allergic reactions occurring in up to 60% of patients with inhibitors. Low success rates of immune tolerance induction therapy in hemophilia B necessitate the search for novel immune tolerance therapies. Skin-associated lymphoid tissues have been successfully targeted in allergen-specific immunotherapy. ObjectivesWe aimed to develop a prophylactic immune tolerance protocol based on intradermal administration of FIX that would prevent inhibitor formation and/or anaphylaxis in response to replacement therapy. MethodsWe measured FIX inhibitor, anti-FIX immunoglobulin G1, and immunoglobulin E titers using the Bethesda assay and enzyme-linked immunosorbent assay after 4 weeks of twice-weekly intradermal FIX or FIX-Fc administration followed by 5 to 6 weeks of weekly systemic FIX injections in C3H/HeJ hemophilia B mice. We also measured skin antigen-presenting, follicular helper T, and germinal center B cell frequencies in skin-draining lymph nodes after a single or repeat intradermal FIX administration. ResultsIntradermal administration enhanced FIX inhibitor formation in response to systemic administration. We further found that intradermal administration alone triggers inhibitor formation, even at a low dose of 0.4 IU/kg, which is 100-fold lower than the intravenous dose of 40 IU/kg typically required to induce inhibitor development in hemophilia B mice. Also, intradermal administration triggered germinal center formation in skin-draining lymph nodes and sensitized mice to systemic administration. Factor IX–Fc fusion protein did not modulate inhibitor formation. ConclusionIntradermal FIX administration is highly immunogenic, suggesting that the skin compartment is not amenable to immune tolerance induction or therapeutic delivery of clotting factors.

Targeting ACC1 in T cells ameliorates psoriatic skin inflammation

Psoriasis is a chronic inflammatory skin disease driven by the IL-23/IL-17 axis. It results from excessive activation of effector T cells, including T helper (Th) and cytotoxic T (Tc) cells, and is associated with dysfunctional regulatory T cells (Tregs). Acetyl-CoA carboxylase 1 (ACC1), a rate-limiting enzyme of fatty acid synthesis (FAS), directs cell fate decisions between Th17 and Tregs and thus could be a promising therapeutic target for psoriasis treatment. Here, we demonstrate that targeting ACC1 in T cells by genetic ablation ameliorates skin inflammation in an experimental model of psoriasis by limiting Th17, Tc17, Th1, and Tc1 cells in skin lesions and increasing the frequency of effector Tregs in skin-draining lymph nodes (LNs).Key messagesACC1 deficiency in T cells ameliorates psoriatic skin inflammation in mice.ACC1 deficiency in T cells reduces IL-17A-producing Th17/Tc17/dysfunctional Treg populations in psoriatic lesions.ACC1 deficiency in T cells restrains IFN-γ-producing Th1/Tc1 populations in psoriatic skin lesions and skin-draining LNs.ACC1 deficiency promotes activated CD44+CD25+ Tregs and effector CD62L-CD44+ Tregs under homeostasis and psoriatic conditions.

Dendritic cell ICAM-1 strengthens synapses with CD8 T cells but is not required for their early differentiation

Lymphocyte priming in lymph nodes (LNs) was postulated to depend on the formation of stable Tcell receptor (TCR)-specific immune synapses (ISs) with antigen (Ag)-presenting dendritic cells (DCs). The high-affinity LFA-1 ligand ICAM-1 was implicated in different ISs studied invitro. We dissect the invivo roles of endogenous DC ICAM-1 in Ag-stimulated Tcell proliferation and differentiation and find that under type 1 polarizing conditions in vaccinated or vaccinia virus-infected skin-draining LNs, Ag-presenting DCs engage in ICAM-1-dependent stable conjugates with a subset of Ag-specific CD8 blasts. Nevertheless, in the absence of these conjugates, CD8 lymphocyte proliferation and differentiation into functional cytotoxic Tcells (CTLs) and skin homing effector lymphocytes takes place normally. Our results suggest that although CD8 Tcell blasts engage in tight ICAM-1-dependent DC-T ISs, firm ISs are dispensable for TCR-triggered proliferation and differentiation into productive effector lymphocytes.

CD4 T cells from mice with alopecia areata express an effector like phenotype and can transfer disease

Abstract Alopecia areata (AA) is an autoimmune disease with a 2% lifetime incidence. AA presents as hair loss and is characterized histologically by the presence of CD4 and CD8 T cells surrounding the hair bulb. Although CD4 T cells comprise a majority of the cellular infiltrate, little is known about the contribution of this population to disease pathogenesis. An emerging animal model of AA involves adoptive transfer of in vitro activated and expanded bulk skin draining lymph node (SDLN) cells from AA mice, resulting in the induction of disease in recipient mice. The objective of this study was to investigate the mechanisms by which those cells transfer disease. Expanded bulk SDLN cells overwhelmingly consisted of CD3+ T cells, including both CD8 and CD4 T cells. To address whether these T cell populations could separately induce AA, we first sorted CD8 T cells from the SDLNs of AA mice and found these cells potently induced disease in recipient mice. Surprisingly, isolated CD4 T cells from AA mice also had a robust capacity to induce disease, and they did so more efficiently than CD4 T cells from unaffected (UA) mice. High dimensional flow cytometric analysis of the SDLNs indicated that an enhanced number of CD4 T cells in AA mice exhibited an effector-like phenotype. Development of AA following transfer of expanded CD4 T cells relied on the presence of endogenous CD8 T cells and host responsiveness to IFN-γ, but, in contrast, loss of IL-17 signaling appeared to have no effect. Together, these data suggest that activated CD4 T-helper type 1 effector cells contribute to the activation of CD8 T cells and the subsequent attack of the hair follicle. Further studies are needed to further define the specific mechanisms by which CD4 T cells contribute to the development of AA. Dept of VA (I01BX004907), NIH/NIAMS (R01AR077194, K08AR069111, T32AI007485)

Generation of autoreactive CD8 T cell in a mouse model of alopecia areata

Abstract Alopecia areata (AA) is the most frequent form of an organ-specific autoimmune disease in humans mediated by NKG2D +CD8 T cells destroying hair follicles. C3H/HeJ mice naturally develop AA similar to humans, and we found it accompanies the expansion of exhausted phenotype (CD101 +Tim3 +) memory CD8 T cells not only in the skin and skin-draining lymph nodes (SDLNs), but also in the liver and lungs. Before the disease induction, we found these CD8 T cells are activated in the lungs and liver, suggesting they are pre-activated in these organs. In the skin, expanded CD8 T cells additionally upregulated CD39, PD-1, and CTLA-4, which produced less IFNg than those in the SDLN, liver and lungs when stimulated. These features suggest that autoreactive CD8 T cells in the skin are exhausted by chronic antigenic stimulation. However, they did not upregulate TOX, a hallmark of T cell exhaustion. Intriguingly, CD44 highNKG2D-expressing CD8 T cells appeared in the thymi of aged C3H/HeJ mice before disease induction. These cells express TBET and EOMES without overt expansion of PLZF-expressing T cells. Collectively these features suggest AA is mediated by autoreactive activation CD8 T cells that are not explained by previously known mechanisms. This research was supported by the National Research Foundation of Korea (NRF-2022R1A2C1007692)

Age-associated changes to lymph node architecture shape T cell responses

Abstract Aging dramatically impacts T cells, contributing to diminished and delayed responses to infection. While the development and maintenance of lymphocytes certainly undergo intrinsic changes with age, the contribution of cell-extrinsic forces, such as the aging tissue microenvironment, has been difficult to uncouple. Macroscopic changes to the lymph nodes have been well described, but the impact of aging on lymph node stromal subsets is less understood. Here, we visualized naïve T cell migration in the aged murine lymph node using live-cell 2-photon microscopy and determined that T cell motility was impaired in regions of increased fibrotic deposition. Using fluorescent reporters for Ccl19 and Cxcl12, homeostatic chemokines important for stromal:lymphocyte crosstalk, we also found that the distribution of stromal cells expressing these chemokines was altered with age, and that migrating naïve T cells were excluded from regions of chemokine expression. Flow cytometric analyses of fibroblastic reticular cells (FRCs) revealed decreased proportions of FRCs within the mesenteric lymph nodes and decreased putative FRC progenitors in the skin-draining lymph nodes. FRC progenitors at both sites had reduced surface expression of lymphotoxin-beta receptor, an important receptor for FRC differentiation and maintenance. We hypothesize that age-associated changes to FRC maturation contribute to increased lymph node fibrosis and altered localization of homeostatic factors. Current studies have indicated that in vitro cultured lymph node fibroblasts are sensitive to TNF-alpha and respond by increasing expression of alpha-smooth muscle actin, suggesting a mechanism by which aging remodels the lymph node microenvironment.

A new slow-releasing formulation of butyrate prolongs allograft survival

Abstract The microbiota consists of diverse microbes producing metabolites that can influence the immune system locally as well as systemically. These bioactive metabolites (postbiotics) have therapeutic potential and may prove useful to facilitate graft acceptance. Short-chain fatty acids (SCFA) promote intestinal homeostasis and have been linked to health and disease. The Hubbell-Nagler laboratories at the University of Chicago have developed a micelle-based platform that can deliver the SCFA butyrate systemically, with long-term retention and induction of tolerogenic responses. We hypothesized that the administration of this butyrate formulation will improve graft survival by suppressing the alloimmune response. Our preliminary data showed that only oral delivery of the butyrate formulation prolonged survival of a C57Bl/6 male to female minor-mismatched skin graft significantly, whereas sub-cutaneous and intra-peritoneal administration were ineffective. Improved graft survival was associated with diminished production of TNFα by splenic and skin-draining lymph node myeloid cells upon LPS stimulation, suggesting that butyrate modulates the myeloid compartment to reduce levels of pro-inflammatory cytokines. The postbiotic also enhanced survival of a BALB/c to C57Bl/6 major-mismatched skin graft, without the use of immunosuppressive drugs, and resulted in lower levels of donor-specific alloantibodies. Prolonging the administration of butyrate post-transplantation ameliorated graft survival even further, confirming the micelle-based platform has therapeutic potential. Current efforts focus on determining if the butyrate formulation drives myeloid cell polarization toward an anti-inflammatory phenotype. This project was supported by grant NIH/NIAID 2R01AI115716

Foxp3 exon 2 regulates keratinocyte-specific IgE and basophil extracellular traps in cutaneous autoimmune photosensitivity.

Abstract Ultraviolet B (UVB) light is a common environmental trigger that can induce flares in several autoimmune diseases, but the mechanisms that mediate UVB-induced photosensitivity remain poorly understood. We used mice which express an autoimmune-driving isoform of Foxp3, called FoxP3 ΔE2mice, to develop a model autoimmune cutaneous photosensitivity. In the steady-state, FoxP3 ΔE2mice have high serum titers of IgE that target skin-associated autoantigens, and increased numbers of IL4-producing T follicular helper cells that target skin-associated proteins (Keratin 14) in the absence of overt immune challenge. After skin exposure to UVB light, FoxP3 ΔE2mice had further elevated IgE, worsened skin inflammation, and increased IgE complex deposition that localized to the challenge site. IgE production in UVB-challenged mice correlated with increased frequencies of germinal center (GC) B cells, elevated percentages of IL-4 +T follicular helper cells, and numbers of basophils with high surface expression of IgE in the draining lymph nodes of UVB-challenged skin. We also observed a significant increase in IgE accumulation, increased numbers of Tug8 +basophil extracellular traps in UVB-challenged skin and increased frequencies of activated plasmacytoid dendritic cells (CD80 +CD86 +) in the skin and skin-draining lymph nodes of FoxP3 ΔE2mice when compared to wild-type littermates. Collectively, we found that T follicular regulatory cells in FoxP3 ΔE2mice fail to maintain self-tolerance in the GC, resulting in increased production of skin reactive IgE and worsened skin inflammation driven by basophil extracellular trap accumulation in UVB-damaged skin. Supported by grants from the NIH (F32 AI154787, R01 AI136475, R21 AI169418, and R21 AI152444)

Abstract LB334: Assessment of the potential of graphene oxide as an antigen delivery platform for cancer immunotherapy

Abstract Introduction: Novel cancer immunotherapies are urgently needed due to a lack of definitive treatments, as well as toxicity and cost of current therapies. 2-dimensional carbon graphene oxide (GO) nanomaterials provide a large surface area, high protein loading efficiency and good biocompatibility, as well as being inexpensive. Given these properties, we investigated whether and how GO could be an effective antigen delivery system for targeted cancer immunotherapies. Methods: GO was non-covalently complexed with the model antigen ovalbumin peptide (OVA257-264) and the immunostimulant and toll-like receptor 3 agonist polyinosinic:polycytidylic acid (Poly (I:C)). We examined innate and adaptive immune responses after subcutaneous injection of GO complexes by histology and flow cytometry. Results: We found that GO without Poly (I:C) had a very limited immunogenic potential. In contrast, GO complexed with Poly (I:C) significantly increased immune cell recruitment to the injection site, and enhanced activation and migration of dendritic cell subsets (cDC1s and cDC2s) in skin-draining lymph nodes 24 hours after injection. Additionally, we found that GO complexed with Poly (I:C) dramatically enhanced OVA-specific CD8+ T cell expansion and cytotoxic potential in both spleen and skin-draining lymph nodes 7 days after subcutaneous complex administration to mice which had previously been injected intravenously with traceable, OVA-specific (OT-I) CD8+ T cells. Conclusion: Our results have revealed the immunomodulatory potential of GO when complexed with Poly (I:C) by attracting immune cells to the injection site and augmenting antigen-specific cytotoxic responses both locally and systemically. Ongoing work is determining the anti-tumor potential of this approach, and potential mechanisms by which GO complexes might limit tumor progression. Citation Format: Sorayut Chattrakarn, Grace Mallett, Helen Parker, Neus Lozano, Kostas Kostarelos, Andrew S. MacDonald. Assessment of the potential of graphene oxide as an antigen delivery platform for cancer immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB334.

PDC-like cells are pre-DC2 and require KLF4 to control homeostatic CD4 T cells.

Plasmacytoid dendritic cells (pDCs) have been shown to play an important role during immune responses, ranging from initial viral control through the production of type I interferons to antigen presentation. However, recent studies uncovered unexpected heterogeneity among pDCs. We identified a previously uncharacterized immune subset, referred to as pDC-like cells, that not only resembles pDCs but also shares conventional DC (cDC) features. We show that this subset is a circulating precursor distinct from common DC progenitors, with prominent cDC2 potential. Our findings from human CD2-iCre and CD300c-iCre lineage tracing mouse models suggest that a substantial fraction of cDC2s originates from pDC-like cells, which can therefore be referred to as pre-DC2. This precursor subset responds to homeostatic cytokines, such as macrophage colony stimulating factor, by expanding and differentiating into cDC2 that efficiently prime T helper 17 (TH17) cells. Development of pre-DC2 into CX3CR1+ ESAM- cDC2b but not CX3CR1- ESAM+ cDC2a requires the transcription factor KLF4. Last, we show that, under homeostatic conditions, this developmental pathway regulates the immune threshold at barrier sites by controlling the pool of TH17 cells within skin-draining lymph nodes.

IL-17 Signaling in Keratinocytes Orchestrates the Defense against Staphylococcus aureus Skin Infection

Keratinocytes (KCs) form the outer epithelial barrier of the body, protecting against invading pathogens. Mice lacking the IL-17RA or both IL-17A and IL-17F develop spontaneous Staphylococcusaureus skin infections. We found a marked expansion of T17 cells, comprised of RORγt-expressing γδ T cells and T helper 17 cells in the skin-draining lymph nodes of these mice. Contradictory to previous suggestions, this expansion was not a result of a direct negative feedback loop because we found no expansion of T17 cells in mice lacking IL-17 signaling specifically in T cells. Instead, we found that the T17 expansion depended on the microbiota and was observed only when KCs were deficient for IL-17RA signaling. Indeed, mice that lack IL-17RA only in KCs showed an increased susceptibility to experimental epicutaneous infection with S.aureus together with an accumulation of IL-17A-producing γδ T cells. We conclude that deficiency of IL-17RA on KCs leads to microbiota dysbiosis in the skin, which triggers the expansion of IL-17A-producing T cells. Our data show that KCs are the primary target cells of IL-17A and IL-17F, coordinating the defense against microbial invaders in the skin.