Subsets Of Antigen-presenting Cells Research Articles

Acquired immunostimulatory phenotype of migratory CD103+ DCs promotes alloimmunity following corneal transplantation.

After transplantation, Th1-mediated immune rejection is the predominant cause of graft failure. Th1 cell sensitization occurs through complex and context-dependent interaction among antigen-presenting cell subsets, particularly CD11b+ DCs (DC2) and CD103+ DCs (DC1). This interaction necessitates further investigation in the context of transplant immunity. We used well-established preclinical models of corneal transplantation and identified distinct roles of migratory CD103+ DC1 in influencing the outcomes of the grafted tissue. In recipients with uninflamed corneal beds, migratory CD103+ DC1 demonstrate a tolerogenic phenotype that modulates the immunogenic capacity of CD11b+ DC2 primarily mediated by IL-10, suppressing alloreactive CD4+ Th1 cells via the PD-L1/PD-1 pathway and enhancing Treg-mediated tolerance via αvβ8 integrin-activated TGF-β1, thus facilitating graft survival. Conversely, in recipients with inflamed and vascularized corneal beds, IFN-γ produced by CD4+ Th1 cells induced migratory CD103+ DC1 to adopt an immunostimulatory phenotype, characterized by the downregulation of regulatory markers, including αvβ8 integrin and IL-10, and the upregulation of IL-12 and costimulatory molecules CD80/86, resulting in graft failure. The adoptive transfer of ex vivo induced tolerogenic CD103+ DC1 (iDC1) effectively inhibited Th1 polarization and preserved the tolerogenic phenotype of their physiological counterparts. Collectively, our findings underscore the essential role played by CD103+ DC1 in modulating host alloimmune responses.

MrgprA3 neurons drive cutaneous immunity against helminths through selective control of myeloid-derived IL-33.

Skin uses interdependent cellular networks for barrier integrity and host immunity, but most underlying mechanisms remain obscure. Herein, we demonstrate that the human parasitic helminth Schistosoma mansoni inhibited pruritus evoked by itch-sensing afferents bearing the Mas-related G-protein-coupled receptor A3 (MrgprA3) in mice. MrgprA3 neurons controlled interleukin (IL)-17+ γδ T cell expansion, epidermal hyperplasia and host resistance against S. mansoni through shaping cytokine expression in cutaneous antigen-presenting cells. MrgprA3 neuron activation downregulated IL-33 but induced IL-1β and tumor necrosis factor in macrophages and type 2 conventional dendritic cells partially through the neuropeptide calcitonin gene-related peptide. Macrophages exposed to MrgprA3-derived secretions or bearing cell-intrinsic IL-33 deletion showed increased chromatin accessibility at multiple inflammatory cytokine loci, promoting IL-17/IL-23-dependent changes to the epidermis and anti-helminth resistance. This study reveals a previously unrecognized intercellular communication mechanism wherein itch-inducing MrgprA3 neurons initiate host immunity against skin-invasive parasites by directing cytokine expression patterns in myeloid antigen-presenting cell subsets.

CD91 and its ligand gp96 confer cross-priming capabilities to multiple APCs during immune responses to nascent, emerging tumors.

During cancer immunosurveillance, dendritic cells (DCs) play a central role in orchestrating T-cell responses against emerging tumors. Capture of miniscule amounts of antigen along with tumor-initiated costimulatory signals can drive maturation of DCs. Expression of CD91 on DCs is essential in cross-priming of T-cell responses in the context of nascent tumors. Multiple DC and macrophage subsets express CD91 and engage tumor-derived gp96 to initiate antitumor immune responses, yet the specific CD91+ antigen-presenting cells (APCs) that are required for T-cell cross-priming during cancer immunosurveillance are unknown. In this study, we determined that CD91 expression on type 1 conventional DCs (cDC1) is necessary for cancer immunosurveillance. Specifically, CD91-expressing cDC1 were found to capture the CD91 ligand gp96 from tumors and, upon migration to the lymph nodes, distribute gp96 among lymph-node resident APCs. However, cDC1 that captured tumor-derived gp96 only provided early tumor control, while sustained and long-term tumor rejection was bestowed to the host by other gp96+ cross-priming DCs. We further found that the CD91-induced transcriptome in APCs promoted cross-priming of T-cell responses while downregulating immune regulatory pathways. Our results show an elaborate and synchronized division of labor of APCs in the successful elimination of cancer cells via CD91. We predict that the specialized functions of APC subsets can be harnessed for immunotherapy of disease.

Increased IFN-β indicates better survival in hepatocellular carcinoma treated with radiotherapy.

Preclinical data suggest that type I interferon (IFN) responsiveness is essential for the antitumor effects of radiotherapy (RT). However, its clinical value remains unclear. This study aimed to explore this from a clinical perspective. In cohort 1, data from 152 hepatocellular carcinoma (HCC) patients who received RT were analyzed. Blood samples were taken 1 day before and 2 weeks after RT. RT was found to increase serum levels of IFN-β (a subtype of IFN-I) in HCC patients (3.42 ± 1.57 to 5.51 ± 2.11 pg/ml, P < 0.01), particularly in those with favorable responses. Higher post-RT serum IFN-β levels (≥4.77 pg/ml) were associated with better progression-free survival (HR = 0.58, P < 0.01). Cohort 2 included 46 HCC patients, including 23 who underwent preoperative RT and 23 matched control HCC who received surgical resection without RT. Formalin-fixed paraffin-embedded samples were obtained. Neoadjuvant RT significantly increased IFN-β expression in tumor tissues compared to direct surgery (8.13% ± 5.19% to 15.10% ± 5.89%, P < 0.01). Higher post-RT IFN-β (>median) indicated better disease-free survival (P = 0.049). Additionally, increased CD11c+MHCII+CD141+ antigen-presenting cell subsets and CD103+CD39+CD8+ tumor-infiltrating lymphocytes were found in the higher IFN-β group (P = 0.02, P = 0.03), which may contribute to the favorable prognosis in higher IFN-β group. Collectively, these findings suggest that IFN-β response activated by radiation may serve as a prognostic biomarker for HCC patients undergoing RT.

Relation of Langerhans cell size to buccal carcinoma

ABSTRACT Oral cancer decreases quality of life despite timely medical management. The carcinogens in tobacco products and their role in tumorigenesis are well documented. Langerhans cells (LCs) are a subset of antigen-presenting cells (APCs) that monitor the tumor microenvironment and engulf carcinogens and foreign bodies. We investigated the distribution and size of LCs and their relation to the mode of tobacco consumption and clinical outcome in patients with buccal carcinoma. We recruited patients with oral cancer who were scheduled for tumor excision and men with urethral stricture undergoing substitution urethroplasty using buccal mucosa. Normal and tumor-adjacent tissues were stained with CD1a antibody. The distribution and mean diameter of 100 LCs/patient were determined. We found significantly smaller LCs in patients who chewed only tobacco compared to those who consumed tobacco by other means. The size of LCs decreased significantly with progressive stages of malignant disease. We found that patients with larger LCs survived longer than those with smaller LCs during an average follow-up of 24 months. We suggest a relation between the size of LCs and clinical outcomes in patients with buccal carcinoma.

Dendritic Cells: Multifunctional Roles in Host Defenses to Cryptococcus Infections.

Fungal infections are an increasingly growing public health concern, and Cryptococcus is one of the most problematic fungal organisms causing substantial mortality and morbidity worldwide. Clinically, this high incidence of cryptococcosis is most commonly seen in immunocompromised patients, especially those who lack an adaptive T cell response, such as HIV/AIDS patients. However, patients with other underlying immunodeficiencies are also at an increased risk for cryptococcosis. The adaptive immune response, in particular the Th1/Th17 T-cell-mediated responses, to pulmonary Cryptococcus infections are required for host protection. Dendritic cells (DCs), encompassing multiple subsets identified to date, are recognized as the major professional antigen-presenting cell (APC) subset essential for the initiation and execution of T-cell immunity. Apart from their prominent role in orchestration of the adaptive arm of the immune defenses, DCs are fully armed cells from the innate immune system capable of the recognition, uptake, and killing of the fungal cells. Thus, DCs serve as a critical point for the endpoint outcomes of either fungal control or unrestrained fungal infection. Multiple studies have shown that DCs are required for anti-cryptococcal defense in the lungs. In addition, the role of DCs in Cryptococcus gattii infections is just starting to be elucidated. C. gattii has recently risen to prominence with multiple outbreaks in the US and Canada, demonstrating increased virulence in non-immunocompromised individuals. C. gattii infection fails to generate an inflammatory immune response or a protective Th1/Th17 T cell response, at least in part, through a lack of proper DC function. Here we summarize the multiple roles of DCs, including subsets of DCs in both mouse and human models, the roles of DCs during cryptococcal infection, and mechanisms by cryptococcal cells to attempt to undermine these host defenses.

Cytotoxicity as a form of immunogenic cell death leading to efficient tumor antigen cross-priming.

Antigen cross-priming of CD8+ T cells is a critical process necessary for the effective expansion and activation of CD8+ T cells endowed with the ability to recognize and destroy tumor cells. The cross-presentation of tumor antigens to cross-prime CD8+ T cells is mainly mediated, if not only, by a subset of professional antigen-presenting cells termed type-1 conventional dendritic cells (cDC1). The demise of malignant cells can be immunogenic if it occurs in the context of premortem stress. These ways of dying are termed immunogenic cell death (ICD) and are associated with biochemical features favoring cDC1 for the efficient cross-priming of tumor antigens. Immunosurveillance and the success of immunotherapies heavily rely on the ability of cytotoxic immune cells, primarily CD8+ T cells and NK cells, to detect and eliminate tumor cells through mechanisms collectively known as cytotoxicity. Recent studies have revealed the significance of NK- and CTL-mediated cytotoxicity as a prominent form of immunogenic cell death, resulting in mechanisms that promote and sustain antigen-specific immune responses. This review focuses on the mechanisms underlying the cross-presentation of antigens released during tumor cell killing by cytotoxic immune cells, with an emphasis on the role of cDC1 cells. Indeed, cDC1s are instrumental in the effectiveness of most immunotherapies, underscoring the significance of tumor antigen cross-priming in contexts of immunogenic cell death. The notion of the potent immunogenicity of cell death resulting from NK or cytotoxic T lymphocyte (CTL)-mediated cytotoxicity has far-reaching implications for cancer immunotherapy.

CCR4 and CCR7 differentially regulate thymocyte localization with distinct outcomes for central tolerance.

Central tolerance ensures autoreactive T cells are eliminated or diverted to the regulatory T cell lineage, thus preventing autoimmunity. To undergo central tolerance, thymocytes must enter the medulla to test their T-cell receptors (TCRs) for autoreactivity against the diverse self-antigens displayed by antigen-presenting cells (APCs). While CCR7 is known to promote thymocyte medullary entry and negative selection, our previous studies implicate CCR4 in these processes, raising the question of whether CCR4 and CCR7 play distinct or redundant roles in central tolerance. Here, synchronized positive selection assays, two-photon time-lapse microscopy, and quantification of TCR-signaled apoptotic thymocytes, demonstrate that CCR4 and CCR7 promote medullary accumulation and central tolerance of distinct post-positive selection thymocyte subsets in mice. CCR4 is upregulated within hours of positive selection signaling and promotes medullary entry and clonal deletion of immature post-positive selection thymocytes. In contrast, CCR7 is expressed several days later and is required for medullary localization and negative selection of mature thymocytes. In addition, CCR4 and CCR7 differentially enforce self-tolerance, with CCR4 enforcing tolerance to self-antigens presented by activated APCs, which express CCR4 ligands. Our findings show that CCR7 expression is not synonymous with medullary localization and support a revised model of central tolerance in which CCR4 and CCR7 promote early and late stages of negative selection, respectively, via interactions with distinct APC subsets.

CCR4 and CCR7 differentially regulate thymocyte localization with distinct outcomes for central tolerance

Abstract Central tolerance ensures autoreactive thymocytes are either eliminated via clonal deletion or are diverted to the regulatory T-cell lineage, thus minimizing T cell autoimmunity. To undergo central tolerance, thymocytes must enter the medulla to test their TCRs for autoreactivity against the diverse self-antigens displayed by medullary antigen presenting cells (APCs). While CCR7 is known to promote thymocyte medullary entry and negative selection against some self-antigens, our previous studies implicate CCR4 in these processes, raising the question of whether CCR4 and CCR7 play distinct or redundant roles in central tolerance. Here, we use synchronized positive selection assays and 2-photon timelapse microscopy to demonstrate that CCR4 and CCR7 are expressed sequentially after positive selection and promote medullary accumulation and central tolerance of distinct post-positive selection thymocyte subsets. CCR4 is upregulated within hours of positive selection signaling and promotes medullary entry and clonal deletion of immature post-positive selection thymocytes. In contrast, CCR7 is expressed several days later and promotes medullary entry and negative selection of mature thymocytes. Unlike CCR7 ligands, which are expressed by medullary thymic epithelial cells, CCR4 ligands are expressed by hematopoietic APCs, and we find that CCR4 enforces thymocyte tolerance to self-antigens presented by activated thymic APCs. Our findings demonstrate that CCR7 expression is neither necessary nor sufficient for thymocyte medullary entry and support a revised model of central tolerance in which CCR4 and CCR7 promote early and late stages of central tolerance, respectively, via interactions with distinct APC subsets. Supported by a grant from the NIH/NIAID (R01AI104870)

Deciphering immunological mechanisms underlying the efficacy of nanoparticle-based vaccines against opioid use disorder (OUD)

Abstract The highly complex OUD and overdose epidemic poses a huge public health and economic burden, urging the need for safe and more effective therapeutic options. Vaccines offer a promising strategy for OUD treatment and prevention of overdose. Vaccinating against opioids generates drug-specific polyclonal antibodies (Ab) that selectively bind targeted opioids, blocking their distribution to the brain and thus blunting opioid induced rewards, pharmacological and side effects. Previous clinical trials of addiction vaccines showed proof of efficacy only in subjects with the highest Ab titers, highlighting the need to design more effective vaccines. The generation of a robust anti-drug polyclonal Abs response relies on CD4+ T cell-dependent B cell activation, hence dendritic cells (DC) are crucial for initiating CD4+ T cells priming and B cell responses. To improve vaccine formulation, we are exploiting a lipid-polymer hybrid nanoparticle (LPNP) platform and toll-like receptor (TLR) agonists to potentiate antigen recognition by antigen presenting cells (APCs) and subsequently the efficacy of anti-opioid conjugate vaccines. Using a flow cytometry-based in vitro activation assay, we demonstrated that LPNP-based vaccines are more effective in inducing macrophages activation marker (iNOS) and DCs co-stimulatory molecules and maturation markers (CD86, CD40, and MHC II) compared to conventional vaccines. Adding selected TLR agonists further improved nanovaccine efficacy in inducing the maturation and activation of APCs. These findings were confirmed with RT-qPCR quantifying mRNA expression of above-mentioned markers. These studies will identify key APCs subsets contributing to vaccine efficacy against OUD and other targets. Supported by grants from NIH (UG3/UH3 DA048775)

Long-term tolerance to skin commensals is established neonatally through a specialized dendritic cell subgroup

Early-life establishment of tolerance to commensal bacteria at barrier surfaces carries enduring implications for immune health but remains poorly understood. Here, we showed that tolerance in skin was controlled by microbial interaction with a specialized subset of antigen-presenting cells. More particularly, CD301b+ type 2 conventional dendritic cells (DCs) in neonatal skin were specifically capable of uptake and presentation of commensal antigens for the generation of regulatory T (Treg) cells. CD301b+ DC2 were enriched for phagocytosis and maturation programs, while also expressing tolerogenic markers. In both human and murine skin, these signatures were reinforced by microbial uptake. In contrast to their adult counterparts or other early-life DC subsets, neonatal CD301b+ DC2 highly expressed the retinoic-acid-producing enzyme, RALDH2, the deletion of which limited commensal-specific Treg cell generation. Thus, synergistic interactions between bacteria and a specialized DC subset critically support early-life tolerance at the cutaneous interface.

A Multiparameter Prognostic Risk Score of Chronic Graft-versus-Host Disease Based on CXCL10 and Plasmacytoid Dendritic Cell Levels in the Peripheral Blood at 3 Months after Allogeneic Hematopoietic Stem Cell Transplantation

Chronic GVHD (cGVHD) is the major cause of long-term morbidity after allogeneic hematopoietic stem cell transplantation (HSCT). There are no biomarkers that can consistently predict its occurrence. We aimed to evaluate whether numbers of antigen-presenting cell subsets in peripheral blood (PB) or serum chemokine concentrations are biomarkers of cGVHD occurrence. The study cohort comprised 101 consecutive patients undergoing allogeneic HSCT between January 2007 and 2011. cGVHD was diagnosed by both modified Seattle criteria and National Institutes of Health (NIH) criteria. Multicolor flow cytometry was used to determine the number of PB myeloid dendritic cells (DCs), plasmacytoid DCs, CD16+ DCs, and CD16+ and CD16- monocytes, as well as CD4+ and CD8+ T cells, CD56+ natural killer cells, and CD19+ B cells. Serum concentrations of CXCL8, CXCL10, CCL2, CCL3, CCL4, and CCL5 were measured by a cytometry bead array assay. At a median of 60 days after enrollment, 37 patients had developed cGVHD. Patients with cGVHD and those without cGVHD had comparable clinical characteristics. However, previous acute GVHD (aGVHD) was strongly correlated with later cGVHD (57% versus 24%, respectively; P=.0024). Each potential biomarker was screened for its association with cGVHD using the Mann-Whitney U test. Biomarkers that differed significantly (P < .05) between patients with cGVHD and those without cGVHD were analyzed by receiver operating characteristic (ROC) curve analysis to select the variables predicting cGVHD with an area under the ROC curve (AUC) >.5 and a P value <.05. A multivariate Fine-Gray model identified the following variables as independently associated with the risk of cGVHD: CXCL10 ≥592.650 pg/mL (hazard ratio [HR], 2.655; 95% confidence interval [CI], 1.298 to 5.433; P=.008), pDC ≥2.448/μL (HR, .286; 95% CI, .142 to .577; P < .001) and previous aGVHD (HR, 2.635; 95% CI, 1.298 to 5.347; P=.007). A risk score was derived based on the weighted coefficients of each variable (2 points each), resulting in the identification of 4 cohorts of patients (scores of 0, 2, 4, and 6). In a competing risk analysis to stratify patients at differing risk levels of cGVHD, the cumulative incidence of cGVHD was 9.7%, 34.3%, 57.7%, and 100% in patients with scores of 0, 2, 4, and 6, respectively (P < .0001). The score could nicely stratify the patients based on the risk of extensive cGVHD as well as NIH-based global and moderate to severe cGVHD. Based on ROC analysis, the score could predict the occurrence of cGVHD with an AUC of .791 (95% CI, .703 to .880; P < .001). Finally, a cutoff score ≥4 was identified as the optimal cutoff by Youden J index with a sensitivity of 57.1% and a specificity of 85.0%. A multiparameter score including a history of previous aGVHD, serum CXCL10 concentration, and number of pDCs in the PB at 3 months post-HSCT stratify patients at varying risk levels of cGVHD. However, the score needs to be validated in a much larger independent and possibly multicenter cohort of patients undergoing transplantation from different donor types and with distinct GVHD prophylaxis regimens.

Differential expression of nuclear hormone receptors by dendritic cell subsets in human vaginal mucosa and skin.

Nuclear hormone receptors (NHRs) expressed by dendritic cells (DCs), the major immune inducers and regulators, could play important roles in host immunity. Assessment of NHRs expressed by DCs in the vaginal mucosa (VM), in comparison with those expressed by DCs in other tissues, will thus help us understand the immunology of human vagina. This study identified 16 NHR transcripts that are differentially expressed among 8 different antigen-presenting cell (APC) subsets isolated from human VM, skin, and blood. The expression profiles of NHRs were largely tissue specific. VM APCs expressed increased levels of LXRA, RXRA, ESRRA, ESRRAP2, and PPARG, whereas skin and blood APCs expressed increased levels of NURR1, NOR1 and RARA. Of interest, female sex hormone receptors, ESR1 and PGR, were found to be mainly expressed by non-APC cell types in the VM; ESR1 by HLA-DR+CD34+ and PGR by HLA-DR- cells. ERα and PR were expressed by vimentin+ cells in the VM, but not in human skin. ERα, but not PR, was also expressed in CD10+ cells in the lamina propria of VM. In conclusion, NHR expression by APC subsets is tissue- and cell type-specific. Future studies on the roles of individual NHRs expressed by different cell types, including DC subsets, in the human VM are warranted.

Conventional dendritic cells type 1 are strongly enriched, quiescent and relatively tolerogenic in local inflammatory arthritis.

Dendritic cells (DC) are crucial for initiating and shaping immune responses. So far, little is known about the functional specialization of human DC subsets in (local) inflammatory conditions. We profiled conventional (c)DC1, cDC2 and monocytes based on phenotype, transcriptome and function from a local inflammatory site, namely synovial fluid (SF) from patients suffering from a chronic inflammatory condition, Juvenile Idiopathic Arthritis (JIA) as well as patients with rheumatoid arthritis (RA). Paired PB and SF samples from 32 JIA and 4 RA patients were collected for mononuclear cell isolation. Flow cytometry was done for definition of antigen presenting cell (APC) subsets. Cell sorting was done on the FACSAria II or III. RNA sequencing was done on SF APC subsets. Proliferation assays were done on co-cultures after CD3 magnetic activated cell sorting (MACS). APC Toll-like receptor (TLR) stimulation was done using Pam3CSK4, Poly(I:C), LPS, CpG-A and R848. Cytokine production was measured by Luminex. cDC1, a relatively small DC subset in blood, are strongly enriched in SF, and showed a quiescent immune signature without a clear inflammatory profile, low expression of pathogen recognition receptors (PRRs), chemokine and cytokine receptors, and poor induction of T cell proliferation and cytokine production, but selective production of IFNλ upon polyinosinic:polycytidylic acid exposure. In stark contrast, cDC2 and monocytes from the same environment, showed a pro-inflammatory transcriptional profile, high levels of (spontaneous) pro-inflammatory cytokine production, and strong induction of T cell proliferation and cytokine production, including IL-17. Although the cDC2 and monocytes showed an overlapping transcriptional core profile, there were clear differences in the transcriptional landscape and functional features, indicating that these cell types retain their lineage identity in chronic inflammatory conditions. Our findings suggest that at the site of inflammation, there is specific functional programming of human DCs, especially cDC2. In contrast, the enriched cDC1 remain relatively quiescent and seemingly unchanged under inflammatory conditions, pointing to a potentially more regulatory role.

Study and isolation of human intestinal dendritic cell and macrophage subsets.

Dendritic cells and macrophages are the main antigen-presenting cells (APC). In the gut, they control the mechanisms of tolerance toward commensals and nutrients, at the time that they maintain their capacity to trigger immune responses against invading pathogens. Nevertheless, this balance is not perfect as it can get disrupted like in inflammatory bowel disease (where they drive an abnormal immune response against the microbiota) or in coeliac disease (where they trigger an immune response against dietary gluten). Therefore, the study of human intestinal APC subsets is crucial not just to get a deeper insight in the mechanisms of human intestinal homeostasis, but also to understand the pathogenesis of inflammatory bowel disease and coeliac disease. Nevertheless, their study is quite complicated as despite their relevance, their numbers are scare in the intestinal mucosa. Therefore, we hereby describe different approaches to study human intestinal dendritic cell and macrophage subsets in the human intestinal mucosa.

The Conventional Dendritic Cell 1 Subset Primes CD8+ T Cells and Traffics Tumor Antigen to Drive Antitumor Immunity in the Brain.

The central nervous system (CNS) antigen-presenting cell (APC) that primes antitumor CD8+ T-cell responses remains undefined. Elsewhere in the body, the conventional dendritic cell 1 (cDC1) performs this role. However, steady-state brain parenchyma cDC1 are extremely rare; cDCs localize to the choroid plexus and dura. Thus, whether the cDC1 play a function in presenting antigen derived from parenchymal sources in the tumor setting remains unknown. Using preclinical glioblastoma (GBM) models and cDC1-deficient mice, we explored the presently unknown role of cDC1 in CNS antitumor immunity. We determined that, in addition to infiltrating the brain tumor parenchyma itself, cDC1 prime neoantigen-specific CD8+ T cells against brain tumors and mediate checkpoint blockade-induced survival benefit. We observed that cDC, including cDC1, isolated from the tumor, the dura, and the CNS-draining cervical lymph nodes harbored a traceable fluorescent tumor antigen. In patient samples, we observed several APC subsets (including the CD141+ cDC1 equivalent) infiltrating glioblastomas, meningiomas, and dura. In these same APC subsets, we identified a tumor-specific fluorescent metabolite of 5-aminolevulinic acid, which fluorescently labeled tumor cells during fluorescence-guided GBM resection. Together, these data elucidate the specialized behavior of cDC1 and suggest that cDC1 play a significant role in CNS antitumor immunity.

Protective interaction of human phagocytic APC subsets with Cryptococcus neoformans induces genes associated with metabolism and antigen presentation.

Cryptococcal meningitis is the most common cause of meningitis among HIV/AIDS patients in sub-Saharan Africa, and worldwide causes over 223,000 cases leading to more than 181,000 annual deaths. Usually, the fungus gets inhaled into the lungs where the initial interactions occur with pulmonary phagocytes such as dendritic cells and macrophages. Following phagocytosis, the pathogen can be killed or can replicate intracellularly. Previous studies in mice showed that different subsets of these innate immune cells can either be antifungal or permissive for intracellular fungal growth. Our studies tested phagocytic antigen-presenting cell (APC) subsets from the human lung against C. neoformans. Human bronchoalveolar lavage was processed for phagocytic APCs and incubated with C. neoformans for two hours to analyze the initial interactions and fate of the fungus, living or killed. Results showed all subsets (3 macrophage and 3 dendritic cell subsets) interacted with the fungus, and both living and killed morphologies were discernable within the subsets using imaging flow cytometry. Single cell RNA-seq identified several different clusters of cells which more closely related to interactions with C. neoformans and its protective capacity against the pathogen rather than discrete cellular subsets. Differential gene expression analyses identified several changes in the innate immune cell's transcriptome as it kills the fungus including increases of TNF-α (TNF) and the switch to using fatty acid metabolism by upregulation of the gene FABP4. Also, increases of TNF-α correlated to cryptococcal interactions and uptake. Together, these analyses implicated signaling networks that regulate expression of many different genes - both metabolic and immune - as certain clusters of cells mount a protective response and kill the pathogen. Future studies will examine these genes and networks to understand the exact mechanism(s) these phagocytic APC subsets use to kill C. neoformans in order to develop immunotherapeutic strategies to combat this deadly disease.

The PD-1/PD-L1 pathway is induced during Borrelia burgdorferi infection and inhibits T cell joint infiltration without compromising bacterial clearance.

The Lyme disease bacterial pathogen, Borrelia burgdorferi, establishes a long-term infection inside its mammalian hosts. Despite the continued presence of the bacteria in animal models of disease, inflammation is transitory and resolves spontaneously. T cells with limited effector functions and the inability to become activated by antigen, termed exhausted T cells, are present in many long-term infections. These exhausted T cells mediate a balance between pathogen clearance and preventing tissue damage resulting from excess inflammation. Exhausted T cells express a variety of immunoinhibitory molecules, including the molecule PD-1. Following B. burgdorferi infection, we found that PD-1 and its ligand PD-L1 are significantly upregulated on CD4+ T cells and antigen presenting cell subsets, respectively. Using mice deficient in PD-1, we found that the PD-1/PD-L1 pathway did not impact bacterial clearance but did impact T cell expansion and accumulation in the ankle joint and popliteal lymph nodes without affecting B cell populations or antibody production, suggesting that the PD-1/PD-L1 pathway may play a role in shaping the T cell populations present in affected tissues.

(Not) Home alone: Antigen presenting cell - T Cell communication in barrier tissues.

Priming of T cells by antigen presenting cells (APCs) is essential for T cell fate decisions, enabling T cells to migrate to specific tissues to exert their effector functions. Previously, these interactions were mainly explored using blood-derived cells or animal models. With great advances in single cell RNA-sequencing techniques enabling analysis of tissue-derived cells, it has become clear that subsets of APCs are responsible for priming and modulating heterogeneous T cell effector responses in different tissues. This composition of APCs and T cells in tissues is essential for maintaining homeostasis and is known to be skewed in infection and inflammation, leading to pathological T cell responses. This review highlights the commonalities and differences of T cell priming and subsequent effector function in multiple barrier tissues such as the skin, intestine and female reproductive tract. Further, we provide an overview of how this process is altered during tissue-specific infections which are known to cause chronic inflammation and how this knowledge could be harnessed to modify T cell responses in barrier tissue.

Interplay between plasmacytoid dendritic cells and tumor-specific T cells in peripheral blood influences long-term survival in non-small cell lung carcinoma.

Plasmacytoid dendritic cells (pDCs) represent a subset of antigen-presenting cells that play an ambivalent role in cancer immunity. Here, we investigated the clinical significance of circulating pDCs and their interaction with tumor-specific T cell responses in patients with non-small cell lung cancer (NSCLC, n = 126) . The relation between intratumoral pDC signature and immune checkpoint inhibitors efficacy was also evaluated. Patients with NSCLC had low level but activated phenotype pDC compared to healthy donors. In overall population, patients with high level of pDC (pDChigh) had improved overall survival (OS) compared to patients with pDClow, median OS 30.4 versus 20.7months (P = 0.013). This clinical benefit was only observed in stage I to III patients, but not in metastatic disease. We showed that patients harboring pDChigh profile had high amount of Th1-diffentiation cytokine interleukin-12 (IL-12) in blood and had functional T cells directed against a broad range of tumor antigens. Furthermore, a high pDC signature in the tumor microenvironment was associated with improved clinical outcome in patients treated with anti-PD-(L)1 therapy. Overall, this study showedthatcirculating pDChigh is associated with long-term OSin NSCLC and highlighted the predictive value of intratumor pDC signature in the efficacy of immune checkpoint inhibitors.