Circulating Proteins Associated with Anti-IL6 Receptor Therapeutic Resistance in the Sera of Patients with Severe COVID-19.

Circulating proteomes provide a snapshot of the physiological state of a human organism responding to pathogenic challenges and drug interventions. The outcomes of patients with COVID-19 and acute respiratory distress syndrome triggered by the SARS-CoV2 virus remain uncertain. Tocilizumab is an anti-interleukin-6 treatment that exerts encouraging clinical activity by controlling the cytokine storm and improving respiratory distress in patients with COVID-19. We investigate the biological determinants of therapeutic outcomes after tocilizumab treatment. Overall, 28 patients hospitalized due to severe COVID-19 who were treated with tocilizumab intravenously were included in this study. Sera were collected before and after tocilizumab, and the patient's outcome was evaluated until day 30 post-tocilizumab infusion for favorable therapeutic response to tocilizumab and mortality. Hyperreaction monitoring measurements by liquid chromatography-mass spectrometry-based proteomic analysis with data-independent acquisition quantified 510 proteins and 7019 peptides in the serum of patients. Alterations in the serum proteome reflect COVID-19 outcomes in patients treated with tocilizumab. Our results suggested that circulating proteins associated with the most significant prognostic impact belonged to the complement system, platelet degranulation, acute-phase proteins, and the Fc-epsilon receptor signaling pathway. Among these, upregulation of the complement system by activation of the classical pathway was associated with poor response to tocilizumab, and upregulation of Fc-epsilon receptor signaling was associated with lower mortality.

Adoptive cell therapies in thoracic malignancies.

Immunotherapy has gained great interest in thoracic malignancies in the last decade, first in non-small cell lung cancer (NSCLC), but also more recently in small-cell lung cancer (SCLC) and malignant pleural mesothelioma (MPM). However, while 15-20% of patients will greatly benefit from immune checkpoint blockers (ICBs), a vast majority will rapidly exhibit resistance. Reasons for this are multiple: non-immunogenic tumors, immunosuppressive tumor microenvironment or defects in immune cells trafficking to the tumor sites being some of the most frequent. Current progress in adoptive cell therapies could offer a way to overcome these hurdles and bring effective immune cells to the tumor site. In this review, we discuss advantages, limits and future perspectives of adoptive cell therapy (ACT) in thoracic malignancies from lymphokine-activated killer cells (LAK), cytokine-induced killer cells (CIK), natural killer cells (NK), dendritic cells (DC) vaccines and tumor-infiltrating lymphocytes (TILs) to TCR engineering and CARs. Trials are still in their early phases, and while there may still be many limitations to overcome, a combination of these different approaches with ICBs, chemotherapy and/or radiotherapy could vastly improve the way we treat thoracic cancers.

Natural killer cell-directed therapies: moving from unexpected results to successful strategies.

Natural killer (NK) cells influence innate and adaptive immune host defenses. Existing data indicate that manipulating the balance between inhibitory and activating NK receptor signals, the sensitivity of target cells to NK cell-mediated apoptosis, and NK cell cross-talk with dendritic cells might hold therapeutic promise. Efforts to modulate NK cell trafficking into inflamed tissues and/or lymph nodes, and to counteract NK cell suppressors, might also prove fruitful in the clinic. However, deeper investigation into the benefits of combination therapy, greater understanding of the functional distinctions between NK cell subsets, and design of new tools to monitor NK cell activity are needed to strengthen our ability to harness the power of NK cells for therapeutic aims.

Enterocolitis due to immune checkpoint inhibitors: a systematic review.

Immune checkpoint inhibitors targeting cytotoxic T-lymphocyte-associated protein-4 (CTLA-4) and programmed death-1 (PD-1)/ligand are increasingly used to treat several types of cancer. These drugs enhance antitumour T-cell activity and therefore induce immune-related adverse effects (irAE), of which gastrointestinal (GI) irAE are among the most frequent and severe. This systematic literature review summarises the clinical manifestations, management and pathophysiology of GI irAE due to immune checkpoint inhibitors. GI irAE induced by anti-CTLA-4 are frequent, potentially severe and resemble IBD, whereas those induced by PD-1 blockade seem to be less frequent and clinically more diverse. Baseline symbiotic gut microbiota is associated with an enhanced antitumour response to immune checkpoint inhibitors and an increased susceptibility to developing enterocolitis, in patients treated with anti-CTLA-4. These findings open new perspectives for possible manipulation of the gut microbiota in order to better identify responders to immune checkpoint inhibitors and to increase their efficacy and safety.

Deep phenotyping of immune cell populations by optimized and standardized flow cytometry analyses.

Multicolor flow cytometry is a technology of choice for phenotyping of immune cells, and it can be used routinely for the follow up of patients in clinical trials. But it is challenging to define combinations of conjugated antibodies that efficiently allow the detailed analysis of major immune cell subsets and the identification of rare cell populations. In a collaborative work among the Immunology, Immunopathology, Immunotherapy (I3 ) laboratory, and the laboratory of immunomonitoring in oncology (L.I.O), we developed and validated 12 different 10-color flow cytometry panels that allow the deep immunophenotyping of cells from whole blood for the follow up of autoimmune and cancer patients. Here, we describe these optimized flow cytometry panels, showing that they provide the advanced analysis of T cells (including regulatory T cells), B cells, NK cells, MAIT cells, myeloid cells, monocytes, and dendritic cells. Most of the panels have been dried to improve standardization of the labeling and the entire procedure can be performed on less than 2 ml of whole blood. These deep immunophenotyping flow cytometry panels constitute a powerful tool for the monitoring of immune blood cells and will hopefully lead to the discovery of new biomarkers and potential therapeutic targets in autoimmune and cancer clinical trials. © 2018 International Society for Advancement of Cytometry.

Estimating causal effects of time-dependent exposures on a binary endpoint in a high-dimensional setting.

BACKGROUND: Recently, the intervention calculus when the DAG is absent (IDA) method was developed to estimate lower bounds of causal effects from observational high-dimensional data. Originally it was introduced to assess the effect of baseline biomarkers which do not vary over time. However, in many clinical settings, measurements of biomarkers are repeated at fixed time points during treatment and, therefore, this method needs to be extended. The purpose of this paper is to extend the first step of the IDA, the Peter Clarks (PC)-algorithm, to a time-dependent exposure in the context of a binary outcome. METHODS: We generalised the so-called "PC-algorithm" to take into account the chronological order of repeated measurements of the exposure and proposed to apply the IDA with our new version, the chronologically ordered PC-algorithm (COPC-algorithm). The extension includes Firth's correction. A simulation study has been performed before applying the method for estimating causal effects of time-dependent immunological biomarkers on toxicity, death and progression in patients with metastatic melanoma. RESULTS: The simulation study showed that the completed partially directed acyclic graphs (CPDAGs) obtained using COPC-algorithm were structurally closer to the true CPDAG than CPDAGs obtained using PC-algorithm. Also, causal effects were more accurate when they were estimated based on CPDAGs obtained using COPC-algorithm. Moreover, CPDAGs obtained by COPC-algorithm allowed removing non-chronological arrows with a variable measured at a time t pointing to a variable measured at a time t´ where t´ < t. Bidirected edges were less present in CPDAGs obtained with the COPC-algorithm, supporting the fact that there was less variability in causal effects estimated from these CPDAGs. In the example, a threshold of the per-comparison error rate of 0.5% led to the selection of an interpretable set of biomarkers. CONCLUSIONS: The COPC-algorithm provided CPDAGs that keep the chronological structure present in the data and thus allowed to estimate lower bounds of the causal effect of time-dependent immunological biomarkers on early toxicity, premature death and progression.

IL-15 Trans-Signaling with the Superagonist RLI Promotes Effector/Memory CD8+ T Cell Responses and Enhances Antitumor Activity of PD-1 Antagonists.

Tumors with the help of the surrounding environment facilitate the immune suppression in patients, and immunotherapy can counteract this inhibition. Among immunotherapeutic strategies, the immunostimulatory cytokine IL-15 could represent a serious candidate for the reactivation of antitumor immunity. However, exogenous IL-15 may have a limited impact on patients with cancer due to its dependency on IL-15Rα frequently downregulated in cancer patients. In this work, we studied the antitumor activity of the IL-15 superagonist receptor-linker-IL-15 (RLI), designed to bypass the need of endogenous IL-15Rα. RLI consists of human IL-15 covalently linked to the human IL-15Rα sushi(+) domain. In a mouse model of colorectal carcinoma, RLI as a stand-alone treatment could limit tumor outgrowth only when initiated at an early time of tumor development. At a later time, RLI was not effective, coinciding with the strong accumulation of terminally exhausted programmed cell death-1 (PD-1)(high) T cell Ig mucin-3(+) CD8(+) T cells, suggesting that RLI was not able to reactivate terminally exhausted CD8(+) T cells. Combination with PD-1 blocking Ab showed synergistic activity with RLI, but not with IL-15. RLI could induce a greater accumulation of memory CD8(+) T cells and a stronger effector function in comparison with IL-15. Ex vivo stimulation of tumor-infiltrated lymphocytes from 16 patients with renal cell carcinoma demonstrated 56% of a strong tumor-infiltrated lymphocyte reactivation with the combination anti-PD-1/RLI compared with 43 and 6% with RLI or anti-PD-1, respectively. Altogether, this work provides evidence that the sushi-IL-15Rα/IL-15 fusion protein RLI enhances antitumor activity of anti-PD-1 treatment and is a promising approach to stimulate host immunity.

IL-21-Induced MHC Class II+ NK Cells Promote the Expansion of Human Uncommitted CD4+ Central Memory T Cells in a Macrophage Migration Inhibitory Factor-Dependent Manner.

NK cells are critical for innate immunity-mediated protection. The main roles of NK cells rely on their cytotoxic functions or depend on the tuning of Th1 adaptive immunity by IFN-γ. However, the precise influence of inflammatory cytokines on NK cell and CD4 T lymphocyte interactions was never investigated. In this study, we provide evidence that IL-21, a cytokine produced during chronic inflammation or infectious diseases, promotes the differentiation of a specific subset of NK cells coexpressing CD86 and HLA-DR and lacking NKp44. More importantly, IL-21-propagated HLA-DR(+) NK cells produce macrophage migration inhibitory factor and provide costimulatory signaling during naive CD4(+) T cell priming inducing the differentiation of uncommitted central memory T cells. Central memory T cells expanded in the presence of HLA-DR(+) NK cells are CXCR3(+)CCR6(-)CCR4(-)CXCR5(-) and produce IL-2, as well as low levels of TNF-α. Costimulation of CD4(+) T cells by HLA-DR(+) NK cells prevents the acquisition of effector memory phenotype induced by IL-2. Moreover, we identified this population of NK HLA-DR(+) macrophage migration inhibitory factor(+) cells in inflammatory human appendix. Collectively, these results demonstrate a novel function for IL-21 in tuning NK and CD4(+) T cell interactions promoting a specific expansion of central memory lymphocytes.

Predictive biomarkers for programmed death-1/programmed death ligand immune checkpoint inhibitors in nonsmall cell lung cancer.

PURPOSE OF REVIEW: Immune checkpoint inhibitors, antiprogrammed death receptor 1 (anti-PD-1)/antiprogrammed death-ligand 1 (anti-PD-L1), are new therapeutic regimens for managing advanced nonsmall cell lung cancer patients, giving an overall response rate of approximately 20% as monotherapy in second-line treatment. The use of predictive biomarkers for identifying patients suitable for these therapies is an important issue not only for making treatment decisions, but also from a medical economic point of view. RECENT FINDINGS: Among potential predictive biomarker candidates for anti-PD-1/PD-L1 treatments in nonsmall cell lung cancer, the expression of PD-L1 (as determined by immunohistochemistry) is currently the most studied. PD-L1 positivity has been associated with higher response rate to anti-PD-1/PD-L1 therapies. However, several observations suggest that the predictive value of PD-L1 expression is not clear-cut. We review other potential predictive biomarkers, including programmed death-ligand 2, IFN-γ, and genetic signatures. SUMMARY: Standardized techniques and conditions for evaluating PD-L1 expression (tissue quality and age, percentage positivity threshold, managing heterogeneous and dynamic expression) are critical for establishing the use of this protein as a predictive marker. Care should be also taken when using anti-PD-1/PD-L1 therapies in combination with other therapies, which may impact the predictive value of PD-L1 expression.

Dendritic cell-derived exosomes as immunotherapies in the fight against cancer.

Exosomes are nanometric membrane vesicles of late endosomal origin released by most, if not all, cell types as a means of sophisticated intercellular communication. A multitude of studies showed how exosomes can mediate and regulate immune responses against tumors. Dendritic cell-derived exosomes (Dex) have received much attention as immunotherapeutic anticancer agents since the discovery that they harbor functional MHC-peptide complexes, in addition to various other immune-stimulating components, that together facilitate immune cell-dependent tumor rejection. The therapeutic potential of Dex has been substantiated with their development and clinical testing in the treatment of cancer. This review focuses on mechanisms by which Dex interact with and influence immune cells and describes how they can be engineered to promote their immunogenic capacity as novel and dynamic anticancer agents.

Treatment of gastric peritoneal carcinomatosis by combining complete surgical resection of lesions and intraperitoneal immunotherapy using catumaxomab.

BACKGROUND: The peritoneum is one of the most frequent sites of recurrent gastric carcinoma after curative treatment, despite the administration of pre- and/or postoperative systemic chemotherapy. Indeed, the prognosis of peritoneal carcinomatosis from gastric carcinoma continues to be poor, with a median survival of less than one year with systemic chemotherapy. Whereas the prognosis of peritoneal carcinomatosis from colorectal cancer has changed with the development of locally administered hyperthermic intraperitoneal chemotherapy (HIPEC), survival results following carcinomatosis from gastric cancer remain disappointing, yielding a 5-year survival rate of less than 20%. Innovative surgical therapies such as intraperitoneal immunotherapy therefore need to be developed for the immediate postoperative period after complete cytoreductive surgery. In a recent randomised study, a clinical effect was obtained after intraperitoneal infusion of catumaxomab in patients with malignant ascites, notably from gastric carcinoma. Catumaxomab, a nonhumanized chimeric antibody, is characterized by its unique ability to bind to three different types of cells: tumour cells expressing the epithelial cell adhesion molecule (EpCAM), T lymphocytes (CD3) and also accessory cells (Fcγ receptor). Because the peritoneum is an immunocompetent organ and up to 90% of gastric carcinomas express EpCAM, intraperitoneal infusion of catumaxomab after complete resection of all macroscopic disease (as defined in the treatment of carcinomatosis from colorectal cancer) could therefore efficiently treat microscopic residual disease. METHODS/DESIGN: The aim of this randomized phase II study is to assess 2-year overall survival after complete resection of limited carcinomatosis synchronous with gastric carcinoma, followed by an intraperitoneal infusion of catumaxomab with different total doses administered in each of the 2 arms. Close monitoring of peri-opertive mortality, morbidity and early surgical re-intervention will be done with stopping rules. Besides this analysis, translational research will be conducted to determine immunological markers of catumaxomab efficacy and to correlate these markers with clinical efficacy.

Human CD90 identifies Th17/Tc17 T cell subsets that are depleted in HIV-infected patients.

By revisiting CD90, a GPI-anchored glycoprotein, we show that CD90 is expressed by a subset of CD4(+) and CD8(+) human T cells. CD4(+)CD90(+) cells share similarities with Th17 cells because they express the Th17-specific transcription factor RORC2 and produce IL-17A. CD4(+)CD90(+) cells are activated memory T cells that express the gut mucosal markers CCR6, CD161, and the α(4) and ß(7) integrins. Compared with CD90-depleted CCR6(+) memory Th17 cells, CD4(+)CD90(+) cells express higher levels of IL-22 and proinflammatory cytokines (IL-6, TNF-α and GM-CSF), but they produce lower levels of IL-21 and no IL-9. Analyses of CD8(+)CD90(+) cells reveal that they express RORC2 and are able to produce higher levels of IL-17A, IL-22, and CCL20 compared with CD90-depleted CD8(+) cells. These data show that CD90 identifies Th17 and Tc17 cells with a peculiar cytokine profile. Studies of circulating CD90(+) cells in HIV patients show that CD90(+) cells are decreased with an imbalance of the CD4(+)CD90(+)/regulatory T cell ratio in nontreated patients compared with treated patients and healthy donors. Overall, human CD90 identifies a subset of Th17 and Tc17 cells within CD4(+) and CD8(+) T cells, respectively, which are depleted during HIV infection.

Blood-based circulating biomarkers for prediction of immune-checkpoint inhibitors efficacy in renal cell carcinoma.

Immune checkpoint inhibitors (ICI)-based combinations have become the standard first-line treatment for advanced clear cell renal cell carcinoma (ccRCC). Despite significant improvements in survival and the achievement of sustained long-term responses, a subset of patients remains refractory to ICI, and most will eventually develop resistance. Thus, identifying predictive biomarkers for ICI efficacy and resistance is essential for optimizing therapeutic strategies. Up to now, tissue-based biomarkers have not been successful as predictive biomarkers in RCC. Circulating blood-based biomarkers offer a promising alternative. These biomarkers, including circulating immune cells, soluble factors, tumor-derived markers, and those based on metabolomics, are less invasive, offer reproducibility over time, and provide a comprehensive assessment of tumor biology and patient immune status, as well as allow dynamic monitoring during treatment. This review aims to evaluate the current evidence on the different candidate circulating biomarkers being investigated for their potential to predict ICI efficacy in RCC patients.

B cells and the coordination of immune checkpoint inhibitor response in patients with solid tumors.

Immunotherapy profoundly changed the landscape of cancer therapy by providing long-lasting responses in subsets of patients and is now the standard of care in several solid tumor types. However, immunotherapy activity beyond conventional immune checkpoint inhibition is plateauing, and biomarkers are overall lacking to guide treatment selection. Most studies have focused on T cell engagement and response, but there is a growing evidence that B cells may be key players in the establishment of an organized immune response, notably through tertiary lymphoid structures. Mechanisms of B cell response include antibody-dependent cellular cytotoxicity and phagocytosis, promotion of CD4+ and CD8+ T cell activation, maintenance of antitumor immune memory. In several solid tumor types, higher levels of B cells, specific B cell subpopulations, or the presence of tertiary lymphoid structures have been associated with improved outcomes on immune checkpoint inhibitors. The fate of B cell subpopulations may be widely influenced by the cytokine milieu, with versatile roles for B-specific cytokines B cell activating factor and B cell attracting chemokine-1/CXCL13, and a master regulatory role for IL-10. Roles of B cell-specific immune checkpoints such as TIM-1 are emerging and could represent potential therapeutic targets. Overall, the expanding field of B cells in solid tumors of holds promise for the improvement of current immunotherapy strategies and patient selection.

Impact of Clonal Hematopoiesis-Associated Mutations in Phase I Patients Treated for Solid Tumors: An Analysis of the STING Trial.

PURPOSE: With liquid biopsy's widespread adoption in oncology, an increased number of clonal hematopoiesis-associated mutations (CHm) have been identified in patients with solid tumors. However, its impact on patient outcomes remains unclear. This study aimed to analyze and describe CHm in a cohort of phase I patients. METHODS: Retrospective data collection from medical records and molecular profiles (Foundation One Liquid CDx Assay) was performed before first study drug administration at the Drug Development Department of Gustave Roussy (France) within the STING trial (ClinicalTrials.gov identifier: NCT04932525). CHm prevalence was assessed using any and ≥1% variant allele frequency (VAF) in epigenetic modifier genes (DNMT3A, TET2, and ASXL1). RESULTS: From January 2021 to December 2022, 255 patients were enrolled in a phase I clinical trial. A total of 55% were male, with a median age of 62 years (24-86). Principal tumor locations were GI (27%) and genitourinary (21%). Overall, 104 patients (41%) had at least one CHm in liquid biopsy, with 55 patients (22%) having a VAF of ≥ 1%. The most frequent mutation was DNMT3A 73% at any VAF (n = 76) and 22% at 1% VAF (n = 23). Median progression-free survival (PFS) and overall survival were 3.8 months (m) for the CHm group versus 3.2 m for nonclonal hematopoiesis (CH; P = .08) and 18.26 m CHm versus 15.8 m non-CH (P = .9), respectively. PFS increased in the CHm population treated with targeted therapy (hazard ratio, 0.6 [95% CI, 0.42 to 0.84]; P = .004). CONCLUSION: CHm was commonly found in patients with solid tumors treated in phase I trials, with a prevalence of 41% in our cohort. The most frequently mutated gene was DNMT3A. The presence of CHm had no impact on the population of patients treated in the phase I trials.

Safety and efficacy of nivolumab in elderly patients with metastatic clear cell renal cell carcinoma: Analysis of the NIVOREN GETUG-AFU 26 study.

INTRODUCTION: Immune checkpoint inhibitors are standard of care in metastatic renal cell carcinoma but their activity and safety in elderly patients is insufficiently explored. We evaluated outcomes of elderly patients with mRCC treated with nivolumab in the GETUG-AFU 26 NIVOREN phase 2 trial (NCT03013335) and conducted exploratory circulating biomarker analyses. METHODS: Patients with mRCC were treated with nivolumab after at least one antiangiogenic therapy. The main endpoint of this analysis was safety in patients ≥ 70 years old (y.o), as per the rate of treatment-related grade 3-5 events (TRAE). Secondary endpoints included overall response rate (ORR), progression-free survival (PFS), overall survival. Exploration of candidate biomarkers associated with aging included baseline circulating cytokines involved in inflammation, adhesion, immune checkpoints, angiogenesis (IL6, IL7, IL8, BAFF, CXCL13, VCAM-1, 4-1BB, VEGF). RESULTS: Of 720 patients, 515 were < 70 y.o and 205 ≥ 70 y.o. Patients ≥ 70 y.o exhibited numerically less IMDC poor risk disease (21.0% vs 26.9%), sarcomatoid component (4.9% vs 9.8%) or brain metastases (5.9% vs. 14.7%), but more previous treatment lines (≥ 2 in 54.1% vs 48.5%). TRAE were higher in patients ≥ 70 y.o (24.9% vs. 17.9%, p = 0.033). Respective ORR (19.2% vs. 22.1%) and median PFS (4.5 versus 3.0 months, HR 0.97 [95%CI 0.81-1.15]) were similar. Overall survival was shorter in patients ≥ 70 y.o (19.3 versus 26.9 months, HR 1.26 [95%CI 1.04-1.51]), but not significantly in a competitive risk model. Only V-CAM1 and 4-1BB were found to be increased in patients ≥ 70 y.o. CONCLUSIONS: Nivolumab displayed higher grade 3/4 TRAE but manageable toxicity in elderly patients, with sustained activity. Elderly patients did not display specific inflammatory or angiogenic circulating profiles.

Metabolic tumor volume assessed by 18F FDG - PET CT scan as a predictive biomarker for immune checkpoint blockers in advanced NSCLC and its biological correlates.

PURPOSE: This study aimed to explore metabolic tumor volume (tMTV) as assessed 18F-fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG-PET/CT), and understand its biological meaning in patients with NSCLC exposed to immune checkpoint blockers(ICBs). EXPERIMENTAL DESIGN: In this study, patients with advanced NSCLC and a positive PET scan within 42 days of first line treatment were enrolled in 11 institutions across 4 countries. Total MTV (tMTV) was analyzed, with a 42% SUVmax threshold. Survival was analyzed according to high tMTV (≥ median). Plasma proteomic profile, whole exome, transcriptome and other analysis were performed on monocentric cohorts to explore its biological correlates. RESULTS: Of the 518 patients included, 167 received ICBs, 257 had chemotherapy plus ICBs, and 94 had chemotherapy. Median tMTV was 99 cm3. Median overall survival (OS) for patients with high tMTV treated with ICBs was 11.4 months vs 29.6 months (P<0.0012) for those with low tMTV. In patients receiving chemotherapy-ICB tMTV did not correlate with OS (P=0.099). In patients with PD-L1≥1% and high tMTV, chemotherapy-ICB combination was associated with longer OS compared with ICBs alone (20 vs 11.4 months,p=0.026), while no survival differences observed in low tMTV group. High tMTV correlated (and its detrimental effect seems to be driven by) a specific proteomic profile and increase in genomic instability. CONCLUSION: Our analysis indicates high tTMV is linked to an increase in systemic inflammation, specific cytokines production and chromosomal instability. tTMV may serve as one of the biomarker to select the best upfront strategy in patients with PD-L1 positive advanced NSCLC.

acDCs enhance human antigen-specific T-cell responses.

Detection of human Ag-specific T cells is limited by sensitivity and blood requirements. As dendritic cells (DCs) can potently stimulate T cells, we hypothesized that their induction in PBMCs in situ could link Ag processing and presentation to Ag-specific T-cell activation. To this end, unfractionated PBMCs (fresh or frozen) or whole blood were incubated for 48 hours with protein or peptide Ag together with different DC-activating agents to rapidly and sequentially induce, pulse, and mature DCs. DC activation was therefore lined up with Ag recognition by neighboring T cells, thus telescoping the sequential steps of T-cell activation. Efficient processing of protein Ags made prior knowledge of epitopes and HLA restrictions dispensable. While reducing stimulation time, manipulation and blood requirements, in situ DC induction specifically amplified Ag-specific T-cell responses (cytokine secretion, proliferation, CD137/CD154 up-regulation, and binding of peptide-HLA multimers). IL-1ß, although released by DCs, was also secreted in an Ag-specific fashion, thus providing an indirect biomarker of T-cell responses. These accelerated cocultured DC (acDC) assays offered a sensitive means with which to evaluate T-cell responses to viral and melanoma Ag vaccination, and may therefore find application for immune monitoring in viral, tumor, autoimmune, and transplantation settings.

A novel dendritic cell subset involved in tumor immunosurveillance.

The interferon (IFN)-gamma-induced TRAIL effector mechanism is a vital component of cancer immunosurveillance by natural killer (NK) cells in mice. Here we show that the main source of IFN-gamma is not the conventional NK cell but a subset of B220(+)Ly6C(-) dendritic cells, which are atypical insofar as they express NK cell-surface molecules. Upon contact with a variety of tumor cells that are poorly recognized by NK cells, B220(+)NK1.1(+) dendritic cells secrete high levels of IFN-gamma and mediate TRAIL-dependent lysis of tumor cells. Adoptive transfer of these IFN-producing killer dendritic cells (IKDCs) into tumor-bearing Rag2(-/-)Il2rg(-/-) mice prevented tumor outgrowth, whereas transfer of conventional NK cells did not. In conclusion, we identified IKDCs as pivotal sensors and effectors of the innate antitumor immune response.