Genome-scale screens identify factors regulating tumor cell responses to natural killer cells.

To systematically define molecular features in human tumor cells that determine their degree of sensitivity to human allogeneic natural killer (NK) cells, we quantified the NK cell responsiveness of hundreds of molecularly annotated 'DNA-barcoded' solid tumor cell lines in multiplexed format and applied genome-scale CRISPR-based gene-editing screens in several solid tumor cell lines, to functionally interrogate which genes in tumor cells regulate the response to NK cells. In these orthogonal studies, NK cell-sensitive tumor cells tend to exhibit 'mesenchymal-like' transcriptional programs; high transcriptional signature for chromatin remodeling complexes; high levels of B7-H6 (NCR3LG1); and low levels of HLA-E/antigen presentation genes. Importantly, transcriptional signatures of NK cell-sensitive tumor cells correlate with immune checkpoint inhibitor (ICI) resistance in clinical samples. This study provides a comprehensive map of mechanisms regulating tumor cell responses to NK cells, with implications for future biomarker-driven applications of NK cell immunotherapies.

Determination and Quantitation of Cytotoxic T Cell-Mediated Cell Death.

Cytotoxic T cell-induced cell death is well documented. Cytotoxic T cell releases various cytolytic proteins. The cytolytic proteins induce target cell death. T cell-induced cell death can be measured by the lytic assay. One of the well-known lytic assays uses radioactive tracer, Chromium-51 (51Cr), and detects the amount of 51Cr released from target cells. This assay can detect cell death and the efficiency of the T cell-induced cell death by coculture effector cells (T cells) and target cells. This assay can determine the kinetics of the cell lysis. The issue of this approach is the use of radioactive material. This chapter describes measuring T cell-induced cell death by determining the epigenetic remodeling and the release of cytolytic proteins. Determine the efficiency of T cell-induced cell death by using a flow cytometry-based detection method.

Human Leukemia T-Cell Lines as Alternatives to Animal Use for Detecting Biologically Active Staphylococcal Enterotoxin Type B.

Staphylococcal enterotoxin type B (SEB) is associated with food poisoning. Current methods for the detection of biologically active SEB rely upon its ability to cause emesis when administered to live kittens or monkeys. This technique suffers from poor reproducibility and low sensitivity and is ethically disfavored over concerns for the welfare of laboratory animals. The data presented here show the first successful implementation of an alternative method to live animal testing that utilizes SEB super-antigenic activity to induce cytokine production for specific novel cell-based assays for quantifiable detection of active SEB. Rather than using or sacrificing live animals, we found that SEB can bind to the major histocompatibility complex (MHC) class II molecules on Raji B-cells. We presented this SEB-MHC class II complex to specific Vß5.3 regions of the human T-cell line HPB-ALL, which led to a dose-dependent secretion of IL-2 that is capable of being quantified and can further detect 10 pg/mL of SEB. This new assay is 100,000 times more sensitive than the ex vivo murine splenocyte method that achieved a detection limit of 1 µg/mL. The data presented here also demonstrate that SEB induced proliferation in a dose-dependent manner for cells obtained by three different selection methods: by splenocyte cells containing 22% of CD4+ T-cells, by CD4+ T-cells enriched to >90% purity by negative selection methods, and by CD4+ T-cells enriched to >95% purity by positive selection methods. The highly enriched and positively isolated CD4+ T-cells with the lowest concentration of antigen-presenting cells (APC) (below 5%) provided higher cell proliferation than the splenocyte cells containing the highest concentration of APC cells.

Determination of Cytotoxic Activities Against Melanoma Cells Using Flow Cytometry.

Within the adaptive and innate immune system, effector lymphocytes known as cytotoxic T cells (CTLs) or natural killer (NK) cells play an essential role in host defense against tumor cells and virally infected cells. Here we describe a flow cytometry-based method to quantify CTLs or NK cell cytotoxic activity against melanoma cells. In this assay, spleen cells, peripheral blood mononuclear cells (PBMCs), or purified NK cell preparations are co-incubated at different ratios with a target tumor cell line. The target cells are pre-labeled with a fluorescent dye to allow their discrimination from the effector cells. After the incubation period, killed target cells are identified by a nucleic acid stain, which specifically permeates dead cells. This method is amenable to both diagnostic and research applications.

Comparative analysis of assays to measure CAR T-cell-mediated cytotoxicity.

The antitumor efficacy of genetically engineered 'living drugs', including chimeric antigen receptor and T-cell receptor T cells, is influenced by their activation, proliferation, inhibition, and exhaustion. A sensitive and reproducible cytotoxicity assay that collectively reflects these functions is an essential requirement for translation of these cellular therapeutic agents. Here, we compare various in vitro cytotoxicity assays (including chromium release, bioluminescence, impedance, and flow cytometry) with respect to their experimental setup, appropriate uses, advantages, and disadvantages, and measures to overcome their limitations. We also highlight the US Food and Drug Administration (FDA) directives for a potency assay for release of clinical cell therapy products. In addition, we discuss advanced assays of repeated antigen exposure and simultaneous testing of combinations of immune effector cells, immunomodulatory antibodies, and targets with variable antigen expression. This review article should help to equip investigators with the necessary knowledge to select appropriate cytotoxicity assays to test the efficacy of immunotherapeutic agents alone or in combination.

Non-invasive image-based cytometry for high throughput NK cell cytolysis analysis.

Natural Killer (NK) cells are lymphocytes that are the first line of defense against malignantly transformed cells, virally infected cells and other stressed cell types. To study the cytolytic function of NK cells in vitro, a cytotoxicity assay is normally conducted against a target cancerous cell line. Current assay methods are typically performed in mixed 2D cocultures with destructive endpoints and low throughput, thereby limiting the scale, time-resolution, and relevance of the assay to in vivo conditions. Here, we evaluated a novel, non-invasive, quantitative image-based cytometry (qIBC) assay for detection of NK-mediated killing of target cells in 2D and 3D environments in vitro and compared its performance to two common flow cytometry- and fluorescence-based cytotoxicity assays. Similar to the other methods evaluated, the qIBC assay allowed for reproducible detection of target cell killing across a range of effector-to-target ratios with reduced variability. The qIBC assay also allowed for detection of NK cytolysis in 3D spheroids, which enabled scalable measurements of cell cytotoxicity in 3D models. Our findings suggest that quantitative image-based cytometry would be suitable for rapid, high-throughput screening of NK cytolysis in vitro, including in quasi-3D structures that model tissue environments in vivo.

Betulinic Acid-Azaprostanoid Hybrids: Synthesis and Pharmacological Evaluation as Anti-inflammatory Agents.

BACKGROUND: Prevention and treatment of chronic inflammatory diseases require effective and low-toxic medicines. Molecular hybridization is an effective strategy to enhance the biological activity of new compounds. Triterpenoid scaffolds are in the focus of attention owing to their anti-inflammatory, antiviral, antiproliferative, and immunomodulatory activities. Heteroprostanoids have different pleiotropic effects in acute and chronic inflammatory processes. OBJECTIVE: The study aimed to develop structurally new and low toxic anti-inflammatory agents via hybridization of betulinic acid with azaprostanoic acids. METHODS: A series of betulinic acid-azaprostanoid hybrids was synthesized. The synthetic pathway included the transformation of betulin via Jones' oxidation into betulonic acid, reductive amination of the latter and coupling obtained by 3ß-amino-3-deoxybetulinic acid with the 7- or 13-azaprostanoic acids and their homo analogues. The hybrids 1-9 were investigated in vivo on histamine-, formalin- and concanavalin A-induced mouse paw edema models and two models of pain - the acetic acid-induced abdominal writhing and the hotplate test. The hybrids were in vitro evaluated for cytotoxic activity on cancer (MCF7, U- 87 MG) and non-cancer humane cell lines. RESULTS: In the immunogenic inflammation model, the substances showed a pronounced anti-inflammatory effect, which was comparable to that of indomethacin. In the models of the exudative inflammation, none of the compounds displayed a statistically significant effect. The hybrids produced weak or moderate analgesic effects. All the agents revealed low cytotoxicity on human immortalized fibroblasts and cancer cell lines compared with 3ß- amino-3-deoxybetulinic acid and doxorubicin. CONCLUSION: The results indicate that the principal anti-inflammatory effect of hybrids is substantially provided with the triterpenoid scaffold and in some cases with the azaprostanoid scaffold, but the latter makes a significant contribution to reducing the toxicity of hybrids. Hybrid 1 is of interest as a potent low toxic agent against immune-mediated inflammation.

A Flow Cytometry-Based Whole Blood Natural Killer Cell Cytotoxicity Assay Using Overnight Cytokine Activation.

Background: Measurement of natural killer (NK) cell function has important clinical utility in several diseases. Although the flow cytometry (FC)-based 4-h NK cytotoxicity assay using peripheral blood mononuclear cells (PBMCs) in the clinical laboratory has been used for this purpose, this assay requires large amounts of blood and a rapid PBMC isolation step. Here, we developed an FC-based overnight NK cytotoxicity assay using whole blood (WB), and applied it to patients with liver diseases. Methods: Peripheral blood of healthy volunteers (n = 28) and patients with liver diseases, including hepatocellular carcinoma (n = 19) and liver cirrhosis (n = 7), was analyzed for complete blood count, absolute NK cell count, and NK cell activity (NKA). NKA was evaluated in three assay types: an FC-based overnight WB NK cytotoxicity assay using carboxyfluorescein diacetate succinimidyl ester-labeled K562 cells in the presence of various cytokine combinations [including interleukin (IL)-2, IL-18, and IL-21], an FC-based 4-h PBMC NK cytotoxicity assay, and an FC-based CD107a degranulation assay using WB and PBMCs. Results: Optimal cytokine combinations for NK cell activation in WB were determined (IL-2/IL-18, IL-2/IL-21, and IL-2/IL-18/IL-21). A good correlation was observed between WB and PBMC NK cytotoxicity assays; absolute NK cell counts were better correlated with the WB NK cytotoxicity assay than with the PBMC NK cytotoxicity assay. This WB NK cytotoxicity assay showed that patients with liver diseases had significantly lower NK cytotoxicity than healthy volunteers, under stimulation with various cytokines (p < 0.001). Conclusion: The proposed FC-based overnight WB NK cytotoxicity assay correlates well with the conventional 4-h PBMC NK cytotoxicity assay, demonstrating future potential as a supportive assay for clinical laboratory research and observational studies.

MRGPRX2 activation as a rapid, high-throughput mechanistic-based approach for detecting peptide-mediated human mast cell degranulation liabilities.

Mast cells play key roles in allergy, anaphylaxis/anaphylactoid reactions, and defense against pathogens/toxins. These cells contain cytoplasmic granules with a wide spectrum of pleotropic mediators that are released upon activation. While mast cell degranulation (MCD) occurs upon clustering of the IgE receptor bound to IgE and antigen, MCD is also triggered through non-IgE-mediated mechanisms, one of which is via Mas-related G protein-coupled receptor X2 (MRGPRX2). MRGPRX2 can be activated by many basic biogenic amines and peptides. Consequently, MRGPRX2-mediated MCD is an important potential safety liability for peptide therapeutics. To facilitate peptide screening for this liability in early preclinical drug development, a rapid, high-throughput engineered CHO-K1 cell-based MRGPRX2 activation assay was evaluated and compared to histamine release in CD34+ stem cell-derived mature human mast cells as a reference assay, using 30 positive control and 29 negative control peptides for MCD. Both G protein-dependent (Ca2+ endpoint) and -independent (ß-arrestin endpoint) pathways were assessed in the MRGPRX2 activation assay. The MRGPRX2 activation assay had a sensitivity of 100% for both Ca2+ and ß-arrestin endpoints and a specificity of 93% (ß-arrestin endpoint) and 83% (Ca2+ endpoint) compared to histamine release in CD34+ stem cell-derived mature human mast cells. These findings suggest that assessing MRGPRX2 activation in an engineered cell model can provide value as a rapid, high-throughput, economical mechanism-based screening tool for early MCD hazard identification during preclinical safety evaluation of peptide-based therapeutics.

Research into biocompatibility and cytotoxicity of daptomycin, gentamicin, vancomycin and teicoplanin antibiotics at common doses added to bone cement.

OBJECTIVES: This study aims to investigate the biocompatibility and cytotoxicity of daptomycin, gentamicin, vancomycin and teicoplanin at commonly-used dose intervals added to polymethylmethacrylate (PMMA) in vitro. MATERIALS AND METHODS: This prospective study was conducted between February 2016 and June 2016. Antibiotics were added to PMMA at doses frequently used in clinical practice. The antibiotic doses added were teicoplanin (2 g, 3 g, 4 g), gentamicin (0.5 g, 0.75 g, 1 g), daptomycin (0.5 g.) and vancomycin (2 g, 3 g, 4 g). Standard cement balls (10 mm) were created. Activated L929 mouse fibroblast cell culture was used for incubation. Agar diffusion, Cell Proliferation Kit II (XTT) test and electron microscope investigations were performed to examine biocompatibility and cytotoxicity. RESULTS: In the cytotoxicity test, teicoplanin at 4 g and daptomycin at 0.5 g doses were observed to cause reductions in viability percentages. The same doses caused 20% and 20-40% cell lysis indices during the agar diffusion test. On electron microscope images, cytotoxic effects in fibroblast cells and involvement with the surface of cement balls were observed. CONCLUSION: Gentamicin, vancomycin and teicoplanin were observed to be non-toxic and biocompatible at commonly-used dose intervals. Teicoplanin at 4 g and daptomycin at 0.5 g doses were identified to be cytotoxic and not biocompatible. When selecting antibiotics to be added to bone cement, care should be taken that the antibiotic is non-toxic and biocompatible.

In vivo assessment of respiratory burst inhibition by xenobiotic exposure using larval zebrafish.

Currently, assessment of the potential immunotoxicity of a given agent involves a tiered approach for hazard identification and mechanistic studies, including observational studies, evaluation of immune function, and measurement of susceptibility to infectious and neoplastic diseases. These studies generally use costly low-throughput mammalian models. Zebrafish, however, offer an excellent alternative due to their rapid development, ease of maintenance, and homology to mammalian immune system function and development. Larval zebrafish also are a convenient model to study the innate immune system with no interference from the adaptive immune system. In this study, a respiratory burst assay (RBA) was utilized to measure reactive oxygen species (ROS) production after developmental xenobiotic exposure. Embryos were exposed to non-teratogenic doses of chemicals and at 96 h post-fertilization, the ability to produce ROS was measured. Using the RBA, 12 compounds with varying immune-suppressive properties were screened. Seven compounds neither suppressed nor enhanced the respiratory burst; five reproducibly suppressed global ROS production, but with varying potencies: benzo[a]pyrene, 17ß-estradiol, lead acetate, methoxychlor, and phenanthrene. These five compounds have all previously been reported as immunosuppressive in mammalian innate immunity assays. To evaluate whether the suppression of ROS by these compounds was a result of decreased immune cell numbers, flow cytometry with transgenic zebrafish larvae was used to count the numbers of neutrophils and macrophages after chemical exposure. With this assay, benzo[a]pyrene was found to be the only chemical that induced a change in the number of immune cells by increasing macrophage but not neutrophil numbers. Taken together, this work demonstrates the utility of zebrafish larvae as a vertebrate model for identifying compounds that impact innate immune function at non-teratogenic levels and validates measuring ROS production and phagocyte numbers as metrics for monitoring how xenobiotic exposure alters the innate immune system.

Measurement of Natural Killer Cell-Mediated Cytotoxicity and Migration in the Context of Hepatic Tumor Cells.

Natural killer (NK) cells are a subset of the cytotoxic lymphocyte population of the innate immune system and participate as a first line of defense by clearing pathogen-infected, malignant, and stressed cells. The ability of NK cells to eradicate cancer cells makes them an important tool in the fight against cancer. Several new immune-based therapies are under investigation for cancer treatment which rely either on enhancing NK cell activity or increasing the sensitivity of cancer cells to NK cell-mediated eradication. However, to effectively develop these therapeutic approaches, cost-effective in vitro assays to monitor NK cell-mediated cytotoxicity and migration are also needed. Here, we present two in vitro protocols that can reliably and reproducibly monitor the effect of NK-cell cytotoxicity on cancer cells (or other target cells). These protocols are non-radioactivity-based, simple to set up, and can be scaled up for high-throughput screening. We also present a flow cytometry-based protocol to quantitatively monitor NK cell migration, which can also be scaled up for high-throughput screening. Collectively, these three protocols can be used to monitor key aspects of NK cell activity that are necessary for the cells' ability to eradicate dysfunctional target cells.

Interleukin-35 Suppresses CD8+ T Cell Activity in Patients with Viral Hepatitis-Induced Acute-on-Chronic Liver Failure.

BACKGROUND: Interleukin (IL)-35 is a newly indentified cytokine and induces immunotolerance via suppression of CD8+ T cell activity in chronic viral hepatitis. AIMS: To investigate the modulatory function of IL-35 to CD8+ T cells in viral hepatitis-induced acute-on-chronic liver failure (ACLF). METHODS: Fifty-five ACLF patients and 21 healthy controls were enrolled. Serum IL-35 concentration was measured by ELISA. Absolute accounts for T cells, immune checkpoint molecules, and cytotoxic molecules in CD8+ T cells were measured by flow cytometry and real-time PCR, respectively. Direct and indirect contact co-culture systems between CD8+ T cells and HepG2 cells were set up. The regulatory function of IL-35 to CD8+ T cells was assessed by measuring lactate dehydrogenase expression and cytokine production. RESULTS: Serum IL-35 concentration was elevated in ACLF patients and positively correlated with total bilirubin, but negatively correlated with prothrombin time activity. Peripheral CD8+ T cells showed exhausted phenotype in ACLF patients, which manifested as up-regulation of programmed death-1 (PD-1), cytotoxic T-lymphocyte-associated protein-4 (CTLA-4), and lymphocyte activation gene-3 (LAG-3) but down-regulation of perforin, granzyme B, and FasL. Recombinant IL-35 stimulation dampened cytotoxicity and interferon-γ production in both direct and indirect contact co-culture systems. This process was accompanied by elevation of PD-1, CTLA-4, and LAG3, as well as reduction of perforin, granzyme B, and FasL in CD8+ T cells. CONCLUSION: Elevated IL-35 suppressed both cytolytic and non-cytolytic activity of CD8+ T cells in ACLF patients.

Generating stem-like memory T cells with antioxidants for adoptive cell transfer immunotherapy of cancer.

Among the multiple factors that are responsible for the success of adoptive cell transfer (ACT) immunotherapy for cancer, the differentiation status of the in vitro expanded T cell product at the time of transfer seems to play a major role. In particular, less differentiated memory CD8+ T cells endowed with self-renewing capacity and multipotency exert the most potent antitumor activity. To this aim, expansion protocols that generate sufficient numbers of tumor-specific CD8+ T cells with superior capacity to persist in vivo following ACT are needed. We describe a procedure for the differentiation of TCF-1+ stem-like CD8+ memory T cells from peripheral blood naïve precursors that takes advantage of the use of antioxidants, in particular N-acetylcysteine (NAC), in combination with T cell receptor stimulation and proinflammatory cytokines. We additionally describe how to conduct in vitro assays to test the stem-like features of the generated cells at the phenotypic, functional and metabolic level. Balancing the oxidative metabolism by the addition of antioxidants during in vitro manipulation of CD8+ T cells results in the generation of cell products with potent antitumor characteristics following ACT.

Assessment of NK cell-mediated cytotoxicity by flow cytometry after rapid, high-yield isolation from peripheral blood.

Natural killer (NK) cells constitute the predominant innate lymphocyte subset that mediates the anti-viral and anti-tumor immune responses. NK cells use an array of innate receptors to sense their environment and to respond to infections, cellular stress and transformation. The resulting NK cell activation, including cytotoxicity and cytokine production, is a fundamental component of the early immune response. The most recent discoveries in NK cell biology have stimulated the translational research that has led to remarkable results for the treatment of human malignancies. Therefore, the rapid isolation of NK cells from the peripheral blood or tumor microenvironment and the subsequent assessment of cytolytic function are crucial to the study of their potency and NK cell-mediated immunosurveillance. Here, we provide protocols for NK cell isolation and the assessment of NK cell cytotoxicity using flow cytometry.

Two-dimensional dynamic evaluation of natural killer cell-mediated lysis of adherent target cells.

Cell-mediated cytotoxicity is a major function of cytotoxic lymphocytes. The cytotoxic function of immune effectors requires accurate and sensitive quantification as tumor immunotherapies are actively developed to treat growing types of tumors. Various methods have been developed to quantify this function. A first approach consists in measuring the externalization of LAMP-1 (lysosomal associated membrane 1), CD107a molecules transitory expressed at the cell surface by degranulating cytotoxic cells and is determined by flow cytometry. The focus of the chapter concerns the second approach that quantifies target cell lysis resulting from the close contact interaction with cytotoxic Natural Killer (NK) lymphocytes. For long time, target cell lysis was evaluated by chromium release assay, requiring use of radioactive labeled salt (51Cr) and specific devices not compatible with repeated tests performed for immunomonitoring of patients. Other methods include fluorimetric and bioluminescence assays. Monitoring immune cell-mediated lysis of adherent targets by the dynamic measure of cell proliferation using the Real time cell analyzer (RTCA) is a good alternative. The test relies on sensitive dynamic measure of cell index values during their interactions with cytotoxic immune effectors. The cell index increasing with cell proliferation rapidly drops in presence of immune cells. The lysis is quantified in reference with targets alone and expressed as percentages of lysis curves. Moreover, the dynamic monitoring of target cell index allows the evaluation of drugs, cytokines, mAbs on target cell lysis. Here we describe a robust and sensitive method for quantification of immune cell-mediated lysis of adherent targets.

Applications of microfluidic devices in advancing NK-cell migration studies.

Understanding how NK cells interact with tumor cells under specific microenvironment will be informative in development of NK-cell based immunotherapy. Applications of microfluidic devices in in vitro studies of NK-cell migrations offer unique opportunities to examine NK-cell migrations at single-cell under controlled cellular microenvironments. Novel devices can be created and engineered to present precise configuration that mimics cellular microenvironments for cell migration studies. We established previously the first application of a simple Y-shaped device for imaging and analysis of the abilities of the immature and mature DC to regulate murine IL-2 activated NK cell migrations. Here we reported the application of our recent technical development of a novel microfluidic device, which is also called the triple docking device (i.e., D3-Chip), for the studies of NK-cell migrations in NK-4T1 breast cancer cell interactions in vitro. Key features of this microfluidic device are its pump-free gradient generation, and the three-parallel units design that supports easy setup and parallel comparison of multiple experimental conditions. The cell docking structure enables the prealignment of all NK cells at the same "start" position before their exposures to the test conditions. As a result, quantification of cell displacement toward a chemical gradient can be quantified by enumeration of the number of cells migrated out of the docking structure and their displacements. Such microfluidic devices can be further modified in future to mimic the complex in vivo microenvironments to support more advanced investigations of NK-cell migratory responses in vitro.

Complementary approaches to study NKT cells in cancer.

NKT cells are a small but influential member of the T cell family, recognizing lipids presented by the non-classical MHC-like molecule CD1d rather than peptides presented by classical MHC molecules. They bridge between the innate and adaptive immune systems, serving as rapid responders but also allowing the T cell immune system to recognize lipid antigens, for example derived from tumors or bacteria. They also serve as potent regulatory cells, controlling other immune responses. Type I NKT cells use a semi-invariant T cell receptor (TCR) whereas type II use diverse TCRs. Most often, type I NKT cells promote tumor immunity whereas type II tend to suppress it, and the two subtypes crossregulate each other, forming an immunoregulatory axis. Lack of tools to study these important cells has limited the understanding of these, but newer tools have allowed great advances, especially in mouse models. These range from transgenic and knock-out mice to CD1d tetramers carrying ligands for type I or II NKT cells, to antibodies and NKT cell hybridomas. Here we describe these complementary tools and approaches and their use to study NKT cells and their role in the immunology and immunotherapy of cancer.

Assessment of IFN-γ and granzyme-B production by in "sitro" technology.

Tumor neantigens (TNAs) and tumor-associated antigens (TAAs) are crucial triggers of anticancer immune responses. Through major histocompatibility complex, such antigens activate T cells, which, by releasing interferon gamma (IFN-γ) and granzyme B (GRZB), act as crucial effectors against tumor onset and progression. However, in response to immune pressure, cancer cells use different strategies to favor the establishment of an immunosuppressive tumor microenvironment (TME). Elucidating the dynamics of tumor-host co-evolution provides novel opportunities for personalized cancer immunotherapies. The in sitro (in vitro+in situ) technology is an experimental approach involving the preparation of heterocellular cell suspensions from fresh tumors and their use in vitro. The in sitro experimental setup offers the possibility to (1) analyze immune-related parameters (e.g., quantification of cytokines released in the TME), (2) reveal the mechanism of action of drugs, and (3) unveil crucial cell-intrinsic and cell-extrinsic processes boosting anticancer immune responses. Nonetheless, the in sitro technology does not fully recapitulate the complexity of the tissue "in situ" nor models the patterns of infiltrating immune cell localization, and hence parallel experimentation should be scheduled. In this chapter we discuss in sitro technology to analyze and quantify IFN-γ and GRZB production by T cells either co-cultured with cancer cells in the presence of exogenous adjuvant stimuli (i.e., an antibody targeting the immune checkpoint programmed cell death protein 1, and recombinant calreticulin) and boosting with TAAs (i.e., the model SIINFEKL ovalbumin antigen). Specifically, we describe IFN-γ and GRZB quantification by flow cytometry, ELISA and ELISpot technologies.

Assessment of IFNγ responsiveness in patient-derived xenografts.

Patient-derived xenografts are a useful tool in cancer immunology, as they allow researchers to study human cancers in vivo when starting with a relatively small amount of human tumor tissue. These models make it possible to study tumor cell-intrinsic changes that occur in response to external stimuli including cytokines like interferon gamma (IFNγ) that are important for effective anti-tumor immune responses. IFNγ responsiveness can be measured by assessing surface expression of MHC class I on tumor cells, the molecule on which tumor antigens are presented to cytotoxic T cells in the tumor microenvironment. Low levels of MHC class I and lack of responsiveness have been associated with resistance to T-cell directed therapies like immune checkpoint inhibitors. In this chapter, we present a protocol for an assay to screen patient-derived xenografts for their responsiveness to IFNγ. The results of this assay can be used as a starting point for uncovering cancer cell-intrinsic mechanisms of resistance to immunotherapies in patient tumors.