Antigen-experienced Effector Research Articles

Persistence of peripheral CD8 + CD28− T cells indicates a favourable outcome and tumour immunity in first-line HER2-positive metastatic breast cancer

BackgroundThe contradictory role of CD8 + CD28− T cells in tumour immunity has been reported, while their biological and clinical significance in HER2-positive metastatic breast cancer (MBC) is still unknown.MethodsHER2-positive MBC patients with no prior therapy in the metastatic setting were retrospectively recruited at two medical centres. Peripheral CD8 + CD28− T cells (pTCD8+CD28-) were detected at baseline and following therapeutic intervals. Progression-free survival (PFS) was compared according to pTCD8+CD28− levels. The molecular features of pTCD8+CD28− and its correlation with tumour immunity were also investigated.ResultsA total of 252 patients were enrolled, and the median follow-up time was 29.6 months. pTCD8+CD28− high at baseline has prolonged PFS compared to pTCD8+CD28− low (P = 0.001). Patients who maintained pTCD8+CD28− high had a longer PFS than those who kept pTCD8+CD28− low (P < 0.001). The enhanced pTCD8+CD28− level also indicates a longer PFS compared to pTCD8+CD28− low (P = 0.025). Here, pTCD8+CD28- was demonstrated as an antigen-experienced effector T cell. Higher IL-2 level (P = 0.034) and lower TGF-β level (P = 0.016) in the serum and highly infiltrated CD8 + CD28− T cells (P = 0.037) were also connected to pTCD8+CD28− high.ConclusionsHigh pTCD8+CD28− level is associated with a favourable tumour immunity and a better PFS of HER2-targeting therapy in MBC patients.

Abstract 719: A tumor-activated PD1/IL2 bispecific molecule, designed to overcome IL-2 receptor-mediated clearance, improve tolerability and stimulate antigen-experienced CD8+ T cells in the tumor microenvironment of murine models

Abstract PD-1/PD-L1 therapies have shown significant activity across a range of tumor types, however, 70-90% of patients do not derive durable benefit. In preclinical settings, delivery of PD-1 blockade and IL-2 agonism in cis via a bispecific molecule, comprising a PD-1 antibody fused to IL-2, has demonstrated superior activity compared to delivery of individual components or their combination. Targeting of IL-2 to PD-1+ cells in cis has been shown to drive a unique differentiation path endowing CD8+ T cells with enhanced functionality. However, we show that the IL-2 component in an unmasked PD1/IL2 bispecific molecule dominates its pharmacology, driving marked peripheral activation of immune cells, rapid IL-2 receptor-mediated clearance and systemic toxicity. To address these challenges and enable tumor-specific activity, we designed a PD1/IL2 bispecific molecule that incorporates a single domain antibody-based mask to bind to the IL-2 component and maintain it in a quiescent state until activated by prevalent and dysregulated proteases in the tumor microenvironment (TME). In preclinical models, the affinity-optimized mask prevented peripheral IL-2 receptor binding, associated toxicity and receptor-mediated clearance. Improved pharmacokinetics of our tumor-activated PD1/IL2 enabled PD1 antibody-like exposures and is projected to achieve complete blockade of PD1 signaling. Tumor-activated PD1/IL2 significantly inhibited tumor growth compared to anti-PD-1 alone or vehicle and demonstrated improved tolerability compared to an unmasked PD1/IL2 bispecific in mouse models. In addition, pharmacodynamic activity of tumor-activated PD1/IL2 was restricted to the TME. Consistent with the masked design, we observed no significant change in CD8+ T cells in the periphery and significant increases in antigen specific CD8+ T cells, memory CD8+ T cells and TCF1+ stem-like CD8+ T cells in the TME. Ex vivo protease cleavage assays performed in human samples demonstrated efficient activation of tumor-activated PD1/IL2 by multiple tumor types and minimal activation in human plasma. In non-human primates, tumor-activated PD1/IL2 achieved tolerable exposures that were comparable to those of existing PD-1 blocking immunotherapies. Taken together, these preclinical data suggest that tumor-activated PD1/IL2 has the potential to improve upon existing PD-1/PD-L1 immunotherapies by inhibiting PD-1/PD-L1 axis and simultaneously directing immunostimulatory IL-2 to antigen-experienced effector cell populations in the TME. Citation Format: Ertan Eryilmaz, Wilson Guzman, Stephanie Hsiao, Parker Johnson, Lisa Quinn, Jimit Lakhani, Brendan Whalen, Rosa Quiroz, Kurt Jenkins, Bernard Lanter, Oleg Yerov, Will Scott, Justin Greene, Zhen Liu, Jason Hedges, Megan McLaughlin, Sallyann Vu, Chelsea Turcotte, Jacob Taylor, Caitlin O'Toole, Magali Pederzoli-Ribeil, Haley Duprey, Natalia Malkova, Damiano Fantini, David Crowe, Kyle Smith, Joseph Card, Janice Lee, Kerri Smith, Benjamin Nicholson, Jennifer O'Neil, Carl U. Bialucha. A tumor-activated PD1/IL2 bispecific molecule, designed to overcome IL-2 receptor-mediated clearance, improve tolerability and stimulate antigen-experienced CD8+ T cells in the tumor microenvironment of murine models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 719.

Abstract PR16: Neutrophil-intrinsic tumor necrosis factor (TNF) is a novel driver of T-cell and cancer-associated fibroblast (CAF) dysfunction in pancreatic cancer

Abstract INTRODUCTION: We have recently shown that neutrophilic myeloid-derived suppressor cells (MDSC) are the dominant source of TNF in the pancreatic ductal adenocarcinoma (PDAC) tumor microenvironment (TME). Moreover, neutrophil-derived TNF amplifies stromal fibrosis and immune tolerance via transmembraneTNF-TNFR2 interactions to promote therapeutic resistance in PDAC. Here, we develop a novel tumor-bearing murine model with efficient neutrophil lineage-restricted inactivation of Tnf to mechanistically dissect the impact of neutrophil-intrinsic TNF on stromal and T-cell dysfunction in PDAC. METHODS: We generated a neutrophil-lineage restricted MRP8Cre/+Tnfflox/flox model (Neu-TnfKO) by crossing Tnfflox/flox mice with mice bearing Cre-recombinase under control of MRP8 neutrophilic promoter, and confirmed &amp;gt;98% Tnf reduction in circulating neutrophils. Orthotopically implanted KPC tumors in Neu-TnfKO vs. littermates (MRP8Cre+/−Tnf+/+ or MRP8Cre-/−Tnffl/fl) were subjected to single-cell RNAseq (scRNAseq), flow cytometric immunophenotyping, and tissue histology. RESULTS: Compared with littermate controls, primary tumor weights and frequency of liver metastasis were significantly reduced in Neu-TnfKO mice. ScRNAseq in CD45− fraction of d21 tumors in Neu-TnfKO vs. control mice revealed downregulation of myofibroblastic features (i.e., Ccn2, Tgfb1), hypoxia signaling, and metabolic dysregulation in CAF single-cell transcriptomes. Tissue histology in Neu-TnfKO tumors revealed striking attenuation in fibrotic collagen deposition, and myofibril organization. Moreover, Lrrc15—implicated as a central regulator of CAF-driven immunotherapy resistance—was downregulated in Neu-TnfKO CAFs. This remodeling of stromal fibrosis manifested in increased trafficking of T-cells into Neu-TnfKO vs. littermate tumors via immunostaining and flow cytometry. ScRNAseq in CD45+ fractions of Neu-TnfKO mice corroborated enrichment in effector/helper T-cell and attenuation of MDSC and macrophage populations. In investigating if neutrophil-restricted Tnf silencing invokes reprogramming of T-cell single-cell transcriptomes, we observed global skewness towards effector vs exhausted programming in Neu-TnfKO tumors; enrichment of pathways related to ribosomal activation, interferon signaling, and negative regulation of T-cell apoptosis; and overexpression of multiple effector function genes—e.g., Adgre5, Cam1kd, Dgka—together indicating functional T-cell activation. Flow cytometry validated this activated CD8+ T-cell phenotype in Neu-TnfKO tumor-infiltrating by highlighting increased antigen-experienced (PD1+CD39neg) and short-lived effector populations (P&amp;lt;0.0001), and also revealed reduction in terminally exhausted (CD69+Ly108− in PD1hi) CD8+ T-cell subsets (P=0.028). CONCLUSIONS: Conditional silencing of neutrophilic-restricted TNF reprograms the immunotherapy-restrictive CAF and T-cell landscapes in the PDAC TME. Compartment-specific inhibition of TNF may be a provocative strategy to overcome immunotherapy resistance in PDAC. Citation Format: Anna Bianchi, Haleh Amirian, Iago De Castro Silva, Ifeanyichukwu Ogobuiro, Karthik Rajkumar, Andrew Mark Adams, Vanessa Garrido, Samara Singh, Siddharth Mehra, Christine Rafie, Nagarj Nagathihalli, Erietta Stelekati, Nipun Merchant, Jashodeep Datta. Neutrophil-intrinsic tumor necrosis factor (TNF) is a novel driver of T-cell and cancer-associated fibroblast (CAF) dysfunction in pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr PR16.

Adding Fuel to the Fire? A Role of Intraepithelial Lymphocytes in Enteric Immune Responses to SARS-CoV-2 Infection

Adding Fuel to the Fire? A Role of Intraepithelial Lymphocytes in Enteric Immune Responses to SARS-CoV-2 Infection

Human Regulatory T Cells From Umbilical Cord Blood Display Increased Repertoire Diversity and Lineage Stability Relative to Adult Peripheral Blood.

The human T lymphocyte compartment is highly dynamic over the course of a lifetime. Of the many changes, perhaps most notable is the transition from a predominantly naïve T cell state at birth to the acquisition of antigen-experienced memory and effector subsets following environmental exposures. These phenotypic changes, including the induction of T cell exhaustion and senescence, have the potential to negatively impact efficacy of adoptive T cell therapies (ACT). When considering ACT with CD4+CD25+CD127–/lo regulatory T cells (Tregs) for the induction of immune tolerance, we previously reported ex vivo expanded umbilical cord blood (CB) Tregs remained more naïve, suppressed responder T cells equivalently, and exhibited a more diverse T cell receptor (TCR) repertoire compared to expanded adult peripheral blood (APB) Tregs. Herein, we hypothesized that upon further characterization, we would observe increased lineage heterogeneity and phenotypic diversity in APB Tregs that might negatively impact lineage stability, engraftment capacity, and the potential for Tregs to home to sites of tissue inflammation following ACT. We compared the phenotypic profiles of human Tregs isolated from CB versus the more traditional source, APB. We conducted analysis of fresh and ex vivo expanded Treg subsets at both the single cell (scRNA-seq and flow cytometry) and bulk (microarray and cytokine profiling) levels. Single cell transcriptional profiles of pre-expansion APB Tregs highlighted a cluster of cells that showed increased expression of genes associated with effector and pro-inflammatory phenotypes (CCL5, GZMK, CXCR3, LYAR, and NKG7) with low expression of Treg markers (FOXP3 and IKZF2). CB Tregs were more diverse in TCR repertoire and homogenous in phenotype, and contained fewer effector-like cells in contrast with APB Tregs. Interestingly, expression of canonical Treg markers, such as FOXP3, TIGIT, and IKZF2, were increased in CB CD4+CD127+ conventional T cells (Tconv) compared to APB Tconv, post-expansion, implying perinatal T cells may adopt a default regulatory program. Collectively, these data identify surface markers (namely CXCR3) that could be depleted to improve purity and stability of APB Tregs, and support the use of expanded CB Tregs as a potentially optimal ACT modality for the treatment of autoimmune and inflammatory diseases.

Dendritic Cells and T Cells Interact Within Murine Afferent Lymphatic Capillaries.

Afferent lymphatic vessels contribute to immunity by transporting antigen and leukocytes to draining lymph nodes (LNs) and are emerging as new players in the regulation of peripheral tolerance. Performing intravital microscopy in inflamed murine ear skin we found that migrating dendritic cells (DCs) and antigen-experienced effector T cells spend considerable time arresting or clustering within afferent lymphatic capillaries. We also observed that intralymphatic T cells frequently interacted with DCs. When imaging polyclonal T cells during an ongoing contact-hypersensitivity response, most intralymphatic DC-T cell interactions were short-lived. Conversely, during a delayed-type-hypersensitivity response, cognate antigen-bearing DCs engaged in long-lived MHCII-(I-A/I-E)-dependent interactions with antigen-specific T cells. Long-lived intralymphatic DC-T cell interactions reduced the speed of DC crawling but did not delay overall DC migration to draining LNs. While further consequences of these intralymphatic interactions still need to be explored, our findings suggest that lymphatic capillaries represent a unique compartment in which adaptive immune interaction and modulation occur.

Genealogy, Dendritic Cell Priming, and Differentiation of Tissue-Resident Memory CD8+ T Cells.

Tissue-resident memory CD8+ T (Trm) cells define a distinct non-recirculating subset. Trm cells constitute a first line of defense against local infections in barrier tissues, but they are also found in non-barrier tissues and play a role in antitumor immunity. Their differentiation in tissues and their phenotypical, transcriptional, and functional characteristics are the object of active research. Herein, we will discuss the potential existence of committed CD8+ Trm precursors and the genealogy of memory CD8+ T cell subsets. In addition to the priming of naive T cells, there is some plasticity of antigen-experienced effector and memory T cell subsets to generate Trm precursors. Local inflammation, antigen presentation, and cytokines drive Trm differentiation. It is of prime interest how specific dendritic cell subsets modulate priming and differentiation of Trm cells, as well as their reactivation within tissues. Research on how we can manipulate generation of memory T cells subsets is key for improved vaccination strategies.

OX40 Stimulation Enhances Protective Immune Responses Induced After Vaccination With Attenuated Malaria Parasites.

Protection against a malaria infection can be achieved by immunization with live-attenuated Plasmodium sporozoites and while the precise mechanisms of protection remain unknown, T cell responses are thought to be critical in the elimination of infected liver cells. In cancer immunotherapies, agonistic antibodies that target T cell surface proteins, such as CD27, OX40 (CD134), and 4-1BB (CD137), have been used to enhance T cell function by increasing co-stimulation. In this study, we have analyzed the effect of agonistic OX40 monoclonal antibody treatment on protective immunity induced in mice immunized with genetically attenuated parasites (GAPs). OX40 stimulation enhanced protective immunity after vaccination as shown by an increase in the number of protected mice and delay to blood-stage infection after challenge with wild-type sporozoites. Consistent with the enhanced protective immunity enforced OX40 stimulation resulted in an increased expansion of antigen-experienced effector (CD11ahiCD44hi) CD8+ and CD4+ T cells in the liver and spleen and also increased IFN-γ and TNF producing CD4+ T cells in the liver and spleen. In addition, GAP immunization plus α-OX40 treatment significantly increased sporozoite-specific IgG responses. Thus, we demonstrate that targeting T cell costimulatory receptors can improve sporozoite-based vaccine efficacy.

Fast and easy immunomagnetic isolation of untouched human naïve T cells in less than 15 minutes

Abstract Peripheral blood circulating T cells can be subdivided into either antigen experienced effector and memory T cells or naïve T cells that have not yet encountered their cognate antigen. Naïve T cells are valuable tools when studying mechanisms of T cell activation and are required for foundational research into infectious diseases, cancer and transplantation. We describe here a simple immunomagnetic cell isolation protocol for the isolation of untouched human naïve T cells from fresh or previously frozen PBMC or leukapheresis samples. The column-free, negative selection procedure involves labelling and removing unwanted cells using bispecific antibody complexes that crosslink cell surface antigens to magnetic particles. The labelling cocktail is composed of antibodies that target non-T cells, memory T cells, and an optional cocktail for depleting gamma delta T cells. Briefly, the procedure involves a five minute incubation with the antibody cocktail followed by the addition of magnetic particles and two three minute magnetic separations in a hand-held EasySep™ magnet. Following the second magnetic separation, the untouched naïve T cells are simply poured off into a new tube and are ready for use. We define naïve T cells phenotypically as CD3+CD45RA+CD45RO-CD197+. Starting from fresh PBMC, we were able to obtain purities of 96.1 ± 2.3% (mean ± SD, n=14) and recoveries of 62.6% ± 24.5% (mean ± SD, n=14). Additionally, isolated naïve T cells are functional and respond by upregulating the expression of CD25 and CD69 upon stimulation. Our EasySep™ Human Naïve Pan T Cell Isolation Kit offers a fast and easy isolation method for naïve T cells that is suitable for downstream applications such as flow cytometry, cell culture or DNA/RNA extraction.

Intravital Microscopy Analysis of Hepatic T Cell Dynamics.

T cells play critical roles in controlling hepatotropic viral infections and liver tumors. The protective capacity of these cells is mediated by antigen-experienced effector cells and depends on their ability to migrate to and traffic within the liver, recognize pathogen- or tumor-derived antigens, get activated and deploy effector functions.While some of the rules that characterize T cell behavior in the healthy and cancerous antigen-expressing liver have been characterized at the population level, we have only limited knowledge of the precise dynamics of T cell interactions with different kinds of liver cells at the single-cell level. Here, we describe in detail an intravital microscopy technique that allows the analysis of T cell dynamic behavior in the liver of anesthetized mice at high spatial and temporal resolution. A detailed understanding of the spatiotemporal dynamics of T cells within the liver is important for the rational design of targeted immunotherapeutic approaches for chronic liver infections and tumors.

Abstract DDT01-02: Unleashing anti-tumor immunity through anti-OX40 monotherapy and in combination with anti-PD-L1

Abstract Cancer immunotherapy has the potential to induce durable responses through the generation of tumor-specific T cell memory. In addition to cognate antigen recognition, T cells require costimulation via stimulatory receptors for optimal memory T cell development and the establishment of anti-tumor immunity. OX40 is a costimulatory molecule that is expressed on activated effector and regulatory T cells. Agonistic antibodies against OX40 are predicted to counteract the immunosuppressive tumor microenvironment and promote T cell-dependent, anti-tumor immunity via two mechanisms: (1) binding to OX40 on antigen-experienced effector T cells increases their proliferation and cytokine production and (2) binding to OX40 on activated regulatory T cell inhibits their suppressive function, which in turn enhances the T cell based immune response. MOXR0916 is a humanized monoclonal antibody that binds to the human OX40 costimulatory receptor in an agonistic fashion. Binding of MOXR0916 to OX40 on activated human T cells in vitro resulted in the costimulation of effector T cell proliferation and IFN-g production, whereas binding to regulatory T cells inhibited their suppressive function. Due to sequence divergence between human and mouse OX40, a murine agonist antibody was employed to assess anti-tumor efficacy and T cell dynamics in murine syngeneic tumor models. In preclinical tumor models, anti-mouse OX40 administration induced a spectrum of anti-tumor activity, including durable responses. Animals with a complete response to anti-OX40 treatment were resistant to tumor rechallenge, indicating generation of tumor-specific memory. Tumor regression in anti-OX40 sensitive tumor models was associated with increased intratumoral expression of IFN-g, granzymes, and perforin at baseline, suggesting that anti-OX40 treatment augments latent immune responses to the tumor. Administration of anti-OX40 in several tumor models results in an increase in intratumoral CD8+ T cells and a decrease in regulatory T cells. Both anti-tumor efficacy and pharmacodynamic modulation of effector and regulatory T cells required antibody crosslinking. Similarly, anti-human OX40 MOXR0916 required antibody crosslinking to costimulate effector T cells. Treatment of agonistic anti-OX40 antibodies was capable of enhancing tumor immunity despite the activity of multiple inhibitory pathways including the PD-1- PD-L1 axis. In preclinical tumor models, the combination of anti-OX40 and a blocking antibody to the inhibitory receptor PD-L1 led to increased tumor growth inhibition and increased number of complete responses compared to either agent alone. This combination activity was associated with an increase in the expression of IFN-g associated genes and activated CD8+ T cells in the tumor. Together, these studies demonstrate that anti-OX40, both as a single agent and in combination with anti-PD-L1 can induce robust immune responses in animal tumor models. Citation Format: Jeong M. Kim. Unleashing anti-tumor immunity through anti-OX40 monotherapy and in combination with anti-PD-L1. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr DDT01-02. doi:10.1158/1538-7445.AM2015-DDT01-02

Spatiotemporal dynamics of effector CD8+ T cell responses within the liver.

CD8(+) T cells play a critical role in controlling hepatotropic viral infections, such as those caused by hepatitis B and hepatitis C viruses. The capacity of these cells to protect against such pathogens is mediated by antigen-experienced effector cells and relies on their ability to home to the liver, recognize pathogen-derived antigens, and deploy effector functions. Here, we review how dynamic imaging of hepatic effector CD8(+) T cell migration and function in mouse models of hepatitis B virus pathogenesis has recently revealed a unique and novel mode of adaptive immune surveillance. Circulating effector CD8(+) T cells initially arrest within liver sinusoids by docking onto adherent platelets and then actively crawl along the liver vasculature, probing hepatocytes for the presence of antigens by extending protrusions through the fenestrated sinusoidal endothelial cells. Hepatocellular antigen recognition and effector functions occur while CD8(+) T cells are still confined to the intravascular space and are inhibited by the pathologic processes that characterize liver fibrosis. A detailed understanding of the spatiotemporal dynamics of effector CD8(+) T cells within the liver is important for the rational design of targeted immunotherapeutic approaches for chronic liver infections.

A different view on immunity: spatial mapping of human T cells over a lifetime.

A different view on immunity: spatial mapping of human T cells over a lifetime.

Epigenetic modification of the PD-1 (Pdcd1) promoter in effector CD4(+) T cells tolerized by peptide immunotherapy.

Clinically effective antigen-based immunotherapy must silence antigen-experienced effector T cells (Teff) driving ongoing immune pathology. Using CD4(+) autoimmune Teff cells, we demonstrate that peptide immunotherapy (PIT) is strictly dependent upon sustained T cell expression of the co-inhibitory molecule PD-1. We found high levels of 5-hydroxymethylcytosine (5hmC) at the PD-1 (Pdcd1) promoter of non-tolerant T cells. 5hmC was lost in response to PIT, with DNA hypomethylation of the promoter. We identified dynamic changes in expression of the genes encoding the Ten-Eleven-Translocation (TET) proteins that are associated with the oxidative conversion 5-methylcytosine and 5hmC, during cytosine demethylation. We describe a model whereby promoter demethylation requires the co-incident expression of permissive histone modifications at the Pdcd1 promoter together with TET availability. This combination was only seen in tolerant Teff cells following PIT, but not in Teff that transiently express PD-1. Epigenetic changes at the Pdcd1 locus therefore determine the tolerizing potential of TCR-ligation.

Anti-tumor efficacy and biomarker evaluation of agonistic anti-OX40 antibodies in preclinical models

Meeting abstracts OX40, a TNFRSF member, is a co-stimulatory molecule expressed on antigen experienced effector T (Teff) and regulatory T (Treg) cells, including infiltrating cells in mouse and human tumors. Activation of OX40 by agonistic antibodies is hypothesized to promote anti-tumor immunity

Anti-tumor efficacy and biomarker evaluation of agonistic anti-OX40 antibodies in preclinical models

Meeting abstracts OX40, a TNFRSF member, is a co-stimulatory molecule expressed on antigen experienced effector T (Teff) and regulatory T (Treg) cells, including infiltrating cells in mouse and human tumors. Activation of OX40 by agonistic antibodies is hypothesized to promote anti-tumor immunity

Hepatic effector CD8(+) T-cell dynamics.

CD8(+) T cells play a critical role in hepatitis B virus (HBV) pathogenesis. During acute, self-limited infections, these cells are instrumental to viral clearance; in chronic settings, they sustain repetitive cycles of hepatocellular necrosis that promote hepatocellular carcinoma development. Both CD8(+) T-cell defensive and destructive functions are mediated by antigen-experienced effector cells and depend on the ability of these cells to migrate to the liver, recognize hepatocellular antigens and perform effector functions. Understanding the signals that modulate the spatiotemporal dynamics of CD8(+) T cells in the liver, particularly in the context of antigen recognition, is therefore critical to gaining insight into the pathogenesis of acute and chronic HBV infection. Here, we highlight recent data on how effector CD8(+) T cells traffic within the liver, and we discuss the potential for novel imaging techniques to shed light on this important aspect of HBV pathogenesis.

Pancreatic ductal adenocarcinoma contains an effector and regulatory immune cell infiltrate that is altered by multimodal neoadjuvant treatment.

ObjectiveThe immune response to pancreatic ductal adenocarcinoma (PDA) may play a role in defining its uniquely aggressive biology; therefore, we sought to clearly define the adaptive immune infiltrate in PDA.DesignWe used immunohistochemistry and flow cytometry to characterize the immune infiltrate in human PDA and compared our findings to the patients’ peripheral blood.ResultsIn contrast to the myeloid cell predominant infiltrate seen in murine models, T cells comprised the majority of the hematopoietic cell component of the tumor stroma in human PDA. Most intratumoral CD8+ T cells exhibited an antigen-experienced effector memory cell phenotype and were capable of producing IFN-γ. CD4+ regulatory T cells (Treg) and IL-17 producing T helper cells were significantly more prevalent in tumor than in blood. Consistent with the association with reduced survival in previous studies, we observed higher frequencies of both myeloid cells and Treg in poorly differentiated tumors. The majority of intratumoral T cells expressed the co-inhibitory receptor programmed death-1 (PD-1), suggesting one potential mechanism through which PDA may evade antitumor immunity. Successful multimodal neoadjuvant therapy altered the immunoregulatory balance and was associated with reduced infiltration of both myeloid cells and Treg.ConclusionOur data show that human PDA contains a complex mixture of inflammatory and regulatory immune cells, and that neoadjuvant therapy attenuates the infiltration of intratumoral cells associated with immunosuppression and worsened survival.

PTPN2 attenuates T-cell lymphopenia-induced proliferation

When the peripheral T-cell pool is depleted, T cells undergo homoeostatic expansion. This expansion is reliant on the recognition of self-antigens and/or cytokines, in particular interleukin-7. The T cell-intrinsic mechanisms that prevent excessive homoeostatic T-cell responses and consequent overt autoreactivity remain poorly defined. Here we show that protein tyrosine phosphatase N2 (PTPN2) is elevated in naive T cells leaving the thymus to restrict homoeostatic T-cell proliferation and prevent excess responses to self-antigens in the periphery. PTPN2-deficient CD8(+) T cells undergo rapid lymphopenia-induced proliferation (LIP) when transferred into lymphopenic hosts and acquire the characteristics of antigen-experienced effector T cells. The enhanced LIP is attributed to elevated T-cell receptor-dependent, but not interleukin-7-dependent responses, results in a skewed T-cell receptor repertoire and the development of autoimmunity. Our results identify a major mechanism by which homoeostatic T-cell responses are tuned to prevent the development of autoimmune and inflammatory disorders.

Short-Lived Effector CD8 T Cells Induced by Genetically Attenuated Malaria Parasite Vaccination Express CD11c

Vaccination with a single dose of genetically attenuated malaria parasites can induce sterile protection against sporozoite challenge in the rodent Plasmodium yoelii model. Protection is dependent on CD8(+) T cells, involves perforin and gamma interferon (IFN-γ), and is correlated with the expansion of effector memory CD8(+) T cells in the liver. Here, we have further characterized vaccine-induced changes in the CD8(+) T cell phenotype and demonstrated significant upregulation of CD11c on CD3(+) CD8b(+) T cells in the liver, spleen, and peripheral blood. CD11c(+) CD8(+) T cells are predominantly CD11a(hi) CD44(hi) CD62L(-), indicative of antigen-experienced effector cells. Following in vitro restimulation with malaria-infected hepatocytes, CD11c(+) CD8(+) T cells expressed inflammatory cytokines and cytotoxicity markers, including IFN-γ, tumor necrosis factor alpha (TNF-α), interleukin-2 (IL-2), perforin, and CD107a. CD11c(-) CD8(+) T cells, on the other hand, expressed negligible amounts of all inflammatory cytokines and cytotoxicity markers tested, indicating that CD11c marks multifunctional effector CD8(+) T cells. Coculture of CD11c(+), but not CD11c(-), CD8(+) T cells with sporozoite-infected primary hepatocytes significantly inhibited liver-stage parasite development. Tetramer staining for the immunodominant circumsporozoite protein (CSP)-specific CD8(+) T cell epitope demonstrated that approximately two-thirds of CSP-specific cells expressed CD11c at the peak of the CD11c(+) CD8(+) T cell response, but CD11c expression was lost as the CD8(+) T cells entered the memory phase. Further analyses showed that CD11c(+) CD8(+) T cells are primarily KLRG1(+) CD127(-) terminal effectors, whereas all KLRG1(-) CD127(+) memory precursor effector cells are CD11c(-) CD8(+) T cells. Together, these results suggest that CD11c marks a subset of highly inflammatory, short-lived, antigen-specific effector cells, which may play an important role in eliminating infected hepatocytes.