Towards targeting the breast cancer immune microenvironment

The tumour immune microenvironment is shaped by the crosstalk between cancer cells, immune cells, fibroblasts, endothelial cells and other stromal components. Although the immune tumour microenvironment (TME) serves as a source of therapeutic targets, it is also considered a friend or foe to tumour-directed therapies. This is readily illustrated by the importance of T cells in triple-negative breast cancer (TNBC), culminating in the advent of immune checkpoint therapy in combination with cytotoxic chemotherapy as standard of care for both early and advanced-stage TNBC, as well as recent promising signs of efficacy in a subset of hormone receptor-positive disease. In this Review, we discuss the various components of the immune TME in breast cancer and therapies that target or impact the immune TME, as well as the complexity of host physiology.

The TCR assigns naive T cells to a preferred lymph node

Naive T cells recirculate between the spleen and lymph nodes where they mount immune responses when meeting dendritic cells presenting foreign antigen. As this may happen anywhere, naive T cells ought to visit all lymph nodes. Here, deep sequencing almost-complete TCR repertoires led to a comparison of different lymph nodes within and between individual mice. We find strong evidence for a deterministic CD4/CD8 lineage choice and a consistent spatial structure. Specifically, some T cells show a preference for one or multiple lymph nodes, suggesting that their TCR interacts with locally presented (self-)peptides. These findings are mirrored in TCR-transgenic mice showing localized CD69 expression, retention, and cell division. Thus, naive T cells intermittently sense antigenically dissimilar niches, which is expected to affect their homeostatic competition.

Tissue-resident memory T cells in immunotherapy and immune-related adverse events by immune checkpoint inhibitor

Tissue-resident memory T cells (TRM) are a specialized subset of T cells that reside in tissues and provide long-term protective immunity against pathogens that enter the body through that specific tissue. TRM cells have specific phenotype and reside preferentially in barrier tissues. Recent studies have revealed that TRM cells are the main target of immune checkpoint inhibitor immunotherapy since their role in cancer immunosurveillance. Furthermore, TRM cells also play a crucial part in pathogenesis of immune-related adverse events (irAEs). Here, we provide a concise review of biological characteristics of TRM cells, and the major advances and recent findings regarding their involvement in immune checkpoint inhibitor immunotherapy and the corresponding irAEs.

The potential role of CD8+ cytotoxic T lymphocytes and one branch connected with tissue-resident memory in non-luminal breast cancer

Advances in understanding the pathological mechanisms of breast cancer have resulted in the emergence of novel therapeutic strategies. However, triple-negative breast cancer (TNBC), a molecular subtype of breast cancer with a poor prognosis, lacks classical and general therapeutic targets, hindering the clinical application of several therapies to breast cancer. As insights into the unique immunity and molecular mechanisms of TNBC have become more extensive, immunotherapy has gradually become a valuable complementary approach to classical radiotherapy and chemotherapy. CD8+ cells are significant actors in the tumor immunity cycle; thus, research on TNBC immunotherapy is increasingly focused in this direction. Recently, CD8+ tissue-resident memory (TRM) cells, a subpopulation of CD8+ cells, have been explored in relation to breast cancer and found to seemingly play an undeniably important role in tumor surveillance and lymphocytic infiltration. In this review, we summarize the recent advances in the mechanisms and relative targets of CD8+ T cells, and discuss the features and potential applications of CD8+ TRM cells in non-luminal breast cancer immunotherapy.

Bacterial vaginosis-driven changes in vaginal T cell phenotypes and their implications for HIV susceptibility

Bacterial vaginosis (BV) is a dysbiosis of the vaginal microbiome that is prevalent in reproductive-age women worldwide. Adverse outcomes associated with BV include an increased risk of sexually acquired Human Immunodeficiency Virus (HIV), yet the immunological mechanisms underlying this association are not well understood. To investigate BV driven changes to cervicovaginal tract (CVT) and circulating T cell phenotypes, participants with or without BV provided vaginal tract (VT) and ectocervical (CX) tissue biopsies and peripheral blood mononuclear cells (PBMC). Immunofluorescence analysis of genital mucosal tissues revealed a reduced density of CD3+CD4+CCR5+ cells in the VT lamina propria of individuals with compared to those without BV (median 243.8 cells/mm2 BV- vs 106.9 cells/mm2 BV+, p=0.043). High-parameter flow cytometry of VT biopsies revealed an increased frequency in individuals with compared to those without BV of dysfunctional CD39+ conventional CD4+ T cells (Tconv) (median frequency 15% BV- vs 30% BV+, padj=0.0331) and tissue-resident CD69+CD103+ Tconv (median frequency 24% BV- vs 38% BV+, padj=0.0061), previously reported to be implicated in HIV acquisition and replication. Our data suggests that BV elicits diverse and complex VT T cell alterations and expands on potential immunological mechanisms that may promote adverse outcomes including HIV susceptibility.

The protective roles of integrin α4β7 and Amphiregulin-expressing innate lymphoid cells in lupus nephritis

Type 2 innate lymphoid cells (ILC2s) have emerged as key regulators of the immune response in renal inflammatory diseases such as lupus nephritis. However, the mechanisms underlying ILC2 adhesion and migration in the kidney remain poorly understood. Here, we revealed the critical role of integrin α4β7 in mediating renal ILC2 adhesion and function. We found that integrin α4β7 enables the retention of ILC2s in the kidney by binding to VCAM-1, E-cadherin, or fibronectin on structural cells. Moreover, integrin α4β7 knockdown reduced the production of the reparative cytokine amphiregulin (Areg) by ILC2s. In lupus nephritis, TLR7/9 signaling within the kidney microenvironment downregulates integrin α4β7 expression, leading to decreased Areg production and promoting the egress of ILC2s. Notably, IL-33 treatment upregulated integrin α4β7 and Areg expression in ILC2s, thereby enhancing survival and reducing inflammation in lupus nephritis. Together, these findings highlight the potential of targeting ILC2 adhesion as a therapeutic strategy for autoimmune kidney diseases.

Inflammatory memory in psoriasis: From remission to recurrence

The routine use of targeted systemic immunomodulatory therapies has transformed outcomes for people with severe psoriasis, with skin clearance (clinical remission) rates up to 60% at 1 year of biologic treatment. However, psoriasis may recur following drug withdrawal, and as a result, patients tend to continue receiving costly treatment indefinitely. Here, we review research into the "inflammatory memory" in resolved psoriasis skin and the potential mechanisms leading to psoriasis recurrence following drug withdrawal. Research has implicated immune cells such as tissue resident memory T cells, Langerhans cells, and dermal dendritic cells, and there is growing interest in keratinocytes and fibroblasts. A better understanding of the interactions between these cell populations, enabled by single cell technologies, will help to elucidate the events underpinning the shift from remission to recurrence. This may inform the development of personalized strategies for sustaining remission while reducing long-term drug burden.

IL-10 suppresses T cell expansion while promoting tissue-resident memory cell formation during SARS-CoV-2 infection in rhesus macaques

The regulation of inflammatory responses and pulmonary disease during SARS-CoV-2 infection is incompletely understood. Here we examine the roles of the prototypic pro- and anti-inflammatory cytokines IFNγ and IL-10 using the rhesus macaque model of mild COVID-19. We find that IFNγ drives the development of 18fluorodeoxyglucose (FDG)-avid lesions in the lungs as measured by PET/CT imaging but is not required for suppression of viral replication. In contrast, IL-10 limits the duration of acute pulmonary lesions, serum markers of inflammation and the magnitude of virus-specific T cell expansion but does not impair viral clearance. We also show that IL-10 induces the subsequent differentiation of virus-specific effector T cells into CD69+CD103+ tissue resident memory cells (Trm) in the airways and maintains Trm cells in nasal mucosal surfaces, highlighting an unexpected role for IL-10 in promoting airway memory T cells during SARS-CoV-2 infection of macaques.

Local Power: The Role of Tissue-Resident Immunity in Human Genital Herpes Simplex Virus Reactivation

From established latency, human herpes virus type 2 (HSV-2) frequently reactivates into the genital tract, resulting in symptomatic ulcers or subclinical shedding. Tissue-resident memory (TRM) CD8+ T cells that accumulate and persist in the genital skin at the local site of recrudescence are the "first responders" to viral reactivation, performing immunosurveillance and containment and aborting the ability of the virus to induce clinical lesions. This review describes the unique spatiotemporal characteristics, transcriptional signatures, and noncatalytic effector functions of TRM CD8+ T cells in the tissue context of human HSV-2 infection. We highlight recent insights into the intricate overlaps between intrinsic resistance, innate defense, and adaptive immunity in the tissue microenvironment and discuss how rapid virus-host dynamics at the skin and mucosal level influence clinical outcomes of genital herpes diseases.

Filling two needs with one deed: a combinatory mucosal vaccine against influenza A virus and respiratory syncytial virus

Influenza A Virus (IAV) and Respiratory Syncytial Virus (RSV) are both responsible for millions of severe respiratory tract infections every year worldwide. Effective vaccines able to prevent transmission and severe disease, are important measures to reduce the burden for the global health system. Despite the strong systemic immune responses induced upon current parental immunizations, this vaccination strategy fails to promote a robust mucosal immune response. Here, we investigated the immunogenicity and efficacy of a mucosal adenoviral vector vaccine to tackle both pathogens simultaneously at their entry site. For this purpose, BALB/c mice were immunized intranasally with adenoviral vectors (Ad) encoding the influenza-derived proteins, hemagglutinin (HA) and nucleoprotein (NP), in combination with an Ad encoding for the RSV fusion (F) protein. The mucosal combinatory vaccine induced neutralizing antibodies as well as local IgA responses against both viruses. Moreover, the vaccine elicited pulmonary CD8+ and CD4+ tissue resident memory T cells (TRM) against the immunodominant epitopes of RSV-F and IAV-NP. Furthermore, the addition of Ad-TGFβ or Ad-CCL17 as mucosal adjuvant enhanced the formation of functional CD8+ TRM responses against the conserved IAV-NP. Consequently, the combinatory vaccine not only provided protection against subsequent infections with RSV, but also against heterosubtypic challenges with pH1N1 or H3N2 strains. In conclusion, we present here a potent combinatory vaccine for mucosal applications, which provides protection against two of the most relevant respiratory viruses.

Islet-Resident Memory T Cells Orchestrate the Immunopathogenesis of Type 1 Diabetes through the FABP4-CXCL10 Axis

Type 1 diabetes (T1D) is a chronic disease characterized by self-destruction of insulin-producing pancreatic β cells by cytotoxic T cell activity. However, the pathogenic mechanism of T cell infiltration remains obscure. Recently, tissue-resident memory T (TRM) cells have been shown to contribute to cytotoxic T cell recruitment. TRM cells are found present in human pancreas and are suggested to modulate immune homeostasis. Here, the role of TRM cells in the development of T1D is investigated. The presence of TRM cells in pancreatic islets is observed in non-obese diabetic (NOD) mice before T1D onset. Mechanistically, elevated fatty acid-binding protein 4 (FABP4) potentiates the survival and alarming function of TRM cells by promoting fatty acid utilization and C-X-C motif chemokine 10 (CXCL10) secretion, respectively. In NOD mice, genetic deletion of FABP4 or depletion of TRM cells using CD69 neutralizing antibodies resulted in a similar reduction of pancreatic cytotoxic T cell recruitment, a delay in diabetic incidence, and a suppression of CXCL10 production. Thus, targeting FABP4 may represent a promising therapeutic strategy for T1D.

Innate phase production of IFN-γ by memory and effector T cells expressing early activation marker CD69 during infection with Cryptococcus deneoformans in the lungs

Cryptococcus deneoformans is a yeast-type fungus that causes fatal meningoencephalitis in immunocompromised patients and evades phagocytic cell elimination through an escape mechanism. Memory T (Tm) cells play a central role in preventing the reactivation of this fungal pathogen. Among these cells, tissue-resident memory T (TRM) cells quickly respond to locally invaded pathogens. This study analyzes the kinetics of effector T (Teff) cells and Tm cells in the lungs after cryptococcal infection. Emphasis is placed on the kinetics and cytokine expression of TRM cells in the early phase of infection. CD4+ Tm cells exhibited a rapid increase by day 3, peaked at day 7, and then either maintained their levels or exhibited a slight decrease until day 56. In contrast, CD8+ Tm cells reached their peak on day 3 and thereafter decreased up to day 56 post-infection. These Tm cells were predominantly composed of CD69+ TRM cells and CD69+ CD103+ TRM cells. Disruption of the CARD9 gene resulted in reduced accumulation of these TRM cells and diminished interferon (IFN) -γ expression in TRM cells. TRM cells were derived from T cells with T cell receptors non-specific to ovalbumin in OT-II mice during cryptococcal infection. In addition, TRM cells exhibited varied behavior in different tissues. These results underscore the importance of T cells, which produce IFN-γ in the lungs during the early stage of infection, in providing early protection against cryptococcal infection through CARD9 signaling.

CD69 Is Indispensable for Development of Functional Local Immune Memory in Murine Contact Hypersensitivity

Local immune memory develops at the site of antigen exposure and facilitates a rapid and strong local adaptive defense upon re-exposure. Resident memory T (TRM) cells play a role in local immune memory, and their cell-surface molecules CD69 and CD103 promote their tissue residency. However, the contribution of these molecules to skin immune memory remains unclear. In this study, by inducing contact hypersensitivity (CHS) in CD69KO (CD69-deficient) and CD103-deficient mice, where different degrees of TRM cell contribution are observed by repeated challenges on the right ear and a single challenge on the left ear, we found that the deficiency of CD69 but not CD103 leads to impaired CHS upon repeated antigen challenges, even although TRM cells-like CD8 T cells developed at the challenged site of CD69KO. CHS responses in both ears were diminished in CD69KO by FTY720 or CD8 neutralization, suggesting that CHS in CD69KO is ascribed to circulating CD8 T cells and that the developed TRM cell-like CD8 T cells do not behave as TRM cells. The infiltration of macrophages was reduced in the rechallenged site of CD69KO, along with the downregulation of Cxcl1 and Cxcl2. Thus, CD69 is considered essential for an effective recall response, involving the development of functional TRM cells and the recruitment of macrophages.

Lymphatic vessels in the age of cancer immunotherapy

Lymphatic transport maintains homeostatic health and is necessary for immune surveillance, and yet lymphatic growth is often associated with solid tumour development and dissemination. Although tumour-associated lymphatic remodelling and growth were initially presumed to simply expand a passive route for regional metastasis, emerging research puts lymphatic vessels and their active transport at the interface of metastasis, tumour-associated inflammation and systemic immune surveillance. Here, we discuss active mechanisms through which lymphatic vessels shape their transport function to influence peripheral tissue immunity and the current understanding of how tumour-associated lymphatic vessels may both augment and disrupt antitumour immune surveillance. We end by looking forward to emerging areas of interest in the field of cancer immunotherapy in which lymphatic vessels and their transport function are likely key players: the formation of tertiary lymphoid structures, immune surveillance in the central nervous system, the microbiome, obesity and ageing. The lessons learnt support a working framework that defines the lymphatic system as a key determinant of both local and systemic inflammatory networks and thereby a crucial player in the response to cancer immunotherapy.

Apoptosis, a Metabolic "Head-to-Head" between Tumor and T Cells: Implications for Immunotherapy

Induction of apoptosis represents a promising therapeutic approach to drive tumor cells to death. However, this poses challenges due to the intricate nature of cancer biology and the mechanisms employed by cancer cells to survive and escape immune surveillance. Furthermore, molecules released from apoptotic cells and phagocytes in the tumor microenvironment (TME) can facilitate cancer progression and immune evasion. Apoptosis is also a pivotal mechanism in modulating the strength and duration of anti-tumor T-cell responses. Combined strategies including molecular targeting of apoptosis, promoting immunogenic cell death, modulating immunosuppressive cells, and affecting energy pathways can potentially overcome resistance and enhance therapeutic outcomes. Thus, an effective approach for targeting apoptosis within the TME should delicately balance the selective induction of apoptosis in tumor cells, while safeguarding survival, metabolic changes, and functionality of T cells targeting crucial molecular pathways involved in T-cell apoptosis regulation. Enhancing the persistence and effectiveness of T cells may bolster a more resilient and enduring anti-tumor immune response, ultimately advancing therapeutic outcomes in cancer treatment. This review delves into the pivotal topics of this multifaceted issue and suggests drugs and druggable targets for possible combined therapies.

Crosstalk between CD8+ T cells and mesenchymal stromal cells in intestine homeostasis and immunity

The intestine represents the most complex cellular network in the whole body. It is constantly faced with multiple types of immunostimulatory agents encompassing from food antigen, gut microbiome, metabolic waste products, and dead cell debris. Within the intestine, most T cells are found in three primary compartments: the organized gut-associated lymphoid tissue, the lamina propria, and the epithelium. The well-orchestrated epithelial-immune-microbial interaction is critically important for the precise immune response. The main role of intestinal mesenchymal stromal cells is to support a structural framework within the gut wall. However, recent evidence from stromal cell studies indicates that they also possess significant immunomodulatory functions, such as maintaining intestinal tolerance via the expression of PDL1/2 and MHC-II molecules, and promoting the development of CD103+ dendritic cells, and IgA+ plasma cells, thereby enhancing intestinal homeostasis. In this review, we will summarize the current understanding of CD8+ T cells and stromal cells alongside the intestinal tract and discuss the reciprocal interactions between T subsets and mesenchymal stromal cell populations. We will focus on how the tissue residency, migration, and function of CD8+ T cells could be potentially regulated by mesenchymal stromal cell populations and explore the molecular mediators, such as TGF-β, IL-33, and MHC-II molecules that might influence these processes. Finally, we discuss the potential pathophysiological impact of such interaction in intestine hemostasis as well as diseases of inflammation, infection, and malignancies.

Tissue-resident memory T cells: decoding intra-organ diversity with a gut perspective

Tissue-resident memory T cells (TRM) serve as the frontline of host defense, playing a critical role in protection against invading pathogens. This emphasizes their role in providing rapid on-site immune responses across various organs. The physiological significance of TRM is not just confined to infection control; accumulating evidence has revealed that TRM also determine the pathology of diseases such as autoimmune disorders, inflammatory bowel disease, and cancer. Intensive studies on the origin, mechanisms of formation and maintenance, and physiological significance of TRM have elucidated the transcriptional and functional diversity of these cells, which are often affected by local cues associated with their presence. These were further confirmed by the recent remarkable advancements of next-generation sequencing and single-cell technologies, which allow the transcriptional and phenotypic characterization of each TRM subset induced in different microenvironments. This review first overviews the current knowledge of the cell fate, molecular features, transcriptional and metabolic regulation, and biological importance of TRM in health and disease. Finally, this article presents a variety of recent studies on disease-associated TRM, particularly focusing and elaborating on the TRM in the gut, which constitute the largest and most intricate immune network in the body, and their pathological relevance to gut inflammation in humans.

Gut-tropic T cells and extra-intestinal autoimmune diseases

Gut-tropic T cells primarily originate from gut-associated lymphoid tissue (GALT), and gut-tropic integrins mediate the trafficking of the T cells to the gastrointestinal tract, where their interplay with local hormones dictates the residence of the immune cells in both normal and compromised gastrointestinal tissues. Targeting gut-tropic integrins is an effective therapy for inflammatory bowel disease (IBD). Gut-tropic T cells are further capable of entering the peripheral circulatory system and relocating to multiple organs. There is mounting evidence indicating a correlation between gut-tropic T cells and extra-intestinal autoimmune disorders. This review aims to systematically discuss the origin, migration, and residence of gut-tropic T cells and their association with extra-intestinal autoimmune-related diseases. These discoveries are expected to offer new understandings into the development of a range of autoimmune disorders, as well as innovative approaches for preventing and treating the diseases.

Long-term activation of anti-tumor immunity in pancreatic cancer by a p53-expressing telomerase-specific oncolytic adenovirus

BACKGROUND

Pancreatic cancer is an aggressive, immunologically "cold" tumor. Oncolytic virotherapy is a promising treatment to overcome this problem. We developed a telomerase-specific oncolytic adenovirus armed with p53 gene (OBP-702).

METHODS

We investigated the efficacy of OBP-702 for pancreatic cancer, focusing on its long-term effects via long-lived memory CD8 + T cells including tissue-resident memory T cells (TRMs) and effector memory T cells (TEMs) differentiated from effector memory precursor cells (TEMps).

RESULTS

First, in vitro, OBP-702 significantly induced adenosine triphosphate (ATP), which is important for memory T cell establishment. Next, in vivo, OBP-702 local treatment to murine pancreatic PAN02 tumors increased TEMps via ATP induction from tumors and IL-15Rα induction from macrophages, leading to TRM and TEM induction. Activation of these memory T cells by OBP-702 was also maintained in combination with gemcitabine+nab-paclitaxel (GN) in a PAN02 bilateral tumor model, and GN + OBP-702 showed significant anti-tumor effects and increased TRMs in OBP-702-uninjected tumors. Finally, in a neoadjuvant model, in which PAN02 cells were re-inoculated after resection of treated-PAN02 tumors, GN + OBP-702 provided long-term anti-tumor effects even after tumor resection.

CONCLUSION

OBP-702 can be a long-term immunostimulant with sustained anti-tumor effects on immunologically cold pancreatic cancer.

Resident memory T cells in nonlesional skin and healed lesions of patients with chronic inflammatory diseases: Appearances can be deceptive

Tissue-resident memory T (TRM) cells serve as a first line of defense in peripheral tissues to protect the organism against foreign pathogens. However, autoreactive TRM cells are increasingly implicated in autoimmunity, as evidenced in chronic autoimmune and inflammatory skin conditions. This highlights the need to characterize their phenotype and understand their role for the purpose of targeting them specifically without affecting local immunity. To date, the investigation of TRM cells in human skin diseases has focused mainly on lesional tissues of patients. Accumulating evidence suggests that self-reactive TRM cells are still present in clinically healed lesions of patients and play a role in disease flares, but TRM cells also populate skin that is apparently normal. This review discusses the ontogeny of TRM cells in the skin as well as recent insights regarding the presence of self-reactive TRM cells in both clinically healed skin and nonlesional skin of patients with autoimmune and inflammatory skin conditions, with a particular focus on psoriasis, atopic dermatitis, and vitiligo.

Memory T cells: promising biomarkers for evaluating protection and vaccine efficacy against leishmaniasis

Understanding the immune response to Leishmania infection and identifying biomarkers that correlate with protection are crucial for developing effective vaccines. One intriguing aspect of Leishmania infection is the persistence of parasites, even after apparent lesion healing. Various host cells, including dendritic cells, fibroblasts, and Langerhans cells, may serve as safe sites for latent infection. Memory T cells, especially tissue-resident memory T cells (TRM), play a crucial role in concomitant immunity against cutaneous Leishmania infections. These TRM cells are long-lasting and can protect against reinfection in the absence of persistent parasites. CD4+ TRM cells, in particular, have been implicated in protection against Leishmania infections. These cells are characterized by their ability to reside in the skin and rapidly respond to secondary infections by producing cytokines such as IFN-γ, which activates macrophages to kill parasites. The induction of CD4+ TRM cells has shown promise in experimental immunization, leading to protection against Leishmania challenge infections. Identifying biomarkers of protection is a critical step in vaccine development and CD4+ TRM cells hold potential as biomarkers, as their presence and functions may correlate with protection. While recent studies have shown that Leishmania-specific memory CD4+ T-cell subsets are present in individuals with a history of cutaneous leishmaniasis, further studies are needed to characterize CD4+ TRM cell populations. Overall, this review highlights the importance of memory T cells, particularly skin-resident CD4+ TRM cells, as promising targets for developing effective vaccines against leishmaniasis and as biomarkers of immune protection to assess the efficacy of candidate vaccines against human leishmaniasis.

Decoding the transcriptional heterogeneity, differentiation lineage, clinical significance in tissue-resident memory CD8 T cell of the small intestine by single-cell analysis

Resident memory T (Trm) cells which are specifically located in non-lymphoid tissues showed distinct phenotypes and functions compared to circulating memory T cells and were vital for the initiation of robust immune response within tissues. However, the heterogeneity in the transcriptional features, development pathways, and cancer response of Trm cells in the small intestine was not demonstrated. Here, we integrated scRNA-seq and scTCR-seq data pan-tissue T cells to explore the heterogeneity of Trm cells and their development pathways. Trm were enriched in tissue-specific immune response and those in the DUO specially interacted with B cells via TNF and MHC-I signatures. T cell lineage analyses demonstrated that Trm might be derived from the T_CD4/CD8 subset within the same organ or migrated from spleen and mesenteric lymph nodes. We compared the immune repertoire of Trm among organs and implied that clonotypes in both DUO and ILE were less expanded and hydrophilic TRB CDR3s were enriched in the DUO. We further demonstrated that Trm in the intestine infiltrated the colorectal cancer and several effector molecules were highly expressed. Finally, the TCGA dataset of colorectal cancer implied that the infiltration of Trm from the DUO and the ILE was beneficial for overall survival and the response to immune checkpoint blockade.

Intestinal immunological events of acute and resolved SARS-CoV-2 infection in non-human primates

SARS-CoV-2 infection has been associated with intestinal mucosal barrier damage, leading to microbial and endotoxin translocation, heightened inflammatory responses, and aggravated disease outcomes. This study aimed to investigate the immunological mechanisms associated with impaired intestinal barrier function. We conducted a comprehensive analysis of gut damage and inflammation markers and phenotypic characterization of myeloid and lymphoid populations in the ileum and colon of SARS-CoV-2-exposed macaques during both the acute and resolved infection phases. Our findings revealed a significant accumulation of terminally differentiated and activated CD4+ and CD8+ T cells, along with memory B cells, within the gastrointestinal tract up to 43 days after exposure to SARS-CoV-2. This robust infection-induced immune response was accompanied by a notable depletion of plasmacytoid dendritic cells, myeloid dendritic cells, and macrophages, particularly affecting the colon during the resolved infection phase. Additionally, we identified a population of CX3CR1Low inflammatory macrophages associated with intestinal damage during active viral replication. Elevated levels of immune activation and gut damage markers, and perturbation of macrophage homeostasis, persisted even after the resolution of the infection, suggesting potential long-term clinical sequelae. These findings enhance our understanding of gastrointestinal immune pathology following SARS-CoV-2 infection and provide valuable information for developing and testing medical countermeasures.

Signalling mechanisms driving homeostatic and inflammatory effects of interleukin-15 on tissue lymphocytes

There is an intriguing dichotomy in the function of cytokine interleukin-15-at low levels, it is required for the homeostasis of the immune system, yet when it is upregulated in response to pathogenic infections or in autoimmunity, IL-15 drives inflammation. IL-15 associates with the IL-15Rα within both myeloid and non-haematopoietic cells, where IL-15Rα trans-presents IL-15 in a membrane-bound form to neighboring cells. Alongside homeostatic maintenance of select lymphocyte populations such as NK cells and tissue-resident T cells, when upregulated, IL-15 also promotes inflammatory outcomes by driving effector function and cytotoxicity in NK cells and T cells. As chronic over-expression of IL-15 can lead to autoimmunity, IL-15 expression is tightly regulated. Thus, blocking dysregulated IL-15 and its downstream signalling pathways are avenues for immunotherapy. In this review we discuss the molecular pathways involved in IL-15 signalling and how these pathways contribute to both homeostatic and inflammatory functions in IL-15-dependent mature lymphoid populations, focusing on innate, and innate-like lymphocytes in tissues.

PD-1 and TIGIT coexpressing CD8 + CD103 + tissue-resident memory cells in endometrial cancer as potential targets for immunotherapy

BACKGROUND

Immunotherapy has shown promise in treating various cancers; however, its efficacy in endometrial cancer (EC) remains suboptimal owing to the complex dynamics of the tumour immune microenvironment. This study focuses on exploring the potential of targeting the programmed cell death protein 1 gene (PD-1) and the T cell Immunoreceptor with Ig and ITIM domains gene (TIGIT) coexpressing tissue-resident memory cells in EC.

METHODS

A comprehensive approach, utilizing RNA sequencing, single-cell RNA sequencing, mass cytometry, and flow cytometry, was employed to analyse the expression patterns of PD-1 and TIGIT in the EC tumor environment and to characterize the phenotypic properties of tumor-infiltrating lymphocytes (TILs), particularly tissue-resident memory (TRM) cells. Additionally, in vitro cell experiments were conducted to assess the functional impact of PD-1 and TIGIT blockade on T-cell activity.

RESULTS

Our analysis identified a significant co-expression of PD-1 and TIGIT in TRM cells within the EC tumor microenvironment. These TRM cells displayed an exhausted phenotype with impaired cytotoxicity, enhanced proliferative capacity, and diminished cytotoxic activity. In vitro T-cell assays showed that a dual blockade of PD-1 and TIGIT more effectively restored T-cell functionality compared to single blockade, suggesting enhanced therapeutic potential.

CONCLUSIONS

TRM cells co-expressing PD-1 and TIGIT represent potential targets for EC immunotherapy. Dual immune checkpoint blockade targeting PD-1 and TIGIT may offer an effective therapeutic strategy for EC, providing valuable insights for the development of immunotherapeutic approaches.

CD8+ Trms against malaria liver-stage: prospects and challenges

Attenuated sporozoites provide a valuable model for exploring protective immunity against the malarial liver stage, guiding the design of highly efficient vaccines to prevent malaria infection. Liver tissue-resident CD8+ T cells (CD8+ Trm cells) are considered the host front-line defense against malaria and are crucial to developing prime-trap/target strategies for pre-erythrocytic stage vaccine immunization. However, the spatiotemporal regulatory mechanism of the generation of liver CD8+ Trm cells and their responses to sporozoite challenge, as well as the protective antigens they recognize remain largely unknown. Here, we discuss the knowledge gap regarding liver CD8+ Trm cell formation and the potential strategies to identify predominant protective antigens expressed in the exoerythrocytic stage, which is essential for high-efficacy malaria subunit pre-erythrocytic vaccine designation.

CD69 is a Promising Immunotherapy and Prognosis Prediction Target in Cancer

Immunotherapy utilizing T cells that attack tumors is a promising strategy for treatment, but immune suppressive T cell subsets, such as regulatory T cell (Treg), and immune checkpoint molecules, including programmed death-1 (PD-1), can suppress the intensity of a T cell immune reaction and thereby impair tumor clearance. Cluster of differentiation 69 (CD69), known as an early leukocyte activation marker, can be used as a measure or early marker of T cell activation. In recent years, the functions of CD69 in the regulation of Treg/Th17 (T helper cell 17) differentiation and in the tissue retention of T cells have attracted considerable interest. These functions are related to the role of CD69 in immune suppression in tumor environments (TME). In this review, we first summarized current perspectives in the biological function of CD69 and demonstrated that CD69 acts as a regulator of T cell activation, differentiation, retention, and exhaustion. Then, we discussed recent advances in understanding of CD69 deficiency and anti-CD69 antibody administration and shed light on the value of targeting on CD69 for cancer immunotherapy and prognosis prediction.

Regulatory role of RGMb in lung injury promoted by the combination of carbon ion irradiation and anti-PD-1 antibody through Erk1/2 and p38 MAPK pathways

The combination of carbon ion radiotherapy and anti-PD-1 antibody represents a new approach to treating thoracic tumors. However, the lung damage caused by this combination therapy may limit its use, and the potential mechanisms for this are worthy of investigation. The objective of this research was to examine the potential involvement of repulsive guidance molecule b (RGMb) in lung damage promoted by the utilization of carbon ion irradiation combined with an anti-PD-1 antibody. The C57BL/6 mice have been randomly separated into four distinct groups: control, anti-PD-1, whole thorax carbon ion irradiation, and irradiation in combination with anti-PD-1 treatment groups (combination group). Detection of pathological changes in lung tissue using HE staining. Detection of pulmonary fibrosis by Masson staining and the hydroxyproline assay. ELISA to detect TNF-α, TGF-β, IL-6, and IL-1β expression levels within lung homogenates. The expression of RGMb, p38 MAPK, and Erk1/2 pathways was detected using a fully automated digital Western blotting system WES (ProteinSimple, USA). Flow cytometry was employed to analyze tissue-resident memory T cells (TRM) within the lung. Subsequently, the siRNA gene was employed to induce the downregulation of RGMb in mice in order to validate the involvement of RGMb in radiation-immune lung injury. The present study observed a significant increase in both inflammatory and fibrotic indicators within the mice group's lung tissue that received the combination treatment. The combination group exhibited elevated levels of TGF-β, TNF-α, IL-6, and IL-1β in lung homogenates. Anti-PD-1 antibody and carbon ion irradiation, upregulated RGMb, phospho-p38 MAPK and phospho-Erk1/2. The results obtained from the flow cytometry analysis indicated that the combination group was significantly higher in the number of clonal expansion TRMs, which were predominantly characterized by the expression of CD8+CD103+CD69-TRMs. The downregulate of RGMb via siRNA in mice resulted in a decrease in phospho-p38 MAPK and phospho-Erk1/2. The combination group exhibited a reduction in TNF-α, TGF-β, IL-6, and IL-1β in their lung tissues, and the number of CD8+CD103+CD69-TRM was significantly reduced. The combination group exhibited a significant improvement in inflammatory and fibrotic indicators within the lung tissues. Anti-PD-1 antibody and carbon ion irradiation synergistically regulate RGMb, leading to strong clonal expansion of lung TRM through the p38 MAPK and Erk1/2 pathways. The present study offers valuable insights into the treatment of lung injury due to the combined administration of carbon ion radiotherapy and anti-PD-1 antibody therapy.

Tissue-resident memory T cells exhibit phenotypically and functionally heterogeneous in human physiological and pathological nasal mucosa

Pathogens commonly enter mucosal barrier tissues and tissue-resident memory T cells (TRM) are essential for preventing mucosal lesions. However, the immunological properties of TRM cells in nasal mucosa are poorly known. In comparison with control tissues, decreasing CD103+ TRM cells were observed in Chronic rhinosinusitis with nasal polyps (CRSwNPs) and sinonasal inverted papilloma (SNIP), which presented high capability to produce effector cytokines. In CRSwNPs, we found that CD103+ TRM cells with higher cytokine and Granzyme B coexpressed high PD-1, CD103- TRM cells expressed higher IL-10. Homogenates isolated from CRSwNPs induced CD103 expression on peripheral T cells which could be inhibited by blocking TGF-β. The frequencies of CD103+ TRM cells in CRSwNPs were extremely negatively correlated with neutrophil infiltration. CD103+ TRM cells from Staphylococcus aureus positive CRSwNPs had a stronger response to SEB. Taken together, two phenotypically and functionally distinct subsets of TRM cells exist in nasal tissues and play critical roles in the progress of CRSwNPs and SNIPs.

A novel "prime and pull" strategy mediated by the combination of two dendritic cell-targeting designs induced protective lung tissue-resident memory T cells against H1N1 influenza virus challenge

Vaccination is still the most promising strategy for combating influenza virus pandemics. However, the highly variable characteristics of influenza virus make it difficult to develop antibody-based universal vaccines, until now. Lung tissue-resident memory T cells (TRM), which actively survey tissues for signs of infection and react rapidly to eliminate infected cells without the need for a systemic immune reaction, have recently drawn increasing attention towards the development of a universal influenza vaccine. We previously designed a sequential immunization strategy based on orally administered Salmonella vectored vaccine candidates. To further improve our vaccine design, in this study, we used two different dendritic cell (DC)-targeting strategies, including a single chain variable fragment (scFv) targeting the surface marker DC-CD11c and DC targeting peptide 3 (DCpep3). Oral immunization with Salmonella harboring plasmid pYL230 (S230), which displayed scFv-CD11c on the bacterial surface, induced dramatic production of spleen effector memory T cells (TEM). On the other hand, intranasal boost immunization using purified DCpep3-decorated 3M2e-ferritin nanoparticles in mice orally immunized twice with S230 (S230inDC) significantly stimulated the differentiation of lung CD11b+ DCs, increased intracellular IL-17 production in lung CD4+ T cells and elevated chemokine production in lung sections, such as CXCL13 and CXCL15, as determined by RNAseq and qRT‒PCR assays, resulting in significantly increased percentages of lung TRMs, which could provide efficient protection against influenza virus challenge. The dual DC targeting strategy, together with the sequential immunization approach described in this study, provides us with a novel "prime and pull" strategy for addressing the production of protective TRM cells in vaccine design.

Divergent molecular networks program functionally distinct CD8+ skin-resident memory T cells

Skin-resident CD8+ T cells include distinct interferon-γ-producing [tissue-resident memory T type 1 (TRM1)] and interleukin-17 (IL-17)-producing (TRM17) subsets that differentially contribute to immune responses. However, whether these populations use common mechanisms to establish tissue residence is unknown. In this work, we show that TRM1 and TRM17 cells navigate divergent trajectories to acquire tissue residency in the skin. TRM1 cells depend on a T-bet-Hobit-IL-15 axis, whereas TRM17 cells develop independently of these factors. Instead, c-Maf commands a tissue-resident program in TRM17 cells parallel to that induced by Hobit in TRM1 cells, with an ICOS-c-Maf-IL-7 axis pivotal to TRM17 cell commitment. Accordingly, by targeting this pathway, skin TRM17 cells can be ablated without compromising their TRM1 counterparts. Thus, skin-resident T cells rely on distinct molecular circuitries, which can be exploited to strategically modulate local immunity.

Resident cutaneous memory T cells: a clinical review of their role in chronic inflammatory dermatoses and potential as therapeutic targets

Resident memory T cells (T-RMs) remain in epithelial barrier tissues after antigen exposure and the initial effector phase. These T-RMs provide effective antimicrobial and anticancer immunity; however, pathogenic T-RMs have been shown to mediate various chronic inflammatory disorders in a variety of tissue types. In the skin, T-RMs are referred to as resident cutaneous memory T cells (cT-RMs). Understanding the mechanisms leading to the development and establishment of these cT-RMs populations may allow for targeted treatments that provide durable responses in chronic immune-mediated skin diseases, even after cessation. In this review, we summarize the evidence on cT-RMs as drivers of chronic inflammatory dermatoses, including psoriasis, vitiligo, atopic dermatitis, cutaneous lupus erythematosus and alopecia areata, among others. Data from in vitro, animal model and ex vivo human studies are presented, with a focus on the potential for cT-RMs to trigger acute disease flares, as well as recurrent disease, by establishing an immune 'memory' in the skin. Furthermore, the available data on the potential for existing and novel treatments to affect the development or survival of cT-RMs in the skin are synthesized. The data suggest a dynamic and rapidly growing area in the field of dermatology; however, we also discuss areas in need of greater research to allow for optimal treatment selection for long-term disease control.

Egress of resident memory T cells from tissue with neoadjuvant immunotherapy: Implications for systemic anti-tumor immunity

INTRODUCTION

Resident memory T (TRM) cells are embedded in peripheral tissue and capable of acting as sentinels that can respond quickly to repeat pathogen exposure as part of an endogenous anti-microbial immune response. Recent evidence suggests that chronic antigen exposure and other microenvironment cues may promote the development of TRM cells within solid tumors as well, and that this TRM phenotype can sequester tumor-specific T cells into tumors and out of circulation resulting in limited systemic antitumor immunity. Here, we perform a review of the published English literature and describe tissue-specific mediators of TRM cell differentiation in states of infection and malignancy with special focus on the role of TGF-β and how targeting TGF-β signaling could be used as a therapeutical approach to promote tumor systemic immunity.

DISCUSSION

The presence of TRM cells with antigen specificity to neoepitopes in tumors associates with positive clinical prognosis and greater responsiveness to immunotherapy. Recent evidence indicates that solid tumors may act as reservoirs for tumor specific TRM cells and limit their circulation - possibly resulting in impaired systemic antitumor immunity. TRM cells utilize specific mechanisms to egress from peripheral tissues into circulation and other peripheral sites, and emerging evidence indicates that immunotherapeutic approaches may initiate these processes and increase systemic antitumor immunity.

CONCLUSIONS

Reversing tumor sequestration of tumor-specific T cells prior to surgical removal or radiation of tumor may increase systemic antitumor immunity. This finding may underlie the improved recurrence free survival observed with neoadjuvant immunotherapy in clinical trials.

The involvement of circulating CD69+ CD56bright natural killer cells in weight loss before bariatric surgery: A retrospective cohort study

As the impact of the immune system on weight loss prior to bariatric surgery has never been proven, we elucidated the clinical utility of the immune system as an indicator of preoperative weight loss before bariatric surgery. We examined the relationships between preoperative weight loss and biochemical and clinical data at the initial visit in 34 obese patients. Patients were divided according to preoperative weight loss, and peripheral blood mononuclear cells were compared using flowcytometry. The Δpreoperative excess weight loss [Δpre-EWL: pre-EWL (%)/period of preoperative weight loss (days)] showed negative correlations with total and subcutaneous fat area (P = .02, r = -0.41, P = .02, r = -0.42 respectively). The Δpre-EWL and Δpreoperative total weight loss (Δpre-TWL) were negatively correlated with white blood cell count, lymphocyte count, and C-reactive protein (CRP) levels at the initial visit (Δpre-EWL; P = .02, r = -0.37, P = .01, r = -0.41, P = .008, r = -0.45, Δpre-TWL; P = .01, r = -0.40, P = .01, r = -0.42, P = .01, r = -0.42, respectively). Multivariate regression modeling showed that both Δpre-EWL and Δpre-TWL were significantly associated with lymphocyte count (Δpre-EWL; P = .01, Δpre-TWL; P = .01). A comparison between the high (Δ pre-EWL > 0.098) and low weight loss group (Δ pre-EWL < 0.098) demonstrated a significant difference in the expression of the activation marker CD69 on CD56bright Natural killer (NK) cells (P = .01), whereas there was no difference in the frequency of T cells, Natural killer T cells, or NK cells. Additionally, high CRP levels were associated with CD69 expression in CD56bright NK cells (P = .01, R = 0.57). Peripheral lymphocytes, especially CD69-positive CD56bright NK cells, are involved in preoperative weight loss after bariatric surgery, and systemic inflammation may inhibit weight loss before surgery.

Increased innate immune activation induces protective RSV-specific lung-resident memory T cells in neonatal mice

Young infants frequently experience respiratory tract infections, yet vaccines designed to provide mucosal protection are lacking. Localizing pathogen-specific cellular and humoral immune responses to the lung could provide improved immune protection. We used a well-characterized murine model of respiratory syncytial virus (RSV) to study the development of lung-resident memory T cells (TRM) in neonatal compared to adult mice. We demonstrated that priming with RSV during the neonatal period failed to retain RSV-specific clusters of differentiation (CD8) TRM 6 weeks post infection, in contrast to priming during adulthood. The reduced development of RSV-specific TRM was associated with poor acquisition of two key markers of tissue residence: CD69 and CD103. However, by augmenting both innate immune activation and antigen exposure, neonatal RSV-specific CD8 T cells increased expression of tissue-residence markers and were maintained in the lung at memory time points. Establishment of TRM correlated with more rapid control of the virus in the lungs upon reinfection. This is the first strategy to effectively establish RSV-specific TRM in neonates providing new insight into neonatal memory T cell development and vaccine strategies.

Characterization of Bovine Intraepithelial T Lymphocytes in the Gut

Intraepithelial T lymphocytes (T-IELs), which constitute over 50% of the total T lymphocytes in the animal, patrol the mucosal epithelial lining to defend against pathogen invasion while maintaining gut homeostasis. In addition to expressing T cell markers such as CD4 and CD8, T-IELs display T cell receptors (TCR), including either TCRαβ or TCRγδ. Both humans and mice share similar T-IEL subsets: TCRγδ+, TCRαβ+CD8αα+, TCRαβ+CD4+, and TCRαβ+CD8αβ+. Among these subsets, human T-IELs are predominantly TCRαβ+ (over 80%), whereas those in mice are mostly TCRγδ+ (~60%). Of note, the majority of the TCRγδ+ subset expresses CD8αα in both species. Although T-IELs have been extensively studied in humans and mice, their profiles in cattle have not been well examined. Our study is the first to characterize bovine T-IELs using flow cytometry, where we identified several distinct features. The percentage of TCRγδ+ was comparable to that of TCRαβ+ T-IELs (both ~50% of CD3+), and the majority of bovine TCRγδ+ T-IELs did not express CD8 (CD8-) (above 60%). Furthermore, about 20% of TCRαβ+ T-IELs were CD4+CD8αβ+, and the remaining TCRαβ+ T-IELs were evenly distributed between CD4+ and CD8αβ+ (~40% of TCRαβ+ T-IELs each) with no TCRαβ+CD8αα+ identified. Despite these unique properties, bovine T-IELs, similar to those in humans and mice, expressed a high level of CD69, an activation and tissue-retention marker, and a low level of CD62L, a lymphoid adhesion marker. Moreover, bovine T-IELs produced low levels of inflammatory cytokines such as IFNγ and IL17A, and secreted small amounts of the immune regulatory cytokine TGFβ1. Hence, bovine T-IELs' composition largely differs from that of human and mouse, with the dominance of the CD8- population among TCRγδ+ T-IELs, the substantial presence of TCRαβ+CD4+CD8αβ+ cells, and the absence of TCRαβ+CD8αα+ T-IELs. These results provide the groundwork for conducting future studies to examine how bovine T-IELs respond to intestinal pathogens and maintain the integrity of the gut epithelial barrier in animals.

Memory T Cells in the Immunoprevention of Cancer: A Switch from Therapeutic to Prophylactic Approaches

Cancer immunoprevention, the engagement of the immune system to prevent cancer, is largely overshadowed by therapeutic approaches to treating cancer after detection. Vaccines or, alternatively, the utilization of genetically engineered memory T cells could be methods of engaging and creating cancer-specific T cells with superb memory, lenient activation requirements, potent antitumor cytotoxicity, tumor surveillance, and resilience against immunosuppressive factors in the tumor microenvironment. In this review we analyze memory T cell subtypes based on their potential utility in cancer immunoprevention with regard to longevity, localization, activation requirements, and efficacy in fighting cancers. A particular focus is on how both tissue-resident memory T cells and stem memory T cells could be promising subtypes for engaging in immunoprevention.

CD8+ tissue-resident memory T-cell development depends on infection-matching regulatory T-cell types

Immunological memory is critical for immune protection, particularly at epithelial sites, which are under constant risk of pathogen invasions. To counter invading pathogens, CD8+ memory T cells develop at the location of infection: tissue-resident memory T cells (TRM). CD8+ T-cell responses are associated with type-1 infections and type-1 regulatory T cells (TREG) are important for CD8+ T-cell development, however, if CD8+ TRM cells develop under other infection types and require immune type-specific TREG cells is unknown. We used three distinct lung infection models, to show that type-2 helminth infection does not establish CD8+ TRM cells. Intracellular (type-1) and extracellular (type-3) infections do and rely on the recruitment of response type-matching TREG population contributing transforming growth factor-β. Nevertheless, type-1 TREG cells remain the most important population for TRM cell development. Once established, TRM cells maintain their immune type profile. These results may have implications in the development of vaccines inducing CD8+ TRM cells.

Recruitment and Residence of Intestinal T Cells - Lessons for Therapy in Inflammatory Bowel Disease

Targeting leukocyte trafficking in the management of inflammatory bowel disease [IBD] has been a significant therapeutic advance over the past 15 years. However, as with other advanced therapies, phase III clinical trials report response to trafficking inhibitors in only a proportion of patients, with fewer achieving clinical remission or mucosal healing. Additionally, there have been significant side effects, most notably progressive multifocal leukoencephalopathy in association with the α4 inhibitor natalizumab. This article reviews the mechanisms underpinning T cell recruitment and residence, to provide a background from which the strength and limitations of agents that disrupt leukocyte trafficking can be further explored. The therapeutic impact of trafficking inhibitors is underpinned by the complexity and plasticity of the intestinal immune response. Pathways essential for gut homing in health may be bypassed in the inflamed gut, thus providing alternative routes of entry when conventional homing molecules are targeted. Furthermore, there is conservation of trafficking architecture between proinflammatory and regulatory T cells. The persistence of resident memory cells within the gut gives rise to local established pro-inflammatory populations, uninfluenced by inhibition of trafficking. Finally, trafficking inhibitors may give rise to effects beyond the intended response, such as the impact of vedolizumab on innate immunity, as well as on target side effects. With significant research efforts into predictive biomarkers already underway, it is ultimately hoped that a better understanding of trafficking and residence will help us predict which patients are most likely to respond to inhibition of leukocyte trafficking, and how best to combine therapies.

Graded expression of the chemokine receptor CX3CR1 marks differentiation states of human and murine T cells and enables cross-species interpretation

T cells differentiate into functionally distinct states upon antigen encounter. These states are delineated by different cell surface markers for murine and human T cells, which hamper cross-species translation of T cell properties. We aimed to identify surface markers that reflect the graded nature of CD8+ T cell differentiation and delineate functionally comparable states in mice and humans. CITEseq analyses revealed that graded expression of CX3CR1, encoding the chemokine receptor CX3CR1, correlated with the CD8+ T cell differentiation gradient. CX3CR1 expression distinguished human and murine CD8+ and CD4+ T cell states, as defined by migratory and functional properties. Graded CX3CR1 expression, refined with CD62L, accurately captured the high-dimensional T cell differentiation continuum. Furthermore, the CX3CR1 expression gradient delineated states with comparable properties in humans and mice in steady state and on longitudinally tracked virus-specific CD8+ T cells in both species. Thus, graded CX3CR1 expression provides a strategy to translate the behavior of distinct T cell differentiation states across species.

Get me out of here: Sphingosine 1-phosphate signaling and T cell exit from tissues during an immune response

During an immune response, the duration of T cell residence in lymphoid and non-lymphoid tissues likely affects T cell activation, differentiation, and memory development. The factors that govern T cell transit through inflamed tissues remain incompletely understood, but one important determinant of T cell exit from tissues is sphingosine 1-phosphate (S1P) signaling. In homeostasis, S1P levels are high in blood and lymph compared to lymphoid organs, and lymphocytes follow S1P gradients out of tissues into circulation using varying combinations of five G-protein coupled S1P receptors. During an immune response, both the shape of S1P gradients and the expression of S1P receptors are dynamically regulated. Here we review what is known, and key questions that remain unanswered, about how S1P signaling is regulated in inflammation and in turn how S1P shapes immune responses.

Tumor-resident memory T cells as a biomarker of the response to cancer immunotherapy

Tumor-infiltrating lymphocytes (TIL) often include a substantial subset of CD8+ tissue-resident memory T (TRM) cells enriched in tumor-specific T cells. These TRM cells play a major role in antitumor immune response. They are identified on the basis of their expression of the CD103 (αE(CD103)β7) and/or CD49a (α1(CD49a)β1) integrins, and the C-type lectin CD69, which are involved in tissue residency. TRM cells express several T-cell inhibitory receptors on their surface but they nevertheless react strongly to malignant cells, exerting a strong cytotoxic function, particularly in the context of blocking interactions of PD-1 with PD-L1 on target cells. These TRM cells form stable conjugates with autologous tumor cells and interact with dendritic cells and other T cells within the tumor microenvironment to orchestrate an optimal in situ T-cell response. There is growing evidence to indicate that TGF-β is essential for the formation and maintenance of TRM cells in the tumor, through the induction of CD103 expression on activated CD8+ T cells, and for the regulation of TRM effector functions through bidirectional integrin signaling. CD8+ TRM cells were initially described as a prognostic marker for survival in patients with various types of cancer, including ovarian, lung and breast cancers and melanoma. More recently, these tumor-resident CD8+ T cells have been shown to be a potent predictive biomarker of the response of cancer patients to immunotherapies, including therapeutic cancer vaccines and immune checkpoint blockade. In this review, we will highlight the major characteristics of tumor TRM cell populations and the possibilities for their exploitation in the design of more effective immunotherapy strategies for cancer.

Friend or Foe - Tc17 cell generation and current evidence for their importance in human disease

The term Tc17 cells refers to interleukin 17 (IL-17)-producing CD8+ T cells. While IL-17 is an important mediator of mucosal defense, it is also centrally involved in driving the inflammatory response in immune-mediated diseases, such as psoriasis, multiple sclerosis, and inflammatory bowel disease. In this review, we aim to gather the current knowledge on the phenotypic and transcriptional profile, the in vitro and in vivo generation of Tc17 cells, and the evidence pointing towards a relevant role of Tc17 cells in human diseases such as infectious diseases, cancer, and immune-mediated diseases.

Selected Immunohistochemical Assessment and Clinical Examinations in the Diagnosis of Palatine Tonsil Diseases

INTRODUCTION

The palatine tonsils are secondary lymphoid organs where immune processes occur, influencing the development of a targeted cellular and humoral response. The diseased tonsils are subject to immunological imbalances, including the activity of pro-inflammatory and anti-inflammatory factors. This leads to the development of palatine tonsil diseases, such as palatine tonsillitis and palatine tonsillar hypertrophy.

AIM

The main aim of the study was to evaluate the similarities and differences in the clinical and pathomorphological pictures of patients qualified for surgical treatment due to hypertrophy or inflammation of the palatine tonsils. The aim was achieved by demonstrating the relationship between the patient's medical history and physical examination and histopathological diagnosis of a given tonsillar disease, evaluating the usefulness of basic blood tests (leukocytosis, ASO, ESR, and CRP) in differential diagnosis, and assessing the immunohistochemical assessment of palatine tonsil tissue.

MATERIAL AND METHODS

The tonsils were stained with the following antibodies: IL-1, IL-2, IL-6, IL-8 IL-10, and IL-37 and CD25, CD40, and CD69, taking into account the histological division of the studied lymphatic tissue (epithelial, subepithelial, follicular, follicular center, and interfollicular). Patients aged between 19 and 70 years with tonsillitis or clinical signs of tonsillar hypertrophy were qualified for tonsillectomy/UPPP. Seventy-two males (68.6%) and thirty-three females (31.4%) were enrolled in the study. Histopathological and immunohistochemical assessment was performed on 105 palatine tonsils.

RESULTS

The diagnostic value of blood tests, including determination of ASO, ESR, CRP, and leukocyte level, proved to be a significant predictor of tonsil disease. In the pathomorphological assessment, 75% of the subjects who had simultaneously elevated ESR (>4.73) and leukocytosis (>6.96) and reduced ASO (<161.03) and CRP (<0.31) belonged to the tonsillitis group. The immunohistochemical assessment revealed a diverse profile of the markers tested depending on the diagnosed disease of the tonsils. The follicular center proved to be the region of palatine tonsil tissue for which the most statistically significant differences between the markers were found. Responses to CD-40 and IL-1 were observed in this region. The tissue of epithelial, follicular, and interfollicular regions each showed one statistically significant value for the studied chemokines and lymphokines. However, the lack of significant statistical differences for p < 0.05 between the study groups was only noted in the subepithelial region. It should be emphasized that for the data as a whole (calculated on the basis of the data for all regions together), no statistically significant differences were observed.

CONCLUSION

In conclusion, the results obtained are indicative of the presence of a specific immunohistochemical profile for palatine tonsil diseases. Significant discrepancies have been found in the clinical and pathomorphological assessment of tonsils qualified for tonsillectomy. Therefore, these methods should be considered complementary. The patient's medical history and physical examination, depending on the adopted clinical or histopathological classification, show a variation in the distribution of features that are the basis for allocation to a particular group.

The Sphingosine 1-Phosphate Axis: an Emerging Therapeutic Opportunity for Endometriosis

Endometriosis is a common condition in women of reproductive age, but its current interventions are unsatisfactory. Recent research discovered a dysregulation of the sphingosine 1-phosphate (S1P) signaling pathway in endometriosis and showed a positive outcome by targeting it. The S1P axis participates in a series of fundamental pathophysiological processes. This narrative review is trying to expound the reported and putative (due to limited reports in this area for now) interactions between the S1P axis and endometriosis in those pathophysiological processes, to provide some perspectives for future research. In short, S1P signaling pathway is highly activated in the endometriotic lesion. The S1P concentration has a surge in the endometriotic cyst fluid and the peritoneal fluid, with the downstream dysregulation of its receptors. The S1P axis plays an essential role in the migration and activation of the immune cells, fibrosis, angiogenesis, pain-related hyperalgesia, and innervation. S1P receptor (S1PR) modulators showed an impressive therapeutic effect by targeting the different S1P receptors in the endometriosis model, and many other conditions resemble endometriosis. And several of them already got approval for clinical application in many diseases, which means a drug repurposing direction and a rapid clinical translation for endometriosis treatments.

Functional heterogeneity of human skin-resident memory T cells in health and disease

The human skin is populated by a diverse pool of memory T cells, which can act rapidly in response to pathogens and cancer antigens. Tissue-resident memory T cells (TRM ) have been implicated in range of allergic, autoimmune and inflammatory skin diseases. Clonal expansion of cells with TRM properties is also known to contribute to cutaneous T-cell lymphoma. Here, we review the heterogeneous phenotypes, transcriptional programs, and effector functions of skin TRM . We summarize recent studies on TRM formation, longevity, plasticity, and retrograde migration and contextualize the findings to skin TRM and their role in maintaining skin homeostasis and altered functions in skin disease.

Lung-resident CD69+ST2+ TH2 cells mediate long-term type 2 memory to inhaled antigen in mice

BACKGROUND

Chronic airway diseases such as asthma are characterized by persistent type 2 immunity in the airways. We know little about the mechanisms that explain why type 2 inflammation continues in these diseases.

OBJECTIVE

We used mouse models to investigate the mechanisms involved in long-lasting immune memory.

METHODS

Naive mice were exposed intranasally to ovalbumin (OVA) antigen with Alternaria extract as an adjuvant. Type 2 memory was analyzed by parabiosis model, flow cytometry with in vivo antibody labeling, and intranasal OVA recall challenge. Gene-deficient mice were used to analyze the mechanisms.

RESULTS

In the parabiosis model, mice previously exposed intranasally to OVA with Alternaria showed more robust antigen-specific immune responses and airway inflammation than mice with circulating OVA-specific T cells. After a single airway exposure to OVA with Alternaria, CD69+ST2+ TH2-type T cells, which highly express type 2 cytokine messenger RNA and lack CD62L expression, appeared in lung tissue within 5 days and persisted for at least 84 days. When exposed again to OVA in vivo, these cells produced type 2 cytokines quickly without involving circulating T cells. Development of tissue-resident CD69+ST2+ TH2 cells and long-term memory to an inhaled antigen were abrogated in mice deficient in ST2 or IL-33, but not TSLP receptor.

CONCLUSION

CD69+ST2+ TH2 memory cells develop quickly in lung tissue after initial allergen exposure and persist for a prolonged period. The ST2/IL-33 pathway may play a role in the development of immune memory in lung to certain allergens.

Retinoic acid signaling during priming licenses intestinal CD103+ CD8 TRM cell differentiation

CD8 tissue-resident memory T (TRM) cells provide frontline protection at barrier tissues; however, mechanisms regulating TRM cell development are not completely understood. Priming dictates the migration of effector T cells to the tissue, while factors in the tissue induce in situ TRM cell differentiation. Whether priming also regulates in situ TRM cell differentiation uncoupled from migration is unclear. Here, we demonstrate that T cell priming in the mesenteric lymph nodes (MLN) regulates CD103+ TRM cell differentiation in the intestine. In contrast, T cells primed in the spleen were impaired in the ability to differentiate into CD103+ TRM cells after entry into the intestine. MLN priming initiated a CD103+ TRM cell gene signature and licensed rapid CD103+ TRM cell differentiation in response to factors in the intestine. Licensing was regulated by retinoic acid signaling and primarily driven by factors other than CCR9 expression and CCR9-mediated gut homing. Thus, the MLN is specialized to promote intestinal CD103+ CD8 TRM cell development by licensing in situ differentiation.

Barriers to immune cell infiltration in tumors

Increased immune cell infiltration into tumors is associated with improved patient survival and predicts response to immune therapies. Thus, identification of factors that determine the extent of immune infiltration is crucial, so that methods to intervene on these targets can be developed. T cells enter tumor tissues through the vasculature, and under control of interactions between homing receptors on the T cells and homing receptor ligands (HRLs) expressed by tumor vascular endothelium and tumor cell nests. HRLs are often deficient in tumors, and there also may be active barriers to infiltration. These remain understudied but may be crucial for enhancing immune-mediated cancer control. Multiple intratumoral and systemic therapeutic approaches show promise to enhance T cell infiltration, including both approved therapies and experimental therapies. This review highlights the intracellular and extracellular determinants of immune cell infiltration into tumors, barriers to infiltration, and approaches for intervention to enhance infiltration and response to immune therapies.

Tissue-resident memory T cells in the multiple sclerosis brain and their relationship to Epstein-Barr virus infected B cells

Presence of EBV infected B cells and EBV-specific CD8 T cells in the multiple sclerosis (MS) brain suggests a role for virus-driven immunopathology in brain inflammation. Tissue-resident memory (Trm) T cells differentiating in MS lesions could provide local protection against EBV reactivation. Using immunohistochemical techniques to analyse canonical tissue residency markers in postmortem brains from control and MS cases, we report that CD103 and/or CD69 are mainly expressed in a subset of CD8+ T cells that intermingle with and contact EBV infected B cells in the infiltrated MS white matter and meninges, including B-cell follicles. Some Trm-like cells were found to express granzyme B and PD-1, mainly in white matter lesions. In the MS brain, Trm cells could fail to constrain EBV infection while contributing to sustain inflammation.