The origin of diversity: studying the evolution of multi-faceted CD8+ T cell responses

Phytochemicals and Their Nanoformulations for Targeting Hepatocellular Carcinoma: Exploring Potential and Targeting Strategies

Hepatocellular carcinoma (HCC) continues to pose a global health concern, necessitating the exploration of innovative therapeutic approaches. In the recent decade, targeting tumor stroma consisting of extracellular matrix (ECM), immune cells, vascular system, hypoxia, and also suppressive mechanisms in HCC has attracted interest in repressing tumor growth and metastasis. Phytochemicals have attained considerable attention because of their manifold biological effects and high capacity for anticancer activities. These chemical agents have shown the capability to modulate different cells and secretions within the stroma of malignancies. In recent years, the development of nanoformulations has further enhanced the therapeutic potential of phytochemicals by improving their solubility, bioavailability, and targeted delivery to tumor tissues. This review aims to provide an encyclopedic overview of the potential of phytochemicals and their nanoformulations as promising therapeutic strategies for targeting HCC. The review initially highlights the broad array of phytochemicals exhibiting potent anticancer properties, including flavonoids, alkaloids, terpenoids, and phenolic compounds, among others. Then, the nanoformulations and modification of these agents will be reviewed. Finally, we will review the latest experiments that have examined the modulation of HCC using adjuvant phytochemicals and their nanoformulations.

Targeting anticancer immunity in melanoma tumour microenvironment: unleashing the potential of adjuvants, drugs, and phytochemicals

Melanoma poses a challenge in oncology because of its aggressive nature and limited treatment modalities. The tumour microenvironment (TME) in melanoma contains unique properties such as an immunosuppressive and high-density environment, unusual vasculature, and a high number of stromal and immunosuppressive cells. In recent years, numerous experiments have focused on boosting the immune system to effectively remove malignant cells. Adjuvants, consisting of phytochemicals, toll-like receptor (TLR) agonists, and cytokines, have shown encouraging results in triggering antitumor immunity and augmenting the therapeutic effectiveness of anticancer therapy. These adjuvants can stimulate the maturation of dendritic cells (DCs) and infiltration of cytotoxic CD8+ T lymphocytes (CTLs). Furthermore, nanocarriers can help to deliver immunomodulators and antigens directly to the tumour stroma, thereby improving their efficacy against malignant cells. The remodelling of melanoma TME utilising phytochemicals, agonists, and other adjuvants can be combined with current modalities for improving therapy outcomes. This review article explores the potential of adjuvants, drugs, and their nanoformulations in enhancing the anticancer potency of macrophages, CTLs, and natural killer (NK) cells. Additionally, the capacity of these agents to repress the function of immunosuppressive components of melanoma TME, such as immunosuppressive subsets of macrophages, stromal and myeloid cells will be discussed.

A Single-Cell Perspective on Memory T-Cell Differentiation

Memory differentiation of CD4 and CD8 T-cell populations has been extensively studied and many key molecular players and transcriptional networks have been identified. But how regulatory principles, identified on this population level, translate to immune responses that originate from single antigen-specific T cells is only now being elucidated. Here, we provide a short summary of the approaches used for mapping the fate of individual T cells and their progeny in vivo. We then highlight which major questions, with respect to memory T-cell differentiation, have been addressed by studying the development of single-cell-derived T-cell families during infection or vaccination. We discuss how fate decisions of single T cells are modulated by the affinity of their TCR and further shaped through a coregulation of T-cell differentiation and T-cell proliferation. These current findings indicate the early segregation into slowly dividing T central memory precursors (CMPs) and rapidly dividing non-CMPs, as a key event that separates the developmental paths of long- and short-lived T cells.

CD8+ T Lymphocytes: Crucial Players in Sjögren's Syndrome

Primary Sjögren's syndrome (pSS) is a chronic autoimmune disease associated with damage to multiple organs and glands. The most common clinical manifestations are dry eyes, dry mouth, and enlarged salivary glands. Currently, CD4+ T lymphocytes are considered to be key factors in the immunopathogenesis of pSS, but various studies have shown that CD8+ T lymphocytes contribute to acinar injury in the exocrine glands. Therefore, in this review, we discussed the classification and features of CD8+ T lymphocytes, specifically describing the role of CD8+ T lymphocytes in disease pathophysiology. Furthermore, we presented treatment strategies targeting CD8+ T cells to capitalize on the pathogenic and regulatory potential of CD8+ T lymphocytes in SS to provide promising new strategies for this inflammatory disease.

The elusive identity of CXCR5+ CD8 T cells in viral infection and autoimmunity: Cytotoxic, regulatory, or helper cells?

Our knowledge on the development and functions of CXCR5⁺ CD8 T cells is rudimentary when confronted to other extensively studied CD8 T cell subsets. A decade ago, it became apparent that CD8 T cells possess two additional and rather unexpected functional properties other than cytotoxicity, one involving what is known as B cell helper activity and the other involving suppression of self-reactive responses generally known as T cell regulation. Although these adaptive responses are well-known functions of CD4 T cells, they remain poorly understood in CD8 T cells. Thus far, three subsets of CXCR5⁺ CD8 T cells have been identified. The first subset of CXCR5⁺ CD8 T cells is present in chronic viral infections and is referred to as progenitors of exhausted T cells showing heightened proliferative and cytotoxic properties as compared to CXCR5^- CD8 T cells. The second subset of CXCR5⁺ CD8 T cells functions as regulatory T cells that inhibit CD4 T follicular helper (Tfh) humoral responses and the development of autoantibodies. The third subset of CXCR5⁺ CD8 T cells was identified in mice with mutations in immunoregulatory genes (i.e. FOXP3 and IL-2-deficient mice) and involves CD8 T cells with Tfh-like properties that promote humoral autoimmunity through interaction with B cells. This review summarizes the phenotype, function, and differentiation of CXCR5⁺ CD8 T cells.

Concepts of GPCR-controlled navigation in the immune system

G‐protein–coupled receptor (GPCR) signaling is essential for the spatiotemporal control of leukocyte dynamics during immune responses. For efficient navigation through mammalian tissues, most leukocyte types express more than one GPCR on their surface and sense a wide range of chemokines and chemoattractants, leading to basic forms of leukocyte movement (chemokinesis, haptokinesis, chemotaxis, haptotaxis, and chemorepulsion). How leukocytes integrate multiple GPCR signals and make directional decisions in lymphoid and inflamed tissues is still subject of intense research. Many of our concepts on GPCR‐controlled leukocyte navigation in the presence of multiple GPCR signals derive from in vitro chemotaxis studies and lower vertebrates. In this review, we refer to these concepts and critically contemplate their relevance for the directional movement of several leukocyte subsets (neutrophils, T cells, and dendritic cells) in the complexity of mouse tissues. We discuss how leukocyte navigation can be regulated at the level of only a single GPCR (surface expression, competitive antagonism, oligomerization, homologous desensitization, and receptor internalization) or multiple GPCRs (synergy, hierarchical and non‐hierarchical competition, sequential signaling, heterologous desensitization, and agonist scavenging). In particular, we will highlight recent advances in understanding GPCR‐controlled leukocyte navigation by intravital microscopy of immune cells in mice.

The TNF Superfamily Molecule LIGHT Promotes the Generation of Circulating and Lung-Resident Memory CD8 T Cells following an Acute Respiratory Virus Infection

The transition of effector T cells or memory precursors into distinct long-lived memory T cell subsets is not well understood. Although many molecules made by APCs can contribute to clonal expansion and effector cell differentiation, it is not clear if clonal contraction and memory development is passive or active. Using respiratory virus infection, we found that CD8 T cells that cannot express the TNF family molecule lymphotoxin-like, exhibits inducible expression, competes with HSV glycoprotein D for herpes virus entry mediator, a receptor expressed by T lymphocytes (LIGHT) are unimpaired in their initial response and clonally expand to form effector cell pools. Thereafter, LIGHT-deficient CD8 T cells undergo strikingly enhanced clonal contraction with resultant compromised accumulation of both circulating and tissue-resident memory cells. LIGHT expression at the peak of the effector response regulates the balance of several pro- and antiapoptotic genes, including Akt, and has a preferential impact on the development of the peripheral memory population. These results underscore the importance of LIGHT activity in programming memory CD8 T cell development, and suggest that CD8 effector T cells can dictate their own fate into becoming memory cells by expressing LIGHT.

Tracking genetically engineered lymphocytes long-term reveals the dynamics of T cell immunological memory

Long-lasting immune protection from pathogens and cancer requires the generation of memory T cells able to survive long-term. To unravel the immunological requirements for long-term persistence of human memory T cells, we characterized and traced, over several years, T lymphocytes genetically modified to express the thymidine kinase (TK) suicide gene that were infused in 10 patients after haploidentical hematopoietic stem cell transplantation (HSCT). At 2 to 14 years after infusion and in the presence of a broad and resting immune system, we could still detect effectors/effector memory (TEM/EFF), central memory (TCM), and stem memory (TSCM) TK(+) cells, circulating at low but stable levels in all patients. Longitudinal analysis of cytomegalovirus (CMV)- and Flu-specific TK(+) cells indicated that antigen recognition was dominant in driving in vivo expansion and persistence at detectable levels. The amount of infused TSCM cells positively correlated with early expansion and with the absolute counts of long-term persisting gene-marked cells. By combining T cell sorting with sequencing of integration (IS), TCRα and TCRβ clonal markers, we showed that T cells retrieved long-term were enriched in clones originally shared in different memory T cell subsets, whereas dominant long-term clonotypes appeared to preferentially originate from infused TSCM and TCM clones. Together, these results indicate that long-term persistence of gene-modified memory T cells after haploidentical HSCT is influenced by antigen exposure and by the original phenotype of infused cells. Cancer adoptive immunotherapy might thus benefit from cellular products enriched in lymphocytes with an early-differentiated phenotype.

Single cell behavior in T cell differentiation

Upon primary infection, naïve T cells that recognize their cognate antigen become activated, proliferate, and simultaneously differentiate into various subsets. A long-standing question in the field has been how this cellular diversification is achieved. Conceptually, diverse cellular output may either arise from every single cell or only from populations of naïve cells. Furthermore, such diversity may either be driven by cell-intrinsic heterogeneity or by external, niche-derived signals. In this review, we discuss how recently developed technologies have allowed the analysis of the mechanisms underlying T cell diversification at the single cell level. In addition, we outline the implications of this work on our understanding of the formation of immunological memory, and describe a number of unresolved key questions in this field.

The smallest unit: effector and memory CD8(+) T cell differentiation on the single cell level

CD8⁺ T cell immune responses provide immediate protection against primary infection and durable memory capable of rapidly fighting off re-infection. Immediate protection and lasting memory are implemented by phenotypically and functionally distinct T cell subsets. While it is now widely accepted that these diverge from a common source of naïve T cells (T_n), the developmental relation and succession of effector and memory T cell subsets is still under intense debate. Recently, a distinct memory T cell subset has been suggested to possess stem cell-like features, sparking the hope to harness its capacity for self-renewal and diversification for successful therapy of chronic infections or malignant diseases. In this review we highlight current developmental models of memory generation, T cell subset diversification and T cell stemness. We discuss the importance of single cell monitoring techniques for adequately mapping these developmental processes and take a brief look at signaling components active in the putative stem cell-like memory T cell compartment.