Obesity has become a worldwide scourge, affecting more than 10% of adults worldwide. While widely recognized to be associated with increased incidence of medical conditions such as diabetes mellitus and atherosclerosis, obesity also accounts for 9% of the cancer burden in some populations. This is due in part to perturbation of protective immune mechanisms involving natural killer cells, macrophages, and neutrophils. Recent studies indicate that γδ T cells play a prominent protective role against cancer, but in some circumstances are detrimental and pro tumorogenic. In this review, the current scientific literature was explored to determine whether and how obesity affects the anti- and pro-tumoral functions of γδ T cells. Considerable perturbations of γδ T cells by obesity were revealed, suggesting that the “obesity-γδ T cell axis” may profoundly impact the increased incidence of cancer in obese individuals and is worthy of further study.

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Lower respiratory tract infections caused over 4 million deaths per year worldwide, especially in low-income countries. Viral respiratory infections often occur as rapidly spreading seasonal endemic or epidemic, and sometimes due to new respiratory viruses including corona viruses. The first level of host defense against viral infection is based on the innate immune system and intracellular killing mechanisms. The latter is activated by the release of viral DNA or RNA into the cytosol of the infected cells during the initial phase of virus replication. Viral DNA and RNA are recognized by the cyclic guanosine monophosphate (cGMP)-adenosine monophosphate (AMP) synthase (cGAS)–stimulator of interferon (IFN) genes (STING) sensing pathway, leading to the activation of type-I and -III IFN synthesis, with the aim to limit viral replication. However, the efficacy of the cGAS-STING sensing mechanism seems to vary with different viruses, and therefore, so is the efficacy of the host defense mechanism. Viral DNA can be sensed by different proteins including DNA-dependent activator of IFN regulating factor (DAI), cGAS, and toll-like receptor-9 (TLR-9). Viral RNA is recognized by retinoid acid-inducible gene 1 (RIG-1), TLR-7 and TLR-8. The question if cGAS also recognizes viral RNA remains unclear. The activation of IFN synthesis by cGAS is initiated by the recognition of purines and pyrimidines and their enzymatic conversion into cGMP and cyclic AMP (cAMP), followed by the activation of STING. In addition, it is indicated that several viruses can evade the cGAS-STING signaling and escape the host defense. This review aims to summarize the role of cGAS-STING as a host defense mechanism against viral respiratory tract infections.

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Treatment of sepsis currently relies on eliminating the causal pathogen and supportive care, whereas almost no approaches to interfere with the defining event of a “dysregulated host response” are available. This review points to the striking correlation of two phenotypes of sepsis etiopathology with the concept of bipartite response patterns of higher organisms to microbial attacks. According to this concept, the phenotypes of sepsis can be interpreted as either resistance or tolerance responses to infection that got out of hand. This concept might allow focusing sepsis research and related patient studies on key conundrums of current sepsis research: how do resistance responses result in immunopathology and how can tolerance lead to systemic immunosuppression or even immunoparalysis? The heuristic vigor of these questions might inspire experimental efforts and clinical studies and ultimately advance the therapeutic armamentarium for sepsis care.

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Self-replicating RNA viruses have been commonly used for preventive and therapeutic interventions in the fields of infectious diseases and cancers. Both RNA viruses with single-stranded RNA genomes of positive and negative polarity have been utilized. Expression of viral surface proteins from self-replicating RNA virus vectors has elicited strong immune responses and provided protection against challenges with lethal doses of pathogens in various animal models using recombinant viral particles, RNA replicons, or plasmid-based replicon vectors. Similarly, immunization with self-replicating RNA virus vectors expressing tumor antigens has induced tumor-specific antibody (Ab) responses, inhibited tumor growth, eradicated tumors, and protected immunized animals against tumor challenges. Clinical trials have demonstrated good safety and tolerance of self-replicating RNA viruses. Although the number of clinical trials is low, robust immune responses and protection against challenges with pathogens and tumor cells have been achieved. The Ervebo vaccine against Ebola virus disease has been approved by both the European Medicines Agency (EMA) and the US Food and Drug Administration (FDA).

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The crown-like shaped viruses known as coronaviruses which were first reported in the 1960’s have caused three epidemics in the past two decades namely, coronavirus disease-19 (COVID-19), severe acute respiratory syndrome (SARS), and Middle East respiratory syndrome (MERS). SARS coronavirus 2 (SARS-CoV-2) was first reported in the latter half of December in Wuhan, a city of China, with people affected by deadly pneumonia with unknown etiology. Since then, the world has experienced two phases of virus spread with different symptoms and disease severity. This review embarks on the journey to investigate candidate molecules of this virus which can and are being investigated for various vaccine formulations and to discuss immunity developed against this virus.

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Alzheimer’s disease (AD) is a common neurological disease in the elderly, and the major manifestations are cognitive dysfunction, neuronal loss, and neuropathic lesions in the brain. In the process of AD pathogenesis, the inflammatory response plays an indispensable role. The nucleotide-binding oligomerization domain (NOD)-like receptor family pyrin domain containing 3 (NLRP3) inflammasome containing NOD, leucine-rich repeat (LRR), and pyran domains is a multi-molecular complex that can detect dangerous signals related to neurological diseases. The assembly of NLRP3 inflammasome promotes the maturation of interleukin-1beta (IL-1β) and IL-18 mediated by caspase-1 in microglia, which leads to neuroinflammation and finally contributes to the occurrence and development of AD. This review aimed to clarify the structure and activating mechanism of NLRP3 inflammasome and its key role in the pathogenesis of AD, summarize the latest findings on the suppression of NLRP3 inflammasome activation for the treatment of AD, as well as indicate that targeting regulation of NLRP3 inflammasome assembly may be a potential strategy for the treatment of AD, providing a theoretical basis for the research of AD.

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Recent anti-cancer strategies are based on the stimulation of anti-tumor immune reaction, exploiting distinct lymphocyte subsets. Among them, γδ T cells represent optimal anti-cancer candidates, especially in those tissues where they are highly localized, such as the respiratory or gastrointestinal tract. One important challenge has been the identification of stimulating drugs able to induce and maintain γδ T cell-mediated anti-cancer immune response. Amino-bisphosphonates (N-BPs) have been largely employed in anti-cancer clinical trials due to their ability to upregulate the accumulation of pyrophosphates that promote the activation of Vγ9Vδ2 T cells. This activation depends on the butyrophilin A family, which is crucial in contributing to Vγ9Vδ2 T cells stimulation but is not equally expressed in all cancer tissues. Thus, the clinical outcome of such treatments is still a challenge. In this viewpoint, a critical picture of γδ T cells as effective anti-cancer effectors is designed, with a specific focus on the best immune-stimulating therapeutic schemes involving this lymphocyte subset and the tools available to measure their efficacy and presence in tumor tissues. Some pre-clinical models, useful to measure γδ T cell anti-cancer potential and their response to stimulating drugs, therapeutic monoclonal antibodies, or bispecific antibodies are described. Computerized imaging and digital pathology are also proposed as a help in the identification of co-stimulatory molecules and localization of γδ T cell effectors. Finally, two types of novel drug preparation are proposed: nanoparticles loaded with N-BPs and pro-drug formulations that enhance the effectiveness of γδ T lymphocyte stimulation.

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Until now, despite 30 years of intensive work, the RV144 human immunodeficiency virus (HIV) vaccine trial initiated in 2003 remains so far the most protective vaccine prototype of all those tested (32% reduction in the infection rate three years after the vaccination) and the HIV epidemic is still spreading worldwide. In addition, antiretroviral therapy (ART) for people living with HIV is given for life as no other pharmacological intervention has allowed to maintain an undetectable viral load after ART withdrawal. Pr Andrieu and colleagues discovered tolerogenic CD8+T-cells that suppress simian immunodeficiency virus (SIV) specific activation, ensuing SIV reverse transcription suppression and viral replication-defective in Chinese macaques vaccinated by intragastric route with inactivated SIV particles + Lactobacillus rhamnosus. Moreover, in HIV-infected elite controllers with specific genetic features (HLA-1-Bw4-80i and KIR3DL1 genes), Pr Andrieu found out that similar tolerogenic CD8+T-cells suppress in the same manner HIV-specific activation, HIV reverse transcription, and HIV replication. These data justify the development of a tolerogenic vaccine composed of inactivated HIV particles + Lactobacillus rhamnosus that could be used as a preventive or therapeutic vaccine.

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Although a large number of preventative human immunodeficiency virus (HIV) vaccine trials have been carried out during the last 30 years, it is remarkable that an effective HIV vaccine has not yet been developed. Research paradigms correspond to theoretical assumptions and particular strategies that scientists use when they try to solve a particular problem. Many paradigms used successfully in vaccinology were ineffective with HIV. For instance: 1) The structure-based reverse vaccinology approach failed because investigators tried to generate a vaccine starting with the antigenic structure of HIV-envelope (Env) epitopes bound to neutralizing monoclonal antibodies (mAbs) derived from HIV-infected individuals. They assumed that this antigenic structure would also possess the immunogenic capacity of inducing in vaccinees a polyclonal antibody (Ab) response with the same neutralizing capacity as the mAb. 2) The structures observed in epitope-paratope crystallographic complexes result from mutually induced fit between the two partners and do not correspond to the structures present in the free molecules before they had interacted. 3) The affinity-matured neutralizing mAbs obtained from chronically infected individuals did not recognize the germline predecessors of these Abs present in vaccinees. 4) The HIV p17 matrix protein that lines the inner surface of the viral membrane is one of the most disordered proteins identified on our planet and this prevents the induced Abs from binding to the glycosylated HIV gp120 protein. 5) Vaccinologists need to solve so-called inverse problems, for instance, guessing what are the multiple causes that produced an earlier wanted beneficial effect such as the absence of deleterious HIV infection in elite controllers. Since the immune system consists of numerous subsystems that have not yet been elucidated, it is impossible to solve the inverse problems posed by each subsystem. 6) Vaccinology is an empirical science that only sometimes succeeds because we do not understand the complex mechanisms that lead to protective immune responses.

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Gamma delta lymphocytes (γδ T) sit at the interface between innate and adaptive immunity. They have the capacity to recognize cancer cells by interaction of their surface receptors with an array of cancer cell surface target antigens. Interactions include the binding of γδ T cell receptors, the ligands for which are diverse and do not involve classical major histocompatibility complex (MHC) molecules. Moreover, a variety of natural killer-like and fragment crystallizable gamma (Fcγ) receptors confer additional cancer reactivity. Given this innate capacity to recognize and kill cancer cells, there appears less rationale for redirecting specific to cancer cell surface antigens through chimeric antigen receptor (CAR) expression. Several groups have however reported research findings that expression of CARs in γδ T cells can confer additional specificity or functionality. Though limited in number, these studies collectively identify the potential of CAR-T engineering to augment and fine tune anti-cancer responses. Together with the lack of graft versus host disease induced by allogeneic γδ T cells, these insights should encourage researchers to explore additional γδ T-CAR refinements for the development of off-the-shelf anti-cancer cell therapies.

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Avidity of immunoglobulin G (IgG) is defined as its binding strength to its target antigen. As a consequence of affinity maturation of the IgG response, avidity is maturing as well. Therefore, acute infections are characterized by low-avidity IgG, whereas past infections are usually associated with high-avidity IgG. Avidity maturation is also observed as a consequence of optimal vaccination. Avidity has been shown to play a significant role in protective humoral immunity in many microbial systems. After severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, the situation is different compared to other viral infections, as the moderate degree of avidity reached in most cases of infection is similar to that reached after only one vaccination step. In contrast, two vaccination steps lead to a much higher avidity of IgG directed towards viral spike protein S1 (S1) in the majority of vaccinated individuals. Therefore, it seems that two vaccination steps allow for a more extended affinity/avidity maturation than natural infection. The degree of avidity maturation after two vaccination steps is heterogeneous. It can be further enhanced by a third vaccination step. Complete avidity maturation seems to depend on sustained availability of antigen during the maturation process. Variants of concern seem to increase the affinity of their receptor-binding domain (RBD) to angiotensin-converting enzyme-2 (ACE2) and/or to decrease the susceptibility for neutralizing antibodies. Classical neutralization tests do not necessarily reflect the avidity of neutralizing IgG, as they operationally dissect the binding reaction between S1 and IgG from the binding of the S1 to ACE2. This approach fades out critical competition reactions between IgG and ACE for RBD of the S1. Quantitative avidity determination might be an essential tool to define individuals that only possess suboptimal protective immunity after vaccination and therefore might benefit from an additional booster immunization.

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Allogeneic stem cell transplantation is currently the only curative approach for a variety of malignant and non-malignant diseases. In the early transplant era, the intent of this treatment was to apply an intensive myeloablative regimen to eliminate residual malignant cells followed by the hematopoietic rescue of the patients with donor hematopoietic stem cells. However, the focus has shifted over time and allogeneic transplantation is nowadays seen as a cellular therapy in which the donor-derived immune system mounts an anti-infectious and especially an anti-tumor effect in the posttransplant phase. In order to further augment the anti-tumor effect, various approaches have been developed, including the manipulation of the donor-derived immune system in vivo or the adoptive transfer of ex vivo-expanded donor-derived effector cells. Based on their lack of alloreactivity, γδ⁺ T cells are shifting into the spotlight of research in the context of allogeneic transplantation. Their exploitation with regard to their anti-infectious and anti-tumor properties and their in vivo and ex vivo manipulation will lead to new therapeutic approaches to improve the outcome of patients after allogeneic stem cell transplantation. In this review, the important role of γδ⁺ T cells in allogeneic matched and mismatched transplantation is summarized and an outlook is discussed on how to best make use of this unique cell population.

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γδ T cells express unique T cell receptor (TCR) γ and TCR δ chains, with structural and functional heterogeneity. Taking advantage of the diverse γδ TCR repertoire or other ligand-receptor interactions, γδ T cells can recognize a broad spectrum of tumor-associated antigens (TAAs) in a major histocompatibility complex (MHC)—independent manner, thereby activating downstream pleiotropic effects. γδ T cells recruited into the tumor microenvironment can act as effector cells to mediate cancer immune surveillance. Their advantage lies in the ability to perceive tumors with a low mutation load, thus establishing the first line of defense against pathogens. Activated γδ T cells exhibit strong cytotoxic activity and cytokine secretion functions and are effective antitumor lymphocytes with simple and direct recognition modes and rapid responses. However, the clinical application of tumor—infiltrating γδ T cells has certain limitations. First, γδ T cells exposed to complicated cytokine networks are potentially affected by multiple inhibitory mechanisms. Additionally, these cells show highly flexible and dynamic plasticity and are extremely easily polarized into regulatory phenotypes. This review further emphasizes the diversified cross-talk between γδ T cells and other immune cells. Effective immunity of the body is often manifested by counterbalance under mutual restriction. Therefore, an in-depth understanding of γδ T cells that play conflicting roles in the tumor microenvironment is necessary. These cells may be a key factor ultimately mediating the deviation of the antagonistic response between tumor inhibition and tumor promotion. Finally, it retrospectively analyze the activation strategies and clinical relevance of existing γδ T cell adoptive immunotherapies. According to current challenges, there is a need to explore innovative immunotherapies, maximize the tumor-killing efficacy of γδ T cells, and attenuate or eliminate tumor immunosuppression. It is hoped that the host immune status can be accurately predicted and gradually advance γδ T cell precise individualized medicine.

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Antitumor immunity relies on the ability of T cells to recognize and kill tumor targets. γδ T cells are a specialized subset of T cells that predominantly localizes to non-lymphoid tissue such as the skin, gut, and lung where they are actively involved in tumor immunosurveillance. γδ T cells respond to self-stress ligands that are increased on many tumor cells, and these interactions provide costimulatory signals that promote their activation and cytotoxicity. This review will cover costimulatory molecules that are known to be critical for the function of γδ T cells with a specific focus on mouse dendritic epidermal T cells (DETC). DETC are a prototypic tissue-resident γδ T cell population with known roles in antitumor immunity and are therefore useful for identifying mechanisms that may control activation of other γδ T cell subsets within non-lymphoid tissues. This review concludes with a brief discussion on how γδ T cell costimulatory molecules can be targeted for improved cancer immunotherapy.

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In recent years, immunologists have been working to utilize the functional mechanism of the immune system to research new tumor treatment methods and achieved a major breakthrough in 2013, which was listed as one of the top 10 scientific breakthroughs of 2013 by Science magazine (see “Cancer immunotherapy”. Science. 2013;342:1417. doi: 10.1126/science.1249481). Currently, two main methods are used in clinical tumor immunotherapy: immune checkpoint inhibitors and chimeric antigen receptor (CAR) T cells. Clinical responses to checkpoint inhibitors rely on blockade of the target neoantigens expressed on the surfaces of tumor cells, which can inhibit T cell activity and prevent the T cell immune response; therefore, the therapeutic effect is limited by the tumor antigen expression level. While CAR-T cell therapy can partly enhance neoantigen recognition of T cells, problems remain in the current treatment for solid tumors, such as restricted transport of adoptively transferred cells to the tumor site and off-targets. Immunologists have therefore turned their attention to γδ T cells, which are not restricted by the major histocompatibility complex (MHC) for neoantigen recognition and are able to initiate a rapid immune response at an early stage. However, due to the lack of an understanding of the antigens that γδ T cells recognize, the role of γδ T cells in tumorigenesis and tumor development is not clearly understood. In the past few years, extensive data identifying antigen ligands recognized by γδ T cells have been obtained, mainly focusing on bisphosphonates and small-molecule polypeptides, but few studies have focused on protein ligands recognized by γδ T cells. In this paper, we reviewed and analyzed the tumor-associated protein ligands of γδ T cells that have been discovered thus far, hoping to provide new ideas for the comprehensive application of γδ T cells in tumor immunotherapy.

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γδ T cells are one of the immune cell types that express antigen receptors. γδ T cells are able to recognize pathogens or cancer cells independently of human leukocyte antigen restriction, which is an important feature of αβ T cells. Therefore, γδ T cells are considered the bridge between innate and adaptive immunity. These cells exhibit important roles in immune surveillance, exert immune defense against tumors and have become promising effector cells for cancer immunotherapy. However, in particular circumstances, the tumor microenvironment seems to render γδ T cells immunosuppressive and even tumor-promoting, emphasizing the importance of regulating γδ T functions in realizing their translation into practical cancer immunotherapy. In recent years, increasing evidence has demonstrated that the intratumoral and peritumoral microbiota can have complex effects on tumor immunology. Thus, understanding the role of microbiota in the crosstalk between γδ T cells and tumors will provide insights for developing adjuvant immunotherapy with precise regulation of tumor-related microbiota. In the present review, the effects of microbiota on γδ T cell receptor repertoire and the roles of microbiota in some common tumors will be discussed, with implications for future cancer therapy.

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In recent decades, abundant methods for targeted tumor cell immunotherapy have been developed. It was recently discovered that excellent curative effects observed in hematological tumors cannot be achieved in solid tumors, as serious side effects will occur. These are all derived from engineered adaptive immune cells, the use of which will bring limitations. γδT cells have a unique ability to respond to a variety of tumor cells while linking innate immunity and adaptive immunity, and thus, they are an ideal source of therapeutic allogeneic cells. This review introduces strategies that can optimize the clinical application of γδT cells to provide novel ideas for adoptive immunotherapy in the future.

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Endometriosis is an inflammatory oestrogen-dependent chronic disease and is mainly expressed by pain and increased infertility. Several studies showed an increased prevalence of autoimmune systemic diseases and various autoantibodies in endometriosis. The association of these autoimmune markers and diseases could raise the fact that endometriosis is an authentic autoimmune or inflammatory disease and thus could argue for the use of immunomodulatory therapies. Usually, it is considered that the autoantibodies did not directly act in endometrium implants growth, and could be rather implicated in endometriosis-related infertility. The use of immunomodulatory strategies could be an important alternative or additional strategy to the use of hormones and surgery but need prospective well-designed trials.

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