Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2; βCoV), the causative agent of coronavirus disease 2019 (COVID-19), causes severe lower respiratory tract infections and acute respiratory failure syndrome (ARDS). Deaths due to the ongoing COVID-19 pandemic for more than a year are still seen worldwide. Therefore, vaccine trials have gained importance. The discovery of the genome and protein structure of SARS-CoV-2 in a short time allowed the development of nucleic acid-based vaccines (mRNA and DNA vaccines), vector vaccines, inactivated virus vaccines, protein-based vaccines, virus-like particle vaccines, and live attenuated virus vaccines. Many companies, universities, and institutes around the world continue to develop effective vaccines against SARS-CoV-2. In this review, the structural features, classification, genome, and intracellular entry of SARS-CoV-2 coronaviruses, stimulation of the immune system and immunity, COVID-19 vaccine types, and the latest status of clinical trials of these vaccines have been reviewed.

Repeated inoculation with messenger RNA (mRNA) vaccines elicits immunoglobulin G4 (IgG4) antibody production. Such an increase in the concentration of specific and non-specific IgG4 antibodies allows the growth of some types of cancer by blocking the activation of effector immune cells. This work proposes the hypothesis that cancer growth may be indirectly promoted by increased concentrations of non-specific IgG4 antibodies by the following mechanisms: 1) IgG4 antibodies can bind to anti-tumor IgG1 antibodies and block their interaction with receptors located on effector cells, thus preventing the destruction of cancer cells, 2) IgG4 can interact with fragment crystallizable gamma receptor IIb (FcγRIIB) inhibitory receptors, thus reducing effector functions of innate immune cells, and 3) targeting of specific epitopes by IgG4 could be oncogenic by inducing the production of a microenvironment that can promote cancer development. This article reviews the supporting literature and suggests several experimental protocols to evaluate this hypothesis in the context of repeated inoculation with mRNA vaccines. Additionally, this work proposes some management options aimed at reducing the unfavorable molecular consequences that could mediate cancer development when encountering high concentrations of IgG4 antibodies.

Rheumatoid arthritis (RA) is a complex autoimmune disorder characterized by a spectrum of hypersensitivity reactions, encompassing Type II, Type III, and Type IV responses. Firstly, RA is marked by Type II hypersensitivity reactions driven by autoantibodies, such as rheumatoid factor (RF) and anti-(cyclic) citrullinated protein antibodies (ACPAs). These autoantibodies serve not only as serological markers for RA but also actively participate in inflammation, bone erosion, and clinical outcomes, with concurrent activation of the complement system involving C1q, C3, and C5 components specifically linked to RA progression and bone damage. Secondly, RA exhibits traits of Type III hypersensitivity, marked by the formation of immune complexes inciting inflammatory reactions. Immunoglobulin G (IgG) autoantibodies like RF and ACPA play pivotal roles in immune complex formation and the ensuing inflammatory responses. RA also demonstrates Type IV hypersensitivity propelled by CD4⁺ T cells, encompassing T helper 1 (Th1) and Th17 subsets. Th1 cells release interferon (IFN)-γ, promoting proinflammatory cytokines, while Th17 cells secrete IL-17, IL-22, and granulocyte-macrophage colony-stimulating factor (GM-CSF), contributing to synovial inflammation, bone and cartilage damage, and angiogenesis. RA concurrently exhibits features of Type II, Type III, and Type IV hypersensitivity. It is crucial to comprehend the presence and complex interplay of hypersensitivity responses and specific immune cell subsets in RA to create precise and efficient therapeutic approaches for the management of this incapacitating autoimmune condition. Thus, in this review, we aim to provide a comprehensive overview of the hypersensitivity features of RA.

Atopic dermatitis (AD) is characterized by skin barrier disruption, type 2 immune dysregulation, chronic pruritus, and abnormal colonization by Staphylococcus aureus (S. aureus). Tapinarof, an aryl hydrocarbon receptor modulator, has been demonstrated to attenuate the development of AD in clinical studies. Recently, we found that tapinarof upregulated the expression of filaggrin and loricrin, which are essential proteins in skin barrier functions. Paradoxically, tapinarof induced interleukin (IL)-24 secretion by normal human keratinocytes. IL-24 is produced by T helper 2 lymphocytes and keratinocytes following stimulation by type 2 cytokines, and IL-24 is upregulated in the skin of patients with AD. Furthermore, IL-24 contributes to skin barrier disruption and hyperplasia in AD, and it may exacerbate skin inflammatory responses, itch, and S. aureus infection. In this review, we summarized the current findings regarding the detrimental role of IL-24 in AD, thereby suggesting that co-treatment of tapinarof with therapeutics that block IL-24 signaling may represent a promising strategy for managing AD.

There have been significant developments in the design of nanostructured scaffolds for eliciting robust immune responses named vaccine. The technique is to produce strong immune responses is to manipulate the appearance of a pathogen. Subsequently pathogens such as viruses and bacteria often demonstrate of multiple copies of ligands on their surfaces, the immune system is predominantly sensitive towards multivalent presentations of antigens. Consequently, when designing a vaccine, it is beneficial to garnish a nanostructured surface with multiple copies of an antigen so it can effectively act as an immune booster. Different methods are there for the development of the vaccine, from them most of the techniques are well developed and reported and some of in the developing state. This review focuses primarily on cellular and non-cellular vaccines, the whole cells or cellular proteins either as the source of antigens or the platform in which to deliver the antigens. Purpose of this review, understand and discussion on the various vaccine platforms which will contribute noteworthy information to vaccine research and development (R and D).

Humans are afflicted by a wide spectrum of autoimmune disorders, ranging from those affecting just one or a few organs to those associated with more systemic effects. In most instances, the etiology of such disorders remains unknown; a consequence of this lack of knowledge is a lack of specific treatment options. Systemic lupus erythematosus (SLE) is the prototypic systemic autoimmune disorder; pathology is believed to be antibody-mediated, and multiple organs are targeted. Periods of disease “flares” are often followed by long periods of remission. The fact that SLE is more commonly observed in females, and also that it more particularly manifests in females in the reproductive age group, has quite naturally drawn attention to the potential roles that hormones play in disease onset and progression. This review attempts to shed light on the influences that key hormones might have on disease indicators and pathology. Databases (Google Scholar, PubMed) were searched for the following keywords (sometimes in certain combinations), in conjunction with the term “lupus” or “SLE”: autoantibodies, recurrent abortion, polycystic ovarian syndrome (PCOS), preeclampsia, pre-term delivery, estrogens, progesterone, androgens, prolactin, leptin, human chorionic gonadotropin (hCG). Cited publications included both research articles and reviews.

Mesenchymal stromal cells (MSCs) are a mesodermal stem cell population, with known self-renewal and multilineage differentiation properties. In the last century, MSCs have been widely used in regenerative medicine and tissue engineering approaches. MSCs initially were isolated from bone marrow aspirates, but currently have been identified in a great number of tissues of the human body. Besides their utilization in regenerative medicine, MSCs possess significant immunoregulatory/immunosuppressive properties, through interaction with the cells of innate and adaptive immunity. MSCs can exert their immunomodulatory properties with either cell-cell contact or via paracrine secretion of molecules, such as cytokines, growth factors and chemokines. Of particular importance, the MSCs’ immunomodulatory properties are explored as promising therapeutic strategies in immune-related disorders, such as autoimmune diseases, graft versus host disease, cancer. MSCs may also have an additional impact on coronavirus disease-19 (COVID-19), by attenuating the severe symptoms of this disorder. Nowadays, a great number of clinical trials, of MSC-mediated therapies are evaluated for their therapeutic potential. In this review, the current knowledge on cellular and molecular mechanisms involved in MSC-mediated immunomodulation were highlighted. Also, the most important aspects, regarding their potential application in immune-related diseases, will be highlighted. The broad application of MSCs has emerged their role as key immunomodulatory players, therefore their utilization in many disease situations is full of possibilities for future clinical treatment.

Skin is the largest organ of the body having multifunctional activities. It has a dynamic cellular network with unique immunologic properties to maintain defensive actions, photoprotection, immune response, inflammation, tolerogenic capacity, wound healing, etc. The immune cells of the skin exhibit distinct properties. They can synthesize active vitamin D [1,24(OH)₂D₃] and express vitamin D receptors. Any difficulties in the cutaneous immune system cause skin diseases (psoriasis, vitiligo, atopic dermatitis, skin carcinoma, and others). Vitamin D is an essential factor, exhibits immunomodulatory effects by regulating dendritic cells’ maturation, lymphocytes’ functions, and cytokine production. More specifically, vitamin D acts as an immune balancing agent, inhibits the exaggeration of immunostimulation. This vitamin suppresses T-helper 1 and T-helper 17 cell formation decreases inflammatory cytokines release and promotes the maturation of regulatory T cells and interleukin 10 secretion. The deficiency of this vitamin promotes the occurrence of immunoreactive disorders. Administration of vitamin D or its analogs is the therapeutic choice for the treatment of several skin diseases.

Cancer immunotherapy, especially T-cell driven targeting, has significantly evolved and improved over the past decade, paving the way to treat previously refractory cancers. Hematologic malignancies, given their direct tumor accessibility and less immunosuppressive microenvironment compared to solid tumors, are better suited to be targeted by cellular immunotherapies. Gamma delta (γδ) T cells, with their unique attributes spanning the entirety of the immune system, make a tantalizing therapeutic platform for cancer immunotherapy. Their inherent anti-tumor properties, ability to act like antigen-presenting cells, and the advantage of having no major histocompatibility complex (MHC) restrictions, allow for greater flexibility in their utility to target tumors, compared to their αβ T cell counterpart. Their MHC-independent anti-tumor activity, coupled with their ability to be easily expanded from peripheral blood, enhance their potential to be used as an allogeneic product. In this review, the potential of utilizing γδ T cells to target hematologic malignancies is described, with a specific focus on their applicability as an allogeneic adoptive cellular therapy product.

Immunity is continuously evolving by evolutionary mechanisms shaped by pathogenic stimuli of different kinds. Man-made nanomaterials (NMs) have been developed in the last decades and represent a novel challenge for our immune system, especially when applied to medical science. Toxicological studies of such nanoparticles (NPs) revealed that size, shape, and surface chemistry are key parameters to understand their noxious effects on cellular mechanisms. Less is known on the immune reactions to NMs since prolonged exposure data are not so detailed as the results for acute administration. The importance of immunity to biocompatible NPs is underlined by their increasing use as drug or gene delivery carriers in common pharmaceutical preparations and vaccines. In the latter case, the immunomodulatory properties of NMs allow their use also as efficient adjuvants to enhance the innate immune response. In the current manuscript, the authors discuss the main concepts in this fast-growing field by restricting our view to NMs with consolidated application in biomedicine.

Cutaneous homeostasis is maintained by dynamic cellular communications between different cell types in the skin through interactions with various mediators, including cytokines, chemokines and antimicrobial peptides/proteins (AMPs). Keratinocytes, as the major cell type of the epidermis, not only form a passive physical barrier, but also actively participate in the pathogenesis of many, if not all, inflammatory skin diseases. Keratinocytes highly interact with immune cells to shape, amplify or regulate inflammatory responses, thus triggering and/or sustaining these inflammatory skin diseases. In this review, crosstalk between keratinocytes and immune cells is summarized, and its contributions to two major inflammatory skin disorders including psoriasis and atopic dermatitis are highlighted.

Understanding the interactions of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) with humans is deeply grounded in immunology, from the diagnosis to pathogenesis, from the clinical presentations to the epidemiology, prevention, and treatment. However, the difficulty of capturing the complex and changeable array of immunological concepts and incorporating them into the strategies of control of the SARS-CoV-2 pandemic poses significant hindrances to establish optimal public health policies. The contribution of immunology to the control of the pandemic is to shed light on the features and mechanisms of the protective immunity elicited by SARS-CoV-2 infection and vaccines. Do they induce effective protective immunity? How? For how long? What is the effect of vaccination on individuals who were previously infected? To appropriately answer these questions, it is necessary to get rid of the outdated notion of a naïve, static, and closed immune system, which leads to misconceptions about susceptibility, specificity, immunological memory, and protective immunity. The present essay discusses these issues based on current immunological concepts.

Interleukin (IL)-22 is produced from immune cells such as T helper (Th)22 cells, Th17/22 cells, and group 3 innate lymphoid cells. IL-22 signals via the IL-22 receptor 1 (IL-22R1) and the IL-10 receptor 2 (IL-10R2). As the IL-22R1/IL-10R2 heterodimer is preferentially expressed on border tissue between the host and the environment, IL-22 is believed to be involved in border defense. Epidermal keratinocytes are the first-line skin barrier and express IL-22R1/IL-10R2. IL-22 increases keratinocyte proliferation but inhibits differentiation. Aryl hydrocarbon receptor (AHR) is a chemical sensor and an essential transcription factor for IL-22 production. In addition, AHR also upregulates the production of barrier-related proteins such as filaggrin in keratinocytes, suggesting a pivotal role for the AHR-IL-22 axis in regulating the physiological skin barrier. Although IL-22 signatures are elevated in atopic dermatitis and psoriasis, their pathogenic and/or protective implications are not fully understood.

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.

Arginase-1 (Arg1) and the inducible nitric oxide synthase 2 (NOS2) compete for the common substrate L-arginine, semi-essential amino acid, and central intestinal metabolite. Both enzymes exhibit various, sometimes opposing effects on immune responses, tissue regeneration, or microbial growth and replication. In sub-mucosal tissues of patients suffering from inflammatory bowel disease (IBD), similar as in experimental colitis, the expression and activity of both enzymes, Arg1 and NOS2 are more prominent than in respective controls. Accordingly, the metabolism of L-arginine is altered in IBD patients. Thus, L-arginine represents a promising medical target for clinical intervention in these devastating diseases. Previous studies primarily focused on the host side of L-arginine metabolism. Initial reports using Arg1 inhibitors generated conflicting results in murine colitis models. Subsequently, only the generation of conditional Arg1 knockout mice allowed reliable functional analyses of Arg1 and the L-arginine metabolism in the immune system. Utilizing cell-specific conditional Arg1 knockouts, we have recently reported that Arg1, surprisingly, hampered the resolution of experimental colitis due to the restriction of the intraluminal availability of L-arginine. Reduced levels of L-arginine restrained the compositional diversity of the intestinal microbiota and subsequently the mutual metabolism between the microbiota and the host. Thus, the intraluminal microbiota represents a potential therapeutic target for L-arginine metabolism aside from host-dependent L-arginine consumption.

Viral vectors have been frequently applied for vaccine development. It has also been the case for vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to tackle the coronavirus disease 2019 (COVID-19) pandemic. A multitude of different viral vectors have been mainly targeting the SARS-CoV-2 spike (S) protein as antigen. Intramuscular injection has been most commonly used, but also intranasal administration has been tested. Adenovirus vector-based vaccines are the most advanced with several vaccines receiving Emergency Use Authorization (EUA). The simian ChAdOx1 nCoV-19 vaccine applied as a prime-boost regimen has provided 62.1–90% vaccine efficacy in clinical trials. The Ad26.COV2.S vaccine requires only one immunization to provide protection against SARS-CoV-2. The rAd26-S/rAd5-S vaccine utilizes the Ad26 serotype for the prime immunization followed by a boost with the Ad5 serotype resulting in 91.2% vaccine efficacy. All adenovirus-based vaccines are used for mass vaccinations. Moreover, vaccine candidates based on vaccinia virus and lentivirus vectors have been subjected to clinical evaluation. Among self-replicating RNA viruses, vaccine vectors based on measles virus, rhabdoviruses, and alphaviruses have been engineered and tested in clinical trials. In addition to the intramuscular route of administration vaccine candidates based on influenza viruses and adenoviruses have been subjected to intranasal delivery showing antibody responses and protection against SARS-CoV-2 challenges in animal models. The detection of novel more transmissible and pathogenic SARS-CoV-2 variants added concerns about the vaccine efficacy and needs to be monitored. Moreover, the cause of recently documented rare cases of vaccine-induced immune thrombotic thrombocytopenia (VITT) must be investigated.

The testis is designated as one of the immune previleged sites in the body and harbours a unique immunoregulatory environment, which is important for preventing an immune response against sperm antigens which otherwise are recognized as “foreign” by the immune system. The blood-testis barrier along with the unique immune cells repertoire and various immunoregulatory & immunosuppressive factors secreted by the Leydig cells, Sertoli cells and peritubular cells act in concert to maintain the tolerogenic environment in the testis. Abberations in immunotolerant mechanisms in the testis can lead to generation of anti-sperm antibodies that have an association with male infertility. It can also lead to inflammatory conditions of the male reproductive tract manifested as epididymitis and orchitis, generally due to bacterial or viral infections. In addition, non-infectious epididymitis and orchitis, having autoimmune origin have also been reported in males. While the immune privilege status of human testis protects the germ cells from an immune attack, it can also make the testis a succeptible reservoir for viruses such as human immunodeficiency virus-1, Zika virus and severe acute respiratory syndrome coronavirus-2, all of which have adverse consequences on male reproduction.

Since 2019, notable global viral outbreaks have occurred necessitating further research and healthcare system investigations. Following the coronavirus disease 2019 (COVID-19) pandemic, in 2022, whilst severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) strains evolved, monkeypox virus (MPXV) infections became more evident. MPXV is of the Orthopoxviridae genus, belonging to the family Poxviridae. Zoonotic transmission (animal-to-human transmission) may occur. The Orthopoxviridae genus includes other orthopoxviruses (OPXVs) present in animal host reservoirs that include cowpox viruses (CPXVs), vaccinia virus (VACV), and variola virus (VARV), with the latter being a causal agent of smallpox and excessive mortality. This review aims to present facts about MPXV-specific pathogenesis, epidemiology, and immunology alongside historical perspectives. MPXV was rarely reported outside Africa before April 2000. Early research since 1796 contributed towards the eradication of VARV leading to immunisation strategies. The World Health Organisation (WHO) announcement that VARV had been eradicated was confirmed in 1980. On the 23rd of July 2022, the WHO announced MPXV as a health emergency. Therefore, concern due to the propagation of MPXV causing monkeypox (mpox) disease requires clarity. Infected hosts display symptoms like extensive cellular-initiated rashes and lesions. Infection with MPXV makes it difficult to differentiate from other diseases or skin conditions. Antiviral therapeutic drugs were typically prescribed for smallpox and mpox disease; however, the molecular and immunological mechanisms with cellular changes remain of interest. Furthermore, no official authorized treatment exists for mpox disease. Some humans across the globe may be considered at risk. Historically, presenting symptoms of mpox resemble other viral diseases. Symptoms include rashes or lesions like Streptococcus, but also human herpes viruses (HHVs), including Varicella zoster virus (VZV).

Polycystic ovary syndrome (PCOS) is one of the most frequently observed endocrinopathies among women of reproductive age that redound to subfertility. The specific etiology of this heterogenic syndrome remains ambiguous. Metabolic complications, hormonal imbalance, deregulation in the immune system and their interrelationship make PCOS more complex. Hyperandrogenism and chronic low-grade inflammation modulate each other and enhance the self-perpetuation of PCOS. Even though there are many literature studies on PCOS and immune deregulation, this review focuses on the endocrine-immune nexus and how the altered endocrine system is embroiled in the immunopathology of PCOS.

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.