Search Results (86)

Background: Non-classical MHC class I molecules MICA and MICB are stress-inducible NKG2D ligands that contribute to immune surveillance, non-HLA antibody formation, and alloreactivity in solid organ and hematopoietic stem cell transplantation; population-level data for Southern Europe remain limited. Methods: High-resolution MICA and MICB genotyping was performed in 1364 unrelated individuals from southern Portugal using a hybrid-capture next-generation sequencing workflow, and allele calls were analyzed with standard population-genetic metrics (allele and genotype frequencies, heterozygosity, Hardy–Weinsberg equilibrium, and LD-like D, D′, r²) and multilocus allele presence/absence encodings explored by k-means clustering, spectral clustering, principal component analysis, t-distributed stochastic neighbor embedding, and uniform manifold approximation and projection. Results: Forty-two MICA and twenty-two MICB alleles were identified; MICA*002:01, MICA*004:01, MICA*008:01, MICA*008:04 and MICB*002:01, MICB*004:01, MICB*005:02, MICB*008:01 were most frequent, and most individuals carried at least two distinct MICA and two distinct MICB allotypes. Co-occurrence and LD-like analyses revealed conserved MICA–MICB combinations, including a strong association between MICA*009:02 and MICB*005:06, while unsupervised analyses identified partially overlapping multilocus genotype backgrounds and recurrent four-allele constellations. Conclusions: These findings provide a detailed non-classical MHC reference for southern Portugal and a multilocus framework to support interpretation of non-HLA antibodies and MICA/MICB-aware donor evaluation in selected clinical scenarios, as well as the development of machine learning-based immunologic risk models. Full article

Hepatocellular carcinoma (HCC) exhibits a striking male predominance, particularly in Hepatitis B Virus (HBV) endemic regions. While lifestyle factors and estrogen protection are traditional explanations, they fail to fully account for this disparity. This review elucidates the molecular mechanisms driving this gender gap, focusing on the interplay between the Androgen Receptor (AR), viral replication, and the suppression of NKG2D-mediated immune surveillance. We synthesized experimental and clinical findings linking AR signaling, the viral protein HBx, and the regulation of NKG2D ligands (MICA/MICB). Current evidence identifies a positive feedback loop where AR enhances HBV replication, while HBx amplifies AR activity. Crucially, this axis systematically dismantles innate immunity: AR signaling represses MICA/B transcription via miRNA networks and upregulates ADAM metalloproteases, leading to ligand shedding and the release of soluble MICA (sMICA), effectively blinding Natural Killer (NK) cells. We propose that historical failures of anti-androgen monotherapy likely stemmed from ignoring this immune modulation. Consequently, targeting the AR-NKG2D axis represents a promising strategy to sensitize tumors to immunotherapy, suggesting that future therapeutic approaches should combine AR modulation with immune checkpoint inhibitors or shedding-blockade. Full article

Breast cancer (BC) is a global health problem. BC is a biologically heterogeneous disease in which novel immunotherapeutic strategies are needed, particularly in the metastatic setting. The NKG2D/NKG2D ligand (NKG2DL) axis is a key component of innate antitumor immunity and represents a potential therapeutic target, but its relevance in BC has not been fully characterized. We performed an in silico analysis of NKG2DL expression in BC cell lines, healthy breast tissue, and tumor samples using publicly available transcriptomic databases (DSMZCellDive, ShinyTHOR, GTEx, TCGA, Human Protein Atlas), complemented by survival analyses from TCGA and KMPlot and a narrative review of the literature. NKG2DL transcripts were consistently expressed in BC cell lines and tumor tissues, with higher expression observed in ductal histology, higher tumor stage, and basal molecular subtype. Survival analyses showed heterogeneous and generally weak associations between individual NKG2DLs and clinical outcomes. In silico proteomics data are scarce, but the narrative review showed that NKG2DLs are expressed by immunohistochemistry in tumor tissues but absent in surrounding healthy tissues. The literature review also revealed concomitant dysfunction of NKG2D+ effector cells due to multiple resistance mechanisms (including ligand shedding). We also review potential therapeutic approaches. Full article

Major histocompatibility complex class I chain-related gene A (MICA) is a non-classical MHC-I molecule essential for immune surveillance, yet its intracellular maturation remains poorly understood. We show that MICA is predominantly retained intracellularly in melanoma cells and colocalizes with the endoplasmic reticulum chaperone calreticulin (CRT). Notably, MICA also colocalizes with CRT in healthy skin. Immunoprecipitation assays reveal that CRT preferentially associates with a low-molecular-weight form of MICA. Recombinant protein assays and in silico analyses support direct interaction between CRT and non-glycosylated MICA, but not with fully glycosylated eukaryotic MICA. These findings identify CRT-dependent retention of MICA as a physiological checkpoint that may be dysregulated in melanoma to promote immune evasion. Full article

Natural killer (NK) cells are the main cytotoxic lymphocytes of the natural immune system, which play an important role in tumor immune surveillance and anti-viral response. The surface receptor NKG2D can recognize NKG2D ligands on the surface of tumor or metabolism-stressed cells, thereby activating immune responses and mediating cytotoxicity and anti-tumor activity of NK cells. However, NKG2D-positive NK cells are regulated by metabolites, and play a negative role in metabolic diseases. Various metabolites, including lipids, reactive oxygen species (ROS), glucose and amino acids, regulate NKG2D expression and NK cell activity and decide the immune microenvironment of pathological tissue. Thus, targeted therapies based on NKG2D-positive NK cell have entirely different strategies in the treatment of tumor or metabolic diseases. This article focuses on the metabolic regulation of NKG2D-positive NK cells and their opposite roles in disease progression, including of cancer and metabolic disease. In the future, in-depth studies of the regulatory mechanisms of the NKG2D signaling pathway by metabolites and the optimization of the safety and efficacy of targeted therapeutic strategies will lead to new breakthroughs in the treatment of tumors and metabolic diseases, providing patients with more effective treatment options. Full article

Background: The emergence of the COVID-19 pandemic has accelerated research into diverse immune response mechanisms. One key area of interest is the regulation of cytotoxic activity by Natural Killer (NK) cells. These cells rely on a dynamic interplay between activating and inhibitory surface receptors that recognize specific ligands on target cells. Among these, receptors from the NKG2 family are particularly important, as maintaining their proper balance and function is essential for controlling NK cell cytotoxicity. Methods: In this study we employed qPCR to assess the genetic variability using single-nucleotide polymorphisms (SNPs) of NKG2A and NKG2D receptors and their ligands HLA-E and MICA/MICB. NKG2C deletion was determined by PCR-SSP, and serum-soluble levels of HLA-E and MICA/MICB molecules were measured by ELISA and Luminex methods. Results: Genotyping studies revealed that both NKG2A rs7301582 T and HLA-E rs1264457 A (HLA-E*01:01) alleles were predominant among infected individuals (OR = 2.21, p = 0.0258 and OR = 2.84, p = 0.0257, respectively). In contrast to MICB rs1065075 A, the MICA rs1051792 A (129Met) allele was most commonly found in hospitalized patients (OR = 14.95, p = 0.0114). The presence of the NKG2C del variant tended to be associated with an increased risk of SARS-CoV-2 infection (OR = 2.02, p = 0.0694). Moreover, higher concentrations of serum-soluble MICB was detected in infected individuals as compared to the control group (p = 0.008). Conclusions: Genetic variability of NK cell receptors and ligands as well as serum levels of their soluble forms showed associations with the risk of development of COVID-19 and the severity of its symptoms. Full article

Despite advances in immunotherapy, the treatment of breast cancer still remains a major global problem. In a previous study, we showed that co-blockade of Interleukin-33/ST2 and Programmed death-1/Programmed death-ligand (PD-1/PD-L) signaling pathways strongly slows progression by enhancing the antitumor capacity of natural killer (NK) cells. The main aim of this study is to elucidate the exact effect of co-blockade on the T lymphocyte and macrophage effector cells. 4T1 cells were used to induct breast cancer in female BALB/C and BALB/C ST2^−/− mice. The mice, both BALB/C and BALB/C ST2^−/−, were treated with anti-PD-1 antibody on certain days. After the mice were sacrificed, T cells and macrophages were analyzed using flow cytometry; dual co-blockade increased significantly the percentage of M1 macrophages in the tumor microenvironment, followed by an increase in expression of CD86⁺ and TNFα⁺. T cell accumulation was significantly higher in the spleen and within the tumor microenvironment, with elevation in activation markers such as Interleukin-17, CD69, NKG2D, and FasL and a decrease in Interleukin-10 and FoxP3 expression. Co-blockade of the PD-1/PD-L axes and IL-33/ST2 axes shows promising results in reestablishing an effective immune response and offers a new perspective on improving immune response to breast carcinoma. Full article

Background/Objectives: Chimeric Antigen Receptor (CAR)-T cell therapy has demonstrated impressive clinical results against hematological malignancies. However, currently commercialized CAR-T therapies are designed for autologous use, which entails some disadvantages, including high costs, manufacturing delays, complex standardization, and frequent production failures due to patient T cell dysfunction. Moreover, their CARs target one specific antigen, increasing the probability of antigen-negative tumor relapses. To overcome these limitations, we developed a novel NKG2D CAR-T cell therapy for allogeneic use with broad target specificity, as this CAR targets eight different ligands commonly upregulated in both solid and hematological tumors. Additionally, the manufacturing process was optimized to improve the phenotypic characteristics of the final product. Methods: Multiplex CRISPR/Cas9 technology was applied to eliminate the expression of TCR and HLA class I complexes in healthy donor T cells to reduce the risk of graft-versus-host disease and immune rejection, respectively, as well as lentiviral transduction for introducing the second-generation NKG2D-CAR. Moreover, we sought to optimize this manufacturing process by comparing the effect of different culture interleukin supplementations (IL-2, IL-7/IL-15 or IL-7/IL-15/IL-21) on the phenotypic and functional characteristics of the product obtained. Results: Our results showed that the novel CAR-T cells effectively targeted cervicouterine and colorectal cancer cells, and that those manufactured with IL-7/IL-15/IL-21 supplementation showed the most suitable characteristics among the conditions tested, considering genetic modification efficiency, cell proliferation, antitumor activity and proportion of the stem cell memory T cell subset, which is associated with enhanced in vivo CAR-T cell survival, expansion and long-term persistence. Conclusions: In summary, this new prototype of NKG2D CAR-T cell therapy for allogeneic use represents a promising universal treatment for a wide range of tumor types. Full article

Chimeric Antigen Receptor (CAR)-T cell therapy has transformed the treatment landscape of cancer, yet major challenges remain in enhancing efficacy, reducing adverse effects, and expanding accessibility. Autologous CAR-T cells, derived from individual patients, have achieved remarkable clinical success in hematologic malignancies; however, their highly personalized nature limits scalability, increases costs, and delays timely treatment. Allogeneic CAR-T cells generated from healthy donors provide an “off-the-shelf” alternative but face two critical immune barriers: graft-versus-host disease (GvHD), caused by donor T-cell receptor (TCR) recognition of host tissues, and host-versus-graft rejection, mediated by recipient immune responses against donor HLA molecules. Recent advances in genome engineering, particularly Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9, allow precise modification of donor T cells to overcome these limitations. For example, TRAC gene knockout eliminates TCR expression, preventing GvHD, while disruption of HLA molecules reduces immunogenicity without impairing cytotoxicity. Beyond hematologic cancers, CRISPR-edited allogeneic CAR-T cells targeting the NKG2D receptor have shown promise in preclinical studies and early-phase trials. NKG2D CAR-T cells recognize stress ligands (MICA/B, ULBP1–6) expressed on over 80% of diverse solid tumors, including pancreatic and ovarian cancers, thereby broadening therapeutic applicability. Nevertheless, the genomic editing process carries risks of off-target effects, including potential disruption of tumor suppressor genes and oncogenes, underscoring the need for stringent safety and quality control. This review examines the distinguishing features of allogeneic versus autologous CAR-T therapy, with a particular focus on NKG2D-based allogeneic CAR-T approaches for solid tumors. We summarize current strategies to mitigate immune barriers, discuss practical manufacturing challenges, and analyze available clinical data on NKG2D CAR-T trials. Collectively, these insights underscore both the promise and the hurdles of developing safe, universal, and scalable allogeneic CAR-T therapies for solid malignancies. Full article

This study investigated the expression of immune checkpoint molecules on CD4⁺ and CD4⁻ NKT cell subpopulations throughout healthy pregnancy trimesters and in non-pregnant condition to understand their role in maternal–fetal immunotolerance. Using flow cytometry, we found that CD4⁻ NKT cells significantly outnumbered CD4⁺ NKT cells in all investigated groups. In the case of the immune checkpoint molecules, PD-1 receptor expression was significantly lower in CD4⁻ NKT cells compared to CD4⁺ counterpart cells only in non-pregnant women, while the PD-L1 ligand expression on CD4⁺ NKT cells significantly decreased in the third trimester. In contrast, LAG-3 and Galectin-3 expressions remained stable across all subsets and trimesters. For the TIGIT/CD226 axis, CD226 expression was significantly higher in CD4⁺ NKT cells in the third trimester and in non-pregnant women. The two ligands CD112 and CD155 were consistently lower on CD4⁻ NKT cells across all groups. The activating receptor NKG2D was significantly higher on CD4⁻ NKT cells in all examined cohorts. These findings suggest that CD4⁺ NKT cells tend towards a more tolerogenic phenotype, while CD4⁻ NKT cells maintain a balanced cytotoxic potential with reduced immunoregulation function. The dynamic regulation of immune checkpoints on NKT cell subsets, particularly the downregulation of PD-L1 and CD226 in late pregnancy, highlights their fine-tuned role in balancing maternal–fetal immune tolerance with readiness for parturition. Full article

Multiple myeloma (MM or plasma cell myeloma) is a heterogenous B-cell malignant tumor that typically exhibits a high recurrence rate, resistance to drugs, and molecular diversity of tumor subclones. Given the limited efficacy of standard therapy options, cellular immunotherapy featuring a chimeric antigen receptor (CAR) has proven tangible potential in treatment for relapsed and refractory forms of MM. The rational choice of a tumor target which shows high selectivity, stable expression, and biological significance is key to the successful implementation of CAR therapy. This review has summarized and analyzed data from the literature on biological properties, the features of expression, and the clinical development stages of CAR cell products for MM treatment which target BCMA, GPRC5D, FcRH5, SLAMF7, CD38, CD138, TACI, APRIL, CD19, TNFR2, CD44v6, CD70, NKG2D ligands, etc. Special focus is on strategic approaches to overcoming antigenic escape, such as multi-specific CAR constructs, logical activation sequences, and controlled safety systems. The analysis underscores the need for integrating the molecular selection of targets with cutting-edge bioengineering solutions as a key trend for raising the efficacy, stability, and safety of cellular therapy in the case of MM. Full article

Malignant tumors of the digestive system are widespread and pose a serious threat to humans. Immune escape is an important factor promoting the deterioration of malignant tumors in the digestive system. Natural killer cells (NK cells) are key members of the anti-tumor and immune surveillance system, mainly exerting cytotoxic effects by binding to the activating receptor natural killer cell group 2D (NKG2D) on their cell surface with the corresponding ligands (major histocompatibility complex class I chain-related protein A/B, MICA/B) on the surface of tumor cells. Malignant tumors of epithelial origin usually highly express NKG2D ligands such as MICA, which can attract NK cells to kill tumor cells and also serve as an important basis for NK cell-based immunotherapy. Tumor cells highly express hypoxia-inducible factor-1α (HIF-1α), which promotes the expression of matrix metalloproteinases (MMPs) and a disintegrin and metalloproteinases (ADAMs). These metalloproteinases hydrolyze MICA and other ligands on the surface of tumor cells to generate soluble molecules. These soluble ligands, when binding to NKG2D, cannot activate NK cells and also block the binding of NKG2D to MICA on the surface of tumor cells, enabling tumor cells to evade the killing effect of NK cells. Almost all organs in the digestive system originate from epithelial tissue, so the soluble ligands generated by the HIF-1α/MMPs or HIF-1α/ADAMs signaling pathways play a crucial role in evading NK cell killing. A comprehensive understanding of this immune escape process is helpful for a deeper understanding of the molecular mechanism of NK cell anti-tumor activity. This article reviews the molecular mechanisms of common digestive system malignancies evading NK cell killing, providing new insights into the mechanism of tumor immune escape. Full article

UL16-binding protein 2 (ULBP2), a ligand for the activating receptor NKG2D, plays a dual role in tumor immunity, promoting immune activation or suppression, depending on the context. To investigate its impact on CD4⁺CD25⁺ T cell-targeted immunotherapies, we used a syngeneic CT26 colon cancer model engineered to express ULBP2 and compared tumor growth and tumor-infiltrating lymphocyte (TIL) profiles in control and ULBP2-expressing tumors treated with anti-CD4, anti-CD25, or anti-CTLA-4 antibodies. Tumor growth was uniformly assessed on day 21 post-transplantation, and TIL analysis was performed in groups with evaluable residual tumors. Anti-CD4 antibody significantly suppressed tumor growth in mock-transfected tumors, while no significant suppression was observed in ULBP2-expressing tumors. Anti-CD25 antibody had limited efficacy in mock tumors and tended to promote tumor growth in ULBP2-expressing tumors. Following these treatments, ULBP2 expression was associated with reduced NKG2D expression in CD8⁺ effector memory T cells, particularly PD-1^high subsets. In contrast, anti-CTLA-4 antibody treatment induced marked tumor regression irrespective of ULBP2 expression. These findings suggest that ULBP2–NKG2D signaling may contribute to altered CD8⁺ T cell phenotypes under T cell-modulatory conditions, potentially impacting the outcome of CD4⁺CD25⁺ T cell-targeted therapies and providing insights for optimizing immunotherapeutic strategies. Full article

UL-16 binding protein 2 (ULBP2), a human NKG2D ligand, has been identified as a poor prognostic factor in several cancers based on recent comprehensive analyses of immune-related genes using the Cancer Genome Atlas datasets. Despite its clinical significance, the functional role of ULBP2 in vivo remains largely unknown. In this study, we investigated the role of ULBP2 in modulating anti-tumor immunity using murine melanoma cell lines engineered to stably express surface-expressed or soluble ULBP2. Subcutaneous transplantation of ULBP2-expressing melanoma cells into syngeneic mice resulted in accelerated tumor growth, mediated by surface-expressed ULBP2, through the suppression of NKG2D-dependent immune responses. In vitro experiments revealed that sustained exposure to tumor-expressed ULBP2 reduced NKG2D expression and cytotoxic activity of splenocytes. In contrast, soluble ULBP2 did not significantly affect tumor growth or immune responses. These findings suggest that surface-expressed ULBP2 plays a pivotal role in tumor immune evasion and highlight its potential as a therapeutic target to enhance anti-tumor immunity. Full article

The immune system’s ability to detect and eliminate transformed cells is a critical factor in suppressing cancer development. However, immune surveillance in tumors is often disrupted by various immune escape mechanisms, many of which remain poorly understood. The Natural Killer Group 2D (NKG2D) receptor is an activating receptor expressed on natural killer (NK) cells and cytotoxic T lymphocytes. It can recognize and bind with varying affinities to a wide range of structurally diverse ligands, including MHC class I chain-related proteins A and B (MICA and MICB) and members of the ULBP family (ULBP1-6). The expression of these ligands plays a crucial role in immune antitumor responses and cancer immunoevasion mechanisms. Some evidence suggests that functional polymorphisms in the NKG2D receptor and the genes encoding its ligands significantly influence HLA-independent cancer immunosurveillance. Consequently, the NKG2D-NKG2D ligands (NKG2DLs) axis represents a promising target for developing novel therapeutic strategies. This review aims to provide a general overview of the role of NKG2D and its ligands in various malignancies and explore their potential in advancing personalized cancer treatment protocols. Full article