COVID-19 and the human innate immune system.

The introduction of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) into the human population represents a tremendous medical and economic crisis. Innate immunity-as the first line of defense of our immune system-plays a central role in combating this novel virus. Here, we provide a conceptual framework for the interaction of the human innate immune system with SARS-CoV-2 to link the clinical observations with experimental findings that have been made during the first year of the pandemic. We review evidence that variability in innate immune system components among humans is a main contributor to the heterogeneous disease courses observed for coronavirus disease 2019 (COVID-19), the disease spectrum induced by SARS-CoV-2. A better understanding of the pathophysiological mechanisms observed for cells and soluble mediators involved in innate immunity is a prerequisite for the development of diagnostic markers and therapeutic strategies targeting COVID-19. However, this will also require additional studies addressing causality of events, which so far are lagging behind.

Jagged2 targeting in lung cancer activates anti-tumor immunity via Notch-induced functional reprogramming of tumor-associated macrophages.

Signaling through Notch receptors intrinsically regulates tumor cell development and growth. Here, we studied the role of the Notch ligand Jagged2 on immune evasion in non-small cell lung cancer (NSCLC). Higher expression of JAG2 in NSCLC negatively correlated with survival. In NSCLC pre-clinical models, deletion of Jag2, but not Jag1, in cancer cells attenuated tumor growth and activated protective anti-tumor T cell responses. Jag2-/- lung tumors exhibited higher frequencies of macrophages that expressed immunostimulatory mediators and triggered T cell-dependent anti-tumor immunity. Mechanistically, Jag2 ablation promoted Nr4a-mediated induction of Notch ligands DLL1/4 on cancer cells. DLL1/4-initiated Notch1/2 signaling in macrophages induced the expression of transcription factor IRF4 and macrophage immunostimulatory functionality. IRF4 expression was required for the anti-tumor effects of Jag2 deletion in lung tumors. Antibody targeting of Jagged2 inhibited tumor growth and activated IRF4-driven macrophage-mediated anti-tumor immunity. Thus, Jagged2 orchestrates immunosuppressive systems in NSCLC that can be overcome to incite macrophage-mediated anti-tumor immunity.

GPNMB+ Gal-3+ hepatic parenchymal cells promote immunosuppression and hepatocellular carcinogenesis.

Hepatocellular carcinoma (HCC) formation is a multi-step pathological process that involves evolution of a heterogeneous immunosuppressive tumor microenvironment. However, the specific cell populations involved and their origins and contribution to HCC development remain largely unknown. Here, comprehensive single-cell transcriptome sequencing was applied to profile rat models of toxin-induced liver tumorigenesis and HCC patients. Specifically, we identified three populations of hepatic parenchymal cells emerging during HCC progression, termed metabolic hepatocytes (HCMeta ), Epcam+ population with differentiation potential (EP+Diff ) and immunosuppressive malignant transformation subset (MTImmu ). These distinct subpopulations form an oncogenic trajectory depicting a dynamic landscape of hepatocarcinogenesis, with signature genes reflecting the transition from EP+Diff to MTImmu . Importantly, GPNMB+ Gal-3+ MTImmu cells exhibit both malignant and immunosuppressive properties. Moreover, SOX18 is required for the generation and malignant transformation of GPNMB+ Gal-3+ MTImmu cells. Enrichment of the GPNMB+ Gal-3+ MTImmu subset was found to be associated with poor prognosis and a higher rate of recurrence in patients. Collectively, we unraveled the single-cell HCC progression atlas and uncovered GPNMB+ Gal-3+ parenchymal cells as a major subset contributing to the immunosuppressive microenvironment thus malignance in HCC.

New Therapeutic Approaches to Large-Vessel Vasculitis.

Giant cell arteritis (GCA) and Takayasu arteritis (TAK) are large-vessel vasculitides affecting the aorta and its branches. Arterial damage from these diseases may result in ischemic complications, aneurysms, and dissections. Despite their similarities, the management of GCA and TAK differs. Glucocorticoids are used frequently but relapses are common, and glucocorticoid toxicity contributes to significant morbidity. Conventional immunosuppressive therapies can be beneficial in TAK, though their role in the management of GCA remains unclear. Tumor necrosis factor inhibitors improve remission rates and appear to limit vascular damage in TAK; these agents are not beneficial in GCA. Tocilizumab is the first biologic glucocorticoid-sparing agent approved for use in GCA and also appears to be effective in TAK. A better understanding of the pathogenesis of both conditions and the availability of targeted therapies hold much promise for future management.

Armored bicistronic CAR T cells with dominant-negative TGF-ß receptor II to overcome resistance in glioblastoma.

Chimeric antigen receptor (CAR) T cells have shown significant efficacy in hematological diseases. However, CAR T therapy has demonstrated limited efficacy in solid tumors, including glioblastoma (GBM). One of the most important reasons is the immunosuppressive tumor microenvironment (TME), which promotes tumor growth and suppresses immune cells used to eliminate tumor cells. The human transforming growth factor ß (TGF-ß) plays a crucial role in forming the suppressive GBM TME and driving the suppression of the anti-GBM response. To mitigate TGF-ß-mediated suppressive activity, we combined a dominant-negative TGF-ß receptor II (dnTGFßRII) with our previous bicistronic CART-EGFR-IL13Rα2 construct, currently being evaluated in a clinical trial, to generate CART-EGFR-IL13Rα2-dnTGFßRII, a tri-modular construct we are developing for clinical application. We hypothesized that this approach would more effectively subvert resistance mechanisms observed with GBM. Our data suggest that CART-EGFR-IL13Rα2-dnTGFßRII significantly augments T cell proliferation, enhances functional responses, and improves the fitness of bystander cells, particularly by decreasing the TGF-ß concentration in a TGF-ß-rich TME. In addition, in vivo studies validate the safety and efficacy of the dnTGFßRII cooperating with CARs in targeting and eradicating GBM in an NSG mouse model.

An inhibitor of leukotriene-A4 hydrolase from bat salivary glands facilitates virus infection.

SignificanceAn immunosuppressant protein (MTX), which facilitates virus infection by inhibiting leukotriene A4 hydrolase (LTA4H) to produce the lipid chemoattractant leukotriene B4 (LTB4), was identified and characterized from the submandibular salivary glands of the bat Myotis pilosus. To the best of our knowledge, this is a report of an endogenous LTA4H inhibitor in animals. MTX was highly concentrated in the bat salivary glands, suggesting a mechanism for the generation of immunological privilege and immune tolerance and providing evidence of viral shedding through oral secretions. Moreover, given that the immunosuppressant MTX selectively inhibited the proinflammatory activity of LTA4H, without affecting its antiinflammatory activity, MTX might be a potential candidate for the development of antiinflammatory drugs by targeting the LTA4-LTA4H-LTB4 inflammatory axis.

IKKα-deficient lung adenocarcinomas generate an immunosuppressive microenvironment by overproducing Treg-inducing cytokines.

The tumor microenvironment (TME) provides potential targets for cancer therapy. However, how signals originating in cancer cells affect tumor-directed immunity is largely unknown. Deletions in the CHUK locus, coding for IκB kinase α (IKKα), correlate with reduced lung adenocarcinoma (ADC) patient survival and promote KrasG12D-initiated ADC development in mice, but it is unknown how reduced IKKα expression affects the TME. Here, we report that low IKKα expression in human and mouse lung ADC cells correlates with increased monocyte-derived macrophage and regulatory T cell (Treg) scores and elevated transcription of genes coding for macrophage-recruiting and Treg-inducing cytokines (CSF1, CCL22, TNF, and IL-23A). By stimulating recruitment of monocyte-derived macrophages from the bone marrow and enforcing a TNF/TNFR2/c-Rel signaling cascade that stimulates Treg generation, these cytokines promote lung ADC progression. Depletion of TNFR2, c-Rel, or TNF in CD4+ T cells or monocyte-derived macrophages dampens Treg generation and lung tumorigenesis. Treg depletion also attenuates carcinogenesis. In conclusion, reduced cancer cell IKKα activity enhances formation of a protumorigenic TME through a pathway whose constituents may serve as therapeutic targets for KRAS-initiated lung ADC.

Identification of rat Vstm1 with conservative anti-inflammatory effect between rat and human homologs.

Human VSTM1 (also known as SIRL1) is an inhibitory immune checkpoint receptor involved in leukocyte activation. Identification of the homologous genes in other species, such as mice and rats, will undoubtedly contribute to functional studies and clinical applications. Here, we successfully cloned the Vstm1 gene in rats, as supported by high-throughput sequencing data. However, Vstm1 is degenerated to a pseudogene in the mouse genome. Rat Vstm1 mRNA contains a complete open reading frame (ORF) of 630 nucleotides encoding 209 amino acids. Rat Vstm1 is highly expressed in bone marrow, especially in granulocytes. The expression levels of Vstm1 gradually increase with the development of granulocytes in bone marrow but are downregulated in response to inflammatory stimuli. Rat VSTM1 does not have an immunoreceptor tyrosine-based inhibitory motif (ITIM), however, it shows a conservative function of inflammatory inhibition with human VSTM1, and both are anti-correlated with many inflammatory cytokines, such as IL-1α and TNF-α. In bone marrow-derived macrophages (BMDMs), either rat or human VSTM1 suppressed the secretion of inflammatory cytokines in response to LPS stimulation. Further analysis in lung cancer microenvironment revealed that VSTM1 is mainly expressed in myeloid cells, anti-correlated with inflammatory cytokines and associated with tumor development and metastasis.

Immunosuppressive Ability of Trichinella spiralis Adults Can Ameliorate Type 2 Inflammation in a Murine Allergy Model.

BACKGROUND: There is an increase in the global incidence of allergies. The hygiene hypothesis and the old friend hypothesis reveal that helminths are associated with the prevalence of allergic diseases. The therapeutic potential of Trichinella spiralis is recognized; however, the stage at which it exerts its immunomodulatory effect is unclear. METHODS: We evaluated the differentiation of bone marrow-derived macrophages stimulated with T spiralis excretory-secretory products. Based on an ovalbumin-induced murine model, T spiralis was introduced during 3 allergy phases. Cytokine levels and immune cell subsets in the lung, spleen, and peritoneal cavity were assessed. RESULTS: We found that T spiralis infection reduced lung inflammation, increased anti-inflammatory cytokines, and decreased Th2 cytokines and alarms. Recruitment of eosinophils, CD11b+ dendritic cells, and interstitial macrophages to the lung was significantly suppressed, whereas Treg cells and alternatively activated macrophages increased in T spiralis infection groups vs the ovalbumin group. Notably, when T spiralis was infected prior to ovalbumin challenge, intestinal adults promoted proportions of CD103+ dendritic cells and alveolar macrophages. CONCLUSIONS: T spiralis strongly suppressed type 2 inflammation, and adults maintained lung immune homeostasis.

Incidence and risk factors for invasive fungal infections in patients initiating TNF-alpha inhibitors for inflammatory bowel disease and rheumatoid arthritis.

In a commercial claims database analysis, <0.5% of patients with inflammatory bowel disease or rheumatoid arthritis developed an IFI within one year of initiating TNF-alpha therapy. Histoplasmosis was the most common IFI type. Overall IFI incidence varied based on region, underlying conditions, and use of certain immunosuppressive medications.

Comparing the prognostic performance of iBOX and biopsy-proven acute rejection for long-term kidney graft survival.

Biopsy-proven acute rejection (BPAR) occurs in approximately 10% of kidney transplant recipients in the first year, making superiority trials unfeasible. iBOX, a quantitative composite of estimated glomerular filtration rate, proteinuria, antihuman leukocyte antigen donor-specific antibody, and + full/- abbreviated kidney histopathology, is a new proposed surrogate endpoint. BPAR's prognostic ability was compared with iBOX in a pooled cohort of 1534 kidney transplant recipients from 4 data sets, including 2 prospective randomized controlled trials. Discrimination analyses showed mean c-statistic differences between both iBOX compared with BPAR of 0.25 (95% confidence interval: 0.17-0.32) for full iBOX and 0.24 (95% confidence interval: 0.16-0.32) for abbreviated iBOX, indicating statistically significantly higher c-statistic values for the iBOX prognosis of death-censored graft survival. Mean (± standard error) c-statistics were 0.81 ± 0.03 for full iBOX, 0.80 ± 0.03 for abbreviated iBOX, and 0.57 ± 0.03 for BPAR. In calibration analyses, predicted graft loss events from both iBOX models were not significantly different from those observed. However, for BPAR, the predicted events were significantly (P < .01) different (observed: 64; predicted: 70; full iBOX: 76; abbreviated iBOX: 173 BPAR). IBOX at 1-year posttransplant is superior to BPAR in the first year posttransplant in graft loss prognostic performance, providing valuable additional information and facilitating the demonstration of superiority of novel immunosuppressive regimens.

Incidence and predictors of hepatocellular carcinoma in patients with autoimmune hepatitis.

BACKGROUND AND AIMS: Autoimmune hepatitis (AIH) is a rare chronic liver disease of unknown aetiology; the risk of hepatocellular carcinoma (HCC) remains unclear and risk factors are not well-defined. We aimed to investigate the risk of HCC across a multicentre AIH cohort and to identify predictive factors. METHODS: We performed a retrospective, observational, multicentric study of patients included in the International Autoimmune Hepatitis Group Retrospective Registry. The assessed clinical outcomes were HCC development, liver transplantation, and death. Fine and Gray regression analysis stratified by centre was applied to determine the effects of individual covariates; the cumulative incidence of HCC was estimated using the competing risk method with death as a competing risk. RESULTS: A total of 1,428 patients diagnosed with AIH from 1980 to 2020 from 22 eligible centres across Europe and Canada were included, with a median follow-up of 11.1 years (interquartile range 5.2-15.9). Two hundred and ninety-three (20.5%) patients had cirrhosis at diagnosis. During follow-up, 24 patients developed HCC (1.7%), an incidence rate of 1.44 cases/1,000 patient-years; the cumulative incidence of HCC increased over time (0.6% at 5 years, 0.9% at 10 years, 2.7% at 20 years, and 6.6% at 30 years of follow-up). Patients who developed cirrhosis during follow-up had a significantly higher incidence of HCC. The cumulative incidence of HCC was 2.6%, 4.6%, 5.6% and 6.6% at 5, 10, 15, and 20 years after the development of cirrhosis, respectively. Obesity (hazard ratio [HR] 2.94, p = 0.04), cirrhosis (HR 3.17, p = 0.01), and AIH/PSC variant syndrome (HR 5.18, p = 0.007) at baseline were independent risk factors for HCC development. CONCLUSIONS: HCC incidence in AIH is low even after cirrhosis development and is associated with risk factors including obesity, cirrhosis, and AIH/PSC variant syndrome. IMPACT AND IMPLICATIONS: The risk of developing hepatocellular carcinoma (HCC) in individuals with autoimmune hepatitis (AIH) seems to be lower than for other aetiologies of chronic liver disease. Yet, solid data for this specific patient group remain elusive, given that most of the existing evidence comes from small, single-centre studies. In our study, we found that HCC incidence in patients with AIH is low even after the onset of cirrhosis. Additionally, factors such as advanced age, obesity, cirrhosis, alcohol consumption, and the presence of the AIH/PSC variant syndrome at the time of AIH diagnosis are linked to a higher risk of HCC. Based on these findings, there seems to be merit in adopting a specialized HCC monitoring programme for patients with AIH based on their individual risk factors.

Clinical impact and characteristics of erythroid dysplasia in adult aplastic anaemia: Results from a multicentre registry.

Morphological dysplasia in haematopoietic cells, defined by a 10% threshold in each lineage, is one of the diagnostic criteria for myelodysplastic neoplasms. Dysplasia limited to the erythroid lineage has also been reported in some cases of aplastic anaemia (AA); however, its significance remains unclear. We herein examined the impact of erythroid dysplasia on immunosuppressive therapy responses and survival in AA patients. The present study included 100 eligible AA patients without ring sideroblasts. Among them, 32 had dysplasia in the erythroid lineage (AA with minimal dysplasia [mini-D]). No significant sex or age differences were observed between AA groups with and without erythroid dysplasia. In severe/very severe AA and non-severe AA patients, a response to anti-thymocyte globulin + ciclosporin within 12 months was observed in 80.0% and 60.0% of AA with mini-D and 42.9% and 90.0% of those without dysplasia, with no significant difference (p = 0.29 and p = 0.24 respectively). Overall survival and leukaemia-free survival did not significantly differ between the groups. Collectively, the present results indicate that the presence of erythroid dysplasia did not significantly affect clinical characteristics or outcomes in AA patients, suggesting that its presence in AA is acceptable. Therefore, erythroid dysplasia should not exclude an AA diagnosis.

Acidity promotes the differentiation of immunosuppressive regulatory T cells.

The metabolic milieu is emerging as a major contributing factor in the maintenance of the immunosuppressive microenvironment within tumors. In particular, the presence of lactic acid produced by highly glycolytic cancer cells is known to suppress antitumor immune cell subsets while promoting immunosuppressive cell populations, such as regulatory T cells (Tregs). Unlike conventional T cells, Tregs have a unique, potent ability to take up lactic acid to fuel both mitochondrial metabolism and gluconeogenesis, thus supporting suppressive function and proliferation. In this issue of the European Journal of Immunology [Eur. J. Immunol. 2023.53:2250258], Rao et al. uncover a novel mechanism by which lactic acid can support Treg accumulation within tumors in mice. This study shows that lactic acid, through a pH-dependent mechanism rather than lactate itself, promotes TGFß-induced differentiation of Tregs from conventional CD4+ T cells. These findings build on the already multifaceted role of lactic acid in maintaining an immunosuppressive tumor microenvironment.

A Metal-Phenolic Network-Enabled Nanoadjuvant to Modulate Immune Responses.

The presence of hierarchical suppressive pathways in the immune system combined with poor delivery efficiencies of adjuvants and antigens to antigen-presenting cells are major challenges in developing advanced vaccines. The present study reports a nanoadjuvant constructed using aluminosilicate nanoparticles (as particle templates), incorporating cytosine-phosphate-guanosine (CpG) oligonucleotides and small-interfering RNA (siRNA) to counteract immune suppression in antigen-presenting cells. Furthermore, the application of a metal-phenolic network (MPN) coating, which can endow the nanoparticles with protective and bioadhesive properties, is assessed with regard to the stability and immune function of the resulting nanoadjuvant in vitro and in vivo. Combining the adjuvanticity of aluminum and CpG with RNA interference and MPN coating results in a nanoadjuvant that exhibits greater accumulation in lymph nodes and elicits improved maturation of dendritic cells in comparison to a formulation without siRNA or MPN, and with no observable organ toxicity. The incorporation of a model antigen, ovalbumin, within the MPN coating demonstrates the capacity of MPNs to load functional biomolecules as well as the ability of the nanoadjuvant to trigger enhanced antigen-specific responses. The present template-assisted fabrication strategy for engineering nanoadjuvants holds promise in the design of delivery systems for disease prevention, as well as therapeutics.

Aberrant baseline cytokine profile in patients with newly diagnosed acquired aplastic anaemia correlates with disease severity and the treatment response.

BACKGROUND: Immune dysregulation is crucial in the pathogenesis of acquired aplastic anaemia (aAA). There is paucity of data regarding correlation of baseline cytokine profile with treatment response in aAA. OBJECTIVE: Present prospective case-control study aimed to correlate the baseline cytokines in patients with aAA with the treatment response. METHODS: Fifty-one patients with newly-diagnosed aAA > 13 years of either sex were enrolled over 1.5 years. Twenty age-and sex-matched healthy controls (HC) were also included. The cytokine profile (IL-2, 4, 6, 8, 10, 17, IFN-γ and TNF-α) in the peripheral blood plasma of aAA patients was performed at the baseline using cytometric bead analysis. The cytokine levels were compared with HC and correlated with response to immunosuppressive therapy (IST) at 3-months. RESULTS: The median age of cases was 29 years (range,13-74). The cases had higher mean levels of IL2 (p = 0.326), IL4 (p = 0.038), IL6 (p = 0.000), IL10 (p = 0.002), TNF-α (p = 0.302), IFN-γ (p = 0.569) and IL-17 (p = 0.284) than the HC. The baseline levels of all the cytokines were higher (statistically non-significant) among responders (n = 13) than the non-responders (n = 14) to IST. CONCLUSIONS: Baseline cytokine profile in patients with aAA might predict response to the IST. Larger studies are needed to validate our results.

Unveiling Immunological Signatures and Predictors of Response to Immunosuppressive Therapy in Acquired Aplastic Anaemia".

Acquired Aplastic Anaemia (AA) often results from immune destruction of hematopoietic stem and progenitor cells. However, only 60-70% of patients with AA respond to immunosuppressive therapy (IST). There is lack of strong predictive marker for response to IST which can help therapy. Our study sought to pinpoint unique immune markers in AA patients and validate established predictors for response to IST. We enrolled 51 severe AA patients and analyzed 57 immunological parameters via flow cytometry. Additionally, we measured paroxysmal nocturnal hemoglobinuria (PNH) clone, telomere length, and thrombopoietin (TPO) levels prior to IST. After a 6-months follow-up, response was observed. Patients with AA had a distinct immunological signature characterized by absolute lymphopenia, skewed CD4/CD8 ratio with expansion of CD8 T cells with activated and senescent phenotype. Treg counts were reduced, while proportion of Treg A and B was comparable to controls. Treatment response was correlated with elevated Absolute Neutrophil Count (ANC), Absolute Reticulocyte Count (ARC), and reduced CD57+ CD8+ naive cells and B cell % before therapy. However, predictors like TPO, telomere length, and PNH did not emerge as indicators of treatment response. Identifying predictors for treatment response in AA is challenging due to abnormal haematopoiesis, genetic mutations, and treatment variables.

Single-cell transcriptome analysis reveals immunosuppressive landscape in overweight and obese colorectal cancer.

BACKGROUND: Overweight and obesity are established risk factors for various types of cancers including colorectal cancer (CRC). However the underlying molecular mechanisms remain unclear. An in-depth understanding of the oncologic characteristics of overweight and obese CRC at the single-cell level can provide valuable insights for the development of more effective treatment strategies for CRC. METHODS: We conducted single-cell RNA sequencing (scRNA-seq) analysis on tumor and adjacent normal colorectal samples from 15 overweight/obese and 15 normal-weight CRC patients. Immunological and metabolic differences between overweight/obese CRC and non-obese CRC were characterized. RESULTS: We obtained single-cell transcriptomics data from a total of 192,785 cells across all samples. By evaluating marker gene expression patterns, we annotated nine main cell types in the CRC ecosystem. Specifically, we found that the cytotoxic function of effector T cells and NK cells was impaired in overweight/obese CRC compared with non-obese CRC, relating to its metabolic dysregulation. CD4+T cells in overweight/obese CRC exhibited higher expression of immune checkpoint molecules. The antigen-presenting ability of DCs and B cells is down-regulated in overweight/obese CRC, which may further aggravate the immunosuppression of overweight/obese CRC. Additionally, dysfunctional stromal cells were identified, potentially promoting invasion and metastasis in overweight/obese CRC. Furthermore, we discovered the up-regulated metabolism of glycolysis and lipids of tumor cells in overweight/obese CRC, which may impact the metabolism and function of immune cells. We also identified inhibitory interactions between tumor cells and T cells in overweight/obese CRC. CONCLUSIONS: The study demonstrated that overweight/obese CRC has a more immunosuppressive microenvironment and distinct metabolic reprogramming characterized by increased of glycolysis and lipid metabolism. These findings may have implications for the development of novel therapeutic strategies for overweight/obese CRC patients.

Potential crosstalk between SPP1 + TAMs and CD8 + exhausted T cells promotes an immunosuppressive environment in gastric metastatic cancer.

BACKGROUND: Immunotherapy brings new hope to patients with advanced gastric cancer. However, liver metastases can reduce the efficacy of immunotherapy in patients. Tumor-associated macrophages (TAMs) may be the cause of this reduction in efficacy. SPP1 + TAMs are considered to have immunosuppressive properties. We aimed to investigate the involvement of SPP1 + TAMs in the metastasis of gastric cancer. METHODS: The single-cell transcriptome was combined with batched BULK datasets for analysis. Animal models were used to verify the analysis results. RESULTS: We reveal the interaction of SPP1 + TAMs with CD8 + exhausted T cells in metastatic cancer. Among these interactions, GDF15-TGFBR2 may play a key immunosuppressive role. We constructed an LR score to quantify interactions based on ligands and receptors. The LR score is highly correlated with various immune features and clinical molecular subtypes. The LR score may also guide the prediction of the efficacy of immunotherapy and prognosis. CONCLUSIONS: The crosstalk between SPP1 + TAMs and CD8 + exhausted T cells plays a key immunosuppressive role in the gastric metastatic cancer microenvironment.

γδ T cells and the PD-1/PD-L1 axis: a love-hate relationship in the tumor microenvironment.

Gamma delta (γδ) T cells demonstrate strong cytotoxicity against diverse cancer cell types in an MHC-independent manner, rendering them promising contenders for cancer therapy. Although amplification and adoptive transfer of γδ T cells are being evaluated in the clinic, their therapeutic efficacy remains unsatisfactory, primarily due to the influence of the immunosuppressive tumor microenvironment (TME). Currently, the utilization of targeted therapeutic antibodies against inhibitory immune checkpoint (ICP) molecules is a viable approach to counteract the immunosuppressive consequences of the TME. Notably, PD-1/PD-L1 checkpoint inhibitors are considered primary treatment options for diverse malignancies, with the objective of preserving the response of αß T cells. However, γδ T cells also infiltrate various human cancers and are important participants in cancer immunity, thereby influencing patient prognosis. Hence, it is imperative to comprehend the reciprocal impact of the PD-1/PD-L1 axis on γδ T cells. This understanding can serve as a therapeutic foundation for improving γδ T cells adoptive transfer therapy and may offer a novel avenue for future combined immunotherapeutic approaches.