SAP-Dependent and -Independent Regulation of Innate T Cell Development Involving SLAMF Receptors

Endometrial regeneration cell-derived exosomes loaded with siSLAMF6 inhibit cardiac allograft rejection through the suppression of desialylation modification

BACKGROUNDS

Acute transplant rejection is a major component of poor prognoses for organ transplantation. Owing to the multiple complex mechanisms involved, new treatments are still under exploration. Endometrial regenerative cells (ERCs) have been widely used in various refractory immune-related diseases, but the role of ERC-derived exosomes (ERC-Exos) in alleviating transplant rejection has not been extensively studied. Signaling lymphocyte activation molecule family 6 (SLAMF6) plays an important role in regulating immune responses. In this study, we explored the main mechanism by which ERC-Exos loaded with siSLAMF6 can alleviate allogeneic transplant rejection.

METHODS

C57BL/6 mouse recipients of BALB/c mouse kidney transplants were randomly divided into four groups and treated with exosomes. The graft pathology was evaluated by H&E staining. Splenic and transplanted heart immune cell populations were analyzed by flow cytometry. Recipient serum cytokine profiles were determined by enzyme-linked immunosorbent assay (ELISA). The proliferation and differentiation capacity of CD4+ T cell populations were evaluated in vitro. The α-2,6-sialylation levels in the CD4+ T cells were determined by SNA blotting.

RESULTS

In vivo, mice treated with ERC-siSLAMF6 Exo achieved significantly prolonged allograft survival. The serum cytokine profiles of the recipients were significantly altered in the ERC-siSLAMF6 Exo-treated recipients. In vitro, we found that ERC-siSLAMF6-Exo considerably downregulated α-2,6-sialyltransferase (ST6GAL1) expression in CD4+ T cells, and significantly reduced α-2,6-sialylation levels. Through desialylation, ERC-siSLAMF6 Exo therapy significantly decreased CD4+ T cell proliferation and inhibited CD4+ T cell differentiation into Th1 and Th17 cells while promoting regulatory T cell (Treg) differentiation.

CONCLUSIONS

Our study indicated that ERC-Exos loaded with siSLAMF6 reduce the amount of sialic acid connected to α-2,6 at the end of the N-glycan chain on the CD4+ T cell surface, increase the number of therapeutic exosomes endocytosed into CD4+ T cells, and inhibit the activation of T cell receptor signaling pathways, which prolongs allograft survival. This study confirms the feasibility of using ERC-Exos as natural carriers combined with gene therapy, which could be used as a potential therapeutic strategy to alleviate allograft rejection.

Circulating proteomic biomarkers for diagnosing sporadic amyotrophic lateral sclerosis: a cross-sectional study

JOURNAL/nrgr/04.03/01300535-202408000-00039/figure1/v/2023-12-16T180322Z/r/image-tiff Biomarkers are required for the early detection, prognosis prediction, and monitoring of amyotrophic lateral sclerosis, a progressive disease. Proteomics is an unbiased and quantitative method that can be used to detect neurochemical signatures to aid in the identification of candidate biomarkers. In this study, we used a label-free quantitative proteomics approach to screen for substantially differentially regulated proteins in ten patients with sporadic amyotrophic lateral sclerosis compared with five healthy controls. Substantial upregulation of serum proteins related to multiple functional clusters was observed in patients with sporadic amyotrophic lateral sclerosis. Potential biomarkers were selected based on functionality and expression specificity. To validate the proteomics profiles, blood samples from an additional cohort comprising 100 patients with sporadic amyotrophic lateral sclerosis and 100 healthy controls were subjected to enzyme-linked immunosorbent assay. Eight substantially upregulated serum proteins in patients with sporadic amyotrophic lateral sclerosis were selected, of which the cathelicidin-related antimicrobial peptide demonstrated the best discriminative ability between patients with sporadic amyotrophic lateral sclerosis and healthy controls (area under the curve [AUC] = 0.713, P < 0.0001). To further enhance diagnostic accuracy, a multi-protein combined discriminant algorithm was developed incorporating five proteins (hemoglobin beta, cathelicidin-related antimicrobial peptide, talin-1, zyxin, and translationally-controlled tumor protein). The algorithm achieved an AUC of 0.811 and a P-value of < 0.0001, resulting in 79% sensitivity and 71% specificity for the diagnosis of sporadic amyotrophic lateral sclerosis. Subsequently, the ability of candidate biomarkers to discriminate between early-stage amyotrophic lateral sclerosis patients and controls, as well as patients with different disease severities, was examined. A two-protein panel comprising talin-1 and translationally-controlled tumor protein effectively distinguished early-stage amyotrophic lateral sclerosis patients from controls (AUC = 0.766, P < 0.0001). Moreover, the expression of three proteins (FK506 binding protein 1A, cathelicidin-related antimicrobial peptide, and hemoglobin beta-1) was found to increase with disease progression. The proteomic signatures developed in this study may help facilitate early diagnosis and monitor the progression of sporadic amyotrophic lateral sclerosis when used in combination with current clinical-based parameters.

A review: Mechanisms and molecular pathways of signaling lymphocytic activation molecule family 3 (SLAMF3) in immune modulation and therapeutic prospects

The signaling lymphocytic activation molecule (SLAM) family participates in the modulation of various innate and adaptive immune responses. SLAM family (SLAMF) receptors include nine transmembrane glycoproteins, of which SLAMF3 (also known as CD229 or Ly9) has important roles in the modulation of immune responses, from the fundamental activation and suppression of immune cells to the regulation of intricate immune networks. SLAMF3 is mainly expressed in immune cells, such as T, B, and natural killer cells. It has a unique molecular structure, including four immunoglobulin-like domains in the extracellular domain and two immunoreceptor tyrosine-based signaling motifs in the intracellular structural domains. These unique structures have important implications for protein functioning. SLAMF3 is involved in pathogenesis of various disease, particularly autoimmune diseases and cancer. However, despite its potential clinical significance, a comprehensive overview of the current paradigm of SLAMF3 research is lacking. This review summarizes the structure, functional mechanisms, and therapeutic implications of SLAMF3. Our findings highlight the significance of SLAMF3 in both physiological and pathological contexts, and underline its dual role in autoimmunity and malignancies, and including disease progression and prognosis. The review also proposes that future studies on SLAMF3 should explore its context-specific inhibitory and stimulatory effects, expand on its potential in disease mapping, investigate related signaling pathways, and explore its value as a drug target. Research in these areas related to SLAMF3 can provide more precise directions for future therapeutic strategies.

SLAMF8 can predict prognosis of pan-cancer and the immunotherapy response effectivity of gastric cancer

SLAMF8, the eighth member of the Signaling Lymphocytic Activation Molecule Family (SLAMF), functions in the regulation of the development and activity of diverse immune cells as a costimulatory receptor within the SLAMF family. Studies had revealed that SLAMF8 is expressed higher in several autoimmune inflammation diseases and tumors. Nevertheless, the connection between SLAMF8 and pan-cancer remains undisclosed. The research investigated the correlation between SLAMF8 and various factors including the immune microenvironment, microsatellite instability, immune novel antigen, gene mutation, immune regulatory factors, immune blockade TMB, and immune or molecular subtypes of SLAMF8 in verse cancer types. Immunohistochemistry was ultimately employed to validate the presence of the SLAMF8 gene in various tumor types including hepatocellular carcinoma, prostate adenocarcinoma, and kidney renal clear cell carcinoma. Furthermore, the relationship between SLAMF8 expression and the therapeutic efficacy of the PD1 blockade agent, Sintilimab, treatment in gastric cancer was validated. The result of differential analysis suggested that SLAMF8 was over-expressed in pan-cancer compared with paracancerous tissues. The analysis of survival indicated a connection between SLAMF8 and the overall prognosis in different types of cancers, where higher levels of SLAMF8 were found to be significantly linked to unfavorable outcomes in patients but favorable outcome of immunotherapy in gastric cancer. Significant correlations were observed between SLAMF8 levels and pan-cancer tumorigenesis, tumor metabolism, and immunity. As a result, SLAMF8 may become an important prognostic biomarker in the majority of tumors and a hopeful gene target for immunotherapy against gastric cancer.

SLAM-family receptors come of age as a potential molecular target in cancer immunotherapy

The signaling lymphocytic activation molecule (SLAM) family receptors were discovered in immune cells for the first time. The SLAM-family receptors are a significant player in cytotoxicity, humoral immune responses, autoimmune diseases, lymphocyte development, cell survival, and cell adhesion. There is growing evidence that SLAM-family receptors have been involved in cancer progression and heralded as a novel immune checkpoint on T cells. Previous studies have reported the role of SLAMs in tumor immunity in various cancers, including chronic lymphocytic leukemia, lymphoma, multiple myeloma, acute myeloid leukemia, hepatocellular carcinoma, head and neck squamous cell carcinoma, pancreas, lung, and melanoma. Evidence has deciphered that the SLAM-family receptors may be targeted for cancer immunotherapy. However, our understanding in this regard is not complete. This review will discuss the role of SLAM-family receptors in cancer immunotherapy. It will also provide an update on recent advances in SLAM-based targeted immunotherapies.

Novel Inflammasome-Based Risk Score for Predicting Survival and Efficacy to Immunotherapy in Early-Stage Non-Small Cell Lung Cancer

Immune checkpoint inhibitors (ICI) for early-stage non-small cell lung cancer (NSCLC) have been approved to improve outcomes and reduce recurrence. Biomarkers for patient selection are needed. In this paper, we proposed an inflammasome-based risk score (IRS) system for prognosis and prediction of ICI response for early-stage NSCLC. Cox regression analysis was used to identify significant genes (from 141 core inflammasome genes) for overall survival (OS) in a microarray discovery cohort (n = 467). IRS was established and independently validated by other datasets (n = 1320). We evaluated the inflammasome signaling steps based on five gene sets, which were IL1B-, CASP-1-, IL18-, GSDMD-, and inflammasome-regulated genes. Gene set enrichment analysis, the Kaplan–Meier curve, receiver operator characteristic with area under curve (AUC) analysis, and advanced bioinformatic tools were used to confirm the ability of IRS in prognosis and classification of patients into ICI responders and non-responders. A 30-gene IRS was developed, and it indicated good risk stratification at 10-year OS (AUC = 0.726). Patients were stratified into high- and low-risk groups based on optimal cutoff points, and high-risk IRS had significantly poorer OS and relapse-free survival. In addition, the high-risk group was characterized by an inflamed immunophenotype and higher proportion of ICI responders. Furthermore, expression of SLAMF8 was the key gene in IRS and indicated good correlation with biomarkers associated with immunotherapy. It could serve as a therapeutic target in the clinical setting of immunotherapy.

Identification and Validation of Novel Biomarkers for Hepatocellular Carcinoma, Liver Fibrosis/Cirrhosis and Chronic Hepatitis B via Transcriptome Sequencing Technology

Purpose

The aim of this study was to identify and validate novel biomarkers for distinguishing among hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC), liver fibrosis/liver cirrhosis (LF/LC) and chronic hepatitis B (CHB).

Patients and Methods

Transcriptomic sequencing was conducted on the liver tissues of 5 patients with HCC, 5 patients with LF/LC, 5 patients with CHB, and 4 healthy controls. The expression levels of selected mRNAs and proteins were assessed by quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemical (IHC) staining, and were verified in validation set (n=200) and testing set (n=400) via enzyme-linked immunosorbent assay (ELISA).

Results

A total of 9 hub mRNAs were identified by short time-series expression miner and weighted gene co-expression network analysis. Of note, the results of qRT-PCR and IHC staining demonstrated that SHC adaptor protein 1 (SHC1), SLAM family member 8 (SLAMF8), and interleukin-32 (IL-32) exhibited gradually increasing trends in the four groups. Subsequent ELISA tests on the validation cohort indicated that the plasma levels of SHC1, SLAMF8 and IL-32 also gradually increased. Furthermore, a diagnostic model APFSSI (age, PLT, ferritin, SHC1, SLAMF8 and IL-32) was established to distinguish among CHB, LF/LC and HCC. The performance of APFSSI model for discriminating CHB from healthy subjects (AUC=0.966) was much greater compared to SHC1 (AUC=0.900), SLAMF8 (AUC=0.744) and IL-32 (AUC=0.821). When distinguishing LF/LC from CHB, APFSSI was the most outstanding diagnostic parameter (AUC=0.924), which was superior to SHC1, SLAMF8 and IL-32 (AUC=0.812, 0.684 and 0.741, respectively). Likewise, APFSSI model with the greatest AUC value displayed an excellent performance for differentiating between HCC and LF/LC than other variables (SHC1, SLAMF8 and IL-32) via ROC analysis. Finally, the results in the test set were consistent with those in the validation set.

Conclusion

SHC1, SLAMF8 and IL-32 can differentiate among patients with HCC, LF/LC, CHB and healthy controls. More importantly, the APFSSI model greatly improves the diagnostic accuracy of HBV-associated liver diseases.

Innate immune response in bovine neutrophils stimulated with Mycoplasma bovis

Mycoplasma bovis (M. bovis) is a significant worldwide pathogen of cattle. Neutrophils have an important role in the innate immune response during infection with M. bovis. However, even though neutrophils accumulate in M. bovis infection, the interaction of M. bovis and neutrophils has not been fully elucidated. We attempted to elucidate the innate immune response of neutrophils stimulated with M. bovis and evaluate the transcriptome and functional analysis of bovine neutrophils stimulated with M. bovis. Proinflammatory cytokines, such as inducible nitric oxide (iNOS), which was the most increased gene in transcriptome analysis, were increased in quantitative polymerase chain reaction analysis of bovine neutrophils stimulated with live or heat-killed M. bovis. Nitric oxide and intracellular reactive oxygen species production of neutrophils stimulated with M. bovis was significantly increased. Neutrophils stimulated with M. bovis showed an increased ratio of nonapoptotic cell death compared to unstimulated controls. We demonstrated that neutrophil extracellular traps (NETs) formation was not recognized in neutrophils stimulated with live M. bovis. However, heat-killed M. bovis induced NETs formation. We also showed the interaction with M. bovis and bovine neutrophils regarding proinflammatory cytokine gene expression and functional expression related to NETs formation. Live and killed M. bovis induced innate immune responses in neutrophils and had the potential to induce NETs formation, but live M. bovis escaped NETs.

Transcriptome analysis of Mycoplasma bovis stimulated bovine peripheral blood mononuclear cells

Mycoplasma bovis is a pathogenic bacterium in bovines that causes huge global economic losses. Numerous factors play important roles in M. bovis pathogenesis; however, the host immune response involved in M. bovis infection has not been fully elucidated. We aimed to determine the characteristics of the host immune response to Mycoplasma infection. We evaluated the responsiveness of bovine peripheral blood mononuclear cells (PBMCs) stimulated with M. bovis via microarray analysis. The transcriptional abundance of innate immune-related genes IL-36A, IL-27, IFN-γ, and IL-17 in PBMCs increased after M. bovis exposure. Upon M. bovis infection, there was increased expression of the lymphocyte activated genes basic leucine zipper transcription factor (BATF) and signaling lymphocytic activation molecule family members 1 and 7 (SLAMF 1 and SLAMF 7) in PBMCs compared with that in unstimulated cells. The study revealed that the transcriptional abundance of innate immunity genes in PBMCs increased during M. bovis infection. This induced the activation of PBMCs, giving rise to an immune response, which is followed by the development of the inflammatory response. The results from this study could be used as the basis for the development of novel vaccine candidates against M. bovis.

SLAM-SAP-Fyn: Old Players with New Roles in iNKT Cell Development and Function

Invariant natural killer T (iNKT) cells are a unique T cell lineage that develop in the thymus and emerge with a memory-like phenotype. Accordingly, following antigenic stimulation, they can rapidly produce copious amounts of Th1 and Th2 cytokines and mediate activation of several immune cells. Thus, it is not surprising that iNKT cells play diverse roles in a broad range of diseases. Given their pivotal roles in host immunity, it is crucial that we understand the mechanisms that govern iNKT cell development and effector functions. Over the last two decades, several studies have contributed to the current knowledge of iNKT cell biology and activity. Collectively, these studies reveal that the thymic development of iNKT cells, their lineage expansion, and functional properties are tightly regulated by a complex network of transcription factors and signaling molecules. While prior studies have clearly established the importance of the SLAM-SAP-Fyn signaling axis in iNKT cell ontogenesis, recent studies provide exciting mechanistic insights into the role of this signaling cascade in iNKT cell development, lineage fate decisions, and functions. Here we summarize the previous literature and discuss the more recent studies that guide our understanding of iNKT cell development and functional responses.

SLAMF6 as a Regulator of Exhausted CD8+ T Cells in Cancer

The tumor microenvironment in leukemia and solid tumors induces a shift of activated CD8+ cytotoxic T cells to an exhausted state, characterized by loss of proliferative capacity and impaired immunologic synapse formation. Efficient strategies and targets need to be identified to overcome T-cell exhaustion and further improve overall responses in the clinic. Here, we took advantage of the Eμ-TCL1 chronic lymphocytic leukemia (CLL) and B16 melanoma mouse models to assess the role of the homophilic cell-surface receptor SLAMF6 as an immune-checkpoint regulator. The transfer of SLAMF6+ Eμ-TCL1 cells into SLAMF6-/- recipients, in contrast to wild-type (WT) recipients, significantly induced expansion of a PD-1+ subpopulation among CD3+CD44+CD8+ T cells, which had impaired cytotoxic functions. Conversely, administering anti-SLAMF6 significantly reduced the leukemic burden in Eμ-TCL1 recipient WT mice concomitantly with a loss of PD-1+CD3+CD44+CD8+ T cells with significantly increased effector functions. Anti-SLAMF6 significantly reduced leukemic burden in the peritoneal cavity, a niche where antibody-dependent cellular cytotoxicity (ADCC) is impaired, possibly through activation of CD8+ T cells. Targeting of SLAMF6 affected tumor growth not only in B cell-related leukemia and lymphomas but also in nonhematopoietic tumors such as B16 melanoma, where SLAMF6 is not expressed. In vitro exhausted CD8+ T cells showed increased degranulation when anti-human SLAMF6 was added in culture. Taken together, anti-SLAMF6 both effectively corrected CD8+ T-cell dysfunction and had a direct effect on tumor progression. The outcomes of our studies suggest that targeting SLAMF6 is a potential therapeutic strategy.

The Role of Adaptor Proteins in the Biology of Natural Killer T (NKT) Cells

Adaptor proteins contribute to the selection, differentiation and activation of natural killer T (NKT) cells, an innate(-like) lymphocyte population endowed with powerful immunomodulatory properties. Distinct from conventional T lymphocytes NKT cells preferentially home to the liver, undergo a thymic maturation and differentiation process and recognize glycolipid antigens presented by the MHC class I-like molecule CD1d on antigen presenting cells. NKT cells express a semi-invariant T cell receptor (TCR), which combines the Vα14-Jα18 chain with a Vβ2, Vβ7, or Vβ8 chain in mice and the Vα24 chain with the Vβ11 chain in humans. The avidity of interactions between their TCR, the presented glycolipid antigen and CD1d govern the selection and differentiation of NKT cells. Compared to TCR ligation on conventional T cells engagement of the NKT cell TCR delivers substantially stronger signals, which trigger the unique NKT cell developmental program. Furthermore, NKT cells express a panoply of primarily inhibitory NK cell receptors (NKRs) that control their self-reactivity and avoid autoimmune activation. Adaptor proteins influence NKT cell biology through the integration of TCR, NKR and/or SLAM (signaling lymphocyte-activation molecule) receptor signals or the variation of CD1d-restricted antigen presentation. TCR and NKR ligation engage the SH2 domain-containing leukocyte protein of 76kDa slp-76 whereas the SLAM associated protein SAP serves as adaptor for the SLAM receptor family. Indeed, the selection and differentiation of NKT cells selectively requires co-stimulation via SLAM receptors. Furthermore, SAP deficiency causes X-linked lymphoproliferative disease with multiple immune defects including a lack of circulating NKT cells. While a deletion of slp-76 leads to a complete loss of all peripheral T cell populations, mutations in the SH2 domain of slp-76 selectively affect NKT cell biology. Furthermore, adaptor proteins influence the expression and trafficking of CD1d in antigen presenting cells and subsequently selection and activation of NKT cells. Adaptor protein complex 3 (AP-3), for example, is required for the efficient presentation of glycolipid antigens which require internalization and processing. Thus, our review will focus on the complex contribution of adaptor proteins to the delivery of TCR, NKR and SLAM receptor signals in the unique biology of NKT cells and CD1d-restricted antigen presentation.

Serum biomarker panels for the diagnosis of gastric cancer

Gastric cancer is a leading cause of mortality due to neoplastic disease. Although early detection of gastric cancers can decrease the mortality rate, it remains a diagnostic challenge because of the lack of effective biomarkers. In this study, fifteen gastric cancer patients and ten healthy subjects were recruited to assess novel serum biomarkers for gastric cancer using antibody microarray technology. ELISA was utilized to validate the antibody array results. As a result, compared to the controls, eleven cytokines were found to be significantly increased in gastric cancer, including interferon gamma receptor 1 (IFNGR1), neurogenic locus notch homolog protein 3 (Notch‐3), tumor necrosis factor receptor superfamily member 19L (TNFRSF19L), growth hormone receptor (GHR), signaling lymphocytic activation molecule family 8 (SLAMF8), folate receptor beta (FR‐beta), integrin alpha 5, galectin‐8, erythropoietin‐producing hepatocellular A1 (EphA1), epiregulin, and fibroblast growth factor 12 (FGF‐12) with P < 0.05. ELISA validation supported the results of the antibody array. More importantly, most of these eleven cytokines, including IFNGR1, TNFRSF19L, GHR, SLAMF8, FR‐beta, and integrin alpha 5 were discovered to be elevated in gastric cancer serum samples for the first time in this study, suggesting that these proteins may serve as novel biomarkers for the early diagnosis and prognosis determination of gastric cancer.

Combined deficiency of SLAMF8 and SLAMF9 prevents endotoxin-induced liver inflammation by downregulating TLR4 expression on macrophages

Classical signaling lymphocyte activating molecule (SLAM) family receptors are abundant within many types of immune cells, whereas the nonclassical SLAM family receptors SLAMF8 and SLAMF9, which uniquely lack cytoplasmic signaling motifs, are highly expressed by myeloid cells. Due to the potential redundancy, whether these two receptors regulate macrophage function remains largely unknown. Here, we show that SLAMF8 and SLAMF9 co-regulate macrophage-mediated liver inflammation. To overcome the redundancy, we generated mice that simultaneously lacked SLAMF8 and SLAMF9 using CRISPR-Cas9 technology. Although macrophage differentiation was not altered by the combined deficiency of SLAMF8 and SLAMF9, the loss of these two receptors significantly protected against lipopolysaccharide (LPS)-induced liver injury. SLAMF8 and SLAMF9 double-deficient mice had a prolonged survival rate and less infiltration of inflammatory cells. The depletion of macrophages using clodronate liposomes abolished the effects of SLAMF8 and SLAMF9 deficiencies on LPS-induced liver injury, which demonstrates that these receptors are required for macrophage activation following LPS challenge. Moreover, the deficiency of SLAMF8 and SLAMF9 suppressed the secretion of inflammatory cytokines by downregulating the expression of Toll-like receptor-4 (TLR4), a receptor that specifically binds LPS, which led to decreased mitogen-activated protein kinases (MAPK) signaling activation. Notably, combined injections of truncated extracellular SLAMF8 and SLAMF9 proteins significantly alleviated LPS-induced liver injury. Thus, our findings provide insights into the role of SLAMF8 and SLAMF9 in endotoxin-induced liver injury and suggest that SLAMF8 and SLAMF9 are potential therapeutic targets for acute hepatic injury.

The ins and outs of type I iNKT cell development

Natural killer T (NKT) cells are innate-like lymphocytes that bridge the gap between the innate and adaptive immune responses. Like innate immune cells, they have a mature, effector phenotype that allows them to rapidly respond to threats, compared to adaptive cells. NKT cells express T cell receptors (TCRs) like conventional T cells, but instead of responding to peptide antigen presented by MHC class I or II, NKT cell TCRs recognize glycolipid antigen in the context of CD1d. NKT cells are subdivided into classes based on their TCR and antigen reactivity. This review will focus on type I iNKT cells that express a semi invariant Vα14Jα18 TCR and respond to the canonical glycolipid antigen, α-galactosylceramide. The innate-like effector functions of these cells combined with their T cell identity make their developmental path quite unique. In addition to the extrinsic factors that affect iNKT cell development such as lipid:CD1d complexes, co-stimulation, and cytokines, this review will provide a comprehensive delineation of the cell intrinsic factors that impact iNKT cell development, differentiation, and effector functions - including TCR rearrangement, survival and metabolism signaling, transcription factor expression, and gene regulation.

The novel immunoglobulin super family receptor SLAMF9 identified in TAM of murine and human melanoma influences pro-inflammatory cytokine secretion and migration

Melanoma is a highly immunogenic tumor with a good response to treatment with immune checkpoint inhibitors. Tumor-associated macrophages (TAMs) play an important immunosuppressive role in such tumors and have therefore been identified as possible future therapeutic targets in oncology. The aim of this study was to identify novel immunoregulatory receptors specifically expressed on TAM. Expression of Slamf9, a member of the signaling lymphocytic-activating molecule (Slam) immunoreceptor family, was found to be upregulated in a gene expression analysis of murine bone marrow-derived macrophages (BMDM) stimulated with tumor-conditioned medium of B16F1 melanoma cells. SLAMF9⁺ macrophages were identified in human and murine melanomas by using self-generated antibodies against human and murine SLAMF9. A comprehensive immunohistochemical analysis of tissue microarrays detected SLAMF9⁺ TAM in 73.3% of human melanomas, but also in 95.5% of naevi of melanoma patients and in 50% of naevi from healthy controls. In addition, 20% of melanomas and 2.3% of naevi from melanoma patients displayed a positive SLAMF9 expression also in melanocytic cells. No SLAMF9 expression was detected in naevus cells of healthy donors. Although SLAMF9 has no intracellular signaling motif, a comprehensive functional analysis revealed that the molecule was able to significantly enhance TNF-α secretion after LPS-stimulation. In addition, SLAMF9 delayed the wound closure of RAW 264.7 cells in a scratch assay, while proliferation and cell death were not affected. Taken together, SLAMF9 is a novel type-I-transmembrane receptor with immunomodulatory properties in macrophages. Further studies are required to evaluate whether SLAMF9 classifies as a promising future therapeutic target in melanoma.

Costimulatory checkpoint SLAMF8 is an independent prognosis factor in glioma

AIMS

Immune checkpoint blockade has made breakthroughs in immunotherapy for glioma. However, current immunotherapy has therapeutic benefits only in a subset of patients and accompanied by immune-related side effects. SLAMF8 is a costimulatory molecule that affects the activation of macrophages in inflammation. The study of SLAMF8 may provide new information for immunological research and treatment of glioma.

METHODS

CGGA and TCGA cohorts of 946 patients with RNA sequencing data and full clinical information were analyzed using R language and GraphPad Prism 7.

RESULTS

SLAMF8 was overexpressed along with malignancy progression and was a biomarker of mesenchymal subtype. As an independent prognostic factor, high SLAMF8 conferred reduced overall survival and chemotherapy resistance. SLAMF8 implied lower proportion of cancer cells along with increasing enrichment of monocytic lineage, myeloid dendritic cells. Functional analysis showed higher SLAMF8 indicated activation of antigen processing and presenting and the IFN-γ/TNF/TLR-mediated signaling. Meanwhile, coexpressing with classical checkpoint SLAMF8 aggravated immunosuppression and enhanced inflammation response.

CONCLUSION

Our study highlighted the important role of SLAMF8 in malignancy progression, shortened survival, and immune disorders. Further research on SLAMF8 in immunosuppression and inflammation response to glioma cells could aid immunotherapy for glioma.

Development of mucosal-associated invariant T cells

Mucosal‐associated invariant T (MAIT) cells develop in the thymus and migrate into the periphery to become the largest antigen‐specific αβ T‐cell population in the human immune system. However, the frequency of MAIT cells varies widely between human individuals, and the basis for this is unclear. While MAIT cells are highly conserved through evolution and are phenotypically similar between humans and mice, they represent a much smaller proportion of total T cells in mice. In this review, we discuss how MAIT cells transition through a three‐stage development pathway in both mouse and human thymus, and continue to mature and expand after they leave the thymus. Moreover, we will explore and speculate on how specific factors regulate different stages of this process.

Ly9 (SLAMF3) receptor differentially regulates iNKT cell development and activation in mice

Invariant natural killer T (iNKT) cells develop into three subsets (NKT1, NKT2, and NKT17) expressing a distinct transcription factor profile, which regulates cytokine secretion upon activation. iNKT cell development in the thymus is modulated by signaling lymphocytic activation molecule family (SLAMF) receptors. In contrast to other SLAMF members, Ly9 (SLAMF3) is a non-redundant negative regulator of iNKT cell development. Here, we show that Ly9 influences iNKT cell lineage differentiation. Ly9-deficient mice on a BALB/c background contained a significantly expanded population of thymic NKT2 cells, while NKT1 cells were nearly absent in BALB/c.Ly9^-/- thymus. Conversely, the number of peripheral NKT1 cells in BALB/c.Ly9^-/- mice was comparable to that in wild-type mice, indicating that the homeostasis of the different iNKT cell subsets may have distinct requirements depending on their tissue localization. Importantly, Ly9 absence also promoted NKT2 cell differentiation in the NKT1-skewed C57BL/6 background. Furthermore, treatment of wild-type mice with an agonistic monoclonal antibody directed against Ly9 impaired IL-4 and IFN-γ production and reduced by half the number of spleen iNKT cells, with a significant decrease in the proportion of NKT2 cells. Thus, anti-Ly9 targeting could represent a novel therapeutic approach to modulate iNKT cell numbers and activation.

SLAMF7-CAR T cells eliminate myeloma and confer selective fratricide of SLAMF7+ normal lymphocytes

SLAMF7 is under intense investigation as a target for immunotherapy in multiple myeloma. In this study, we redirected the specificity of T cells to SLAMF7 through expression of a chimeric antigen receptor (CAR) derived from the huLuc63 antibody (elotuzumab) and demonstrate that SLAMF7-CAR T cells prepared from patients and healthy donors confer potent antimyeloma reactivity. We confirmed uniform, high-level expression of SLAMF7 on malignant plasma cells in previously untreated and in relapsed/refractory (R/R) myeloma patients who had received previous treatment with proteasome inhibitors and immunomodulatory drugs. Consequently, SLAMF7-CAR T cells conferred rapid cytolysis of previously untreated and R/R primary myeloma cells in vitro. In addition, a single administration of SLAMF7-CAR T cells led to resolution of medullary and extramedullary myeloma manifestations in a murine xenograft model in vivo. SLAMF7 is expressed on a fraction of normal lymphocytes, including subsets of natural killer (NK) cells, T cells, and B cells. After modification with the SLAMF7-CAR, both CD8⁺ and CD4⁺ T cells rapidly acquired and maintained a SLAMF7^- phenotype and could be readily expanded to therapeutically relevant cell doses. We analyzed the recognition of normal lymphocytes by SLAMF7-CAR T cells and show that they induce selective fratricide of SLAMF7^+/high NK cells, CD4⁺ and CD8⁺ T cells, and B cells. Importantly, however, the fratricide conferred by SLAMF7-CAR T cells spares the SLAMF7^-/low fraction in each cell subset and preserves functional lymphocytes, including virus-specific T cells. In aggregate, our data illustrate the potential use of SLAMF7-CAR T-cell therapy as an effective treatment against multiple myeloma and provide novel insights into the consequences of targeting SLAMF7 for the normal lymphocyte compartment.

Slamf6 negatively regulates autoimmunity

The nine SLAM family (Slamf) receptors are positive or negative regulators of adaptive and innate immune responses, and of several autoimmune diseases. Here we report that the transfer of Slamf6^-/- B6 CD4⁺ T cells into co-isogenic bm12 mice causes SLE-like autoimmunity with elevated levels of autoantibodies. In addition, significantly higher percentages of Tfh cells and IFN-γ-producing CD4⁺ cells, as well as GC B cells were observed. Interestingly, the expression of the Slamf6-H1 isoform in Slamf6^-/- CD4⁺ T cells did not induce this lupus-like phenotype. By contrast, Slamf1^-/- or Slamf5^-/- CD4⁺ T cells caused the same pathology as WT CD4⁺ T cells. As the transfer of Slamf [1+6]^-/- or Slamf [1+5+6]^-/- CD4⁺ T cells induced WT levels of autoantibodies, the presence of Slamf1 was requisite for the induction of increased levels of autoantibodies by Slamf6^-/- CD4⁺ T cells. We conclude that Slamf6 functions as an inhibitory receptor that controls autoimmune responses.

CRISPR-Mediated Triple Knockout of SLAMF1, SLAMF5 and SLAMF6 Supports Positive Signaling Roles in NKT Cell Development

The SLAM family receptors contribute to diverse aspects of lymphocyte biology and signal via the small adaptor molecule SAP. Mutations affecting SAP lead to X-linked lymphoproliferative syndrome Type 1, a severe immunodysregulation characterized by fulminant mononucleosis, dysgammaglobulinemia, and lymphoproliferation/lymphomas. Patients and mice having mutations affecting SAP also lack germinal centers due to a defect in T:B cell interactions and are devoid of invariant NKT (iNKT) cells. However, which and how SLAM family members contribute to these phenotypes remains uncertain. Three SLAM family members: SLAMF1, SLAMF5 and SLAMF6, are highly expressed on T follicular helper cells and germinal center B cells. SLAMF1 and SLAMF6 are also implicated in iNKT development. Although individual receptor knockout mice have limited iNKT and germinal center phenotypes compared to SAP knockout mice, the generation of multi-receptor knockout mice has been challenging, due to the genomic linkage of the genes encoding SLAM family members. Here, we used Cas9/CRISPR-based mutagenesis to generate mutations simultaneously in Slamf1, Slamf5 and Slamf6. Genetic disruption of all three receptors in triple-knockout mice (TKO) did not grossly affect conventional T or B cell development and led to mild defects in germinal center formation post-immunization. However, the TKO worsened defects in iNKT cells development seen in SLAMF6 single gene-targeted mice, supporting data on positive signaling and potential redundancy between these receptors.

CRISPR-Mediated Slamf1Δ/Δ Slamf5Δ/Δ Slamf6Δ/Δ Triple Gene Disruption Reveals NKT Cell Defects but Not T Follicular Helper Cell Defects

SAP (SH2D1A) is required intrinsically in CD4 T cells to generate germinal center responses and long-term humoral immunity. SAP binds to SLAM family receptors, including SLAM, CD84, and Ly108 to enhance cytokine secretion and sustained T cell:B cell adhesion, which both improve T follicular helper (Tfh) cell aid to germinal center (GC) B cells. To understand the overlapping roles of multiple SLAM family receptors in germinal center responses, Slamf1^Δ/ΔSlamf5^Δ/ΔSlamf6^Δ/Δ triple gene disruption (Slamf1,5,6^Δ/Δ) mice were generated using CRISPR-Cas9 gene editing to eliminate expression of SLAM (CD150), CD84, and Ly108, respectively. Gene targeting was highly efficient, with 6 of 6 alleles disrupted in 14 of 23 pups and the majority of alleles disrupted in the remaining pups. NKT cell differentiation in Slamf1,5,6^Δ/Δ mice was defective, but not completely absent. The remaining NKT cells exhibited substantially increased 2B4 (SLAMF4) expression. Surprisingly, there were no overt defects in germinal center responses to acute viral infections or protein immunizations in Slamf1,5,6^Δ/Δ mice, unlike Sh2d1a^-/- mice. Similarly, in the context of a competitive environment, SLAM family receptor expressing GC Tfh cell, GC B cell, and plasma cell responses exhibited no advantages over Slamf1,5,6^Δ/Δ cells.

Clonal expansion of CD4(+) cytotoxic T lymphocytes in patients with IgG4-related disease

BACKGROUND

IgG4-related disease (IgG4-RD) is a systemic condition of unknown cause characterized by highly fibrotic lesions with dense lymphoplasmacytic infiltrates. CD4(+) T cells constitute the major inflammatory cell population in IgG4-RD lesions.

OBJECTIVE

We used an unbiased approach to characterize CD4(+) T-cell subsets in patients with IgG4-RD based on their clonal expansion and ability to infiltrate affected tissue sites.

METHODS

We used flow cytometry to identify CD4(+) effector/memory T cells in a cohort of 101 patients with IgG4-RD. These expanded cells were characterized by means of gene expression analysis and flow cytometry. Next-generation sequencing of the T-cell receptor β chain gene was performed on CD4(+)SLAMF7(+) cytotoxic T lymphocytes (CTLs) and CD4(+)GATA3(+) TH2 cells in a subset of patients to identify their clonality. Tissue infiltration by specific T cells was examined by using quantitative multicolor imaging.

RESULTS

CD4(+) effector/memory T cells with a cytolytic phenotype were expanded in patients with IgG4-RD. Next-generation sequencing revealed prominent clonal expansions of these CD4(+) CTLs but not CD4(+)GATA3(+) memory TH2 cells in patients with IgG4-RD. The dominant T cells infiltrating a range of inflamed IgG4-RD tissue sites were clonally expanded CD4(+) CTLs that expressed SLAMF7, granzyme A, IL-1β, and TGF-β1. Clinical remission induced by rituximab-mediated B-cell depletion was associated with a reduction in numbers of disease-associated CD4(+) CTLs.

CONCLUSIONS

IgG4-RD is prominently linked to clonally expanded IL-1β- and TGF-β1-secreting CD4(+) CTLs in both peripheral blood and inflammatory tissue lesions. These active, terminally differentiated, cytokine-secreting effector CD4(+) T cells are now linked to a human disease characterized by chronic inflammation and fibrosis.

Development of invariant natural killer T cells

Invariant natural killer T (iNKT) cells develop into functionally distinct subsets. Each subset expresses a unique combination of transcription factors that regulate cytokine gene transcription upon activation. The tissue distribution and localization within tissues also varies between subsets. Importantly, the relative abundance of the various subsets is directly responsible for altering several immunological parameters, which subsequently affect the immune response. Here, I review recent advances in our understanding of the molecular regulation of iNKT cell subset development.

Negative Regulation of Humoral Immunity Due to Interplay between the SLAMF1, SLAMF5, and SLAMF6 Receptors

Whereas the SLAMF-associated protein (SAP) is involved in differentiation of T follicular helper (Tfh) cells and antibody responses, the precise requirements of SLAMF receptors in humoral immune responses are incompletely understood. By analyzing mice with targeted disruptions of the Slamf1, Slamf5, and Slamf6 genes, we found that both T-dependent and T-independent antibody responses were twofold higher compared to those in single knockout mice. These data suggest a suppressive synergy of SLAMF1, SLAMF5, and SLAMF6 in humoral immunity, which contrasts the decreased antibody responses resulting from a defective GC reaction in the absence of the adapter SAP. In adoptive co-transfer assays, both [Slamf1 + 5 + 6]^−/− B and T cells were capable of inducing enhanced antibody responses, but more pronounced enhancement was observed after adoptive transfer of [Slamf1 + 5 + 6]^−/− B cells compared to that of [Slamf1 + 5 + 6]^−/− T cells. In support of [Slamf1 + 5 + 6]^−/− B cell intrinsic activity, [Slamf1 + 5 + 6]^−/− mice also mounted significantly higher antibody responses to T-independent type 2 antigen. Furthermore, treatment of mice with anti-SLAMF6 monoclonal antibody results in severe inhibition of the development of Tfh cells and GC B cells, confirming a suppressive effect of SLAMF6. Taken together, these results establish SLAMF1, SLAMF5, and SLAMF6 as important negative regulators of humoral immune response, consistent with the notion that SLAM family receptors have dual functions in immune responses.

Transplantation: molecular phenotyping of T-cell-mediated rejection

A new study has reported a molecular signature of T-cell-mediated rejection in human kidney transplant biopsy samples that is enriched for effector T cells, interferon-γ and macrophages. Inhibitors of T-cell activation, such as CTLA4 and PDL1, were also prominent, raising the possibility that these immunological constrains could be harnessed by therapies for treating rejection.