SLAM receptors foster iNKT cell development by reducing TCR signal strength after positive selection.

Invariant natural killer T cells (iNKT cells) develop through an incompletely understood process that requires positive selection by CD4+CD8+ double-positive thymocytes and SLAM family receptors (SFRs). Here we found that SFRs promoted the development of iNKT cells by reducing the strength of the T cell antigen receptor (TCR) signal after positive selection. This effect improved the survival of iNKT cells and their responses to antigen. Loss of SFRs upregulated the expression of inhibitory receptors, including PD-1, on iNKT cells to mitigate the deleterious effect of SFR deficiency. The role of SFRs could be mimicked by expression of SLAMF6 alone in SFR-deficient mice, and this involved the adaptor SAP-kinase Fyn complex and the phosphatase SHP-1. Thus, SFRs foster iNKT cell development by attenuating TCR signal strength after positive selection.

The Self-Specific Activation Receptor SLAM Family Is Critical for NK Cell Education.

NK cell education, a term describing a process for NK cell acquisition of functional competence, is primarily achieved by self-MHC-I-specific inhibitory receptors. In this study, we have demonstrated that SLAM family receptors (SFRs) redundantly expressed on hematopoietic cells function as self-specific activation receptors critical for NK cell education. To overcome gene redundancy, we generated mice simultaneously lacking seven SFRs, revealing that NK-cell-mediated rejection of semi-allogeneic hematopoietic cells largely depended on the presence of SFRs on target cells. This stimulatory effect was determined by the presence of SFR-coupled adaptors; however, SFR-deficient mice displayed enhanced reactivity to hematopoietic cells. These findings demonstrate that SFRs endow NK cells with an ability to kill hematopoietic cells during the effector phase; however, the sustained engagement of SFRs can desensitize NK cell responses during an education process. Therefore, self-specific activating ligands may be "tolerogens" for NK cells, akin to self-antigens that induce T cell tolerance.

SLAM Family Receptors in B Cell Chronic Lymphoproliferative Disorders.

The signaling lymphocytic activation molecule (SLAM) receptor family (SLAMF) consists of nine glycoproteins that belong to the CD2 superfamily of immunoglobulin (Ig) domain-containing molecules. SLAMF receptors modulate the differentiation and activation of a wide range of immune cells. Individual SLAMF receptors are expressed on the surface of hematopoietic stem cells, hematopoietic progenitor cells, B cells, T cells, NK cells, NKT cells, monocytes, macrophages, dendritic cells, neutrophils, and platelets. The expression of SLAMF receptors was studied during normal B cell maturation. Several SLAMF receptors were also detected in cancer cell lines of B-lymphoid origin and in pathological B cells from patients with B cell chronic lymphoproliferative disorders (B-CLPD), the most frequent hematological malignancies in adults. This review summarizes current knowledge on the expression of SLAMF receptors and their adaptor proteins SAP and EAT-2 in B-CLPD. Several SLAMF receptors could be regarded as potential diagnostic and differential diagnostic markers, prognostic factors, and targets for the development of novel drugs for patients with B-CLPD.

Single-Cell Analysis Reveals the Heterogeneity of Monocyte-Derived and Peripheral Type-2 Conventional Dendritic Cells.

Dendritic cells (DCs) are critical for pathogen recognition and Ag processing/presentation. Human monocyte-derived DCs (moDCs) have been extensively used in experimental studies and DC-based immunotherapy approaches. However, the extent of human moDC and peripheral DCs heterogeneity and their interrelationship remain elusive. In this study, we performed single-cell RNA sequencing of human moDCs and blood DCs. We identified seven subtypes within moDCs: five corresponded to type 2 conventional DCs (cDC2s), and the other two were CLEC10A+CD127+ cells with no resemblance to any peripheral DC subpopulations characterized to date. Moreover, we defined five similar subtypes in human cDC2s, revealed the potential differentiation trajectory among them, and unveiled the transcriptomic differences between moDCs and cDC2s. We further studied the transcriptomic changes of each moDC subtype during maturation, demonstrating SLAMF7 and IL15RA as maturation markers and CLEC10A and SIGLEC10 as markers for immature DCs. These findings will enable more accurate functional/developmental analyses of human cDC2s and moDCs.

SLAMF7 Signaling Reprograms T Cells toward Exhaustion in the Tumor Microenvironment.

T cell exhaustion represents one of the most pervasive strategies tumors employ to circumvent the immune system. Although repetitive, cognate TCR signaling is recognized as the primary driving force behind this phenomenon, and it remains unknown what other forces drive T cell exhaustion in the tumor microenvironment (TME). In this study, we show that activation of the self-ligand SLAMF7 immune receptor on T cells induced STAT1 and STAT3 phosphorylation, expression of multiple inhibitory receptors, and transcription factors associated with T cell exhaustion. Analysis of The Cancer Genome Atlas revealed that SLAMF7 transcript levels were strongly correlated with various inhibitory receptors and that high SLAMF7 expression was indicative of poor survival in clear cell renal cell carcinoma (ccRCC). Targeted reanalysis of a CyTOF dataset, which profiled the TME in 73 ccRCC patients, revealed cell-type-specific SLAMF7 expression patterns, strong correlations between exhausted T cells and SLAMF7+ tumor-associated macrophages (TAMs), and a unique subset of SLAMF7highCD38high TAMs. These SLAMF7highCD38high TAMs showed the strongest correlations with exhausted T cells and were an independent prognostic factor in ccRCC. Confirmatory ex vivo coculture studies validated that SLAMF7-SLAMF7 interactions between murine TAMs and CD8+ T cells induce expression of multiple inhibitory receptors. Finally, mice lacking SLAMF7 show restricted growth of B16-F10 tumors, and CD8+ T cells from these mice express less PD-1 and TOX and exhibited an impaired ability to progress through the exhaustion developmental trajectory to terminal exhaustion. These findings suggest that SLAMF7 might play an important role in modulating T cell function in the TME.

Screening of Diabetic Nephropathy Progression-Related Genes Based on Weighted Gene Co-expression Network Analysis.

The purpose of this study is to explore the progression-related genes of diabetic nephropathy (DN) through weighted gene co-expression network analysis (WGCNA). The gene expression dataset GSE14202 was downloaded from the GEO database for differential expression analysis. WGCNA v1.69 was used to perform co-expression analysis on differentially expressed genes. 25 modular genes were selected through WGCNA. The motif enrichment analysis was performed on 25 genes, and 34 motifs were obtained, of which 8 transcription factors (TFs) were differentially expressed. GENIE3 was applied to analyze the expression correlation of 8 differentially expressed TFs and 25 genes. Combined with the predicted TF-target gene relationship, 69 interactions between 8 TFs and 18 genes were obtained. The functional enrichment analysis of 18 genes showed that 7 key genes were obviously enriched in adaptive immune response and were clearly up-regulated in advanced DN patients. The expression of C1S, LAIR1, CD84, SIT1, SASH3, and CD180 in glomerular samples from DN patients was significantly up-regulated in compared with normal samples, and the expression of these genes was negatively correlated with GFR. We observed that in the in vitro cell model of DN, the relative expression levels of 5 key genes (except SASH3) were obviously elevated in the high-glucose group. Five key genes were identified to be related to the progression of DN. The findings of this study may provide new ideas and therapeutic targets for exploring the pathogenesis of DN.

Macrophage-mediated anti-tumor immunity against high-risk neuroblastoma.

Neuroblastoma is the most common extracranial childhood solid tumor. The majority of high-risk neuroblastoma is resistant/refractory to the current high intensity therapy. Neuroblastoma lacks classical HLA Class I expression and exhibits low mutation burden, allowing neuroblastoma cells to evade CD8+ T cell-mediated immunity. Neuroblastoma cells do not express PD-L1, and tumor-associated macrophages are the predominant PD-L1+ cells in the tumor. In this study, we performed gene expression profiling and survival analyses on large neuroblastoma datasets to address the prognostic effect of PD-L1 gene expression and the possible involvement of the SLAMF7 pathway in the anti-neuroblastoma immunity. High-level expression of PD-L1 was found significantly associated with better outcome of high-risk neuroblastoma patients; two populations of PD-1+ PD-L1+ macrophages could be present in high-risk tumors with PD-1/PD-L1 ratios, ≈1 and >1. Patients with the PD-1/PD-L1 ratio >1 tumor showed inferior survival. High-level co-expression of SLAMF7 and SH2D1B was significantly associated with better survival of the high-risk neuroblastoma patients. Together, this study supports the hypothesis that macrophages are important effector cells in the anti-high-risk neuroblastoma immunity, that PD-1 blockade therapy can be beneficial to the high-risk neuroblastoma subset with the PD-1/PD-L1 expression ratio >1, and that SLAMF7 is a new therapeutic target of high-risk neuroblastoma.

Upregulation of CXCL1 and LY9 contributes to BRCAness in ovarian cancer and mediates response to PARPi and immune checkpoint blockade.

BACKGROUND: Mutations in BRCA1 or BRCA2 (BRCA1/2) cause homologous recombination deficiency (HRD). Ovarian cancer (OvCa) patients harbouring HRD beyond BRCA1/2 mutation result in a state referred to as "BRCAness". OvCa with BRCAness could benefit from PARP inhibitors. This study aims to identify a signature to detect the BRCAness population at the transcriptome level. METHODS: We used a rank-based algorithm to develop a qualitative BRCAness signature for OvCa. Upregulation of CXCL1 with downregulation of SV2A and upregulation of LY9 with downregulation of CHRNB3 were constructed as the BRCAness signature (2 gene pairs, 2-GPS) for OvCa. RESULTS: OvCa samples that were classified as BRCAness by 2-GPS showed improved overall survival, progression-free survival and exhibited increased multi-omics alterations in homologous recombination genes and enhanced sensitivity to immune checkpoint blockade. BRCAness cells were sensitive to PARP inhibitors. By biological experiments, we validated SKOV3 cells and patients with HRD exhibited higher expression of CXCL1 than SV2A and higher expression of LY9 than CHRNB3 at mRNA level. Both SKOV3 and A2780 with HRD were sensitive to mitomycin C, cisplatin and olaparib. CONCLUSIONS: In conclusion, 2-GPS could robustly predict BRCAness OvCa at the individual level and extend the population who may benefit from PARP inhibitors.

SLAMF7 modulates B cells and adaptive immunity to regulate susceptibility to CNS autoimmunity.

BACKGROUND: Multiple sclerosis (MS) is a chronic, debilitating condition characterized by CNS autoimmunity stemming from a complex etiology involving both environmental and genetic factors. Our current understanding of MS points to dysregulation of the immune system as the pathogenic culprit, however, it remains unknown as to how the many genes associated with increased susceptibility to MS are involved. One such gene linked to MS susceptibility and known to regulate immune function is the self-ligand immune cell receptor SLAMF7. METHODS: We subjected WT and SLAMF7-/- mice to multiple EAE models, compared disease severity, and comprehensively profiled the CNS immune landscape of these mice. We identified all SLAMF7-expressing CNS immune cells and compared the entire CNS immune niche between genotypes. We performed deep phenotyping and in vitro functional studies of B and T cells via spectral cytometry and BioPlex assays. Adoptive transfer studies involving the transfer of WT and SLAMF7-/- B cells into B cell-deficient mice (µMT) were also performed. Finally, B-T cell co-culture studies were performed, and a comparative cell-cell interaction network derived from scRNA-seq data of SLAMF7+ vs. SLAMF7- human CSF immune cells was constructed. RESULTS: We found SLAMF7-/- mice to be more susceptible to EAE compared to WT mice and found SLAMF7 to be expressed on numerous CNS immune cell subsets. Absence of SLAMF7 did not grossly alter the CNS immune landscape, but allowed for altered immune cell subset infiltration during EAE in a model-dependent manner. Global lack of SLAMF7 expression increased myeloid cell activation states along with augmented T cell anti-MOG immunity. B cell profiling studies revealed increased activation states of specific plasma and B cell subsets in SLAMF7-/- mice during EAE, and functional co-culture studies determined that SLAMF7-/- B cells induce exaggerated T cell activation. Adoptive transfer studies revealed that the increased susceptibility of SLAMF7-/- mice to EAE is partly B cell dependent and reconstruction of the human CSF SLAMF7-interactome found B cells to be critical to cell-cell communication between SLAMF7-expressing cells. CONCLUSIONS: Our studies have identified novel roles for SLAMF7 in CNS immune regulation and B cell function, and illuminate underpinnings of the genetic association between SLAMF7 and MS.

CD84 Links T Cell and Platelet Activity in Cerebral Thrombo-Inflammation in Acute Stroke.

RATIONALE: Ischemic stroke is a leading cause of morbidity and mortality worldwide. Recanalization of the occluded vessel is essential but not sufficient to guarantee brain salvage. Experimental and clinical data suggest that infarcts often develop further due to a thromboinflammatory process critically involving platelets and T cells, but the underlying mechanisms are unknown. OBJECTIVE: We aimed to determine the role of CD (cluster of differentiation)-84 in acute ischemic stroke after recanalization and to dissect the underlying molecular thromboinflammatory mechanisms. METHODS AND RESULTS: Here, we show that mice lacking CD84-a homophilic immunoreceptor of the SLAM (signaling lymphocyte activation molecule) family-on either platelets or T cells displayed reduced cerebral CD4+ T-cell infiltration and thrombotic activity following experimental stroke resulting in reduced neurological damage. In vitro, platelet-derived soluble CD84 enhanced motility of wild-type but not of Cd84-/- CD4+ T cells suggesting homophilic CD84 interactions to drive this process. Clinically, human arterial blood directly sampled from the ischemic cerebral circulation indicated local shedding of platelet CD84. Moreover, high platelet CD84 expression levels were associated with poor outcome in patients with stroke. CONCLUSIONS: These results establish CD84 as a critical pathogenic effector and thus a potential pharmacological target in ischemic stroke.

Signaling Lymphocytic Activation Molecule Family-7 Alleviates Corneal Inflammation by Promoting M2 Polarization.

BACKGROUND: Signaling lymphocytic activation molecule family-7 (SLAMF7) functions as an immune checkpoint molecule on macrophages in antitumor immunity. However, its role in bacterial infection remains largely unknown. METHODS: Bone marrow-derived macrophages (BMDMs) isolated from wild-type (WT) or SLAMF7 knockout (KO) mice were infected with bacteria or treated with lipopolysaccharide/interferon-γ to investigate the expression and function of SLAMF7 in macrophage polarization. A Pseudomonas aeruginosa keratitis murine model was established to explore the effect of SLAMF7 on P. aeruginosa keratitis using WT vs SLAMF7 KO mice, or recombinant SLAMF7 vs phosphate-buffered saline-treated mice, respectively. RESULTS: SLAMF7 expression was enhanced on M1-polarized or bacterial-infected macrophages, and infiltrating macrophages in P. aeruginosa-infected mouse corneas. SLAMF7 promoted M2 polarization by inducing STAT6 activation. In vivo data showed that SLAMF7 KO aggravated, while treatment with recombinant SLAMF7 alleviated, corneal inflammation and disease severity. In addition, blockage of M2 polarization by Arg-1 inhibitor abrogated the effect of recombinant SLAMF7 in disease progression. CONCLUSIONS: SLAMF7 expression in macrophages was induced upon M1 polarization or bacterial infection and alleviated corneal inflammation and disease progression of P. aeruginosa keratitis by promoting M2 polarization. These findings may provide a potential strategy for the treatment of P. aeruginosa keratitis.

Evidence for the loss and recovery of SLAMF9 during human evolution: implications on Dollo's law.

Signaling lymphocyte activation molecule family member 9 (SLAMF9) is a cell surface protein of the CD2/SLAM family of leukocyte surface receptors. It is conserved throughout mammals and has roles in the initiation of inflammatory responses and regulation of plasmacytoid dendritic cell function. Through comparison of reference sequences encoding SLAMF9 in human, mouse, and primate sequences, we have determined that the SLAMF9 gene underwent successive mutation events, resulting in the loss of the protein and subsequent recovery of a less stable version. The mutations included a single base pair deletion in the second exon and a change in the splice acceptor site of that same exon. These changes would have had the effect of creating and later repairing a frameshift in the coding sequence. These events took place since the divergence of the human lineage from the chimpanzee-human last common ancestor and represent the first known case of the functional loss and recovery of a gene within the human lineage.

Expression and function of SLAMF6 in CD8+ T lymphocytes of patients with severe aplastic anemia.

This study investigated the expression status of signaling lymphocytic activation molecule family 6 (SLAMF6) in CD8+ T lymphocytes of patients with severe aplastic anemia (SAA) and its association with the clinical indicators and immune status of the disease. The effects of SLAMF6 on the function and apoptosis of CD8+ T lymphocytes were also investigated. Levels of SLAMF6 and SLAM-associated protein in the CD8+ T lymphocytes of SAA patients were significantly lower than the normal controls, and they were positively correlated with hematopoietic-related indicators but negatively correlated with the levels of functional molecules of CD8+ T lymphocytes. After blocking SLAMF6, CD8+ T lymphocyte functional molecule secretion was upregulated and RICD was downregulated in SAA patients, suggesting that SLAMF6, is involved in the pathogenetic mechanism of SAA by regulating CD8+ T lymphocyte functional molecule secretion and RICD levels. SLAMF6 may be a novel target for the regulation of CD8+ T lymphocyte homeostasis.

Affinity purification mass spectrometry analysis of PD-1 uncovers SAP as a new checkpoint inhibitor.

Programmed cell death-1 (PD-1) is an essential inhibitory receptor in T cells. Antibodies targeting PD-1 elicit durable clinical responses in patients with multiple tumor indications. Nevertheless, a significant proportion of patients do not respond to anti-PD-1 treatment, and a better understanding of the signaling pathways downstream of PD-1 could provide biomarkers for those whose tumors respond and new therapeutic approaches for those whose tumors do not. We used affinity purification mass spectrometry to uncover multiple proteins associated with PD-1. Among these proteins, signaling lymphocytic activation molecule-associated protein (SAP) was functionally and mechanistically analyzed for its contribution to PD-1 inhibitory responses. Silencing of SAP augmented and overexpression blocked PD-1 function. T cells from patients with X-linked lymphoproliferative disease (XLP), who lack functional SAP, were hyperresponsive to PD-1 signaling, confirming its inhibitory role downstream of PD-1. Strikingly, signaling downstream of PD-1 in purified T cell subsets did not correlate with PD-1 surface expression but was inversely correlated with intracellular SAP levels. Mechanistically, SAP opposed PD-1 function by acting as a molecular shield of key tyrosine residues that are targets for the tyrosine phosphatase SHP2, which mediates PD-1 inhibitory properties. Our results identify SAP as an inhibitor of PD-1 function and SHP2 as a potential therapeutic target in patients with XLP.

Computational Analysis Reveals a Critical Point Mutation in the N-Terminal Region of the Signaling Lymphocytic Activation Molecule Responsible for the Cross-Species Infection with Canine Distemper Virus.

Infection of hosts by morbilliviruses is facilitated by the interaction between viral hemagglutinin (H-protein) and the signaling lymphocytic activation molecule (SLAM). Recently, the functional importance of the n-terminal region of human SLAM as a measles virus receptor was demonstrated. However, the functional roles of this region in the infection process by other morbilliviruses and host range determination remain unknown, partly because this region is highly flexible, which has hampered accurate structure determination of this region by X-ray crystallography. In this study, we analyzed the interaction between the H-protein from canine distemper virus (CDV-H) and SLAMs by a computational chemistry approach. Molecular dynamics simulations and fragment molecular orbital analysis demonstrated that the unique His28 in the N-terminal region of SLAM from Macaca is a key determinant that enables the formation of a stable interaction with CDV-H, providing a basis for CDV infection in Macaca. The computational chemistry approach presented should enable the determination of molecular interactions involving regions of proteins that are difficult to predict from crystal structures because of their high flexibility.

Signalling lymphocyte activation molecule family member 9 is found on select subsets of antigen-presenting cells and promotes resistance to Salmonella infection.

Signalling lymphocyte activation molecule family member 9 (SLAMF9) is an orphan receptor of the CD2/SLAM family of leucocyte surface proteins. Examination of SLAMF9 expression and function indicates that SLAMF9 promotes inflammation by specialized subsets of antigen-presenting cells. Within healthy liver and circulating mouse peripheral blood mononuclear cells, SLAMF9 is expressed on CD11b+ , Ly6C- , CD11clow , F4/80low , MHC-II+ , CX3 CR1+ mononuclear phagocytes as well as plasmacytoid dendritic cells. In addition, SLAMF9 can be found on peritoneal B1 cells and small (F4/80low ), but not large (F4/80high ), peritoneal macrophages. Upon systemic challenge with Salmonella enterica Typhimurium, Slamf9-/- mice were impaired in their ability to clear the infection from the liver. In humans, SLAMF9 is up-regulated upon differentiation of monocytes into macrophages, and lipopolysaccharide stimulation of PMA-differentiated, SLAMF9 knockdown THP-1 cells showed an essential role of SLAMF9 in production of granulocyte-macrophage colony-stimulating factor, tumour necrosis factor-α, and interleukin-1ß. Taken together, these data implicate SLAMF9 in the initiation of inflammation and clearance of bacterial infection.

T cell reconstitution after lymphocyte depletion features a different pattern of inhibitory receptor expression in ABO- versus HLA-incompatible kidney transplant recipients.

Chronic antigen stimulation can lead to immune exhaustion (a state of T cell dysfunction). Several phenotypical signatures of T cell exhaustion have been described in various pathological situations, characterized by aberrant expression of multiple inhibitory receptors (IR). This signature has been barely studied in the context of allogenic organ transplantation. We undertook a cross-sectional analysis of the expression of IR [CD244, CD279, T cell immunoreceptor with immunoglobulin (Ig) and immunoreceptor tyrosine-based inhibition motif (ITIM) domains (TIGIT) and CD57] and their correlation with cytokine-producing functions in T cells reconstituting after lymphocyte depletion in patients transplanted from living donors, with preformed donor-specific antibodies. After ABO incompatible transplantation, T cells progressively acquired a phenotype similar to healthy donors and the expression of several IR marked cells with increased functions, with the exception of TIGIT, which was associated with decreased cytokine production. In stark contrast, T cell reconstitution in patients with anti-human leukocyte antigen (HLA) antibodies was characterized with an increased co-expression of IR by T cells, and specifically by an increased expression of TIGIT. Furthermore, expression of these receptors was no longer directly correlated to cytokine production. These results suggest that T cell alloreactivity in HLA-incompatible kidney transplantation drives an aberrant T cell reconstitution with respect to IR profile, which could have an impact on the transplantation outcome.

Diagnostic challenges for a novel SH2D1A mutation associated with X-linked lymphoproliferative disease.

Mutations in SH2D1A, encoding the intracellular adaptor signaling lymphocyte activation molecule associated protein (SAP), are associated with X-linked lymphoproliferative disease type 1 (XLP1). We identified a novel hemizygous SH2D1A c.49G > A (p.E17K) variant in a 21-year-old patient with fatal Epstein-Barr virus infection-associated hemophagocytic lymphohistiocytosis. Cellular and biochemical assays revealed normal expression of the SAP variant protein, yet binding to phosphorylated CD244 receptor was reduced by >95%. Three healthy brothers carried the SH2D1A c.49G > A variant. Thus, data suggest that this variant represents a pathogenic mutation, but with variable expressivity. Importantly, our results highlight challenges in the clinical interpretation of SH2D1A variants and caution in using functional flow cytometry assays for the diagnosis of XLP1.

2B4 Mediates Inhibition of CD8+ T Cell Responses via Attenuation of Glycolysis and Cell Division.

We recently showed that 2B4 expression on memory T cells in human renal transplant recipients was associated with reduced rates of rejection. To investigate whether 2B4 functionally underlies graft acceptance during transplantation, we established an experimental model in which 2B4 was retrogenically expressed on donor-reactive murine CD8+ T cells (2B4rg), which were then transferred into naive recipients prior to skin transplantation. We found that constitutive 2B4 expression resulted in significantly reduced accumulation of donor-reactive CD8+ T cells following transplantation and significantly prolonged graft survival following transplantation. This marked reduction in alloreactivity was due to reduced proliferation of CD8+ Thy1.1+ 2B4rg cells as compared with control cells, underpinned by extracellular flux analyses demonstrating that 2B4-deficient (2B4KO) CD8+ cells activated in vitro exhibited increased glycolytic capacity and upregulation of gene expression profiles consistent with enhanced glycolytic machinery as compared with wild type controls. Furthermore, 2B4KO CD8+ T cells primed in vivo exhibited significantly enhanced ex vivo uptake of a fluorescent glucose analogue. Finally, the proliferative advantage associated with 2B4 deficiency was only observed in the setting of glucose sufficiency; in glucose-poor conditions, 2B4KO CD8+ T cells lost their proliferative advantage. Together, these data indicate that 2B4 signals function to alter T cell glucose metabolism, thereby limiting the proliferation and accumulation of CD8+ T cells. Targeting 2B4 may therefore represent a novel therapeutic strategy to attenuate unwanted CD8+ T cell responses.

Structural and functional analysis of the signaling lymphocytic activation molecule family 7 (SLAMF7) gene in response to infection with coagulase-negative and coagulase-positive staphylococci.

Splice variants of the signaling lymphocytic activation molecule family 7 (SLAMF7) gene have been identified, and differences in the expression of this gene have been demonstrated at the mRNA level in the mammary glands of healthy and mastitis-infected dairy cows. At the same time, significant associations have been found between a deletion in the SLAM7 gene exon, the occurrence of different splice variants, and the occurrence of mastitis in one group of dairy cows. An expression study was conducted on 40 Polish Holstein-Friesian dairy cows of the Black and White variety (group I). Milk samples were taken for microbiological analysis 2 d before slaughter and examined for the presence of bacteria. Immediately after slaughter, mammary tissue samples were taken and divided into 3 groups according to the health status of the mammary gland: healthy (without pathogenic bacteria in milk), coagulase-negative staphylococci (CNS), and coagulase-positive staphylococci (CPS). Based on different SLAMF7 gene DNA fragments, 2 alternative variants of this gene (V1 and V2) and complete gene expression were identified. Separate analyses performed for each isoform showed that the health status of the cow was strongly associated with the expression level of individual variants. The highest expression was detected for the SLAMF7 complete amplicon in healthy cows, and in the CNS and CPS cows the expression of this variant was also higher than V1 and V2. Sanger sequencing was applied to detect the polymorphism/indel variant in the second exon of the SLAMF7 gene probably having the greatest effect on the protein structure and function of SLAMF7. Two genotypes were detected: AA (wild-type) and AB (insertion A). In healthy cows, the frequency of homozygotes AA was higher than the heterozygotes, whereas in the infected animals, the genotypic distribution was the opposite. An association analysis between the identified polymorphism and production traits-including somatic cell count, as well as lactose, protein, and casein content and yield as indicators of subclinical mastitis occurrence-was performed on the group II cows (166 Polish Holstein-Friesian dairy cows). Unfortunately, due to the low number of AB animals, no relationship was demonstrated between genotype in the second exon and the health status of cows. Additionally, the difference in the percentage of SLAMF7-targeted DNA methylation between the groups of animals was not significant, with an average of ∼66 to 68%.