Dual Chimeric Antigen Receptor T Cells Targeting CD38 and SLAMF7 with Independent Signaling Demonstrate Preclinical Efficacy and Safety in Multiple Myeloma

Chimeric antigen receptor (CAR) T-cell therapy for multiple myeloma targeting B-cell maturation antigen (BCMA) induces high overall response rates. However, relapse still occurs and novel strategies for targeting multiple myeloma cells using CAR T-cell therapy are needed. SLAMF7 (also known as CS1) and CD38 on tumor plasma cells represent potential alternative targets for CAR T-cell therapy in multiple myeloma, but their expression on activated T cells and other hematopoietic cells raises concerns about the efficacy and safety of such treatments. Here, we used CRISPR/Cas9 deletion of the CD38 gene in T cells and developed DCAR, a double CAR system targeting CD38 and CS1 through activation and costimulation receptors, respectively. Inactivation of CD38 enhanced the anti-multiple myeloma activity of DCAR T in vitro. Edited DCAR T cells showed strong in vitro and in vivo responses specifically against target cells expressing both CD38 and CS1. Furthermore, we provide evidence that, unlike anti-CD38 CAR T-cell therapy, which elicited a rapid immune reaction against hematopoietic cells in a humanized mouse model, DCAR T cells showed no signs of toxicity. Thus, DCAR T cells could provide a safe and efficient alternative to anti-BCMA CAR T-cell therapy to treat patients with multiple myeloma.

2B4: A potential target in Staphylococcus aureus associated allergic inflammation

Staphylococcus aureus (SA) and its exotoxins activate eosinophils (Eos) and mast cells (MCs) via CD48, a GPI-anchored receptor belonging to the signaling lymphocytes activation molecules (SLAM) family. 2B4 (CD244), an immuno-regulatory transmembrane receptor also belonging to the SLAM family, is the high-affinity ligand for CD48. 2B4 is expressed on several leukocytes including NK cells, T cells, basophils, monocytes, dendritic cells (DCs), and Eos. In the Eos and MCs crosstalk carried out by physical and soluble interactions (named the 'allergic effector unit', AEU), 2B4-CD48 binding plays a central role. As CD48 and 2B4 share some structural characteristics and SA colonization accompanies most of the allergic diseases, we hypothesized that SA exotoxins (e.g. Staphylococcus enterotoxin B, SEB) can also bind and activate 2B4 and thereby possibly further aggravate inflammation. To check our hypothesis, we used in vitro, in silico, and in vivo methods. By enzyme-linked immunosorbent assay (ELISA), flow cytometry (FC), fluorescence microscopy, and microscale thermophoresis, we have shown that SEB can bind specifically to 2B4. By Eos short- and long-term activation assays, we confirmed the functionality of the SEB-2B4 interaction. Using computational modeling, we identified possible SEB-binding sites on human and mouse 2B4. Finally, in vivo, in an SEB-induced peritonitis model, 2B4-KO mice showed a significant reduction of inflammatory features compared with WT mice. Altogether, the results of this study confirm that 2B4 is an important receptor in SEB-mediated inflammation, and therefore a role is suggested for 2B4 in SA associated inflammatory conditions.

A novel tumor purity and immune infiltration-related model for predicting distant metastasis-free survival in prostate cancer

BACKGROUND

umor cells, immune cells and stromal cells jointly modify tumor development and progression. We aim to explore the potential effects of tumor purity on the immune microenvironment, genetic landscape and prognosis in prostate cancer (PCa).

METHODS

Tumor purity of prostate cancer patients was extracted from The cancer genome atlas (TCGA). Immune cellular proportions were calculated by the CIBERSORT. To identify critical modules related to tumor purity, we used weighted gene co-expression network analysis (WGCNA). Using STRING and Cytoscape, protein-protein interaction (PPI) networks were constructed and analyzed. A Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, Disease Ontology (DO), and Gene Set Enrichment Analysis (GSEA) enrichment analysis of identified modules was conducted. To identify the expression of key genes at protein levels, we used the Human Protein Atlas (HPA) platform.

RESULTS

A model of tumor purity score (TPS) was constructed in the gene expression omnibus series (GSE) 116,918 cohort. TCGA cohort served as a validation set and was employed to validate the TPS. TPS model, as an independent prognostic factor of distant metastasis-free survival (DMFS) in PCa. Patients had higher tumor purity and better prognosis in the low-TPS group. Tumor purity was related to the infiltration of mast cells and macrophage cells positively, whereas related to the infiltration of dendritic cells, T cells and B cells negatively in PCa. The nomogram based on TPS, Age, Gleason score and T stage had a good predictive value and could evaluate the prognosis of PCa metastasis. GO and KEGG enrichment analyses showed that hub genes mainly participate in T cell activation and T-helper lymphocytes (TH) differentiation. Hub genes were mainly enriched in primary immunodeficiency disease, according to DO analysis. SLAMF8 was identified as the most critical gene by Cytoscape and HPA analysis.

CONCLUSIONS

Dynamic changes in the immune microenvironment associated with tumor purity could correlate with a poor DMFS of low-purity PCa. The TPS can predict the DMFS of PCa. In addition, prostate cancer metastases may be related to immunosuppression caused by a disorder of the immune microenvironment.

Mitochondrial ROS-dependent CD4+PD-1+T cells are pathological expansion in patients with primary immune thrombocytopenia

OBJECTIVE

Aberrant-activated T cells, especially CD4+T cells, play a crucial part in the pathogenetic progress of immune thrombocytopenia (ITP). PD-1-mediated signals play a negative part in the activation of CD4+T cells. However, knowledge is limited on the pathogenic characteristics and function of CD4+PD-1+T cells in ITP.

MATERIALS AND METHODS

The frequency and phenotype including cell activation, apoptosis, and cytokine production of CD4+PD-1+T cells were evaluated by flow cytometry. PD-1 Ligation Assay was performed to assess the function of PD-1 pathway in CD4+T cells. Mitochondrial reactive oxygen species (mtROS) were detected by MitoSOX Red probe.

RESULTS

Compared with healthy controls (HC), the frequencies of CD4+PD-1+T cells were significantly increased in ITP patients. However, these cells are not exhausted despite PD-1 expression. Besides retaining cytokine-producing potential, these CD4+PD-1+T cells also had a possible B-cell helper function including expressing ICOS, CD84, and CD40L. Moreover, the CD4+PD-1+T cell subset contained higher levels of mitochondrial ROS than CD4+PD-1-T cell subset in patients with ITP. And mtROS inhibition could reduce the secretion of the inflammatory cytokines and regulate the function of CD4+PD-1+T cells. Upon in-vitro T cell receptor (TCR) stimulation of CD4+T cells in the presence of plate-bound PD-L1 fusion protein (PD-L1-Ig), CD4+T cells from ITP patients appeared resistant to such PD-1-mediated inhibition of interferon (IFN)-γ secretion.

CONCLUSIONS

The CD4+PD-1+T cells were more abundant in patients with ITP. Additionally, this CD4+PD-1+T cell subset may be a potential etiology of ITP and a potential immune therapeutic target for ITP patients in the future.

Evaluation of mRNA Expression of CD244 and Its Adapter Molecules in CD8+ T Cells in Acute Leukemia

Background

This study investigated the role of the immune-checkpoint receptor (ICR), CD244, and its adapter molecules, in CD8+ T cells in acute leukemia.

Methods

Blood samples were obtained from 21 acute lymphoblastic leukemia (ALL) and 6 acute myeloid leukemia (AML) patients and 20 control subjects. Relative gene expression of CD244, immune receptor tyrosine-based switch motif-associated protein (SA), EWS/FLI1-activated transcript 2 (EAT-2), and LncRNA-GSTT1-AS1 were evaluated using quantitative reverse transcription polymerase chain reaction.

Results

Expression of CD244, SAP, and EAT-2 were significantly lower in CD8+ T cells from ALL patients than those from control subjects. Interestingly, the expression of SAP was much lower than that of CD244, indicating a lower ratio of SAP to CD244. Also, SAP expression was significantly lower in AML patients compared to the control group. Expression of LncRNA-GSTT1-AS1 showed no significant difference in ALL and AML patients compared to control subjects.

Conclusion

The low SAP/CD244 expression ratio in CD8+ T cells in ALL suggests an inhibitory role for CD244 in ALL.

Evaluation of mRNA Expression of CD244 and Its Adapter Molecules in CD8+ T Cells in Acute Leukemia

Background

This study investigated the role of the immune-checkpoint receptor (ICR), CD244, and its adapter molecules, in CD8+ T cells in acute leukemia.

Methods

Blood samples were obtained from 21 acute lymphoblastic leukemia (ALL) and 6 acute myeloid leukemia (AML) patients and 20 control subjects. Relative gene expression of CD244, immune receptor tyrosine-based switch motif-associated protein (SA), EWS/FLI1-activated transcript 2 (EAT-2), and LncRNA-GSTT1-AS1 were evaluated using quantitative reverse transcription polymerase chain reaction.

Results

Expression of CD244, SAP, and EAT-2 were significantly lower in CD8+ T cells from ALL patients than those from control subjects. Interestingly, the expression of SAP was much lower than that of CD244, indicating a lower ratio of SAP to CD244. Also, SAP expression was significantly lower in AML patients compared to the control group. Expression of LncRNA-GSTT1-AS1 showed no significant difference in ALL and AML patients compared to control subjects.

Conclusion

The low SAP/CD244 expression ratio in CD8+ T cells in ALL suggests an inhibitory role for CD244 in ALL.

Tim-3, PD-1, CD244 and Foxp3 Positive T Cells' Relation to the Prognosis of Dermatomyositis and Polymyositis Patients

OBJECTIVE

To explore the frequency of circulating CD4+ T cells expressing PD-1+, TIM-3+ in polymyositis (PM) and dermatomyositis (DM) patients and its correlation with inflammatory factors, CD244+ and FOXP3+ T cell subtypes and prognosis.

STUDY DESIGN

Observational study. Place and Duration of the Study: Ganzhou people's Hospital, Ganzhou, Jiangxi, China, from July 2019 to June 2021.

METHODOLOGY

PM and DM patients were treated according to the institution's guidelines and followed up for 2 years. Fifty healthy volunteers were enrolled as controls. Serum interleukin (IL)-6, C-reactive protein (CRP), IL-17, and tumour necrosis factor α (TNF-α) levels were detected by enzyme-linked immunosorbent assay (ELISA). TIM-3+, PD-1+, CD244+, and FOXP3+ expressions were measured using flow cytometry. Inability to live normally, recurrence or death was defined as poor prognosis.

RESULTS

The ESR, ALT, AST, LDH and ferritin concentration in PM/DM patients were remarkably elevated than that in healthy volunteers. The frequencies of PD-1+, TIM-3+, CD244+, and FOXP3+ were all remarkably enhanced in PM/DM patients compared with the healthy volunteers. The frequencies of PD-1+, TIM-3+, FOXP3+, and TIM-3+/PD-1+ T cells were significantly elevated in the poor prognosis group compared with the good prognosis group. The frequency of CD4+TIM-3+PD-1+ had satisfactory diagnostic value for PM/DM patients with bad prognoses. IL-17, TIM-3+, PD-1+and TIM-3+ PD-1+ were the risk factors for PM/DM patients with bad outcomes.

CONCLUSION

The frequency of circulating CD4+ T cells expressing TIM-3+PD-1+ could be used to predict the prognosis of PM/DM patients.

KEY WORDS

Tim-3, PD-1, Dermatomyositis, Polymyositis, Inflammatory.

Differentiation-related genes in tumor-associated macrophages as potential prognostic biomarkers in non-small cell lung cancer

Background

The purpose of this study was to evaluate the role of differentiation-related genes (DRGs) in tumor-associated macrophages (TAMs) in non-small cell lung cancer (NSCLC).

Methods

Single cell RNA-seq (scRNA-seq) data from GEO and bulk RNA-seq data from TCGA were analyzed to identify DRGs using trajectory method. Functional gene analysis was carried out by GO/KEGG enrichment analysis. The mRNA and protein expression in human tissue were analyzed by HPA and GEPIA databases. To investigate the prognostic value of these genes, three risk score (RS) models in different pathological types of NSCLC were generated and predicted NSCLC prognosis in datasets from TCGA, UCSC and GEO databases.

Results

1,738 DRGs were identified through trajectory analysis. GO/KEGG analysis showed that these genes were predominantly related to myeloid leukocyte activation and leukocyte migration. 13 DRGs (C1QB, CCL4, CD14, CD84, FGL2, MS4A6A, NLRP3, PLEK, RNASE6, SAMSN1, SPN, TMEM176B, ZEB2) related to prognosis were obtained through univariate Cox analysis and Lasso regression. C1QB, CD84, FGL2, MS4A6A, NLRP3, PLEK, SAMSN1, SPN, and ZEB2 were downregulated in NSCLC compared to non-cancer tissue. The mRNA of 13 genes were significantly expressed in pulmonary macrophages with strong cell specificity. Meanwhile, immunohistochemical staining showed that C1QB, CCL4, SPN, CD14, NLRP3, SAMSN1, MS4A6A, TMEM176B were expressed in different degrees in lung cancer tissues. ZEB2 (HR=1.4, P<0.05) and CD14 (HR=1.6, P<0.05) expression were associated with a worse prognosis in lung squamous cell carcinoma; ZEB2 (HR=0.64, P<0.05), CD84 (HR=0.65, P<0.05), PLEK (HR=0.71, P<0.05) and FGL2 (HR=0.61, P<0.05) expression were associated with a better prognosis in lung adenocarcinoma. Three RS models based on 13 DRGs both showed that the high RS was significantly associated with poor prognosis in different pathological types of NSCLC.

Conclusions

This study highlights the prognostic value of DRGs in TAMs in NSCLC patients, providing novel insights for the development of therapeutic and prognostic targets based on TAM functional differences.

CD229 interacts with RASAL3 to activate RAS/ERK pathway in multiple myeloma proliferation

Multiple myeloma (MM) is an incurable plasma cell malignancy, while CAR-T therapy offers a new direction for the treatment of MM. Recently, signaling lymphocytic activation molecule family 3 (CD229), a cell surface immune receptor belonging to the signaling lymphocyte activating molecule family (SLAMF), is emerging as a CAR-T therapeutic target in MM. However, a clear role of CD229 in MM remains elusive. In this study, MM patients with elevated CD229 expression achieved poor prognosis by analyzing MM clinical databases. In addition, CD229 promoted MM cell proliferation in vitro as well as in xenograft mouse model in vivo. Mechanism study revealed that CD229 promoted MM cell proliferation by regulating the RAS/ERK signaling pathway. Further exploration employed co-immunoprecipitation coupled with mass spectrometry to identify RASAL3 as an important downstream protein of CD229. Additionally, we developed a co-culture method combined with the immunofluorescence assay to confirm that intercellular tyrosine phosphorylation mediated self-activation of CD229 to activate RAS/ERK signaling pathway via interacting with RASAL3. Taken together, these findings not only demonstrate the oncogenic role of CD229 in MM cell proliferation, but also illustrate the potential of CD229 as a promising therapeutic target for MM treatment.

Increased TOX expression concurrent with PD-1, Tim-3, and CD244 expression in T cells from patients with acute myeloid leukemia

BACKGROUND

T cell dysregulation is a common event in leukemia. Recent findings have indicated that aberrant expression of immune checkpoint proteins may be associated with disease relapse and progression in acute myeloid leukemia (AML). TOX, a transcription factor in the HMG-box protein superfamily, was found to be a potential target for immunotherapy not only in solid tumors but also in hematological malignancies. However, little is known about TOX expression and co-expression with immune checkpoint proteins or the exhausted phenotype in the T cell subsets in AML. Thus, in this study, we analyzed TOX expression and co-expression with PD-1, Tim-3, and CD244 in T cells.

METHODS

TOX expression and co-expression with PD-1, Tim-3, and CD244 in CD3+, CD4+, regulatory T (Treg), and CD8+ T cells were analyzed by multi-color fluorescent flow cytometry in peripheral blood (PB) and bone marrow (BM) samples from patients with de novo AML and AML in complete remission (CR) and healthy individuals (HIs).

RESULTS

A significantly increased percentage of TOX+CD3+, CD4+, and CD8+ T cells was found in PB from patients with de novo AML in comparison with HIs. Double-positive TOX+CD244+, TOX+PD-1+, and TOX+Tim-3+ T cells markedly increased in the CD3+, CD4+, and CD8+ T cell populations in de novo AML patients compared with HIs, and similar trends were demonstrated for TOX+Tim-3+CD3+/CD4+/CD8+ T cells in de novo AML compared with AML-CR patients. In addition, the number of TOX+, TOX+PD-1+, and TOX+Tim-3+Treg cells significantly increased in de novo AML patients compared with HIs, and TOX+PD-1+Treg cells were higher in de novo AML compared with AML-CR patients. Moreover, TOX positively correlated with Tim-3 expression in CD8+ and Treg cells, and a positive correlation between the expression of TOX+ CD4+ and CD244+CD4+ T cells was found. Furthermore, an increased percentage of TOX+Tim-3+ T cells in BM was also found in de novo AML patients compared with HIs.

CONCLUSIONS

Increased TOX concurrent with PD-1, Tim-3, and CD244 in T cells may contribute to T cell exhaustion and impair their function in AML. Such exhausted T cells may be partially revised when AML patients achieve CR after chemotherapy. TOX may be considered a potential target for reversing T cell exhaustion and improving T cell function in AML.

New twists in humoral immune regulation by SLAM family receptors

SLAM family receptors are involved in humoral immune regulation. In this issue of JEM, Zhong et al. (2021. J. Exp. Med.https://doi.org/10.1084/jem.20200756) provide evidence that these receptors collectively suppress germinal center reaction but promote production of antigen-specific antibodies.

Activation by SLAM Family Receptors Contributes to NK Cell Mediated "Missing-Self" Recognition

Natural Killer (NK) cells attack normal hematopoietic cells that do not express inhibitory MHC class I (MHC-I) molecules, but the ligands that activate NK cells remain incompletely defined. Here we show that the expression of the Signaling Lymphocyte Activation Molecule (SLAM) family members CD48 and Ly9 (CD229) by MHC-I-deficient tumor cells significantly contributes to NK cell activation. When NK cells develop in the presence of T cells or B cells that lack inhibitory MHC-I but express activating CD48 and Ly9 ligands, the NK cells’ ability to respond to MHC-I-deficient tumor cells is severely compromised. In this situation, NK cells express normal levels of the corresponding activation receptors 2B4 (CD244) and Ly9 but these receptors are non-functional. This provides a partial explanation for the tolerance of NK cells to MHC-I-deficient cells in vivo. Activating signaling via 2B4 is restored when MHC-I-deficient T cells are removed, indicating that interactions with MHC-I-deficient T cells dominantly, but not permanently, impair the function of the 2B4 NK cell activation receptor. These data identify an important role of SLAM family receptors for NK cell mediated “missing-self” reactivity and suggest that NK cell tolerance in MHC-I mosaic mice is in part explained by an acquired dysfunction of SLAM family receptors.

The cell surface receptor Slamf6 modulates innate immune responses during Citrobacter rodentium-induced colitis

The homophilic cell surface receptors CD150 (Slamf1) and CD352 (Slamf6) are known to modulate adaptive immune responses. Although the Th17 response was enhanced in Slamf6(-/-) C57BL/6 mice upon oral infection with Citrobacter rodentium, the pathologic consequences are indistinguishable from an infection of wild-type C57BL/6 mice. Using a reporter-based binding assay, we show that Slamf6 can engage structures on the outer cell membrane of several Gram(-) bacteria. Therefore, we examined whether Slamf6, like Slamf1, is also involved in innate responses to bacteria and regulates peripheral inflammation by assessing the outcome of C. rodentium infections in Rag(-/-) mice. Surprisingly, the pathology and immune responses in the lamina propria of C. rodentium-infected Slamf6(-/-) Rag(-/-) mice were markedly reduced as compared with those of Rag(-/-) mice. Infiltration of inflammatory phagocytes into the lamina propria was consistently lower in Slamf6(-/-) Rag(-/-) mice than in Rag(-/-) animals. Concomitant with the reduced systemic translocation of the bacteria was an enhanced production of IL-22, suggesting that Slamf6 suppresses a mucosal protective program. Furthermore, administering a mAb (330) that inhibits bacterial interactions with Slamf6 to Rag(-/-) mice ameliorated the infection compared with a control antibody. We conclude that Slamf6-mediated interactions of colonic innate immune cells with specific Gram(-) bacteria reduce mucosal protection and enhance inflammation, contributing to lethal colitis that is caused by C. rodentium infections in Rag(-/-) mice.

Elotuzumab Therapy for Relapsed or Refractory Multiple Myeloma

BACKGROUND

Elotuzumab, an immunostimulatory monoclonal antibody targeting signaling lymphocytic activation molecule F7 (SLAMF7), showed activity in combination with lenalidomide and dexamethasone in a phase 1b-2 study in patients with relapsed or refractory multiple myeloma.

METHODS

In this phase 3 study, we randomly assigned patients to receive either elotuzumab plus lenalidomide and dexamethasone (elotuzumab group) or lenalidomide and dexamethasone alone (control group). Coprimary end points were progression-free survival and the overall response rate. Final results for the coprimary end points are reported on the basis of a planned interim analysis of progression-free survival.

RESULTS

Overall, 321 patients were assigned to the elotuzumab group and 325 to the control group. After a median follow-up of 24.5 months, the rate of progression-free survival at 1 year in the elotuzumab group was 68%, as compared with 57% in the control group; at 2 years, the rates were 41% and 27%, respectively. Median progression-free survival in the elotuzumab group was 19.4 months, versus 14.9 months in the control group (hazard ratio for progression or death in the elotuzumab group, 0.70; 95% confidence interval, 0.57 to 0.85; P<0.001). The overall response rate in the elotuzumab group was 79%, versus 66% in the control group (P<0.001). Common grade 3 or 4 adverse events in the two groups were lymphocytopenia, neutropenia, fatigue, and pneumonia. Infusion reactions occurred in 33 patients (10%) in the elotuzumab group and were grade 1 or 2 in 29 patients.

CONCLUSIONS

Patients with relapsed or refractory multiple myeloma who received a combination of elotuzumab, lenalidomide, and dexamethasone had a significant relative reduction of 30% in the risk of disease progression or death. (Funded by Bristol-Myers Squibb and AbbVie Biotherapeutics; ELOQUENT-2 ClinicalTrials.gov number, NCT01239797.).

Whole-exome DNA sequence analysis of Brca2- and Trp53-deficient mouse mammary gland tumours

Germline mutations in the tumour suppressor BRCA2 predispose to breast, ovarian and a number of other human cancers. Brca2-deficient mouse models are used for preclinical studies but the pattern of genomic alterations in these tumours has not yet been described in detail. We have performed whole-exome DNA sequencing analysis of mouse mammary tumours from Blg-Cre Brca2(f/f) Trp53(f/f) animals, a model of BRCA2-deficient human cancer. We also used the sequencing data to estimate DNA copy number alterations in these tumours and identified a recurrent copy number gain in Met, which has been found amplified in other mouse mammary cancer models. Through a comparative genomic analysis, we identified several mouse Blg-Cre Brca2(f/f) Trp53(f/f) mammary tumour somatic mutations in genes that are also mutated in human cancer, but few of these genes have been found frequently mutated in human breast cancer. A more detailed analysis of these somatic mutations revealed a set of genes that are mutated in human BRCA2 mutant breast and ovarian tumours and that are also mutated in mouse Brca2-null, Trp53-null mammary tumours. Finally, a DNA deletion surrounded by microhomology signature found in human BRCA1/2-deficient cancers was not common in the genome of these mouse tumours. Although a useful model, there are some differences in the genomic landscape of tumours arising in Blg-Cre Brca2(f/f) Trp53(f/f) mice compared to human BRCA-mutated breast cancers. Therefore, this needs to be taken into account in the use of this model.

Identification of novel chicken CD4⁺ CD3⁻ blood population with NK cell like features

Chicken NK cells have been defined in embryonic spleen and intestinal epithelium as CD8(+) lymphoid cells that lack BCR and TCR, whereas blood NK cells have not been phenotypically defined. Here we employed the mab, 8D12 directed against CHIR-AB1, a chicken Fc receptor, to define a previously uncharacterized lymphoid cell population in the blood. Although CHIR-AB1 expression was found on several cell populations, cells with extraordinary high CHIR-AB1 levels ranged between 0.4 and 2.8% in five different chicken lines. The widespread applicability of the CHIR-AB1 mab was unexpected, since CHIR-AB1-like genes form a polygenic and polymorphic subfamily. Surprisingly the CHIR-AB1 high cells coexpressed low MHCII, low CD4 and CD5, while other T cell markers CD3 and CD8, the B cell marker Bu1, the macrophage marker KUL01 were absent. Moreover, they stained with the mab 28-4, 20E5 and 1G7, which define chicken NK cells and they also expressed CD25, CD57, CD244 and the vitronectin receptor (αVβ3 integrin). In functional assays, PMA stimulation led to high levels of IFNγ release, while spontaneous cytotoxicity was not detectable. The expression of typical NK cell markers in the absence of characteristic B- or T-cell markers, and their IFNγ release is suggestive of a yet unidentified NK like population.

Mice lacking the SLAM family member CD84 display unaltered platelet function in hemostasis and thrombosis

Background

Platelets are anuclear cell fragments derived from bone marrow megakaryocytes that safeguard vascular integrity by forming thrombi at sites of vascular injury. Although the early events of thrombus formation—platelet adhesion and aggregation—have been intensively studied, less is known about the mechanisms and receptors that stabilize platelet-platelet interactions once a thrombus has formed. One receptor that has been implicated in this process is the signaling lymphocyte activation molecule (SLAM) family member CD84, which can undergo homophilic interactions and becomes phosphorylated upon platelet aggregation.

Objective

The role of CD84 in platelet physiology and thrombus formation was investigated in CD84-deficient mice.

Methods and Results

We generated CD84-deficient mice and analyzed their platelets in vitro and in vivo. Cd84^−/− platelets exhibited normal activation and aggregation responses to classical platelet agonists. Furthermore, CD84 deficiency did not affect integrin-mediated clot retraction and spreading of activated platelets on fibrinogen. Notably, also the formation of stable three-dimensional thrombi on collagen-coated surfaces under flow ex vivo was unaltered in the blood of Cd84^−/− mice. In vivo, Cd84^−/− mice exhibited unaltered hemostatic function and arterial thrombus formation.

Conclusion

These results show that CD84 is dispensable for thrombus formation and stabilization, indicating that its deficiency may be functionally compensated by other receptors or that it may be important for platelet functions different from platelet-platelet interactions.

MHC-I molecules selectively inhibit cell-mediated cytotoxicity triggered by ITAM-coupled activating receptors and 2B4

NK cell effector functions are controlled by a combination of inhibitory receptors, which modulate NK cell activation initiated by stimulatory receptors. Most of the canonical NK cell inhibitory receptors recognize allelic forms of classical and non-classical MHC class I molecules. Furthermore, high expression of MHC-I molecules on effector immune cells is also associated with reverse signaling, giving rise to several immune-regulatory functions. Consequently, the inhibitory function of MHC class I expressed on a human NKL cell line and activated primary NK and T cells on different activating receptors are analyzed in this paper. Our results reveal that MHC-I molecules display specific patterns of “selective” inhibition over cytotoxicity and cytokine production induced by ITAM-dependent receptors and 2B4, but not on NKG2D. This contrasts with the best known “canonical” inhibitory receptors, which constitutively inhibit both functions, regardless of the activating receptor involved. Our results support the existence of a new fine-tuner inhibitory function for MHC-I molecules expressed on cytotoxic effector cells that could be involved in establishing self-tolerance in mature activated NK cells, and could also be important in tumor and infected cell recognition.

The effect of adjuvanting cancer vaccines with herpes simplex virus glycoprotein D on melanoma-driven CD8+ T cell exhaustion

Two vaccines expressing CD4(+) and CD8(+) T cell epitopes of melanoma-associated Ags (MAAs) by a chimpanzee-derived replication-defective AdC68 vector were compared in a mouse model of melanoma. In one vaccine, termed AdC68-gDMelapoly, the epitopes were expressed as a fusion protein within HSV-1 glycoprotein D (gD), which blocks immunoinhibitory signaling through the herpes virus entry mediator pathway. The other vaccine, termed AdC68-Melapoly, expressed only the MAA epitopes. AdC68-gDMelapoly induced more potent MAA-specific CD8(+) T cell responses especially to the subdominant MAA epitopes. Upon prophylactic vaccination, mice that developed CD8(+) T cell responses to the two vaccines that were comparable in magnitude showed equal protection against tumor challenge. When mice were first challenged with tumor cells and then vaccinated results differed. In animals with comparable CD8(+) T cell responses, the AdC68-gDMelapoly vaccine was more efficacious compared with the AdC68-Melapoly vaccine in delaying tumor growth. This effect was linked to reduced expression of 2B4, LAG-3, and programmed death-1 on tumor-infiltrating MAA-specific CD8(+) T cells elicited by the gD-adjuvanted vaccine, suggesting that CD8(+) T cells induced in presence of gD are less susceptible to tumor-driven exhaustion.

The expression of the hepatocyte SLAMF3 (CD229) receptor enhances the hepatitis C virus infection

Hepatitis C virus (HCV) is a leading cause of cirrhosis and liver cancer worldwide. We recently characterized for the first time the expression of Signaling Lymphocyte Activating Molecule 3 (SLAMF3) in human hepatocytes and here, we report that SLAMF3 interacts with the HCV viral protein E2 and is implicated in HCV entry process. We found a strong correlation between SLAMF3 expression level and hepatocyte susceptibility to HCV infection. The use of specific siRNAs to down-modulate SLAMF3 expression and SLAMF3-blocking antibodies both decreased the hepatocytes susceptibility to HCV infection. Moreover, SLAMF3 over-expression significantly increased susceptibility to HCV infection. Interestingly, experiments with peptides derived from each SLAMF3 domain showed that the first N-terminal extracellular domain is essential for interaction with HCV particles. Finally, we showed that recombinant HCV envelop protein E2 can bind SLAMF3 and that anti-SLAMF3 antibodies inhibited specifically this interaction. Overall, our results revealed that SLAMF3 plays a role during HCV entry, likely by enhancing entry of viral particle within hepatocytes.

Phenotypic T cell exhaustion in a murine model of bacterial infection in the setting of pre-existing malignancy

While much of cancer immunology research has focused on anti-tumor immunity both systemically and within the tumor microenvironment, little is known about the impact of pre-existing malignancy on pathogen-specific immune responses. Here, we sought to characterize the antigen-specific CD8⁺ T cell response following a bacterial infection in the setting of pre-existing pancreatic adenocarcinoma. Mice with established subcutaneous pancreatic adenocarcinomas were infected with Listeria monocytogenes, and antigen-specific CD8⁺ T cell responses were compared to those in control mice without cancer. While the kinetics and magnitude of antigen-specific CD8⁺ T cell expansion and accumulation was comparable between the cancer and non-cancer groups, bacterial antigen-specific CD8⁺ T cells and total CD4⁺ and CD8⁺ T cells in cancer mice exhibited increased expression of the coinhibitory receptors BTLA, PD-1, and 2B4. Furthermore, increased inhibitory receptor expression was associated with reduced IFN-γ and increased IL-2 production by bacterial antigen-specific CD8⁺ T cells in the cancer group. Taken together, these data suggest that cancer's immune suppressive effects are not limited to the tumor microenvironment, but that pre-existing malignancy induces phenotypic exhaustion in T cells by increasing expression of coinhibitory receptors and may impair pathogen-specific CD8⁺ T cell functionality and differentiation.

Fine specificity and molecular competition in SLAM family receptor signalling

SLAM family receptors regulate activation and inhibition in immunity through recruitment of activating and inhibitory SH2 domain containing proteins to immunoreceptor tyrosine based switch motifs (ITSMs). Binding of the adaptors, SAP and EAT-2 to ITSMs in the cytoplasmic regions of SLAM family receptors is important for activation. We analysed the fine specificity of SLAM family receptor phosphorylated ITSMs and the conserved tyrosine motif in EAT-2 for SH2 domain containing signalling proteins. Consistent with the literature describing dependence of CRACC (SLAMF7) on EAT-2, CRACC bound EAT-2 (K_D = 0.003 μM) with approximately 2 orders of magnitude greater affinity than SAP (K_D = 0.44 μM). RNA interference in cytotoxicity assays in NK92 cells showed dependence of CRACC on SAP in addition to EAT-2, indicating selectivity of SAP and EAT-2 may depend on the relative concentrations of the two adaptors. The concentration of SAP was four fold higher than EAT-2 in NK92 cells. Compared with SAP, the significance of EAT-2 recruitment and its downstream effectors are not well characterised. We identified PLCγ1 and PLCγ2 as principal binding partners for the EAT-2 tail. Both PLCγ1 and PLCγ2 are functionally important for cytotoxicity in NK92 cells through CD244 (SLAMF4), NTB-A (SLAMF6) and CRACC. Comparison of the specificity of SH2 domains from activating and inhibitory signalling mediators revealed a hierarchy of affinities for CD244 (SLAMF4) ITSMs. While binding of phosphatase SH2 domains to individual ITSMs of CD244 was weak compared with SAP or EAT-2, binding of tandem SH2 domains of SHP-2 to longer peptides containing tandem phosphorylated ITSMs in human CD244 increased the affinity ten fold. The concentration of the tyrosine phosphatase, SHP-2 was in the order of a magnitude higher than the adaptors, SAP and EAT-2. These data demonstrate a mechanism for direct recruitment of phosphatases in inhibitory signalling by ITSMs, while explaining competitive dominance of SAP and EAT-2.

HTLV-1 specific CD8+ T cell function augmented by blockade of 2B4/CD48 interaction in HTLV-1 infection

CD8+ T cell response is important in the response to viral infections; this response though is regulated by inhibitory receptors. Expression of inhibitory receptors has been positively correlated with CD8+ T cell exhaustion; the consequent effect of simultaneous blockade of these inhibitory receptors on CD8+ T cell response in viral infections have been studied, however, the role of individual blockade of receptor-ligand pair is unclear. 2B4/CD48 interaction is involved in CD8+T cell regulation, its signal transducer SAP (signaling lymphocyte activation molecule (SLAM)-associated protein) is required for stimulatory function of 2B4/CD244 on lymphocytes hence, we analyzed 2B4/CD244 (natural killer cell receptor) and SAP (signaling lymphocyte activation molecule(SLAM)-associated protein) on total CD8+ and HTLV-1 specific CD8+T cells in HTLV-1 infection and the effect of blockade of interaction with ligand CD48 on HTLV-1 specific CD8+ T cell function. We observed a high expression of 2B4/CD244 on CD8+ T cells relative to uninfected and further upregulation on HTLV-1 specific CD8+ T cells. 2B4+ CD8+ T cells exhibited more of an effector and terminally differentiated memory phenotype. Blockade of 2B4/CD48 interaction resulted in improvement in function via perforin expression and degranulation as measured by CD107a surface mobilization on HTLV-1 specific CD8+ T cells. In the light of these findings, we thus propose an inhibitory role for 2B4/CD48 interaction on CD8+T cell function.

Identification of SLAMF3 (CD229) as an inhibitor of hepatocellular carcinoma cell proliferation and tumour progression

Although hepatocellular carcinoma (HCC) is one of the most common malignancies and constitutes the third leading cause of cancer-related deaths, the underlying molecular mechanisms are not fully understood. In the present study, we demonstrate for the first time that hepatocytes express signalling lymphocytic activation molecule family member 3 (SLAMF3/CD229) but not other SLAMF members. We provide evidence to show that SLAMF3 is involved in the control of hepatocyte proliferation and in hepatocellular carcinogenesis. SLAMF3 expression is significantly lower in primary human HCC samples and HCC cell lines than in human healthy primary hepatocytes. In HCC cell lines, the restoration of high levels of SLAMF3 expression inhibited cell proliferation and migration and enhanced apoptosis. Furthermore, SLAMF3 expression was associated with inhibition of HCC xenograft progression in the nude mouse model. The restoration of SLAMF3 expression levels also decreased the phosphorylation of MAPK ERK1/2, JNK and mTOR. In samples from resected HCC patients, SLAMF3 expression levels were significantly lower in tumorous tissues than in peritumoral tissues. Our results identify SLAMF3 as a specific marker of normal hepatocytes and provide evidence for its potential role in the control of proliferation of HCC cells.

Elotuzumab directly enhances NK cell cytotoxicity against myeloma via CS1 ligation: evidence for augmented NK cell function complementing ADCC

Elotuzumab is a monoclonal antibody in development for multiple myeloma (MM) that targets CS1, a cell surface glycoprotein expressed on MM cells. In preclinical models, elotuzumab exerts anti-MM efficacy via natural killer (NK)-cell-mediated antibody-dependent cellular cytotoxicity (ADCC). CS1 is also expressed at lower levels on NK cells where it acts as an activating receptor. We hypothesized that elotuzumab may have additional mechanisms of action via ligation of CS1 on NK cells that complement ADCC activity. Herein, we show that elotuzumab appears to induce activation of NK cells by binding to NK cell CS1 which promotes cytotoxicity against CS1(+) MM cells but not against autologous CS1(+) NK cells. Elotuzumab may also promote CS1-CS1 interactions between NK cells and CS1(+) target cells to enhance cytotoxicity in a manner independent of ADCC. NK cell activation appears dependent on differential expression of the signaling intermediary EAT-2 which is present in NK cells but absent in primary, human MM cells. Taken together, these data suggest elotuzumab may enhance NK cell function directly and confer anti-MM efficacy by means beyond ADCC alone.

CRACC-CRACC interaction between Kupffer and NK cells contributes to poly I:C/D-GalN induced hepatitis

CD2-like receptor activating cytotoxic cells (CRACC) is known as a critical activating receptor of natural killer (NK) cells. We have previously reported that NK cells contribute to Poly I:C/D-galactosamine (D-GalN)-induced fulminant hepatitis. Since natural killer group 2, member D (NKG2D) is considered critical but not the only activating receptor for NK cells, we investigated the role of CRACC in this model. We found that CRACC was abundant on hepatic NK cells but with low expression levels on Kupffer cells under normal conditions. Expression of CRACC on NK cells and Kupffer cells was remarkably upregulated after poly I:C injection. Hepatic CRACC mRNA levels were also upregulated in Poly I:C/D-GalN-treated mice, and correlated positively with the serum alanine aminotransferase (ALT) levels. CRACC expression on Kupffer cells was specifically silenced by nano-particle encapsulated siRNA in vivo, which significantly reduced Poly I:C/D-GalN-induced liver injury. In co-culture experiments, it was further verified that silencing CRACC expression or blockade of CRACC activation by mAb reduced the production of interferon (IFN)-γ and tumor necrosis factor (TNF)-α. Collectively, our findings suggest that CRACC-CRACC interaction between NK cells and resident Kupffer cells contributes to Poly I:C/D-GalN-induced fulminant hepatitis.

Robust evidence for five new Graves' disease risk loci from a staged genome-wide association analysis

Graves' disease (GD), characterized by autoantibodies targeting antigens specifically expressed in thyroid tissues causing hyperthyroidism, is triggered by a combination of genetic and environmental factors. However, only a few loci for GD risk were confirmed in the various ethnic groups, and additional genetic determinants have to be detected. In this study, we carried out a three-stage study in 9529 patients with GD and 9984 controls to identify new risk loci for GD and found genome-wide significant associations in the overall populations for five novel susceptibility loci: the GPR174-ITM2A at Xq21.1, C1QTNF6-RAC2 at 22q12.3-13.1, SLAMF6 at 1q23.2, ABO at 9q34.2 and an intergenic region harboring two non-coding RNAs at 14q32.2 and one previous indefinite locus, TG at 8q24.22 (Pcombined < 5 × 10(-8)). The genotypes of corresponding variants at 14q32.2 and 8q24.22 were correlated with the expression levels of C14orf64 and a TG transcript skipping exon 46, respectively. This study increased the number of GD loci with compelling evidence and indicated that non-coding RNAs might be potentially involved in the pathogenesis of GD.

Genome-wide association study and gene expression analysis identifies CD84 as a predictor of response to etanercept therapy in rheumatoid arthritis

Anti-tumor necrosis factor alpha (anti-TNF) biologic therapy is a widely used treatment for rheumatoid arthritis (RA). It is unknown why some RA patients fail to respond adequately to anti-TNF therapy, which limits the development of clinical biomarkers to predict response or new drugs to target refractory cases. To understand the biological basis of response to anti-TNF therapy, we conducted a genome-wide association study (GWAS) meta-analysis of more than 2 million common variants in 2,706 RA patients from 13 different collections. Patients were treated with one of three anti-TNF medications: etanercept (n = 733), infliximab (n = 894), or adalimumab (n = 1,071). We identified a SNP (rs6427528) at the 1q23 locus that was associated with change in disease activity score (ΔDAS) in the etanercept subset of patients (P = 8 × 10(-8)), but not in the infliximab or adalimumab subsets (P>0.05). The SNP is predicted to disrupt transcription factor binding site motifs in the 3' UTR of an immune-related gene, CD84, and the allele associated with better response to etanercept was associated with higher CD84 gene expression in peripheral blood mononuclear cells (P = 1 × 10(-11) in 228 non-RA patients and P = 0.004 in 132 RA patients). Consistent with the genetic findings, higher CD84 gene expression correlated with lower cross-sectional DAS (P = 0.02, n = 210) and showed a non-significant trend for better ΔDAS in a subset of RA patients with gene expression data (n = 31, etanercept-treated). A small, multi-ethnic replication showed a non-significant trend towards an association among etanercept-treated RA patients of Portuguese ancestry (n = 139, P = 0.4), but no association among patients of Japanese ancestry (n = 151, P = 0.8). Our study demonstrates that an allele associated with response to etanercept therapy is also associated with CD84 gene expression, and further that CD84 expression correlates with disease activity. These findings support a model in which CD84 genotypes and/or expression may serve as a useful biomarker for response to etanercept treatment in RA patients of European ancestry.

HIV-1 Vpu affects the anterograde transport and the glycosylation pattern of NTB-A

HIV-1 Vpu induces downregulation of cell surface NTB-A to evade lysis of HIV-1 infected cells by NK cells. Here we show that Vpu affects the anterograde transport and the glycosylation pattern of NTB-A by a mechanism that is distinct from the Vpu induced downregulation of CD4 and tetherin. In the presence of Vpu, only the high mannose form of NTB-A was detectable, suggesting that Vpu prevented the formation of the mature form of NTB-A. This phenomenon is associated with the ability of Vpu to downregulate cell surface NTB-A by retention of NTB-A within the Golgi-compartment. Furthermore, the Vpu-mediated effect on NTB-A glycosylation is highly conserved among Vpu proteins derived from HIV-1 and SIV and corresponds to the level of downregulation of NTB-A. Together, these results suggest that the reduction of NTB-A from the cell surface is associated with the Vpu-mediated effect on the glycosylation pattern of newly synthesized NTB-A molecules.

The SLAM family member CD84 is regulated by ADAM10 and calpain in platelets

BACKGROUND AND OBJECTIVE

Ectodomain shedding is a major mechanism to modulate platelet receptor signaling and to downregulate platelet reactivity. Proteins of the a disintegrin and metalloproteinase (ADAM) family are implicated in the shedding of various platelet receptors. The signaling lymphocyte activation molecule (SLAM) family receptor CD84 is highly expressed in platelets and immune cells, but its role in platelet physiology is not well explored. Because of its ability to form homodimers, CD84 has been suggested to mediate contact-dependent signaling and contribute to thrombus stability. However, nothing is known about the cellular regulation of CD84.

METHODS

We studied the regulation of CD84 in murine platelets by biochemical approaches and use of three different genetically modified mouse lines. Regulation of CD84 in human platelets was studied using inhibitors and biochemical approaches.

RESULTS

We show that CD84 is cleaved from the surface of human and murine platelets in response to different shedding inducing agents and platelet receptor agonists. CD84 downregulation occurs through ectodomain-shedding and intracellular cleavage. Studies in transgenic mice identified ADAM10 as the principal sheddase responsible for CD84 cleavage, whereas ADAM17 was dispensable. Western blot analyses revealed calpain-mediated intracellular cleavage of the CD84 C-terminus, occurring simultaneously with, but independently of, ectodomain shedding. Furthermore, analysis of plasma and serum samples from transgenic mice demonstrated that CD84 is constitutively shed from the platelet surface by ADAM10 in vivo.

CONCLUSIONS

These results reveal a dual regulation mechanism for platelet CD84 by simultaneous extra- and intracellular cleavage that may modulate platelet-platelet and platelet-immune cell interactions.

TGF-β1 down-regulation of NKG2D/DAP10 and 2B4/SAP expression on human NK cells contributes to HBV persistence

The mechanism underlying persistent hepatitis B virus (HBV) infection remains unclear. We investigated the role of innate immune responses to persistent HBV infection in 154 HBV-infected patients and 95 healthy controls. The expression of NKG2D- and 2B4-activating receptors on NK cells was significantly decreased, and moreover, the expression of DAP10 and SAP, the intracellular adaptor proteins of NKG2D and 2B4 (respectively), were lower, which then impaired NK cell-mediated cytotoxic capacity and interferon-γ production. Higher concentrations of transforming growth factor-beta 1 (TGF-β1) were found in sera from persistently infected HBV patients. TGF-β1 down-regulated the expression of NKG2D and 2B4 on NK cells in our in vitro study, leading to an impairment of their effector functions. Anti-TGF-β1 antibodies could restore the expression of NKG2D and 2B4 on NK cells in vitro. Furthermore, TGF-β1 induced cell-cycle arrest in NK cells by up-regulating the expression of p15 and p21 in NK cells from immunotolerant (IT) patients. We conclude that TGF-β1 may reduce the expression of NKG2D/DAP10 and 2B4/SAP, and those IT patients who are deficient in these double-activating signals have impaired NK cell function, which is correlated with persistent HBV infection.

NK cells have been viewed as the most important effectors of the initial antiviral innate immune response. Their activation depends on the integration of signals from “co-activation” receptors, and the cytotoxic effects of NK cells on target cells are tempered by a need for combined signals from multiple activating receptors, such as NKG2D and 2B4. In this study, we showed that NKG2D and 2B4 expression levels were decreased on NK cells from patients in the IT phase of HBV infection. We further demonstrated that lower levels of intracellular adaptor proteins (DAP10 and SAP) were associated with lower surface expression of NKG2D and 2B4. As a result, the synergistically co-activated signalling pathway initiated by NKG2D and 2B4 did not operate properly in IT-phase patients. We demonstrated that high levels of soluble TGF-β1 were associated with the reduction of NKG2D and 2B4 in patients. In addition, we showed that TGF-β1 causes the cell-cycle arrest of NK cells by up-regulating the levels of p15 and p21 in NK cells from IT patients. Collectively, these findings may contribute to our understanding of the immune tolerance mechanism and aid in the development of novel therapeutic methods to clear HBV infection during the initial phase.

Increased expression of SLAM receptors SLAMF3 and SLAMF6 in systemic lupus erythematosus T lymphocytes promotes Th17 differentiation

Altered T cell function in systemic lupus erythematosus (SLE) is determined by various molecular and cellular abnormalities, including increased IL-17 production. Recent evidence suggests a crucial role for signaling lymphocyte activation molecules (SLAMs) in the expression of autoimmunity. In this study, we demonstrate that SLAMF3 and SLAMF6 expression is increased on the surface of SLE T cells compared with normal cells. SLAM coengagement with CD3 under Th17 polarizing conditions results in increased IL-17 production. SLAMF3 and SLAMF6 T cell surface expression and IL-17 levels significantly correlate with disease activity in SLE patients. Both naive and memory CD4(+) T cells produce more IL-17 in response to SLAM costimulation as compared with CD28 costimulation. In naive CD4(+) cells, IL-17 production after CD28 costimulation peaks on day 3, whereas costimulation with anti-SLAMF3 and anti-SLAMF6 Abs results in a prolonged and yet increasing production during 6 d. Unlike costimulation with anti-CD28, SLAM costimulation requires the presence of the adaptor molecule SLAM-associated protein. Thus, engagement of SLAMF3 and SLAMF6 along with Ag-mediated CD3/TCR stimulation represents an important source of IL-17 production, and disruption of this interaction with decoy receptors or blocking Abs should mitigate disease expression in SLE and other autoimmune conditions.

[Some considerations of immune metabolism at preeclampsia]

The goal of the work is to determine several aspects of abnormalities and a part of immune metabolism in preeclampsia. In peripheral blood serum of all pregnant women at 20th week of gestation relative content of T-lymphocyte subpopulations, active T-lymphocytes and natural killers (NK) were detected by the method of indirect immunofluorescence and in cyto-toxic test using monoclonal antibodies to CD4 and CD84, CD 16 (T-cell markers of HLA-DR antigen of second class of MHC (marker of active T-lymphocytes, "ICN Pharmaceutical", USA). According study results it can be concluded that at preeclampsia a content of NK cells in peripheral blood of pregnant women increases in the end of the second and early in the third trimesters on the background of significant decrease of general CD4 lymphocyte subpopulation. Received data allow to suppose that activation of natural killer cells (NK-cells) may be caused by the activation of cytotoxic Th-1 cells and their cytokines.

Molecular pathogenesis of EBV susceptibility in XLP as revealed by analysis of female carriers with heterozygous expression of SAP

X-linked lymphoproliferative disease (XLP) is a primary immunodeficiency caused by mutations in SH2D1A which encodes SAP. SAP functions in signalling pathways elicited by the SLAM family of leukocyte receptors. A defining feature of XLP is exquisite sensitivity to infection with EBV, a B-lymphotropic virus, but not other viruses. Although previous studies have identified defects in lymphocytes from XLP patients, the unique role of SAP in controlling EBV infection remains unresolved. We describe a novel approach to this question using female XLP carriers who, due to random X-inactivation, contain both SAP(+) and SAP(-) cells. This represents the human equivalent of a mixed bone marrow chimera in mice. While memory CD8(+) T cells specific for CMV and influenza were distributed across SAP(+) and SAP(-) populations, EBV-specific cells were exclusively SAP(+). The preferential recruitment of SAP(+) cells by EBV reflected the tropism of EBV for B cells, and the requirement for SAP expression in CD8(+) T cells for them to respond to Ag-presentation by B cells, but not other cell types. The inability of SAP(-) clones to respond to Ag-presenting B cells was overcome by blocking the SLAM receptors NTB-A and 2B4, while ectopic expression of NTB-A on fibroblasts inhibited cytotoxicity of SAP(-) CD8(+) T cells, thereby demonstrating that SLAM receptors acquire inhibitory function in the absence of SAP. The innovative XLP carrier model allowed us to unravel the mechanisms underlying the unique susceptibility of XLP patients to EBV infection in the absence of a relevant animal model. We found that this reflected the nature of the Ag-presenting cell, rather than EBV itself. Our data also identified a pathological signalling pathway that could be targeted to treat patients with severe EBV infection. This system may allow the study of other human diseases where heterozygous gene expression from random X-chromosome inactivation can be exploited.

SLAM family predicting the initiation potential of human acute lymphoblastic leukemia in NOD/SCID mice

BACKGROUND

The SLAM family recently has been reported to show an important biological role in lymphocyte development and immunological function, and it is efficient to highly purify hematopoietic stem cells using a simple combination of SLAM family members. To elucidate the presence of this family on acute lymphoblastic leukemia (ALL), as well as its relationship with the leukemia-initiating potential, we analyzed the expression pattern of this family members on human ALL progenitor cells, combined with serial xenotransplantation assay.

METHODS

Expression analysis was carried out by flow cytometry. We combined the expression pattern of human CD(150), CD(244) and CD(48) with serial xenotransplantation of B-ALL progenitor cells to indicate their relationship.

RESULTS

CD(48) and CD(244) were expressed on most B-ALL progenitor cells, the percentage being (93.08 ± 6.46)% and (63.37 ± 29.31)%, respectively. Interestingly, the proportion of CD(150)(+) cells declined obviously in engrafted cases ((24.94 ± 7.32)%) compared with non-engrafted cases ((77.54 ± 5.93)%, P < 0.01), which indicated that only blast cells with low percentage of CD(150)(+) population were able to reconstitute leukemia into primary, secondary and tertiary NOD/SCID mice.

CONCLUSIONS

SLAM family members are present on B-ALL progenitor cells and the leukemia-initiating potential of leukemic blasts is correlated negatively with the proportion of CD(150)(+) cells, the percentage of which can serve as a useful predictor for engraftment success of B-ALL to immune deficient mice.

Dual function of the NK cell receptor 2B4 (CD244) in the regulation of HCV-specific CD8+ T cells

The outcome of viral infections is dependent on the function of CD8+ T cells which are tightly regulated by costimulatory molecules. The NK cell receptor 2B4 (CD244) is a transmembrane protein belonging to the Ig superfamily which can also be expressed by CD8+ T cells. The aim of this study was to analyze the role of 2B4 as an additional costimulatory receptor regulating CD8+ T cell function and in particular to investigate its implication for exhaustion of hepatitis C virus (HCV)-specific CD8+ T cells during persistent infection. We demonstrate that (i) 2B4 is expressed on virus-specific CD8+ T cells during acute and chronic hepatitis C, (ii) that 2B4 cross-linking can lead to both inhibition and activation of HCV-specific CD8+ T cell function, depending on expression levels of 2B4 and the intracellular adaptor molecule SAP and (iii) that 2B4 stimulation may counteract enhanced proliferation of HCV-specific CD8+ T cells induced by PD1 blockade. We suggest that 2B4 is another important molecule within the network of costimulatory/inhibitory receptors regulating CD8+ T cell function in acute and chronic hepatitis C and that 2B4 expression levels could also be a marker of CD8+ T cell dysfunction. Understanding in more detail how 2B4 exerts its differential effects could have implications for the development of novel immunotherapies of HCV infection aiming to achieve immune control.

Infection with the hepatitis C Virus (HCV) is a world-wide health burden, the infection becomes persistent in the majority of cases. In chronic patients HCV-specific immune responses are weak, HCV-specific CD8+ T cells were shown to be functionally exhausted and to be negatively controlled by costimulatory molecules like PD-1. Here, we show that the costimulatory molecule 2B4 (CD244) is also involved in the regulation of HCV-specific CD8+ T cell responses and that 2B4 expression is selectively upregulated on virus-specific CD8+ T cells in persistent infections. Proliferation of HCV-specific CD8+ T cells from chronic patients increased by 2B4 cross-linking only if the ex vivo 2B4 expression was low, while we could observe no effect on samples with high 2B4 expression levels. Of note, expression of the intracellular 2B4 adaptor molecule SAP, which leads to an activation of the cell, decreased with higher 2B4 expression levels. Finally, we were able to show that 2B4 cross-linking can counter-act enhanced proliferation of HCV-specific CD8+ T cells seen upon PD-1 blockade. Thus, our study provides new insights into the regulation of CD8+ T cell responses demonstrating an implication of the costimulatory molecule 2B4.

The Ras/MAPK pathway is required for generation of iNKT cells

iNKT cells derive from CD4(+)CD8(+) DP thymocytes, and are selected by thymocyte-thymocyte interactions through signals from their invariant Vα14-Jα18 TCR and from the costimulatory molecules SLAMF1 and SLAMF6. Genetic studies have demonstrated the contribution of different signaling pathways to this process. Surprisingly, current models imply that the Ras/MAPK pathway, one of the critical mediators of conventional αβ T cell positive selection, is not necessary for iNKT cell development. Using mice defective at different levels of this pathway our results refute this paradigm, and demonstrate that Ras, and its downstream effectors Egr-1 and Egr-2 are required for positive selection of iNKT cells. Interestingly our results also show that there are differences in the contributions of several of these molecules to the development of iNKT and conventional αβ T cells.

Association study of 3 rheumatoid arthritis risk loci in systemic sclerosis in European Caucasian population

INTRODUCTION

Accumulating evidences show that shared autoimmunity is critical for the pathogenesis of many inflammatory rheumatic conditions. Specific phenotype could arise from specific genes, and/or combination of genetic factors and environment. Systemic sclerosis (SSc) belongs to connective tissue disorders and recent data have highlighted strong associations with some autoimmunity genes shared with other autoimmune diseases.

OBJECTIVES

To determine whether novel risk loci associated with rheumatoid arthritis (RA) may confer susceptibility to SSc. Single nucleotide polymorphism from CCL21, CD244 and CDK6 were tested for association.

METHODS

SNPs harbouring association with RA, CCL21-rs2812378, CDK6-rs42041 and CD244-rs6682654 were genotyped in a cohort of 1031 SSc patients and 1014 controls. All individuals were of European Caucasian origin.

RESULTS

The three polymorphisms were in Hardy-Weinberg equilibrium in the control population and allelic frequencies were similar to those expected in European populations. Allelic and genotypic frequencies for these three polymorphisms were found to be similar in SSc patients and controls. Moreover, sub-phenotype analyses in particular for subgroups having diffuse subcutaneous subtype, specific auto-antibodies or fibrosing alveolitis did not detect any difference between SSc patients and controls.

CONCLUSIONS

These results obtained through a large cohort of European Caucasian SSc patients do not support the implication of CCL21, CD244 and CDK6 genes in the pathogenesis of SSc although these genes were recently identified as RA susceptibility genes.

Physical interactions between mast cells and eosinophils: a novel mechanism enhancing eosinophil survival in vitro

BACKGROUND

Mast cells (MCs) and eosinophils (Eos) are the key effector cells of the allergic reaction. Although classically associated with different stages of the response, the cells co-exist in the inflamed tissue in the late and chronic phases in high numbers and are likely to cross-talk. While some mediators of MCs are known to affect Eos biology and vice versa, paracrine and physical interplay between the two cells has not been described yet. We aimed to investigate whether intercellular MC-Eos communication could take place in the allergic response and exert functional bidirectional changes on the cells.

METHODS

Tissue sections from various allergic disorders were specifically stained for both cells. Human cord blood-derived MCs and peripheral blood Eos, co-cultured under different conditions, were studied by advanced microscopy and flow cytometry.

RESULTS

Several co-localized MC-Eos pairs were detected in human nasal polyps and asthmatic bronchi, as well in mouse atopic dermatitis. In vitro, MCs and Eos formed stable conjugates at high rates, with clear membrane contact. In the presence of MCs, Eos were significantly more viable under several co-culture conditions and at both IgE-activated and steroid-inhibited settings. MC regulation of Eos survival required communication through soluble mediators but was even more dependent on physical cell-cell contact.

CONCLUSIONS

Our findings provide the first evidence for a complex network of paracrine and membrane interactions between MCs and Eos. The prosurvival phenotype induced by this MC-Eos interplay may be critical for sustaining chronic allergic inflammation.

Strain-specific copy number variation in the intelectin locus on the 129 mouse chromosome 1

BACKGROUND

C57BL/6J mice possess a single intelectin (Itln) gene on chromosome 1. The function of intelectins is not well understood, but roles have been postulated in insulin sensitivity, bacterial recognition, intestinal lactoferrin uptake and response to parasites and allergens. In contrast to C57BL/6J mice, there is evidence for expansion of the Itln locus in other strains and at least one additional mouse Itln gene product has been described. The aim of this study was to sequence and characterise the Itln locus in the 129S7 strain, to determine the nature of the chromosomal expansion and to inform possible future gene deletion strategies.

RESULTS

Six 129S7 BAC clones were sequenced and assembled to generate 600 kbp of chromosomal sequence, including the entire Itln locus of approximately 500 kbp. The locus contained six distinct Itln genes, two CD244 genes and several Itln- and CD244-related pseudogenes. It was approximately 433 kbp larger than the corresponding C57BL/6J locus. The expansion of the Itln locus appears to have occurred through multiple duplications of a segment consisting of a full-length Itln gene, a CD244 (pseudo)gene and an Itln pseudogene fragment. Strong evidence for tissue-specific distribution of Itln variants was found, indicating that Itln duplication contributes more than a simple gene dosage effect.

CONCLUSIONS

We have characterised the Itln locus in 129S7 mice to reveal six Itln genes with distinct sequence and expression characteristics. Since C57BL/6J mice possess only a single Itln gene, this is likely to contribute to functional differences between C57BL/6J and other mouse strains.

Coexpression of PD-1, 2B4, CD160 and KLRG1 on exhausted HCV-specific CD8+ T cells is linked to antigen recognition and T cell differentiation

Exhausted CD8+ T cell responses during chronic viral infections are defined by a complex expression pattern of inhibitory receptors. However, very little information is currently available about the coexpression patterns of these receptors on human virus-specific CD8+ T cells and their correlation with antiviral functions, T cell differentiation and antigen recognition. We addressed these important aspects in a cohort of 38 chronically HCV infected patients and found a coexpression of inhibitory receptors such as 2B4, CD160 and KLRG1 in association with PD-1 in about half of the HCV-specific CD8+ T cell responses. Importantly, this exhaustive phenotype was associated with low and intermediate levels of CD127 expression, an impaired proliferative capacity, an intermediate T cell differentiation stage and absence of sequence variations within the corresponding epitopes, indicating ongoing antigen triggering. In contrast, a low expression of inhibitory receptors by the remaining HCV-specific CD8+ T cells occurred in concert with a CD127hi phenotype, an early T cell differentiation stage and presence of viral sequence variations within the corresponding epitopes. In sum, these results suggest that T cell exhaustion contributes to the failure of about half of HCV-specific CD8+ T cell responses and that it is determined by a complex interplay of immunological (e.g. T cell differentiation) and virological (e.g. ongoing antigen triggering) factors.

About 170 million people are infected with hepatitis C virus (HCV), which may cause severe liver disease and liver cancer. Upon acute infection, only about 30% of patients are able to eliminate the virus spontaneously while about 70% of patients develop chronic infection. It is known that a successful immune response against HCV depends on virus-specific CD8+ T cells. However, during chronic infection, these cells are impaired in their antiviral function. In this study, we found that the exhaustion is characterized by the expression of multiple inhibitory receptors, such as PD-1, 2B4, CD160 and KLRG1. Of note, the coexpression of these receptors depends on the ongoing recognition of the viral antigen and the maturation stage of the T cell. The remaining virus-specific T cell responses that are not exhausted do not recognize the virus present in the patients any more due to viral mutations, indicating viral escape. Thus, they fail to exert antiviral activity, although they share characteristics of fully functional memory T cells. In sum, we have found that T cell exhaustion contributes to the failure of about half of HCV-specific CD8+ T cell responses and that it is determined by a complex interplay of immunological and virological factors. These findings will be important to consider in the design of new antiviral vaccination strategies.

Synergistic signals for natural cytotoxicity are required to overcome inhibition by c-Cbl ubiquitin ligase

Natural killer (NK) cell cytotoxicity toward target cells depends on synergistic coactivation by NK cell receptors such as NKG2D and 2B4. How synergy occurs is not known. Synergistic phosphorylation of phospholipase PLC-gamma2, Ca(2+) mobilization, and degranulation triggered by NKG2D and 2B4 coengagement were blocked by Vav1 siRNA knockdown, but enhanced by knockdown of c-Cbl. c-Cbl inhibited Vav1-dependent signals, given that c-Cbl knockdown did not rescue the Vav1 defect. Moreover, c-Cbl knockdown and Vav1 overexpression each circumvented the necessity for synergy because NKG2D or 2B4 alone became sufficient for activation. Thus, synergy requires not strict complementation but, rather, strong Vav1 signals to overcome inhibition by c-Cbl. Inhibition of NK cell cytotoxicity by CD94-NKG2A binding to HLA-E on target cells was dominant over synergistic activation, even after c-Cbl knockdown. Therefore, NK cell activation by synergizing receptors is regulated at the level of Vav1 by a hierarchy of inhibitory mechanisms.

High expression of CD244 and SAP regulated CD8 T cell responses of patients with HTLV-I associated neurologic disease

HTLV-I-specific CD8⁺ T cells have been characterized with high frequencies in peripheral blood and cerebrospinal fluid and production of proinflammatory cytokines, which contribute to central nervous system inflammation in HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP). However, little is known about the differences in CD8⁺ T cell activation status between asymptomatic carrier (ACs) and patients with HAM/TSP. The expression of CD244, a signaling lymphocyte activation molecule (SLAM) family receptor, was significantly higher on CD8⁺ T cells in HTLV-I-infected patients, both ACs and patients with HAM/TSP, than those on healthy normal donors (NDs). Blockade of CD244 inhibited degranulation and IFN-γ production in CD8⁺ T cells of patients with HAM/TSP, suggesting that CD244 is associated with effector functions of CD8⁺ T cells in patients with HAM/TSP. Moreover, SLAM-associated protein (SAP) was overexpressed in patients with HAM/TSP compared to ACs and NDs. SAP expression in Tax-specific CTLs was correlated in the HTLV-I proviral DNA loads and the frequency of the cells in HTLV-I-infected patients. SAP knockdown by siRNA also inhibited IFN-γ production in CD8⁺ T cells of patients with HAM/TSP. Thus, the CD244/SAP pathway was involved in the active regulation of CD8⁺ T cells of patients with HAM/TSP, and may play roles in promoting inflammatory neurological disease.

Human T-lymphotropic virus type I (HTLV-I) is a retrovirus that persistently infects 20 million people worldwide. The majority of infected individuals are asymptomatic carriers of the virus, but 5–10% of infected people develop either adult T cell leukemia/lymphoma (ATL) or a chronic, progressive neurological disease termed HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HAM/TSP is characterized by central nervous system (CNS) inflammation including HTLV-I-specific CD8⁺ T cells where disease progression and pathogenesis is associated with a dysregulation of antigen-specific CD8⁺ T cells, although the mechanism of this dysregulation remains to be defined. Here we demonstrate that a signaling lymphocyte activation molecule (SLAM) family of receptors, CD244, was overexpressed on CD8⁺ T cells of HTLV-I-infected patients than those of healthy normal donors, and that the upregulation of the adaptor protein, SAP, in CD8⁺ T cells distinguished HTLV-I infected individuals with and without neurologic disease. Both CD244 and SAP were associated with effector functions (high expression of IFN-γ) of CD8⁺ T cells in patients with HAM/TSP. This finding has important implication for T cell-mediated pathogenesis in human chronic viral infection associated with imbalance of immune function.

2B4 (CD244) signaling via chimeric receptors costimulates tumor-antigen specific proliferation and in vitro expansion of human T cells

Regulatory NK cell receptors can contribute to antigen-specific adaptive immune responses by modulating T cell receptor (TCR)-induced T cell activation. We investigated the potential of the NK cell receptor 2B4 (CD244) to enhance tumor antigen-induced activation of human T cells. 2B4 is a member of the CD2 receptor subfamily with both activating and inhibitory functions in NK cells. In T cells, its expression is positively associated with the acquisition of a cytolytic effector memory phenotype. Recombinant chimeric receptors that link extracellular single-chain Fv fragments specific for the tumor-associated surface antigens CD19 and G(D2) to the signaling domains of human 2B4 and/or TCRzeta were expressed in non-specifically activated peripheral blood T cells by retroviral gene transfer. While 2B4 signaling alone failed to induce T cell effector functions or proliferation, it significantly augmented the antigen-specific activation responses induced by TCRzeta. 2B4 costimulation did not affect the predominant effector memory phenotype of expanding T cells, nor did it increase the proportion of T cells with regulatory phenotype (CD4+CD25(hi)FoxP3+). These data support a costimulatory role for 2B4 in human T cell subpopulations. As an amplifier of TCR-mediated signals, 2B4 may provide a powerful new tool for immunotherapy of cancer, promoting sustained activation and proliferation of gene-modified antitumor T cells.

Inhibition and activation by CD244 depends on CD2 and phospholipase C-gamma1

Regulation by the NK and T cell surface receptor CD244 in mice and humans depends both on engagement at the cell surface by CD48 and intracellular interactions with SAP and EAT-2. Relevance to human disease by manipulating CD244 in mouse models is complicated by rodent CD2 also binding CD48. We distinguish between contributions of mouse CD244 and CD2 on engagement of CD48 in a mouse T cell hybridoma. CD2 and CD244 both contribute positively to the immune response as mutation of proline-rich motifs or tyrosine motifs in the tails of CD2 and CD244, respectively, result in a decrease in antigen-specific interleukin-2 production. Inhibitory effects of mouse CD244 are accounted for by competition with CD2 at the cell surface for CD48. In humans CD2 and CD244 are engaged separately at the cell surface but biochemical data suggest a potential conserved intracellular link between the two receptors through FYN kinase. We identify a novel signaling mechanism for CD244 through its potential to recruit phospholipase C-gamma1 via the conserved phosphorylated tyrosine motif in the tail of the adaptor protein EAT-2, which we show is important for function.

2B4 (CD244) signaling by recombinant antigen-specific chimeric receptors costimulates natural killer cell activation to leukemia and neuroblastoma cells

PURPOSE

Novel natural killer (NK) cell-directed strategies in cancer immunotherapy aim at specifically modulating the balance between NK cell receptor signals toward tumor-specific activation. The signaling lymphocyte activation molecule-related receptor 2B4 (CD244) is an important regulator of NK cell activation. We investigated whether 2B4-enhanced activation signals can redirect the cytolytic function of human NK cells to NK cell-resistant and autologous leukemia and tumor targets.

EXPERIMENTAL DESIGN

In vitro-stimulated NK cells from healthy donors and pediatric leukemia patients were gene modified with CD19 or G(D2)-specific chimeric receptors containing either the T-cell receptor zeta or 2B4 endodomain alone or combined.

RESULTS

Chimeric 2B4 signaling alone failed to induce interleukin-2 receptor up-regulation and cytokine secretion but triggered a specific degranulation response. Integration of the 2B4 endodomain into T-cell receptor zeta chimeric receptors significantly enhanced all aspects of the NK cell activation response to antigen-expressing leukemia or neuroblastoma cells, including CD25 up-regulation, secretion of IFN-gamma and tumor necrosis factor-alpha, release of cytolytic granules, and growth inhibition, and overcame NK cell resistance of autologous leukemia cells while maintaining antigen specificity.

CONCLUSION

These data indicate that the 2B4 receptor has a potent costimulatory effect in NK cells. Antigen-specific 2B4zeta-expressing NK cells may be a powerful new tool for adoptive immunotherapy of leukemia and other malignancies.

Integrin-dependent organization and bidirectional vesicular traffic at cytotoxic immune synapses

Cytotoxic lymphocytes kill target cells by releasing the content of secretory lysosomes at the immune synapse. To understand the dynamics and control of cytotoxic immune synapses, we imaged human primary, live natural killer cells on lipid bilayers carrying ligands of activation receptors. Formation of an organized synapse was dependent on the presence of the beta2 integrin ligand ICAM-1. Ligands of coactivation receptors 2B4 and NKG2D segregated into central and peripheral regions, respectively. Lysosomal protein LAMP-1 that was exocytosed during degranulation accumulated in a large and spatially stable cluster, which overlapped with a site of membrane internalization. Lysosomal compartments reached the plasma membrane at focal points adjacent to centrally accumulated LAMP-1. Imaging of fixed cells revealed that perforin-containing granules were juxtaposed to an intracellular compartment where exocytosed LAMP-1 was retrieved. Thus, cytotoxic immune synapses include a central region of bidirectional vesicular traffic, which is controlled by integrin signaling.