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The localization of memory T cells to human skin is essential for long-term immune surveillance and the maintenance of barrier integrity. The expression of CCR8 during naive T cell activation is controlled by skin-specific factors derived from epidermal keratinocytes and not by resident dendritic cells. In this study,we show that the CCR8-inducing factors are heat stable and protease resistant and include the vitamin D3 metabolite 1α,25-dihydroxyvitamin D3 and PGE2. The effect of either metabolite alone on CCR8 expression was weak,whereas their combination resulted in robust CCR8 expression. Elevation of intracellular cAMP was essential because PGE2 could be substituted with the adenylyl cyclase agonist forskolin,and CCR8 expression was sensitive to protein kinase A inhibition. For effective induction,exposure of naive T cells to these epidermal factors needed to occur either prior to or during T cell activation even though CCR8 was only detected 4-5 d later in proliferating T cells. The importance of tissue environments in maintaining cellular immune surveillance networks within distinct healthy tissues provides a paradigm shift in adaptive immunity. Epidermal-derived vitamin D3 metabolites and PGs provide an essential cue for the localization of CCR8(+) immune surveillance T cells within healthy human skin. View Publication

Daratumumab is an anti-CD38 monoclonal antibody with lytic activity against multiple myeloma (MM) cells,including ADCC (antibody-dependent cellular cytotoxicity) and CDC (complement-dependent cytotoxicity). Owing to a marked heterogeneity of response to daratumumab therapy in MM,we investigated determinants of the sensitivity of MM cells toward daratumumab-mediated ADCC and CDC. In bone marrow samples from 144 MM patients,we observed no difference in daratumumab-mediated lysis between newly diagnosed or relapsed/refractory patients. However,we discovered,next to an expected effect of effector (natural killer cells/monocytes) to target (MM cells) ratio on ADCC,a significant association between CD38 expression and daratumumab-mediated ADCC (127 patients),as well as CDC (56 patients). Similarly,experiments with isogenic MM cell lines expressing different levels of CD38 revealed that the level of CD38 expression is an important determinant of daratumumab-mediated ADCC and CDC. Importantly,all-trans retinoic acid (ATRA) increased CD38 expression levels but also reduced expression of the complement-inhibitory proteins CD55 and CD59 in both cell lines and primary MM samples. This resulted in a significant enhancement of the activity of daratumumab in vitro and in a humanized MM mouse model as well. Our results provide the preclinical rationale for further evaluation of daratumumab combined with ATRA in MM patients. View Publication

Host defense peptides have recently gained much interest as novel anti-infectives owing to their ability to kill bacteria and simultaneously modulate host cell responses. The cationic host defense peptide GKY25 (GKYGFYTHVFRLKKWIQKVIDQFGE),derived from the C terminus of human thrombin,inhibits proinflammatory responses in vitro and in vivo,but the mode of action is unclear. In this study,we show that GKY25,apart from binding bacterial LPS,also interacts directly with monocytes and macrophages in vitro,ex vivo,and in vivo. Moreover,GKY25 inhibits TLR4- and TLR2-induced NF-κB activation in response to several microbe-derived agonists. Furthermore,GKY25 reduces LPS-induced phosphorylation of MAPKs p38α and JNK1/2/3. FACS and electron microscopy analyses showed that GKY25 interferes with TLR4/myeloid differentiation protein-2 dimerization. The results demonstrate a previously undisclosed activity of the host defense peptide GKY25,based on combined LPS and cell interactions leading to inhibition of TLR4 dimerization and subsequent reduction of NF-κB activity and proinflammatory cytokine production in monocytes and macrophages. View Publication

BACKGROUND Acute myeloid leukemia (AML) is initiated and maintained by a subset of self-renewing leukemia stem cells (LSCs),which contribute to the progression,recurrence and therapeutic resistance of leukemia. However,the mechanisms underlying the maintenance of LSCs drug resistance have not been fully defined. In this study,we attempted to elucidate the mechanisms of LSCs drug resistance. METHODS We performed reverse phase protein arrays to analyze the expression of anti-apoptotic proteins in the LSC-enriched leukemia cell line KG-1a. Immuno-blotting,cell viability and clinical AML samples were evaluated to verify the micro-assay results. The characteristics and transcriptional regulation of survivin were analyzed with the relative luciferase reporter assay,mutant constructs,chromatin immuno-precipitation (ChIP),quantitative real-time reverse transcription polymerase chain reaction (RT-qPCR),and western blotting. The levels of Sp1,c-Myc,phospho-extracellular signal-regulated kinase (p-ERK),phospho-mitogen and stress-activated protein kinase (p-MSK) were investigated in paired CD34+ and CD34- AML patient samples. RESULTS Survivin was highly over-expressed in CD34 + CD38- KG-1a cells and paired CD34+ AML patients compared with their differentiated counterparts. Functionally,survivin contributes to the drug resistance of LSCs,and Sp1 and c-Myc concurrently regulate levels of survivin transcription. Clinically,Sp1 and c-Myc were significantly up-regulated and positively correlated with survivin in CD34+ AML patients. Moreover,Sp1 and c-Myc were further activated by the ERK/MSK mitogen-activated protein kinase (MAPK) signaling pathway,modulating survivin levels. CONCLUSION Our findings demonstrated that ERK/MSK/Sp1/c-Myc axis functioned as a critical regulator of survivin expression in LSCs,offering a potential new therapeutic strategy for LSCs therapy. View Publication

BACKGROUND This article is part of a series of publications providing formal method validation for biospecimen processing in the context of accreditation in laboratories and biobanks. We report the optimization and validation for fitness-for-purpose of automated and manual protocols for isolating peripheral blood mononuclear cells (PBMCs) from whole blood,and compare the two methods. METHODS The manual method was optimized for whole blood centrifugation speed,gradient type (Ficoll,Leucosep,CPT),and freezing method (Mr Frosty,Controlled Rate Freezing). Various parameters of the automated protocol using a CPT gradient on a Tecan liquid handler were optimized. Optimal protocols were validated in parallel for reproducibility and robustness. Optimization and validation were assessed in terms of cell yield,viability,recovery,white blood cell (WBC) subpopulation distribution,gene expression,and lymphoblastoid cell line (LCL) transformation. RESULTS An initial centrifugation of whole blood at 2000 g was considered optimal for further processing,allowing isolation of plasma and PBMCs from a single sample. The three gradients gave similar outcomes in terms of cell yield,viability,and WBC subpopulation distribution. Ficoll showed some advantages and was selected for further evaluations. Optimization of the automated protocol script using a CPT gradient gave 61% cell recovery. No significant differences in quality,quantity,and WBC subpopulation distribution were seen between the two freezing methods,and Mr. Frosty was selected. The manual and automated protocols were reproducible in terms of quantity,recovery,viability,WBC subpopulation distribution,gene expression,and LCL transformation. Most (75%-100%) of the 13 robustness parameters were accepted for both methods with an 8 h pre-centrifugation delay versus 38%-85% after 24 h. Differences identified between the automated and manual methods were not considered consequential. CONCLUSIONS We validated the first fully automated method for isolating viable PBMCs,including RNA analysis and generation of LCLs. We recommend processing within 8 h of blood collection. View Publication

The paracaspase MALT1 plays an important role in immune receptor-driven signaling pathways leading to NF-κB activation. MALT1 promotes signaling by acting as a scaffold,recruiting downstream signaling proteins,as well as by proteolytic cleavage of multiple substrates. However,the relative contributions of these two different activities to T and B cell function are not well understood. To investigate how MALT1 proteolytic activity contributes to overall immune cell regulation,we generated MALT1 protease-deficient mice (Malt1(PD/PD)) and compared their phenotype with that of MALT1 knockout animals (Malt1(-/-)). Malt1(PD/PD) mice displayed defects in multiple cell types including marginal zone B cells,B1 B cells,IL-10-producing B cells,regulatory T cells,and mature T and B cells. In general,immune defects were more pronounced in Malt1(-/-) animals. Both mouse lines showed abrogated B cell responses upon immunization with T-dependent and T-independent Ags. In vitro,inactivation of MALT1 protease activity caused reduced stimulation-induced T cell proliferation,impaired IL-2 and TNF-α production,as well as defective Th17 differentiation. Consequently,Malt1(PD/PD) mice were protected in a Th17-dependent experimental autoimmune encephalomyelitis model. Surprisingly,Malt1(PD/PD) animals developed a multiorgan inflammatory pathology,characterized by Th1 and Th2/0 responses and enhanced IgG1 and IgE levels,which was delayed by wild-type regulatory T cell reconstitution. We therefore propose that the pathology characterizing Malt1(PD/PD) animals arises from an immune imbalance featuring pathogenic Th1- and Th2/0-skewed effector responses and reduced immunosuppressive compartments. These data uncover a previously unappreciated key function of MALT1 protease activity in immune homeostasis and underline its relevance in human health and disease. View Publication

Class switch DNA recombination (CSR) is central to the maturation of the Ab response because it diversifies Ab effector functions. Like somatic hypermutation,CSR requires activation-induced cytidine deaminase (AID),whose expression is restricted to B cells,as induced by CD40 engagement or dual TLR-BCR engagement (primary CSR-inducing stimuli). By constructing conditional knockout Igh(+/C)γ(1-cre)Rab7(fl/fl) mice,we identified a B cell-intrinsic role for Rab7,a small GTPase involved in intracellular membrane functions,in mediating AID induction and CSR. Igh(+/C)γ(1-cre)Rab7(fl/fl) mice displayed normal B and T cell development and were deficient in Rab7 only in B cells undergoing Igh(C)γ(1-cre) Iγ1-Sγ1-Cγ1-cre transcription,as induced--like Igh germline Iγ1-Sγ1-Cγ1 and Iε-Sε-Cε transcription--by IL-4 in conjunction with a primary CSR-inducing stimulus. These mice could not mount T-independent or T-dependent class-switched IgG1 or IgE responses while maintaining normal IgM levels. Igh(+/C)γ(1-cre)Rab7(fl/fl) B cells showed,in vivo and in vitro,normal proliferation and survival,normal Blimp-1 expression and plasma cell differentiation,as well as intact activation of the noncanonical NF-κB,p38 kinase,and ERK1/2 kinase pathways. They,however,were defective in AID expression and CSR in vivo and in vitro,as induced by CD40 engagement or dual TLR1/2-,TLR4-,TLR7-,or TLR9-BCR engagement. In Igh(+/C)γ(1-cre)Rab7(fl/fl) B cells,CSR was rescued by enforced AID expression. These findings,together with our demonstration that Rab7-mediated canonical NF-κB activation,as critical to AID induction,outline a novel role of Rab7 in signaling pathways that lead to AID expression and CSR,likely by promoting assembly of signaling complexes along intracellular membranes. View Publication

Naïve T cells require B7/CD28 costimulation in order to be fully activated. Attempts to block this pathway have been effective in preventing unwanted immune reactions. As B7 blockade might also affect Treg cells and interfere with negative signaling through membrane CTLA-4 on effector T (Teff) cells,its immune-modulatory effects are potentially more complex. Here,we used the mouse model of multiple sclerosis (MS),EAE,to study the effect of B7 blockade. An effective therapy for MS patients has to interfere with ongoing inflammation,and therefore we injected CTLA-4Ig at day 7 and 9 after immunization,when myelin-reactive T cells have been primed and start migrating toward the CNS. Surprisingly,B7 blockade exacerbated disease signs and resulted in more severe CNS inflammation and demyelination,and was associated with an enhanced production of the inflammatory cytokines IL-17 and IFN-γ. Importantly,CTLA-4Ig treatment resulted in a transient reduction of Ki67 and CTLA-4 expression and function of peripheral Treg cells. Taken together,B7 blockade at a particular stage of the autoimmune response can result in the suppression of Treg cells,leading to a more severe disease. View Publication

The mechanisms by which neutralizing antibodies inhibit Marburg virus (MARV) are not known. We isolated a panel of neutralizing antibodies from a human MARV survivor that bind to MARV glycoprotein (GP) and compete for binding to a single major antigenic site. Remarkably,several of the antibodies also bind to Ebola virus (EBOV) GP. Single-particle EM structures of antibody-GP complexes reveal that all of the neutralizing antibodies bind to MARV GP at or near the predicted region of the receptor-binding site. The presence of the glycan cap or mucin-like domain blocks binding of neutralizing antibodies to EBOV GP,but not to MARV GP. The data suggest that MARV-neutralizing antibodies inhibit virus by binding to infectious virions at the exposed MARV receptor-binding site,revealing a mechanism of filovirus inhibition. View Publication

HIV-1 infection leads to numerous B cell abnormalities,including hypergammaglobulinemia,nonspecific B cell activation,nonspecific class switching,increased cell turnover,breakage of tolerance,increased immature/transitional B cells,B cell malignancies,as well as a loss of capacity to generate and maintain memory,all of which contribute to a global impairment of the immune humoral compartment. Several cytokines and soluble factors,which are increased in sera of HIV-1-infected individuals,have been suggested to directly or indirectly contribute to these B cell dysfunctions,and one of these is the B cell-activating factor (BAFF). We report in this study that HIV-1 (X4- and R5-tropic) upregulates BAFF expression and secretion by human monocytes. Moreover,we show that the virus-mediated production of BAFF by monocytes relies on a type I IFN response by a small percentage of plasmacytoid dendritic cells (pDCs) present in the monocyte cultures. HIV-1-induced type I IFN by pDCs triggers BAFF production in both classical and intermediate monocytes,but not in nonclassical monocytes,which nonetheless display a very strong basal BAFF production. We report also that basal BAFF secretion was higher in monocytes obtained from females compared with those from male donors. This study provides a novel mechanistic explanation for the increased BAFF levels observed during HIV-1 infection and highlights the importance of pDC/monocyte crosstalk to drive BAFF secretion. View Publication

Manipulation of the CD28/CTLA-4 pathway is at the heart of a number of immunomodulatory approaches used in both autoimmunity and cancer. Although it is clear that CTLA-4 is a critical regulator of T cell responses,the immunological contexts in which CTLA-4 controls immune responses are not well defined. In this study,we show that whereas CD80/CD86-dependent activation of resting human T cells caused extensive T cell proliferation and robust CTLA-4 expression,in this context CTLA-4 blocking Abs had no impact on the response. In contrast,in settings where CTLA-4(+) cells were present as regulators� View Publication

Mast cells are tissue-resident immune cells that play a key role in inflammation and allergy. Here we show that interaction of mast cells with antibody-targeted cells induces the polarized exocytosis of their granules resulting in a sustained exposure of effector enzymes,such as tryptase and chymase,at the cell-cell contact site. This previously unidentified mast cell effector mechanism,which we name the antibody-dependent degranulatory synapse (ADDS),is triggered by both IgE- and IgG-targeted cells. ADDSs take place within an area of cortical actin cytoskeleton clearance in the absence of microtubule organizing centre and Golgi apparatus repositioning towards the stimulating cell. Remarkably,IgG-mediated degranulatory synapses also occur upon contact with opsonized Toxoplasma gondii tachyzoites resulting in tryptase-dependent parasite death. Our results broaden current views of mast cell degranulation by revealing that human mast cells form degranulatory synapses with antibody-targeted cells and pathogens for dedicated secretion and defence. View Publication