scholarly journals Surface-associated antigen induces permeabilization of primary mouse B-cells and lysosome exocytosis facilitating antigen uptake and presentation to T-cells

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Fernando Y Maeda ◽  
Jurriaan JH van Haaren ◽  
David B Langley ◽  
Daniel Christ ◽  
Norma W Andrews ◽  
...  
Keyword(s):  
T Cells ◽  
B Cells ◽  
B Cell ◽  
Lipid Bilayers ◽  
Cell Receptor ◽  
Cell Permeabilization ◽  
Antigen Uptake ◽  
Extracellular Release ◽  
Primary Mouse ◽  
Antigen Presenting

B-cell receptor (BCR)-mediated antigen internalization and presentation are essential for humoral memory immune responses. Antigen encountered by B-cells is often tightly associated with the surface of pathogens and/or antigen-presenting cells. Internalization of such antigens requires myosin-mediated traction forces and extracellular release of lysosomal enzymes, but the mechanism triggering lysosomal exocytosis is unknown. Here we show that BCR-mediated recognition of antigen tethered to beads, to planar lipid-bilayers or expressed on cell surfaces causes localized plasma membrane (PM) permeabilization, a process that requires BCR signaling and non-muscle myosin II activity. B-cell permeabilization triggers PM repair responses involving lysosomal exocytosis, and B-cells permeabilized by surface-associated antigen internalize more antigen than cells that remain intact. Higher affinity antigens cause more B-cell permeabilization and lysosomal exocytosis and are more efficiently presented to T-cells. Thus, PM permeabilization by surface-associated antigen triggers a lysosome-mediated B-cell resealing response, providing the extracellular hydrolases that facilitate antigen internalization and presentation.

scholarly journals Surface-bound antigen induces B-cell permeabilization and lysosome exocytosis facilitating antigen uptake and presentation to T-cells

2020 ◽  
Author(s):  
Fernando Y. Maeda ◽  
Jurriaan J. H. van Haaren ◽  
David B. Langley ◽  
Daniel Christ ◽  
Norma W. Andrews ◽  
...  
Keyword(s):  
T Cells ◽  
B Cells ◽  
B Cell ◽  
Lipid Bilayers ◽  
Cell Receptor ◽  
Cell Permeabilization ◽  
Antigen Uptake ◽  
Extracellular Release ◽  
Antigen Presenting ◽  
Muscle Myosin

AbstractB-cell receptor (BCR)-mediated antigen internalization and presentation are essential for humoral memory immune responses. Antigen encountered by B-cells is often tightly associated with the surface of pathogens and/or antigen-presenting cells. Internalization of such antigens requires myosin-mediated traction forces and extracellular release of lysosomal enzymes, but the mechanism triggering lysosomal exocytosis is unknown. Here we show that BCR-mediated high-affinity recognition of antigen tethered to beads or planar lipid-bilayers causes localized plasma membrane (PM) permeabilization, a process that requires BCR signaling and non-muscle myosin II activity. B-cell permeabilization triggers a PM repair response involving lysosomal exocytosis. B-cells transiently permeabilized by surface-associated antigen internalize more antigen than cells that remain intact, and higher affinity antigens that cause more B-cell permeabilization and lysosomal exocytosis are more efficiently presented to T-cells. Thus, PM permeabilization by surface-associated antigen triggers a lysosome-mediated B-cell resealing response, which provides the extracellular hydrolases that can facilitate antigen internalization and presentation.

scholarly journals Naïve Regulatory T Cell Subset Is Altered in X-Linked Agammaglobulinemia

2021 ◽  
Vol 12 ◽  
Author(s):  
Pavel V. Shelyakin ◽  
Ksenia R. Lupyr ◽  
Evgeny S. Egorov ◽  
Ilya A. Kofiadi ◽  
Dmitriy B. Staroverov ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
B Cell ◽  
Cell Subset ◽  
Cell Receptor ◽  
T Cell Subsets ◽  
Cell Compartments ◽  
Expression Of Genes ◽  
Tcr Repertoire ◽  
Antigen Presenting

The interplay between T- and B-cell compartments during naïve, effector and memory T cell maturation is critical for a balanced immune response. Primary B-cell immunodeficiency arising from X-linked agammaglobulinemia (XLA) offers a model to explore B cell impact on T cell subsets, starting from the thymic selection. Here we investigated characteristics of naïve and effector T cell subsets in XLA patients, revealing prominent alterations in the corresponding T-cell receptor (TCR) repertoires. We observed immunosenescence in terms of decreased diversity of naïve CD4+ and CD8+ TCR repertoires in XLA donors. The most substantial alterations were found within naïve CD4+ subsets, and we have investigated these in greater detail. In particular, increased clonality and convergence, along with shorter CDR3 regions, suggested narrower focused antigen-specific maturation of thymus-derived naïve Treg (CD4+CD45RA+CD27+CD25+) in the absence of B cells - normally presenting diverse self and commensal antigens. The naïve Treg proportion among naïve CD4 T cells was decreased in XLA patients, supporting the concept of impaired thymic naïve Treg selection. Furthermore, the naïve Treg subset showed prominent differences at the transcriptome level, including increased expression of genes specific for antigen-presenting and myeloid cells. Altogether, our findings suggest active B cell involvement in CD4 T cell subsets maturation, including B cell-dependent expansion of the naïve Treg TCR repertoire that enables better control of self-reactive T cells.

scholarly journals T Cell Accumulation in B Cell Follicles Is Regulated by Dendritic Cells and Is Independent of B Cell Activation

2003 ◽  
Vol 197 (2) ◽  
pp. 195-206 ◽  
Author(s):  
Simon Fillatreau ◽  
David Gray
Keyword(s):  
T Cells ◽  
Dendritic Cells ◽  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Cell Activation ◽  
B Cell Activation ◽  
Cell Accumulation ◽  
Antigen Presenting ◽  
Deficient Mice

We investigated the mechanism of CD4 T cell accumulation in B cell follicles after immunization. Follicular T cell numbers were correlated with the number of B cells, indicating B cell control of the niche that T cells occupy. Despite this, we found no role for B cells in the follicular migration of T cells. Instead, T cells are induced to migrate into B cell follicles entirely as a result of interaction with dendritic cells (DCs). Migration relies on CD40-dependent maturation of DCs, as it did not occur in CD40-deficient mice but was reconstituted with CD40+ DCs. Restoration was not achieved by the activation of DCs with bacterial activators (e.g., lipopolysaccharide, CpG), but was by the injection of OX40L–huIgG1 fusion protein. Crucially, the up-regulation of OX40L (on antigen-presenting cells) and CXCR-5 (on T cells) are CD40-dependent events and we show that T cells do not migrate to follicles in immunized OX40-deficient mice.

ZAP-70 Is Not Phosphorylated on the Activating Tyrosine Residue (Tyr319) in Chronic Lymphocytic Leukemia and B-Cell Lymphoma Cells.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 178-178
Author(s):  
Stefania Gobessi ◽  
Aleksandar Petlickovski ◽  
Luca Laurenti ◽  
Dimitar G. Efremov
Keyword(s):  
T Cells ◽  
B Cells ◽  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Progressive Disease ◽  
Cell Receptor ◽  
Kinase Domain ◽  
Lymphocytic Leukemia ◽  
Bcr Signaling ◽  
Cell Receptor Signaling

Abstract The protein tyrosine kinase ZAP-70 is expressed at high levels in leukemic B-cells from chronic lymphocytic leukemia (CLL) patients with progressive disease and short survival. ZAP-70 is a key component of the proximal T-cell receptor signaling pathway and is highly homologous to Syk, an important B-cell receptor signaling (BCR) molecule. Recent studies indicate that ZAP-70 may participate in BCR signaling as well, but the mechanism of action is still not well understood. In T-cells, upon TCR stimulation ZAP-70 becomes phosphorylated on Tyr319 by the Src-like kinase Lck, which results in the release of the ZAP-70 kinase domain from an autoinhibited state to a fully active conformation. The Tyr319 site in ZAP-70 corresponds to the Tyr352 site in Syk, which is phosphorylated in B-cells following BCR stimulation. We therefore investigated the activation status of ZAP-70 and Syk in BCR stimulated CLL B-cells, using phosphorylation of Tyr319 and Tyr352 as markers of their activation. Analysis of 10 ZAP-70-positive CLL samples by immunoblotting with the phospho-ZAP70Tyr319/SykTyr352 antibody revealed that ZAP-70 is not phosphorylated at this site either before or after BCR stimulation, although in control experiments with Jurkat T-cells ZAP-70 became phosphorylated on Tyr319 upon TCR stimulation. Moreover, the Tyr352 site in Syk was phosphorylated following BCR stimulation in 6 of the 10 CLL B-cell samples. To further investigate the reasons for the unexpected lack of ZAP-70 activation in CLL B-cells, we produced stable transfectants of the BJAB lymphoma B-cell line that expressed ZAP-70 at levels similar to those found in CLL cases with progressive disease. In agreement with the CLL B-cell experiments, the Tyr319 site in ZAP-70 was not phosphorylated either before or after BCR stimulation. Since phosphorylation of Tyr319 is Lck-dependent in T-cells, and this kinase is expressed also in CLL B-cells, we ectopically expressed Lck in the ZAP-70-positive BJAB clones. Again, the Tyr319 site was not phosphorylated, indicating that ZAP-70 does not undergo activation of the kinase domain also in this cellular system. In contrast, BCR crosslinking in BJAB cells induced significant phosphorylation of Tyr352 in Syk, which was further enhanced in the clones that coexpressed ZAP-70. Furthermore, analysis of downstream signaling pathways following BCR stimulation showed stronger and prolonged activation of ERK and to a lesser extent Akt in the ZAP-70 positive clones, whereas no difference was observed in terms of activation of PLC-γ 2, JNK and degradation of the NF-kB inhibitor IkB. These data indicate that ZAP-70 does not undergo full activation in B-cells, but can still enhance activation of certain downstream BCR signaling pathways, possibly by affecting the activity of the related PTK Syk.

Human B Cell Lines and Primary B Cells Actively Secrete Granzyme B in Response to IL-2 Family Cytokines.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 1340-1340
Author(s):  
Bernd Jahrsdoerfer ◽  
Sue E. Blackwell ◽  
Thomas Simmet ◽  
George J. Weiner
Keyword(s):  
T Cells ◽  
B Cells ◽  
B Cell ◽  
Cell Lines ◽  
Granzyme B ◽  
Cell Receptor ◽  
Lymphocytic Leukemia ◽  
Main Function ◽  
Dependent Manner ◽  
Unexpected Findings

Abstract It is widely believed that the main function of B cells is antibody secretion, but not cellular cytotoxicity. Recently we found that human B cells activated with interleukin 21 (IL-21) and antibodies to the B cell receptor (BCR) or immunostimulatory oligonucleotides (CpG ODN) develop a phenotype similar to that of cytotoxic T lymphocytes. B cells treated in such a way start to secrete large amounts of granzyme B (GrB) instead of antibodies and, as in the case of B-chronic lymphocytic leukemia (B-CLL), acquire the capability to induce apoptosis in bystander B-CLL cells in a GrB-dependent manner. Using FACS and ELISpot analyses we could now demonstrate that GrB is actively secreted by B cells in a time-dependent manner and that IL-21 is not the only cytokine that induces GrB in B cells. Also cytokine combinations such as IL-10 and IL-4 as well as IL-10 and IFN-alpha induce GrB in normal B cells and various B cell lines including MEC-1 (CLL), ARH-77 (plasma cell leukemia) and Namalwa (Burkitts lymphoma). We conclude that IL-21 and further cytokines can induce B cells to produce functional granzyme B. Further studies are required to elucidate the interactions with B lymphocytes of cells producing these cytokines such as CD4+ T cells, regulatory T cells, NKT cells and plasmacytoid dendritic cells. Our unexpected findings could have significant implications on our understanding of the role of B cells in immune regulation and for a variety of immune phenomena including auto-, cancer and infectious immunity.

Targeting STAT3 Signaling to Augment the Immunogenicity of B-Cell Lymphomas

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 708-708
Author(s):  
Hongwei Wang ◽  
F. Cheng ◽  
K. Wright ◽  
J. Tao ◽  
M. Smith ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
B Cells ◽  
Dna Binding ◽  
B Cell ◽  
Cd4 T Cells ◽  
Mutant Form ◽  
B Cell Lymphomas ◽  
Stat3 Signaling ◽  
Antigen Presenting

Abstract STAT3 signaling has emerged as a negative regulator of inflammatory responses in immune cells. In bone-marrow derived antigen-presenting cells (APCs), genetic or pharmacologic disruption of STAT3 led to inflammatory cells that effectively prime antigen-specific T-cell responses and restore the responsiveness of tolerized T-cells. In contrast, enhanced Stat3 activity in APCs resulted in increased production of the immunosuppressive cytokine IL-10 and induction of T-cell tolerance1. B-cell lymphomas being tumors derived from B-lymphocytes display intrinsic antigen-presenting capabilities. Augmentation of this APC function has been shown to result in effective anti-lymphoma immunity2. In this study we determined whether targeting Stat3 signaling might influence the intrinsic APC function of malignant B-cells and the responsiveness –or not- of antigen-specific CD4+ T-cells. First, we specifically block STAT3 signaling in A20 lymphoma B-cells by using a dominant negative variant of STAT3, Stat3b. Inhibition of STAT3 resulted in tumor cells capable not only of fully priming naïve antigen-specific CD4+T-cells but also able of restoring the responsiveness of tolerant T-cells from lymphoma bearing mice. Conversely, transfection of A20 B-cells with Stat3c, a constitutively activated mutant form of STAT3, led to T-cell unresponsiveness. Of note, manipulation of STAT3 in B cell tumors was associated with changes in the mRNA expression and protein levels of IL-10. Second, we evaluated the effects of two novel Stat3 inhibitors, CPA-7 (a platinum-containing compound that disrupts STAT3 DNA binding activity) and S3I-201 (inhibitor of Stat3:Stat3 complex formation and Stat3 DNA binding and transcriptional activities) in a murine model of Mantle Cell Lymphoma (MCL). In vitro treatment of FC-muMCL1 cells - derived from a tumor elicited in Em-Cyclin D1 transgenic mice- with increasing concentrations of either CPA-7 or S3I-201 resulted in an enhanced presentation of OVA-peptide to naïve CD4+ T-cells specific for a MHC class II restricted epitope of ovalbumin (OT-II cells). Indeed, these T-cells produce higher levels of IL-2 and IFN-gamma compared to anti-OVA T cells that encountered cognate antigen in untreated FC-muMCL1 cells. More importantly, MCL cells treated with CPA-7 restored the responsiveness of tolerized anti-OVA CD4+ T-cells. Finally, in vivo treatment of MCL-bearing mice with CPA-7 (5 mg/kg/iv given on days +21, +24 and +27 after tumor challenge) resulted in significant inhibition of p-Stat3 in malignant B-cells and augmentation of their APC function. Taken together, STAT3 signaling is involved in the regulation of the antigen-presenting capabilities of B-cell lymphomas and as such represents a novel molecular target to augment the immunogenicity of these tumors.

scholarly journals Antigen presentation by resting B cells. Radiosensitivity of the antigen-presentation function and two distinct pathways of T cell activation.

1984 ◽  
Vol 159 (3) ◽  
pp. 881-905 ◽  
Author(s):  
J D Ashwell ◽  
A L DeFranco ◽  
W E Paul ◽  
R H Schwartz
Keyword(s):  
Cell Proliferation ◽  
T Cells ◽  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Antigen Presentation ◽  
Cell Activation ◽  
T Cell Proliferation ◽  
B Cell Activation ◽  
Antigen Presenting

In this report we have examined the ability of small resting B cells to act as antigen-presenting cells (APC) to antigen-specific MHC-restricted T cells as assessed by either T cell proliferation or T cell-dependent B cell stimulation. We found that 10 of 14 in vitro antigen-specific MHC-restricted T cell clones and lines and three of four T cell hybridomas could be induced to either proliferate or secrete IL-2 in the presence of lightly irradiated (1,000 rads) purified B cells and the appropriate foreign antigen. All T cell lines and hybridomas were stimulated to proliferate or make IL-2 by macrophage- and dendritic cell-enriched populations and all T cells tested except one hybridoma caused B cell activation when stimulated with B cells as APC. Furthermore, lightly irradiated, highly purified syngeneic B cells were as potent a source of APC for inducing B cell activation as were low density dendritic and macrophage-enriched cells. Lymph node T cells freshly taken from antigen-primed animals were also found to proliferate when cultured with purified B cells and the appropriate antigen. Thus, small resting B cells can function as APC to a variety of T cells. This APC function was easily measured when the cells were irradiated with 1,000 rads, but was greatly diminished or absent when they were irradiated with 3,300 rads. Thus, the failure of some other laboratories to observe this phenomenon may be the result of the relative radiosensitivity of the antigen-presenting function of the B cells. In addition, this radiosensitivity allowed us to easily distinguish B cell antigen presentation from presentation by the dendritic cell and macrophage, as the latter was resistant to 3,300 rads. Finally, one T cell clone that failed to proliferate when B cells were used as APC was able to recruit allogeneic B cells to proliferate in the presence of syngeneic B cells and the appropriate antigen. This result suggests that there are at least two distinct pathways of activation in T cells, one that leads to T cell proliferation and one that leads to the secretion of B cell recruitment factor(s).

scholarly journals Spontaneous relapsing-remitting EAE in the SJL/J mouse: MOG-reactive transgenic T cells recruit endogenous MOG-specific B cells

2009 ◽  
Vol 206 (6) ◽  
pp. 1303-1316 ◽  
Author(s):  
Bernadette Pöllinger ◽  
Gurumoorthy Krishnamoorthy ◽  
Kerstin Berer ◽  
Hans Lassmann ◽  
Michael R. Bösl ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
B Cells ◽  
Transgenic Mice ◽  
B Cell ◽  
Cell Receptor ◽  
Conformational Epitope ◽  
Autoreactive B Cells ◽  
Spinal Cord Development ◽  
Relapsing Remitting

We describe new T cell receptor (TCR) transgenic mice (relapsing-remitting [RR] mice) carrying a TCR specific for myelin oligodendrocyte glycoprotein (MOG) peptide 92–106 in the context of I-As. Backcrossed to the SJL/J background, most RR mice spontaneously develop RR experimental autoimmune encephalomyelitis (EAE) with episodes often altering between different central nervous system tissues like the cerebellum, optic nerve, and spinal cord. Development of spontaneous EAE depends on the presence of an intact B cell compartment and on the expression of MOG autoantigen. There is no spontaneous EAE development in B cell–depleted mice or in transgenic mice lacking MOG. Transgenic T cells seem to expand MOG autoreactive B cells from the endogenous repertoire. The expanded autoreactive B cells produce autoantibodies binding to a conformational epitope on the native MOG protein while ignoring the T cell target peptide. The secreted autoantibodies are pathogenic, enhancing demyelinating EAE episodes. RR mice constitute the first spontaneous animal model for the most common form of multiple sclerosis (MS), RR MS.

scholarly journals Immune Cell Profiling of COVID-19 Patients in the Recovery Stage by Single-Cell Sequencing

2020 ◽  
Author(s):  
Wen Wen ◽  
Wenru Su ◽  
Hao Tang ◽  
Wenqing Le ◽  
Xiaopeng Zhang ◽  
...  
Keyword(s):  
T Cells ◽  
B Cells ◽  
B Cell ◽  
Single Cell ◽  
Hospital Discharge ◽  
Immune Cell ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Early Recovery ◽  
Recovery Stage

AbstractCOVID-19, caused by SARS-CoV-2, has recently affected over 300,000 people and killed more than 10,000. The manner in which the key immune cell subsets change and their states during the course of COVID-19 remain unclear. Here, we applied single-cell technology to comprehensively characterize transcriptional changes in peripheral blood mononuclear cells during the recovery stage of COVID-19. Compared with healthy controls, in patients in the early recovery stage (ERS) of COVID-19, T cells decreased remarkably, whereas monocytes increased. A detailed analysis of the monocytes revealed that there was an increased ratio of classical CD14++ monocytes with high inflammatory gene expression as well as a greater abundance of CD14++IL1B+ monocytes in the ERS. CD4+ and CD8+ T cells decreased significantly and expressed high levels of inflammatory genes in the ERS. Among the B cells, the plasma cells increased remarkably, whereas the naïve B cells decreased. Our study identified several novel B cell-receptor (BCR) changes, such as IGHV3-23 and IGHV3-7, and confirmed isotypes (IGHV3-15, IGHV3-30, and IGKV3-11) previously used for virus vaccine development. The strongest pairing frequencies, IGHV3-23-IGHJ4, indicated a monoclonal state associated with SARS-CoV-2 specificity. Furthermore, integrated analysis predicted that IL-1β and M-CSF may be novel candidate target genes for inflammatory storm and that TNFSF13, IL-18, IL-2 and IL-4 may be beneficial for the recovery of COVID-19 patients. Our study provides the first evidence of an inflammatory immune signature in the ERS, suggesting that COVID-19 patients are still vulnerable after hospital discharge. Our identification of novel BCR signaling may lead to the development of vaccines and antibodies for the treatment of COVID-19.Highlights-The immune response was sustained for more than 7 days in the early recovery stage of COVID-19, suggesting that COVID-19 patients are still vulnerable after hospital discharge.-Single-cell analysis revealed a predominant subset of CD14++ IL1β+ monocytes in patients in the ERS of COVID-19.-Newly identified virus-specific B cell-receptor changes, such as IGHV3-23, IGHV3-7, IGHV3-15, IGHV3-30, and IGKV3-11, could be helpful in the development of vaccines and antibodies against SARS-CoV-2.-IL-1β and M-CSF were discovered as novel mediators of inflammatory cytokine storm, and TNFSF13, IL-2, IL-4, and IL-18 may be beneficial for recovery.

CD8+ T Cells Engineered to Express a ROR1-Specific Chimeric Antigen Receptor Specifically Recognize ROR1 Positive B Cell Tumors.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 930-930
Author(s):  
Michael Hudecek ◽  
Thomas M Schmitt ◽  
Sivasubramanian Baskar ◽  
Wen-Chung Chang ◽  
David G Maloney ◽  
...  
Keyword(s):  
T Cells ◽  
B Cells ◽  
Tyrosine Kinase ◽  
B Cell ◽  
Cell Line ◽  
Chimeric Antigen Receptor ◽  
Cd8 T Cells ◽  
Antigen Receptor ◽  
Cell Receptor ◽  
Surface Expression

Abstract Abstract 930 The orphan tyrosine kinase receptor ROR1 was previously identified as a highly expressed gene by expression profiling of B cell chronic lymphocytic leukemia (B-CLL), [Klein et al. J Exp Med 2001], and has subsequently been shown to be expressed on mantle cell lymphoma (MCL) and a subset of B cell acute lymphoblastic leukemias (B-ALL). ROR1 encodes a 105 kDa protein that contains Ig-like, cysteine rich, kringle, tyrosine kinase and proline rich domains and is expressed during embryonic development but is absent on normal adult tissues including non-malignant B cells. The function of ROR1 in normal and malignant cells is not known, although secreted Wnt proteins have been proposed as candidate ligands. Analysis of ROR1 protein expression using specific polyclonal antibodies revealed uniform, stable, and restricted cell surface expression on B-CLL, suggesting this molecule is a candidate for targeted immunotherapy of B cell malignancies [Baskar et al. Clin Cancer Res 2008]. We constructed a lentiviral vector that encodes a chimeric antigen receptor (CAR) consisting of single chain variable (scFV) fragments of the heavy and light chains of a murine monoclonal antibody specific for ROR1, linked to an IgG4 Fc domain, the T cell receptor CD3 zeta chain and a CD28 costimulatory domain. The specificity and function of the ROR1 CAR was compared with a similarly designed CAR specific for the CD20 molecule, which is expressed on both malignant and normal B cells, and is being targeted with gene-modified T cells in clinical trials. Primary human CD8+ T cells were transduced with the ROR1 and CD20-specific CARs respectively, and T cells expressing high levels of the receptors were sort-purified using an anti-Fc antibody. T cells that expressed either the ROR1-specific CAR or the CD20-specific CAR efficiently lysed primary B-CLL samples (5/5) obtained from patients with advanced disease, and also lysed a MCL cell line (JeKo-1), and a ROR1+ B-ALL cell line (BALL-1). ROR1-specific T cells did not recognize the myeloid leukemia cell line K562, but efficiently lysed K562 cells that had been transfected to express ROR1, confirming the specific recognition of ROR1 on target cells. Consistent with the expression pattern of the target molecules, T cells that expressed the CD20-specific CAR also efficiently lysed normal primary and EBV-transformed B cells, but T cells that expressed the ROR1-specific CAR did not recognize nonmalignant or EBV-transformed B cells. Activation of normal B cells by engagement of the B cell receptor or activation through CD40 induced B cell proliferation and upregulation of the CD80 and CD86 costimulatory molecules, but did not result in ROR1 surface expression by flow cytometry or recognition by T cells that expressed the ROR1-specific CAR. These results suggest that targeting ROR1 with gene-modified T cells may have advantages over targeting B cell-lineage restricted molecules such as CD19 and CD20 that are expressed on normal mature B cells. Studies to determine whether ROR1 is expressed during a stage of normal B cell development are in progress. ROR1 is highly conserved in non-human primates and this model may be suitable to determine potential toxicities of adoptive immunotherapy with ROR1-specific CAR expressing T cells. Disclosures: No relevant conflicts of interest to declare.

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