Projects & Collaborations 2 foundShow per page10 10 20 50 B cells and antibodies in autoimmune CNS diseases Research Project | 4 Project MembersMultiple sclerosis (MS) is a serious disease of the central nervous system (CNS) involving destruction of the myelin sheaths and axons, and chronic immune activity inside the brain and spinal cord. The commonest disease course involves relapses with new neurological symptoms, followed by remission, against a background of slowly worsening disability known as progression. Several treatments are available to prevent relapses but their impact on progression is moderate and decreases with disease duration. In particular, depleting CD20-expressing cells with monoclonal antibodies such as rituximab is highly effective in the relapsing-remitting stage of the diseases. The majority of CD20-expressing cells are B cells, and the speed of the therapeutic effect suggests that peripheral, rather than CNS-resident B cells are the target. We describe two alternative hypothetical mechanisms that could explain the involvement of peripheral B cells in causing demyelinating lesions within the CNS, and propose experiments to test them. We assume that lymphocyte invasion of the CNS is initiated by T cells that encounter their cognate antigen within the CNS. The first hypothesis posits that these T cells are responding to a non-autoimmune stimulus such as a virus reactivation, and that the autoimmune component is mediated by B cells. The second hypothesis posits that the pioneer T cells are themselves autoreactive, and are activated by B cells in the periphery. 1.2 Overall ObjectiveThe objective of this project is to test two competing hypotheses to explain the mechanism of action of CD20 depletion, and to investigate whether the same mechanisms are connected to the more serious problem of ongoing progression. This will require the acquisition of much basic information about the biology of B cell trafficking, most of which will be done with animal models. We will also test some predictions of the two hypotheses in the real disease, using samples from patients with MS, and suitable controls.1.3 Specific Aims We aim to test the following hypotheses:Hypothesis 1: Relapses are caused by myelin-reactive B cells that traffic into the brain in response to local immune activity, and secrete myelin-binding antibodies.Hypothesis 2: Relapses are caused by autoreactive T cells, activated by virus-specific B cells that have co-captured self antigens, in the context of a peripheral viral infection. B cells and antibodies in autoimmune CNS diseases Research Project | 6 Project MembersOur goal is to understand the causes of autoimmune neurological disorders, particularly multiple sclerosis. The cause of MS is unknown, but strong evidence implicates a dysfunction of the immune system. Clinically, patients present with disturbances of sensorimotor and other central nervous system functions, and histologically the disease is characterized by demyelinated areas of brain and spinal cord, with infiltrations of immune cells. The most effective therapies target lymphocytes, by depletion, prevention of proliferation, or prevention of trafficking into the CNS. The most precisely targeted effective therapies are B cell depleting agents, and the most significant lab finding are oligoclonal expanded immunoglobulins in the cerebrospinal fluid, suggesting that B cells are an important component of MS. We are studying the role of this cell type in two complementary approaches. Observationally we are isolating and characterizing autoreactive B cells from patients; and experimentally we are trying to understand how autoreactive B cells can escape from tolerance. Our working hypothesis is that if autoreactive B cells capture their cognate self antigen from a virus-infected cell that also co-expresses viral antigens, these viral antigens can be co-captured by the B cell and presented to T cells, thus qualifying the B cell for fraudulent T cell help and circumventing the normal tolerance mechanism. Isolation and characterization of autoreactive B cells from patientsAutoantibodies involved in neurological diseases often bind to membrane proteins such as ion channels, neurotransmitter receptors and myelin proteins, and often recognize conformational epitopes, rather than simple amino acid sequences. This makes them difficult subjects for traditional antibody techniques such as western blotting and immunoprecipitation, which often involve denaturation steps. We have developed a novel technique for isolating B cells recognizing membrane protein antigens in their native conformation. We plan to characterize B cells identified using this process from the blood and CSF of patients with neurological symptoms. B cell escape from tolerance by viral antigen co-capture.Secretion of autoreactive antibodies is normally avoided directly by the elimination of self-reactive B cells, and indirectly by the elimination of self-reactive T cells, thus depriving self-reactive B cells of the T cell help needed for development into antibody-secreting plasma cells. It is not known why this mechanism fails in autoimmune diseases, but we hypothesize that the second mechanism could be overcome by self-reactive B cells that co-capture both self and viral antigens from the membranes of virus-infected cells and present them to virus-specific T cells. We have observed this phenomenon in vitro using mouse cells, and now plan to examine the plausibility of the process in human cells and in animal models. 1 1
B cells and antibodies in autoimmune CNS diseases Research Project | 4 Project MembersMultiple sclerosis (MS) is a serious disease of the central nervous system (CNS) involving destruction of the myelin sheaths and axons, and chronic immune activity inside the brain and spinal cord. The commonest disease course involves relapses with new neurological symptoms, followed by remission, against a background of slowly worsening disability known as progression. Several treatments are available to prevent relapses but their impact on progression is moderate and decreases with disease duration. In particular, depleting CD20-expressing cells with monoclonal antibodies such as rituximab is highly effective in the relapsing-remitting stage of the diseases. The majority of CD20-expressing cells are B cells, and the speed of the therapeutic effect suggests that peripheral, rather than CNS-resident B cells are the target. We describe two alternative hypothetical mechanisms that could explain the involvement of peripheral B cells in causing demyelinating lesions within the CNS, and propose experiments to test them. We assume that lymphocyte invasion of the CNS is initiated by T cells that encounter their cognate antigen within the CNS. The first hypothesis posits that these T cells are responding to a non-autoimmune stimulus such as a virus reactivation, and that the autoimmune component is mediated by B cells. The second hypothesis posits that the pioneer T cells are themselves autoreactive, and are activated by B cells in the periphery. 1.2 Overall ObjectiveThe objective of this project is to test two competing hypotheses to explain the mechanism of action of CD20 depletion, and to investigate whether the same mechanisms are connected to the more serious problem of ongoing progression. This will require the acquisition of much basic information about the biology of B cell trafficking, most of which will be done with animal models. We will also test some predictions of the two hypotheses in the real disease, using samples from patients with MS, and suitable controls.1.3 Specific Aims We aim to test the following hypotheses:Hypothesis 1: Relapses are caused by myelin-reactive B cells that traffic into the brain in response to local immune activity, and secrete myelin-binding antibodies.Hypothesis 2: Relapses are caused by autoreactive T cells, activated by virus-specific B cells that have co-captured self antigens, in the context of a peripheral viral infection.
B cells and antibodies in autoimmune CNS diseases Research Project | 6 Project MembersOur goal is to understand the causes of autoimmune neurological disorders, particularly multiple sclerosis. The cause of MS is unknown, but strong evidence implicates a dysfunction of the immune system. Clinically, patients present with disturbances of sensorimotor and other central nervous system functions, and histologically the disease is characterized by demyelinated areas of brain and spinal cord, with infiltrations of immune cells. The most effective therapies target lymphocytes, by depletion, prevention of proliferation, or prevention of trafficking into the CNS. The most precisely targeted effective therapies are B cell depleting agents, and the most significant lab finding are oligoclonal expanded immunoglobulins in the cerebrospinal fluid, suggesting that B cells are an important component of MS. We are studying the role of this cell type in two complementary approaches. Observationally we are isolating and characterizing autoreactive B cells from patients; and experimentally we are trying to understand how autoreactive B cells can escape from tolerance. Our working hypothesis is that if autoreactive B cells capture their cognate self antigen from a virus-infected cell that also co-expresses viral antigens, these viral antigens can be co-captured by the B cell and presented to T cells, thus qualifying the B cell for fraudulent T cell help and circumventing the normal tolerance mechanism. Isolation and characterization of autoreactive B cells from patientsAutoantibodies involved in neurological diseases often bind to membrane proteins such as ion channels, neurotransmitter receptors and myelin proteins, and often recognize conformational epitopes, rather than simple amino acid sequences. This makes them difficult subjects for traditional antibody techniques such as western blotting and immunoprecipitation, which often involve denaturation steps. We have developed a novel technique for isolating B cells recognizing membrane protein antigens in their native conformation. We plan to characterize B cells identified using this process from the blood and CSF of patients with neurological symptoms. B cell escape from tolerance by viral antigen co-capture.Secretion of autoreactive antibodies is normally avoided directly by the elimination of self-reactive B cells, and indirectly by the elimination of self-reactive T cells, thus depriving self-reactive B cells of the T cell help needed for development into antibody-secreting plasma cells. It is not known why this mechanism fails in autoimmune diseases, but we hypothesize that the second mechanism could be overcome by self-reactive B cells that co-capture both self and viral antigens from the membranes of virus-infected cells and present them to virus-specific T cells. We have observed this phenomenon in vitro using mouse cells, and now plan to examine the plausibility of the process in human cells and in animal models.
