How autoreactive B cells see their antigen: understanding the anti-TG2 response in celiac disease from characterization of patient-derived recombinant monoclonal antibodies.
B cells are an important arm of the adaptive immune system. The B-cell receptor undergoes genetic rearrangement to generate a vast repertoire of specificities. We can therefore produce antibodies against almost any pathogenic threat. B-cells that recognize structures in our own body are normally removed or tightly regulated. This regulation fails in many autoimmune diseases. To understand why and how autoreactive B cells can be activated we need to study diseases where we both know the B cell autoantigen and can obtain patient material that contain the autoreactive B-cells. This we can to in celiac disease.
Celiac disease is a curious case of autoimmunity. Celiac disease is caused by an aberrant and harmful immune response to gluten proteins from wheat that leads to intestinal destruction (Figure 1). In addition, all patients develop an autoimmune B-cell response towards the enzyme Transglutaminase 2 (TG2). TG2 modifies dietary gluten peptides so that they become immunogenic and activate pro-inflammatory CD4 T-cells. The autoantibody production towards TG2 depends on dietary gluten and we believe that the gluten-specific T cells give help to the autoreactive B-cells. However, we still do not know how and where the B cells see their antigen, TG2, in vivo.
We can isolate TG2-specific effector B cells (plasma cells) from the small intestine of CD patients to sequence and clone their immunoglobulin genes. We have seen that all patients develop a strong antibody response towards the N-terminal region of TG2, while almost no antibodies appear to recognize the C-terminal C2-domain of the protein. B-cells need to capture and internalize their antigen to become activated and produce antibodies. We know that TG2 can bind to extracellular matrix (ECM) proteins and this will likely influence how exposed the different protein regions are. We have recently discovered that TG2 binds to the ECM predominantly via a part of its C2 domain. We therefore hypothesize that the epitope bias in the CD anti-TG2 response can tell us how these B-cells see their autoantigen in the body. Testing this hypothesis will be important understand how autoantibody responses develop.
The project: Plasma cells that recognize the TG2 C2 domain exists in CD patients, but are rare and not yet characterized on the immunoglobulin level. The master student will clone and express a panel of TG2 C2-domain specific autoantibodies (Figure 1). These antibodies will be expressed in HEK293 cells as human IgG1 and purified by protein G affinity purification. The student will fine map the epitopes using recombinant TG2 and address whether the antibodies recognize TG2 in situ in tissue sections. All required methodology is well established in the lab.
Methods: Recombinant antibody expression in mammalian cells, protein purification, ELISA, immunohistochemistry and fluorescence microscopy.
What we expect from you: We seek a highly motivated and curious candidate. The tasks are well defined and the project as such of low risk. The potential implications of the outcome are high. We expect you to work hard, read relevant literature and spend time to understand why this project is important. We expect you to acquire good laboratory skills, become independent, but also learn when to ask for help. We expect you to learn a lot from this year!
What you will get from us: You will be part of a large, multinational research group (20+) that is world leading in mucosal immunology and celiac disease. You will meet fellow master students but also many experienced researches (Ph.D, post doc and researcher level) that can help you. You will take part in weekly scientific meetings as well as journal clubs and other group activities. If you aim for a career in research and a Ph.D in immunology this is where you should start.
The environment: The group of Prof. Ludvig Sollid is part of the K.G Jebsen Coeliac Disease Research Centre at the Institute of Immunology (Medical faculty, Rikshospitalet), a translational research center that studies all aspects of celiac disease. The research environment in the group and at the institute is ambitious, dynamic and highly collaborative.