DESCRIPTION (provided by applicant): We will take advantage of a unique observation from our laboratory, based on our work in primary biliary cirrhosis (PBC), considered a model autoimmune disease, that plasmablasts (PB) play a critical role in ongoing immune activation and loss of tolerance. We have demonstrated the striking finding that in PBC, on average, 10% of the total IgG and IgA and 23% of the IgM PB population, are specific for the immunodominant mitochondrial autoantigen, PDC-E2, the signature autoantigen in this disease. Further, our data reflect that PB-derived autoantibodies recognize only native PDC-E2, whereas serum from the same patient recognize native PDC-E2 and xenobiotic modified PDC-E2. These data take on additional significance based on work suggesting that PBC is induced following exposure to environmental chemicals that facilitate loss of tolerance in genetically susceptible hosts. Sera autoantibodies reflect long-term resident plasma cells, whereas the PB reactivity reflects current and ongoing B cell responses. Our data suggests that a better understanding of PB is key to dissecting the loss of immune tolerance that leads to biliary autoimmunity and we postulate that there are two categories of PB that are critical in the inflammatory liver microenvironment, including 1) PB arising from memory B cells, previously primed by xenobiotics, subsequently undergoing somatic hypermutation to obtain higher affinity for PDC-E2 while losing their binding activity for the priming xenobiotics, and 2) PB derived from naive B cells directly activated by PDC-E2 autoantigen and memory B cells originally primed by PDC-E2. We will address this proposal using two specific aims. Firstly, we will elucidate in detail the ongoing PDC-E2 specific PB response through global characterization of the autoantigen-specific PB cell repertoire, including isotype distribution and lineage structure of the B cell clones in each isotype. This wil allow us to identify PDC-E2-specific clones of each Ig isotype and provides an overall picture for the ongoing autoreactive PB response in PBC. We expect to identify evolutionally related IgG and IgA clones to those in the IgM population, which are likely derived from naive or re-activated memory B cells primed by PDC-E2 autoantigen, as well as the independent clones that are derived from memory B cells potentially primed by xenobiotics. Second, to verify that PDC-E2 specific PB reactivities arose originally from xenobiotic reactive antibodies, we will revert highl mutated PDC-E2-specific IgG or IgA sequences back to their germline sequences. Functionally relevant binding activities to native PDC-E2 and xenobiotics will be compared between PB-derived mAb and germline reverted Ig clones. These data will provide evidence for the environmental etiology of PBC and allow us to produce recombinant mAbs against PDC-E2 and germline reverted engineered antibodies, powerful tools for a functional approach to address the pathogenic functions of AMAs and xenobiotic-reactive antibodies. Finally, our approach of reverting hypermutated antibody to germline sequences provides a unique molecular approach to defining the role of B cells in loss of tolerance.
|Effective start/end date||12/1/14 → 11/30/16|
- National Institutes of Health: $194,896.00
- National Institutes of Health: $235,063.00
- Immunology and Microbiology(all)