THE ROLE OF ENDOPLASMIC RETICULUM STRESS IN TYPE 1 DIABETES: IDENTIFICATION OF GLUCOSE REGULATED PROTEIN 78 AS THE AUTOANTIGEN FOR BDC-2.5 T CELL CLONE.

摘要

Environmental triggers, such as viral infection and environmental toxins, have been proposed to initiate the autoimmune disease of Type 1 Diabetes (T1D), however, the mechanism is unknown. The identification of novel autoantigens may provide insight to the mechanism of environmental triggers and pathogenesis of T1D. I identified the antigen recognized by the diabetogenic BDC- 2.5 T cell clone using a novel in vivo reconstitution system, Restricted Immune System via Adoptive Transfer (RISAT). In RISAT, immunodeficient mice are adoptive transferred with a single T cell clone and an open repertoire of B cells. Reconstituted mice are immunized with an antigenic protein preparation. This system will drive an antibody response to the cognate antigen for the T and B cell through the co-stimulatory pathways involved in linked recognition. For the BDC-2.5 RISAT, non-obese diabetic (NOD).Rag-/- mice were adoptive transferred with the diabetogenic BDC-2.5 T cells and NOD B cells and then immunized with an antigenic beta cell membrane preparation (βmem) to drive an antibody response. The resulting antibodies recognized the endoplasmic reticulum (ER) stress associated protein glucose regulated protein 78 (GRP78) from βmem. To determine if ER stress plays a role in the antigenic response of the BDC-2.5 T cell clone, the non-antigenic NOD insulinoma cell line, NIT-1, were treated with thapsigargin, which induces ER stress. The treatment of NIT-1 with thapsigargin led to increased GRP78 synthesis, correlating with antigenic recognition by the BDC-2.5 T cell clone. The antibodies from the BDC-2.5 TCR-Tg recognizes a subset of GRP78 which is modified with phosphoserine. The data presented in this thesis demonstrates a mechanistic link between ER stress and environmental triggers leading to the initiation of TID through the novel autoantigen, GRP78. Also the technique, RISAT, can be used to identify additional potential autoantigens of isolated T cell clones in both T1D and other autoimmune diseases.