Xiaoxiao Wan, PhD

Our laboratory focuses on examining pathogenic events responsible for initiating the development of tissue-specific autoimmune diseases. We primarily employ mouse experimental models to mechanistically dissect key factors involved in type 1 diabetes, a deteriorating autoimmune disorder that eventually destroys insulin-producing β-cells in the pancreatic islets. The research projects center on 1) Identifying antigenic targets involved in disease pathogenesis, which not only serves as a platform for activating antigen-specific autoreactive T cells but also can be used as diagnostic and therapeutic targets; 2) Examining the biological behaviors of the tissue innate immune system that finely tunes tissue homeostasis and shapes the phenotypic signatures of localized autoimmunity.
Identify MHC-II epitopes required for initiating type 1 diabetes. We recently identified a specific site in pancreatic β cells, the crinosomes, responsible for generating disease-relevant peptides. Crinosomes are a specific set of vesicles formed by fusion of insulin granules with lysosomes. As an enzyme-rich structure, crinosomes not only generate unique or “cryptic” epitopes from degraded protein segments but also produce neoepitopes formed by post-translational modifications. These immunogenic materials are released into circulation during β-cell degranulation and become an antigen source for sensitizing peripheral lymphoid tissues. We are working on to better understand crinosome biology and apply this knowledge to diagnostic and therapeutic aspects of type 1 diabetes. Using a platform integrating mass spectrometry with immunological characterization, we are moving forward to determine disease-relevant epitopes in the islets and peripheral blood from humans with type 1 diabetes.
Examine the role of tissue microenvironment in islet biology and autoimmunity. The pancreatic islet is a mini organ essential for maintaining body metabolism. This tissue contains several types of endocrine cells, including the insulin-producing β cells, but only consists of one immune cell, the resident macrophages. Lineage tracing studies indicate that islet macrophages derive from definitive hematopoiesis. The islet macrophages are in intimate contact with β cells, extending long filopodia in between them. Some of these filopodia enter the blood lumen and can capture microparticles. Islet macrophages isolated from different mouse strains (NOD, NOD.Rag1–/–, B6) have a high expression of genes encoding MHC-II, costimulatory molecules, and inflammatory cytokines and chemokines. We consider such an activation state as a self-defensive mechanism for protecting the islets from pathogen infections. However, autoimmune risk can also be precipitated to foster incoming autoimmune responses. We seek to dissect the key factors expressed by the islet macrophages that not only influence β-cell biology during homeostasis but also play a role in the pathogenesis of autoimmune diabetes.