Project Summary/Abstract Type 1 diabetes (T1D) is an autoimmune disorder characterized by destruction of the pancreatic beta cells, leading to decreased production of insulin and hyperglycemia. Although T cells are the primary effectors of beta cell destruction in T1D, autoreactive B cells are thought to be essential contributors as antigen presenting cells. Moreover, recent findings indicate that B cells appear to play a more pathogenic role in individuals who develop T1D at an earlier age. Studies have shown that young onset T1D subjects have increased B cells in their blood and an increased frequency of B cells in their pancreas compared to later onset T1D subjects. Importantly, this age-specific B cell signature is also associated with rapid progression of disease. Despite the recent evidence for B cell participation in a more aggressive form of disease, little is known regarding the phenotype and function of B cells in subjects at different ages of onset. Recently we developed a robust 38+ B cell panel for high dimensional single-cell mass cytometry to simultaneously identify total and insulin-reactive B cells, the various B cell subpopulations, and their activation and functional status, allowing for a more granular characterization of B cells. Using this comprehensive B cell panel, in aim 1 we will determine whether a specific B cell subset / phenotype exists in the peripheral blood of young onset T1D subjects and a portion of at-risk autoantibody positive prediabetics, which could explain their rapid progression of disease. In aim 2 we will compare the B cell population in paired spleen and pancreatic lymph node samples from early onset, late onset, and control organ donors to determine whether a specific B cell subset has migrated from the periphery (spleen) to the site of inflammation (pancreatic lymph node). The potential impact of these studies lies in identification of the pathogenic B cell(s) responsible for the rapid progression of disease, which will inform our understanding of the aggressiveness of early onset T1D and increase the precision of future age appropriate therapeutics.

Project Narrative Recent evidence suggests a more pathogenic role for B lymphocytes in type 1 diabetic (T1D) subjects diagnosed at an early age compared to older onset subjects. In this application we propose to analyze the total and insulin-reactive B cell compartment, including their activation state and signaling response, in young onset T1D, older onset T1D, autoantibody positive prediabetics, and controls using a comprehensive 38+ marker B cell panel and mass cytometry. The overarching goal of this work is to identify whether a unique B cell subset exists in early onset T1D, which would inform our understanding of the pathogenesis and rapid progression seen in young T1D patients and aid in future age-appropriate therapeutic targets to treat the disease.