Th106 - TCR repertoire analysis in Human Immune System Mice Derived from Type 1 Diabetic and Healthy Control Hematopoietic Cells

Benjamin Vermette – Columbia University Irving Medical Center; Mohsen Maharlooei – Columbia University Irving Medical Center; Robert Winchester – Columbia University Irving Medical Center; Megan Sykes – Columbia University Irving Medical Center

Abstract Text: The extent to which thymic selection and formation of TCR repertoire contributes to Type 1 Diabetes (T1D) is unknown due to limited accessibility of human thymic tissue and our inability to manipulate variables in vivo. However, Human Immune System (HIS) mice generated with human thymus and partially HLA-matched Hematopoietic Stem Cells (HSCs) from Type 1 Diabetic (T1D) and Healthy Controls (HC) (Personalized Immune, PI mice) provide a system in which to investigate TCR repertoire development in vivo. Thymocyte subsets from T1D or HC PI mice were sorted, gDNA extracted and high throughput TCRβ-CDR3 sequencing carried out (Adaptive Biotech). Analysis utilizing TiRP score (Lagattuta et al., 2022) revealed increased TiRP scores in the CD4SP subset compared to DP CD69+ cells in one T1D PI mouse, whereas it remained constant in the HLA-matched HC PI mouse, suggesting failed negative selection of autoreactive TCRs in the T1D system. Consistently, CDR3 hydrophobicity as a measure of autoreactivity revealed greater hydrophobicity in CD4SP cells of the T1D PI mouse as compared to the DP CD69+ population. Analysis of two HC PI mice revealed increasing hydrophobicity as the cells mature from DP CD69- to DP CD69+ but no change as the thymocytes mature into Tconv CD4SP. However, Treg CD4SP cells demonstrated appropriate increased hydrophobicity scores. These results support previous observations of diminished negative selection of an islet autoreactive TCR in T1D PI mice. Additional analysis of thymocytes in T1D and HC PI mice is currently in process to further substantiate these initial observations.