294-OR: The Type 1 Diabetes Protective Variant of Tyrosine Kinase 2 (TYK2) Protects ß-Cells from Autoimmunity

Type 1 diabetes (T1D) is a complex autoimmune disease where genes and environmental factors impact pathogenesis. Analysis of the >150 loci identified by GWAS reveals the compelling theme that candidate genes cluster into pathways. A pathway connecting environment to T1D genetics is the anti-viral/Type 1 interferon (IFN1) pathway that is regulated by at least 7 T1D linked loci, including Tyrosine Kinase 2 (TYK2) which regulates IFN1 receptor signaling. We test the hypothesis that the T1D protective variant of TYK2 restrains signaling though the IFN1 receptor functions in β-cells reduce interactions with and killing by autoreactive, cytolytic CD8+ T lymphocytes (CTL) . These studies employed β-cells edited in the endogenous TYK2 locus with CRISPR/Cas9 to express the T1D protective TYK2^110A or common allotype, TYK2^110P. These cells were treated with Poly I:C (50ng/mL) , to see IFN1 response to an imitated viral infection. Outcomes were IFN1 production, gene expression, antigen presentation, and responses to CTL. When allotypic β-cells were treated with Poly I:C, both produced equivalent levels of IFN1. While β-cells with TYK2^110P showed increased mechanisms of antigen presentation, this pathway was attenuated in TYK2^110A β-cells (p<0.05) . These results were replicated by treating TYK2^110P and TYK2^110A IFN1 (100U/mL) , where we observed increased antigen presentation in TYK2^110P β-cells but not TYK2^110A β-cells (p<0.05) . Interestingly, prior to treatment cell surface human leukocyte antigen class I levels were reduced in TYK2^110A β-cells (p<0.01) . Studies to test the interactions of autoreactive CTL with β-cells supported our hypothesis. TYK2^110P β-cells were efficiently lysed by CTL and lysis was increased by pre-treatment of β-cells with IFN1 or PolyI:C. In stark contrast, TYK2^110A β-cells exhibited low levels of CTL-lysis and pre-treatment with IFN1 or PolyI:C did not modify lysis.

In conclusion, TYK2^110A protects β-cells from autoimmune-mediated death.