The immune system is subject to multiple layers of regulation that promote tolerance to self and that are critical for the prevention of autoimmune diseases, such as Type 1 diabetes. A key player in the maintenance of immune tolerance is the Autoimmune Regulator (Aire) gene. Aire was identified as the defective gene in the human autoimmune syndrome Autoimmune Polyglandular Syndrome Type 1, highlighting the critical importance of this gene in tolerance. Aire acts within specialized medullary thymic epithelial cells (mTECs) to promote the expression of hundreds of self-antigens for the purpose of removing developing self-reactive T cells, a process known as negative selection. Recently, we have described an additional site of Aire action within a unique population of antigen-presenting cells found in peripheral lymphoid organs that we have termed extra-thymic Aire-expressing cells (eTACs). As in mTECs, Aire acts in eTACs to promote the expression of many self-antigens that are distinct from those controlled by Aire in the thymus, suggesting a complementary role of eTACs in promoting tolerance in the periphery. Indeed, eTACs are capable of presenting self-antigens to peripheral T cells to cause deletion or functional inactivation of the self-reactive cells, thus preventing autoimmunity. Much remains unknown about this novel cell type;however, the discovery of the bone-marrow origins of eTACs opens up the potential for expansion and manipulation of this cell type for therapeutic applications in promoting self-tolerance. We have developed a powerful set of genetic tools that will allow us to define the growth and development of these cells as well as identify potentially unique pathways of peripheral tolerance induction, through comparisons with other types of antigen-presenting cells. We hypothesize that eTACs represent a unique tolerogenic population of APCs with an important role in mediating peripheral tolerance and can serve as a novel therapeutic target for tolerance induction. Therefore, our specific aims are: (1) to define and characterize the lineage and growth requirements of eTACs, (2) to define the sites and mechanisms of eTAC action, and (3) to determine how loss and gain of function in eTACs can modulate disease in models of T1D. Taken together, our studies will help determine origins of eTACs, the mechanisms by which they enforce tolerance, and how we may employ them in the prevention of Type 1 diabetes and other autoimmune diseases.

Public Health Relevance

This project is designed to further understand an important cell population in peripheral lymphoid organs, extrathymic Aire-expressing cells (eTACs), that helps promote immune tolerance to self. eTACs are capable of inactivating T cells and preventing autoimmunity, and further study is needed to better understand the origins of these cells and how they work to promote tolerance. The proposed studies will further define how these cells develop, how they prevent autoimmunity, and how we may harness these abilities to develop cell- based therapies for the potential treatment of autoimmune diseases, such as Type 1 diabetes.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
1R01DK101622-01
Application #
8672284
Study Section
Hypersensitivity, Autoimmune, and Immune-mediated Diseases Study Section (HAI)
Program Officer
Spain, Lisa M
Project Start
2014-04-02
Project End
2019-03-31
Budget Start
2014-04-02
Budget End
2015-03-31
Support Year
1
Fiscal Year
2014
Total Cost
$343,107
Indirect Cost
$125,607
Name
University of California San Francisco
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
094878337
City
San Francisco
State
CA
Country
United States
Zip Code
94143
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Malhotra, Deepali; Linehan, Jonathan L; Dileepan, Thamotharampillai et al. (2016) Tolerance is established in polyclonal CD4(+) T cells by distinct mechanisms, according to self-peptide expression patterns. Nat Immunol 17:187-95
Chan, Alice Y; Anderson, Mark S (2015) Central tolerance to self revealed by the autoimmune regulator. Ann N Y Acad Sci 1356:80-9
Bluestone, Jeffrey A; Bour-Jordan, Hélène; Cheng, Mickie et al. (2015) T cells in the control of organ-specific autoimmunity. J Clin Invest 125:2250-60
LaFlam, Taylor N; Seumois, Grégory; Miller, Corey N et al. (2015) Identification of a novel cis-regulatory element essential for immune tolerance. J Exp Med 212:1993-2002