Regulatory T (Treg) cells play a critical role in the prevention of cutaneous autoimmune and inflammatory diseases, such as vitiligo, psoriasis, atopic dermatitis and systemic lupus erythematosus. T cell receptor stimulation is a major factor which determines Treg cell differentiation. Therefore, manipulations of antigen processing pathways which diminish T cell receptor ligands may be used to enhance Treg cell development and lessen autoimmune disease. GILT (gamma-interferon-inducible lysosomal thiol reductase) is a prime candidate for such manipulation, because loss of GILT diminishes the presentation of a subset of antigens on MHC class I and II. The long term objective of this project is to determine how antigen processing pathways regulate the balance between T cell-mediated immunity and self-tolerance in the skin. GILT is an enzyme in the lysosomal compartment of antigen presenting cells that is critical for efficient processing of disulfide bond- containing antigens. Our prior studies have shown that GILT is required for MHC class II-restricted presentation of tyrosinase-related protein 1 (TRP1), a clinically-relevant autoantigen in vitiligo and melanoma. We have developed a TRP1-specific T cell receptor transgenic mouse model in which skin-specific Treg cells develop and suppress vitiligo. We hypothesize that the loss of GILT increases peripheral induction of Treg cells that home to the skin and control cutaneous autoimmune responses. In the current proposal we will employ a unique set of genetic and immunological tools to determine the etiology of increased Treg cells in the absence of GILT by investigating whether there is increased intrathymic Treg cell development, peripheral induction of Treg cells, or proliferation of Treg cells in the periphery. We will identify the factors that lad to increased Treg cells in the absence of GILT. We will evaluate the role of GILT in Treg cell differentiation of polyclonal T cells and prevention of cutaneous autoimmunity to demonstrate the clinical significance and broad applicability of altered antigen presentation in Treg cell development. We will determine the location where TRP1-specific T cells are required to prevent vitiligo. The impact of these studies is to increase our knowledge of factors that regulate the development and function of skin-specific Treg cells and to determine how alterations in antigen processing affect the development and function of autoreactive Treg cells. In turn, this knowledge has the potential to yield novel targets (such as GILT) to promote Treg cell differentiation and control autoimmunity. Since the effect of GILT is not limited to the presentation of TRP1 or cutaneous autoantigens, modulation of GILT expression or activity may be a broadly applied therapeutic approach for autoimmune disease.

Public Health Relevance

Regulatory T cells play a critical role in the prevention of cutaneous autoimmune and inflammatory diseases, such as vitiligo, psoriasis, atopic dermatitis and systemic lupus erythematosus. These illnesses affect approximately 19 million people in the United States. In the proposed studies, we will investigate how modulation of antigen processing pathways affects the development and function of regulatory T cells. This work will identify factors that enhance the development of skin-specific regulatory T cells and determine the site where regulatory T cells control cutaneous autoimmune responses, and thus facilitate development of novel therapeutic approaches for autoimmune disease.

National Institute of Health (NIH)
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Small Research Grants (R03)
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Special Emphasis Panel (ZAR1)
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Cibotti, Ricardo
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University of Arizona
Other Basic Sciences
Schools of Medicine
United States
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Hastings, K Taraszka; Elizalde, Diana; Muppana, Leela et al. (2017) Nab2 maintains thymus cellularity with aging and stress. Mol Immunol 85:185-195
Nguyen, Jennifer; Bernert, Richard; In, Kevin et al. (2016) Gamma-interferon-inducible lysosomal thiol reductase is upregulated in human melanoma. Melanoma Res 26:125-37
Rausch, Matthew P; Hastings, Karen Taraszka (2015) An exhaustion-like phenotype constrains the activity of CD4+ T cells specific for a self and melanoma antigen. PLoS One 10:e0123332
Rausch, Matthew P; Hastings, Karen Taraszka (2015) Diverse cellular and organismal functions of the lysosomal thiol reductase GILT. Mol Immunol 68:124-8
Hastings, Karen Taraszka (2013) GILT: Shaping the MHC Class II-Restricted Peptidome and CD4(+) T Cell-Mediated Immunity. Front Immunol 4:429
Phipps-Yonas, Hannah; Cui, Haiyan; Sebastiao, Noemi et al. (2013) Low GILT Expression is Associated with Poor Patient Survival in Diffuse Large B-Cell Lymphoma. Front Immunol 4:425
Phipps-Yonas, Hannah; Semik, Vikki; Hastings, Karen Taraszka (2013) GILT expression in B cells diminishes cathepsin S steady-state protein expression and activity. Eur J Immunol 43:65-74