Training Plan: The clonal deletion of autoreactive thymocytes (negative selection) results from the induction of programmed cell death or apoptosis. This process is important for achieving tolerance within an individual. While loss of self-tolerance may result in autoimmune disease, the induction of tolerance to alloantigens may result in permanent organ graft acceptance. Recent studies suggest that thromboxane A2 (TxA2) produced in the thymic microenvironment may regulate thymic maturation. Thromboxane synthase, the final catalytic enzyme involved in TxA2 synthesis, is expressed within the thymus. Moreover, the thymus expresses high levels of the thromboxane receptor (TxR), far above that of other tissues tested. Finally, TxR expression has been localized to immature thymocytes and exposure of these cells to TxA2 induces apoptosis. Therefore, the hypothesis is that TxA2 binds to its receptor and, through specific signaling pathways, regulates cellular processes important to T cell maturation and selection. The goals of this project are to identify the biochemical characteristics and ontogeny of the TxR in thymocytes and identify the function of TxA2 in thymocyte development. To investigate this hypothesis, three specific aims are proposed: (1) To characterize the signal transduction pathways coupled to the TxR in thymocytes. In these studies, the signal transduction pathways coupled to the TxR in freshly isolated thymocytes will be identified by microphysiometry and active second messenger coupling confirmed by standard biochemical assays. (2) To identify which signals activated by TxR cause apoptosis in thymocytes. These studies will directly determine which of the second messengers (identified in specific aim I) mediate apoptosis of thymocytes in vitro. (3) To define the effects of TxA2 on thymocyte maturation in vitro. Using fetal thymic organ culture as a model of thymic development, the applicant will directly test the role of TxA2 in influencing the development of T cells. T cell receptor transgenic mice will be used to specifically examine the role of TxA2 in controlling negative selection of autoreactive T cell precursors. This project is expected to provide novel information regarding the expression and function of the TxR in thymocytes and the effective role of TxA2 in regulating T cell maturation. It is hoped that understanding of the role of lipid mediators in the thymic development may suggest new strategies in preventing autoimmune disease and in the induction of transplantation tolerance to organ allografts.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Clinical Investigator Award (CIA) (K08)
Project #
5K08AI001389-04
Application #
2886027
Study Section
Allergy & Clinical Immunology-1 (AITC)
Program Officer
Prograis, Lawrence J
Project Start
1996-04-01
Project End
2001-03-31
Budget Start
1999-04-01
Budget End
2000-03-31
Support Year
4
Fiscal Year
1999
Total Cost
Indirect Cost
Name
Duke University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
071723621
City
Durham
State
NC
Country
United States
Zip Code
27705
Franceschini, Nora; Cheng, Orlena; Zhang, Xiaojie et al. (2003) Inhibition of prolyl-4-hydroxylase ameliorates chronic rejection of mouse kidney allografts. Am J Transplant 3:396-402
Mannon, Roslyn B; Griffiths, Robert; Ruiz, Phillip et al. (2002) Absence of donor MHC antigen expression ameliorates chronic kidney allograft rejection. Kidney Int 62:290-300
Mannon, R B; Nataraj, C; Pisetsky, D S (2000) Stimulation of thymocyte proliferation by phosphorothioate DNA oligonucleotides. Cell Immunol 201:14-21
Mannon, R B; Doyle, C; Griffiths, R et al. (2000) Altered intragraft immune responses and improved renal function in MHC class II-deficient mouse kidney allografts. Transplantation 69:2137-43
Mannon, R B; Coffman, T M (1999) Gene targeting: applications in transplantation research. Kidney Int 56:18-27
Mannon, R B; Kopp, J B; Ruiz, P et al. (1999) Chronic rejection of mouse kidney allografts. Kidney Int 55:1935-44
Mannon, R B; Roberts, K; Ruiz, P et al. (1999) Inducible nitric oxide synthase promotes cytokine expression in cardiac allografts but is not required for efficient rejection. J Heart Lung Transplant 18:819-27
Mannon, R B; Kotzin, B L; Nataraj, C et al. (1998) Downregulation of T cell receptor expression by CD8(+) lymphocytes in kidney allografts. J Clin Invest 101:2517-27
Mannon, R B; Coffman, T M; Mannon, P J (1996) Distribution of binding sites for thromboxane A2 in the mouse kidney. Am J Physiol 271:F1131-8