Naturally occurring CD4+CD25+ T regulatory cells (Treg) play important roles in maintaining immunologic self-tolerance in addition to controlling the magnitude of anti-microbial immune responses. However, the capacity of these CD4+CD25+ Treg cells to control immune responses both in vivo and in vitro is not well established. CD4+CD25+ Treg cell-mediated suppression can control autoimmune diseases; transplantation tolerance and graft verses host disease and, in contrast hinder tumor immunity and immunity to infectious agents. As Treg cells have been reported to be involved in several diseases, this study focused on molecular characteristics that enables them to maintain anergy and also resistance to programmed cell death along with the effect of FIV-infection on regulation of the above phenotypic characteristics. Our results show that feline CD4+CD25+ Treg cells are phenotypically and functionally anergic as indicated by elevated levels of the cyclin dependent kinase inhibitors, CdkI¡¦s, (p21cip1,p16ink4, and p27kip1) , and resistance to mitogen-induced proliferation compared to their counter parts CD4+CD25- T cells. Importantly, CdkI¡¦s are constitutively over-expressed only in FIV-infected cats. As expected Treg cells from FIV-infected cats that over-expressed CdkI¡¦s expressed low levels of the cyclins (mainly cyclins D) and phosphorylated retinoblastoma protein (pRb) that are responsible for cell cycle progression. We investigated the role of TGF?Ò signaling and found that TGF?Ò1 plus ConA stimulation was able to convert CD4+CD25- T cells to CD4+CD25+ T cells with functional and phenotypic characteristics including upregulation of CdkI¡¦s and bcl-2. The differential expression of CdkI¡¦s and bcl-2 between the two CD4+ T cell subsets may be linked to TGF?Ò-Smad pathway. Consistent with upregulation of CdkI¡¦s and bcl-2, we found that although natural and TGF?Ò1 converted CD4+CD25+ Treg cells are anergic, they are more resistant to activation induced cell death compared to CD4+CD25- T cells functionally which correlated with increased bcl-2 to bax ratio in Treg cells. Thus, the molecular characterization of this unique population of Treg cells may be essential for understanding their role and function for developing effective therapeutics and vaccination especially against chronic infections such as Acquired Immune Deficiency Syndrome (AIDS).
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-01192006-105756 |
| Date | 24 January 2006 |
| Creators | Emani, Sirisha |
| Contributors | Dr. Mary Tompkins, Dr. Barbara Sherry, Dr. Wayne Tompkins, Dr. Frederick Fuller |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-01192006-105756/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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