Document Type

Dissertation

Date of Degree

2011

Degree Name

PhD (Doctor of Philosophy)

Degree In

Immunology

First Advisor

Timothy L. Ratliff

Second Advisor

Thomas S. Griffith

Abstract

Myeloid-derived suppressor cells (MDSC) are a heterogeneous population of immature myeloid cells identified in mice as Gr-1+CD11b+ cells with the ability to inhibit T cell function. MDSC are emerging as important regulators of T cell mediated immune responses. Current paradigm suggests that despite heterogeneity, all Gr-1+CD11b+ cells are suppressive when exposed to inflammatory stimuli. In vitro evaluation shows MDSC from multiple tissue sites have suppressive activity, and in vivo inhibition of MDSCenhances T cell function. However, the relative capacity of MDSC present at localized inflammatory sites or in peripheral tissues to suppress T cell responses in vivo has not been directly evaluated. Using a tissue specific acute inflammatory prostatitis model, we demonstrate that MDSC inhibition of CD8+ T-cell proliferation is restricted to the inflammatory site.Further, MDSC from inflammatory sites possess immediate capacity to inhibit T-cell function, whereas those isolated from peripheral tissues (spleens and liver) were not suppressive without activation of iNOS by exposure to IFN-_.Using two mouse models of prostate cancer, we extend these findings to thetumor micro-environment. During a chronic inflammatory response induced by tumorgrowth, we show Gr-1+CD11b+ cells from the tumor site possess immediate capacity toregulate effector T cell function whereas those from the spleen do not. In both tumormodels and in our prostatitis model, long term culture of activated T cells with splenicGr-1+CD11b+ cells converted precursor cells into functional MDSC during standard in vitro suppression assays. These data highlight the importance of MDSC in the prostate, and demonstrate the function of MDSC during a localized inflammatory response isrestricted to the site of an ongoing immune responseGrowing evidence suggests that prostatitis associated with chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) is mediated in part by the loss of T cell and B cell tolerance to prostate antigens. Clinical data demonstrates the presence of T cell proliferative responses to prostate auto-antigens in CP/CPPS patients. However, the mechanisms leading to this loss of tolerance are not clearly understood, largely because of a lack of available animal models. We report the development of a new mouse model for the study of chronic prostate inflammation (CPI), the Prostate Ovalbumin Expressing Transgenic-3 (POET-3) model. Adoptive transfer of antigen specific OT-I T cells induces CPI characterized by infiltration of exogenous (OT-I) and endogenous T cells into the prostate persisting as long as 45 days after transfer. In vitro and in vivo data demonstrate inflammation induced loss of T cell tolerance to prostate auto-antigens. Auto-antibody responses to prostate antigens were detected in POET-3 mice after induction of CPI. These data have important therapeutic implications for treatment of CPI.

Keywords

Arginase I, CD8 T cell, inducible nitric oxide synthase, Myeloid-derived suppressor cell, Prostate inflammation

Pages

2, xii, 176 pages

Bibliography

Includes bibliographical references (pages 162-176).

Copyright

Copyright 2011 Jessica M. Haverkamp

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