Date of Degree
MS (Master of Science)
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 MDSC enhances 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-γ.
Using two mouse models of prostate cancer, we extend these findings to the tumor micro-environment. During a chronic inflammatory response induced by tumor growth, we show Gr-1+CD11b+ cells from the tumor site possess immediate capacity to regulate effector T cell function whereas those from the spleen do not. In both tumor models and in our prostatitis model, long term culture of activated T cells with splenic Gr-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 is restricted to the site of an ongoing immune response.
Growing 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.
Copyright 2012 Jaime Ricci
Ricci, Jaime. "Investigating environmental response to Afro-Arabian flood basalt volcanism with elemental analysis of oligocene carbonate sediments from Odp Leg 115 site 709, Indian Ocean." thesis, University of Iowa, 2012.