Work done in many laboratories has demonstrated that Ag stimulation of na?ve CD8 T cells can lead to different outcomes: development into effector cells and/or memory cells after immunogenic stimulation, and either activation and deletion or anergy in relation to Ag-specific tolerance. These distinct outcomes depend on the nature and maturation state of the Ag presenting cell, the relationship of the Ag to self, and the influence of other cell types and molecules within the lymphoid organ where activation takes place. Because these difference influences may operate in conjunction with one another in the course of an immune response, we refer to them collectively in this application as """"""""the quality of presented Ag"""""""". Over the course of the previous funding period, we have been concerned with 3 different aspects of CD8 T cell activation that are relevant to tumor immunity: 1) deletional tolerance of CD8 T cells that occurs in response to a melanoma Ag derived from tyrosinase (Tyr369) that is also expressed on normal melanocytes;2) CD8 T cell activation in the LN that drain established tumors;and 3) the response of CD8 T cells in different lymph nodes (LN) activated by peptide- pulsed dendritic cells. We have shown that self-tolerance to a melanocyte differentiation antigen is based on a direct presentation by lymph node (LN) resident cell, rather than either central tolerance or cross- presentation of tissue derived Ag by dendritic cells (DC). This self-tolerance results in CD8 T cell deletion, but this outcome can be mitigated by cross-presentation of the same Ag from several different sources, including tumor. We have also demonstrated that immunization with peptide-pulsed DC results in primary immune responses that are localized to individual LN, resulting in differences in homing receptor expression, followed by systemic redistribution. However, the route of immunization also determines the ability of memory cells to control tumors growing in different locations, suggesting that homing receptor programming is an important determinant of the effectiveness of active immunotherapy. These two important sets of observations serve as the basis for this renewal application.
The specific aims of this proposal are: 1) To determine the basis for tumor control and long-term persistence of na?ve, tolerance-prone Tyr369-specific T cells after adoptive transfer into early-stage tumor bearing mice, and mechanisms to enhance it;and 2) To determine how the quality of presented Ag and its localization to different lymphoid compartments influences the homing characteristics of CD8 T cells and their ability to control tumors growing in different locations in the body.
Cancer therapies based on stimulating the patient's immune system represent an important treatment modality, but much remains to be discovered to optimize their use. The investigators have developed model systems that allow them to evaluate two factors that may limit the success of anti-tumor immune responses: deletion of T lymphocytes reactive with self-antigens that are also expressed on tumors, and the programming of activated T lymphocytes to home to tumors growing in different parts of the body. These models will allow the investigators to also address mechanisms by which these limitations may be overcome. Success of the work may offer insights into improving immunotherapy approaches for treating cancer patients.
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