| Veto cells are an immunoregulatory cell type that can delete CTL-p that recognize antigens on the veto cell. Deletion of responding cells by peripheral CD8+ veto cells requires both CD8 and MHC class I on the veto cells, and occurs by a process of Fas/FasL dependent induction of apoptosis in the responding cell that recognizes the veto cells. In order for veto cell therapy to be translated into a cellular therapeutic, several obstacles must be over come. First, there is only a 48-hour window of opportunity where responding T cells are susceptible to veto-based deletion. Second, large quantities of veto cells of similar specificity must be generated. Third, the characteristics of the interactions between veto cells and immunosuppressive drugs that patients may be taking concomitantly with veto therapy must be determined. Lastly, veto cells are proposed as a novel approach for inducing transgene-specific immunological tolerance. These translational issues are addressed by the work contained herein. It is demonstrated that: (1) the addition of rapamycin significantly extended the window of opportunity for veto-based deletion by preventing the responding T cells from differentiating out of a vetoable state; (2) CD8+ veto cells can be rapidly generated using artificial APCs; (3) restimulating veto cells with IL-2 produces a veto cell line with identical specificities that can be harvested on a weekly basis; (4) CsA can be used in combination with the veto cell line, but not with primary veto cells; and (5) recipient CD8+ veto cells can induce tolerance in the CTL compartment to antigens as a model for veto cell protection of products in gene replacement therapy. The findings in this dissertation further our understanding of veto cell biology as well as lay the groundwork for future translation of veto cell therapy into the clinical setting both with transplantation tolerance induction and in circumventing a major obstacle in gene replacement therapy. |
