The studies described in this thesis focus on the feasibility of using carcinoembryonic antigen (CEA) as a target for immunotherapy of colorectal cancer and on the balance between anti-tumor... Show moreThe studies described in this thesis focus on the feasibility of using carcinoembryonic antigen (CEA) as a target for immunotherapy of colorectal cancer and on the balance between anti-tumor immunity and autoimmune pathology. The potential of CEA as a target antigen for immunotherapy of cancer is conceivably restricted by the fact that CEA is expressed in several abundant and vital tissues, including intestine and stomach, and is even routinely found in the serum of healthy individuals. We demonstrate that the CEA-specific CD4+ T-cell repertoire in CEA-tg mice is severely limited compared to wild-type mice and that this CD4+ T-cell tolerance for CEA was induced by the thymus. In addition we showed that CEA was expressed in medullary thymic epithelial cells (mTEC) in both mice and human beings. The latter suggests that the CEA-specific T-cell repertoire may also be tolerized in people. In further studies we have focussed on possibilities to overcome tolerance of CEA by reconstituting the T-cell repertoire of CEA-tg mice by adoptive transfer of the T-cell repertoire of CEA-immunized wild-type mice into tumor-bearing CEA-tg mice. Adoptive transfer in combination with immune modulation can result in efficient eradication of CEA-positive tumors. However, in order to prevent hazardous CEA-specific autoimmune reactions, the choice of the right immune modulation protocol is critical. Show less
