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Self-Tolerance Does Not Restrict the CD4+ T-Helper Response against the p53 Tumor Antigen

Departments of ¹ Immunohematology and Blood Transfusion and ² Clinical Oncology, Leiden University Medical Center, Leiden, the Netherlands

Requests for reprints: Rienk Offringa, Leiden University Medical Center, Leiden, the Netherlands. E-mail: R.Offringa{at}LUMC.nl.

Key Words: Tumor antigens • Cellular immunotherapy • Immune responses to cancer

Tumorigenesis is frequently associated with mutation and overexpression of p53, which makes it an attractive target antigen for T cell–mediated immunotherapy of cancer. However, the magnitude and breadth of the p53-specific T-cell repertoire may be restricted due to the ubiquitous expression of wild-type p53 in normal somatic tissues. In view of the importance of the CD4+ T-helper cell responses in effective antitumor immunity, we have analyzed and compared the p53-specific reactivity of this T cell subset in p53+/+ and p53–/– C57Bl/6 mice. This response was found to be directed against the same three immunodominant epitopes in both mouse types. Fine-specificity, magnitude, and avidity were not affected by self-tolerance. Immunization of p53–/– and p53+/+ mice with synthetic peptide vaccines comprising the identified epitopes induced equal levels of Th1 immunity. Our findings imply that the p53-specific CD4+ T-cell repertoire is not restricted by self-tolerance and is fully available for the targeting of cancer. [Cancer Res 2008;68(3):893–900]