CD8A and neoplasm: Figure 4d demonstrates that tumors that grew back still expressed the Mam-A antigen. Additionally, we show that tumor cell lines derived from animals where tumors had previously grown back were equally capable of regressing as compared to the original Mam-A+ tumor cell line (Fig. 4e). Together these results indicate that loss of tumor antigen is not responsible for tumor outgrowth. Moreover, with the transfer of whole splenocytes antigen-specific CD8 T cells as well as regulatory T cells (CD4+CD25+ T cells) are introduced into the tumor-bearing host.