WT1 and neoplasm: The frequencies of WT1-specific CD8+ T cells in tumor infiltrating CD8+ T cells were 0.32% and 8.8% on average in tumors of mice treated with the WT1 CTL peptide vaccine alone or with the combination vaccine of WT1 CTL and helper peptides, respectively, and thus were approximately 27 times higher in the latter than in the former.