CD4 and neoplasm: For TSAs, peptide antigens of 25 amino acids in length are typically used wherein the middle (15th amino acid) is the mutant (ie, tumor-specific) residue.85,86 This length ensures that all 8–11 amino acid CD8+ T-cell epitopes and most 12–15 amino acid CD4+ T-cell epitopes including the mutant amino acid are represented in each sequence.