Tetramer staining of CD8⁺ T cells specific for the NPM1^mut-derived peptides #1 and #3. The frequency of CD8⁺ T lymphocytes specifically recognizing NPM1^mut peptides #1 and #3 was assessed by counterstaining CD8 T cells with tetramers with the respective epitope peptide in an AML patient with a NPM1^mut (A). (B) Negative controls using an individual who was negative against NPM1 peptides #1 and #3 in ELISPOT analysis. IMP tetramer staining served as a positive control for the experiments shown in both A and B.