Naturally occurring DKK1-specific T cells in patients with MM. HLA-A*0201-peptide-tetramer staining showing the presence of DKK1 peptide-specific CD8⁺ T cells in the blood of 2 patients positive for HLA-A*0201 with MM. Percentages of cells are shown. Blood from a healthy donor who was HLA-A*0201⁺ was used as control.