Four-color analysis of HLA-E tetramer–positive T cells. PBMCs isolated from 4 HAM/TSP patients and 5 healthy (uninfected) controls were stained with HLA-E tetramer and with antibodies to CD3, CD8, and the γδ TCR. A representative experiment from one healthy control is shown. (A) PBMCs were stained with E tetramer and anti-CD3 mAb. HLA-E tetramer–positive CD3⁺ cells were gated (square gate). (B) Dot plot shows expression of CD8 and γδ TCR in CD3⁺ cells that were HLA-E tetramer–positive (inside square gate on panel A). Staining with a pan anti-γδ TCR mAb indicates that about 70% of HLA-E tetramer–positive/CD3⁺ cells were CD8^high- γδ T cells and almost all CD8^high+ cells were γδ^- T cells in this individual.