Original magnification × 420. Antigen-positive cells appear in red. In Figs 1D, 3C, and 3D, nuclei are counterstained in blue (DAPI; Oncor). Chromosome-specific hybridization signals are seen as green dots in simple and as green and blue dots in double hybridization experiments. (A) Mixed lymphoid chimerism in patient no. 2. Two CD3⁺ cells are XX, one is XY. CD3⁻ cells are XY in relapse. X, green dot; Y, blue dot. (B) Male CD15⁺ cells at relapse in patient no. 2. X, green dot. (C) One female CD15⁺ cell (XX) within male CD15⁺ cells (XY) at week 6 after DLI in patient no. 2. X, green dot; Y, blue dot. (D) CD15⁺ and CD15⁻cells are all XX at week 17 after DLI in patient no. 2. X, green dot.