Tyramide IHC and XY FISH show that male donor cells express IBA1. Representative images from tyramide IBA1 IHC and XY FISH of 2 separate samples (top and bottom rows). (Column 1) tyramide-based IBA1 IHC (green); (column 2) same sections after XY FISH; (column 3) digital overlap of IHC and FISH images. Arrows indicate donor cells. Donor cells are present in both amoeboid (yellow arrow; top) and ramified (red arrow, bottom) forms, with a lower expression of IBA1 in ramified cells. Green, IBA1 IHC; red probe, Y chromosome; green probe, X chromosome; blue, DAPI-stained nuclei. Images taken at original magnification ×400; scale bar, 4 μm.