Kidney biopsy.

 Histology (A-B) and immunohistochemistry and FISH (C-D). (A-B) Hematoxylin and eosin silver staining, showing the characteristics of thrombotic microangiopathy. (A) Reduced vascular lumen (*) of arteriole next to a glomerulus with reduced capillary lumina and ischaemic winding of some basement membranes. (B) Renal arteriole with a reduced vascular lumen (*) and mucoid intima degeneration. (C-D) The participation of male donor bone marrow cells in vascular endothelial repair and maintenance in a female kidney. Endothelial cells are stained with Ulex Europaeus TRITC, and the green dots in the blue nuclei (DAPI) are FISH-stained Y chromosomes. (C) Vessel (*) with male endothelial cell (arrow). (D) Vessel (*) with male endothelial cell (arrow) and a circulating male cell (arrowhead). Original magnification A, × 630; B-D, × 1000.