Expression of hPLAP in tissues of irradiated wild-type rats transplanted with bone marrow from hPLAP-tg rats [WT (hPLAP-BMT)], 4 weeks post-transplantation. FACS analysis reveals hPLAP expression (mAb clone 8B6) on peripheral blood leukocytes (A) and bone marrow cells (B) in irradiated WT (hPLAP-BMT) rats (grey area) in contrast to wild-type rats (white area). All leukocytes in lymph nodes demonstrate clear hPLAP staining (C). In cross-sections of the ileum, enterocytes and smooth muscle cells remain unstained, while cells in the submucosa and endothelial cells show intense hPLAP labeling (D). Cardiomyocytes (E) and renal tubular epithelial cells (F) are hPLAP negative cells of recipient origin, while a significant portion of capillary endothelium in heart and kidney is of donor origin as indicated by hPLAP labeling (arrows). Five-μm-thick paraffin sections of abdominal lymph node (C), ileum (D), heart (E), and kidney (F) stained for hPLAP activity and counterstained with nuclear fast red. Bar = 50 μm.