Effects of ablative HCT on the liver and spleen. Characteristic histology analysis of irradiated and or transplanted axolotl. The examples shown are from recipients of both spleen and liver cells, but the results are similar in spleen or liver only transplants. No other donor tissue transplant resulted in GFP⁺ donor cell engraftment. (A,C) H&E staining (×40) of the liver. Irradiation destroys the peripheral hematopoietic layer of the liver demarcated by the red line and “H”. The black line marks where the hematopoietic layer ends and hepatocytes begin. (B,D) H&E staining (×40) of the spleen. The tissue displays some degradation after irradiation. (E,G) H&E staining (×20) of the liver with matching direct GFP 3 weeks after irradiation and transplant. The hematopoietic peripheral layer is still present but partially ablated and shows more engraftment by donor cells than the rest of the liver. (F,H) H&E staining (×20) of the spleen with matching direct GFP 3 weeks after irradiation and transplant. Donor cells engraft all through the organ without preference as seen in the liver. (I,K) H&E staining (×20) of the liver with matching direct GFP 6 weeks after irradiation and transplant. The hematopoietic layer has been ablated and donor cells show poor engraftment without preference for the periphery. (J,L) H&E staining (×20) of the spleen with matching direct GFP 6 weeks after irradiation and transplant. There is no change in engraftment as seen in the liver. (M-N) Direct GFP section (×5) of the liver and spleen at 4 weeks after irradiation and transplant. Donor cells show some preference for engraftment near the periphery in the liver but none in the spleen and there is substantially more engraftment in the spleen.