ARTICLES: PDF OnlyMETCALF D.Transplantation: May 1964 - p 387-392 Free Abstract Single 1-day-old C3H spleen grafts in adult splenectomised (AKR X C3H)F1 mice grew to a larger size and contained more lymphoid tissue than grafts in sham-operated mice. In splenectomised hosts, individual spleen grafts attained a progressively smaller size in hosts grafted with 6 and 12 spleen grafts per animal. Thus the total mass of spleen graft tissue in such animals reached a plateau which approximated the weight of the normal spleen in such animals. Similar results were obtained with AKR spleen grafts in AKR mice and with C57BL spleen grafts in (AKR X C57BL) F1 hybrid mice. In sham-operated hosts a similar tendency for a reduction in individual spleen graft size after multiple grafting was also noted. Total spleen mass appears to be under positive regulation by the body but the mechanisms involved are unknown. © Williams & Wilkins 1964. All Rights Reserved.