Regeneration of heterotopically transplanted autologous splenic tissue

Normal young pigs were splenectomized and thin slices of autologous splenic tissue grafted in pouches of the large omentum and underneath the fascia of the abdominal muscles. The regeneration of the transplanted splenic fragments was studied histologically. Within the first few days, the grafts underwent almost complete necrosis. After 14 days no signs of regeneration could be seen. All typical structures of splenic tissue could be found after 3 months but the red and white pulp were populated to a lesser extent than normal with lymphoid cells. After 6 months and 12 days after i.v. injection of sheep red blood cells, the number of follicles increased dramatically and all the morphological signs of an immune response could be seen. After heterotopic transplantation in young pigs splenic fragments regenerate to small splenules of normal appearance. The regeneration is less rapid and results in smaller masses of tissue than in rodents.