Heterotopic autologous splenic grafts in rat. Morphological studies.

Splenic grafts autotransplanted at splenectomy into the omentum of 23 Porton strain rats were compared with spleens from 10 sham-operated controls. Six months after transplantation, the grafts weighed between 81 to 545 mg (median 166 mg) compared to control spleens which weighed 775 to 1,250 mg (median 995 g). Histoquantitation of the grafts revealed marked reduction of the splenic white pulp when compared to control spleens. Morphological examination showed not only a reduction of lymphocytes but also a striking architectural abnormality in all grafts. In 2 of the transplants, no lymphoid aggregates were observed; small subcapsular collections were present in 7, while in 8, isolated perivascular aggregates of lymphocytes with poorly formed marginal zones were observed. Only 6 transplanted spleens showed linkage of adjacent lymphoid aggregates but the number and size of these aggregates were clearly less than normal. These findings indicate that autotransplanted splenic tissue in rats does not regain histological normality. The implications of these observations for autotransplantation in splenectomized patients are discussed.