Morphologic and Functional Study of Heterotopic Splenic Tissue Allografts in Rabbits.

OBJECTIVES To assess the viability and induction of immunotolerance of nonvascularized splenic alloimplants. The phagocytic functions of splenic implants also were studied. MATERIALS AND METHODS Thirty-six adult female New Zealand and California rabbits were used, and these animals were divided into the following 5 groups: (n = 6 / groups 1-4) group 1 (sham operations); group 2 (total splenectomy); group 3 (implantation of autologous sliced splenic tissue in the greater omentum following splenectomy); group 4 (implantation of allogenic sliced splenic tissue in the greater omentum after splenectomy); and group 5 (n = 12) (implanting allogenic sliced splenic tissue in the greater omentum after splenectomy and receiving oral cyclosporine at a dosage of 40 mg/kg/d). All animals were followed for 120 days after the operations, then received venous injections of China ink (groups 1, 2, 3, 4, 5A) or a colloidal radiopharmaceutical (group 5B), and subsequently underwent reoperations. Hematimetric examinations were performed, and the histologic aspects and phagocytic functions of the implants were assessed. RESULTS Spontaneous immunotolerance was not induced by sliced splenic allografts implanted in the greater omentum. The use of cyclosporine did not preserve the viabilities of the implants. All animals in group 3, which were subjected to autologous implants, exhibited viable implants that exhibited phagocytic function, although this phagocytic function was reduced compared with that of the normal spleen. CONCLUSIONS No viable spleen alloimplants were observed regardless of the presence of cyclosporine. Spontaneous immunotolerance was not induced by sliced splenic alloimplants.