PROLONGED SURVIVAL OF AUXILIARY SPLEEN ALLOGRAFTS IN RATS INDUCING ACCEPTANCE OF SKIN ALLOGRAFTS

Abstract

Auxiliary, heterotopic spleen allografts have been performed between two inbred rat strains using PVG (Hooded Lister) as donor and AGUS as recipient strains, across a major Ag-B histocompatibility barrier. In this strain combination spleen allografts were rejected at approximately 3 weeks and skin allografts after 7.7 ± 0.3 days. However, where the recipients were pretreated with a mixture of 5 × 10⁷ spleen cells, 5 × 10⁷ thymus cells, 3 × 10⁷ liver cells, and 1 ml of blood from the donor strain, given i.v. 8–22 days prior to spleen grafting, 72% of the grafts survived longer than 4 months. These AGUS rats bearing spleen allografts accepted subsequent skin allografts. Even after removal or late absorption of accepted spleen allografts, the rats remained tolerant to skin allografts. Pretreated rats which absorbed spleen allografts within 4 weeks after operation rejected subsequent skin allografts after 7.9 ± 0.9 days. Skin allografts on pretreated recipients which had no spleen allografts were rejected like first-set grafts.