Second-set allograft responses in the earthworm Lumbricus terrestris. Kinetics and characteristics

Second-set Lumbricus terrestris allografts from the same donor to the same recipient undergo accelerated rejection if transplanted less than 10 days after first-set allografts. In contrast, second-set allografts, transplanted at longer intervals (20-90 days) show no accelerated rejection. Accelerated rejection of allotransplants under these kinetic conditions agrees with earlier intrafamilial xenotransplant results obtained in earthworms affirming an essential experimental variable: the time of second-set transplantation. Accelerated rejection, weak specificity, and short-term "memory" are three characteristics of the earthworm's allogeneic cellular defense/immune system. These reactions probably result from intense responses (although of short duration) of coelomocytes activated by first transplants that are still present at the time of second-set grafting but absent or inactive at later periods.