Chronic skin allograft rejection in terrestrial slugs

To know whether or not molluscs are capable of recognizing tissue alloantig ens, dorsal skin-allografts were exchanged between adult terrestrial slug, Incilaria fruhstorferi. We succeeded for the first time in orthotopic trans plantation of allografts and observed chronic rejection of allografts. Duri ng the first two weeks after transplantation (WAT), in all grafts, both for eign (allo-) and self (auto-), many macrophages infiltrated from the host t oward the grafts. This phenomenon is seemed to heal wounds. In the case of autografts, many macrophages observed in the grafted site until 8 weeks, wh ereas at 4 WAT, grafted tissues such as muscle fibers and mucous cells begu n to regenerate slowly and the regeneration of these cells had been over at 20 WAT. However, in the case of allografts, regenerative phenomena were no t observed, rather than muscle fibers had been actively attacked by macroph ages. Numerous macrophages which phagocytosed cell debris were observed in host connective tissues during this experiment. These observations strongly suggest that an allorecognition system is present in molluscs, and in the case of terrestrial slugs dorsal skin transplantation is a useful assay sys tem for analyses of immunological incompatibility.