Specific allograft reactivity in the sea star Dermasterias imbricata.

Transplantation studies with the sea star Dermasterias imbricata revealed that this echinoderm rejected most first-set allografts after prolonged chronic reactions. All control autografts remained intact and fully viable. The greatly accelerated rejection of subsequent second- and third-set allografts demonstrated that these reactions were not only highly specific, but that these animals possess at least short-term immunological memory. The specific nature of the allograft response was confirmed by the prolonged survival of unrelated third party allografts placed at the same time as second- or third-set allografts. Animals in these experiments were maintained in sea water at temperatures of 14-16 C. Since this low temperature is required for successful maintenance of this species, temperature-dependence studies could not be undertaken. The rejection reaction was characterized by loss of pigmentation, edematous swelling, and necrosis. Histologically, the allograft tissue was heavily infiltrated by lymphocyte-like cells and phagocytic cells, causing disruption of the normal cytoarchitecture of the dermis. Deposits of fibrous material were also in evidence. Autografts, on the other hand, remained fully viable with no signs of rejection. We conclude that this asteroid, a representative of the echinoderms, has a well-developed, cell-mediated immune response analogous to that of vertebrates.