Characteristics of transplantation immunity in the sponge, Callyspongia diffusa.

Very extensive polymorphism of histocompatibility (H) molecules in the sponge Callyspongia diffusa was revealed by the incompatibility found among 480 different allogeneic pairings without exception. This represents some 960 individual clones utilized as alloparabionts or sources of fitted allografts. Consistent cytotoxic reactivity provoked by allogeneic cell surface contact in Callyspongia is manifest in a continuum of strong to weak histoincompatibilities; however, strong reactions are most frequent at normal temperatures of 23 to 27 C. The directionality, vigor, and timing of alloparabiotic rejection in this species all depend mainly on the genetic constitutions of the interacting clones. Replicate interclonal combinations yield essentially identical rejection reactions, and differences in graft dosage had no effect on either the direction or intensity of allocytotoxicity. Alloreaction times are inversely proportional to the strength of the H barrier. Maximal allosensitization indicated by accelerated second-set reactivity was gradually achieved, as a function of the interclonal combination, after 2 to 8 days of primary contact. Heightened transplantation immunity or memory persists for at least 2 to 3 weeks after contact sensitization.