Afferent sensitization and efferent cytotoxicity in allogeneic tissue responses of the marine sponge Callyspongia diffusa.

Allogeneic branches of the marine sponge Callyspongia diffusa were paired either in parabiosis or as allografts. To examine the specificity of the allogeneic rejection process, naive second sets and third parties were substituted in the midst of primary allogeneic tissue responses. Other experiments were conducted with 0.2-, 0.8-, 3.0-, and 5.0-micron pore size membrane barriers separating various combinations of naive and presensitized allogeneic paired sponges. The results of these experiments demonstrate that both the afferent and efferent phases of allograft rejection in Callyspongia diffusa depend on direct allogeneic cell contact. Cytotoxic reactivity does not involve a readily diffusible cytotoxic molecule. Moreover, the specificity of allogeneic sponge graft rejections resides in the early recognition or afferent phase; once the effector response is generated or turned on, subsequent allogeneic cytotoxicity is nonspecific.