SPLENIC INVOLVEMENT IN AMPHIBIAN TRANSPLANTATION IMMUNITY

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Abstract
The spleen was identified as a center of alloimmune reactivity in control Xenopus. Levels of 3H thymidine labeling and pyroninophilic cells are elevated in spleens of skin-allografted toadlets when compared with autografted and nongrafted animals. Second-set alloimmune reactivity can be transferred by implanting a spleen from a donor that has rejected 1 or 2 grafts into a nonsensitized host. Spleen donor and host in these experiments were mutually tolerant, following reciprocal transfer of embryonic tissue grafts. In contrast, studies on the uptake of 3H thymidine and levels of pyroninophilia in animals thymectomized at 7 or 8 days of age suggest lack of splenic involvement in the chronic first-set allograft rejection that can still occur in the absence of the thymus. The lymphoid organ origin of thymic-independent alloimmunity still awaits clarification.