Studies on transplantation immunity of the yellow-bellied toad Bombina variegata

Adults and tadpoles of the yellow-bellied toad Bombina variegata reacted in a typically chronic manner to skin allografts and to xenografts from closely related fire-bellied toads B. bombina but they rejected quickly skin xenografts from evolutionary distant anuran species (Bufo and Rana). Adult individuals reacted to allografts slowly not only in the laboratory where their mating was ceased and the weight of lymphoid organs significantly diminished but also in the outdoor enclosure where they bred successfully. Breeding activity in captivity can be induced at any season by Biogonadyl injections. However, any hormonal manipulation (gonadectomy or Biogonadyl treatment) performed during winter/spring on animals housed in the laboratory for several months did not influence their transplantation immunity and the weights of thymuses and spleens. These results lead to conclusion that chronic allograft rejection was not a laboratory artifact caused by a hormonal imbalance but rather reflected a weak donor-host genetic disparity connected with the low MHC polymorphism of Bombina species.