Effects of gamma-irradiation on the rejection of transplanted scale melanophores in the teleost, Oryzias latipes.

The effects of gamma-irradiation on allograft rejection in the teleost, Oryzias latipes, were examined at 25 degrees C. The survival of melanophores in the transplanted scale was observed as an index of rejection. Allografts were rejected in non-irradiated fish within 7 days. In the gamma-irradiated recipients (2kR), the grafts were rejected more slowly, but still within 20 days. The gamma-ray effects, however, disappeared almost completely within 25 days after the irradiation. If the same recipient again received transplants, the secondary response occurred clearly and the melanophores were rejected very rapidly. The secondary response was suppressed by gamma-rays if the fish was irradiated just before the second transplantation. Immunologic memory against the first transplants disappeared within 30 days, a period shorter than that of mammals.