Isolated lymphocytes can restore allograft rejection capacity of early-thymectomized Xenopus

In the clawed toad, Xenopus laevis, thymectomy at 4 days of age abrogates the allograft rejection capacity. Restoration of allograft immunity to approximately normal levels was achieved after injecting 1 × 10⁷ thymic or 2 × 10⁶ splenic lymphocytes from histocompatible toads. Lymphocytes from peripheral blood were as effective as thymocytes. The degree of restoration was dependent upon the number of injected thymocytes. Histoincompatible thymocytes were also effective in restoration, although to a lesser degree. In all restored toads, repopulation of lymphocytes was evident in the spleen.