Murine and human interleukin 2 can substitute for the thymus in immune responses to TNP-Ficoll in Xenopus laevis, the South African clawed toad.

Extirpation of the thymuses of Xenopus laevis abrogates the capacity to respond to trinitrophenol (TNP)-Ficoll regardless of the age of the animal. This thymus requirement can be substituted for by a variety of treatments which stimulate thymus-derived (T)cell activity in the periphery, such as the rejection of allogeneic skin grafts, immunologic challenge with thymus-dependent immunogens, (e.g., heterologous erythrocytes), or plant-derived lectins (e.g., concanavalin A). Here we report that interleukin 2 (IL-2), a T-cell-produced hormone of mammalian origin also substitutes for this thymus requirement in thymectomized toads.