A role for effectors of cellular immunity in epimorphic regeneration of amphibian limbs.

Immune modulation of regeneration of amphibian appendages is suggested, but not proven, by previous studies. Earlier studies have not demonstrated effects of treatments on both epimorphic regeneration and immune responses or restoration of regeneration by specific reversal of immunomodulation. Cyclosporin A (CsA) and interleukin-2 (IL-2) were used in this study to demonstrate the effects of immune suppression and its reversal, on allograft rejection and forelimb regeneration. When administered alone, CsA suppressed rejection of skin allografts and induced a dose-dependent retardation of regeneration. IL-2, administered alone, did not affect allograft rejection or regeneration. However, when combined with CsA, IL-2 abrogated or reversed effects of CsA on both allograft rejection and forelimb regeneration, in a dose-dependent manner. The selective focus of CsA's action and the ability of IL-2 to overcome and reverse these effects strongly suggest that T-lymphocytes participate in or contribute to expression of epimorphic regeneration of amphibian appendages. Further studies are required to better characterize this role.