Putative Immunological Influence Upon Amphibian Forelimb Regeneration. II. Effects of X-Irradiation on Regeneration...

Influence of the immune system on epimorphic regeneration of amphibian limbs has been suggested but not proved. The present investigation explored this hypothesis by examining the effects of x-irradiation on forelimb regeneration and rejection of skin allografts. Two kRad x-irradiation was provided either to a single limb or as whole-body irradiation to intact newts (with 1 limb shielded). Complete suppression of regeneration was observed when limbs to be amputated were irradiated directly. In addition, irradiated limbs displayed severe and protracted inflammation, with total resorption of the affected limbs in 85% of the cases. Moreover, delays in both the rate of forelimb regeneration and allograft rejection were found in animals receiving whole-body irradiation. However, in these cases neither forelimb regeneration nor allograft rejection were suppressed. These observations diffuse the challenge raised by irradiation studies to the notion of possible immunological influence on epimorphic regeneration. Moreover, the delays observed in both regeneration rate and allograft rejection following whole-body irradiation are consistent with possible interaction between the immune system and the regenerating limb. Nevertheless, confirmation that such interaction occurs and is integral to epimorphic regeneration must await further investigations.