The observation of Miller of severe immunological deficiencies in adult, thymectomized, total-body-irradiated mice,1 led to the belief that the thymus played an essential role in reestablishing immune mechanisms in adult life. Miller2 implied that after adult thymectomy the animal becomes incapable of producing new immunologically competent cells. This deficiency results in gradual decrease in the ability of the animal to produce an immune response, provided that the noncommitted immunologically competent cells normally die and disappear in time. Adult thymectomy has been added to the recognized methods of immunosuppresion in animals and in man, in an effort to prolong the survival of allografts. The results of such efforts have been conflicting.3-10
We decided to investigate the influence of extracorporeal irradiation of blood (ECIB) and thymectomy on skin allograft survival in calves and to compare these results to those obtained with ECIB alone.11 It has been shown that