THE EFFECTS OF CHORIOALLANTOIC TRANSPLANTS OF ADULT CHICKEN TISSUES ON HOMOLOGOUS TISSUES OF THE HOST CHICK EMBRYO

Abstract

Transplants of liver and spleen were made from adult chickens to the chorioallantoic membrane of eggs, incubated for 9 days. Sham operations and transplants, using inactivated adult chicken spleens were performed as controls. The grafts were recovered after 8 additional days of incubation and studied histologically. Spleens of the host embryos were removed and analyzed for total and non-protein nitrogen (NPN). The mean weight of the host spleen, stimulated by grafts of homologous tissue was approximately four times that of the controls. The total N content was also increased, but the NPN content was not significantly different indicating that the increased weight of host spleens resulted from an increased protein content. In order to determine whether the host spleen becomes enlarged through a transfer of tissue-specific molecules from the transplant to the homologous host tissue, S35-labeled tissues were obtained by injecting 175 [mu]c/kg of S35 -labeled L-methionine into adult chickens and 225 [mu]c/kg into adult white mice. Spleen and kidney samples from these donors were weighed and then grafted to the chorioallantoic membranes of 9-day-old chick embryo hosts. Following 3 or 5 days of incubation, one-fifth of the grafts together with the homologous host organ, were fixed for histologic and radioautographic analysis. The specific activity of the radiosulfur of the protein and non-protein fractions of all the other donor and host tissues was determined. The results from 902 transplants and injected eggs indicated a highly selective transfer of radioactivity from proteins of labeled spleen and labeled kidney grafts to homologous host tissue. There was no indication of selective incorporation into the chick tissues of radioactivity from transplants of mouse spleen. In other tests, S35 -labeled methionine was injected into the yolk sac of 363 9-day-old embryos following transplants of non-radioactive spleen or sham operations. Although the host spleens were enlarged in the former group, the specific activities in the tissues of the 2 groups did not differ significantly, indicating that tissue-specific components from the transplant were involved in enlargement of host tissue. Histologic examinations of stimulated host kidneys and determination of DNA content in stimulated host spleens supported the assumption that the selective transfer of substance from graft to host tissue involves tissue-specific proteins or specific components of protein molecules larger than amino acids, rather than whole cells. The results obtained in these experiments are discussed with respect to problems of protein biosynthesis, differentiation and growth.