Inhibition of tumor and fetal tissue growth in newborn recipients.

A comparative study of growth of a variety of fetal tissues and transplantable tumors in syngeneic newborn and adult mice was carried out. Tumors used in the experiments arose spontaneously (hepatomas, mammary gland adenocarcinoma) or resulted from malignant conversion of ectopic transplants either of fetal tissues (urinary bladder carcinoma, adenocarcinoma of small intestine, stomach sarcoma) or of adult animal tissues (ovary carcinoma) in syngeneic system. The growth of "teratomas" developed after transplantation of minced tissues of 18-20-day fetuses was considerably inferior in newborn syngeneic recipients as compared to analogous transplants in adults. Inhibition of tumor growth was also observed in newborn animals. It was manifested in prolongation of latent period before tumor node appearance as well as in slowing down of growth rate of developed tumors. Only one tumor, mammary gland adenocarcinoma, proved to be an exception, its growth being equally progressive in newborn and adult recipients. At transplantation of tumor cells mixed with lymphocytes of adult mouse spleen, stimulation of tumor growth in newborns and inhibition of growth in adult recipients was observed. It is suggested that there exists a special type of cellular or humoral mechanism controlling tumor growth in newborns. The activity of such factors is conceivably based on fetal antigens as targets.