CELL-MEDIATED-IMMUNITY TO A TRANSPLANTABLE SARCOMA IN RATS

The transplantable SR-RSV induced sarcoma in rats tends to spontaneous regression in part of the recepients. Host mononuclear and polynuclea r cells emerge in the tumour on day 10 after the transplantation. The tumour in the process of regression forms a capsule. The tumour tissue under the capsule is infiltrated to a varying degree with leukocytes, mainly lymphocytes. Sometimes the leukocyte number is quite large and they form belt-like surroundings as of a bank. Under this layer in so me regressing tumours giant cells of the Langhans type are seen arrang ed close to one another as in a necklace. Lymphocytes isolated from th e regressing and from the progressively growing tumours display a weak er specific cytotoxic activity as compared to lymphocytes from spleens of the same animals towards syngeneic tumour cells. The infiltration of the transplantable tumour with leukocytes (lymphocytes, macrophages and polymorphonuclears) and the demonstration of cytotoxic activity o f TIL no matter how insignificant it may be, is a proof of the immune response of the organism to the tumour.