Life history of cells mediating natural resistance to tumor cells and bone‐marrow transplants: The respective roles of cell lineage commitment and host environment in determining strain characteristics of natural resistance to foreign marrow grafts

Abstract

A class of cells present in the blood and lymphoid tissues of mammals produces rapid cytolysis of tumor cells on first contact. Abundant evidence suggests that such natural killer (NK) cells play a role in tumor immunosurveillance in vivo. A similarly prompt and spontaneous activity can cause the rejection of foreign marrow transplants. These phenomena are known collectively as natural resistance. The cells mediating natural resistance are lymphoid in morphology, but are neither T nor B lymphocytes. Kinetically, NK cells and cells mediating natural resistance to foreign marrow grafts are themselves nondividing but are rapidly renewed from radiosensitive proliferating precursors in the bone marrow. They appear to have no long-lived (memory) component. Newly formed NK cells have a short residence time in the spleen. Other general properties of the natural-resistance cell lineage, including strain variation, ontogeny, and cell phenotype, are reviewed in this article. The present study aimed to examine the respective roles of cell lineage commitment and of the host environment in determining strain characteristics of natural resistance to foreign marrow grafts. Chimeras produced by inoculating mice of a strain that normally has little or no natural resistance with bone marrow from adult mice of a highly resistant strain develop resistance to a third-party marrow allograft. Such chimeras do not develop the full rejection capacity of the high-resistance strain, however; and chimeras created by inoculating marrow from infant mice develop less resistance than those reconstituted by bone marrow from adult mice. The results demonstrate that the ability to reject foreign marrow grafts develops as an intrinsic property of the natural-resistance cell lineage. The host environment may provide an additional influence, however, particularly in the initial development of natural resistance in early postnatal life.