Target‐Effector Interaction in the Natural Killer Cell System

These results show that two subpopulations of target‐binding cells (TBC) can be detected in the lymphoid organs of normal, nonimmunized mice. One cell type is not adherent to nylon wool columns and binds selectively to a large number of tumour cell targets which are susceptible to lysis by the natural killer (NK) cell. The rise and fall in the frequency of these nylon nonadherent TBC, with age, closely parallels the NK cell activity in these mice. Nylon nonadherent TBC were specific since they could be inhibited by subcellular sonicates of sensitive targets but not insensitive targets. The presence of these TBC in nude mice and their ability to pass through nylon wool columns is compatible with the suggestion that, like the NK cell, they may not be mature T cells, macrophages or B cells and hence represent a distinct but not yet defined subpopulation of lymphocytes. The genes controlling the frequency of TBC are inherited in a dominant fashion and are linked to the H‐2 region. The strong correlation between the frequency of TBC in a population and the level of lysis provides strong indirect evidence that the TBC may represent, or be closely related to, the NK cell. In contrast, the second cell type(s), a nylon‐adherent population, was not subject to any detectable genetic control and bound to targets nonspecifically. Furthermore, these nylon‐adherent TBC differed from nylon‐nonadherent TBC in their lack of correlation with lysis, age variations and organ distribution. We believe these observations provide the basis for the eventual understanding of the target structures and receptors involved in the NK cell system.