Heterogeneity within the population of NK and K cells.

Using a cellular immunoadsorbant technique, we have examined the relationship between the K cell, which mediates antibody-dependent cellular cytotoxicity (ADCC) and the natural killer (NK) cell. Human peripheral blood lymphocytes (PBL) were allowed to adhere to monolayers of NK-sensitive target cells. PBL nonadherent to these monolayers and control PBL were then tested for both NK and ADCC activity by using a short-term 51Cr-release assay. The cytotoxic activity of nonadherent PBL was compared to that of control PBL by using the slope rati- method. In most cases, the extent of depletion of NK was greater than that of ADCC; however, in several experiments both activities were depleted to an equivalent extent. It is concluded that a single cell can mediate both ADCC and NK and that the selectivity of a given effector cell for NK targets depends upon the particular NK recognition site(s) that the cell bears.