Depletion of NK by cellular immunoadsorption.

The binding of human natural killer (NK) cells to their tumor cell targets was investigated by using monolayers of sensitive target cell lines. Monolayers of K562 and HSB, a myeloid and T cell line, respectively, were prepared on poly-L-lysine-coated plastic tissue culture dishes and briefly fixed with 0.2% formaldehyde. Freshly isolated peripheral blood lymphocytes (PBL) were incubated on the monolayers. Nonadherent PBL were then removed, after gentle agitation, by decanting and gently washing the monolayer. They were tested, along with unseparated controls, for NK activity in a short-term 51Cr release assay. PBL that were nonadherent to a tested monolayer had only 20 to 60% of the control cytotoxic activity. Our results suggest that NK recognition sites on the effector lymphocytes were able to interact with reciprocal determinants on the target cell monolayers, resulting in selective loss of NK effector cells from the PBL population. The specificity of the NK effector-target interaction was investigated by testing the ability of each monolayer to remove activity against both targets. These data imply heterogeneity with regard to recognition structure within the NK effector population as well as among the target cells.