Countercurrent distribution of human peripheral blood lymphocytes: isolation of a subpopulation enriched with natural killer and K cells.

Aqueous solutions of dextran and of poly(ethylene glycol) when mixed give rise to two-phase systems suitable for the separation by partitioning of cells based on subtle differences in their membrane surface properties. Human peripheral blood mononuclear cells were obtained by centrifuging blood over Hypaque-Ficoll and removing the cells from the cushion. Clean lymphocytes were then isolated by velocity sedimentation of the mononuclear cells. Lymphocytes were subjected to countercurrent distribution (i.e., a multiple extraction procedure) in a two-polymer aqueous phase system which separates cells primarily on the bases of surface charge-associated properties. It was found that a small subpopulation of cells with highest partition coefficient (presumably highest surface charge-associated properties) contain virtually all of the natural killer (NK) and K cell activities.