The "lazy" NK cells of Chediak-Higashi syndrome.

Natural killer (NK) function, measured in a short-term (4-hr) 51Cr-release assay, is profoundly depressed in circulating PBL of donors with Chediak-Higashi syndrome (CHS). In this study, we demonstrate that CHS NK cells can express relatively normal lytic function after prolonged exposure in vitro to high levels of activating as well as cytotoxic stimuli. After activation with the human cloned interferon (B1) for 24 hr, CHS NK cells have lytic activity comparable to unactivated normals in a 4-hr 51Cr-release assay. In addition, after 5 days of activation with mitomycin C-treated B cell lines, CHS NK cells have levels of activity similar to those of activated normals but are defective in generating cytotoxic cells capable of lysing the stimulator B cell. Even though CHS NK cells are defective in a 4-hr 51Cr-release assay, after 16 hr they enhance their killing capability 200 to 400-fold. In fact, after 16 hr of interaction with K562 target cells, CHS NK cells are capable of releasing NK soluble cytotoxic factors. These results are consistent with the hypothesis that CHS NK cells have all the necessary cellular structures and molecules required for them to function as lytic effector cells, but their lack of cytotoxic function is due to a relative refractoriness in initiating the post-binding lytic mechanism.