Natural killer (HNK-1⁺) cells in Chediak-Higashi patients are present in normal numbers but are abnormal in function and morphology

Children with the Chediak-Higahi (CH) syndrome are known to have abnormalities of natural killer (NK) cell function. We used the HNK-1 monoclonal antibody that reacts specifically with human NK and K cells to distinguish whether this abnormality was due either to a numerical deficiency of NK cells or a defect in their ability to function. In eight CH patients, a significant proportion of their blood mononuclear cells (10-19%) expressed the HNK-1 differentiation antigen. The level of NK cells in the five children with CH syndrome was higher than for age-matched normal controls (15.8% vs. 5.8% P < 0.001). When HNK-1⁺ cells were isolated with a fluorescence-activated cell sorter, the NK cells from CH patients were a homogeneous population of lymphocytes with a single large granule rather than the multiple small granules seen in NK cells from normal individuals. The purified HNK-1⁺ cells from the CH patients had minimal NK or K cell function. The CH syndrome thus includes a functionally defective population of NK cells that retain the capability of expressing the HNK-1 differentiation antigen.