The late endosomal/lysosomal enzyme cathepsin D localized to the lumen of the enlarged cytotoxic granules in CHS patient NK cells (Figure 6A) and has previously been observed to be processed and localized correctly in CHS cultured CTLs, as expected from the largely normal lysosomal function in most cell types of CHS patients (32, 43). The gene discussed is CTSD; the disease is Chediak-Higashi syndrome.