label: Absent natural killer cells
label_lc: absent natural killer cells
description: "Lack of natural killer cells, a type of lymphocyte in the innate immune system that contains cytoplasmic granzymes, i.e., small granules with perforin and proteases that allow natural killer cells to form pores in the cell membrane of the target cell through which the granzymes and associated molecules can enter, inducing apoptosis."