The contact of natural killer ( NK ) cells with foreign cells and with certain virus-infected or tumor cells triggers the cytolytic machinery of NK cells .
the contact of natural killer ( nk ) cells with foreign cells and with certain virus-infected or tumor cells triggers the cytolytic machinery of nk cells .
O O O B-cell_type I-cell_type I-cell_type I-cell_type I-cell_type I-cell_type O B-cell_type I-cell_type O O O O O O O O O B-other_name I-other_name O B-cell_type I-cell_type O