Expression of IgE receptors and histamine in cloned natural killer cell lines

Natural killer (NK) activity is mediated by large granulated lymphocytes (LGL). Recently, the relationship of NK cells to mast cells and basophils has been suggested. We therefore examined three distinct interleukin 2-dependent cloned cell lines capable of mediating NK lysis. Virtually all the cells of each line contained membrane-bound granules. Interestingly, ultrastructural studies demonstrated that the granules in each cell line were morphologically distinct and thus heterogeneous. All three cloned, granulated NK cell lines were found to variably express low numbers (less than or equal to 1.3 X 10(4)) of low affinity plasma membrane IgE receptors (Fc epsilon R). In contrast to mast cells and basophils, however, none were found to express high numbers of high affinity Fc epsilon R. In addition, none of the three NK cell lines were found to contain histaminase-sensitive histamine. Our results suggest that NK cells are not related to mast cells or basophils.