The observed differences could have several causes. Thus, NTAL could play different roles in mast cells of different origin. It has been shown that human mast cells differ from mouse mast cells in cytokine production, immunoglobulin receptor expression, and the ability of different stimuli to cause degranulation and release of mediators. Furthermore, when total tyrosine phosphorylated proteins were compared between RBL-2H3 cells and freshly isolated peritoneal and pleural rat mast cells, dramatic differences were observed. These differences could reflect tumor origin of RBL-2H3 cells and could be responsible for the observed properties of NTAL. Berbamine Importantly, mouse and human mast cells were Morroniside obtained after differentiation under different cell culture conditions, which could modify their responsiveness. Mouse BMMCs were obtained by culturing bone marrow precursors in the presence of IL-3 and SCF or IL-3 alone, whereas human mast cells were derived from CD34+ pluripotent peripheral blood progenitors cultured in the presence of human SCF, IL-6 and IL-3. Previous study showed that differentiation of mast cells from their precursors in the presence of various cytokines could result in different responsiveness of the cells to various activators. Finally, one cannot exclude the possibility that silencing vectors used for NTAL KD in human and/or RBL-2H3 mast cells exhibited off-target effects, which modified responsiveness of the cells to FceRI triggering. To clarify the role of NTAL in FceRI signaling and to find out whether absence or decreased expression of NTAL has any effect on transcriptional regulation of genes, we compared under thoroughly controlled conditions RNA expression profiles of resting and Ag-activated BMMCs with NTAL KO or KD and the corresponding controls. We found that number of genes were up- or down-regulated, in BMMCs with NTAL KO or KD when compared to WT cells; most of the genes were not related to known immunoreceptor signaling pathways. The exact mechanisms and pathways through which NTAL causes changes in transcription of these genes remains to be determined.