Basophilic differentiation of the human leukemia cell line KU812 upon treatment with interleukin-4

The human leukemia cell line KU812 had been described as an immature prebasophilic cell line and exhibits a potential to differentiate into mature basophils. We studied the effect of interleukin-4 (IL-4) on the basophilic differentiation of KU812 cells. When KU812 cells were cultured with 1 ng/ml IL-4, cellular histamine content increased more than 10-fold. IL-4 also enhanced the expression of FcεRI, a high affinity IgE receptor, on the cell surface. KU812 cells treated with IL-4 expressed higher levels of FcεRIα, FcεRIβ and FcεRIγ mRNA than non treated KU812 cells. After 21 days in culture with IL-4, KU812 cells became morphologically mature basophilic cells as demonstrated by staining positive for cytoplasmic granules and heparin proteoglycan by Wright dye and toluidin blue dye respectively. In addition, IgE-mediated histamine release was observed, suggesting that the FcεRI induced by IL-4 was functional and was able to transduce a signal for degranulation. These results suggest that IL-4 promotes differentiation of KU812 cells into mature basophilic cells both morphologically and functionally.