Increase in histamine content and enhancement of high affinity IgE receptor FcepsilonRI expression in the human leukemia KU812 cells upon treatment with hydrocortisone.

Hydrocortisone was investigated for its ability todifferentiate human leukemia KU812 cells into maturehematopoietic cells including basophils. Hydrocortisonetreatment increased the amount of intracellular histamine byup-regulation of L-histidine decarboxylase (HDC) mRNA andenhanced cell surface expression of the high affinity IgEreceptor FcepsilonRI. Histamine is catalyzed from L-histidine byHDC, which in blood cell types is only expressed in basophilsand mast cells. Cells, on which the FcepsilonRI expression wasenhanced by hydrocortisone, were shown to release histaminewhen stimulated with anti-IgE antibody after sensitizationwith myeloma IgE, implying that the induced FcepsilonRI moleculeswere able to transduce a signal for degranulation. Theseresults suggest that hydrocortisone promotes differentiationof KU812 cells into functionally mature basophilic cells.