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

Hydrocortisone was investigated for its ability to differentiate human leukemia KU812 cells into mature hematopoietic cells including basophils. Hydrocortisone treatment increased the amount of intracellular histamine by up-regulation of L-histidine decarboxylase (HDC) mRNA and enhanced cell surface expression of the high affinity IgE receptor FcεRI. Histamine is catalyzed from L-histidine by HDC, which in blood cell types is only expressed in basophils and mast cells. Cells, on which the FcεRI expression was enhanced by hydrocortisone, were shown to release histamine when stimulated with anti-IgE antibody after sensitization with myeloma IgE, implying that the induced FcεRI molecules were able to transduce a signal for degranulation. These results suggest that hydrocortisone promotes differentiation of KU812 cells into functionally mature basophilic cells.