Human basophils activated through high-affinity
immunoglobulin E (
IgE) receptors (
Fc epsilon RI) are involved in the late phase of the
allergic reaction. To investigate the possible involvement of
protein-tyrosine kinases in this activation we used human
acute basophilic leukemia (ABL) cells in culture as well as a pure population of normal basophils in vitro-derived from human bone marrow precursor cells (HBMB). ABL cells were 50-80% basophils at various stages of maturation as assessed by staining, morphology, ultrastructure, and flow cytometry analysis, and only basophils in ABL cells expressed
Fc epsilon RI. Aggregation of
Fc epsilon RI by
IgE and
anti-IgE,
IgE and
antigen, or anti-
Fc epsilon RI monoclonal antibodies on ABL cells or on HBMB, led to increased
tyrosine phosphorylation of 120-, 100-, 80-, 72-, 50- to 65-, and 38-kDa substrates.
Tyrosine phosphorylations in ABL cells were in basophils because 1) they were detected after a 5-s stimulation, 2) they were observed under conditions where mediator release is minimal, i.e., in the absence of extracellular
calcium, 3)
hapten addition during
antigen stimulation resulted in almost total disappearance of
tyrosine phosphorylations within 30 s. There was correlation between histamine release and
tyrosine phosphorylation in
anti-IgE dose-responses and in dose-responses of the
tyrosine kinase inhibitor genistein. The
tyrosine kinase p72syk was detected in the cells. Stimulation of ABL cells for 1 min resulted in extracellular
calcium-independent
tyrosine phosphorylation and activation of p72syk. Therefore,
tyrosine kinases are involved in the early steps of human
Fc epsilon RI signaling in basophils.
Tyrosine kinases and their substrates could represent new potential therapeutic targets to prevent the development of the
allergic reaction.