SIGNAL-TRANSDUCTION BY IGG RECEPTORS INDUCES CALCIUM MOBILIZATION, BUT NOT HISTAMINE-RELEASE, IN THE HUMAN BASOPHILIC CELL-LINE KU812F

Human blood basophils selectively express Fc gamma RII (CDw32) among I gG receptor subtypes, but its functional role in allergic reactions re mains unknown. Using the human basophilic leukemia cell line KU812F as a model system, we investigated cellular signaling events mediated th rough IgG receptor stimulation. KU812F cells express Fc gamma RII on t heir surface. mRNAs for both Fc gamma RIIA and IIB subtypes were detec ted by reverse transcriptase-PCR analysis. In this cell line, Fc gamma RII stimulation induced mobilization of free intracellular calcium an d actin polymerization. Yet, no significant histamine release was obse rved, nor did blood basophils stimulated by anti-Fc gamma RII monoclon al antibody IV.3 and by a secondary antibody release histamine. These data indicate that Fc gamma RII stimulation induces cellular signaling events such as calcium mobilization in human basophils. However, thes e events do not lead to histamine release.