ISSN:
1398-9995
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
specificity of IgE binding to a human basophil-like cell line (KU812) was studied by flow cytometry. Four IgE myeloma proteins, representing both light-chain types, one chimeric IgE protein, and polyclonal serum IgE blocked the direct binding of FITC-labeled IgE(DES) myeloma protein to KU812 cells in a dose-dependent and nearly equimolar way. Although not as efficiently as human IgE (from five to eight times less on a molar basis), both rat and mouse IgE blocked IgE(DES)-FITC binding to KU812 cells. In sharp contrast, all four human IgG subclasses, both IgA subclasses, and IgM myeloma proteins, as well as monomeric and heat-aggregated polyclonal human IgG, were unable to block significantly IgE(DES)-FITC binding to KU812 cells (≤0.5/0 on a molar basis). The cytophilic epitope on IgE was heat-susceptible (56 °h), lost after reduction alkylation, and resident in the papain-derived Fcɛ -fragment, but not in the papain-derived F(ab') 2ɛ.- and Fcɛ-fragments nor in the pepsin-derived F(ab')2ɛ- and Fcɛ.'-fragments. Washing and displacement experiments indicated that a major part of IgE reacted with high affinity to KU812 cells. The results indicate that the binding of IgE to KU812 cells is highly specific and involves the classical high-affinity FcɛRI-receptor. Although the density of receptors is low, this human cell line offers a unique model to study IgE/FcɛRI interactions.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1398-9995.1995.tb02485.x
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