Demonstration of specific high-affinity Fc epsilon-receptors on the human basophil-like leukemia cell line KU812 by flow cytometry.
The 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% on a molar basis). The cytophilic epitope on IgE was heat-susceptible (56 degrees C, 2 h), lost after reduction alkylation, and resident in the papain-derived Fc epsilon-fragment, but not in the papain-derived Fab epsilon- and Fc'epsilon-fragments nor in the pepsin-derived F(ab')2 epsilon- and Fc"epsilon-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 Fc epsilon RI-receptor. Although the density of receptors is low, this human cell line offers a unique model to study IgE/Fc epsilon RI interactions.
Magnusson
C G
CG
Department of Clinical Immunology, Karolinska Institute, Stockholm, Sweden.
Håård
J
J
Matsson
P
P
Karlsson
T
T
Nilsson
K
K
Johansson
S G
SG
D000818:Animals; D001491:Basophils / Q000378:metabolism*; D001665:Binding Sites; D001667:Binding, Competitive; D002460:Cell Line; D005434:Flow Cytometry; D016650:Fluorescein-5-isothiocyanate / Q000378:metabolism; D006358:Hot Temperature; D006801:Humans; D007073:Immunoglobulin E / Q000378:metabolism; D015471:Leukemia, Basophilic, Acute / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D051381:Rats; D017455:Receptors, IgE / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D017455:Receptors, IgE; D007073:Immunoglobulin E; D016650:Fluorescein-5-isothiocyanate