The effect of platelet-activating factor on IgE binding to, and IgE-dependent biological properties of, human eosinophils.
This study investigated the effect of platelet-activating factor (PAF), leukotriene B4 (LTB4) histamine and formyl-methionyl-leucyl-phenylalanine (FMLP) on immunoglobulin E (IgE) binding and IgE-dependent cytotoxicity of human normal density eosinophils. The binding of a native myeloma IgE to normal human eosinophils was measured by flow cytometry using a fluorescein-conjugated polyclonal anti-IgE antibody. Preincubation with PAF (optimal at 10(-7)M), but not lyso-PAF or FMLP, gave dose-dependent increases in IgE binding. PAF and LTB4 gave significant increases in IgE binding after 5 min preincubation (P less than 0.05); the effect was further enhanced at 30 min (P less than 0.01). This was further confirmed using the rosette assay where PAF and LTB4, but not lyso-PAF or FMLP, gave dose- and time-dependent increases in IgE eosinophil rosettes. Eosinophil cytotoxicity for schistosomula of Schistosoma mansoni, incubated with immune serum, was also significantly enhanced (P less than 0.01) by PAF in a dose-dependent fashion (optimal at 10(-8) M). Schistosomula coated with FPLC-purified IgE fractions were susceptible to killing by normal density eosinophils, and this was enhanced with PAF (10(-8)M), LTB4 (10(-7)M) and histamine (10(-5)M) but not with FMLP (10(-7)M) or lyso-PAF. IgE-dependent cytotoxicity was confirmed by the removal of contaminating IgG from IgE-rich fractions, and by the abolishment of IgE-dependent cytotoxicity after IgE adsorption. These results suggest that PAF (and to a lesser extent LTB4 and histamine) increase IgE binding, IgE-dependent adherence and cytotoxicity of normal human eosinophils. Although IgE receptors have not been identified, the data support current concepts that certain biological properties of eosinophils may be IgE associated.
Moqbel
R
R
Department of Allergy and Clinical Immunology, National Heart & Lung Institute, Brompton Hospital, London, U.K.
Walsh
G M
GM
Nagakura
T
T
MacDonald
A J
AJ
Wardlaw
A J
AJ
Iikura
Y
Y
Kay
A B
AB
D002478:Cells, Cultured; D002630:Chemotactic Factors / Q000494:pharmacology; D003602:Cytotoxicity, Immunologic / Q000276:immunology; D004306:Dose-Response Relationship, Immunologic; D004804:Eosinophils / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology / Q000378:metabolism*; D010972:Platelet Activating Factor / Q000494:pharmacology*; D012397:Rosette Formation
D002630:Chemotactic Factors; D010972:Platelet Activating Factor; D007073:Immunoglobulin E