Serum Levels of Interleukin 4, Interleukin 6 and Interferon-Gamma following in vivo Isotype-Specific Activation of IgE Synthesis in Humans

It is now generally accepted that interleukin 4 (IL4), interleukin 6 (IL6) and interferon-gamma (IFN gamma) play main roles in the regulation of human IgE synthesis. This concept is based mainly on in vitro data. To obtain corresponding in vivo data, we determined IL4, IL6 and IFN gamma by immunoassays in sera collected from 4 atopic patients following a clinical trial of selective IgE apheresis (plasmaimmunoadsorption). This treatment removes several milligrams of IgE from patient's blood and is suggested to induce strong and isotype-specific activation of the IgE system. Serum IgE levels restored rapidly within 3-5 days after IgE apheresis. However, very low and constant levels of IL4 (from less than 50 to 130 pg/ml) and IL6 (from less than 300 to 920 pg/ml) were detected in the sera of the treated patients. Serum IFN gamma was absent before treatment (concentrations less than 0.5 U/ml) and increased to low but detectable levels (0.90 and 8.05 U/ml) on the day following the last IgE apheresis in 2 of 4 patients. In our opinion, the data presented argue against in vivo participation of IL4 and IL6 in the activation of the human IgE system, at least in atopic patients under constant allergen exposure.