IGE-PRODUCING HYBRIDOMAS ESTABLISHED AFTER B-CELL CULTURE IN THE CD40SYSTEM

While total IgE synthesis can be easily induced in human PBL or B cell s by different stimuli, no systems are known for the induction of alle rgen-specific IgE in vitro. In this study we investigated whether a sp ecific Ig response could be induced using the CD40 culture system with the final intention to generate B-cell hybridomas secreting IgE of de fined specificity. B cells derived from immunized donors normally give rise to many specific hybridomas after cell fusion. However, if cultu red in the CD40 system and then immortalized and screened for anti-tet anus specificity, no tetanus-specific clones were found but a large nu mber of IgE-secreting hybridomas had been generated. Also allergen-spe cific B cells could not be expanded in the CD40 system but long-term c ultures yielded again B cells that were efficiently immortalized by ce ll fusion resulting in stable IgE-secreting hybridomas but of undefine d specificity. One of these IgE-producing clones was further character ized and had an IgE production rate of 4.5 mu g/10(6)celIs/24 h. This paper provides two findings. (1) Our cell lines represent a valuable n ew source of human IgE. (2) Most importantly, our data indicate that t he CD40 system is not suitable to expand specific B cells, suggesting that other systems have to be developed for the induction of a signifi cant antigen-specific Ig response.