IgE-producing hybridomas established after B-cell culture in the CD40 system

While total IgE synthesis can be easily induced in human PBL or B cells by different stimuli, no systems are known for the induction of allergen-specific IgE in vitro. In this study we investigated whether a specific Ig response could be induced using the CD40 culture system with the final intention to generate B-cell hybridomas secreting IgE of defined specificity. B cells derived from immunized donors normally give rise to many specific hybridomas after cell fusion. However, if cultured in the CD40 system and then immortalized and screened for anti-tetanus specificity, no tetanus-specific clones were found but a large number of IgE-secreting hybridomas had been generated. Also allergen-specific B cells could not be expanded in the CD40 system but long-term cultures yielded again B cells that were efficiently immortalized by cell fusion resulting in stable IgE-secreting hybridomas but of undefined specificity. One of these IgE-producing clones was further characterized and had an IgE production rate of 4.5 micrograms/10(6) cells/24 h. This paper provides two findings. (1) Our cell lines represent a valuable new source of human IgE. (2) Most importantly, our data indicate that the CD40 system is not suitable to expand specific B cells, suggesting that other systems have to be developed for the induction of a significant antigen-specific Ig response.