IL-4-dependent IgE class switching in an anti-trinitrophenyl B-cell hybridoma after engagement of antigen receptors

A B-cell hybridoma, TP67.21 that expresses surface anti-trinitrophenyl (TNP ) IgM but does not secrete the antibody spontaneously has been reported to differentiate into anti-TNP IgM-secreting cells in response to lipopolysacc haride or engagement of surface IgM. Here, we report isolation and characte rization of a subclone, TP67.21E (TP.E) that undergoes isotype switching to IgE in an interleukin (IL)-4-dependent manner. TP.E cells secreted anti-TN P IgE depending on exogenous IL-4 when they were cultured with an anti-IgM antibody for 6-8 days. 8-Mercaptoguanosine, which has been shown to enhance IgE class switching in murine splenic B-cells further augmented the IgE re sponse in TP.E cells. Immunofluorescence microscopy revealed that approxima tely 1.2% of the cultured cells became positive for intracellular IgE after the stimulation culture. The germline epsilon transcripts were expressed t ransiently on days 2-4 of the culture, while expression of the productive e psilon transcripts was induced 5 days after the start of the culture, thus suggesting that IEE class switching occurred in TP.E cells under these cond itions. (C) 1999 Elsevier Science B.V. All rights reserved.