The induction of murine B cell Ia by IgE-antigen complexes is dependent on protein synthesis and preceded by class II mRNA accumulation

Complexes of murine monoclonal anti-DNP IgE and DNP-OVA interact with murine B cells` to stimulate expression of cell surface Ia antigens. Enhanced membrane expression of class II MHC antigens was accompanied by a threefold increase of I-A and I-E transcripts, as measured by Northern blot. Peak accumulation of Ia mRNA were detected after 6 hr of incubation with IgE-antigen complexes and returned to control levels after 12 hr of incubation. Hence, induction of Ia mRNA by IgE-antigen complexes was compatible with cell surface Ia expression, both quantitatively and with regard to the time frame. The Ia-inductive effects of both IL-4 and IgE-antigen complexes were inhibited by cycloheximide and actinomycin-D. However, whereas actinomycin-D and cycloheximide blocked IL-4 induction of Fcε{lunate}RII expression, inhibition of transcription or protein synthesis did not abrogate the increased expression of Fcε{lunate}R associated with IgE-antigen complexes. These results suggest that the IgE-antigen-induction of B cell Ia expression follows from activation of transcription and de novo synthesis of Ia antigens.