IgE memory B cells identified by the polymerase chain reaction

The existence of memory B cells for IgE was investigated using spleen cells harvested from mice primed and boosted with dinitrophenylated keyhole limpet hemocyanin. Using the polymerase chain reaction, it was found that mRNA for IgE was already demonstrable in spleen cells taken 1 day after boost. Spleen cells taken from mice 1 day after boost and cultured in vitro without the addition of antigen also produced anti-dinitrophenylated (DNP) IgE antibody. In contrast, mRNA for IgE in spleen cells from mice primed 4 weeks previously, but not boosted, was not demonstrable. Anti-DNP IgE was not produced in cultures of spleen cells from mice primed but not boosted. As mRNA for IgE was demonstrable already 1 day after boost we concluded that mice produce memory B cells not only for IgM, but also for IgE specific for the immunizing antigen.