Use of secondarily revised VH genes in IgE antibodies produced in mice infected with the nematode Nippostrongylus brasiliensis

Although a high level of IgE is produced after primary infection with Nippo strongylus brasiliensis (Nb), most of the IgE antibodies (Abs) are not spec ific to the worm. Analyses with Western blotting and enzyme-linked immunoso rbent assay (ELISA) revealed that the IgE Abs from Nb-infected BALB/c mice did not show reactivity with Nb-derived excretory-secretory proteins (NES) and antigens present in the cell-free extracts of the worm. Monoclonal IEE Abs obtained from the Nb-infected mice were not reactive with these Nb anti gen either. To characterize Nb-induced IgE response, we used (QM x C57BL/6) F1 (QBF1) mice that bear the knock-in 17.2.25 VHDJH segment (VHT) encoding a VH region specific to 4-hydroxy-3-nitrophenylacetyl hapten, and express V HT-encoded antigen receptors on 80-85% of their B cells. Consistent with th e frequency of VHT-positive B cells, more than 80% of IgE Abs induced in QB F1 B cells that were cultured with LPS plus IL-4 were found to bear VHT-enc oded H chains. In contrast, when QBF1 mice were infected with Nb, less than 10% of Nb-induced IgE Abs were found to use VHT. The QBF1-derived IgE did not react with Nb antigens either. Taken together, data suggest that Nb-ind uced IgE response in mice is not merely the result of polyclonal activation of B cells, but may involve a mechanism that revises Ig genes secondarily. (C) 2001 Elsevier Science B.V. All rights reserved.