Figure 6.

The Y500F mutation augments isotype switching. (A) Production of IgG1 and IgE by cultured splenocytes treated with an anti-CD40 mAb + IL-4. Levels of IgG1 and IgE antibodies present in IgG1 and IgE in supernatants of unstimulated cells were <8 ng/ml, respectively. Results are means ± SE antibody (4 mice/group). Similar results were found in three separate experiments. (B) Molecular events in isotype switching. RT-PCR analysis of μ, γ1, and ɛ germline (GLT) and γ1 and ɛ postswitch transcripts (Iμ→γ1 and Iμ→ɛ, respectively) in splenic B cells treated for 48 h with IL-4, anti-CD40 mAB, or both. Results are representative of four pairs of WT and mutant mice from two independent experiments. (C) Sμ-Sγ1 and Sμ-Sɛ deletional switch recombination measured by DC-PCR at day 6 after treatment with anti-CD40 mAb + IL-4. PCR was performed using 5 ng (lanes 1 and 3) or 20 ng (lanes 2 and 4) of template DNA.