Figure 4.

Ongoing isotype switching in normal and μMT BM cultures and BM in vivo. (A) BM cells from normal and μMT mouse were cultured in vitro for 5 d in the presence of IL-7. mRNA samples from the cultured cells were subjected to RT-PCR amplification for IgG1 germline and postswitch transcript as well as for AID expression. Normal splenic cells either unstimulated or stimulated with LPS were used as negative and positive controls, respectively. The results shown are representative of three to five different experiments and a total of five to eight mice in each group. (B) B220⁺ cells were sorted directly from BM or spleen of the indicated mice and mRNA samples were subjected to RT-PCR amplification for AID and IgG2b germline and postswitch transcripts. Representative blots from three mice in each group are shown.