In a typical primary immune response, the IgM B cell receptor (BCR) is changed to an IgG BCR by isotype switching. The B cells that have switched to IgG give rise to more bone marrow long-lived plasma cells (LLPCs) than the IgM B cells do. How such BCR isotype-driven bias occurs remains unclear. Here, we showed that IgG1 germinal center (GC) B cells presented higher levels of antigen to Tfh cells, making the resultant plasma cells more proliferative than the IgM cells, and that BCR signaling through IgM conferred more Bim-dependent apoptosis on their plasma cells, together dominating the numbers of IgG1 over IgM plasma cells in the secondary lymphoid tissues. In addition, IgG1 plasma cells were more prone to migrate to bone marrow than the IgM cells. Hence, our findings suggest that differential activities in antigen presentation and signaling through IgG1 BCRs contribute to enrichment of IgG1 plasma cells in the bone marrow LLPC compartment.

Contact

Tomohiro Kurosaki

kurosakiifrec.osaka-u.ac.jp