TLR9-signaling is required for turning retinoic acid into a potent stimulator of RP105 (CD180)-mediated proliferation and IgG synthesis in human memory B cells

- RA inhibits RP105-mediated proliferation and differentiation of human B cells.
- TLR9-signaling changes RA into an activator of RP105-mediated B cell functions.
- IL-10 is required for RA to stimulate anti-RP105/CpG-mediated B cell functions.