Figure 3.

A model for FcμR-mediated immunity and tolerance. FcμR promotes the survival and activation of mature B cells by interacting with the BCR and potentiating foreign Ag-triggered BCR signaling (left). By analogy, FcμR might also promote self Ag-triggered BCR signaling in immature B cells and contribute to the deletion/anergy of autoreactive immature B cells in the BM (right). Ag-specific IgM/IgG are illustrated in the scheme shown in Figures 1, 2 and 4 to suggest that those reactions occur during an immune response. In contrast, IgM shown in this scheme is not Ag-specific to implicate that these reactions can occur in the absence of Ag-specific IgM.