TLR9 and Autoimmunity: In conclusion, the findings described here involving TLR9 signaling in FO B cells modify our current conceptual view of the action of this receptor; it opens a new perspective on the potential role of TLR9 in autoimmunity and have implications for the balance between proliferation and terminal differentiation of B lymphocytes, adding a new layer of complexity in the regulation of clonal sizes of B cell repertoires engaged in humoral immune responses.