Unique requirements for reactivation of virus-specific memory B lymphocytes
Weisel, FJ and Appelt, UK and Schneider, AM and Horlitz, JU and van Rooijen, N and Korner, H and Mach, M and Winkler, TH, Unique requirements for reactivation of virus-specific memory B lymphocytes, Journal of Immunology, 185, (7) pp. 4011-4021. ISSN 0022-1767 (2010) [Refereed Article]
Memory B cells (MBCs) are rapidly activated upon Ag re-exposure in vivo, but the precise requirements for this process are still
elusive. To address these requirements, T cell-independent reactivation of MBCs against virus-like particles was analyzed. As few as
25 MBCs are sufficient for a measurable Ab response after adoptive transfer.We found that MBCs were reactivated upon antigenic
challenge to normal levels after depletion of macrophages, CD11c+ dendritic cells, and matured follicular dendritic cells. Furthermore,
MBC responses were possible in TNF/lymphotoxin a double-deficient mice after partial normalization of lymphoid
architecture by means of long-term reconstitution with wild-type bone marrow. Activation did not occur when chimeric mice,
which still lack all lymph nodes and Peyer’s patches, were splenectomized prior to MBC transfer. Together with our finding that
MBC responses are weak when Ag was administered within minutes after adoptive MBC transfer, these results strongly suggest
that MBCs have to occupy specific niches within secondary lymphoid tissue to become fully Ag-responsive. We provide clear
evidence that MBCs are not preferentially resident within the splenic marginal zones and show that impaired homing to lymphoid
follicles resulted in significantly diminished activation, suggesting that reactivation of MBCs occurred inside lymphoid follicles.
Furthermore, comparison of virus-specific MBC T cell-independent reactivation versus primary T cell-independent type II B cell
activation revealed unique requirements of MBC activation.