Issues

Cover picture: Memory B cells can form germinal centers in response to self-antigen. Transgenic mice expressing the influenza virus hemagglutinin (HA) were injected with a mixture of memory B cells derived from influenza virus­ primed BALB/c mice and HA-specific CD4-positive T cells. 5 d later, splenic sections were taken and stained to identify IgD-positive (blue) and peanut agglutinin­positive (red) cells. Well organized germinal centers were present in HA-transgenic mice (left panel) but not in nontransgenic littermates (right panel). Even though the HA is recognized by HA-specific memory B cells and can induce these cells to form germinal centers, HA-transgenic and nontransgenic mice were found to generate equivalent memory B cell responses after virus immunization. These studies indicate that specificity for self-antigen does not prevent the maturation of autoreactive B cells in the germinal center pathway, arguing against the existence of a second window of tolerance induction during memory B cell formation. See related article in this issue by Reed et al., pp. 1763-1774.