Virus-induced maturation and activation of autoreactive memory B cells

We have examined B cell populations that participate in distinct phases of the immune response to the influenza virus A/PR/8/34 hemagglutinin (HA) for their susceptibility to negative selection in mice that express the HA as a neo-self-antigen (HA104 mice). We demonstrated previously chat specificit y for the neo-self-HA causes a population of immunoglobulin G antibody-secr eting cells, which dominate the primary response to virus immunization in B ALB/c mice, to be negatively selected in HA104 mice. We find here that in c ontrast to these primary response B cells, HA-specific memory response B ce lls developed equivalently in HA104 and nontransgenic (BALB/c) mice. Indeed , there was no indication that HA-specific B cells were negatively selected during memory formation in influenza virus-immunized HA104 mice, even thou gh the neo-self-HA can be recognized by memory B cells. Furthermore, HA-spe cific autoantibodies were induced in the absence of virus immunization by m ating HA104 mice with mice transgenic for a CD4(+) HA-specific T cell recep tor. These findings indicate that specificity for a self-antigen does not p revent the maturation of autoreactive B cells in the germinal center pathwa y. Rather, the availability of CD4(+) T cell help may play a crucial role i n regulating autoantibody responses to the HA in HA104 mice.