Estrogen increases the number of plasma cells and enhances their autoantibody production in nonautoimmune C57BL/6 mice.

The immunological consequences of chronic estrogen exposure in normal individuals are not known, particularly in relation to B cells. In this study, by employing ELIspot, image cytometry, flow cytometry, cytology, and ELISA, we show that long-term exposure of normal mice to estrogen activates B cells to produce higher numbers of not only immunoglobulin-producing cells, but also autoantibody-producing cells. Estrogen promoted a decrease in B220(+) splenic lymphocytes, but resulted in a 10-fold increase in plasma cells. Further, the output of immunoglobulins including autoantibodies from individual plasma cells from estrogen-exposed mice was markedly increased, suggesting B cell hyperactivity. Importantly, our findings show that treatment of normal mice, solely with estrogen, can override B cell tolerance and promote autoreactive B cells in normal individuals.