Hormonal regulation of B cell development:: 17β-estradiol impairs negative selection of high-affinity DNA-reactive B cells at more than one developmental checkpoint

There are increasing data suggesting that sex hormones, such as estrogen, have immunomodulatory effects and play a role in disease progression and pathogenesis in patients with the autoimmune disorder systemic lupus erythematosus. We have shown previously that treatment with 17 beta-estradiol (E2) induces a lupus phenotype in BALB/c mice that express a transgene-encoded H chain of an anti-DNA Ab. Because E2 treatment interferes with normal tolerance of naive DNA-reactive B cells, we elected to study the effects of hormonal modulation on the regulation of autoreactive B cells at early developmental checkpoints. Single-cell PCR was performed to study the repertoire of DNA-reactive B cell subsets. High-affinity DNA-reactive B cells were rescued at both the immature and transitional B cell stage in E2-treated mice. Interestingly, although low-affinity DNA-reactive B cells survive negative selection in control mice, the frequency of these cells was significantly reduced in the mature pool of E2-treated mice, suggesting that the high-affinity DNA-reactive cells that mature to immunocompetence out-compete the low-affinity population for survival as mature B cells. These data provide evidence that an elevation in serum levels of E2 facilitates the maturation of a pathogenic naive autoreactive B cell repertoire and hampers the maturation of a potentially protective autoreactive B cell repertoire. Furthermore, these data show that both positive and negative selection occur within the transitional B cell stage.