A normally rare population of B-cell precursors accumulates in estrogen-treated mice.

CD45R⁺CD43⁻ sIgM⁻ cells from control or E2-treated BALB/c mice were sorted, fixed and made permeable as described in the “Materials and Methods.” The sorted cells were then incubated with an antimouse IgM to detect cμ expression (Panel A). In this example, 40% of the CD43⁻cells in hormone-treated mice were cμ⁻compared with 7% in the control animals. Panel B shows a typical RT-PCR analysis of tdt and bcl-2 gene expression in CD45R⁺CD43⁻ sIgM⁻ cells sorted from control (bone marrow pooled from 3 mice) or E2-treated animals (bone marrow pooled from 5 mice).