Expression of prolactin receptor in B cells. PRL receptor expression (MFI) was measured using flow cytometry from eight mice per strain. BM cells were labelled with anti-B220, anti-CD43, anti-CD23, anti-IgM, and goat anti-PRL receptor antibodies; the isotype control was labelled with anti-B220, anti-CD43, anti-CD23, anti-IgM, and goat unrelated antibodies. (a) Pro-B, pre-B and immature from C57BL/6 mice; (b) histograms of PRL receptor expression in B cells from BM; (c) pro-B, pre-B, and immature from MRL mice; (d) pro-B, pre-B, and immature from MRL/lpr mice. The asterisks denote statistical significance with the P value shown. The MFI values expressed in the graphs correspond to the MFI values minus the isotype control.